Mike Perry commited on 2008-08-05 06:47:05
Zeige 5 geänderte Dateien mit 0 Einfügungen und 3594 Löschungen.
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-<?xml version="1.0" encoding="ISO-8859-1"?> |
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-<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" |
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- "file:///usr/share/sgml/docbook/xml-dtd-4.4-1.0-30.1/docbookx.dtd"> |
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- |
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-<article id="design"> |
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- <articleinfo> |
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- <title>Torbutton Design Documentation</title> |
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- <author> |
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- <firstname>Mike</firstname><surname>Perry</surname> |
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- <affiliation> |
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- <address><email>mikeperry.fscked/org</email></address> |
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- </affiliation> |
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- </author> |
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- <pubdate>July 4 2008</pubdate> |
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- </articleinfo> |
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- |
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-<sect1> |
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- <title>Introduction</title> |
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- <para> |
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- |
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-This document describes the goals, operation, and testing procedures of the |
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-Torbutton Firefox extension. It is current as of Torbutton 1.2.0rc5. |
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- |
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- </para> |
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- <sect2 id="adversary"> |
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- <title>Adversary Model</title> |
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- <para> |
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- |
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-A Tor web browser adversary has a number of goals, capabilities, and attack |
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-types that can be used to guide us towards a set of requirements for the |
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-Torbutton extension. Let's start with the goals. |
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- |
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- </para> |
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- <sect3> |
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- <title>Adversary Goals</title> |
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- <orderedlist> |
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-<!-- These aren't really commands.. But it's the closest I could find in an |
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-acceptable style.. Don't really want to make my own stylesheet --> |
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- <listitem><command>Bypassing proxy settings</command> |
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- <para>The adversary's primary goal is direct compromise and bypass of |
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-Tor, causing the user to directly connect to an IP of the adversary's |
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-choosing.</para> |
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- </listitem> |
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- <listitem><command>Correlation of Tor vs Non-Tor Activity</command> |
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- <para>If direct proxy bypass is not possible, the adversary will likely |
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-happily settle for the ability to correlate something a user did via Tor with |
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-their non-Tor activity. This can be done with cookies, cache identifiers, |
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-javascript events, and even CSS. Sometimes the fact that a user uses Tor may |
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-be enough for some authorities.</para> |
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- </listitem> |
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- <listitem><command>History disclosure</command> |
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- <para> |
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-The adversary may also be interested in history disclosure: the ability to |
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-query a user's history to see if they have issued certain censored search |
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-queries, or visited censored sites. |
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- </para> |
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- </listitem> |
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- <listitem><command>Location information</command> |
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- <para> |
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- |
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-Location information such as timezone and locality can be useful for the |
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-adversary to determine if a user is in fact originating from one of the |
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-regions they are attempting to control, or to zero-in on the geographical |
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-location of a particular dissident or whistleblower. |
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- |
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- </para> |
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- </listitem> |
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- <listitem><command>Miscellaneous anonymity set reduction</command> |
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- <para> |
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- |
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-Anonymity set reduction is also useful in attempting to zero in on a |
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-particular individual. If the dissident or whistleblower is using a rare build |
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-of Firefox for an obscure operating system, this can be very useful |
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-information for tracking them down, or at least <link |
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-linkend="fingerprinting">tracking their activities</link>. |
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- |
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- </para> |
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- </listitem> |
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- <listitem><command>History records and other on-disk |
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-information</command> |
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- <para> |
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-In some cases, the adversary may opt for a heavy-handed approach, such as |
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-seizing the computers of all Tor users in an area (especially after narrowing |
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-the field by the above two pieces of information). History records and cache |
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-data are the primary goals here. |
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- </para> |
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- </listitem> |
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- </orderedlist> |
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- </sect3> |
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- |
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- <sect3> |
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- <title>Adversary Capabilities - Positioning</title> |
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- <para> |
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-The adversary can position themselves at a number of different locations in |
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-order to execute their attacks. |
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- </para> |
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- <orderedlist> |
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- <listitem><command>Exit Node or Upstream Router</command> |
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- <para> |
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-The adversary can run exit nodes, or alternatively, they may control routers |
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-upstream of exit nodes. Both of these scenarios have been observed in the |
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-wild. |
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- </para> |
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- </listitem> |
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- <listitem><command>Adservers and/or Malicious Websites</command> |
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- <para> |
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-The adversary can also run websites, or more likely, they can contract out |
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-ad space from a number of different adservers and inject content that way. For |
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-some users, the adversary may be the adservers themselves. It is not |
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-inconceivable that adservers may try to subvert or reduce a user's anonymity |
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-through Tor for marketing purposes. |
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- </para> |
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- </listitem> |
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- <listitem><command>Local Network/ISP/Upstream Router</command> |
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- <para> |
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-The adversary can also inject malicious content at the user's upstream router |
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-when they have Tor disabled, in an attempt to correlate their Tor and Non-Tor |
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-activity. |
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- </para> |
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- </listitem> |
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- <listitem><command>Physical Access</command> |
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- <para> |
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-Some users face adversaries with intermittent or constant physical access. |
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-Users in Internet cafes, for example, face such a threat. In addition, in |
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-countries where simply using tools like Tor is illegal, users may face |
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-confiscation of their computer equipment for excessive Tor usage or just |
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-general suspicion. |
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- </para> |
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- </listitem> |
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- </orderedlist> |
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- </sect3> |
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- |
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- <sect3> |
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- <title>Adversary Capabilities - Attacks</title> |
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- <para> |
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-The adversary can perform the following attacks from a number of different |
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-positions to accomplish various aspects of their goals. |
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- </para> |
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- <orderedlist> |
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- <listitem><command>Inserting Javascript</command> |
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- <para> |
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-Javascript allows the adversary the opportunity to accomplish a number of |
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-their goals. If not properly disabled, Javascript event handlers and timers |
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-can cause the browser to perform network activity after Tor has been disabled, |
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-thus allowing the adversary to correlate Tor and Non-Tor activity. Javascript |
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-also allows the adversary to execute <ulink |
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-url="http://gemal.dk/browserspy/css.html">history disclosure attacks</ulink>: |
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-to query the history via the different attributes of 'visited' links. Finally, |
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-Javascript can be used to query the user's timezone via the |
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-<function>Date()</function> object, and to reduce the anonymity set by querying |
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-the <function>navigator</function> object for operating system, CPU, and user |
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-agent information. |
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- </para> |
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- </listitem> |
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- |
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- <listitem><command>Inserting Plugins</command> |
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- <para> |
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- |
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-Plugins are abysmal at obeying the proxy settings of the browser. Every plugin |
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-capable of performing network activity that the author has |
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-investigated is also capable of performing network activity independent of |
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-browser proxy settings - and often independent of its own proxy settings. |
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-In addition, plugins can be used to store unique identifiers that are more |
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-difficult to clear than standard cookies. |
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-<ulink url="http://epic.org/privacy/cookies/flash.html">Flash-based |
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-cookies</ulink> fall into this category, but there are likely numerous other |
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-examples. |
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- |
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- </para> |
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- </listitem> |
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- <listitem><command>Inserting CSS</command> |
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- <para> |
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- |
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-CSS can also be used to correlate Tor and Non-Tor activity, via the usage of |
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-<ulink url="http://www.tjkdesign.com/articles/css%20pop%20ups/">CSS |
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-popups</ulink> - essentially CSS-based event handlers that fetch content via |
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-CSS's onmouseover attribute. If these popups are allowed to perform network |
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-activity in a different Tor state than they were loaded in, they can easily |
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-correlate Tor and Non-Tor activity and reveal a user's IP address. In |
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-addition, CSS can also be used without Javascript to perform <ulink |
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-url="http://ha.ckers.org/weird/CSS-history.cgi">CSS-only history disclosure |
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-attacks</ulink>. |
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- </para> |
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- </listitem> |
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- <listitem><command>Read and insert cookies</command> |
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- <para> |
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- |
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-An adversary in a position to perform MITM content alteration can inject |
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-document content elements to both read and inject cookies for |
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-arbitrary domains. In fact, many "SSL secured" websites are vulnerable to this |
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-sort of <ulink url="http://seclists.org/bugtraq/2007/Aug/0070.html">active |
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-sidejacking</ulink>. |
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- |
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- </para> |
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- </listitem> |
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- <listitem><command>Create arbitrary cached content</command> |
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- <para> |
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- |
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-Likewise, the browser cache can also be used to <ulink |
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-url="http://crypto.stanford.edu/sameorigin/safecachetest.html">store unique |
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-identifiers</ulink>. Since by default the cache has no same-origin policy, |
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-these identifiers can be read by any domain, making them an ideal target for |
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-adserver-class adversaries. |
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- |
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- </para> |
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- </listitem> |
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- <listitem id="fingerprinting"><command>Fingerprint users based on browser |
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-attributes</command> |
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-<para> |
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- |
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-There is an absurd amount of information available to websites via attributes |
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-of the browser. This information can be used to reduce anonymity set, or even |
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-<ulink url="http://0x000000.com/index.php?i=520&bin=1000001000">uniquely |
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-fingerprint individual users</ulink>. </para> |
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-<para> |
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-For illustration, let's perform a |
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-back-of-the-envelope calculation on the number of anonymity sets for just the |
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-resolution information available in the <ulink |
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-url="http://developer.mozilla.org/en/docs/DOM:window">window</ulink> and |
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-<ulink |
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-url="http://developer.mozilla.org/en/docs/DOM:window.screen">window.screen</ulink> |
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-objects. Browser window resolution information provides something like |
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-(1280-640)*(1024-480)=348160 different anonymity sets. Desktop resolution |
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-information contributes about another factor of 5 (for about 5 resolutions in |
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-typical use). In addition, the dimensions and position of the desktop taskbar |
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-are available, which can reveal hints on OS information. This boosts the count |
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-by a factor of 5 (for each of the major desktop taskbars - Windows, OSX, KDE |
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-and Gnome, and None). Subtracting the browser content window |
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-size from the browser outer window size provide yet more information. |
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-Firefox toolbar presence gives about a factor of 8 (3 toolbars on/off give |
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-2<superscript>3</superscript>=8). Interface effects such as titlebar fontsize |
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-and window manager settings gives a factor of about 9 (say 3 common font sizes |
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-for the titlebar and 3 common sizes for browser GUI element fonts). |
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-Multiply this all out, and you have (1280-640)*(1024-480)*5*5*8*9 ~= |
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-2<superscript>29</superscript>, or a 29 bit identifier based on resolution |
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-information alone. </para> |
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- |
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-<para> |
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- |
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-Of course, this space is non-uniform and prone to incremental changes. |
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-However, if a bit vector space consisting of the above extracted attributes |
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-were used instead of the hash approach from <ulink |
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-url="http://0x000000.com/index.php?i=520&bin=1000001000">The Hacker |
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-Webzine article above</ulink>, minor changes in browser window resolution will |
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-no longer generate totally new identifiers. |
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- |
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-</para> |
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-<para> |
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- |
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-To add insult to injury, <ulink |
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-url="http://pseudo-flaw.net/content/tor/torbutton/">chrome URL disclosure |
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-attacks</ulink> mean that each and every extension on <ulink |
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-url="https://addons.mozilla.org">addons.mozilla.org</ulink> adds another bit |
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-to that 2<superscript>29</superscript>. With hundreds of popular extensions |
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-and thousands of extensions total, it is easy to see that this sort of |
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-information is an impressively powerful identifier if used properly by a |
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-competent and determined adversary such as an ad network. Again, a |
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-nearest-neighbor bit vector space approach here would also gracefully handle |
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-incremental changes to installed extensions. |
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- |
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-</para> |
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- |
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- </listitem> |
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- <listitem><command>Remotely or locally exploit browser and/or |
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-OS</command> |
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- <para> |
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-Last, but definitely not least, the adversary can exploit either general |
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-browser vulnerabilities, plugin vulnerabilities, or OS vulnerabilities to |
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-install malware and surveillance software. An adversary with physical access |
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-can perform similar actions. Regrettably, this last attack capability is |
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-outside of Torbutton's ability to defend against, but it is worth mentioning |
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-for completeness. |
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- </para> |
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- </listitem> |
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- </orderedlist> |
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- </sect3> |
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- |
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- </sect2> |
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- |
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- <sect2 id="requirements"> |
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- <title>Torbutton Requirements</title> |
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-<note> |
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- |
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-Since many settings satisfy multiple requirements, this design document is |
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-organized primarily by Torbutton components and settings. However, if you are |
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-the type that would rather read the document from the requirements |
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-perspective, it is in fact possible to search for each of the following |
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-requirement phrases in the text to find the relevant features that help meet |
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-that requirement. |
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- |
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-</note> |
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- <para> |
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- |
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-From the above Adversary Model, a number of requirements become clear. |
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- |
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- </para> |
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- |
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-<orderedlist> |
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-<!-- These aren't really commands.. But it's the closest I could find in an |
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-acceptable style.. Don't really want to make my own stylesheet --> |
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- <listitem id="proxy"><command>Proxy Obedience</command> |
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- <para>The browser |
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-MUST NOT bypass Tor proxy settings for any content.</para></listitem> |
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- <listitem id="isolation"><command>Network Isolation</command> |
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- <para>Pages MUST NOT perform any network activity in a Tor state different |
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- from the state they were originally loaded in.</para></listitem> |
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- <listitem id="state"><command>State Separation</command> |
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- <para>Browser state (cookies, cache, history, 'DOM storage'), accumulated in |
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- one Tor state MUST NOT be accessible via the network in |
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- another Tor state.</para></listitem> |
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- <listitem id="undiscoverability"><command>Tor Undiscoverability</command><para>With |
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-the advent of bridge support in Tor 0.2.0.x, there are now a class of Tor |
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-users whose network fingerprint does not obviously betray the fact that they |
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-are using Tor. This should extend to the browser as well - Torbutton MUST NOT |
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-reveal its presence while Tor is disabled.</para></listitem> |
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- <listitem id="disk"><command>Disk Avoidance</command><para>The browser SHOULD NOT write any Tor-related state to disk, or store it |
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- in memory beyond the duration of one Tor toggle.</para></listitem> |
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- <listitem id="location"><command>Location Neutrality</command><para>The browser SHOULD NOT leak location-specific information, such as |
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- timezone or locale via Tor.</para></listitem> |
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- <listitem id="setpreservation"><command>Anonymity Set |
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-Preservation</command><para>The browser SHOULD NOT leak any other anonymity set reducing information |
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- (such as user agent, extension presence, and resolution information) |
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-automatically via Tor. The assessment of the attacks above should make it clear |
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-that anonymity set reduction is a very powerful method of tracking and |
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-eventually identifying anonymous users. |
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-</para></listitem> |
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- <listitem id="updates"><command>Update Safety</command><para>The browser |
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-SHOULD NOT perform unauthenticated updates or upgrades via Tor.</para></listitem> |
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- <listitem id="interoperate"><command>Interoperability</command><para>Torbutton SHOULD interoperate with third-party proxy switchers that |
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- enable the user to switch between a number of different proxies. It MUST |
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- provide full Tor protection in the event a third-party proxy switcher has |
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- enabled the Tor proxy settings.</para></listitem> |
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-</orderedlist> |
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- </sect2> |
