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volunteer.wml

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# Revision: $Revision$

#include "head.wmi" TITLE="Tor: Volunteer"

<h2>Three things everyone can do now:</h2>
<ol>
<li>Please consider <a href="<page docs/tor-doc-relay>">running
a relay</a> to help the Tor network grow.</li>
<li>Tell your friends! Get them to run relays. Get them to run hidden
services. Get them to tell their friends.</li>
<li>We are looking for funding and sponsors. If you like Tor's goals, please
 <a href="<page donate>">take a moment to donate to support further
 Tor development</a>. Also, if you know any
 companies, NGOs, agencies, or other organizations that want communications
 security, let them know about us.</li>
</ol>

<a id="Usability"></a>
<h2><a class="anchor" href="#Usability">Supporting Applications</a></h2>
<ol>
<li>We need more good ways to intercept DNS requests so they don't "leak" their
request to a local observer while we're trying to be anonymous. (This
happens because the application does the DNS resolve before going to
the SOCKS proxy.)</li>
<li>Tsocks/dsocks items:
<ul>
<li>We need to <a
href="https://wiki.torproject.org/noreply/TheOnionRouter/TSocksPatches">apply
all our tsocks patches</a> and maintain a new fork. We'll host it if
you want.</li>
<li>We should patch Dug Song's "dsocks" program to use Tor's
mapaddress commands from the controller interface, so we
don't waste a whole round-trip inside Tor doing the resolve before
connecting.</li>
<li>We need to make our torify script detect which of tsocks or
dsocks is installed, and call them appropriately. This probably means
unifying their interfaces, and might involve sharing code between them
or discarding one entirely.</li>
</ul>
</li>
<li>People running relays tell us they want to have one BandwidthRate
during some part of the day, and a different BandwidthRate at other
parts of the day. Rather than coding this inside Tor, we should have a
little script that speaks via the <a href="<page gui/index>">Tor
Controller Interface</a>, and does a setconf to change the bandwidth
rate. There is one for Unix and Mac already (it uses bash and cron),
but Windows users still need a solution.
</li>
<li>Tor can <a
href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#ChooseEntryExit">exit
the Tor network from a particular exit node</a>, but we should be able
to specify just a country and have something automatically pick. The
best bet is to fetch Blossom's directory also, and run a local Blossom
client that fetches this directory securely (via Tor and checking its
signature), intercepts <tt>.country.blossom</tt> hostnames, and does
the right thing.</li>
<li>Speaking of geolocation data, somebody should draw a map of the Earth
with a pin-point for each Tor relay. Bonus points if it updates as the
network grows and changes. Unfortunately, the easy ways to do this involve
sending all the data to Google and having them draw the map for you. How
much does this impact privacy, and do we have any other good options?</li>
</ol>

<a id="Documentation"></a>
<h2><a class="anchor" href="#Documentation">Documentation</a></h2>
<ol>
<li>Please help Matt Edman with the documentation and how-tos for his
Tor controller,
<a href="http://vidalia-project.net/">Vidalia</a>.</li>
<li>Evaluate and document
<a href="https://wiki.torproject.org/wiki/TheOnionRouter/TorifyHOWTO">our
list of programs</a> that can be configured to use Tor.</li>
<li>We need better documentation for dynamically intercepting
connections and sending them through Tor. tsocks (Linux), dsocks (BSD),
and freecap (Windows) seem to be good candidates, as would better
use of our new TransPort feature.</li>
<li>We have a huge list of <a href="https://wiki.torproject.org/noreply/TheOnionRouter/SupportPrograms">potentially useful
programs that interface to Tor</a>. Which ones are useful in which
situations? Please help us test them out and document your results.</li>
<li>Help translate the web page and documentation into other
languages. See the <a href="<page translation>">translation
guidelines</a> if you want to help out. We especially need Arabic or
Farsi translations, for the many Tor users in censored areas.</li>
</ol>

<a id="Coding"></a>
<a id="Summer"></a>
<a id="Projects"></a>
<h2><a class="anchor" href="#Projects">Good Coding Projects</a></h2>

You may find some of these projects to be good <a href="<page
gsoc>">Google Summer of Code 2008</a> ideas. We have labelled each idea
with how useful it would be to the overall Tor project
(priority), how much work we expect it would be (effort level), how much
clue you should start with (skill level), and which of our <a href="<page
people>#Core">core developers</a> would be good mentors.