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- <sect2 id="layout"> |
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- <title>Extension Layout</title> |
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- |
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-<para>Firefox extensions consist of two main categories of code: 'Components' and |
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-'Chrome'. Components are a fancy name for classes that implement a given |
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-interface or interfaces. In Firefox, components <ulink |
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-url="http://www.xulplanet.com/references/xpcomref/creatingcomps.html">can be |
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-written</ulink> in C++, |
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-Javascript, or a mixture of both. Components have two identifiers: their |
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-'<ulink |
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-url="http://www.mozilla.org/projects/xpcom/book/cxc/html/quicktour2.html#1005005">Contract |
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-ID</ulink>' (a human readable path-like string), and their '<ulink |
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-url="http://www.mozilla.org/projects/xpcom/book/cxc/html/quicktour2.html#1005329">Class |
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-ID</ulink>' (a GUID hex-string). In addition, the interfaces they implement each have a hex |
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-'Interface ID'. It is possible to 'hook' system components - to reimplement |
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-their interface members with your own wrappers - but only if the rest of the |
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-browser refers to the component by its Contract ID. If the browser refers to |
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-the component by Class ID, it bypasses your hooks in that use case. |
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-Technically, it may be possible to hook Class IDs by unregistering the |
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-original component, and then re-registering your own, but this relies on |
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-obsolete and deprecated interfaces and has proved to be less than |
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-stable.</para> |
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- |
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-<para>'Chrome' is a combination of XML and Javascript used to describe a window. |
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-Extensions are allowed to create 'overlays' that are 'bound' to existing XML |
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-window definitions, or they can create their own windows. The DTD for this XML |
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-is called <ulink |
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-url="http://developer.mozilla.org/en/docs/XUL_Reference">XUL</ulink>.</para> |
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- </sect2> |
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-</sect1> |
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-<sect1> |
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- <title>Components</title> |
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- <para> |
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- |
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-Torbutton installs components for two purposes: hooking existing components to |
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-reimplement their interfaces; and creating new components that provide |
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-services to other pieces of the extension. |
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- |
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- </para> |
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- |
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- <sect2> |
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- <title>Hooked Components</title> |
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- |
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-<para>Torbutton makes extensive use of Contract ID hooking, and implements some |
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379 |
-of its own standalone components as well. Let's discuss the hooked components |
|
380 |
-first.</para> |
|
381 |
- |
|
382 |
-<sect3 id="sessionstore"> |
|
383 |
- <title><ulink |
|
384 |
-url="http://developer.mozilla.org/en/docs/nsISessionStore">@mozilla.org/browser/sessionstore;1</ulink> - |
|
385 |
-<ulink |
|
386 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/nsSessionStore2.js">components/nsSessionStore2.js</ulink> |
|
387 |
-and <ulink |
|
388 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/nsSessionStore3.js">components/nsSessionStore3.js</ulink></title> |
|
389 |
- |
|
390 |
-<para>These components address the <link linkend="disk">Disk Avoidance</link> |
|
391 |
-requirements of Torbutton. As stated in the requirements, Torbutton needs to |
|
392 |
-prevent Tor tabs from being written to disk by the Firefox session store for a |
|
393 |
-number of reasons, primary among them is the fact that Firefox can crash at |
|
394 |
-any time, and a restart can cause you to fetch tabs in the incorrect Tor |
|
395 |
-state.</para> |
|
396 |
- |
|
397 |
-<para>These components illustrate a complication with Firefox hooking: you can |
|
398 |
-only hook member functions of a class if they are published in an |
|
399 |
-interface that the class implements. Unfortunately, the sessionstore has no |
|
400 |
-published interface that is amenable to disabling the writing out of Tor tabs |
|
401 |
-in specific. As such, Torbutton had to include the <emphasis>entire</emphasis> |
|
402 |
-nsSessionStore from both Firefox 2 and Firefox 3, |
|
403 |
-with a couple of modifications to prevent tabs that were loaded with Tor |
|
404 |
-enabled from being written to disk, and some version detection code to |
|
405 |
-determine which component to load. The <ulink |
|
406 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/nsSessionStore3.diff">diff against the original session |
|
407 |
-store</ulink> is included in the SVN repository.</para> |
|
408 |
-</sect3> |
|
409 |
-<sect3> |
|
410 |
-<title><ulink |
|
411 |
-url="http://lxr.mozilla.org/seamonkey/source/browser/components/sessionstore/src/nsSessionStartup.js">@mozilla.org/browser/sessionstartup;1</ulink> - |
|
412 |
- <ulink |
|
413 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/crash-observer.js">components/crash-observer.js</ulink></title> |
|
414 |
- |
|
415 |
-<para>This component wraps the Firefox Session Startup component that is in |
|
416 |
-charge of <ulink |
|
417 |
-url="http://developer.mozilla.org/en/docs/Session_store_API">restoring saved |
|
418 |
-sessions</ulink>. The wrapper's only job is to intercept the |
|
419 |
-<function>doRestore()</function> function, which is called by Firefox if it is determined that the |
|
420 |
-browser crashed and the session needs to be restored. The wrapper notifies the |
|
421 |
-Torbutton chrome that the browser crashed by setting the pref |
|
422 |
-<command>extensions.torbutton.crashed</command>, or that it is a normal |
|
423 |
-startup via the pref <command>extensions.torbutton.noncrashed</command>. The Torbutton Chrome <ulink |
|
424 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIPrefBranch2.html#method_addObserver">listens for a |
|
425 |
-preference change</ulink> for this value and then does the appropriate cleanup. This |
|
426 |
-includes setting the Tor state to the one the user selected for crash recovery |
|
427 |
-in the preferences window (<command>extensions.torbutton.restore_tor</command>), and |
|
428 |
-restoring cookies for the corresponding cookie jar, if it exists.</para> |
|
429 |
- |
|
430 |
-<para>By performing this notification, this component assists in the |
|
431 |
-<link linkend="proxy">Proxy Obedience</link>, and <link |
|
432 |
-linkend="isolation">Network Isolation</link> requirements. |
|
433 |
-</para> |
|
434 |
- |
|
435 |
- |
|
436 |
-</sect3> |
|
437 |
-<sect3> |
|
438 |
-<title><ulink |
|
439 |
-url="http://www.xulplanet.com/references/xpcomref/comps/c_browserglobalhistory2.html">@mozilla.org/browser/global-history;2</ulink> |
|
440 |
-- <ulink |
|
441 |
- url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/ignore-history.js">components/ignore-history.js</ulink></title> |
|
442 |
- |
|
443 |
-<para>This component was contributed by <ulink |
|
444 |
-url="http://www.collinjackson.com/">Collin Jackson</ulink> as a method for defeating |
|
445 |
-CSS and Javascript-based methods of history disclosure. The global-history |
|
446 |
-component is what is used by Firefox to determine if a link was visited or not |
|
447 |
-(to apply the appropriate style to the link). By hooking the <ulink |
|
448 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIGlobalHistory2.html#method_isVisited">isVisited</ulink> |
|
449 |
-and <ulink |
|
450 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIGlobalHistory2.html#method_addURI">addURI</ulink> |
|
451 |
-methods, Torbutton is able to selectively prevent history items from being |
|
452 |
-added or being displayed as visited, depending on the Tor state and the user's |
|
453 |
-preferences. |
|
454 |
-</para> |
|
455 |
-<para> |
|
456 |
-This component helps satisfy the <link linkend="state">State Separation</link> |
|
457 |
-and <link linkend="disk">Disk Avoidance</link> requirements of Torbutton. |
|
458 |
-</para> |
|
459 |
-</sect3> |
|
460 |
-</sect2> |
|
461 |
-<sect2> |
|
462 |
-<title>New Components</title> |
|
463 |
- |
|
464 |
-<para>Torbutton creates four new components that are used throughout the |
|
465 |
-extension. These components do not hook any interfaces, nor are they used |
|
466 |
-anywhere besides Torbutton itself.</para> |
|
467 |
- |
|
468 |
-<sect3> |
|
469 |
-<title><ulink |
|
470 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js">@stanford.edu/cookie-jar-selector;2 |
|
471 |
-- components/cookie-jar-selector.js</ulink></title> |
|
472 |
- |
|
473 |
-<para>The cookie jar selector (also based on code from <ulink |
|
474 |
-url="http://www.collinjackson.com/">Collin |
|
475 |
-Jackson</ulink>) is used by the Torbutton chrome to switch between |
|
476 |
-Tor and Non-Tor cookies. Its operations are simple: sync cookies to disk, then |
|
477 |
-move the current cookies.txt file to the appropriate backup location |
|
478 |
-(cookies-tor.txt or cookies-nontor.txt), and then moving the other cookie jar |
|
479 |
-into place.</para> |
|
480 |
- |
|
481 |
-<para> |
|
482 |
-This component helps to address the <link linkend="state">State |
|
483 |
-Isolation</link> requirement of Torbutton. |
|
484 |
-</para> |
|
485 |
- |
|
486 |
-</sect3> |
|
487 |
-<sect3> |
|
488 |
-<title><ulink |
|
489 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/torbutton-logger.js">@torproject.org/torbutton-logger;1 |
|
490 |
-- components/torbutton-logger.js</ulink></title> |
|
491 |
- |
|
492 |
-<para>The torbutton logger component allows on-the-fly redirection of torbutton |
|
493 |
-logging messages to either Firefox stderr |
|
494 |
-(<command>extensions.torbutton.logmethod=0</command>), the Javascript error console |
|
495 |
-(<command>extensions.torbutton.logmethod=1</command>), or the DebugLogger extension (if |
|
496 |
-available - <command>extensions.torbutton.logmethod=2</command>). It also allows you to |
|
497 |
-change the loglevel on the fly by changing |
|
498 |
-<command>extensions.torbutton.loglevel</command> (1-5, 1 is most verbose). |
|
499 |
-</para> |
|
500 |
-</sect3> |
|
501 |
-<sect3 id="windowmapper"> |
|
502 |
- |
|
503 |
-<title><ulink |
|
504 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/window-mapper.js">@torproject.org/content-window-mapper;1 |
|
505 |
-- components/window-mapper.js</ulink></title> |
|
506 |
- |
|
507 |
-<para>Torbutton tags Firefox <ulink |
|
508 |
-url="http://www.xulplanet.com/references/elemref/ref_tabbrowser.html">tabs</ulink> with a special variable that indicates the Tor |
|
509 |
-state the tab was most recently used under to fetch a page. The problem is |
|
510 |
-that for many Firefox events, it is not possible to determine the tab that is |
|
511 |
-actually receiving the event. The Torbutton window mapper allows the Torbutton |
|
512 |
-chrome and other components to look up a <ulink |
|
513 |
-url="http://www.xulplanet.com/references/elemref/ref_tabbrowser.html">browser |
|
514 |
-tab</ulink> for a given <ulink |
|
515 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIDOMWindow.html">HTML content |
|
516 |
-window</ulink>. It does this by traversing all windows and all browsers, until it |
|
517 |
-finds the browser with the requested <ulink |
|
518 |
-url="http://www.xulplanet.com/references/elemref/ref_browser.html#prop_contentWindow">contentWindow</ulink> element. Since the content policy |
|
519 |
-and page loading in general can generate hundreds of these lookups, this |
|
520 |
-result is cached inside the component. |
|
521 |
-</para> |
|
522 |
-</sect3> |
|
523 |
-<sect3 id="contentpolicy"> |
|
524 |
-<title><ulink |
|
525 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cssblocker.js">@torproject.org/cssblocker;1 |
|
526 |
-- components/cssblocker.js</ulink></title> |
|
527 |
- |
|
528 |
-<para>This is a key component to Torbutton's security measures. When Tor is |
|
529 |
-toggled, Javascript is disabled, and pages are instructed to stop loading. |
|
530 |
-However, CSS is still able to perform network operations by loading styles for |
|
531 |
-onmouseover events and other operations. In addition, favicons can still be |
|
532 |
-loaded by the browser. The cssblocker component prevents this by implementing |
|
533 |
-and registering an <ulink |
|
534 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIContentPolicy.html">nsIContentPolicy</ulink>. |
|
535 |
-When an nsIContentPolicy is registered, Firefox checks every attempted network |
|
536 |
-request against its <ulink |
|
537 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIContentPolicy.html#method_shouldLoad">shouldLoad</ulink> |
|
538 |
-member function to determine if the load should proceed. In Torbutton's case, |
|
539 |
-the content policy looks up the appropriate browser tab using the <link |
|
540 |
-linkend="windowmapper">window mapper</link>, |
|
541 |
-and checks that tab's load tag against the current Tor state. If the tab was |
|
542 |
-loaded in a different state than the current state, the fetch is denied. |
|
543 |
-Otherwise, it is allowed.</para> This helps to achieve the <link |
|
544 |
-linkend="isolation">Network |
|
545 |
-Isolation</link> requirements of Torbutton. |
|
546 |
- |
|
547 |
-<para>In addition, the content policy also blocks website javascript from |
|
548 |
-<ulink url="http://pseudo-flaw.net/content/tor/torbutton/">querying for |
|
549 |
-versions and existence of extension chrome</ulink> while Tor is enabled, and |
|
550 |
-also masks the presence of Torbutton to website javascript while Tor is |
|
551 |
-disabled. </para> |
|
552 |
- |
|
553 |
-<para> |
|
554 |
- |
|
555 |
-Finally, some of the work that logically belongs to the content policy is |
|
556 |
-instead handled by the <command>torbutton_http_observer</command> and |
|
557 |
-<command>torbutton_weblistener</command> in <ulink |
|
558 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js">torbutton.js</ulink>. These two objects handle blocking of |
|
559 |
-Firefox 3 favicon loads, popups, and full page plugins, which for whatever |
|
560 |
-reason are not passed to the Firefox content policy itself (see Firefox Bugs |
|
561 |
-<ulink |
|
562 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=437014">437014</ulink> and |
|
563 |
-<ulink |
|
564 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=401296">401296</ulink>). |
|
565 |
- |
|
566 |
-</para> |
|
567 |
- |
|
568 |
-<!-- |
|
569 |
-FIXME: Hrmm, the content policy doesn't really lend itself well to display |
|
570 |
-this way.. People looking for this much detail should consult the source. |
|
571 |
- |
|
572 |
-<para> |
|
573 |
- <table rowheader="firstcol" frame='all'><title>Access Permissions Table</title> |
|
574 |
- <tgroup cols='5' align='left' colsep='1' rowsep='1'> |
|
575 |
- <tbody> |
|
576 |
- <row> |
|
577 |
- <entry></entry> |
|
578 |
- <entry>chrome/resource</entry> |
|
579 |
- <entry>a3</entry> |
|
580 |
- <entry>a4</entry> |
|
581 |
- <entry>a5</entry> |
|
582 |
- </row> |
|
583 |
- <row> |
|
584 |
- <entry>file</entry> |
|
585 |
- <entry>b2</entry> |
|
586 |
- <entry>b3</entry> |
|
587 |
- <entry>b4</entry> |
|
588 |
- <entry>b5</entry> |
|
589 |
- </row> |
|
590 |
- <row> |
|
591 |
- <entry>c1</entry> |
|
592 |
- <entry>c2</entry> |
|
593 |
- <entry>c3</entry> |
|
594 |
- <entry>c4</entry> |
|
595 |
- <entry>c5</entry> |
|
596 |
- </row> |
|
597 |
- <row> |
|
598 |
- <entry>d1</entry> |
|
599 |
- <entry>d2</entry> |
|
600 |
- <entry>d3</entry> |
|
601 |
- <entry>d4</entry> |
|
602 |
- <entry>d5</entry> |
|
603 |
- </row> |
|
604 |
- </tbody> |
|
605 |
- </tgroup> |
|
606 |
- </table> |
|
607 |
-</para> |
|
608 |
---> |
|
609 |
- |
|
610 |
-<para> |
|
611 |
- |
|
612 |
-This helps to fulfill both the <link |
|
613 |
-linkend="setpreservation">Anonymity Set Preservation</link> and the <link |
|
614 |
-linkend="undiscoverability">Tor Undiscoverability</link> requirements of |
|
615 |
-Torbutton.</para> |
|
616 |
- |
|
617 |
-</sect3> |
|
618 |
-</sect2> |
|
619 |
-</sect1> |
|
620 |
-<sect1> |
|
621 |
- <title>Chrome</title> |
|
622 |
- |
|
623 |
-<para>The chrome is where all the torbutton graphical elements and windows are |
|
624 |
-located. Each window is described as an <ulink |
|
625 |
-url="http://developer.mozilla.org/en/docs/XUL_Reference">XML file</ulink>, with zero or more Javascript |
|
626 |
-files attached. The scope of these Javascript files is their containing |
|
627 |
-window.</para> |
|
628 |
- |
|
629 |
-<sect2 id="browseroverlay"> |
|
630 |
-<title>Browser Overlay - <ulink |
|
631 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.xul">torbutton.xul</ulink></title> |
|
632 |
- |
|
633 |
-<para>The browser overlay, torbutton.xul, defines the toolbar button, the status |
|
634 |
-bar, and events for toggling the button. The overlay code is in <ulink |
|
635 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js">chrome/content/torbutton.js</ulink>. |
|
636 |
-It contains event handlers for preference update, shutdown, upgrade, and |
|
637 |
-location change events.</para> |
|
638 |
- |
|
639 |
-<para>The <ulink |
|
640 |
-url="http://www.xulplanet.com/references/xpcomref/comps/c_docloaderservice1.html">location |
|
641 |
-change</ulink> <ulink |
|
642 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebProgressListener.html">webprogress |
|
643 |
-listener</ulink>, <command>torbutton_weblistener</command> is perhaps the |
|
644 |
-most important part of the chrome from a security standpoint. It is a <ulink |
|
645 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebProgressListener.html">web |
|
646 |
-progress listener</ulink> that handles |
|
647 |
-receiving an event every time a page load or iframe load occurs. This class |
|
648 |
-eventually calls down to <function>torbutton_update_tags()</function> and |
|
649 |
-<function>torbutton_hookdoc()</function>, which apply the browser Tor load state tags, plugin |
|
650 |
-permissions, and install the Javascript hooks to hook the <ulink |
|
651 |
-url="http://phrogz.net/objJob/object.asp?id=224">Date</ulink> object and |
|
652 |
-the <ulink |
|
653 |
-url="http://developer.mozilla.org/en/docs/DOM:window.navigator">navigator</ulink> object (for timezone and platform information, |
|
654 |
-respectively).</para> |
|
655 |
-<para> |
|
656 |
-The browser overlay helps to satisfy a number of Torbutton requirements. These |
|
657 |
-are better enumerated in each of the Torbutton preferences below. However, |
|
658 |
-there are also a number of Firefox preferences set in |
|
659 |
-<function>torbutton_update_status()</function> that aren't governed by any |
|
660 |
-Torbutton setting. These are: |
|
661 |
-</para> |
|
662 |
-<orderedlist> |
|
663 |
- |
|
664 |
- <listitem><ulink |
|
665 |
-url="http://kb.mozillazine.org/Browser.bookmarks.livemark_refresh_seconds">browser.bookmarks.livemark_refresh_seconds</ulink> |
|
666 |
-<para> |
|
667 |
-This pref is set in an attempt to disable the fetching of LiveBookmarks via |
|
668 |
-Tor. Since users can potentially collect a large amount of live bookmarks to |
|
669 |
-very personal sites (blogs of friends, wikipedia articles they maintain, |
|
670 |
-comment feeds of their own blog), it is not possible to cleanly isolate these |
|
671 |
-fetches and they are simply disabled during Tor usage. |
|
672 |
-This helps to address the <link |
|
673 |
-linkend="state">State Separation</link> requirement. |
|
674 |
-Unfortunately <ulink |
|
675 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=436250">Firefox Bug |
|
676 |
-436250</ulink> prevents this from |
|
677 |
-functioning completely correctly. |
|
678 |
-</para> |
|
679 |
- </listitem> |
|
680 |
- |
|
681 |
- <listitem><ulink |
|
682 |
-url="http://kb.mozillazine.org/Network.security.ports.banned">network.security.ports.banned</ulink> |
|
683 |
- <para> |
|
684 |
-Torbutton sets this setting to add ports 8123, 8118, 9050 and 9051 (which it |
|
685 |
-reads from <command>extensions.torbutton.banned_ports</command>) to the list |
|
686 |
-of ports Firefox is forbidden to access. These ports are Polipo, Privoxy, Tor, |
|
687 |
-and the Tor control port, respectively. This is set for both Tor and Non-Tor |
|
688 |
-usage, and prevents websites from attempting to do http fetches from these |
|
689 |
-ports to see if they are open, which addresses the <link |
|
690 |
-linkend="undiscoverability">Tor Undiscoverability</link> requirement. |
|
691 |
- </para> |
|
692 |
- </listitem> |
|
693 |
- <listitem><ulink url="http://kb.mozillazine.org/Browser.send_pings">browser.send_pings</ulink> |
|
694 |
- <para> |
|
695 |
-This setting is currently always disabled. If anyone ever complains saying |
|
696 |
-that they *want* their browser to be able to send ping notifications to a |
|
697 |
-page or arbitrary link, I'll make this a pref or Tor-only. But I'm not holding |
|
698 |
-my breath. I haven't checked if the content policy is called for pings, but if |
|
699 |
-not, this setting helps with meeting the <link linkend="isolation">Network |
|
700 |
-Isolation</link> requirement. |
|
701 |
- </para> |
|
702 |
- </listitem> |
|
703 |
- <listitem><ulink |
|
704 |
-url="http://kb.mozillazine.org/Browser.safebrowsing.remoteLookups">browser.safebrowsing.remoteLookups</ulink> |
|
705 |
- <para> |
|
706 |
-Likewise for this setting. I find it hard to imagine anyone who wants to ask |
|
707 |
-Google in real time if each URL they visit is safe, especially when the list |
|
708 |
-of unsafe URLs is downloaded anyway. This helps fulfill the <link |
|
709 |
-linkend="disk">Disk Avoidance</link> requirement, by preventing your entire |
|
710 |
-browsing history from ending up on Google's disks. |
|
711 |
- </para> |
|
712 |
- </listitem> |
|
713 |
- <listitem><ulink |
|
714 |
-url="http://kb.mozillazine.org/Browser.safebrowsing.enabled">browser.safebrowsing.enabled</ulink> |
|
715 |
- <para> |
|
716 |
-Safebrowsing does <ulink |
|
717 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=360387">unauthenticated |
|
718 |
-updates under Firefox 2</ulink>, so it is disabled during Tor usage. |
|
719 |
-This helps fulfill the <link linkend="updates">Update |
|
720 |
-Safety</link> requirement. Firefox 3 has the fix for that bug, and so |
|
721 |
-safebrowsing updates are enabled during Tor usage. |
|
722 |
- </para> |
|
723 |
- </listitem> |
|
724 |
- <listitem><ulink |
|
725 |
-url="http://kb.mozillazine.org/Network.protocol-handler.warn-external.%28protocol%29">network.protocol-handler.warn-external.(protocol)</ulink> |
|
726 |
- <para> |
|
727 |
-If Tor is enabled, we need to prevent random external applications from |
|
728 |
-launching without at least warning the user. This group of settings only |
|
729 |
-partially accomplishes this, however. Applications can still be launched via |
|
730 |
-plugins. The mechanisms for handling this are described under the "Disable |
|
731 |
-Plugins During Tor Usage" preference. This helps fulfill the <link |
|
732 |
-linkend="proxy">Proxy Obedience</link> requirement, by preventing external |
|
733 |
-applications from accessing network resources at the command of Tor-fetched |
|
734 |
-pages. |
|
735 |
- </para> |
|
736 |
-</listitem> |
|
737 |
-</orderedlist> |
|
738 |
-</sect2> |
|
739 |
-<sect2> |
|
740 |
- <title>Preferences Window - <ulink |
|
741 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/preferences.xul">preferences.xul</ulink></title> |
|
742 |
- |
|
743 |
-<para>The preferences window of course lays out the Torbutton preferences, with |
|
744 |
-handlers located in <ulink |
|
745 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/preferences.js">chrome/content/preferences.js</ulink>.</para> |
|
746 |
-</sect2> |
|
747 |
-<sect2> |
|
748 |
- <title>Other Windows</title> |
|
749 |
- |
|
750 |
-<para>There are additional windows that describe popups for right clicking on |
|
751 |
-the status bar, the toolbutton, and the about page.</para> |
|
752 |
- |
|
753 |
-</sect2> |
|
754 |
-</sect1> |
|
755 |
- |
|
756 |
-<sect1> |
|
757 |
- <title>Toggle Code Path</title> |
|
758 |
- <para> |
|
759 |
- |
|
760 |
-The act of toggling is connected to <function>torbutton_toggle()</function> |
|
761 |
-via the <ulink |
|
762 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.xul">torbutton.xul</ulink> |
|
763 |
-and <ulink |
|
764 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/popup.xul">popup.xul</ulink> |
|
765 |
-overlay files. Most of the work in the toggling process is present in <ulink |
|
766 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js">torbutton.js</ulink> |
|
767 |
- |
|
768 |
-</para> |
|
769 |
-<para> |
|
770 |
- |
|
771 |
-Toggling is a 3 stage process: Button Click, Proxy Update, and |
|
772 |
-Settings Update. These stages are reflected in the prefs |
|
773 |
-<command>extensions.torbutton.tor_enabled</command>, |
|
774 |
-<command>extensions.torbutton.proxies_applied</command>, and |
|
775 |
-<command>extensions.torbutton.settings_applied</command>. The reason for the |
|
776 |
-three stage preference update is to ensure immediate enforcement of <link |
|
777 |
-linkend="isolation">Network Isolation</link> via the <link |
|
778 |
-linkend="contentpolicy">content policy</link>. Since the content window |
|
779 |
-javascript runs on a different thread than the chrome javascript, it is |
|
780 |
-important to properly convey the stages to the content policy to avoid race |
|
781 |
-conditions and leakage, especially with <ulink |
|
782 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=409737">Firefox Bug |
|
783 |
-409737</ulink> unfixed. The content policy does not allow any network activity |
|
784 |
-whatsoever during this three stage transition. |
|
785 |
- |
|
786 |
- </para> |
|
787 |
- <sect2> |
|
788 |
- <title>Button Click</title> |
|
789 |
- <para> |
|
790 |
- |
|
791 |
-This is the first step in the toggling process. When the user clicks the |
|
792 |
-toggle button or the toolbar, <function>torbutton_toggle()</function> is |
|
793 |
-called. This function checks the current Tor status by comparing the current |
|
794 |
-proxy settings to the selected Tor settings, and then sets the proxy settings |
|
795 |
-to the opposite state, and sets the pref |
|
796 |
-<command>extensions.torbutton.tor_enabled</command> to reflect the new state. |
|
797 |
-It is this proxy pref update that gives notification via the <ulink |
|
798 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIPrefBranch2.html#method_addObserver">pref |
|
799 |
-observer</ulink> |
|
800 |
-<command>torbutton_unique_pref_observer</command> to perform the rest of the |
|
801 |
-toggle. |
|
802 |
- |
|
803 |
- </para> |
|
804 |
- </sect2> |
|
805 |
- <sect2> |
|
806 |
- <title>Proxy Update</title> |
|
807 |
- <para> |
|
808 |
- |
|
809 |
-When Torbutton receives any proxy change notifications via its |
|
810 |
-<command>torbutton_unique_pref_observer</command>, it calls |
|
811 |
-<function>torbutton_set_status()</function> which checks against the Tor |
|
812 |
-settings to see if the Tor proxy settings match the current settings. If so, |
|
813 |
-it calls <function>torbutton_update_status()</function>, which determines if |
|
814 |
-the Tor state has actually changed, and sets |
|
815 |
-<command>extensions.torbutton.proxies_applied</command> to the appropriate Tor |
|
816 |
-state value, and ensures that |
|
817 |
-<command>extensions.torbutton.tor_enabled</command> is also set to the correct |
|
818 |
-value. This is decoupled from the button click functionalty via the pref |
|
819 |
-observer so that other addons (such as SwitchProxy) can switch the proxy |
|
820 |
-settings between multiple proxies. |
|
821 |
- |
|
822 |
- </para> |
|
823 |
- </sect2> |
|
824 |
- <sect2> |
|
825 |
- <title>Settings Update</title> |
|
826 |
- <para> |
|
827 |
- |
|
828 |
-The next stage is also handled by |
|
829 |
-<function>torbutton_update_status()</function>. This function sets scores of |
|
830 |
-Firefox preferences, saving the original values to prefs under |
|
831 |
-<command>extensions.torbutton.saved.*</command>, and performs the history |
|
832 |
-clearing, cookie jaring, and ssl certificate jaring work of Torbutton. At the |
|
833 |
-end of its work, it sets |
|
834 |
-<command>extensions.torbutton.settings_applied</command>, which signifies the |
|
835 |
-completion of the toggle operation to the <link |
|
836 |
-linkend="contentpolicy">content policy</link>. |
|
837 |
- |
|
838 |
- </para> |
|
839 |
- </sect2> |
|
840 |
-</sect1> |
|
841 |
- |
|
842 |
-<sect1> |
|
843 |
- <title>Description of Options</title> |
|
844 |
- |
|
845 |
-<para>This section provides a detailed description of Torbutton's options. Each |
|
846 |
-option is presented as the string from the preferences window, a summary, the |
|
847 |
-preferences it touches, and the effect this has on the components, chrome, and |
|
848 |
-browser properties.</para> |
|
849 |
- <sect2> |
|
850 |
- <title>Test Settings</title> |
|
851 |
- <para> |
|
852 |
-This button under the Proxy Settings tab provides a way to verify that the |
|
853 |
-proxy settings are correct, and actually do route through the Tor network. It |
|
854 |
-performs this check by issuing an <ulink |
|
855 |
-url="http://developer.mozilla.org/en/docs/XMLHttpRequest">XMLHTTPRequest</ulink> |
|
856 |
-for <ulink |
|
857 |
-url="https://check.torproject.org/?TorButton=True">https://check.torproject.org/?Torbutton=True</ulink>. |
|
858 |
-This is a special page that returns very simple, yet well-formed XHTML that |
|
859 |
-Torbutton can easily inspect for a hidden link with an id of |
|
860 |
-<command>TorCheckResult</command> and a target of <command>success</command> |
|
861 |
-or <command>failure</command> to indicate if the |
|
862 |
-user hit the page from a Tor IP, a non-Tor IP. This check is handled in |
|
863 |
-<function>torbutton_test_settings()</function> in <ulink |
|
864 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js">torbutton.js</ulink>. |
|
865 |
-Presenting the results to the user is handled by the <ulink |
|
866 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/preferences.xul">preferences |
|
867 |
-window</ulink> |
|
868 |
-callback <function>torbutton_prefs_test_settings()</function> in <ulink |
|
869 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/preferences.js">preferences.js</ulink>. |
|
870 |
- |
|
871 |
- </para> |
|
872 |
- </sect2> |
|
873 |
- <sect2 id="plugins"> |
|
874 |
- <title>Disable plugins on Tor Usage (crucial)</title> |
|
875 |
- |
|
876 |
- <para>Option: <command>extensions.torbutton.no_tor_plugins</command></para> |
|
877 |
- |
|
878 |
- <para>Enabling this preference causes the above mentioned Torbutton chrome web progress |
|
879 |
- listener <command>torbutton_weblistener</command> to disable Java via <command>security.enable_java</command> and to disable |
|
880 |
- plugins via the browser <ulink |
|
881 |
- url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIDocShell.html">docShell</ulink> |
|
882 |
- attribute <command>allowPlugins</command>. These flags are set every time a new window is |
|
883 |
- created (<function>torbutton_tag_new_browser()</function>), every time a web |
|
884 |
-load |
|
885 |
-event occurs |
|
886 |
- (<function>torbutton_update_tags()</function>), and every time the tor state is changed |
|
887 |
- (<function>torbutton_update_status()</function>). As a backup measure, plugins are also |
|
888 |
- prevented from loading by the content policy in <ulink |
|
889 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cssblocker.js">@torproject.org/cssblocker;1</ulink> if Tor is |
|
890 |
- enabled and this option is set. |
|
891 |
- </para> |
|
892 |
- |
|
893 |
- <para>Even all this turns out to be insufficient if the user directly |
|
894 |
- clicks on a plugin-handled mime-type. <ulink |
|
895 |
-url="http://www.janusvm.com/goldy/pdf/">In this case</ulink> (and also <ulink |
|
896 |
-url="http://www.janusvm.com/goldy/side-channels/frames/">this |
|
897 |
-one</ulink>), the browser decides that |
|
898 |
- maybe it should ignore all these other settings and load the plugin anyways, |
|
899 |
- because maybe the user really did want to load it (never mind this same |
|
900 |
- load-style could happen automatically with meta-refresh or any number of |
|
901 |
- other ways..). To handle these cases, Torbutton stores a list of plugin-handled |
|
902 |
- mime-types, and sets the pref |
|
903 |
-<command>plugin.disable_full_page_plugin_for_types</command> to this list. |
|
904 |
-Additionally, (since nothing can be assumed when relying on Firefox |
|
905 |
-preferences and internals) if it detects a load of one of them from the web progress |
|
906 |
- listener, it cancels the request, tells the associated DOMWindow |
|
907 |
-to stop loading, clears the document, AND throws an exception. Anything short |
|
908 |
-of all this and |
|
909 |
- the plugin managed to find some way to load. |
|
910 |
- </para> |
|
911 |
- |
|
912 |
- <para> |
|
913 |
- All this could be avoided, of course, if Firefox would either <ulink |
|
914 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=401296">obey |
|
915 |
- allowPlugins</ulink> for directly visited URLs, or notify its content policy for such |
|
916 |
- loads either <ulink |
|
917 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=309524">via</ulink> <ulink |
|
918 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=380556">shouldProcess</ulink> or shouldLoad. The fact that it does not is |
|
919 |
- not very encouraging. |
|
920 |
- </para> |
|
921 |
- <para> |
|
922 |
- |
|
923 |
-Since most plugins completely ignore browser proxy settings, the actions |
|
924 |
-performed by this setting are crucial to satisfying the <link |
|
925 |
-linkend="proxy">Proxy Obedience</link> requirement. |
|
926 |
- |
|
927 |
- </para> |
|
928 |
-</sect2> |
|
929 |
-<sect2> |
|
930 |
- <title>Isolate Dynamic Content to Tor State (crucial)</title> |
|
931 |
- |
|
932 |
- <para>Option: <command>extensions.torbutton.isolate_content</command></para> |
|
933 |
- |
|
934 |
-<para>Enabling this preference is what enables the <ulink |
|
935 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cssblocker.js">@torproject.org/cssblocker;1</ulink> content policy |
|
936 |
-mentioned above, and causes it to block content load attempts in pages an |
|
937 |
-opposite Tor state from the current state. Freshly loaded <ulink |
|
938 |
-url="http://www.xulplanet.com/references/elemref/ref_tabbrowser.html">browser |
|
939 |
-tabs</ulink> are tagged |
|
940 |
-with a <command>__tb_load_state</command> member in |
|
941 |
-<function>torbutton_update_tags()</function> and this |
|
942 |
-value is compared against the current tor state in the content policy.</para> |
|
943 |
- |
|
944 |
-<para>It also kills all Javascript in each page loaded under that state by |
|
945 |
-toggling the <command>allowJavascript</command> <ulink |
|
946 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIDocShell.html">docShell</ulink> property, and issues a |
|
947 |
-<ulink |
|
948 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebNavigation.html#method_stop">webNavigation.stop(webNavigation.STOP_ALL)</ulink> to each browser tab (the |
|
949 |
-equivalent of hitting the STOP button).</para> |
|
950 |
- |
|
951 |
-<para> |
|
952 |
- |
|
953 |
-Unfortunately, <ulink |
|
954 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=409737">Firefox bug |
|
955 |
-409737</ulink> prevents <command>docShell.allowJavascript</command> from killing |
|
956 |
-all event handlers, and event handlers registered with <ulink |
|
957 |
-url="http://developer.mozilla.org/en/docs/DOM:element.addEventListener">addEventListener()</ulink> |
|
958 |
-are still able to execute. The <link linkend="contentpolicy">Torbutton Content |
|
959 |
-Policy</link> should prevent such code from performing network activity within |
|
960 |
-the current tab, but activity that happens via a popup window or via a |
|
961 |
-Javascript redirect can still slip by. For this reason, Torbutton blocks |
|
962 |
-popups by checking for a valid <ulink |
|
963 |
-url="http://developer.mozilla.org/en/docs/DOM:window.opener">window.opener</ulink> |
|
964 |
-attribute in <function>torbutton_check_progress()</function>. If the window |
|
965 |
-has an opener from a different Tor state, its load is blocked. The content |
|
966 |
-policy also takes similar action to prevent Javascript redirects. This also |
|
967 |
-has the side effect/feature of preventing the user from following any links |
|
968 |
-from a page loaded in an opposite Tor state. |
|
969 |
- |
|
970 |
-</para> |
|
971 |
- |
|
972 |
-<para> |
|
973 |
-This setting is responsible for satisfying the <link |
|
974 |
-linkend="isolation">Network Isolation</link> requirement. |
|
975 |
-</para> |
|
976 |
- |
|
977 |
-</sect2> |
|
978 |
-<sect2 id="jshooks"> |
|
979 |
- |
|
980 |
-<title>Hook Dangerous Javascript (crucial)</title> |
|
981 |
- |
|
982 |
- <para>Option: <command>extensions.torbutton.kill_bad_js</command></para> |
|
983 |
- |
|
984 |
-<para>This setting enables injection of the <ulink |
|
985 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/jshooks.js">Javascript |
|
986 |
-hooking code</ulink>. Javascript is injected into |
|
987 |
-pages to hook the <ulink url="http://phrogz.net/objJob/object.asp?id=224">Date |
|
988 |
-class</ulink> to mask your timezone. This is done in the chrome in |
|
989 |
-<function>torbutton_hookdoc()</function>, which is called ultimately by both the |
|
990 |
-<ulink |
|
991 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebProgressListener.html">webprogress |
|
992 |
-listener</ulink> <command>torbutton_weblistener</command> and the <link |
|
993 |
-linkend="contentpolicy">content policy</link> (the latter being a hack to handle |
|
994 |
-javascript: urls). This behavior helps to satisfy the <link |
|
995 |
-linkend="location">Location Neutrality</link> requirement. |
|
996 |
- |
|
997 |
-</para> |
|
998 |
-<para> |
|
999 |
- |
|
1000 |
-In addition, this setting also hooks various resolution properties of the |
|
1001 |
-<ulink url="http://developer.mozilla.org/en/docs/DOM:window">window</ulink>, |
|
1002 |
-<ulink |
|
1003 |
-url="http://developer.mozilla.org/en/docs/DOM:window.screen">window.screen</ulink>, |
|
1004 |
-and <ulink |
|
1005 |
-url="http://developer.mozilla.org/en/docs/DOM:window.navigator">window.navigator</ulink> |
|
1006 |
-to mask window size information and user agent properties not handled by the |
|
1007 |
-standard Firefox user agent override settings. The resolution hooks |
|
1008 |
-effectively make the Firefox browser window appear to websites as if the renderable area |
|
1009 |
-takes up the entire desktop, has no toolbar or other GUI element space, and |
|
1010 |
-the desktop itself has no toolbars. |
|
1011 |
-These hooks drastically reduce the amount of information available to do <link |
|
1012 |
-linkend="fingerprinting">anonymity set reduction attacks</link> and help to |
|
1013 |
-meet the <link linkend="setpreservation">Anonymity Set Preservation</link> |
|
1014 |
-requirements. |
|
1015 |
- |
|
1016 |
-</para> |
|
1017 |
-</sect2> |
|
1018 |
-<sect2> |
|
1019 |
-<title>Resize windows to multiples of 50px during Tor usage (recommended)</title> |
|
1020 |
- |
|
1021 |
- <para>Option: <command>extensions.torbutton.resize_windows</command></para> |
|
1022 |
- |
|
1023 |
-<para> |
|
1024 |
- |
|
1025 |
-This option drastically cuts down on the number of distinct anonymity sets |
|
1026 |
-that divide the Tor web userbase. Without this setting, the dimensions for a |
|
1027 |
-typical browser window range from 600-1200 horizontal pixels and 400-1000 |
|
1028 |
-vertical pixels, or about 600x600 = 360000 different sets. Resizing the |
|
1029 |
-browser window to multiples of 50 on each side reduces the number of sets by |
|
1030 |
-50^2, bringing the total number of sets to 144. Of course, the distribution |
|
1031 |
-among these sets are not uniform, but scaling by 50 will improve the situation |
|
1032 |
-due to this non-uniformity for users in the less common resolutions. |
|
1033 |
-Obviously the ideal situation would be to lie entirely about the browser |
|
1034 |
-window size, but this will likely cause all sorts of rendering issues, and is |
|
1035 |
-also not implementable in a foolproof way from extension land. |
|
1036 |
- |
|
1037 |
-</para> |
|
1038 |
-<para> |
|
1039 |
- |
|
1040 |
-The implementation of this setting is spread across a couple of different |
|
1041 |
-locations in the Torbutton javascript <link linkend="browseroverlay">browser |
|
1042 |
-overlay</link>. Since resizing minimized windows causes them to be restored, |
|
1043 |
-and since maximized windows remember their previous size to the pixel, windows |
|
1044 |
-must be resized before every document load (at the time of browser tagging) |
|
1045 |
-via <function>torbutton_check_round()</function>, called by |
|
1046 |
-<function>torbutton_update_tags()</function>. To prevent drift, the extension |
|
1047 |
-tracks the original values of the windows and uses this to perform the |
|
1048 |
-rounding on document load. In addition, to prevent the user from resizing a |
|
1049 |
-window to a non-50px multiple, a resize listener |
|
1050 |
-(<function>torbutton_do_resize()</function>) is installed on every new browser |
|
1051 |
-window to record the new size and round it to a 50px multiple while Tor is |
|
1052 |
-enabled. In all cases, the browser's contentWindow.innerWidth and innerHeight |
|
1053 |
-are set. This ensures that there is no discrepancy between the 50 pixel cutoff |
|
1054 |
-and the actual renderable area of the browser (so that it is not possible to |
|
1055 |
-infer toolbar size/presence by the distance to the nearest 50 pixel roundoff). |
|
1056 |
- |
|
1057 |
-</para> |
|
1058 |
-<para> |
|
1059 |
-This setting helps to meet the <link |
|
1060 |
-linkend="setpreservation">Anonymity Set Preservation</link> requirements. |
|
1061 |
-</para> |
|
1062 |
-</sect2> |
|
1063 |
-<sect2> |
|
1064 |
-<title>Disable Updates During Tor (recommended)</title> |
|
1065 |
- |
|
1066 |
- <para>Option: <command>extensions.torbutton.no_updates</command></para> |
|
1067 |
- |
|
1068 |
- <para>This setting causes Torbutton to disable the four <ulink |
|
1069 |
-url="http://wiki.mozilla.org/Update:Users/Checking_For_Updates#Preference_Controls_and_State">Firefox |
|
1070 |
-update settings</ulink> during Tor |
|
1071 |
- usage: <command>extensions.update.enabled</command>, |
|
1072 |
-<command>app.update.enabled</command>, |
|
1073 |
- <command>app.update.auto</command>, and |
|
1074 |
-<command>browser.search.update</command>. These prevent the |
|
1075 |
- browser from updating extensions, checking for Firefox upgrades, and |
|
1076 |
- checking for search plugin updates while Tor is enabled. |
|
1077 |
- </para> |
|
1078 |
-<para> |
|
1079 |
-This setting satisfies the <link |
|
1080 |
-linkend="updates">Update Safety</link> requirement. |
|
1081 |
-</para> |
|
1082 |
-</sect2> |
|
1083 |
-<sect2> |
|
1084 |
- |
|
1085 |
-<title>Disable Search Suggestions during Tor (recommended)</title> |
|
1086 |
- |
|
1087 |
- <para>Option: <command>extensions.torbutton.no_search</command></para> |
|
1088 |
- |
|
1089 |
-<para> |
|
1090 |
-This setting causes Torbutton to disable <ulink |
|
1091 |
-url="http://kb.mozillazine.org/Browser.search.suggest.enabled"><command>browser.search.suggest.enabled</command></ulink> |
|
1092 |
-during Tor usage. |
|
1093 |
-This governs if you get Google search suggestions during Tor |
|
1094 |
-usage. Your Google cookie is transmitted with google search suggestions, hence |
|
1095 |
-this is recommended to be disabled. |
|
1096 |
- |
|
1097 |
-</para> |
|
1098 |
-<para> |
|
1099 |
-While this setting doesn't satisfy any Torbutton requirements, the fact that |
|
1100 |
-cookies are transmitted for partially typed queries does not seem desirable |
|
1101 |
-for Tor usage. |
|
1102 |
-</para> |
|
1103 |
-</sect2> |
|
1104 |
-<sect2> |
|
1105 |
-<title>Block Tor/Non-Tor access to network from file:// urls (recommended)</title> |
|
1106 |
- <para>Option: |
|
1107 |
- <simplelist> |
|
1108 |
- <member><command>extensions.torbutton.block_tor_file_net</command></member> |
|
1109 |
- <member><command>extensions.torbutton.block_nontor_file_net</command></member> |
|
1110 |
- </simplelist> |
|
1111 |
- </para> |
|
1112 |
- |
|
1113 |
-<para> |
|
1114 |
- |
|
1115 |
-These settings prevent file urls from performing network operations during the |
|
1116 |
-respective Tor states. Firefox 2's implementation of same origin policy allows |
|
1117 |
-file urls to read and <ulink |
|
1118 |
-url="http://www.gnucitizen.org/blog/content-disposition-hacking/">submit |
|
1119 |
-arbitrary files from the local filesystem</ulink> to arbitrary websites. To |
|
1120 |
-make matters worse, the 'Content-Disposition' header can be injected |
|
1121 |
-arbitrarily by exit nodes to trick users into running arbitrary html files in |
|
1122 |
-the local context. These preferences cause the <link |
|
1123 |
-linkend="contentpolicy">content policy</link> to block access to any network |
|
1124 |
-resources from File urls during the appropriate Tor state. |
|
1125 |
- |
|
1126 |
-</para> |
|
1127 |
-<para> |
|
1128 |
- |
|
1129 |
-This preference helps to ensure Tor's <link linkend="isolation">Network |
|
1130 |
-Isolation</link> requirement, by preventing file urls from executing network |
|
1131 |
-operations in opposite Tor states. Also, allowing pages to submit arbitrary |
|
1132 |
-files to arbitrary sites just generally seems like a bad idea. |
|
1133 |
- |
|
1134 |
-</para> |
|
1135 |
-</sect2> |
|
1136 |
-<sect2> |
|
1137 |
- |
|
1138 |
-<title>Close all Tor/Non-Tor tabs and windows on toggle (optional)</title> |
|
1139 |
- |
|
1140 |
- <para>Options: |
|
1141 |
- <simplelist> |
|
1142 |
- <member><command>extensions.torbutton.close_nontor</command></member> |
|
1143 |
- <member><command>extensions.torbutton.close_tor</command></member> |
|
1144 |
- </simplelist> |
|
1145 |
- </para> |
|
1146 |
- |
|
1147 |
-<para> |
|
1148 |
- |
|
1149 |
-These settings cause Torbutton to enumerate through all windows and close all |
|
1150 |
-tabs in each window for the appropriate Tor state. This code can be found in |
|
1151 |
-<function>torbutton_update_status()</function>. The main reason these settings |
|
1152 |
-exist is as a backup mechanism in the event of any Javascript or content policy |
|
1153 |
-leaks due to <ulink |
|
1154 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=409737">Firefox Bug |
|
1155 |
-409737</ulink>. Torbutton currently tries to block all Javascript network |
|
1156 |
-activity via the content policy, but until that bug is fixed, there is some |
|
1157 |
-risk that there are alternate ways to bypass the policy. This option is |
|
1158 |
-available as an extra assurance of <link linkend="isolation">Network |
|
1159 |
-Isolation</link> for those who would like to be sure that when Tor is toggled |
|
1160 |
-all page activity has ceased. It also serves as a potential future workaround |
|
1161 |
-in the event a content policy failure is discovered, and provides an additional |
|
1162 |
-level of protection for the <link linkend="disk">Disk Avoidance</link> |
|
1163 |
-protection so that browser state is not sitting around waiting to be swapped |
|
1164 |
-out longer than necessary. |
|
1165 |
- |
|
1166 |
-</para> |
|
1167 |
-<para> |
|
1168 |
-While this setting doesn't satisfy any Torbutton requirements, the fact that |
|
1169 |
-cookies are transmitted for partially typed queries does not seem desirable |
|
1170 |
-for Tor usage. |
|
1171 |
-</para> |
|
1172 |
-</sect2> |
|
1173 |
- |
|
1174 |
-<sect2> |
|
1175 |
-<title>Isolate Access to History navigation to Tor state (crucial)</title> |
|
1176 |
- <para>Option: <command>extensions.torbutton.block_js_history</command></para> |
|
1177 |
- <para> |
|
1178 |
-This setting determines if Torbutton installs an <ulink |
|
1179 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsISHistoryListener.html">nsISHistoryListener</ulink> |
|
1180 |
-attached to the <ulink |
|
1181 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsISHistory.html">sessionHistory</ulink> of |
|
1182 |
-of each browser's <ulink |
|
1183 |
-url="http://www.xulplanet.com/references/xpcomref/comps/c_webshell1.html">webNavigatator</ulink>. |
|
1184 |
-The nsIShistoryListener is instantiated with a reference to the containing |
|
1185 |
-browser window and blocks the back, forward, and reload buttons on the browser |
|
1186 |
-navigation bar when Tor is in an opposite state than the one to load the |
|
1187 |
-current tab. In addition, Tor clears the session history during a new document |
|
1188 |
-load if this setting is enabled. |
|
1189 |
- |
|
1190 |
- </para> |
|
1191 |
- <para> |
|
1192 |
- |
|
1193 |
-This is marked as a crucial setting in part |
|
1194 |
-because Javascript access to the history object is indistinguishable from |
|
1195 |
-user clicks, and because |
|
1196 |
-<ulink |
|
1197 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=409737">Firefox Bug |
|
1198 |
-409737</ulink> allows javascript to execute in opposite Tor states, javascript |
|
1199 |
-can issue reloads after Tor toggle to reveal your original IP. Even without |
|
1200 |
-this bug, however, Javascript is still able to access previous pages in your |
|
1201 |
-session history that may have been loaded under a different Tor state, to |
|
1202 |
-attempt to correlate your activity. |
|
1203 |
- |
|
1204 |
- </para> |
|
1205 |
- <para> |
|
1206 |
- |
|
1207 |
-This setting helps to fulfill Torbutton's <link linkend="state">State |
|
1208 |
-Separation</link> and (until Bug 409737 is fixed) <link linkend="isolation">Network Isolation</link> |
|
1209 |
-requirements. |
|
1210 |
- |
|
1211 |
- </para> |
|
1212 |
-</sect2> |
|
1213 |
- |
|
1214 |
- |
|
1215 |
-<sect2> |
|
1216 |
-<title>History Access Settings</title> |
|
1217 |
- |
|
1218 |
- <para>Options: |
|
1219 |
- <simplelist> |
|
1220 |
- <member><command>extensions.torbutton.block_thread</command></member> |
|
1221 |
- <member><command>extensions.torbutton.block_nthread</command></member> |
|
1222 |
- <member><command>extensions.torbutton.block_thwrite</command></member> |
|
1223 |
- <member><command>extensions.torbutton.block_nthwrite</command></member> |
|
1224 |
- </simplelist> |
|
1225 |
- </para> |
|
1226 |
- |
|
1227 |
-<para>These four settings govern the behavior of the <ulink |
|
1228 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/ignore-history.js">components/ignore-history.js</ulink> |
|
1229 |
-history blocker component mentioned above. By hooking the browser's view of |
|
1230 |
-the history itself via the <ulink |
|
1231 |
-url="http://www.xulplanet.com/references/xpcomref/comps/c_browserglobalhistory2.html">mozilla.org/browser/global-history;2</ulink> |
|
1232 |
-component, this mechanism defeats all document-based <ulink |
|
1233 |
-url="http://gemal.dk/browserspy/css.html">history disclosure |
|
1234 |
-attacks</ulink>, including <ulink |
|
1235 |
-url="http://ha.ckers.org/weird/CSS-history.cgi">CSS-only attacks</ulink>. |
|
1236 |
-</para> |
|
1237 |
-<para> |
|
1238 |
- |
|
1239 |
-On Firefox 3, the history write settings also govern if Torbutton sets |
|
1240 |
-<command>browser.history_expire_days</command> to 0 on the appropriate Tor |
|
1241 |
-state, which <ulink |
|
1242 |
-url="http://developer.mozilla.org/en/docs/index.php?title=nsINavHistoryService#Attributes">should |
|
1243 |
-disable</ulink> all <ulink |
|
1244 |
-url="http://developer.mozilla.org/en/docs/Places">Places</ulink> database |
|
1245 |
-writes. |
|
1246 |
- |
|
1247 |
-</para> |
|
1248 |
-<para> |
|
1249 |
-This setting helps to satisfy the <link |
|
1250 |
-linkend="state">State Separation</link> and <link |
|
1251 |
-linkend="disk">Disk Avoidance</link> requirements. |
|
1252 |
-</para> |
|
1253 |
- |
|
1254 |
-</sect2> |
|
1255 |
-<sect2> |
|
1256 |
- |
|
1257 |
-<title>Clear History During Tor Toggle (optional)</title> |
|
1258 |
- |
|
1259 |
-<para>Option: <command>extensions.torbutton.clear_history</command></para> |
|
1260 |
- |
|
1261 |
-<para>This setting governs if Torbutton calls |
|
1262 |
-<ulink |
|
1263 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIBrowserHistory.html#method_removeAllPages">nsIBrowserHistory.removeAllPages</ulink> |
|
1264 |
-and <ulink |
|
1265 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsISHistory.html#method_PurgeHistory">nsISHistory.PurgeHistory</ulink> |
|
1266 |
-for each tab on Tor toggle.</para> |
|
1267 |
-<para> |
|
1268 |
-This setting is an optional way to help satisfy the <link |
|
1269 |
-linkend="state">State Separation</link> requirement. |
|
1270 |
-</para> |
|
1271 |
- |
|
1272 |
-</sect2> |
|
1273 |
-<sect2> |
|
1274 |
- |
|
1275 |
-<title>Block Password+Form saving during Tor/Non-Tor</title> |
|
1276 |
- |
|
1277 |
-<para>Options: |
|
1278 |
- <simplelist> |
|
1279 |
- <member><command>extensions.torbutton.block_tforms</command></member> |
|
1280 |
- <member><command>extensions.torbutton.block_ntforms</command></member> |
|
1281 |
- </simplelist> |
|
1282 |
- </para> |
|
1283 |
- |
|
1284 |
-<para>These settings govern if Torbutton disables |
|
1285 |
-<command>browser.formfill.enable</command> |
|
1286 |
-and <command>signon.rememberSignons</command> during Tor and Non-Tor usage. |
|
1287 |
-Since form fields can be read at any time by Javascript, this setting is a lot |
|
1288 |
-more important than it seems. |
|
1289 |
-</para> |
|
1290 |
- |
|
1291 |
-<para> |
|
1292 |
-This setting helps to satisfy the <link |
|
1293 |
-linkend="state">State Separation</link> and <link |
|
1294 |
-linkend="disk">Disk Avoidance</link> requirements. |
|
1295 |
-</para> |
|
1296 |
- |
|
1297 |
-</sect2> |
|
1298 |
-<sect2> |
|
1299 |
- <title>Block Tor disk cache and clear all cache on Tor Toggle</title> |
|
1300 |
- |
|
1301 |
- <para>Option: <command>extensions.torbutton.clear_cache</command> |
|
1302 |
- </para> |
|
1303 |
- |
|
1304 |
-<para>This option causes Torbutton to call <ulink |
|
1305 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsICacheService.html#method_evictEntries">nsICacheService.evictEntries(0)</ulink> |
|
1306 |
-on Tor toggle to remove all entries from the cache. In addition, this setting |
|
1307 |
-causes Torbutton to set <ulink |
|
1308 |
-url="http://kb.mozillazine.org/Browser.cache.disk.enable">browser.cache.disk.enable</ulink> to false. |
|
1309 |
-</para> |
|
1310 |
-<para> |
|
1311 |
-This setting helps to satisfy the <link |
|
1312 |
-linkend="state">State Separation</link> and <link |
|
1313 |
-linkend="disk">Disk Avoidance</link> requirements. |
|
1314 |
-</para> |
|
1315 |
- |
|
1316 |
-</sect2> |
|
1317 |
-<sect2> |
|
1318 |
- <title>Block disk and memory cache during Tor</title> |
|
1319 |
- |
|
1320 |
-<para>Option: <command>extensions.torbutton.block_cache</command></para> |
|
1321 |
- |
|
1322 |
-<para>This setting |
|
1323 |
-causes Torbutton to set <ulink |
|
1324 |
-url="http://kb.mozillazine.org/Browser.cache.memory.enable">browser.cache.memory.enable</ulink>, |
|
1325 |
-<ulink |
|
1326 |
-url="http://kb.mozillazine.org/Browser.cache.disk.enable">browser.cache.disk.enable</ulink> and |
|
1327 |
-<ulink |
|
1328 |
-url="http://kb.mozillazine.org/Network.http.use-cache">network.http.use-cache</ulink> to false during tor usage. |
|
1329 |
-</para> |
|
1330 |
-<para> |
|
1331 |
-This setting helps to satisfy the <link |
|
1332 |
-linkend="state">State Separation</link> and <link |
|
1333 |
-linkend="disk">Disk Avoidance</link> requirements. |
|
1334 |
-</para> |
|
1335 |
- |
|
1336 |
-</sect2> |
|
1337 |
-<sect2> |
|
1338 |
- <title>Clear Cookies on Tor Toggle</title> |
|
1339 |
- |
|
1340 |
-<para>Option: <command>extensions.torbutton.clear_cookies</command> |
|
1341 |
- </para> |
|
1342 |
- |
|
1343 |
-<para> |
|
1344 |
- |
|
1345 |
-This setting causes Torbutton to call <ulink |
|
1346 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsICookieManager.html#method_removeAll">nsICookieManager.removeAll()</ulink> on |
|
1347 |
-every Tor toggle. In addition, this sets <ulink |
|
1348 |
-url="http://kb.mozillazine.org/Network.cookie.lifetimePolicy">network.cookie.lifetimePolicy</ulink> |
|
1349 |
-to 2 for Tor usage, which causes all cookies to be demoted to session cookies, |
|
1350 |
-which prevents them from being written to disk. |
|
1351 |
- |
|
1352 |
-</para> |
|
1353 |
-<para> |
|
1354 |
-This setting helps to satisfy the <link |
|
1355 |
-linkend="state">State Separation</link> and <link |
|
1356 |
-linkend="disk">Disk Avoidance</link> requirements. |
|
1357 |
-</para> |
|
1358 |
- |
|
1359 |
-</sect2> |
|
1360 |
-<sect2> |
|
1361 |
- |
|
1362 |
- <title>Store Non-Tor cookies in a protected jar</title> |
|
1363 |
- |
|
1364 |
-<para>Option: <command>extensions.torbutton.cookie_jars</command> |
|
1365 |
- </para> |
|
1366 |
- |
|
1367 |
-<para> |
|
1368 |
- |
|
1369 |
-This setting causes Torbutton to use <ulink |
|
1370 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js">@stanford.edu/cookie-jar-selector;2</ulink> to store |
|
1371 |
-non-tor cookies in a cookie jar during Tor usage, and clear the Tor cookies |
|
1372 |
-before restoring the jar. |
|
1373 |
-</para> |
|
1374 |
-<para> |
|
1375 |
-This setting also sets <ulink |
|
1376 |
-url="http://kb.mozillazine.org/Network.cookie.lifetimePolicy">network.cookie.lifetimePolicy</ulink> |
|
1377 |
-to 2 for Tor usage, which causes all cookies to be demoted to session cookies, |
|
1378 |
-which prevents them from being written to disk. |
|
1379 |
- |
|
1380 |
-</para> |
|
1381 |
- |
|
1382 |
-<para> |
|
1383 |
-This setting helps to satisfy the <link |
|
1384 |
-linkend="state">State Separation</link> and <link |
|
1385 |
-linkend="disk">Disk Avoidance</link> requirements. |
|
1386 |
-</para> |
|
1387 |
- |
|
1388 |
- |
|
1389 |
-</sect2> |
|
1390 |
-<sect2> |
|
1391 |
- |
|
1392 |
- <title>Store both Non-Tor and Tor cookies in a protected jar (dangerous)</title> |
|
1393 |
- |
|
1394 |
-<para>Option: <command>extensions.torbutton.dual_cookie_jars</command> |
|
1395 |
- </para> |
|
1396 |
- |
|
1397 |
-<para> |
|
1398 |
- |
|
1399 |
-This setting causes Torbutton to use <ulink |
|
1400 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js">@stanford.edu/cookie-jar-selector;2</ulink> to store |
|
1401 |
-both Tor and Non-Tor cookies into protected jars. |
|
1402 |
-</para> |
|
1403 |
- |
|
1404 |
-<para> |
|
1405 |
-This setting helps to satisfy the <link |
|
1406 |
-linkend="state">State Separation</link> requirement. |
|
1407 |
-</para> |
|
1408 |
- |
|
1409 |
- |
|
1410 |
-</sect2> |
|
1411 |
- |
|
1412 |
- |
|
1413 |
-<sect2> |
|
1414 |
- |
|
1415 |
- <title>Manage My Own Cookies (dangerous)</title> |
|
1416 |
- |
|
1417 |
-<para>Options: None</para> |
|
1418 |
-<para>This setting disables all Torbutton cookie handling by setting the above |
|
1419 |
-cookie prefs all to false.</para> |
|
1420 |
-</sect2> |
|
1421 |
-<sect2> |
|
1422 |
- |
|
1423 |
-<sect2> |
|
1424 |
- <title>Do not write Tor/Non-Tor cookies to disk</title> |
|
1425 |
- <para>Options: |
|
1426 |
- <simplelist> |
|
1427 |
- <member><command>extensions.torbutton.tor_memory_jar</command></member> |
|
1428 |
- <member><command>extensions.torbutton.nontor_memory_jar</command></member> |
|
1429 |
- </simplelist> |
|
1430 |
- </para> |
|
1431 |
- |
|
1432 |
-<para> |
|
1433 |
-These settings (contributed by arno) cause Torbutton to set <ulink |
|
1434 |
-url="http://kb.mozillazine.org/Network.cookie.lifetimePolicy">network.cookie.lifetimePolicy</ulink> |
|
1435 |
-to 2 during the appropriate Tor state, and to store cookies acquired in that |
|
1436 |
-state into a Javascript |
|
1437 |
-<ulink |
|
1438 |
-url="http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Guide:Processing_XML_with_E4X">E4X</ulink> |
|
1439 |
-object as opposed to writing them to disk. |
|
1440 |
-</para> |
|
1441 |
- |
|
1442 |
-<para> |
|
1443 |
-This allows Torbutton to provide an option to preserve a user's |
|
1444 |
-cookies while still satisfying the <link linkend="disk">Disk Avoidance</link> |
|
1445 |
-requirement. |
|
1446 |
-</para> |
|
1447 |
-</sect2> |
|
1448 |
- |
|
1449 |
- |
|
1450 |
- <title>Disable DOM Storage during Tor usage (crucial)</title> |
|
1451 |
- |
|
1452 |
-<para>Option: <command>extensions.torbutton.disable_domstorage</command> |
|
1453 |
- </para> |
|
1454 |
- |
|
1455 |
-<para> |
|
1456 |
- |
|
1457 |
-This setting causes Torbutton to toggle <command>dom.storage.enabled</command> during Tor |
|
1458 |
-usage to prevent |
|
1459 |
-<ulink |
|
1460 |
- url="http://developer.mozilla.org/en/docs/DOM:Storage">DOM Storage</ulink> from |
|
1461 |
- being used to store persistent information across Tor states.</para> |
|
1462 |
-<para> |
|
1463 |
-This setting helps to satisfy the <link |
|
1464 |
-linkend="state">State Separation</link> requirement. |
|
1465 |
-</para> |
|
1466 |
- |
|
1467 |
-</sect2> |
|
1468 |
- |
|
1469 |
-<sect2> |
|
1470 |
- <title>Clear HTTP Auth on Tor Toggle (recommended)</title> |
|
1471 |
-<para>Option: <command>extensions.torbutton.clear_http_auth</command> |
|
1472 |
- </para> |
|
1473 |
- |
|
1474 |
-<para> |
|
1475 |
-This setting causes Torbutton to call <ulink |
|
1476 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIHttpAuthManager.html#method_clearAll">nsIHttpAuthManager.clearAll()</ulink> |
|
1477 |
-every time Tor is toggled. |
|
1478 |
-</para> |
|
1479 |
- |
|
1480 |
-<para> |
|
1481 |
-This setting helps to satisfy the <link |
|
1482 |
-linkend="state">State Separation</link> requirement. |
|
1483 |
-</para> |
|
1484 |
-</sect2> |
|
1485 |
- |
|
1486 |
-<sect2> |
|
1487 |
- |
|
1488 |
- <title>Clear cookies on Tor/Non-Tor shutdown</title> |
|
1489 |
- |
|
1490 |
-<para>Option: <command>extensions.torbutton.shutdown_method</command> |
|
1491 |
- </para> |
|
1492 |
- |
|
1493 |
-<para> This option variable can actually take 3 values: 0, 1, and 2. 0 means no |
|
1494 |
-cookie clearing, 1 means clear only during Tor-enabled shutdown, and 2 means |
|
1495 |
-clear for both Tor and Non-Tor shutdown. When set to 1 or 2, Torbutton listens |
|
1496 |
-for the <ulink |
|
1497 |
-url="http://developer.mozilla.org/en/docs/Observer_Notifications#Application_shutdown">quit-application-granted</ulink> event in |
|
1498 |
-<function>torbutton_uninstall_observer()</function> and use <ulink |
|
1499 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js">@stanford.edu/cookie-jar-selector;2</ulink> |
|
1500 |
-to clear out all cookies and all cookie jars upon shutdown. </para> |
|
1501 |
-<para> |
|
1502 |
-This setting helps to satisfy the <link |
|
1503 |
-linkend="state">State Separation</link> requirement. |
|
1504 |
-</para> |
|
1505 |
- |
|
1506 |
- |
|
1507 |
-</sect2> |
|
1508 |
-<sect2> |
|
1509 |
- |
|
1510 |
- <title>Reload cookie jar/clear cookies on Firefox crash</title> |
|
1511 |
- <para>Options: |
|
1512 |
- <simplelist> |
|
1513 |
- <member><command>extensions.torbutton.reload_crashed_jar</command></member> |
|
1514 |
- <member><command>extensions.torbutton.crashed</command></member> |
|
1515 |
- </simplelist> |
|
1516 |
- </para> |
|
1517 |
- |
|
1518 |
- <para>This is no longer a user visible option, and is enabled by default. In |
|
1519 |
-the event of a crash, the Torbutton <ulink |
|
1520 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/crash-observer.js">components/crash-observer.js</ulink> |
|
1521 |
- component will notify the Chrome (via the |
|
1522 |
- <command>extensions.torbutton.crashed</command> pref and a <ulink |
|
1523 |
-url="http://www.xulplanet.com/references/xpcomref/ifaces/nsIPrefBranch2.html#method_addObserver">pref |
|
1524 |
-observer</ulink> in |
|
1525 |
-the chrome that listens for this update), and Torbutton will load the |
|
1526 |
- correct jar for the current Tor state via the <ulink |
|
1527 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js">@stanford.edu/cookie-jar-selector;2</ulink> |
|
1528 |
- component.</para> |
|
1529 |
- |
|
1530 |
-<para> |
|
1531 |
-This setting helps to satisfy the <link |
|
1532 |
-linkend="state">State Separation</link> requirement in the event of Firefox |
|
1533 |
-crashes. |
|
1534 |
-</para> |