<ol>

<li>
Tor/Polipo/Vidalia Auto-Update Framework
 
Priority: High
 
Effort Level: High
 
Skill Level: High
 
Likely Mentors: Matt, Jacob
 
We're in need of a good authenticated-update framework.
Vidalia already has the ability to notice when the user is running an
outdated or unrecommended version of Tor, using signed statements inside
the Tor directory information. Currently, Vidalia simply pops
up a little message box that lets the user know they should manually
upgrade. The goal of this project would be to extend Vidalia with the
ability to also fetch and install the updated Tor software for the
user. We should do the fetches via Tor when possible, but also fall back
to direct fetches in a smart way. Time permitting, we would also like
to be able to update other
applications included in the bundled installers, such as Polipo and
Vidalia itself.
 
To complete this project, the student will first need to first investigate
the existing auto-update frameworks (e.g., Sparkle on OS X) to evaluate
their strengths, weaknesses, security properties, and ability to be
integrated into Vidalia. If none are found to be suitable, the student
will design their own auto-update framework, document the design, and
then discuss the design with other developers to assess any security
issues. The student will then implement their framework (or integrate
an existing one) and test it.
 
A student undertaking this project should have good C++ development
experience. Previous experience with Qt is helpful, but not required. The
student should also have a good understanding of common security
practices, such as package signature verification. Good writing ability
is also important for this project, since a vital step of the project
will be producing a design document for others to review and discuss
with the student prior to implementation.
</li>

<li>
An Improved and More Usable Network Map in Vidalia
 
Priority: Medium
 
Effort Level: Medium
 
Skill Level: Medium to High
 
Likely Mentors: Matt
 
One of Vidalia's existing features is a network map that shows the user
the approximate geographic location of relays in the Tor network and
plots the paths the user's traffic takes as it is tunneled through the
Tor network. The map is currently not very interactive and has rather
poor graphics. Instead, we would like to leverage KDE's Marble widget
that gives us a better quality map and enables improved interactivity,
such as allowing the user to click on individual relays or circuits to
display additional information. We might also consider adding the ability
for users to click on a particular relay or a country containing one or
more Tor exit relays and say, "I want my connections to foo.com to exit
from here."
 
This project will first involve the student getting familiar with Vidalia
and the Marble widget's API. The student will then integrate the widget
into Vidalia and customize Marble to be better suited for our application,
such as making circuits clickable, storing cached map data in Vidalia's
own data directory, and customizing some of the widget's dialogs.
 
A student undertaking this project should have good C++ development
experience. Previous experience with Qt and CMake is helpful, but not
required.
</li>

<li>
Better Debian Packaging for Tor+Vidalia
 
Priority: High
 
Effort Level: Medium
 
Skill Level: Medium
 
Likely Mentors: Peter, Matt
 
Vidalia currently doesn't play nicely on Debian and Ubuntu with the
default Tor packages. The current Tor packages automatically start Tor
as a daemon running as the debian-tor user and (sensibly) do not have a
<a href="<svnsandbox>doc/spec/control-spec.txt">ControlPort</a> defined
in the default torrc. Consequently, Vidalia will try
to start its own Tor process since it could not connect to the existing
Tor, and Vidalia's Tor process will then exit with an error message
the user likely doesn't understand since Tor cannot bind its listening
ports &mdash; they're already in use by the original Tor daemon.
 