|
1535 |
- |
|
1536 |
-</sect2> |
|
1537 |
- |
|
1538 |
- |
|
1539 |
-<sect2> |
|
1540 |
- <title>On crash recovery or session restored startup, restore via: Tor, Non-Tor</title> |
|
1541 |
- <para>Options: |
|
1542 |
- <simplelist> |
|
1543 |
- <member><command>extensions.torbutton.restore_tor</command></member> |
|
1544 |
- <member><command>extensions.torbutton.crashed</command></member> |
|
1545 |
- </simplelist> |
|
1546 |
- </para> |
|
1547 |
- |
|
1548 |
- <para>This option works with the Torbutton <ulink |
|
1549 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/crash-observer.js">crash-observer.js</ulink> |
|
1550 |
- to set the Tor state after a crash is detected (via the |
|
1551 |
- <command>extensions.torbutton.crashed</command> pref)</para> |
|
1552 |
-<para> |
|
1553 |
- |
|
1554 |
-Since the Tor state after a Firefox crash is unknown/indeterminate, this |
|
1555 |
-setting helps to satisfy the <link linkend="state">State Separation</link> |
|
1556 |
-requirement in the event of Firefox crashes by ensuring all cookies, |
|
1557 |
-settings and saved sessions are reloaded from a fixed Tor state. |
|
1558 |
- |
|
1559 |
-</para> |
|
1560 |
-</sect2> |
|
1561 |
- |
|
1562 |
-<sect2> |
|
1563 |
- <title>On normal startup, set state to: Tor, Non-Tor, Shutdown State</title> |
|
1564 |
- |
|
1565 |
- <para>Options: |
|
1566 |
- <simplelist> |
|
1567 |
- <member><command>extensions.torbutton.startup_state</command></member> |
|
1568 |
- <member><command>extensions.torbutton.noncrashed</command></member> |
|
1569 |
- </simplelist> |
|
1570 |
- </para> |
|
1571 |
- |
|
1572 |
- <para>This option also works with the Torbutton <ulink |
|
1573 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/crash-observer.js">crash-observer.js</ulink> |
|
1574 |
- to set the Tor state after a normal startup is detected (via the |
|
1575 |
- <command>extensions.torbutton.noncrashed</command> pref)</para> |
|
1576 |
- |
|
1577 |
-</sect2> |
|
1578 |
- |
|
1579 |
-<sect2> |
|
1580 |
- <title>Prevent session store from saving Non-Tor/Tor-loaded tabs</title> |
|
1581 |
- |
|
1582 |
- <para>Options: |
|
1583 |
- <simplelist> |
|
1584 |
- <member><command>extensions.torbutton.nonontor_sessionstore</command></member> |
|
1585 |
- <member><command>extensions.torbutton.notor_sessionstore</command></member> |
|
1586 |
- </simplelist> |
|
1587 |
- </para> |
|
1588 |
- |
|
1589 |
- <para>If these options are enabled, the <ulink |
|
1590 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/nsSessionStore3.js">replacement nsSessionStore.js</ulink> |
|
1591 |
- component checks the <command>__tb_tor_fetched</command> tag of tabs before writing them |
|
1592 |
- out. If the tag is from a blocked Tor state, the tab is not written to disk. |
|
1593 |
- </para> |
|
1594 |
-<para> |
|
1595 |
-This setting helps to satisfy the <link linkend="disk">Disk Avoidance</link> |
|
1596 |
-requirement, and also helps to satisfy the <link |
|
1597 |
-linkend="state">State Separation</link> requirement in the event of Firefox |
|
1598 |
-crashes. |
|
1599 |
- |
|
1600 |
-</para> |
|
1601 |
- |
|
1602 |
-</sect2> |
|
1603 |
- |
|
1604 |
-<sect2> |
|
1605 |
- |
|
1606 |
- <title>Set user agent during Tor usage (crucial)</title> |
|
1607 |
- <para>Options: |
|
1608 |
- <simplelist> |
|
1609 |
- <member><command>extensions.torbutton.set_uagent</command></member> |
|
1610 |
- <member><command>extensions.torbutton.oscpu_override</command></member> |
|
1611 |
- <member><command>extensions.torbutton.platform_override</command></member> |
|
1612 |
- <member><command>extensions.torbutton.productsub_override</command></member> |
|
1613 |
- <member><command>extensions.torbutton.appname_override</command></member> |
|
1614 |
- <member><command>extensions.torbutton.appversion_override</command></member> |
|
1615 |
- <member><command>extensions.torbutton.useragent_override</command></member> |
|
1616 |
- <member><command>extensions.torbutton.useragent_vendor</command></member> |
|
1617 |
- <member><command>extensions.torbutton.useragent_vendorSub</command></member> |
|
1618 |
- </simplelist> |
|
1619 |
- </para> |
|
1620 |
- |
|
1621 |
-<para>On face, user agent switching appears to be straight-forward in Firefox. |
|
1622 |
-It provides several options for controlling the browser user agent string: |
|
1623 |
-<command>general.appname.override</command>, |
|
1624 |
-<command>general.appversion.override</command>, |
|
1625 |
-<command>general.platform.override</command>, |
|
1626 |
-<command>general.useragent.override</command>, |
|
1627 |
-<command>general.useragent.vendor</command>, and |
|
1628 |
-<command>general.useragent.vendorSub</command>. If |
|
1629 |
-the Torbutton preference <command>extensions.torbutton.set_uagent</command> is |
|
1630 |
-true, Torbutton copies all of the other above prefs into their corresponding |
|
1631 |
-browser preferences during Tor usage.</para> |
|
1632 |
- |
|
1633 |
-<para>However, this is not the whole story. Additionally, even with the above |
|
1634 |
-prefs set, the <command>oscpu</command>, <command>buildID</command>, and <command>productSub</command> fields of the |
|
1635 |
-<ulink |
|
1636 |
-url="http://developer.mozilla.org/en/docs/DOM:window.navigator">navigator</ulink> object are not changed appropriately by the above prefs. |
|
1637 |
-Javascript hooks implemented in <ulink |
|
1638 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/jshooks.js">chrome/content/jshooks.js</ulink> are installed as part of the |
|
1639 |
-same mechanism that hooks the date object. |
|
1640 |
-</para> |
|
1641 |
- |
|
1642 |
-<para> |
|
1643 |
- |
|
1644 |
-It also turns out that it is possible to detect the original Firefox version |
|
1645 |
-by <ulink url="http://0x000000.com/index.php?i=523&bin=1000001011">inspecting |
|
1646 |
-certain resource:// files</ulink>. These cases are handled by Torbutton's |
|
1647 |
-<link linkend="contentpolicy">content policy</link>. |
|
1648 |
- |
|
1649 |
-</para> |
|
1650 |
- |
|
1651 |
- |
|
1652 |
-<para> |
|
1653 |
-This setting helps to satisfy the <link |
|
1654 |
-linkend="setpreservation">Anonymity Set Preservation</link> requirement. |
|
1655 |
-</para> |
|
1656 |
- |
|
1657 |
- |
|
1658 |
-</sect2> |
|
1659 |
-<sect2> |
|
1660 |
- |
|
1661 |
- <title>Spoof US English Browser</title> |
|
1662 |
-<para>Options: |
|
1663 |
-<simplelist> |
|
1664 |
- <member><command>extensions.torbutton.spoof_english</command></member> |
|
1665 |
- <member><command>extensions.torbutton.spoof_charset</command></member> |
|
1666 |
- <member><command>extensions.torbutton.spoof_language</command></member> |
|
1667 |
-</simplelist> |
|
1668 |
-</para> |
|
1669 |
- |
|
1670 |
-<para> This option causes Torbutton to set |
|
1671 |
-<command>general.useragent.locale</command>, |
|
1672 |
-<command>intl.accept_charsets</command> and |
|
1673 |
-<command>intl.accept_languages</command> to the value specified in |
|
1674 |
-<command>extensions.torbutton.spoof_locale</command>, |
|
1675 |
-<command>extensions.torbutton.spoof_charset</command> and |
|
1676 |
-<command>extensions.torbutton.spoof_language</command> during Tor usage. </para> |
|
1677 |
-<para> |
|
1678 |
-This setting helps to satisfy the <link |
|
1679 |
-linkend="setpreservation">Anonymity Set Preservation</link> and <link |
|
1680 |
-linkend="location">Location Neutrality</link> requirements. |
|
1681 |
-</para> |
|
1682 |
- |
|
1683 |
-</sect2> |
|
1684 |
-<sect2> |
|
1685 |
- |
|
1686 |
- <title>Don't send referrer during Tor Usage</title> |
|
1687 |
- |
|
1688 |
-<para>Option: <command>extensions.torbutton.disable_referer</command> |
|
1689 |
-</para> |
|
1690 |
- |
|
1691 |
-<para> |
|
1692 |
-This option causes Torbutton to set <ulink |
|
1693 |
-url="http://kb.mozillazine.org/Network.http.sendSecureXSiteReferrer">network.http.sendSecureXSiteReferrer</ulink> and |
|
1694 |
-<ulink |
|
1695 |
-url="http://kb.mozillazine.org/Network.http.sendRefererHeader">network.http.sendRefererHeader</ulink> during Tor usage.</para> |
|
1696 |
- |
|
1697 |
-<para> |
|
1698 |
-This setting also does not directly satisfy any Torbutton requirement, but |
|
1699 |
-some may desire to mask their referrer for general privacy concerns. |
|
1700 |
-</para> |
|
1701 |
-</sect2> |
|
1702 |
- |
|
1703 |
-<sect2> |
|
1704 |
- |
|
1705 |
- <title>Store SSL/CA Certs in separate jars for Tor/Non-Tor (recommended)</title> |
|
1706 |
- |
|
1707 |
-<para>Options: |
|
1708 |
-<simplelist> |
|
1709 |
- <member><command>extensions.torbutton.jar_certs</command></member> |
|
1710 |
- <member><command>extensions.torbutton.jar_ca_certs</command></member> |
|
1711 |
-</simplelist> |
|
1712 |
-</para> |
|
1713 |
-<para> |
|
1714 |
- |
|
1715 |
-These settings govern if Torbutton attempts to isolate the user's SSL |
|
1716 |
-certificates into separate jars for each Tor state. This isolation is |
|
1717 |
-implemented in <function>torbutton_jar_certs()</function> in <ulink |
|
1718 |
-url="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js">chrome/content/torbutton.js</ulink>, |
|
1719 |
-which calls <function>torbutton_jar_cert_type()</function> and |
|
1720 |
-<function>torbutton_unjar_cert_type()</function> for each certificate type in |
|
1721 |
-the <ulink |
|
1722 |
-url="http://www.xulplanet.com/references/xpcomref/comps/c_securitynsscertcache1.html">@mozilla.org/security/nsscertcache;1</ulink>. |
|
1723 |
-Certificates are deleted from and imported to the <ulink |
|
1724 |
-url="http://www.xulplanet.com/references/xpcomref/comps/c_securityx509certdb1.html">@mozilla.org/security/x509certdb;1</ulink>. |
|
1725 |
-</para> |
|
1726 |
- |
|
1727 |
-<para> |
|
1728 |
-The first time this pref is used, a backup of the user's certificates is |
|
1729 |
-created in their profile directory under the name |
|
1730 |
-<filename>cert8.db.bak</filename>. This file can be copied back to |
|
1731 |
-<filename>cert8.db</filename> to fully restore the original state of the |
|
1732 |
-user's certificates in the event of any error. |
|
1733 |
-</para> |
|
1734 |
- |
|
1735 |
-<para> |
|
1736 |
-Since exit nodes and malicious sites can insert content elements sourced to |
|
1737 |
-specific SSL sites to query if a user has a certain certificate, |
|
1738 |
-this setting helps to satisfy the <link linkend="state">State |
|
1739 |
-Separation</link> requirement of Torbutton. Unfortunately, <ulink |
|
1740 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=435159">Firefox Bug |
|
1741 |
-435159</ulink> prevents it from functioning correctly in the event of rapid Tor toggle, so it |
|
1742 |
-is currently not exposed via the preferences UI. |
|
1743 |
- |
|
1744 |
-</para> |
|
1745 |
- |
|
1746 |
-</sect2> |
|
1747 |
-</sect1> |
|
1748 |
- |
|
1749 |
-<sect1 id="FirefoxBugs"> |
|
1750 |
- <title>Relevant Firefox Bugs</title> |
|
1751 |
- <para> |
|
1752 |
- |
|
1753 |
- </para> |
|
1754 |
- <sect2 id="FirefoxSecurity"> |
|
1755 |
- <title>Bugs impacting security</title> |
|
1756 |
- <para> |
|
1757 |
- |
|
1758 |
-Torbutton has to work around a number of Firefox bugs that impact its |
|
1759 |
-security. Most of these are mentioned elsewhere in this document, but they |
|
1760 |
-have also been gathered here for reference. Several of these have fixes in |
|
1761 |
-Firefox3.0/trunk, but are listed because they still have not been backported |
|
1762 |
-to FF2.0. In order of decreasing severity, they are: |
|
1763 |
- |
|
1764 |
- </para> |
|
1765 |
- <orderedlist> |
|
1766 |
- |
|
1767 |
- <listitem><ulink |
|
1768 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=392274">Bug 392274 - Timezone |
|
1769 |
-config/chrome API</ulink> |
|
1770 |
- <para> |
|
1771 |
-The lack of a config or API to configure the timezone requires Torbutton to |
|
1772 |
-<link linkend="jshooks">insert client content window javascript</link> to hook |
|
1773 |
-the Date object. Additionally, a way to <ulink |
|
1774 |
-url="http://pseudo-flaw.net/tor/torbutton/unmask-date.html">remove the Date |
|
1775 |
-hooks</ulink> was discovered by Greg Fleischer. Worse, on Firefox 3, |
|
1776 |
-javascript sandboxing prevents most of the javascript hooks from being |
|
1777 |
-installed, including the Date hooks. On Windows and Linux, you can set the TZ |
|
1778 |
-environment variable to "UTC" as a workaround. Firefox will obey this |
|
1779 |
-environment variable for your Timezone on those platforms, but on Windows this |
|
1780 |
-does not take effect until browser restart. |
|
1781 |
- </para> |
|
1782 |
- </listitem> |
|
1783 |
- |
|
1784 |
- <listitem><ulink |
|
1785 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=436250">Bug 436250 - Livemarks can't be |
|
1786 |
-disabled at runtime</ulink> |
|
1787 |
- <para> |
|
1788 |
- |
|
1789 |
-The RSS Feed based "Livemarks"/"Live Bookmarks" update frequency is controlled |
|
1790 |
-by the pref <command>browser.bookmarks.livemark_refresh_seconds</command>. |
|
1791 |
-However, changing this preference does not cancel any pending timers, which |
|
1792 |
-means that at least one livemarks pref fetch will happen over Tor, and once |
|
1793 |
-this pref is set to disable livemarks for Tor, changing it back will never |
|
1794 |
-cause the service to start back up again. |
|
1795 |
- |
|
1796 |
- </para> |
|
1797 |
- </listitem> |
|
1798 |
- |
|
1799 |
- <listitem><ulink |
|
1800 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=435159">Bug 435159 - |
|
1801 |
-nsNSSCertificateDB::DeleteCertificate has race conditions</ulink> |
|
1802 |
- <para> |
|
1803 |
- |
|
1804 |
-In Torbutton 1.2.0rc1, code was added to attempt to isolate SSL certificates |
|
1805 |
-the user has installed. Unfortunately, the method call to delete a certificate |
|
1806 |
-from the current certificate database acts lazily: it only sets a variable |
|
1807 |
-that marks a cert for deletion later, and it is not cleared if that |
|
1808 |
-certificate is re-added. This means that if the Tor state is toggled quickly, |
|
1809 |
-that certificate could remain present until it is re-inserted (causing an |
|
1810 |
-error dialog), and worse, it would still be deleted after that. The lack of |
|
1811 |
-this functionality is considered a Torbutton security bug because cert |
|
1812 |
-isolation is considered a <link linkend="state">State Separation</link> |
|
1813 |
-feature. |
|
1814 |
- |
|
1815 |
- </para> |
|
1816 |
- </listitem> |
|
1817 |
- |
|
1818 |
- <listitem><ulink |
|
1819 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=409737">Bug 409737 - |
|
1820 |
-javascript.enabled and docShell.allowJavascript do not disable all event |
|
1821 |
-handlers</ulink> |
|
1822 |
- <para> |
|
1823 |
- |
|
1824 |
-This bug allows pages to execute javascript via addEventListener and perhaps |
|
1825 |
-other callbacks. In order to prevent this bug from enabling an attacker to |
|
1826 |
-break the <link linkend="isolation">Network Isolation</link> requirement, |
|
1827 |
-Torbutton 1.1.13 began blocking popups and history manipulation from different |
|
1828 |
-Tor states. So long as there are no ways to open popups or redirect the user |
|
1829 |
-to a new page, the <link linkend="contentpolicy">Torbutton content |
|
1830 |
-policy</link> should block Javascript network access. However, if there are |
|
1831 |
-ways to open popups or perform redirects such that Torbutton cannot block |
|
1832 |
-them, pages may still have free reign to break that requirement and reveal a |
|
1833 |
-user's original IP address. |
|
1834 |
- |
|
1835 |
- </para> |
|
1836 |
- </listitem> |
|
1837 |
- |
|
1838 |
- |
|
1839 |
- <listitem><ulink |
|
1840 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=405652">Bug 405652 - In the |
|
1841 |
-TLS ClientHello message the gmt_unix_time is incorrect</ulink> |
|
1842 |
- <para> |
|
1843 |
- |
|
1844 |
-It turns out that Firefox's SSL implementation sends the machine uptime as the |
|
1845 |
-current time. This essentially is a unique identifier that can be used for |
|
1846 |
-the duration of your machine uptime. The issue has been fixed in Firefox 3.0, |
|
1847 |
-but it has as of yet not been backported to 2.0. |
|
1848 |
- |
|
1849 |
- </para> |
|
1850 |
- </listitem> |
|
1851 |
- <listitem><ulink |
|
1852 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=143220">Bug 143220 - Script can get the value of a file control, including the path</ulink> |
|
1853 |
- <para> |
|
1854 |
- |
|
1855 |
-Javascript can query the .value field of file input dialogs to retrieve |
|
1856 |
-username and sometimes hostname/workgroup information. This is obviously very |
|
1857 |
-dangerous for people who are attempting to submit files anonymously via |
|
1858 |
-webforms (ie whistleblowers and anonymous publishers). It is also fixed in |
|
1859 |
-Firefox 3.0, but has not yet been backported to 2.0. |
|
1860 |
- |
|
1861 |
- </para> |
|
1862 |
- </listitem> |
|
1863 |
- <listitem><ulink url="https://bugzilla.mozilla.org/show_bug.cgi?id=418119">Bug 418119 - nsIContentPolicy not called for external DTDs of XML documents</ulink> |
|
1864 |
- <para> |
|
1865 |
- |
|
1866 |
-XML documents can source chrome and resource URLs in their DTDs without a call |
|
1867 |
-to nsIContentPolicy::shouldLoad. Enumerating chrome URLs gives websites and |
|
1868 |
-exit nodes a lot of information. They can use it to probe for vulnerable |
|
1869 |
-versions of extensions, and can also use it to build an <link |
|
1870 |
-linkend="fingerprinting">identifier for tracking purposes</link>. This bug |
|
1871 |
-makes it impossible for extensions such as Adblock and Torbutton to prevent |
|
1872 |
-chrome inspection and enumeration. There is no workaround for this bug as of |
|
1873 |
-yet. |
|
1874 |
- |
|
1875 |
- </para> |
|
1876 |
- </listitem> |
|
1877 |
- |
|
1878 |
- </orderedlist> |
|
1879 |
- </sect2> |
|
1880 |
- <sect2 id="FirefoxWishlist"> |
|
1881 |
- <title>Bugs blocking functionality</title> |
|
1882 |
- <para> |
|
1883 |
-The following bugs impact Torbutton and similar extensions' functionality. |
|
1884 |
- </para> |
|
1885 |
- |
|
1886 |
- <orderedlist> |
|
1887 |
- <listitem><ulink |
|
1888 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=439384">Bug 439384 - |
|
1889 |
-"profile-do-change" event does not cause cookie table reload</ulink> |
|
1890 |
- <para> |
|
1891 |
- |
|
1892 |
-In Firefox 3, the change to the new sqlite database for cookie storage has a |
|
1893 |
-bug that prevents Torbutton's cookie jaring from working properly. The |
|
1894 |
-"profile-do-change" observer event no longer properly causes either a sync or |
|
1895 |
-reload of the cookie database from disk after it is copied into place. |
|
1896 |
-Torbutton currently works around this by issuing the SQLLite queries manually |
|
1897 |
-to store and rebuild the cookie database. |
|
1898 |
- |
|
1899 |
- </para> |
|
1900 |
- </listitem> |
|
1901 |
- <listitem><ulink |
|
1902 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=417869">Bug 417869 - |
|
1903 |
-Browser context is difficult to obtain from many XPCOM callbacks</ulink> |
|
1904 |
- <para> |
|
1905 |
- |
|
1906 |
-It is difficult to determine which tabbrowser many XPCOM callbacks originate |
|
1907 |
-from, and in some cases absolutely no context information is provided at all. |
|
1908 |
-While this doesn't have much of an effect on Torbutton, it does make writing |
|
1909 |
-extensions that would like to do per-tab settings and content filters (such as |
|
1910 |
-FoxyProxy) difficult to impossible to implement securely. |
|
1911 |
- |
|
1912 |
- </para> |
|
1913 |
- </listitem> |
|
1914 |
- <listitem><ulink |
|
1915 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=418321">Bug 418321 - |
|
1916 |
-Components do not expose disk interfaces</ulink> |
|
1917 |
- <para> |
|
1918 |
- |
|
1919 |
-Several components currently provide no way of reimplementing their disk |
|
1920 |
-access to easily satisfy Torbutton's <link linkend="disk">Disk |
|
1921 |
-Avoidance</link> requirements. Workarounds exist, but they are <link |
|
1922 |
-linkend="sessionstore">clunky</link>, and |
|
1923 |
-some of them involve disabling functionality during Tor usage. |
|
1924 |
- |
|
1925 |
- </para> |
|
1926 |
- </listitem> |
|
1927 |
- |
|
1928 |
- </orderedlist> |
|
1929 |
- </sect2> |
|
1930 |
- <sect2 id="FirefoxMiscBugs"> |
|
1931 |
- <title>Low Priority Bugs</title> |
|
1932 |
- <para> |
|
1933 |
-The following bugs have an effect upon Torbutton, but are superseded by more |
|
1934 |
-practical and more easily fixable variant bugs above; or have stable, simple |
|
1935 |
-workarounds. |
|
1936 |
- </para> |
|
1937 |
- |
|
1938 |
- <orderedlist> |
|
1939 |
- <listitem><ulink |
|
1940 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=435151">Bug 435151 - XPCSafeJSObjectWrapper breaks evalInSandbox</ulink> |
|
1941 |
- <para> |
|
1942 |
- |
|
1943 |
-Under Firefox 3, the XPCSafeJSObjectWrapper breaks when you try to use |
|
1944 |
-constructors of classes defined from within the scope of the sandbox, among |
|
1945 |
-other things. This prevents Torbutton from applying the Timezone hooks under |
|
1946 |
-Firefox 3, but a better solution for Torbutton's specific date hooking needs |
|
1947 |
-would be a fix for the above mentioned Bug 392274. Of course, many more |
|
1948 |
-extensions may be interested in the sandbox hooking functionality working |
|
1949 |
-properly though. |
|
1950 |
- |
|
1951 |
- </para> |
|
1952 |
- </listitem> |
|
1953 |
- <listitem><ulink |
|
1954 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=437014">Bug 437014 - |
|
1955 |
-nsIContentPolicy::shouldLoad no longer called for favicons</ulink> |
|
1956 |
- <para> |
|
1957 |
- |
|
1958 |
-Firefox 3.0 stopped calling the shouldLoad call of content policy for favicon |
|
1959 |
-loads. Torbutton had relied on this call to block favicon loads for opposite |
|
1960 |
-Tor states. The workaround it employs for Firefox 3 is to cancel the request |
|
1961 |
-when it arrives in the <command>torbutton_http_observer</command> used for |
|
1962 |
-blocking full page plugin loads. This seems to work just fine, but is a bit |
|
1963 |
-dirty. |
|
1964 |
- |
|
1965 |
- </para> |
|
1966 |
- </listitem> |
|
1967 |
- <listitem><ulink |
|
1968 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=437016">Bug 437016 - |
|
1969 |
-nsIContentPolicy::shouldLoad not called for livemarks</ulink> |
|
1970 |
- <para> |
|
1971 |
- |
|
1972 |
-An alternative fix for the livemarks bug above would be to block livemarks |
|
1973 |
-fetches from the content policy. Unfortunately shouldLoad is not called for |
|
1974 |
-livemarks fetches. |
|
1975 |
- |
|
1976 |
- </para> |
|
1977 |
- </listitem> |
|
1978 |
- <listitem><ulink |
|
1979 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=418986">Bug 418986 - window.screen |
|
1980 |
-provides a large amount of identifiable information</ulink> |
|
1981 |
- <para> |
|
1982 |
- |
|
1983 |
-As <link linkend="fingerprinting">mentioned above</link>, a large amount of |
|
1984 |
-information is available from <ulink |
|
1985 |
-url="http://developer.mozilla.org/en/docs/DOM:window.screen">window.screen</ulink>. |
|
1986 |
-Currently, there is no way to obscure this information without Javascript |
|
1987 |
-hooking. This bug is a feature request to provide some other method to change |
|
1988 |
-these values. |
|
1989 |
- |
|
1990 |
- </para> |
|
1991 |
- </listitem> |
|
1992 |
- |
|
1993 |
- <listitem><ulink |
|
1994 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=309524">Bug 309524</ulink> |
|
1995 |
-and <ulink url="https://bugzilla.mozilla.org/show_bug.cgi?id=380556">Bug |
|
1996 |
-380556</ulink> - nsIContentPolicy::shouldProcess is not called. |
|
1997 |
- <para> |
|
1998 |
- |
|
1999 |
-This is a call that would be useful to develop a better workaround for the |
|
2000 |
-allowPlugins issue above. If the content policy were called before a URL was |
|
2001 |
-handed over to a plugin or helper app, it would make the workaround for the |
|
2002 |
-above allowPlugins bug a lot cleaner. Obviously this bug is not as severe as |
|
2003 |
-the others though, but it might be nice to have this API as a backup. |
|
2004 |
- |
|
2005 |
- </para> |
|
2006 |
- </listitem> |
|
2007 |
- |
|
2008 |
- <listitem><ulink |
|
2009 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=401296">Bug 401296 - docShell.allowPlugins |
|
2010 |
-not honored for direct links</ulink> (Perhaps subset of <ulink |
|
2011 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=282106">Bug 282106</ulink>?) |
|
2012 |
- <para> |
|
2013 |
- |
|
2014 |
-Similar to the javascript plugin disabling attribute, the plugin disabling |
|
2015 |
-attribute is also not perfect — it is ignored for direct links to plugin |
|
2016 |
-handled content, as well as meta-refreshes to plugin handled content. This |
|
2017 |
-requires Torbutton to listen to a number of different http events to intercept |
|
2018 |
-plugin-related mime type URLs and cancel their requests. Again, since plugins |
|
2019 |
-are quite horrible about obeying proxy settings, loading a plugin pretty much |
|
2020 |
-ensures a way to break the <link linkend="isolation">Network Isolation</link> |
|
2021 |
-requirement and reveal a user's original IP address. Torbutton's code to |
|
2022 |
-perform this workaround has been subverted at least once already by Kyle |
|
2023 |
-Williams. |
|
2024 |
- |
|
2025 |
- </para> |
|
2026 |
- </listitem> |
|
2027 |
- |
|
2028 |
- <listitem><ulink |
|
2029 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=418983">Bug 41893 - Scoping |
|
2030 |
-issues with window.__defineGetter__()</ulink> |
|
2031 |
- <para> |
|
2032 |
- |
|
2033 |
-For some reason, defining getters off of window seems to mess with the |
|
2034 |
-implicit window scoping in some documents. There is a workaround for this bug, |
|
2035 |
-so it is barely relevant. It would be far more useful to eliminate the need |
|
2036 |
-for Javascript hooking in the first place by addressing the above bugs. This |
|
2037 |
-bug is just listed for completeness. |
|
2038 |
- |
|
2039 |
- </para> |
|
2040 |
- </listitem> |
|
2041 |
- |
|
2042 |
- |
|
2043 |
- <listitem><ulink |
|
2044 |
-url="https://bugzilla.mozilla.org/show_bug.cgi?id=419598">Bug 419598 - 'var |
|
2045 |
-Date' is deletable</ulink> |
|
2046 |
- <para> |
|
2047 |
- |
|
2048 |
-Based on Page 62 of the <ulink |
|
2049 |
-url="http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf">ECMA-262 |
|
2050 |
-Javascript spec</ulink>, it seems like it should be possible to do something |
|
2051 |
-like the following to prevent the Date object from being unmasked: |
|
2052 |
-<screen> |
|
2053 |
-with(window) { |
|
2054 |
- var Date = fakeDate; |
|
2055 |
- var otherVariable = 42; |
|
2056 |
-} |
|
2057 |
- |
|
2058 |
-delete window.Date; // Should fail. Instead succeeds, revealing original Date. |
|
2059 |
-delete window.otherVariable; // Fails, leaving window.otherVariable set to 42. |
|
2060 |
-</screen> |
|
2061 |
- |
|
2062 |
-From the ECMA-262 spec: |
|
2063 |
- |
|
2064 |
-<blockquote> |
|
2065 |
-If the variable statement occurs inside a FunctionDeclaration, the variables |
|
2066 |
-are defined with function-local scope in that function, as described in |
|
2067 |
-s10.1.3. Otherwise, they are defined with global scope (that is, they are |
|
2068 |
-created as members of the global object, as described in 10.1.3) using |
|
2069 |
-property attributes { DontDelete }. Variables are created when the execution |
|
2070 |
-scope is entered. A Block does not define a new execution scope. Only Program |
|
2071 |
-and FunctionDeclaration produce a new scope. Variables are initialized to |
|
2072 |
-undefined when created. A variable with an Initialiser is assigned the value |
|
2073 |
-of its AssignmentExpression when the VariableStatement is executed, not when |
|
2074 |
-the variable is created. |
|
2075 |
-</blockquote> |
|
2076 |
- |
|
2077 |
-In fact, this is exactly how the with statement with a variable declaration |
|
2078 |
-behaves <emphasis>for all other variables other than ones that shadow system |
|
2079 |
-variables</emphasis>. Some variables (such as |
|
2080 |
-<command>window.screen</command>, and <command>window.history</command>) can't |
|
2081 |
-even be shadowed in this way, and give an error about lacking a setter. If |
|
2082 |
-such shadowing were possible, it would greatly simplify the Javascript hooking |
|
2083 |
-code, which currently relies on undocumented semantics of |
|
2084 |
-<command>__proto__</command> to copy the original values in the event of a |
|
2085 |
-delete. This <command>__proto__</command> hack unfortunately does not work for |
|
2086 |
-the Date object though. |
|
2087 |
- |
|
2088 |
- </para> |
|
2089 |
- </listitem> |
|
2090 |
- |
|
2091 |
- </orderedlist> |
|
2092 |
- </sect2> |
|
2093 |
-</sect1> |
|
2094 |
- |
|
2095 |
-<sect1 id="TestPlan"> |
|
2096 |
- <title>Testing</title> |
|
2097 |
- <para> |
|
2098 |
- |
|
2099 |
-The purpose of this section is to cover all the known ways that Tor browser |
|
2100 |
-security can be subverted from a testing and penetration perspective. The hope |
|
2101 |
-is that it will be useful both for creating a "Tor Safety Check" |
|
2102 |
-page, and for developing novel tests and actively attacking Torbutton with the |
|
2103 |
-goal of finding vulnerabilities in either it or the Mozilla components, |
|
2104 |
-interfaces and settings upon which it relies. |
|
2105 |
- |
|
2106 |
- </para> |
|
2107 |
- <sect2 id="Categories"> |
|
2108 |
- <title>Single state testing</title> |
|
2109 |
- <para> |
|
2110 |
-The following tests can be run from a single web page in one visit without |
|
2111 |
-toggling Tor state or requiring user interaction. Currently they exist as their |
|
2112 |
-own individual tests, but conceivably a single "Tor Safety Check" |
|
2113 |
-page can be devised that contains all of these attacks. |
|
2114 |
-All of these tests are currently known to pass, but that does not mean that |
|
2115 |
-consolidating them into an easy to run test page is pointless. Torbutton is a |
|
2116 |
-complicated piece of software. During development, changes to one component |
|
2117 |
-can affect a whole slough of unrelated features. Having easy-to-verify |
|
2118 |
-comprehensive test pages would make it much easier to fix other issues as they |
|
2119 |
-present themselves without introducing regressions. |
|
2120 |
- |
|
2121 |
- </para> |
|
2122 |
- <sect3> |
|
2123 |
- <title>Java and Plugin Decloaking</title> |
|
2124 |
- <para> |
|
2125 |
-As <link linkend="plugins">mentioned above</link>, Java and plugins <ulink |
|
2126 |
-url="http://java.sun.com/j2se/1.5.0/docs/api/java/net/class-use/NetworkInterface.html">can query</ulink> the <ulink |
|
2127 |
-url="http://www.rgagnon.com/javadetails/java-0095.html">local IP |
|
2128 |
-address</ulink> and report it back to the |
|
2129 |
-remote site. They can also <ulink url="http://metasploit.com/research/misc/decloak/index.htm">bypass proxy settings</ulink> and directly connect to a |
|
2130 |
-remote site without Tor. Every browser plugin we have tested with Firefox has |
|
2131 |
-some form of network capability, and every one ignores proxy settings or worse - only |
|
2132 |
-partially obeys them. This includes but is not limited to: |
|
2133 |
-QuickTime, Windows Media Player, RealPlayer, mplayerplug-in, AcroRead, and |
|
2134 |
-Flash. In addition, |
|
2135 |
-<ulink url="http://www.janusvm.com/goldy/pdf/">issues have been |
|
2136 |
-discovered</ulink> with the browsers handling of |
|
2137 |
-<ulink url="https://bugzilla.mozilla.org/show_bug.cgi?id=401296">direct links to plugin-handled |
|
2138 |
-content</ulink> as well as meta-refreshes to plugin content. To make matters |
|
2139 |
-worse, <ulink |
|
2140 |
-url="http://www.janusvm.com/goldy/side-channels/side-channels.html">externally |
|
2141 |
-handled mime types and urls</ulink> can also cause direct non-Tor connections |
|
2142 |
-as well. |
|
2143 |
- </para> |
|
2144 |
- </sect3> |
|
2145 |
- <sect3> |
|
2146 |
- <title>History Disclosure attacks</title> |
|
2147 |
- <para> |
|
2148 |
-The browser's history can also be queried by a remote site to inspect for |
|
2149 |
-Google queries, visits to sites that contain usernames in the URLs, or |
|
2150 |
-other anonymity set reducing information. This can be done by either |
|
2151 |
-<ulink url="http://gemal.dk/browserspy/css.html">Javascript</ulink>, or by |
|
2152 |
-<ulink url="http://ha.ckers.org/weird/CSS-history.cgi">CSS</ulink> without any scripting involved. |
|
2153 |
- |
|
2154 |
- </para> |
|
2155 |
- </sect3> |
|
2156 |
- <sect3> |
|
2157 |
- <title>User agent, extension, resolution and OS information</title> |
|
2158 |
- <para> |
|
2159 |
- |
|
2160 |
-As mentioned above, these properties can be combined to greatly reduce |
|
2161 |
-anonymity set and even build a potentially <link |
|
2162 |
-linkend="fingerprinting">globally unique identifier</link> for |
|
2163 |
-users. <ulink |
|
2164 |
-url="http://0x000000.com/index.php?i=520&bin=1000001000">Examples of this |
|
2165 |
-in the wild</ulink> rely on <ulink url="http://gemal.dk/browserspy/basic.html">user agent and OS |
|
2166 |
-information</ulink> as well as <ulink |
|
2167 |
-url="http://pseudo-flaw.net/content/tor/torbutton/">chrome disclosure |
|
2168 |
-information</ulink>. |
|
2169 |
- |
|
2170 |
- </para> |
|
2171 |
- </sect3> |
|
2172 |
- <sect3> |
|
2173 |
- <title>Timezone and Location Information</title> |
|
2174 |
- <para> |
|
2175 |
-<ulink url="http://gemal.dk/browserspy/date.html">Time and Timezone</ulink> |
|
2176 |
-should be obscured to be GMT-only, and by the browser should present itself |
|
2177 |
-with an US English locale. |
|
2178 |
- </para> |
|
2179 |
- </sect3> |
|
2180 |
- </sect2> |
|
2181 |
- <sect2> |
|
2182 |
- <title>Multi-state testing</title> |
|
2183 |
- <para> |
|
2184 |
- |
|
2185 |
-The tests in this section are geared towards a page that would instruct the |
|
2186 |
-user to toggle their Tor state after the fetch and perform some operations: |
|
2187 |
-mouseovers, stray clicks, and potentially reloads. |
|
2188 |
- |
|
2189 |
- </para> |
|
2190 |
- <sect3> |
|
2191 |
- <title>Cookies and Cache Correlation</title> |
|
2192 |
- <para> |
|
2193 |
-The most obvious test is to set a cookie, ask the user to toggle tor, and then |
|
2194 |
-have them reload the page. The cookie should no longer be set if they are |
|
2195 |
-using the default Torbutton settings. In addition, it is possible to leverage |
|
2196 |
-the cache to <ulink |
|
2197 |
-url="http://crypto.stanford.edu/sameorigin/safecachetest.html">store unique |
|
2198 |
-identifiers</ulink>. The default settings of Torbutton should also protect |
|
2199 |
-against these from persisting across Tor Toggle. |
|
2200 |
- |
|
2201 |
- </para> |
|
2202 |
- </sect3> |
|
2203 |
- <sect3> |
|
2204 |
- <title>Javascript timers and event handlers</title> |
|
2205 |
- <para> |
|
2206 |
- |
|
2207 |
-Javascript can set timers and register event handlers in the hopes of fetching |
|
2208 |
-URLs after the user has toggled Torbutton. |
|
2209 |
- </para> |
|
2210 |
- </sect3> |
|
2211 |
- <sect3> |
|
2212 |
- <title>CSS Popups and non-script Dynamic Content</title> |
|
2213 |
- <para> |
|
2214 |
- |
|
2215 |
-Even if Javascript is disabled, CSS is still able to |
|
2216 |
-<ulink url="http://www.tjkdesign.com/articles/css%20pop%20ups/">create popup-like |
|
2217 |
-windows</ulink> |
|
2218 |
-via the 'onmouseover' CSS attribute, which can cause arbitrary browser |
|
2219 |
-activity as soon as the mouse enters into the content window. It is also |
|
2220 |
-possible for meta-refresh tags to set timers long enough to make it likely |
|
2221 |
-that the user has toggled Tor before fetching content. |
|
2222 |
- |
|
2223 |
- </para> |
|
2224 |
- </sect3> |
|
2225 |
- </sect2> |
|
2226 |
- <sect2> |
|
2227 |
- <title>Active testing (aka How to Hack Torbutton)</title> |
|
2228 |
- <para> |
|
2229 |
- |
|
2230 |
-The idea behind active testing is to discover vulnerabilities in Torbutton to |
|
2231 |
-bypass proxy settings, run script in an opposite Tor state, store unique |
|
2232 |
-identifiers, leak location information, or otherwise violate <link |
|
2233 |
-linkend="requirements">its requirements</link>. Torbutton has ventured out |
|
2234 |
-into a strange and new security landscape. It depends on Firefox mechanisms |
|
2235 |
-that haven't necessarily been audited for security, certainly not for the |
|
2236 |
-threat model that Torbutton seeks to address. As such, it and the interfaces |
|
2237 |
-it depends upon still need a 'trial by fire' typical of new technologies. This |
|
2238 |
-section of the document was written with the intention of making that period |
|
2239 |
-as fast as possible. Please help us get through this period by considering |
|
2240 |
-these attacks, playing with them, and reporting what you find (and potentially |
|
2241 |
-submitting the test cases back to be run in the standard batch of Torbutton |
|
2242 |
-tests. |
|
2243 |
- |
|
2244 |
- </para> |
|
2245 |
- <sect3> |
|
2246 |
- <title>Some suggested vectors to investigate</title> |
|
2247 |
- <para> |
|
2248 |
- <itemizedlist> |
|
2249 |
- <listitem>Strange ways to register Javascript <ulink |
|
2250 |
-url="http://en.wikipedia.org/wiki/DOM_Events">events</ulink> and <ulink |
|
2251 |
-url="http://www.devshed.com/c/a/JavaScript/Using-Timers-in-JavaScript/">timeouts</ulink> should |
|
2252 |
-be verified to actually be ineffective after Tor has been toggled.</listitem> |
|
2253 |
- <listitem>Other ways to cause Javascript to be executed after |
|
2254 |
-<command>javascript.enabled</command> has been toggled off.</listitem> |
|
2255 |
- <listitem>Odd ways to attempt to load plugins. Kyle Williams has had |
|
2256 |
-<ulink url="http://www.janusvm.com/goldy/pdf/">some |
|
2257 |
-success</ulink> with direct loads/meta-refreshes of plugin-handled URLs.</listitem> |
|
2258 |
- <listitem>The Date and Timezone hooks should be verified to work with |
|
2259 |
-crazy combinations of iframes, nested iframes, iframes in frames, frames in |
|
2260 |
-iframes, and popups being loaded and |
|
2261 |
-reloaded in rapid succession, and/or from one another. Think race conditions and deep, |
|
2262 |
-parallel nesting, involving iframes from both <ulink |
|
2263 |
-url="http://en.wikipedia.org/wiki/Same_origin_policy">same-origin and |
|
2264 |
-non-same-origin</ulink> domains.</listitem> |
|
2265 |
- <listitem>In addition, there may be alternate ways and other |
|
2266 |
-methods to query the timezone, or otherwise use some of the Date object's |
|
2267 |
-methods in combination to deduce the timezone offset. Of course, the author |
|
2268 |
-tried his best to cover all the methods he could foresee, but it's always good |
|
2269 |
-to have another set of eyes try it out.</listitem> |
|
2270 |
- <listitem>Similarly, is there any way to confuse the <link |
|
2271 |
-linkend="contentpolicy">content policy</link> |
|
2272 |
-mentioned above to cause it to allow certain types of page fetches? For |
|
2273 |
-example, it was recently discovered that favicons are not fetched by the |
|
2274 |
-content, but the chrome itself, hence the content policy did not look up the |
|
2275 |
-correct window to determine the current Tor tag for the favicon fetch. Are |
|
2276 |
-there other things that can do this? Popups? Bookmarklets? Active bookmarks? </listitem> |
|
2277 |
- <listitem>Alternate ways to store and fetch unique identifiers. For example, <ulink |
|
2278 |
-url="http://developer.mozilla.org/en/docs/DOM:Storage">DOM Storage</ulink> |
|
2279 |
-caught us off guard. |
|
2280 |
-It was |
|
2281 |
-also discovered by <ulink url="http://pseudo-flaw.net">Gregory |
|
2282 |
-Fleischer</ulink> that <ulink |
|
2283 |
-url="http://pseudo-flaw.net/content/tor/torbutton/">content window access to |
|
2284 |
-chrome</ulink> can be used to build <link linkend="fingerprinting">unique |
|
2285 |
-identifiers</link>. |
|
2286 |
-Are there any other |
|
2287 |
-arcane or experimental ways that Firefox provides to create and store unique |
|
2288 |
-identifiers? Or perhaps unique identifiers can be queried or derived from |
|
2289 |
-properties of the machine/browser that Javascript has access to? How unique |
|
2290 |
-can these identifiers be? |
|
2291 |
- </listitem> |
|
2292 |
- <listitem>Is it possible to get the browser to write some history to disk |
|
2293 |
-(aside from swap) that can be retrieved later? By default, Torbutton should |
|
2294 |
-write no history, cookie, or other browsing activity information to the |
|
2295 |
-harddisk.</listitem> |
|
2296 |
- <listitem>Do popup windows make it easier to break any of the above |
|
2297 |
-behavior? Are javascript events still canceled in popups? What about recursive |
|
2298 |
-popups from Javascript, data, and other funky URL types? What about CSS |
|
2299 |
-popups? Are they still blocked after Tor is toggled?</listitem> |
|
2300 |
- <listitem>Chrome-escalation attacks. The interaction between the |
|
2301 |
-Torbutton chrome Javascript and the client content window javascript is pretty |
|
2302 |
-well-defined and carefully constructed, but perhaps there is a way to smuggle |
|
2303 |
-javascript back in a return value, or otherwise inject network-loaded |
|
2304 |
-javascript into the chrome (and thus gain complete control of the browser). |
|
2305 |
-</listitem> |
|
2306 |
-</itemizedlist> |
|
2307 |
- |
|
2308 |
- </para> |
|
2309 |
- </sect3> |
|
2310 |
- </sect2> |
|
2311 |
-</sect1> |
|
2312 |
-</article> |
... | ... |
@@ -1,1281 +0,0 @@ |
1 |
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> |
|
2 |
-<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Torbutton Design Documentation</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="article" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="design"></a>Torbutton Design Documentation</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Mike</span> <span class="surname">Perry</span></h3><div class="affiliation"><div class="address"><p><code class="email"><<a class="email" href="mailto:mikeperry.fscked/org">mikeperry.fscked/org</a>></code></p></div></div></div></div><div><p class="pubdate">July 4 2008</p></div></div><hr /></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="#id2970568">1. Introduction</a></span></dt><dd><dl><dt><span class="sect2"><a href="#adversary">1.1. Adversary Model</a></span></dt><dt><span class="sect2"><a href="#requirements">1.2. Torbutton Requirements</a></span></dt><dt><span class="sect2"><a href="#layout">1.3. Extension Layout</a></span></dt></dl></dd><dt><span class="sect1"><a href="#id2980698">2. Components</a></span></dt><dd><dl><dt><span class="sect2"><a href="#id3000781">2.1. Hooked Components</a></span></dt><dt><span class="sect2"><a href="#id2988472">2.2. New Components</a></span></dt></dl></dd><dt><span class="sect1"><a href="#id2981568">3. Chrome</a></span></dt><dd><dl><dt><span class="sect2"><a href="#browseroverlay">3.1. Browser Overlay - torbutton.xul</a></span></dt><dt><span class="sect2"><a href="#id2984229">3.2. Preferences Window - preferences.xul</a></span></dt><dt><span class="sect2"><a href="#id2988730">3.3. Other Windows</a></span></dt></dl></dd><dt><span class="sect1"><a href="#id2986171">4. Toggle Code Path</a></span></dt><dd><dl><dt><span class="sect2"><a href="#id2990959">4.1. Button Click</a></span></dt><dt><span class="sect2"><a href="#id2984082">4.2. Proxy Update</a></span></dt><dt><span class="sect2"><a href="#id3001325">4.3. Settings Update</a></span></dt></dl></dd><dt><span class="sect1"><a href="#id2984248">5. Description of Options</a></span></dt><dd><dl><dt><span class="sect2"><a href="#id2980079">5.1. Test Settings</a></span></dt><dt><span class="sect2"><a href="#plugins">5.2. Disable plugins on Tor Usage (crucial)</a></span></dt><dt><span class="sect2"><a href="#id2978605">5.3. Isolate Dynamic Content to Tor State (crucial)</a></span></dt><dt><span class="sect2"><a href="#jshooks">5.4. Hook Dangerous Javascript (crucial)</a></span></dt><dt><span class="sect2"><a href="#id2992126">5.5. Resize windows to multiples of 50px during Tor usage (recommended)</a></span></dt><dt><span class="sect2"><a href="#id3004184">5.6. Disable Updates During Tor (recommended)</a></span></dt><dt><span class="sect2"><a href="#id2997514">5.7. Disable Search Suggestions during Tor (recommended)</a></span></dt><dt><span class="sect2"><a href="#id3000110">5.8. Block Tor/Non-Tor access to network from file:// urls (recommended)</a></span></dt><dt><span class="sect2"><a href="#id2998307">5.9. Close all Tor/Non-Tor tabs and windows on toggle (optional)</a></span></dt><dt><span class="sect2"><a href="#id2996566">5.10. Isolate Access to History navigation to Tor state (crucial)</a></span></dt><dt><span class="sect2"><a href="#id2998342">5.11. History Access Settings</a></span></dt><dt><span class="sect2"><a href="#id2957709">5.12. Clear History During Tor Toggle (optional)</a></span></dt><dt><span class="sect2"><a href="#id2962370">5.13. Block Password+Form saving during Tor/Non-Tor</a></span></dt><dt><span class="sect2"><a href="#id2962437">5.14. Block Tor disk cache and clear all cache on Tor Toggle</a></span></dt><dt><span class="sect2"><a href="#id2962492">5.15. Block disk and memory cache during Tor</a></span></dt><dt><span class="sect2"><a href="#id2962549">5.16. Clear Cookies on Tor Toggle</a></span></dt><dt><span class="sect2"><a href="#id2962603">5.17. Store Non-Tor cookies in a protected jar</a></span></dt><dt><span class="sect2"><a href="#id2962662">5.18. Store both Non-Tor and Tor cookies in a protected jar (dangerous)</a></span></dt><dt><span class="sect2"><a href="#id2962702">5.19. Manage My Own Cookies (dangerous)</a></span></dt><dt><span class="sect2"><a href="#id2962718">5.20. Disable DOM Storage during Tor usage (crucial)</a></span></dt><dt><span class="sect2"><a href="#id2962826">5.21. Clear HTTP Auth on Tor Toggle (recommended)</a></span></dt><dt><span class="sect2"><a href="#id3005721">5.22. Clear cookies on Tor/Non-Tor shutdown</a></span></dt><dt><span class="sect2"><a href="#id3005775">5.23. Reload cookie jar/clear cookies on Firefox crash</a></span></dt><dt><span class="sect2"><a href="#id3005850">5.24. On crash recovery or session restored startup, restore via: Tor, Non-Tor</a></span></dt><dt><span class="sect2"><a href="#id3005910">5.25. On normal startup, set state to: Tor, Non-Tor, Shutdown State</a></span></dt><dt><span class="sect2"><a href="#id3005958">5.26. Prevent session store from saving Non-Tor/Tor-loaded tabs</a></span></dt><dt><span class="sect2"><a href="#id3006023">5.27. Set user agent during Tor usage (crucial)</a></span></dt><dt><span class="sect2"><a href="#id3006210">5.28. Spoof US English Browser</a></span></dt><dt><span class="sect2"><a href="#id3006297">5.29. Don't send referrer during Tor Usage</a></span></dt><dt><span class="sect2"><a href="#id3006338">5.30. Store SSL/CA Certs in separate jars for Tor/Non-Tor (recommended)</a></span></dt></dl></dd><dt><span class="sect1"><a href="#FirefoxBugs">6. Relevant Firefox Bugs</a></span></dt><dd><dl><dt><span class="sect2"><a href="#FirefoxSecurity">6.1. Bugs impacting security</a></span></dt><dt><span class="sect2"><a href="#FirefoxWishlist">6.2. Bugs blocking functionality</a></span></dt><dt><span class="sect2"><a href="#FirefoxMiscBugs">6.3. Low Priority Bugs</a></span></dt></dl></dd><dt><span class="sect1"><a href="#TestPlan">7. Testing</a></span></dt><dd><dl><dt><span class="sect2"><a href="#Categories">7.1. Single state testing</a></span></dt><dt><span class="sect2"><a href="#id3007257">7.2. Multi-state testing</a></span></dt><dt><span class="sect2"><a href="#id3007328">7.3. Active testing (aka How to Hack Torbutton)</a></span></dt></dl></dd></dl></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id2970568"></a>1. Introduction</h2></div></div></div><p> |
|
3 |
- |
|
4 |
-This document describes the goals, operation, and testing procedures of the |
|
5 |
-Torbutton Firefox extension. It is current as of Torbutton 1.2.0rc5. |
|
6 |
- |
|
7 |
- </p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="adversary"></a>1.1. Adversary Model</h3></div></div></div><p> |
|
8 |
- |
|
9 |
-A Tor web browser adversary has a number of goals, capabilities, and attack |
|
10 |
-types that can be used to guide us towards a set of requirements for the |
|
11 |
-Torbutton extension. Let's start with the goals. |
|
12 |
- |
|
13 |
- </p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id2997298"></a>Adversary Goals</h4></div></div></div><div class="orderedlist"><ol type="1"><li><span class="command"><strong>Bypassing proxy settings</strong></span><p>The adversary's primary goal is direct compromise and bypass of |
|
14 |
-Tor, causing the user to directly connect to an IP of the adversary's |
|
15 |
-choosing.</p></li><li><span class="command"><strong>Correlation of Tor vs Non-Tor Activity</strong></span><p>If direct proxy bypass is not possible, the adversary will likely |
|
16 |
-happily settle for the ability to correlate something a user did via Tor with |
|
17 |
-their non-Tor activity. This can be done with cookies, cache identifiers, |
|
18 |
-javascript events, and even CSS. Sometimes the fact that a user uses Tor may |
|
19 |
-be enough for some authorities.</p></li><li><span class="command"><strong>History disclosure</strong></span><p> |
|
20 |
-The adversary may also be interested in history disclosure: the ability to |
|
21 |
-query a user's history to see if they have issued certain censored search |
|
22 |
-queries, or visited censored sites. |
|
23 |
- </p></li><li><span class="command"><strong>Location information</strong></span><p> |
|
24 |
- |
|
25 |
-Location information such as timezone and locality can be useful for the |
|
26 |
-adversary to determine if a user is in fact originating from one of the |
|
27 |
-regions they are attempting to control, or to zero-in on the geographical |
|
28 |
-location of a particular dissident or whistleblower. |
|
29 |
- |
|
30 |
- </p></li><li><span class="command"><strong>Miscellaneous anonymity set reduction</strong></span><p> |
|
31 |
- |
|
32 |
-Anonymity set reduction is also useful in attempting to zero in on a |
|
33 |
-particular individual. If the dissident or whistleblower is using a rare build |
|
34 |
-of Firefox for an obscure operating system, this can be very useful |
|
35 |
-information for tracking them down, or at least <a class="link" href="#fingerprinting">tracking their activities</a>. |
|
36 |
- |
|
37 |
- </p></li><li><span class="command"><strong>History records and other on-disk |
|
38 |
-information</strong></span><p> |
|
39 |
-In some cases, the adversary may opt for a heavy-handed approach, such as |
|
40 |
-seizing the computers of all Tor users in an area (especially after narrowing |
|
41 |
-the field by the above two pieces of information). History records and cache |
|
42 |
-data are the primary goals here. |
|
43 |
- </p></li></ol></div></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id2970954"></a>Adversary Capabilities - Positioning</h4></div></div></div><p> |
|
44 |
-The adversary can position themselves at a number of different locations in |
|
45 |
-order to execute their attacks. |
|
46 |
- </p><div class="orderedlist"><ol type="1"><li><span class="command"><strong>Exit Node or Upstream Router</strong></span><p> |
|
47 |
-The adversary can run exit nodes, or alternatively, they may control routers |
|
48 |
-upstream of exit nodes. Both of these scenarios have been observed in the |
|
49 |
-wild. |
|
50 |
- </p></li><li><span class="command"><strong>Adservers and/or Malicious Websites</strong></span><p> |
|
51 |
-The adversary can also run websites, or more likely, they can contract out |
|
52 |
-ad space from a number of different adservers and inject content that way. For |
|
53 |
-some users, the adversary may be the adservers themselves. It is not |
|
54 |
-inconceivable that adservers may try to subvert or reduce a user's anonymity |
|
55 |
-through Tor for marketing purposes. |
|
56 |
- </p></li><li><span class="command"><strong>Local Network/ISP/Upstream Router</strong></span><p> |
|
57 |
-The adversary can also inject malicious content at the user's upstream router |
|
58 |
-when they have Tor disabled, in an attempt to correlate their Tor and Non-Tor |
|
59 |
-activity. |
|
60 |
- </p></li><li><span class="command"><strong>Physical Access</strong></span><p> |
|
61 |
-Some users face adversaries with intermittent or constant physical access. |
|
62 |
-Users in Internet cafes, for example, face such a threat. In addition, in |
|
63 |
-countries where simply using tools like Tor is illegal, users may face |
|
64 |
-confiscation of their computer equipment for excessive Tor usage or just |
|
65 |
-general suspicion. |
|
66 |
- </p></li></ol></div></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id2972854"></a>Adversary Capabilities - Attacks</h4></div></div></div><p> |
|
67 |
-The adversary can perform the following attacks from a number of different |
|
68 |
-positions to accomplish various aspects of their goals. |
|
69 |
- </p><div class="orderedlist"><ol type="1"><li><span class="command"><strong>Inserting Javascript</strong></span><p> |
|
70 |
-Javascript allows the adversary the opportunity to accomplish a number of |
|
71 |
-their goals. If not properly disabled, Javascript event handlers and timers |
|
72 |
-can cause the browser to perform network activity after Tor has been disabled, |
|
73 |
-thus allowing the adversary to correlate Tor and Non-Tor activity. Javascript |
|
74 |
-also allows the adversary to execute <a class="ulink" href="http://gemal.dk/browserspy/css.html" target="_top">history disclosure attacks</a>: |
|
75 |
-to query the history via the different attributes of 'visited' links. Finally, |
|
76 |
-Javascript can be used to query the user's timezone via the |
|
77 |
-<code class="function">Date()</code> object, and to reduce the anonymity set by querying |
|
78 |
-the <code class="function">navigator</code> object for operating system, CPU, and user |
|
79 |
-agent information. |
|
80 |
- </p></li><li><span class="command"><strong>Inserting Plugins</strong></span><p> |
|
81 |
- |
|
82 |
-Plugins are abysmal at obeying the proxy settings of the browser. Every plugin |
|
83 |
-capable of performing network activity that the author has |
|
84 |
-investigated is also capable of performing network activity independent of |
|
85 |
-browser proxy settings - and often independent of its own proxy settings. |
|
86 |
-In addition, plugins can be used to store unique identifiers that are more |
|
87 |
-difficult to clear than standard cookies. |
|
88 |
-<a class="ulink" href="http://epic.org/privacy/cookies/flash.html" target="_top">Flash-based |
|
89 |
-cookies</a> fall into this category, but there are likely numerous other |
|
90 |
-examples. |
|
91 |
- |
|
92 |
- </p></li><li><span class="command"><strong>Inserting CSS</strong></span><p> |
|
93 |
- |
|
94 |
-CSS can also be used to correlate Tor and Non-Tor activity, via the usage of |
|
95 |
-<a class="ulink" href="http://www.tjkdesign.com/articles/css%20pop%20ups/" target="_top">CSS |
|
96 |
-popups</a> - essentially CSS-based event handlers that fetch content via |
|
97 |
-CSS's onmouseover attribute. If these popups are allowed to perform network |
|
98 |
-activity in a different Tor state than they were loaded in, they can easily |
|
99 |
-correlate Tor and Non-Tor activity and reveal a user's IP address. In |
|
100 |
-addition, CSS can also be used without Javascript to perform <a class="ulink" href="http://ha.ckers.org/weird/CSS-history.cgi" target="_top">CSS-only history disclosure |
|
101 |
-attacks</a>. |
|
102 |
- </p></li><li><span class="command"><strong>Read and insert cookies</strong></span><p> |
|
103 |
- |
|
104 |
-An adversary in a position to perform MITM content alteration can inject |
|
105 |
-document content elements to both read and inject cookies for |
|
106 |
-arbitrary domains. In fact, many "SSL secured" websites are vulnerable to this |
|
107 |
-sort of <a class="ulink" href="http://seclists.org/bugtraq/2007/Aug/0070.html" target="_top">active |
|
108 |
-sidejacking</a>. |
|
109 |
- |
|
110 |
- </p></li><li><span class="command"><strong>Create arbitrary cached content</strong></span><p> |
|
111 |
- |
|
112 |
-Likewise, the browser cache can also be used to <a class="ulink" href="http://crypto.stanford.edu/sameorigin/safecachetest.html" target="_top">store unique |
|
113 |
-identifiers</a>. Since by default the cache has no same-origin policy, |
|
114 |
-these identifiers can be read by any domain, making them an ideal target for |
|
115 |
-adserver-class adversaries. |
|
116 |
- |
|
117 |
- </p></li><li><a id="fingerprinting"></a><span class="command"><strong>Fingerprint users based on browser |
|
118 |
-attributes</strong></span><p> |
|
119 |
- |
|
120 |
-There is an absurd amount of information available to websites via attributes |
|
121 |
-of the browser. This information can be used to reduce anonymity set, or even |
|
122 |
-<a class="ulink" href="http://0x000000.com/index.php?i=520&bin=1000001000" target="_top">uniquely |
|
123 |
-fingerprint individual users</a>. </p><p> |
|
124 |
-For illustration, let's perform a |
|
125 |
-back-of-the-envelope calculation on the number of anonymity sets for just the |
|
126 |
-resolution information available in the <a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window" target="_top">window</a> and |
|
127 |
-<a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window.screen" target="_top">window.screen</a> |
|
128 |
-objects. Browser window resolution information provides something like |
|
129 |
-(1280-640)*(1024-480)=348160 different anonymity sets. Desktop resolution |
|
130 |
-information contributes about another factor of 5 (for about 5 resolutions in |
|
131 |
-typical use). In addition, the dimensions and position of the desktop taskbar |
|
132 |
-are available, which can reveal hints on OS information. This boosts the count |
|
133 |
-by a factor of 5 (for each of the major desktop taskbars - Windows, OSX, KDE |
|
134 |
-and Gnome, and None). Subtracting the browser content window |
|
135 |
-size from the browser outer window size provide yet more information. |
|
136 |
-Firefox toolbar presence gives about a factor of 8 (3 toolbars on/off give |
|
137 |
-2<sup>3</sup>=8). Interface effects such as titlebar fontsize |
|
138 |
-and window manager settings gives a factor of about 9 (say 3 common font sizes |
|
139 |
-for the titlebar and 3 common sizes for browser GUI element fonts). |
|
140 |
-Multiply this all out, and you have (1280-640)*(1024-480)*5*5*8*9 ~= |
|
141 |
-2<sup>29</sup>, or a 29 bit identifier based on resolution |
|
142 |
-information alone. </p><p> |
|
143 |
- |
|
144 |
-Of course, this space is non-uniform and prone to incremental changes. |
|
145 |
-However, if a bit vector space consisting of the above extracted attributes |
|
146 |
-were used instead of the hash approach from <a class="ulink" href="http://0x000000.com/index.php?i=520&bin=1000001000" target="_top">The Hacker |
|
147 |
-Webzine article above</a>, minor changes in browser window resolution will |
|
148 |
-no longer generate totally new identifiers. |
|
149 |
- |
|
150 |
-</p><p> |
|
151 |
- |
|
152 |
-To add insult to injury, <a class="ulink" href="http://pseudo-flaw.net/content/tor/torbutton/" target="_top">chrome URL disclosure |
|
153 |
-attacks</a> mean that each and every extension on <a class="ulink" href="https://addons.mozilla.org" target="_top">addons.mozilla.org</a> adds another bit |
|
154 |
-to that 2<sup>29</sup>. With hundreds of popular extensions |
|
155 |
-and thousands of extensions total, it is easy to see that this sort of |
|
156 |
-information is an impressively powerful identifier if used properly by a |
|
157 |
-competent and determined adversary such as an ad network. Again, a |
|
158 |
-nearest-neighbor bit vector space approach here would also gracefully handle |
|
159 |
-incremental changes to installed extensions. |
|
160 |
- |
|
161 |
-</p></li><li><span class="command"><strong>Remotely or locally exploit browser and/or |
|
162 |
-OS</strong></span><p> |
|
163 |
-Last, but definitely not least, the adversary can exploit either general |
|
164 |
-browser vulnerabilities, plugin vulnerabilities, or OS vulnerabilities to |
|
165 |
-install malware and surveillance software. An adversary with physical access |
|
166 |
-can perform similar actions. Regrettably, this last attack capability is |
|
167 |
-outside of Torbutton's ability to defend against, but it is worth mentioning |
|
168 |
-for completeness. |
|
169 |
- </p></li></ol></div></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="requirements"></a>1.2. Torbutton Requirements</h3></div></div></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3> |
|
170 |
- |
|
171 |
-Since many settings satisfy multiple requirements, this design document is |
|
172 |
-organized primarily by Torbutton components and settings. However, if you are |
|
173 |
-the type that would rather read the document from the requirements |
|
174 |
-perspective, it is in fact possible to search for each of the following |
|
175 |
-requirement phrases in the text to find the relevant features that help meet |
|
176 |
-that requirement. |
|
177 |
- |
|
178 |
-</div><p> |
|
179 |
- |
|
180 |
-From the above Adversary Model, a number of requirements become clear. |
|
181 |
- |
|
182 |
- </p><div class="orderedlist"><ol type="1"><li><a id="proxy"></a><span class="command"><strong>Proxy Obedience</strong></span><p>The browser |
|
183 |
-MUST NOT bypass Tor proxy settings for any content.</p></li><li><a id="isolation"></a><span class="command"><strong>Network Isolation</strong></span><p>Pages MUST NOT perform any network activity in a Tor state different |
|
184 |
- from the state they were originally loaded in.</p></li><li><a id="state"></a><span class="command"><strong>State Separation</strong></span><p>Browser state (cookies, cache, history, 'DOM storage'), accumulated in |
|
185 |
- one Tor state MUST NOT be accessible via the network in |
|
186 |
- another Tor state.</p></li><li><a id="undiscoverability"></a><span class="command"><strong>Tor Undiscoverability</strong></span><p>With |
|
187 |
-the advent of bridge support in Tor 0.2.0.x, there are now a class of Tor |
|
188 |
-users whose network fingerprint does not obviously betray the fact that they |
|
189 |
-are using Tor. This should extend to the browser as well - Torbutton MUST NOT |
|
190 |
-reveal its presence while Tor is disabled.</p></li><li><a id="disk"></a><span class="command"><strong>Disk Avoidance</strong></span><p>The browser SHOULD NOT write any Tor-related state to disk, or store it |
|
191 |
- in memory beyond the duration of one Tor toggle.</p></li><li><a id="location"></a><span class="command"><strong>Location Neutrality</strong></span><p>The browser SHOULD NOT leak location-specific information, such as |
|
192 |
- timezone or locale via Tor.</p></li><li><a id="setpreservation"></a><span class="command"><strong>Anonymity Set |
|
193 |
-Preservation</strong></span><p>The browser SHOULD NOT leak any other anonymity set reducing information |
|
194 |
- (such as user agent, extension presence, and resolution information) |
|
195 |
-automatically via Tor. The assessment of the attacks above should make it clear |
|
196 |
-that anonymity set reduction is a very powerful method of tracking and |
|
197 |
-eventually identifying anonymous users. |
|
198 |
-</p></li><li><a id="updates"></a><span class="command"><strong>Update Safety</strong></span><p>The browser |
|
199 |
-SHOULD NOT perform unauthenticated updates or upgrades via Tor.</p></li><li><a id="interoperate"></a><span class="command"><strong>Interoperability</strong></span><p>Torbutton SHOULD interoperate with third-party proxy switchers that |
|
200 |
- enable the user to switch between a number of different proxies. It MUST |
|
201 |
- provide full Tor protection in the event a third-party proxy switcher has |
|
202 |
- enabled the Tor proxy settings.</p></li></ol></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="layout"></a>1.3. Extension Layout</h3></div></div></div><p>Firefox extensions consist of two main categories of code: 'Components' and |
|
203 |
-'Chrome'. Components are a fancy name for classes that implement a given |
|
204 |
-interface or interfaces. In Firefox, components <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/creatingcomps.html" target="_top">can be |
|
205 |
-written</a> in C++, |
|
206 |
-Javascript, or a mixture of both. Components have two identifiers: their |
|
207 |
-'<a class="ulink" href="http://www.mozilla.org/projects/xpcom/book/cxc/html/quicktour2.html#1005005" target="_top">Contract |
|
208 |
-ID</a>' (a human readable path-like string), and their '<a class="ulink" href="http://www.mozilla.org/projects/xpcom/book/cxc/html/quicktour2.html#1005329" target="_top">Class |
|
209 |
-ID</a>' (a GUID hex-string). In addition, the interfaces they implement each have a hex |
|
210 |
-'Interface ID'. It is possible to 'hook' system components - to reimplement |
|
211 |
-their interface members with your own wrappers - but only if the rest of the |
|
212 |
-browser refers to the component by its Contract ID. If the browser refers to |
|
213 |
-the component by Class ID, it bypasses your hooks in that use case. |
|
214 |
-Technically, it may be possible to hook Class IDs by unregistering the |
|
215 |
-original component, and then re-registering your own, but this relies on |
|
216 |
-obsolete and deprecated interfaces and has proved to be less than |
|
217 |
-stable.</p><p>'Chrome' is a combination of XML and Javascript used to describe a window. |
|
218 |
-Extensions are allowed to create 'overlays' that are 'bound' to existing XML |
|
219 |
-window definitions, or they can create their own windows. The DTD for this XML |
|
220 |