The current solution involves either telling the user to stop the
existing Tor daemon and let Vidalia start its own Tor process, or
explaining to the user how to set a control port and password in their
torrc. A better solution on Debian would be to use Tor's ControlSocket,
which allows Vidalia to talk to Tor via a Unix domain socket, and could
possibly be enabled by default in Tor's Debian packages. Vidalia can
then authenticate to Tor using filesystem-based (cookie) authentication
if the user running Vidalia is also in the debian-tor group.
 
This project will first involve adding support for Tor's ControlSocket
to Vidalia. The student will then develop and test Debian and Ubuntu
packages for Vidalia that conform to Debian's packaging standards and
make sure they work well with the existing Tor packages. We can also
set up an apt repository to host the new Vidalia packages.
 
The next challenge would be to find an intuitive usable way for Vidalia
to be able to change Tor's configuration (torrc) even though it is
located in <code>/etc/tor/torrc</code> and thus immutable. The best
idea we've come up with so far is to feed Tor a new configuration via
the ControlSocket when Vidalia starts, but that's bad because Tor starts
each boot with a different configuration than the user wants. The second
best idea
we've come up with is for Vidalia to write out a temporary torrc file
and ask the user to manually move it to <code>/etc/tor/torrc</code>,
but that's bad because users shouldn't have to mess with files directly.
 
A student undertaking this project should have prior knowledge of
Debian package management and some C++ development experience. Previous
experience with Qt is helpful, but not required.
</li>

<li>
Tor Controller Status Event Interface
 
Priority: Medium
 
Effort Level: Medium
 
Skill Level: Medium
 
Likely Mentors: Matt, Roger
 
There are a number of status changes inside Tor of which the user may need
to be informed. For example, if the user is trying to set up his Tor as a
relay and Tor decides that its ports are not reachable from outside
the user's network, we should alert the user. Currently, all the user
gets is a couple log messages in Vidalia's 'message log' window, which they
likely never see since they don't receive a notification that something
has gone wrong. Even if the user does actually look at the message log,
most of the messages make little sense to the novice user.
 
Tor has the ability to inform Vidalia of many such status changes, and
we recently implemented support for a couple of these events. Still,
there are many more status events the user should be informed of and we
need a better UI for actually displaying them to the user.
 
The goal of this project then is to design and implement a UI for
displaying Tor status events to the user. For example, we might put a
little badge on Vidalia's tray icon that alerts the user to new status
events they should look at. Double-clicking the icon could bring up a
dialog that summarizes recent status events in simple terms and maybe
suggests a remedy for any negative events if they can be corrected by
the user. Of course, this is just an example and the student is free to
suggest another approach.
 
A student undertaking this project should have good UI design and layout
and some C++ development experience. Previous experience with Qt and 
Qt's Designer will be very helpful, but are not required. Some
English writing ability will also be useful, since this project will
likely involve writing small amounts of help documentation that should
be understandable by non-technical users. Bonus points for some graphic
design/Photoshop fu, since we might want/need some shiny new icons too.
</li>

<li>
Translation Wiki
 
Priority: High
 
Effort Level: Medium
 
Skill Level: Medium
 
Likely Mentors: Jacob
 
We need a way to edit and translate sections of the website. Currently
the website is made up of a bunch of <a href="<svnsandbox>website/en/">wml
files</a>, and <a href="<page translation>">translators</a> fetch these
wml files, translate them in an editor, and either send us the translation
or use svn to commit them back. The current "cost" of publication of
website changes is quite high even for English language users. For a
single word change or any type of
minor change, the page may never be corrected or translated. It would
be nice to have a wiki that was specifically geared towards translation
and would somehow track the upstream (English) versions to indicate when
a fresh translation is needed, like our current
<a href="<page translation-status>">translation status page</a>. This
seems mostly like a job for a wiki
integrator or wiki software author. Certainly the person would need to
be interested in human languages and translation. They should at least
be minimally familiar with what Tor is; but they would not have to interact
with the software, only the documentation and the website.
</li>

<li>
Improvements on our active browser configuration tester - 
<a href="https://check.torproject.org/">https://check.torproject.org/</a>
 