-is called <a class="ulink" href="http://developer.mozilla.org/en/docs/XUL_Reference" target="_top">XUL</a>.</p></div></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id2980698"></a>2. Components</h2></div></div></div><p> |
|
221 |
- |
|
222 |
-Torbutton installs components for two purposes: hooking existing components to |
|
223 |
-reimplement their interfaces; and creating new components that provide |
|
224 |
-services to other pieces of the extension. |
|
225 |
- |
|
226 |
- </p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3000781"></a>2.1. Hooked Components</h3></div></div></div><p>Torbutton makes extensive use of Contract ID hooking, and implements some |
|
227 |
-of its own standalone components as well. Let's discuss the hooked components |
|
228 |
-first.</p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="sessionstore"></a><a class="ulink" href="http://developer.mozilla.org/en/docs/nsISessionStore" target="_top">@mozilla.org/browser/sessionstore;1</a> - |
|
229 |
-<a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/nsSessionStore2.js" target="_top">components/nsSessionStore2.js</a> |
|
230 |
-and <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/nsSessionStore3.js" target="_top">components/nsSessionStore3.js</a></h4></div></div></div><p>These components address the <a class="link" href="#disk">Disk Avoidance</a> |
|
231 |
-requirements of Torbutton. As stated in the requirements, Torbutton needs to |
|
232 |
-prevent Tor tabs from being written to disk by the Firefox session store for a |
|
233 |
-number of reasons, primary among them is the fact that Firefox can crash at |
|
234 |
-any time, and a restart can cause you to fetch tabs in the incorrect Tor |
|
235 |
-state.</p><p>These components illustrate a complication with Firefox hooking: you can |
|
236 |
-only hook member functions of a class if they are published in an |
|
237 |
-interface that the class implements. Unfortunately, the sessionstore has no |
|
238 |
-published interface that is amenable to disabling the writing out of Tor tabs |
|
239 |
-in specific. As such, Torbutton had to include the <span class="emphasis"><em>entire</em></span> |
|
240 |
-nsSessionStore from both Firefox 2 and Firefox 3, |
|
241 |
-with a couple of modifications to prevent tabs that were loaded with Tor |
|
242 |
-enabled from being written to disk, and some version detection code to |
|
243 |
-determine which component to load. The <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/nsSessionStore3.diff" target="_top">diff against the original session |
|
244 |
-store</a> is included in the SVN repository.</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id2985696"></a><a class="ulink" href="http://lxr.mozilla.org/seamonkey/source/browser/components/sessionstore/src/nsSessionStartup.js" target="_top">@mozilla.org/browser/sessionstartup;1</a> - |
|
245 |
- <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/crash-observer.js" target="_top">components/crash-observer.js</a></h4></div></div></div><p>This component wraps the Firefox Session Startup component that is in |
|
246 |
-charge of <a class="ulink" href="http://developer.mozilla.org/en/docs/Session_store_API" target="_top">restoring saved |
|
247 |
-sessions</a>. The wrapper's only job is to intercept the |
|
248 |
-<code class="function">doRestore()</code> function, which is called by Firefox if it is determined that the |
|
249 |
-browser crashed and the session needs to be restored. The wrapper notifies the |
|
250 |
-Torbutton chrome that the browser crashed by setting the pref |
|
251 |
-<span class="command"><strong>extensions.torbutton.crashed</strong></span>, or that it is a normal |
|
252 |
-startup via the pref <span class="command"><strong>extensions.torbutton.noncrashed</strong></span>. The Torbutton Chrome <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIPrefBranch2.html#method_addObserver" target="_top">listens for a |
|
253 |
-preference change</a> for this value and then does the appropriate cleanup. This |
|
254 |
-includes setting the Tor state to the one the user selected for crash recovery |
|
255 |
-in the preferences window (<span class="command"><strong>extensions.torbutton.restore_tor</strong></span>), and |
|
256 |
-restoring cookies for the corresponding cookie jar, if it exists.</p><p>By performing this notification, this component assists in the |
|
257 |
-<a class="link" href="#proxy">Proxy Obedience</a>, and <a class="link" href="#isolation">Network Isolation</a> requirements. |
|
258 |
-</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id2979678"></a><a class="ulink" href="http://www.xulplanet.com/references/xpcomref/comps/c_browserglobalhistory2.html" target="_top">@mozilla.org/browser/global-history;2</a> |
|
259 |
-- <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/ignore-history.js" target="_top">components/ignore-history.js</a></h4></div></div></div><p>This component was contributed by <a class="ulink" href="http://www.collinjackson.com/" target="_top">Collin Jackson</a> as a method for defeating |
|
260 |
-CSS and Javascript-based methods of history disclosure. The global-history |
|
261 |
-component is what is used by Firefox to determine if a link was visited or not |
|
262 |
-(to apply the appropriate style to the link). By hooking the <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIGlobalHistory2.html#method_isVisited" target="_top">isVisited</a> |
|
263 |
-and <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIGlobalHistory2.html#method_addURI" target="_top">addURI</a> |
|
264 |
-methods, Torbutton is able to selectively prevent history items from being |
|
265 |
-added or being displayed as visited, depending on the Tor state and the user's |
|
266 |
-preferences. |
|
267 |
-</p><p> |
|
268 |
-This component helps satisfy the <a class="link" href="#state">State Separation</a> |
|
269 |
-and <a class="link" href="#disk">Disk Avoidance</a> requirements of Torbutton. |
|
270 |
-</p></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2988472"></a>2.2. New Components</h3></div></div></div><p>Torbutton creates four new components that are used throughout the |
|
271 |
-extension. These components do not hook any interfaces, nor are they used |
|
272 |
-anywhere besides Torbutton itself.</p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id2981164"></a><a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js" target="_top">@stanford.edu/cookie-jar-selector;2 |
|
273 |
-- components/cookie-jar-selector.js</a></h4></div></div></div><p>The cookie jar selector (also based on code from <a class="ulink" href="http://www.collinjackson.com/" target="_top">Collin |
|
274 |
-Jackson</a>) is used by the Torbutton chrome to switch between |
|
275 |
-Tor and Non-Tor cookies. Its operations are simple: sync cookies to disk, then |
|
276 |
-move the current cookies.txt file to the appropriate backup location |
|
277 |
-(cookies-tor.txt or cookies-nontor.txt), and then moving the other cookie jar |
|
278 |
-into place.</p><p> |
|
279 |
-This component helps to address the <a class="link" href="#state">State |
|
280 |
-Isolation</a> requirement of Torbutton. |
|
281 |
-</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id2995031"></a><a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/torbutton-logger.js" target="_top">@torproject.org/torbutton-logger;1 |
|
282 |
-- components/torbutton-logger.js</a></h4></div></div></div><p>The torbutton logger component allows on-the-fly redirection of torbutton |
|
283 |
-logging messages to either Firefox stderr |
|
284 |
-(<span class="command"><strong>extensions.torbutton.logmethod=0</strong></span>), the Javascript error console |
|
285 |
-(<span class="command"><strong>extensions.torbutton.logmethod=1</strong></span>), or the DebugLogger extension (if |
|
286 |
-available - <span class="command"><strong>extensions.torbutton.logmethod=2</strong></span>). It also allows you to |
|
287 |
-change the loglevel on the fly by changing |
|
288 |
-<span class="command"><strong>extensions.torbutton.loglevel</strong></span> (1-5, 1 is most verbose). |
|
289 |
-</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="windowmapper"></a><a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/window-mapper.js" target="_top">@torproject.org/content-window-mapper;1 |
|
290 |
-- components/window-mapper.js</a></h4></div></div></div><p>Torbutton tags Firefox <a class="ulink" href="http://www.xulplanet.com/references/elemref/ref_tabbrowser.html" target="_top">tabs</a> with a special variable that indicates the Tor |
|
291 |
-state the tab was most recently used under to fetch a page. The problem is |
|
292 |
-that for many Firefox events, it is not possible to determine the tab that is |
|
293 |
-actually receiving the event. The Torbutton window mapper allows the Torbutton |
|
294 |
-chrome and other components to look up a <a class="ulink" href="http://www.xulplanet.com/references/elemref/ref_tabbrowser.html" target="_top">browser |
|
295 |
-tab</a> for a given <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIDOMWindow.html" target="_top">HTML content |
|
296 |
-window</a>. It does this by traversing all windows and all browsers, until it |
|
297 |
-finds the browser with the requested <a class="ulink" href="http://www.xulplanet.com/references/elemref/ref_browser.html#prop_contentWindow" target="_top">contentWindow</a> element. Since the content policy |
|
298 |
-and page loading in general can generate hundreds of these lookups, this |
|
299 |
-result is cached inside the component. |
|
300 |
-</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="contentpolicy"></a><a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cssblocker.js" target="_top">@torproject.org/cssblocker;1 |
|
301 |
-- components/cssblocker.js</a></h4></div></div></div><p>This is a key component to Torbutton's security measures. When Tor is |
|
302 |
-toggled, Javascript is disabled, and pages are instructed to stop loading. |
|
303 |
-However, CSS is still able to perform network operations by loading styles for |
|
304 |
-onmouseover events and other operations. In addition, favicons can still be |
|
305 |
-loaded by the browser. The cssblocker component prevents this by implementing |
|
306 |
-and registering an <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIContentPolicy.html" target="_top">nsIContentPolicy</a>. |
|
307 |
-When an nsIContentPolicy is registered, Firefox checks every attempted network |
|
308 |
-request against its <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIContentPolicy.html#method_shouldLoad" target="_top">shouldLoad</a> |
|
309 |
-member function to determine if the load should proceed. In Torbutton's case, |
|
310 |
-the content policy looks up the appropriate browser tab using the <a class="link" href="#windowmapper" title="@torproject.org/content-window-mapper;1 - components/window-mapper.js">window mapper</a>, |
|
311 |
-and checks that tab's load tag against the current Tor state. If the tab was |
|
312 |
-loaded in a different state than the current state, the fetch is denied. |
|
313 |
-Otherwise, it is allowed.</p> This helps to achieve the <a class="link" href="#isolation">Network |
|
314 |
-Isolation</a> requirements of Torbutton. |
|
315 |
- |
|
316 |
-<p>In addition, the content policy also blocks website javascript from |
|
317 |
-<a class="ulink" href="http://pseudo-flaw.net/content/tor/torbutton/" target="_top">querying for |
|
318 |
-versions and existence of extension chrome</a> while Tor is enabled, and |
|
319 |
-also masks the presence of Torbutton to website javascript while Tor is |
|
320 |
-disabled. </p><p> |
|
321 |
- |
|
322 |
-Finally, some of the work that logically belongs to the content policy is |
|
323 |
-instead handled by the <span class="command"><strong>torbutton_http_observer</strong></span> and |
|
324 |
-<span class="command"><strong>torbutton_weblistener</strong></span> in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js" target="_top">torbutton.js</a>. These two objects handle blocking of |
|
325 |
-Firefox 3 favicon loads, popups, and full page plugins, which for whatever |
|
326 |
-reason are not passed to the Firefox content policy itself (see Firefox Bugs |
|
327 |
-<a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=437014" target="_top">437014</a> and |
|
328 |
-<a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=401296" target="_top">401296</a>). |
|
329 |
- |
|
330 |
-</p><p> |
|
331 |
- |
|
332 |
-This helps to fulfill both the <a class="link" href="#setpreservation">Anonymity Set Preservation</a> and the <a class="link" href="#undiscoverability">Tor Undiscoverability</a> requirements of |
|
333 |
-Torbutton.</p></div></div></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id2981568"></a>3. Chrome</h2></div></div></div><p>The chrome is where all the torbutton graphical elements and windows are |
|
334 |
-located. Each window is described as an <a class="ulink" href="http://developer.mozilla.org/en/docs/XUL_Reference" target="_top">XML file</a>, with zero or more Javascript |
|
335 |
-files attached. The scope of these Javascript files is their containing |
|
336 |
-window.</p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="browseroverlay"></a>3.1. Browser Overlay - <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.xul" target="_top">torbutton.xul</a></h3></div></div></div><p>The browser overlay, torbutton.xul, defines the toolbar button, the status |
|
337 |
-bar, and events for toggling the button. The overlay code is in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js" target="_top">chrome/content/torbutton.js</a>. |
|
338 |
-It contains event handlers for preference update, shutdown, upgrade, and |
|
339 |
-location change events.</p><p>The <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/comps/c_docloaderservice1.html" target="_top">location |
|
340 |
-change</a> <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebProgressListener.html" target="_top">webprogress |
|
341 |
-listener</a>, <span class="command"><strong>torbutton_weblistener</strong></span> is perhaps the |
|
342 |
-most important part of the chrome from a security standpoint. It is a <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebProgressListener.html" target="_top">web |
|
343 |
-progress listener</a> that handles |
|
344 |
-receiving an event every time a page load or iframe load occurs. This class |
|
345 |
-eventually calls down to <code class="function">torbutton_update_tags()</code> and |
|
346 |
-<code class="function">torbutton_hookdoc()</code>, which apply the browser Tor load state tags, plugin |
|
347 |
-permissions, and install the Javascript hooks to hook the <a class="ulink" href="http://phrogz.net/objJob/object.asp?id=224" target="_top">Date</a> object and |
|
348 |
-the <a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window.navigator" target="_top">navigator</a> object (for timezone and platform information, |
|
349 |
-respectively).</p><p> |
|
350 |
-The browser overlay helps to satisfy a number of Torbutton requirements. These |
|
351 |
-are better enumerated in each of the Torbutton preferences below. However, |
|
352 |
-there are also a number of Firefox preferences set in |
|
353 |
-<code class="function">torbutton_update_status()</code> that aren't governed by any |
|
354 |
-Torbutton setting. These are: |
|
355 |
-</p><div class="orderedlist"><ol type="1"><li><a class="ulink" href="http://kb.mozillazine.org/Browser.bookmarks.livemark_refresh_seconds" target="_top">browser.bookmarks.livemark_refresh_seconds</a><p> |
|
356 |
-This pref is set in an attempt to disable the fetching of LiveBookmarks via |
|
357 |
-Tor. Since users can potentially collect a large amount of live bookmarks to |
|
358 |
-very personal sites (blogs of friends, wikipedia articles they maintain, |
|
359 |
-comment feeds of their own blog), it is not possible to cleanly isolate these |
|
360 |
-fetches and they are simply disabled during Tor usage. |
|
361 |
-This helps to address the <a class="link" href="#state">State Separation</a> requirement. |
|
362 |
-Unfortunately <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=436250" target="_top">Firefox Bug |
|
363 |
-436250</a> prevents this from |
|
364 |
-functioning completely correctly. |
|
365 |
-</p></li><li><a class="ulink" href="http://kb.mozillazine.org/Network.security.ports.banned" target="_top">network.security.ports.banned</a><p> |
|
366 |
-Torbutton sets this setting to add ports 8123, 8118, 9050 and 9051 (which it |
|
367 |
-reads from <span class="command"><strong>extensions.torbutton.banned_ports</strong></span>) to the list |
|
368 |
-of ports Firefox is forbidden to access. These ports are Polipo, Privoxy, Tor, |
|
369 |
-and the Tor control port, respectively. This is set for both Tor and Non-Tor |
|
370 |
-usage, and prevents websites from attempting to do http fetches from these |
|
371 |
-ports to see if they are open, which addresses the <a class="link" href="#undiscoverability">Tor Undiscoverability</a> requirement. |
|
372 |
- </p></li><li><a class="ulink" href="http://kb.mozillazine.org/Browser.send_pings" target="_top">browser.send_pings</a><p> |
|
373 |
-This setting is currently always disabled. If anyone ever complains saying |
|
374 |
-that they *want* their browser to be able to send ping notifications to a |
|
375 |
-page or arbitrary link, I'll make this a pref or Tor-only. But I'm not holding |
|
376 |
-my breath. I haven't checked if the content policy is called for pings, but if |
|
377 |
-not, this setting helps with meeting the <a class="link" href="#isolation">Network |
|
378 |
-Isolation</a> requirement. |
|
379 |
- </p></li><li><a class="ulink" href="http://kb.mozillazine.org/Browser.safebrowsing.remoteLookups" target="_top">browser.safebrowsing.remoteLookups</a><p> |
|
380 |
-Likewise for this setting. I find it hard to imagine anyone who wants to ask |
|
381 |
-Google in real time if each URL they visit is safe, especially when the list |
|
382 |
-of unsafe URLs is downloaded anyway. This helps fulfill the <a class="link" href="#disk">Disk Avoidance</a> requirement, by preventing your entire |
|
383 |
-browsing history from ending up on Google's disks. |
|
384 |
- </p></li><li><a class="ulink" href="http://kb.mozillazine.org/Browser.safebrowsing.enabled" target="_top">browser.safebrowsing.enabled</a><p> |
|
385 |
-Safebrowsing does <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=360387" target="_top">unauthenticated |
|
386 |
-updates under Firefox 2</a>, so it is disabled during Tor usage. |
|
387 |
-This helps fulfill the <a class="link" href="#updates">Update |
|
388 |
-Safety</a> requirement. Firefox 3 has the fix for that bug, and so |
|
389 |
-safebrowsing updates are enabled during Tor usage. |
|
390 |
- </p></li><li><a class="ulink" href="http://kb.mozillazine.org/Network.protocol-handler.warn-external.%28protocol%29" target="_top">network.protocol-handler.warn-external.(protocol)</a><p> |
|
391 |
-If Tor is enabled, we need to prevent random external applications from |
|
392 |
-launching without at least warning the user. This group of settings only |
|
393 |
-partially accomplishes this, however. Applications can still be launched via |
|
394 |
-plugins. The mechanisms for handling this are described under the "Disable |
|
395 |
-Plugins During Tor Usage" preference. This helps fulfill the <a class="link" href="#proxy">Proxy Obedience</a> requirement, by preventing external |
|
396 |
-applications from accessing network resources at the command of Tor-fetched |
|
397 |
-pages. |
|
398 |
- </p></li></ol></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2984229"></a>3.2. Preferences Window - <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/preferences.xul" target="_top">preferences.xul</a></h3></div></div></div><p>The preferences window of course lays out the Torbutton preferences, with |
|
399 |
-handlers located in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/preferences.js" target="_top">chrome/content/preferences.js</a>.</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2988730"></a>3.3. Other Windows</h3></div></div></div><p>There are additional windows that describe popups for right clicking on |
|
400 |
-the status bar, the toolbutton, and the about page.</p></div></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id2986171"></a>4. Toggle Code Path</h2></div></div></div><p> |
|
401 |
- |
|
402 |
-The act of toggling is connected to <code class="function">torbutton_toggle()</code> |
|
403 |
-via the <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.xul" target="_top">torbutton.xul</a> |
|
404 |
-and <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/popup.xul" target="_top">popup.xul</a> |
|
405 |
-overlay files. Most of the work in the toggling process is present in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js" target="_top">torbutton.js</a> |
|
406 |
- |
|
407 |
-</p><p> |
|
408 |
- |
|
409 |
-Toggling is a 3 stage process: Button Click, Proxy Update, and |
|
410 |
-Settings Update. These stages are reflected in the prefs |
|
411 |
-<span class="command"><strong>extensions.torbutton.tor_enabled</strong></span>, |
|
412 |
-<span class="command"><strong>extensions.torbutton.proxies_applied</strong></span>, and |
|
413 |
-<span class="command"><strong>extensions.torbutton.settings_applied</strong></span>. The reason for the |
|
414 |
-three stage preference update is to ensure immediate enforcement of <a class="link" href="#isolation">Network Isolation</a> via the <a class="link" href="#contentpolicy" title="@torproject.org/cssblocker;1 - components/cssblocker.js">content policy</a>. Since the content window |
|
415 |
-javascript runs on a different thread than the chrome javascript, it is |
|
416 |
-important to properly convey the stages to the content policy to avoid race |
|
417 |
-conditions and leakage, especially with <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=409737" target="_top">Firefox Bug |
|
418 |
-409737</a> unfixed. The content policy does not allow any network activity |
|
419 |
-whatsoever during this three stage transition. |
|
420 |
- |
|
421 |
- </p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2990959"></a>4.1. Button Click</h3></div></div></div><p> |
|
422 |
- |
|
423 |
-This is the first step in the toggling process. When the user clicks the |
|
424 |
-toggle button or the toolbar, <code class="function">torbutton_toggle()</code> is |
|
425 |
-called. This function checks the current Tor status by comparing the current |
|
426 |
-proxy settings to the selected Tor settings, and then sets the proxy settings |
|
427 |
-to the opposite state, and sets the pref |
|
428 |
-<span class="command"><strong>extensions.torbutton.tor_enabled</strong></span> to reflect the new state. |
|
429 |
-It is this proxy pref update that gives notification via the <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIPrefBranch2.html#method_addObserver" target="_top">pref |
|
430 |
-observer</a> |
|
431 |
-<span class="command"><strong>torbutton_unique_pref_observer</strong></span> to perform the rest of the |
|
432 |
-toggle. |
|
433 |
- |
|
434 |
- </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2984082"></a>4.2. Proxy Update</h3></div></div></div><p> |
|
435 |
- |
|
436 |
-When Torbutton receives any proxy change notifications via its |
|
437 |
-<span class="command"><strong>torbutton_unique_pref_observer</strong></span>, it calls |
|
438 |
-<code class="function">torbutton_set_status()</code> which checks against the Tor |
|
439 |
-settings to see if the Tor proxy settings match the current settings. If so, |
|
440 |
-it calls <code class="function">torbutton_update_status()</code>, which determines if |
|
441 |
-the Tor state has actually changed, and sets |
|
442 |
-<span class="command"><strong>extensions.torbutton.proxies_applied</strong></span> to the appropriate Tor |
|
443 |
-state value, and ensures that |
|
444 |
-<span class="command"><strong>extensions.torbutton.tor_enabled</strong></span> is also set to the correct |
|
445 |
-value. This is decoupled from the button click functionalty via the pref |
|
446 |
-observer so that other addons (such as SwitchProxy) can switch the proxy |
|
447 |
-settings between multiple proxies. |
|
448 |
- |
|
449 |
- </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3001325"></a>4.3. Settings Update</h3></div></div></div><p> |
|
450 |
- |
|
451 |
-The next stage is also handled by |
|
452 |
-<code class="function">torbutton_update_status()</code>. This function sets scores of |
|
453 |
-Firefox preferences, saving the original values to prefs under |
|
454 |
-<span class="command"><strong>extensions.torbutton.saved.*</strong></span>, and performs the history |
|
455 |
-clearing, cookie jaring, and ssl certificate jaring work of Torbutton. At the |
|
456 |
-end of its work, it sets |
|
457 |
-<span class="command"><strong>extensions.torbutton.settings_applied</strong></span>, which signifies the |
|
458 |
-completion of the toggle operation to the <a class="link" href="#contentpolicy" title="@torproject.org/cssblocker;1 - components/cssblocker.js">content policy</a>. |
|
459 |
- |
|
460 |
- </p></div></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id2984248"></a>5. Description of Options</h2></div></div></div><p>This section provides a detailed description of Torbutton's options. Each |
|
461 |
-option is presented as the string from the preferences window, a summary, the |
|
462 |
-preferences it touches, and the effect this has on the components, chrome, and |
|
463 |
-browser properties.</p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2980079"></a>5.1. Test Settings</h3></div></div></div><p> |
|
464 |
-This button under the Proxy Settings tab provides a way to verify that the |
|
465 |
-proxy settings are correct, and actually do route through the Tor network. It |
|
466 |
-performs this check by issuing an <a class="ulink" href="http://developer.mozilla.org/en/docs/XMLHttpRequest" target="_top">XMLHTTPRequest</a> |
|
467 |
-for <a class="ulink" href="https://check.torproject.org/?TorButton=True" target="_top">https://check.torproject.org/?Torbutton=True</a>. |
|
468 |
-This is a special page that returns very simple, yet well-formed XHTML that |
|
469 |
-Torbutton can easily inspect for a hidden link with an id of |
|
470 |
-<span class="command"><strong>TorCheckResult</strong></span> and a target of <span class="command"><strong>success</strong></span> |
|
471 |
-or <span class="command"><strong>failure</strong></span> to indicate if the |
|
472 |
-user hit the page from a Tor IP, a non-Tor IP. This check is handled in |
|
473 |
-<code class="function">torbutton_test_settings()</code> in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js" target="_top">torbutton.js</a>. |
|
474 |
-Presenting the results to the user is handled by the <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/preferences.xul" target="_top">preferences |
|
475 |
-window</a> |
|
476 |
-callback <code class="function">torbutton_prefs_test_settings()</code> in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/preferences.js" target="_top">preferences.js</a>. |
|
477 |
- |
|
478 |
- </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="plugins"></a>5.2. Disable plugins on Tor Usage (crucial)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.no_tor_plugins</strong></span></p><p>Enabling this preference causes the above mentioned Torbutton chrome web progress |
|
479 |
- listener <span class="command"><strong>torbutton_weblistener</strong></span> to disable Java via <span class="command"><strong>security.enable_java</strong></span> and to disable |
|
480 |
- plugins via the browser <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIDocShell.html" target="_top">docShell</a> |
|
481 |
- attribute <span class="command"><strong>allowPlugins</strong></span>. These flags are set every time a new window is |
|
482 |
- created (<code class="function">torbutton_tag_new_browser()</code>), every time a web |
|
483 |
-load |
|
484 |
-event occurs |
|
485 |
- (<code class="function">torbutton_update_tags()</code>), and every time the tor state is changed |
|
486 |
- (<code class="function">torbutton_update_status()</code>). As a backup measure, plugins are also |
|
487 |
- prevented from loading by the content policy in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cssblocker.js" target="_top">@torproject.org/cssblocker;1</a> if Tor is |
|
488 |
- enabled and this option is set. |
|
489 |
- </p><p>Even all this turns out to be insufficient if the user directly |
|
490 |
- clicks on a plugin-handled mime-type. <a class="ulink" href="http://www.janusvm.com/goldy/pdf/" target="_top">In this case</a> (and also <a class="ulink" href="http://www.janusvm.com/goldy/side-channels/frames/" target="_top">this |
|
491 |
-one</a>), the browser decides that |
|
492 |
- maybe it should ignore all these other settings and load the plugin anyways, |
|
493 |
- because maybe the user really did want to load it (never mind this same |
|
494 |
- load-style could happen automatically with meta-refresh or any number of |
|
495 |
- other ways..). To handle these cases, Torbutton stores a list of plugin-handled |
|
496 |
- mime-types, and sets the pref |
|
497 |
-<span class="command"><strong>plugin.disable_full_page_plugin_for_types</strong></span> to this list. |
|
498 |
-Additionally, (since nothing can be assumed when relying on Firefox |
|
499 |
-preferences and internals) if it detects a load of one of them from the web progress |
|
500 |
- listener, it cancels the request, tells the associated DOMWindow |
|
501 |
-to stop loading, clears the document, AND throws an exception. Anything short |
|
502 |
-of all this and |
|
503 |
- the plugin managed to find some way to load. |
|
504 |
- </p><p> |
|
505 |
- All this could be avoided, of course, if Firefox would either <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=401296" target="_top">obey |
|
506 |
- allowPlugins</a> for directly visited URLs, or notify its content policy for such |
|
507 |
- loads either <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=309524" target="_top">via</a> <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=380556" target="_top">shouldProcess</a> or shouldLoad. The fact that it does not is |
|
508 |
- not very encouraging. |
|
509 |
- </p><p> |
|
510 |
- |
|
511 |
-Since most plugins completely ignore browser proxy settings, the actions |
|
512 |
-performed by this setting are crucial to satisfying the <a class="link" href="#proxy">Proxy Obedience</a> requirement. |
|
513 |
- |
|
514 |
- </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2978605"></a>5.3. Isolate Dynamic Content to Tor State (crucial)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.isolate_content</strong></span></p><p>Enabling this preference is what enables the <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cssblocker.js" target="_top">@torproject.org/cssblocker;1</a> content policy |
|
515 |
-mentioned above, and causes it to block content load attempts in pages an |
|
516 |
-opposite Tor state from the current state. Freshly loaded <a class="ulink" href="http://www.xulplanet.com/references/elemref/ref_tabbrowser.html" target="_top">browser |
|
517 |
-tabs</a> are tagged |
|
518 |
-with a <span class="command"><strong>__tb_load_state</strong></span> member in |
|
519 |
-<code class="function">torbutton_update_tags()</code> and this |
|
520 |
-value is compared against the current tor state in the content policy.</p><p>It also kills all Javascript in each page loaded under that state by |
|
521 |
-toggling the <span class="command"><strong>allowJavascript</strong></span> <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIDocShell.html" target="_top">docShell</a> property, and issues a |
|
522 |
-<a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebNavigation.html#method_stop" target="_top">webNavigation.stop(webNavigation.STOP_ALL)</a> to each browser tab (the |
|
523 |
-equivalent of hitting the STOP button).</p><p> |
|
524 |
- |
|
525 |
-Unfortunately, <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=409737" target="_top">Firefox bug |
|
526 |
-409737</a> prevents <span class="command"><strong>docShell.allowJavascript</strong></span> from killing |
|
527 |
-all event handlers, and event handlers registered with <a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:element.addEventListener" target="_top">addEventListener()</a> |
|
528 |
-are still able to execute. The <a class="link" href="#contentpolicy" title="@torproject.org/cssblocker;1 - components/cssblocker.js">Torbutton Content |
|
529 |
-Policy</a> should prevent such code from performing network activity within |
|
530 |
-the current tab, but activity that happens via a popup window or via a |
|
531 |
-Javascript redirect can still slip by. For this reason, Torbutton blocks |
|
532 |
-popups by checking for a valid <a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window.opener" target="_top">window.opener</a> |
|
533 |
-attribute in <code class="function">torbutton_check_progress()</code>. If the window |
|
534 |
-has an opener from a different Tor state, its load is blocked. The content |
|
535 |
-policy also takes similar action to prevent Javascript redirects. This also |
|
536 |
-has the side effect/feature of preventing the user from following any links |
|
537 |
-from a page loaded in an opposite Tor state. |
|
538 |
- |
|
539 |
-</p><p> |
|
540 |
-This setting is responsible for satisfying the <a class="link" href="#isolation">Network Isolation</a> requirement. |
|
541 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="jshooks"></a>5.4. Hook Dangerous Javascript (crucial)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.kill_bad_js</strong></span></p><p>This setting enables injection of the <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/jshooks.js" target="_top">Javascript |
|
542 |
-hooking code</a>. Javascript is injected into |
|
543 |
-pages to hook the <a class="ulink" href="http://phrogz.net/objJob/object.asp?id=224" target="_top">Date |
|
544 |
-class</a> to mask your timezone. This is done in the chrome in |
|
545 |
-<code class="function">torbutton_hookdoc()</code>, which is called ultimately by both the |
|
546 |
-<a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIWebProgressListener.html" target="_top">webprogress |
|
547 |
-listener</a> <span class="command"><strong>torbutton_weblistener</strong></span> and the <a class="link" href="#contentpolicy" title="@torproject.org/cssblocker;1 - components/cssblocker.js">content policy</a> (the latter being a hack to handle |
|
548 |
-javascript: urls). This behavior helps to satisfy the <a class="link" href="#location">Location Neutrality</a> requirement. |
|
549 |
- |
|
550 |
-</p><p> |
|
551 |
- |
|
552 |
-In addition, this setting also hooks various resolution properties of the |
|
553 |
-<a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window" target="_top">window</a>, |
|
554 |
-<a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window.screen" target="_top">window.screen</a>, |
|
555 |
-and <a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window.navigator" target="_top">window.navigator</a> |
|
556 |
-to mask window size information and user agent properties not handled by the |
|
557 |
-standard Firefox user agent override settings. The resolution hooks |
|
558 |
-effectively make the Firefox browser window appear to websites as if the renderable area |
|
559 |
-takes up the entire desktop, has no toolbar or other GUI element space, and |
|
560 |
-the desktop itself has no toolbars. |
|
561 |
-These hooks drastically reduce the amount of information available to do <a class="link" href="#fingerprinting">anonymity set reduction attacks</a> and help to |
|
562 |
-meet the <a class="link" href="#setpreservation">Anonymity Set Preservation</a> |
|
563 |
-requirements. |
|
564 |
- |
|
565 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2992126"></a>5.5. Resize windows to multiples of 50px during Tor usage (recommended)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.resize_windows</strong></span></p><p> |
|
566 |
- |
|
567 |
-This option drastically cuts down on the number of distinct anonymity sets |
|
568 |
-that divide the Tor web userbase. Without this setting, the dimensions for a |
|
569 |
-typical browser window range from 600-1200 horizontal pixels and 400-1000 |
|
570 |
-vertical pixels, or about 600x600 = 360000 different sets. Resizing the |
|
571 |
-browser window to multiples of 50 on each side reduces the number of sets by |
|
572 |
-50^2, bringing the total number of sets to 144. Of course, the distribution |
|
573 |
-among these sets are not uniform, but scaling by 50 will improve the situation |
|
574 |
-due to this non-uniformity for users in the less common resolutions. |
|
575 |
-Obviously the ideal situation would be to lie entirely about the browser |
|
576 |
-window size, but this will likely cause all sorts of rendering issues, and is |
|
577 |
-also not implementable in a foolproof way from extension land. |
|
578 |
- |
|
579 |
-</p><p> |
|
580 |
- |
|
581 |
-The implementation of this setting is spread across a couple of different |
|
582 |
-locations in the Torbutton javascript <a class="link" href="#browseroverlay" title="3.1. Browser Overlay - torbutton.xul">browser |
|
583 |
-overlay</a>. Since resizing minimized windows causes them to be restored, |
|
584 |
-and since maximized windows remember their previous size to the pixel, windows |
|
585 |
-must be resized before every document load (at the time of browser tagging) |
|
586 |
-via <code class="function">torbutton_check_round()</code>, called by |
|
587 |
-<code class="function">torbutton_update_tags()</code>. To prevent drift, the extension |
|
588 |
-tracks the original values of the windows and uses this to perform the |
|
589 |
-rounding on document load. In addition, to prevent the user from resizing a |
|
590 |
-window to a non-50px multiple, a resize listener |
|
591 |
-(<code class="function">torbutton_do_resize()</code>) is installed on every new browser |
|
592 |
-window to record the new size and round it to a 50px multiple while Tor is |
|
593 |
-enabled. In all cases, the browser's contentWindow.innerWidth and innerHeight |
|
594 |
-are set. This ensures that there is no discrepancy between the 50 pixel cutoff |
|
595 |
-and the actual renderable area of the browser (so that it is not possible to |
|
596 |
-infer toolbar size/presence by the distance to the nearest 50 pixel roundoff). |
|
597 |
- |
|
598 |
-</p><p> |
|
599 |
-This setting helps to meet the <a class="link" href="#setpreservation">Anonymity Set Preservation</a> requirements. |
|
600 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3004184"></a>5.6. Disable Updates During Tor (recommended)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.no_updates</strong></span></p><p>This setting causes Torbutton to disable the four <a class="ulink" href="http://wiki.mozilla.org/Update:Users/Checking_For_Updates#Preference_Controls_and_State" target="_top">Firefox |
|
601 |
-update settings</a> during Tor |
|
602 |
- usage: <span class="command"><strong>extensions.update.enabled</strong></span>, |
|
603 |
-<span class="command"><strong>app.update.enabled</strong></span>, |
|
604 |
- <span class="command"><strong>app.update.auto</strong></span>, and |
|
605 |
-<span class="command"><strong>browser.search.update</strong></span>. These prevent the |
|
606 |
- browser from updating extensions, checking for Firefox upgrades, and |
|
607 |
- checking for search plugin updates while Tor is enabled. |
|
608 |
- </p><p> |
|
609 |
-This setting satisfies the <a class="link" href="#updates">Update Safety</a> requirement. |
|
610 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2997514"></a>5.7. Disable Search Suggestions during Tor (recommended)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.no_search</strong></span></p><p> |
|
611 |
-This setting causes Torbutton to disable <a class="ulink" href="http://kb.mozillazine.org/Browser.search.suggest.enabled" target="_top"><span class="command"><strong>browser.search.suggest.enabled</strong></span></a> |
|
612 |
-during Tor usage. |
|
613 |
-This governs if you get Google search suggestions during Tor |
|
614 |
-usage. Your Google cookie is transmitted with google search suggestions, hence |
|
615 |
-this is recommended to be disabled. |
|
616 |
- |
|
617 |
-</p><p> |
|
618 |
-While this setting doesn't satisfy any Torbutton requirements, the fact that |
|
619 |
-cookies are transmitted for partially typed queries does not seem desirable |
|
620 |
-for Tor usage. |
|
621 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3000110"></a>5.8. Block Tor/Non-Tor access to network from file:// urls (recommended)</h3></div></div></div><p>Option: |
|
622 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.block_tor_file_net</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.block_nontor_file_net</strong></span></td></tr></table><p> |
|
623 |
- </p><p> |
|
624 |
- |
|
625 |
-These settings prevent file urls from performing network operations during the |
|
626 |
-respective Tor states. Firefox 2's implementation of same origin policy allows |
|
627 |
-file urls to read and <a class="ulink" href="http://www.gnucitizen.org/blog/content-disposition-hacking/" target="_top">submit |
|
628 |
-arbitrary files from the local filesystem</a> to arbitrary websites. To |
|
629 |
-make matters worse, the 'Content-Disposition' header can be injected |
|
630 |
-arbitrarily by exit nodes to trick users into running arbitrary html files in |
|
631 |
-the local context. These preferences cause the <a class="link" href="#contentpolicy" title="@torproject.org/cssblocker;1 - components/cssblocker.js">content policy</a> to block access to any network |
|
632 |
-resources from File urls during the appropriate Tor state. |
|
633 |
- |
|
634 |
-</p><p> |
|
635 |
- |
|
636 |
-This preference helps to ensure Tor's <a class="link" href="#isolation">Network |
|
637 |
-Isolation</a> requirement, by preventing file urls from executing network |
|
638 |
-operations in opposite Tor states. Also, allowing pages to submit arbitrary |
|
639 |
-files to arbitrary sites just generally seems like a bad idea. |
|
640 |
- |
|
641 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2998307"></a>5.9. Close all Tor/Non-Tor tabs and windows on toggle (optional)</h3></div></div></div><p>Options: |
|
642 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.close_nontor</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.close_tor</strong></span></td></tr></table><p> |
|
643 |
- </p><p> |
|
644 |
- |
|
645 |
-These settings cause Torbutton to enumerate through all windows and close all |
|
646 |
-tabs in each window for the appropriate Tor state. This code can be found in |
|
647 |
-<code class="function">torbutton_update_status()</code>. The main reason these settings |
|
648 |
-exist is as a backup mechanism in the event of any Javascript or content policy |
|
649 |
-leaks due to <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=409737" target="_top">Firefox Bug |
|
650 |
-409737</a>. Torbutton currently tries to block all Javascript network |
|
651 |
-activity via the content policy, but until that bug is fixed, there is some |
|
652 |
-risk that there are alternate ways to bypass the policy. This option is |
|
653 |
-available as an extra assurance of <a class="link" href="#isolation">Network |
|
654 |
-Isolation</a> for those who would like to be sure that when Tor is toggled |
|
655 |
-all page activity has ceased. It also serves as a potential future workaround |
|
656 |
-in the event a content policy failure is discovered, and provides an additional |
|
657 |
-level of protection for the <a class="link" href="#disk">Disk Avoidance</a> |
|
658 |
-protection so that browser state is not sitting around waiting to be swapped |
|
659 |
-out longer than necessary. |
|
660 |
- |
|
661 |
-</p><p> |
|
662 |
-While this setting doesn't satisfy any Torbutton requirements, the fact that |
|
663 |
-cookies are transmitted for partially typed queries does not seem desirable |
|
664 |
-for Tor usage. |
|
665 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2996566"></a>5.10. Isolate Access to History navigation to Tor state (crucial)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.block_js_history</strong></span></p><p> |
|
666 |
-This setting determines if Torbutton installs an <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsISHistoryListener.html" target="_top">nsISHistoryListener</a> |
|
667 |
-attached to the <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsISHistory.html" target="_top">sessionHistory</a> of |
|
668 |
-of each browser's <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/comps/c_webshell1.html" target="_top">webNavigatator</a>. |
|
669 |
-The nsIShistoryListener is instantiated with a reference to the containing |
|
670 |
-browser window and blocks the back, forward, and reload buttons on the browser |
|
671 |
-navigation bar when Tor is in an opposite state than the one to load the |
|
672 |
-current tab. In addition, Tor clears the session history during a new document |
|
673 |
-load if this setting is enabled. |
|
674 |
- |
|
675 |
- </p><p> |
|
676 |
- |
|
677 |
-This is marked as a crucial setting in part |
|
678 |
-because Javascript access to the history object is indistinguishable from |
|
679 |
-user clicks, and because |
|
680 |
-<a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=409737" target="_top">Firefox Bug |
|
681 |
-409737</a> allows javascript to execute in opposite Tor states, javascript |
|
682 |
-can issue reloads after Tor toggle to reveal your original IP. Even without |
|
683 |
-this bug, however, Javascript is still able to access previous pages in your |
|
684 |
-session history that may have been loaded under a different Tor state, to |
|
685 |
-attempt to correlate your activity. |
|
686 |
- |
|
687 |
- </p><p> |
|
688 |
- |
|
689 |
-This setting helps to fulfill Torbutton's <a class="link" href="#state">State |
|
690 |
-Separation</a> and (until Bug 409737 is fixed) <a class="link" href="#isolation">Network Isolation</a> |
|
691 |
-requirements. |
|
692 |
- |
|
693 |
- </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2998342"></a>5.11. History Access Settings</h3></div></div></div><p>Options: |
|
694 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.block_thread</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.block_nthread</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.block_thwrite</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.block_nthwrite</strong></span></td></tr></table><p> |
|
695 |
- </p><p>These four settings govern the behavior of the <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/ignore-history.js" target="_top">components/ignore-history.js</a> |
|
696 |
-history blocker component mentioned above. By hooking the browser's view of |
|
697 |
-the history itself via the <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/comps/c_browserglobalhistory2.html" target="_top">mozilla.org/browser/global-history;2</a> |
|
698 |
-component, this mechanism defeats all document-based <a class="ulink" href="http://gemal.dk/browserspy/css.html" target="_top">history disclosure |
|
699 |
-attacks</a>, including <a class="ulink" href="http://ha.ckers.org/weird/CSS-history.cgi" target="_top">CSS-only attacks</a>. |
|
700 |
-</p><p> |
|
701 |
- |
|
702 |
-On Firefox 3, the history write settings also govern if Torbutton sets |
|
703 |
-<span class="command"><strong>browser.history_expire_days</strong></span> to 0 on the appropriate Tor |
|
704 |
-state, which <a class="ulink" href="http://developer.mozilla.org/en/docs/index.php?title=nsINavHistoryService#Attributes" target="_top">should |
|
705 |
-disable</a> all <a class="ulink" href="http://developer.mozilla.org/en/docs/Places" target="_top">Places</a> database |
|
706 |
-writes. |
|
707 |
- |
|
708 |
-</p><p> |
|
709 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> and <a class="link" href="#disk">Disk Avoidance</a> requirements. |
|
710 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2957709"></a>5.12. Clear History During Tor Toggle (optional)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.clear_history</strong></span></p><p>This setting governs if Torbutton calls |
|
711 |
-<a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIBrowserHistory.html#method_removeAllPages" target="_top">nsIBrowserHistory.removeAllPages</a> |
|
712 |
-and <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsISHistory.html#method_PurgeHistory" target="_top">nsISHistory.PurgeHistory</a> |
|
713 |
-for each tab on Tor toggle.</p><p> |
|
714 |
-This setting is an optional way to help satisfy the <a class="link" href="#state">State Separation</a> requirement. |
|
715 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962370"></a>5.13. Block Password+Form saving during Tor/Non-Tor</h3></div></div></div><p>Options: |
|
716 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.block_tforms</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.block_ntforms</strong></span></td></tr></table><p> |
|
717 |
- </p><p>These settings govern if Torbutton disables |
|
718 |
-<span class="command"><strong>browser.formfill.enable</strong></span> |
|
719 |
-and <span class="command"><strong>signon.rememberSignons</strong></span> during Tor and Non-Tor usage. |
|
720 |
-Since form fields can be read at any time by Javascript, this setting is a lot |
|
721 |
-more important than it seems. |
|
722 |
-</p><p> |
|
723 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> and <a class="link" href="#disk">Disk Avoidance</a> requirements. |
|
724 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962437"></a>5.14. Block Tor disk cache and clear all cache on Tor Toggle</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.clear_cache</strong></span> |
|
725 |
- </p><p>This option causes Torbutton to call <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsICacheService.html#method_evictEntries" target="_top">nsICacheService.evictEntries(0)</a> |
|
726 |
-on Tor toggle to remove all entries from the cache. In addition, this setting |
|
727 |
-causes Torbutton to set <a class="ulink" href="http://kb.mozillazine.org/Browser.cache.disk.enable" target="_top">browser.cache.disk.enable</a> to false. |
|
728 |
-</p><p> |
|
729 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> and <a class="link" href="#disk">Disk Avoidance</a> requirements. |
|
730 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962492"></a>5.15. Block disk and memory cache during Tor</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.block_cache</strong></span></p><p>This setting |
|
731 |
-causes Torbutton to set <a class="ulink" href="http://kb.mozillazine.org/Browser.cache.memory.enable" target="_top">browser.cache.memory.enable</a>, |
|
732 |
-<a class="ulink" href="http://kb.mozillazine.org/Browser.cache.disk.enable" target="_top">browser.cache.disk.enable</a> and |
|
733 |
-<a class="ulink" href="http://kb.mozillazine.org/Network.http.use-cache" target="_top">network.http.use-cache</a> to false during tor usage. |
|
734 |
-</p><p> |
|
735 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> and <a class="link" href="#disk">Disk Avoidance</a> requirements. |
|
736 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962549"></a>5.16. Clear Cookies on Tor Toggle</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.clear_cookies</strong></span> |
|
737 |
- </p><p> |
|
738 |
- |
|
739 |
-This setting causes Torbutton to call <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsICookieManager.html#method_removeAll" target="_top">nsICookieManager.removeAll()</a> on |
|
740 |
-every Tor toggle. In addition, this sets <a class="ulink" href="http://kb.mozillazine.org/Network.cookie.lifetimePolicy" target="_top">network.cookie.lifetimePolicy</a> |
|
741 |
-to 2 for Tor usage, which causes all cookies to be demoted to session cookies, |
|
742 |
-which prevents them from being written to disk. |
|
743 |
- |
|
744 |
-</p><p> |
|
745 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> and <a class="link" href="#disk">Disk Avoidance</a> requirements. |
|
746 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962603"></a>5.17. Store Non-Tor cookies in a protected jar</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.cookie_jars</strong></span> |
|
747 |
- </p><p> |
|
748 |
- |
|
749 |
-This setting causes Torbutton to use <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js" target="_top">@stanford.edu/cookie-jar-selector;2</a> to store |
|
750 |
-non-tor cookies in a cookie jar during Tor usage, and clear the Tor cookies |
|
751 |
-before restoring the jar. |
|
752 |
-</p><p> |
|
753 |
-This setting also sets <a class="ulink" href="http://kb.mozillazine.org/Network.cookie.lifetimePolicy" target="_top">network.cookie.lifetimePolicy</a> |
|
754 |
-to 2 for Tor usage, which causes all cookies to be demoted to session cookies, |
|
755 |
-which prevents them from being written to disk. |
|
756 |
- |
|
757 |
-</p><p> |
|
758 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> and <a class="link" href="#disk">Disk Avoidance</a> requirements. |
|
759 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962662"></a>5.18. Store both Non-Tor and Tor cookies in a protected jar (dangerous)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.dual_cookie_jars</strong></span> |
|
760 |
- </p><p> |
|
761 |
- |
|
762 |
-This setting causes Torbutton to use <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js" target="_top">@stanford.edu/cookie-jar-selector;2</a> to store |
|
763 |
-both Tor and Non-Tor cookies into protected jars. |
|
764 |
-</p><p> |
|
765 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> requirement. |
|
766 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962702"></a>5.19. Manage My Own Cookies (dangerous)</h3></div></div></div><p>Options: None</p><p>This setting disables all Torbutton cookie handling by setting the above |
|
767 |
-cookie prefs all to false.</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962718"></a>5.20. Disable DOM Storage during Tor usage (crucial)</h3></div></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962720"></a>5.20.1. Do not write Tor/Non-Tor cookies to disk</h3></div></div></div><p>Options: |
|
768 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.tor_memory_jar</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.nontor_memory_jar</strong></span></td></tr></table><p> |
|
769 |
- </p><p> |
|
770 |
-These settings (contributed by arno) cause Torbutton to set <a class="ulink" href="http://kb.mozillazine.org/Network.cookie.lifetimePolicy" target="_top">network.cookie.lifetimePolicy</a> |
|
771 |
-to 2 during the appropriate Tor state, and to store cookies acquired in that |
|
772 |
-state into a Javascript |
|
773 |
-<a class="ulink" href="http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Guide:Processing_XML_with_E4X" target="_top">E4X</a> |
|
774 |
-object as opposed to writing them to disk. |
|
775 |
-</p><p> |
|
776 |
-This allows Torbutton to provide an option to preserve a user's |
|
777 |
-cookies while still satisfying the <a class="link" href="#disk">Disk Avoidance</a> |
|
778 |
-requirement. |
|
779 |
-</p></div><p>Option: <span class="command"><strong>extensions.torbutton.disable_domstorage</strong></span> |
|
780 |
- </p><p> |
|
781 |
- |
|
782 |
-This setting causes Torbutton to toggle <span class="command"><strong>dom.storage.enabled</strong></span> during Tor |
|
783 |
-usage to prevent |
|
784 |
-<a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:Storage" target="_top">DOM Storage</a> from |
|
785 |
- being used to store persistent information across Tor states.</p><p> |
|
786 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> requirement. |
|
787 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id2962826"></a>5.21. Clear HTTP Auth on Tor Toggle (recommended)</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.clear_http_auth</strong></span> |
|
788 |
- </p><p> |
|
789 |
-This setting causes Torbutton to call <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIHttpAuthManager.html#method_clearAll" target="_top">nsIHttpAuthManager.clearAll()</a> |
|
790 |
-every time Tor is toggled. |
|
791 |
-</p><p> |
|
792 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> requirement. |
|
793 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3005721"></a>5.22. Clear cookies on Tor/Non-Tor shutdown</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.shutdown_method</strong></span> |
|
794 |
- </p><p> This option variable can actually take 3 values: 0, 1, and 2. 0 means no |
|
795 |
-cookie clearing, 1 means clear only during Tor-enabled shutdown, and 2 means |
|
796 |
-clear for both Tor and Non-Tor shutdown. When set to 1 or 2, Torbutton listens |
|
797 |
-for the <a class="ulink" href="http://developer.mozilla.org/en/docs/Observer_Notifications#Application_shutdown" target="_top">quit-application-granted</a> event in |
|
798 |
-<code class="function">torbutton_uninstall_observer()</code> and use <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js" target="_top">@stanford.edu/cookie-jar-selector;2</a> |
|
799 |
-to clear out all cookies and all cookie jars upon shutdown. </p><p> |
|
800 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> requirement. |
|
801 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3005775"></a>5.23. Reload cookie jar/clear cookies on Firefox crash</h3></div></div></div><p>Options: |
|
802 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.reload_crashed_jar</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.crashed</strong></span></td></tr></table><p> |
|
803 |
- </p><p>This is no longer a user visible option, and is enabled by default. In |
|
804 |
-the event of a crash, the Torbutton <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/crash-observer.js" target="_top">components/crash-observer.js</a> |
|
805 |
- component will notify the Chrome (via the |
|
806 |
- <span class="command"><strong>extensions.torbutton.crashed</strong></span> pref and a <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/ifaces/nsIPrefBranch2.html#method_addObserver" target="_top">pref |
|
807 |
-observer</a> in |
|
808 |
-the chrome that listens for this update), and Torbutton will load the |
|
809 |
- correct jar for the current Tor state via the <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/cookie-jar-selector.js" target="_top">@stanford.edu/cookie-jar-selector;2</a> |
|
810 |
- component.</p><p> |
|
811 |
-This setting helps to satisfy the <a class="link" href="#state">State Separation</a> requirement in the event of Firefox |
|
812 |
-crashes. |
|
813 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3005850"></a>5.24. On crash recovery or session restored startup, restore via: Tor, Non-Tor</h3></div></div></div><p>Options: |
|
814 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.restore_tor</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.crashed</strong></span></td></tr></table><p> |
|
815 |
- </p><p>This option works with the Torbutton <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/crash-observer.js" target="_top">crash-observer.js</a> |
|
816 |
- to set the Tor state after a crash is detected (via the |
|
817 |
- <span class="command"><strong>extensions.torbutton.crashed</strong></span> pref)</p><p> |
|
818 |
- |
|
819 |
-Since the Tor state after a Firefox crash is unknown/indeterminate, this |
|
820 |
-setting helps to satisfy the <a class="link" href="#state">State Separation</a> |
|
821 |
-requirement in the event of Firefox crashes by ensuring all cookies, |
|
822 |
-settings and saved sessions are reloaded from a fixed Tor state. |
|
823 |
- |
|
824 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3005910"></a>5.25. On normal startup, set state to: Tor, Non-Tor, Shutdown State</h3></div></div></div><p>Options: |
|
825 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.startup_state</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.noncrashed</strong></span></td></tr></table><p> |
|
826 |
- </p><p>This option also works with the Torbutton <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/crash-observer.js" target="_top">crash-observer.js</a> |
|
827 |
- to set the Tor state after a normal startup is detected (via the |
|
828 |
- <span class="command"><strong>extensions.torbutton.noncrashed</strong></span> pref)</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3005958"></a>5.26. Prevent session store from saving Non-Tor/Tor-loaded tabs</h3></div></div></div><p>Options: |
|
829 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.nonontor_sessionstore</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.notor_sessionstore</strong></span></td></tr></table><p> |
|
830 |
- </p><p>If these options are enabled, the <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/components/nsSessionStore3.js" target="_top">replacement nsSessionStore.js</a> |
|
831 |
- component checks the <span class="command"><strong>__tb_tor_fetched</strong></span> tag of tabs before writing them |
|
832 |
- out. If the tag is from a blocked Tor state, the tab is not written to disk. |
|
833 |
- </p><p> |
|
834 |
-This setting helps to satisfy the <a class="link" href="#disk">Disk Avoidance</a> |
|
835 |
-requirement, and also helps to satisfy the <a class="link" href="#state">State Separation</a> requirement in the event of Firefox |
|
836 |
-crashes. |
|
837 |
- |
|
838 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3006023"></a>5.27. Set user agent during Tor usage (crucial)</h3></div></div></div><p>Options: |
|
839 |
- </p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.set_uagent</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.oscpu_override</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.platform_override</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.productsub_override</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.appname_override</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.appversion_override</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.useragent_override</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.useragent_vendor</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.useragent_vendorSub</strong></span></td></tr></table><p> |
|
840 |
- </p><p>On face, user agent switching appears to be straight-forward in Firefox. |
|
841 |
-It provides several options for controlling the browser user agent string: |
|
842 |
-<span class="command"><strong>general.appname.override</strong></span>, |
|
843 |
-<span class="command"><strong>general.appversion.override</strong></span>, |
|
844 |
-<span class="command"><strong>general.platform.override</strong></span>, |
|
845 |
-<span class="command"><strong>general.useragent.override</strong></span>, |
|
846 |
-<span class="command"><strong>general.useragent.vendor</strong></span>, and |
|
847 |
-<span class="command"><strong>general.useragent.vendorSub</strong></span>. If |
|
848 |
-the Torbutton preference <span class="command"><strong>extensions.torbutton.set_uagent</strong></span> is |
|
849 |
-true, Torbutton copies all of the other above prefs into their corresponding |
|
850 |
-browser preferences during Tor usage.</p><p>However, this is not the whole story. Additionally, even with the above |
|
851 |
-prefs set, the <span class="command"><strong>oscpu</strong></span>, <span class="command"><strong>buildID</strong></span>, and <span class="command"><strong>productSub</strong></span> fields of the |
|
852 |
-<a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window.navigator" target="_top">navigator</a> object are not changed appropriately by the above prefs. |
|
853 |
-Javascript hooks implemented in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/jshooks.js" target="_top">chrome/content/jshooks.js</a> are installed as part of the |
|
854 |
-same mechanism that hooks the date object. |
|
855 |
-</p><p> |
|
856 |
- |
|
857 |
-It also turns out that it is possible to detect the original Firefox version |
|
858 |
-by <a class="ulink" href="http://0x000000.com/index.php?i=523&bin=1000001011" target="_top">inspecting |
|
859 |
-certain resource:// files</a>. These cases are handled by Torbutton's |
|
860 |
-<a class="link" href="#contentpolicy" title="@torproject.org/cssblocker;1 - components/cssblocker.js">content policy</a>. |
|
861 |
- |
|
862 |
-</p><p> |
|
863 |
-This setting helps to satisfy the <a class="link" href="#setpreservation">Anonymity Set Preservation</a> requirement. |
|
864 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3006210"></a>5.28. Spoof US English Browser</h3></div></div></div><p>Options: |
|
865 |
-</p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.spoof_english</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.spoof_charset</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.spoof_language</strong></span></td></tr></table><p> |
|
866 |
-</p><p> This option causes Torbutton to set |
|
867 |
-<span class="command"><strong>general.useragent.locale</strong></span>, |
|
868 |
-<span class="command"><strong>intl.accept_charsets</strong></span> and |
|
869 |
-<span class="command"><strong>intl.accept_languages</strong></span> to the value specified in |
|
870 |
-<span class="command"><strong>extensions.torbutton.spoof_locale</strong></span>, |
|
871 |
-<span class="command"><strong>extensions.torbutton.spoof_charset</strong></span> and |
|
872 |
-<span class="command"><strong>extensions.torbutton.spoof_language</strong></span> during Tor usage. </p><p> |
|
873 |
-This setting helps to satisfy the <a class="link" href="#setpreservation">Anonymity Set Preservation</a> and <a class="link" href="#location">Location Neutrality</a> requirements. |
|
874 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3006297"></a>5.29. Don't send referrer during Tor Usage</h3></div></div></div><p>Option: <span class="command"><strong>extensions.torbutton.disable_referer</strong></span> |
|
875 |
-</p><p> |
|
876 |
-This option causes Torbutton to set <a class="ulink" href="http://kb.mozillazine.org/Network.http.sendSecureXSiteReferrer" target="_top">network.http.sendSecureXSiteReferrer</a> and |
|
877 |
-<a class="ulink" href="http://kb.mozillazine.org/Network.http.sendRefererHeader" target="_top">network.http.sendRefererHeader</a> during Tor usage.</p><p> |
|
878 |
-This setting also does not directly satisfy any Torbutton requirement, but |
|
879 |
-some may desire to mask their referrer for general privacy concerns. |
|
880 |
-</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3006338"></a>5.30. Store SSL/CA Certs in separate jars for Tor/Non-Tor (recommended)</h3></div></div></div><p>Options: |
|
881 |
-</p><table class="simplelist" border="0" summary="Simple list"><tr><td><span class="command"><strong>extensions.torbutton.jar_certs</strong></span></td></tr><tr><td><span class="command"><strong>extensions.torbutton.jar_ca_certs</strong></span></td></tr></table><p> |
|
882 |
-</p><p> |
|
883 |
- |
|
884 |
-These settings govern if Torbutton attempts to isolate the user's SSL |
|
885 |
-certificates into separate jars for each Tor state. This isolation is |
|
886 |
-implemented in <code class="function">torbutton_jar_certs()</code> in <a class="ulink" href="https://tor-svn.freehaven.net/svn/torbutton/trunk/src/chrome/content/torbutton.js" target="_top">chrome/content/torbutton.js</a>, |
|
887 |
-which calls <code class="function">torbutton_jar_cert_type()</code> and |
|
888 |
-<code class="function">torbutton_unjar_cert_type()</code> for each certificate type in |
|
889 |
-the <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/comps/c_securitynsscertcache1.html" target="_top">@mozilla.org/security/nsscertcache;1</a>. |
|
890 |
-Certificates are deleted from and imported to the <a class="ulink" href="http://www.xulplanet.com/references/xpcomref/comps/c_securityx509certdb1.html" target="_top">@mozilla.org/security/x509certdb;1</a>. |
|
891 |
-</p><p> |
|
892 |
-The first time this pref is used, a backup of the user's certificates is |
|
893 |
-created in their profile directory under the name |
|
894 |
-<code class="filename">cert8.db.bak</code>. This file can be copied back to |
|
895 |
-<code class="filename">cert8.db</code> to fully restore the original state of the |
|
896 |
-user's certificates in the event of any error. |
|
897 |
-</p><p> |
|
898 |
-Since exit nodes and malicious sites can insert content elements sourced to |
|
899 |
-specific SSL sites to query if a user has a certain certificate, |
|
900 |
-this setting helps to satisfy the <a class="link" href="#state">State |
|
901 |
-Separation</a> requirement of Torbutton. Unfortunately, <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=435159" target="_top">Firefox Bug |
|
902 |
-435159</a> prevents it from functioning correctly in the event of rapid Tor toggle, so it |
|
903 |
-is currently not exposed via the preferences UI. |
|
904 |
- |
|
905 |
-</p></div></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="FirefoxBugs"></a>6. Relevant Firefox Bugs</h2></div></div></div><p> |
|
906 |
- |
|
907 |
- </p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="FirefoxSecurity"></a>6.1. Bugs impacting security</h3></div></div></div><p> |
|
908 |
- |
|
909 |
-Torbutton has to work around a number of Firefox bugs that impact its |
|
910 |
-security. Most of these are mentioned elsewhere in this document, but they |
|
911 |
-have also been gathered here for reference. Several of these have fixes in |
|
912 |
-Firefox3.0/trunk, but are listed because they still have not been backported |
|
913 |
-to FF2.0. In order of decreasing severity, they are: |
|
914 |
- |
|
915 |
- </p><div class="orderedlist"><ol type="1"><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=392274" target="_top">Bug 392274 - Timezone |
|
916 |
-config/chrome API</a><p> |
|
917 |
-The lack of a config or API to configure the timezone requires Torbutton to |
|
918 |
-<a class="link" href="#jshooks" title="5.4. Hook Dangerous Javascript (crucial)">insert client content window javascript</a> to hook |
|
919 |
-the Date object. Additionally, a way to <a class="ulink" href="http://pseudo-flaw.net/tor/torbutton/unmask-date.html" target="_top">remove the Date |
|
920 |
-hooks</a> was discovered by Greg Fleischer. Worse, on Firefox 3, |
|
921 |
-javascript sandboxing prevents most of the javascript hooks from being |
|
922 |
-installed, including the Date hooks. On Windows and Linux, you can set the TZ |
|
923 |
-environment variable to "UTC" as a workaround. Firefox will obey this |
|
924 |
-environment variable for your Timezone on those platforms, but on Windows this |
|
925 |
-does not take effect until browser restart. |
|
926 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=436250" target="_top">Bug 436250 - Livemarks can't be |
|
927 |
-disabled at runtime</a><p> |
|
928 |
- |
|
929 |
-The RSS Feed based "Livemarks"/"Live Bookmarks" update frequency is controlled |
|
930 |
-by the pref <span class="command"><strong>browser.bookmarks.livemark_refresh_seconds</strong></span>. |
|
931 |
-However, changing this preference does not cancel any pending timers, which |
|
932 |
-means that at least one livemarks pref fetch will happen over Tor, and once |
|
933 |
-this pref is set to disable livemarks for Tor, changing it back will never |
|
934 |
-cause the service to start back up again. |
|
935 |
- |
|
936 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=435159" target="_top">Bug 435159 - |
|
937 |
-nsNSSCertificateDB::DeleteCertificate has race conditions</a><p> |
|
938 |
- |
|
939 |
-In Torbutton 1.2.0rc1, code was added to attempt to isolate SSL certificates |
|
940 |
-the user has installed. Unfortunately, the method call to delete a certificate |
|
941 |
-from the current certificate database acts lazily: it only sets a variable |
|
942 |
-that marks a cert for deletion later, and it is not cleared if that |
|
943 |
-certificate is re-added. This means that if the Tor state is toggled quickly, |
|
944 |
-that certificate could remain present until it is re-inserted (causing an |
|
945 |
-error dialog), and worse, it would still be deleted after that. The lack of |
|
946 |
-this functionality is considered a Torbutton security bug because cert |
|
947 |
-isolation is considered a <a class="link" href="#state">State Separation</a> |
|
948 |
-feature. |
|
949 |
- |
|
950 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=409737" target="_top">Bug 409737 - |
|
951 |
-javascript.enabled and docShell.allowJavascript do not disable all event |
|
952 |
-handlers</a><p> |
|
953 |
- |
|
954 |
-This bug allows pages to execute javascript via addEventListener and perhaps |
|
955 |
-other callbacks. In order to prevent this bug from enabling an attacker to |
|
956 |
-break the <a class="link" href="#isolation">Network Isolation</a> requirement, |
|
957 |
-Torbutton 1.1.13 began blocking popups and history manipulation from different |
|
958 |
-Tor states. So long as there are no ways to open popups or redirect the user |
|
959 |
-to a new page, the <a class="link" href="#contentpolicy" title="@torproject.org/cssblocker;1 - components/cssblocker.js">Torbutton content |
|
960 |
-policy</a> should block Javascript network access. However, if there are |
|
961 |
-ways to open popups or perform redirects such that Torbutton cannot block |
|
962 |
-them, pages may still have free reign to break that requirement and reveal a |
|
963 |
-user's original IP address. |
|
964 |
- |
|
965 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=405652" target="_top">Bug 405652 - In the |
|
966 |
-TLS ClientHello message the gmt_unix_time is incorrect</a><p> |
|
967 |
- |
|
968 |
-It turns out that Firefox's SSL implementation sends the machine uptime as the |
|
969 |
-current time. This essentially is a unique identifier that can be used for |
|
970 |
-the duration of your machine uptime. The issue has been fixed in Firefox 3.0, |
|
971 |
-but it has as of yet not been backported to 2.0. |
|
972 |
- |
|
973 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=143220" target="_top">Bug 143220 - Script can get the value of a file control, including the path</a><p> |
|
974 |
- |
|
975 |
-Javascript can query the .value field of file input dialogs to retrieve |
|
976 |
-username and sometimes hostname/workgroup information. This is obviously very |
|
977 |
-dangerous for people who are attempting to submit files anonymously via |
|
978 |
-webforms (ie whistleblowers and anonymous publishers). It is also fixed in |
|
979 |
-Firefox 3.0, but has not yet been backported to 2.0. |
|
980 |
- |
|
981 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=418119" target="_top">Bug 418119 - nsIContentPolicy not called for external DTDs of XML documents</a><p> |
|
982 |
- |
|
983 |
-XML documents can source chrome and resource URLs in their DTDs without a call |
|
984 |
-to nsIContentPolicy::shouldLoad. Enumerating chrome URLs gives websites and |
|
985 |
-exit nodes a lot of information. They can use it to probe for vulnerable |
|
986 |
-versions of extensions, and can also use it to build an <a class="link" href="#fingerprinting">identifier for tracking purposes</a>. This bug |
|
987 |
-makes it impossible for extensions such as Adblock and Torbutton to prevent |
|
988 |
-chrome inspection and enumeration. There is no workaround for this bug as of |
|
989 |
-yet. |
|
990 |
- |
|
991 |
- </p></li></ol></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="FirefoxWishlist"></a>6.2. Bugs blocking functionality</h3></div></div></div><p> |
|
992 |
-The following bugs impact Torbutton and similar extensions' functionality. |
|
993 |
- </p><div class="orderedlist"><ol type="1"><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=439384" target="_top">Bug 439384 - |
|
994 |
-"profile-do-change" event does not cause cookie table reload</a><p> |
|
995 |
- |
|
996 |
-In Firefox 3, the change to the new sqlite database for cookie storage has a |
|
997 |
-bug that prevents Torbutton's cookie jaring from working properly. The |
|
998 |
-"profile-do-change" observer event no longer properly causes either a sync or |
|
999 |
-reload of the cookie database from disk after it is copied into place. |
|
1000 |
-Torbutton currently works around this by issuing the SQLLite queries manually |
|
1001 |
-to store and rebuild the cookie database. |
|
1002 |
- |
|
1003 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=417869" target="_top">Bug 417869 - |
|
1004 |
-Browser context is difficult to obtain from many XPCOM callbacks</a><p> |
|
1005 |
- |
|
1006 |
-It is difficult to determine which tabbrowser many XPCOM callbacks originate |
|
1007 |
-from, and in some cases absolutely no context information is provided at all. |
|
1008 |
-While this doesn't have much of an effect on Torbutton, it does make writing |
|
1009 |
-extensions that would like to do per-tab settings and content filters (such as |
|
1010 |
-FoxyProxy) difficult to impossible to implement securely. |
|
1011 |
- |
|
1012 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=418321" target="_top">Bug 418321 - |
|
1013 |
-Components do not expose disk interfaces</a><p> |
|
1014 |
- |
|
1015 |
-Several components currently provide no way of reimplementing their disk |
|
1016 |
-access to easily satisfy Torbutton's <a class="link" href="#disk">Disk |
|
1017 |
-Avoidance</a> requirements. Workarounds exist, but they are <a class="link" href="#sessionstore" title="@mozilla.org/browser/sessionstore;1 - components/nsSessionStore2.js and components/nsSessionStore3.js">clunky</a>, and |
|
1018 |
-some of them involve disabling functionality during Tor usage. |
|
1019 |
- |
|
1020 |
- </p></li></ol></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="FirefoxMiscBugs"></a>6.3. Low Priority Bugs</h3></div></div></div><p> |
|
1021 |
-The following bugs have an effect upon Torbutton, but are superseded by more |
|
1022 |
-practical and more easily fixable variant bugs above; or have stable, simple |
|
1023 |
-workarounds. |
|
1024 |
- </p><div class="orderedlist"><ol type="1"><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=435151" target="_top">Bug 435151 - XPCSafeJSObjectWrapper breaks evalInSandbox</a><p> |
|
1025 |
- |
|
1026 |
-Under Firefox 3, the XPCSafeJSObjectWrapper breaks when you try to use |
|
1027 |
-constructors of classes defined from within the scope of the sandbox, among |
|
1028 |
-other things. This prevents Torbutton from applying the Timezone hooks under |
|
1029 |
-Firefox 3, but a better solution for Torbutton's specific date hooking needs |
|
1030 |
-would be a fix for the above mentioned Bug 392274. Of course, many more |
|
1031 |
-extensions may be interested in the sandbox hooking functionality working |
|
1032 |
-properly though. |
|
1033 |
- |
|
1034 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=437014" target="_top">Bug 437014 - |
|
1035 |
-nsIContentPolicy::shouldLoad no longer called for favicons</a><p> |
|
1036 |
- |
|
1037 |
-Firefox 3.0 stopped calling the shouldLoad call of content policy for favicon |
|
1038 |
-loads. Torbutton had relied on this call to block favicon loads for opposite |
|
1039 |
-Tor states. The workaround it employs for Firefox 3 is to cancel the request |
|
1040 |
-when it arrives in the <span class="command"><strong>torbutton_http_observer</strong></span> used for |
|
1041 |
-blocking full page plugin loads. This seems to work just fine, but is a bit |
|
1042 |
-dirty. |
|
1043 |
- |
|
1044 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=437016" target="_top">Bug 437016 - |
|
1045 |
-nsIContentPolicy::shouldLoad not called for livemarks</a><p> |
|
1046 |
- |
|
1047 |
-An alternative fix for the livemarks bug above would be to block livemarks |
|
1048 |
-fetches from the content policy. Unfortunately shouldLoad is not called for |
|
1049 |
-livemarks fetches. |
|
1050 |
- |
|
1051 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=418986" target="_top">Bug 418986 - window.screen |
|
1052 |
-provides a large amount of identifiable information</a><p> |
|
1053 |
- |
|
1054 |
-As <a class="link" href="#fingerprinting">mentioned above</a>, a large amount of |
|
1055 |
-information is available from <a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:window.screen" target="_top">window.screen</a>. |
|
1056 |
-Currently, there is no way to obscure this information without Javascript |
|
1057 |
-hooking. This bug is a feature request to provide some other method to change |
|
1058 |
-these values. |
|
1059 |
- |
|
1060 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=309524" target="_top">Bug 309524</a> |
|
1061 |
-and <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=380556" target="_top">Bug |
|
1062 |
-380556</a> - nsIContentPolicy::shouldProcess is not called. |
|
1063 |
- <p> |
|
1064 |
- |
|
1065 |
-This is a call that would be useful to develop a better workaround for the |
|
1066 |
-allowPlugins issue above. If the content policy were called before a URL was |
|
1067 |
-handed over to a plugin or helper app, it would make the workaround for the |
|
1068 |
-above allowPlugins bug a lot cleaner. Obviously this bug is not as severe as |
|
1069 |
-the others though, but it might be nice to have this API as a backup. |
|
1070 |
- |
|
1071 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=401296" target="_top">Bug 401296 - docShell.allowPlugins |
|
1072 |
-not honored for direct links</a> (Perhaps subset of <a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=282106" target="_top">Bug 282106</a>?) |
|
1073 |
- <p> |
|
1074 |
- |
|
1075 |
-Similar to the javascript plugin disabling attribute, the plugin disabling |
|
1076 |
-attribute is also not perfect — it is ignored for direct links to plugin |
|
1077 |
-handled content, as well as meta-refreshes to plugin handled content. This |
|
1078 |
-requires Torbutton to listen to a number of different http events to intercept |
|
1079 |
-plugin-related mime type URLs and cancel their requests. Again, since plugins |
|
1080 |
-are quite horrible about obeying proxy settings, loading a plugin pretty much |
|
1081 |
-ensures a way to break the <a class="link" href="#isolation">Network Isolation</a> |
|
1082 |
-requirement and reveal a user's original IP address. Torbutton's code to |
|
1083 |
-perform this workaround has been subverted at least once already by Kyle |
|
1084 |
-Williams. |
|
1085 |
- |
|
1086 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=418983" target="_top">Bug 41893 - Scoping |
|
1087 |
-issues with window.__defineGetter__()</a><p> |
|
1088 |
- |
|
1089 |
-For some reason, defining getters off of window seems to mess with the |
|
1090 |
-implicit window scoping in some documents. There is a workaround for this bug, |
|
1091 |
-so it is barely relevant. It would be far more useful to eliminate the need |
|
1092 |
-for Javascript hooking in the first place by addressing the above bugs. This |
|
1093 |
-bug is just listed for completeness. |
|
1094 |
- |
|
1095 |
- </p></li><li><a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=419598" target="_top">Bug 419598 - 'var |
|
1096 |
-Date' is deletable</a><p> |
|
1097 |
- |
|
1098 |
-Based on Page 62 of the <a class="ulink" href="http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf" target="_top">ECMA-262 |
|
1099 |
-Javascript spec</a>, it seems like it should be possible to do something |
|
1100 |
-like the following to prevent the Date object from being unmasked: |
|
1101 |
-</p><pre class="screen"> |
|
1102 |
-with(window) { |
|
1103 |
- var Date = fakeDate; |
|
1104 |
- var otherVariable = 42; |
|
1105 |
-} |
|
1106 |
- |
|
1107 |
-delete window.Date; // Should fail. Instead succeeds, revealing original Date. |
|
1108 |
-delete window.otherVariable; // Fails, leaving window.otherVariable set to 42. |
|
1109 |
-</pre><p> |
|
1110 |
- |
|
1111 |
-From the ECMA-262 spec: |
|
1112 |
- |
|
1113 |
-</p><div class="blockquote"><blockquote class="blockquote"> |
|
1114 |
-If the variable statement occurs inside a FunctionDeclaration, the variables |
|
1115 |
-are defined with function-local scope in that function, as described in |
|
1116 |
-s10.1.3. Otherwise, they are defined with global scope (that is, they are |
|
1117 |
-created as members of the global object, as described in 10.1.3) using |
|
1118 |
-property attributes { DontDelete }. Variables are created when the execution |
|
1119 |
-scope is entered. A Block does not define a new execution scope. Only Program |
|
1120 |
-and FunctionDeclaration produce a new scope. Variables are initialized to |
|
1121 |
-undefined when created. A variable with an Initialiser is assigned the value |
|
1122 |
-of its AssignmentExpression when the VariableStatement is executed, not when |
|
1123 |
-the variable is created. |
|
1124 |
-</blockquote></div><p> |
|
1125 |
- |
|
1126 |
-In fact, this is exactly how the with statement with a variable declaration |
|
1127 |
-behaves <span class="emphasis"><em>for all other variables other than ones that shadow system |
|
1128 |
-variables</em></span>. Some variables (such as |
|
1129 |
-<span class="command"><strong>window.screen</strong></span>, and <span class="command"><strong>window.history</strong></span>) can't |
|
1130 |
-even be shadowed in this way, and give an error about lacking a setter. If |
|
1131 |
-such shadowing were possible, it would greatly simplify the Javascript hooking |
|
1132 |
-code, which currently relies on undocumented semantics of |
|
1133 |
-<span class="command"><strong>__proto__</strong></span> to copy the original values in the event of a |
|
1134 |
-delete. This <span class="command"><strong>__proto__</strong></span> hack unfortunately does not work for |
|
1135 |
-the Date object though. |
|
1136 |
- |
|
1137 |
- </p></li></ol></div></div></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="TestPlan"></a>7. Testing</h2></div></div></div><p> |
|
1138 |
- |
|
1139 |
-The purpose of this section is to cover all the known ways that Tor browser |
|
1140 |
-security can be subverted from a testing and penetration perspective. The hope |
|
1141 |
-is that it will be useful both for creating a "Tor Safety Check" |
|
1142 |
-page, and for developing novel tests and actively attacking Torbutton with the |
|
1143 |
-goal of finding vulnerabilities in either it or the Mozilla components, |
|
1144 |
-interfaces and settings upon which it relies. |
|
1145 |
- |
|
1146 |
- </p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="Categories"></a>7.1. Single state testing</h3></div></div></div><p> |
|
1147 |
-The following tests can be run from a single web page in one visit without |
|
1148 |
-toggling Tor state or requiring user interaction. Currently they exist as their |
|
1149 |
-own individual tests, but conceivably a single "Tor Safety Check" |
|
1150 |
-page can be devised that contains all of these attacks. |
|
1151 |
-All of these tests are currently known to pass, but that does not mean that |
|
1152 |
-consolidating them into an easy to run test page is pointless. Torbutton is a |
|
1153 |
-complicated piece of software. During development, changes to one component |
|
1154 |
-can affect a whole slough of unrelated features. Having easy-to-verify |
|
1155 |
-comprehensive test pages would make it much easier to fix other issues as they |
|
1156 |
-present themselves without introducing regressions. |
|
1157 |
- |
|
1158 |
- </p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id3007076"></a>Java and Plugin Decloaking</h4></div></div></div><p> |
|
1159 |
-As <a class="link" href="#plugins" title="5.2. Disable plugins on Tor Usage (crucial)">mentioned above</a>, Java and plugins <a class="ulink" href="http://java.sun.com/j2se/1.5.0/docs/api/java/net/class-use/NetworkInterface.html" target="_top">can query</a> the <a class="ulink" href="http://www.rgagnon.com/javadetails/java-0095.html" target="_top">local IP |
|
1160 |
-address</a> and report it back to the |
|
1161 |
-remote site. They can also <a class="ulink" href="http://www.metasploit.com/research/projects/decloak/" target="_top">bypass proxy settings</a> and directly connect to a |
|
1162 |
-remote site without Tor. Every browser plugin we have tested with Firefox has |
|
1163 |
-some form of network capability, and every one ignores proxy settings or worse - only |
|
1164 |
-partially obeys them. This includes but is not limited to: |
|
1165 |
-QuickTime, Windows Media Player, RealPlayer, mplayerplug-in, AcroRead, and |
|
1166 |
-Flash. In addition, |
|
1167 |
-<a class="ulink" href="http://www.janusvm.com/goldy/pdf/" target="_top">issues have been |
|
1168 |
-discovered</a> with the browsers handling of |
|
1169 |
-<a class="ulink" href="https://bugzilla.mozilla.org/show_bug.cgi?id=401296" target="_top">direct links to plugin-handled |
|
1170 |
-content</a> as well as meta-refreshes to plugin content. To make matters |
|
1171 |
-worse, <a class="ulink" href="http://www.janusvm.com/goldy/side-channels/side-channels.html" target="_top">externally |
|
1172 |
-handled mime types and urls</a> can also cause direct non-Tor connections |
|
1173 |
-as well. |
|
1174 |
- </p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id3007174"></a>History Disclosure attacks</h4></div></div></div><p> |
|
1175 |
-The browser's history can also be queried by a remote site to inspect for |
|
1176 |
-Google queries, visits to sites that contain usernames in the URLs, or |
|
1177 |
-other anonymity set reducing information. This can be done by either |
|
1178 |
-<a class="ulink" href="http://gemal.dk/browserspy/css.html" target="_top">Javascript</a>, or by |
|
1179 |
-<a class="ulink" href="http://ha.ckers.org/weird/CSS-history.cgi" target="_top">CSS</a> without any scripting involved. |
|
1180 |
- |
|
1181 |
- </p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id3007200"></a>User agent, extension, resolution and OS information</h4></div></div></div><p> |
|
1182 |
- |
|
1183 |
-As mentioned above, these properties can be combined to greatly reduce |
|
1184 |
-anonymity set and even build a potentially <a class="link" href="#fingerprinting">globally unique identifier</a> for |
|
1185 |
-users. <a class="ulink" href="http://0x000000.com/index.php?i=520&bin=1000001000" target="_top">Examples of this |
|
1186 |
-in the wild</a> rely on <a class="ulink" href="http://gemal.dk/browserspy/basic.html" target="_top">user agent and OS |
|
1187 |
-information</a> as well as <a class="ulink" href="http://pseudo-flaw.net/content/tor/torbutton/" target="_top">chrome disclosure |
|
1188 |
-information</a>. |
|
1189 |
- |
|
1190 |
- </p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id3007238"></a>Timezone and Location Information</h4></div></div></div><p> |
|
1191 |
-<a class="ulink" href="http://gemal.dk/browserspy/date.html" target="_top">Time and Timezone</a> |
|
1192 |
-should be obscured to be GMT-only, and by the browser should present itself |
|
1193 |
-with an US English locale. |
|
1194 |
- </p></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3007257"></a>7.2. Multi-state testing</h3></div></div></div><p> |
|
1195 |
- |
|
1196 |
-The tests in this section are geared towards a page that would instruct the |
|
1197 |
-user to toggle their Tor state after the fetch and perform some operations: |
|
1198 |
-mouseovers, stray clicks, and potentially reloads. |
|
1199 |
- |
|
1200 |
- </p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id3007269"></a>Cookies and Cache Correlation</h4></div></div></div><p> |
|
1201 |
-The most obvious test is to set a cookie, ask the user to toggle tor, and then |
|
1202 |
-have them reload the page. The cookie should no longer be set if they are |
|
1203 |
-using the default Torbutton settings. In addition, it is possible to leverage |
|
1204 |
-the cache to <a class="ulink" href="http://crypto.stanford.edu/sameorigin/safecachetest.html" target="_top">store unique |
|
1205 |
-identifiers</a>. The default settings of Torbutton should also protect |
|
1206 |
-against these from persisting across Tor Toggle. |
|
1207 |
- |
|
1208 |
- </p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id3007292"></a>Javascript timers and event handlers</h4></div></div></div><p> |
|
1209 |
- |
|
1210 |
-Javascript can set timers and register event handlers in the hopes of fetching |
|
1211 |
-URLs after the user has toggled Torbutton. |
|
1212 |
- </p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id3007305"></a>CSS Popups and non-script Dynamic Content</h4></div></div></div><p> |
|
1213 |
- |
|
1214 |
-Even if Javascript is disabled, CSS is still able to |
|
1215 |
-<a class="ulink" href="http://www.tjkdesign.com/articles/css%20pop%20ups/" target="_top">create popup-like |
|
1216 |
-windows</a> |
|
1217 |
-via the 'onmouseover' CSS attribute, which can cause arbitrary browser |
|
1218 |
-activity as soon as the mouse enters into the content window. It is also |
|
1219 |
-possible for meta-refresh tags to set timers long enough to make it likely |
|
1220 |
-that the user has toggled Tor before fetching content. |
|
1221 |
- |
|
1222 |
- </p></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="id3007328"></a>7.3. Active testing (aka How to Hack Torbutton)</h3></div></div></div><p> |
|
1223 |
- |
|
1224 |
-The idea behind active testing is to discover vulnerabilities in Torbutton to |
|
1225 |
-bypass proxy settings, run script in an opposite Tor state, store unique |
|
1226 |
-identifiers, leak location information, or otherwise violate <a class="link" href="#requirements" title="1.2. Torbutton Requirements">its requirements</a>. Torbutton has ventured out |
|
1227 |
-into a strange and new security landscape. It depends on Firefox mechanisms |
|
1228 |
-that haven't necessarily been audited for security, certainly not for the |
|
1229 |
-threat model that Torbutton seeks to address. As such, it and the interfaces |
|
1230 |
-it depends upon still need a 'trial by fire' typical of new technologies. This |
|
1231 |
-section of the document was written with the intention of making that period |
|
1232 |
-as fast as possible. Please help us get through this period by considering |
|
1233 |
-these attacks, playing with them, and reporting what you find (and potentially |
|
1234 |
-submitting the test cases back to be run in the standard batch of Torbutton |
|
1235 |
-tests. |
|
1236 |
- |
|
1237 |
- </p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id3007358"></a>Some suggested vectors to investigate</h4></div></div></div><p> |
|
1238 |
- </p><div class="itemizedlist"><ul type="disc"><li>Strange ways to register Javascript <a class="ulink" href="http://en.wikipedia.org/wiki/DOM_Events" target="_top">events</a> and <a class="ulink" href="http://www.devshed.com/c/a/JavaScript/Using-Timers-in-JavaScript/" target="_top">timeouts</a> should |
|
1239 |
-be verified to actually be ineffective after Tor has been toggled.</li><li>Other ways to cause Javascript to be executed after |
|
1240 |
-<span class="command"><strong>javascript.enabled</strong></span> has been toggled off.</li><li>Odd ways to attempt to load plugins. Kyle Williams has had |
|
1241 |
-<a class="ulink" href="http://www.janusvm.com/goldy/pdf/" target="_top">some |
|
1242 |
-success</a> with direct loads/meta-refreshes of plugin-handled URLs.</li><li>The Date and Timezone hooks should be verified to work with |
|
1243 |
-crazy combinations of iframes, nested iframes, iframes in frames, frames in |
|
1244 |
-iframes, and popups being loaded and |
|
1245 |
-reloaded in rapid succession, and/or from one another. Think race conditions and deep, |
|
1246 |
-parallel nesting, involving iframes from both <a class="ulink" href="http://en.wikipedia.org/wiki/Same_origin_policy" target="_top">same-origin and |
|
1247 |
-non-same-origin</a> domains.</li><li>In addition, there may be alternate ways and other |
|
1248 |
-methods to query the timezone, or otherwise use some of the Date object's |
|
1249 |
-methods in combination to deduce the timezone offset. Of course, the author |
|
1250 |
-tried his best to cover all the methods he could foresee, but it's always good |
|
1251 |
-to have another set of eyes try it out.</li><li>Similarly, is there any way to confuse the <a class="link" href="#contentpolicy" title="@torproject.org/cssblocker;1 - components/cssblocker.js">content policy</a> |
|
1252 |
-mentioned above to cause it to allow certain types of page fetches? For |
|
1253 |
-example, it was recently discovered that favicons are not fetched by the |
|
1254 |
-content, but the chrome itself, hence the content policy did not look up the |
|
1255 |
-correct window to determine the current Tor tag for the favicon fetch. Are |
|
1256 |
-there other things that can do this? Popups? Bookmarklets? Active bookmarks? </li><li>Alternate ways to store and fetch unique identifiers. For example, <a class="ulink" href="http://developer.mozilla.org/en/docs/DOM:Storage" target="_top">DOM Storage</a> |
|
1257 |
-caught us off guard. |
|
1258 |
-It was |
|
1259 |
-also discovered by <a class="ulink" href="http://pseudo-flaw.net" target="_top">Gregory |
|
1260 |
-Fleischer</a> that <a class="ulink" href="http://pseudo-flaw.net/content/tor/torbutton/" target="_top">content window access to |
|
1261 |
-chrome</a> can be used to build <a class="link" href="#fingerprinting">unique |
|
1262 |
-identifiers</a>. |
|
1263 |
-Are there any other |
|
1264 |
-arcane or experimental ways that Firefox provides to create and store unique |
|
1265 |
-identifiers? Or perhaps unique identifiers can be queried or derived from |
|
1266 |
-properties of the machine/browser that Javascript has access to? How unique |
|
1267 |
-can these identifiers be? |
|
1268 |
- </li><li>Is it possible to get the browser to write some history to disk |
|
1269 |
-(aside from swap) that can be retrieved later? By default, Torbutton should |
|
1270 |
-write no history, cookie, or other browsing activity information to the |
|
1271 |
-harddisk.</li><li>Do popup windows make it easier to break any of the above |
|
1272 |
-behavior? Are javascript events still canceled in popups? What about recursive |
|
1273 |
-popups from Javascript, data, and other funky URL types? What about CSS |
|
1274 |
-popups? Are they still blocked after Tor is toggled?</li><li>Chrome-escalation attacks. The interaction between the |
|
1275 |
-Torbutton chrome Javascript and the client content window javascript is pretty |
|
1276 |
-well-defined and carefully constructed, but perhaps there is a way to smuggle |
|
1277 |
-javascript back in a return value, or otherwise inject network-loaded |
|
1278 |
-javascript into the chrome (and thus gain complete control of the browser). |
|
1279 |
-</li></ul></div><p> |
|
1280 |
- |
|
1281 |
- </p></div></div></div></div></body></html> |
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