Priority: Medium
 
Effort Level: Low
 
Skill Level: Low to Medium
 
Likely Mentors: Jacob, Steven
 
We currently have a functional web page to detect if Tor is working. It
has a few places where it falls short. It requires improvements with
regard to default languages and functionality. It currently only responds
in English. In addition, it is a hack of a perl script that should have
never seen the light of day. It should probably be rewritten in python
with multi-lingual support in mind. It currently uses the <a
href="http://exitlist.torproject.org/">Tor DNS exit list</a>
and should continue to do so in the future. It currently result in certain
false positives and these should be discovered, documented, and fixed
where possible. Anyone working on this project should be interested in
DNS, basic perl or preferably python programming skills, and will have
to interact minimally with Tor to test their code.
 
If you want to make the project more exciting
and involve more design and coding, take a look at <a
href="<svnsandbox>doc/spec/proposals/131-verify-tor-usage.txt">proposal
131-verify-tor-usage.txt</a>.
</li>

<li>
Improvements on our DNS Exit List service - 
<a href="http://exitlist.torproject.org/">http://exitlist.torproject.org/</a>
 
Priority: Medium
 
Effort Level: Low
 
Skill Level: Low
 
Likely Mentors: Jacob, Tup
 
The <a href="http://p56soo2ibjkx23xo.onion/">exitlist software</a>
is written by our fabulous anonymous
contributer Tup. It's a DNS server written in Haskell that supports part of our <a
href="https://www.torproject.org/svn/trunk/doc/contrib/torel-design.txt">exitlist
design document</a>. Currently, it is functional and it is used by
check.torproject.org and other users. The issues that are outstanding
are mostly aesthetic. This wonderful service could use a much better
website using the common Tor theme. It would be best served with better
documentation for common services that use an RBL. It could use more
publicity. A person working on this project should be interested in DNS,
basic RBL configuration for popular services, and writing documentation.
The person would require minimal Tor interaction &mdash; testing their
own documentation at the very least. Furthermore, it would be useful
if they were interested in Haskell and wanted to implement more of the
torel-design.txt suggestions.
</li>

<li>
Testing integration of Tor with web browsers for our end users
 
Priority: Medium
 
Effort Level: Medium
 
Skill Level: Medium
 
Likely Mentors: Jacob, Mike, Greg
 
The Tor project currently lacks a solid test suite to ensure that a
user has a properly and safely configured web browser. It should test for as
many known issues as possible. It should attempt to decloak the
user in any way possible. Two current webpages that track these
kinds of issues are run by Greg Fleischer and HD Moore. Greg keeps a nice <a
href="http://pseudo-flaw.net/tor/torbutton/">list of issues along
with their proof of concept code, bug issues, etc</a>. HD Moore runs
the <a href="http://metasploit.com/research/projects/decloak/">metasploit
decloak website</a>. A student interested in defending Tor could start
by collecting as many workable and known methods for decloaking a
Tor user. (<a href="https://torcheck.xenobite.eu/">This page</a> may
be helpful as a start.) The student should be familiar with the common
pitfalls but
possibly have new methods in mind for implementing decloaking issues. The
website should ensure that it tells a user what their problem is. It
should help them to fix the problem or direct them to the proper support
channels. The student should be closely familiar with using Tor and how
to prevent Tor information leakage.
</li>

<li>
Improving Tor's ability to resist censorship
 
Priority: High
 
Effort Level: High
 
Skill Level: High
 
Likely Mentors: Nick
 
The Tor 0.2.0.x series makes <a
href="<svnsandbox>doc/design-paper/blocking.html">significant
improvements</a> in resisting national and organizational censorship.
But Tor still needs better mechanisms for some parts of its
anti-censorship design. For example, current Tors can only listen on a
single address/port combination at a time. There's
<a href="<svnsandbox>doc/spec/proposals/118-multiple-orports.txt">a
proposal to address this limitation</a> and allow clients to connect
to any given Tor on multiple addresses and ports, but it needs more
work. Another anti-censorship project (far more difficult) is to try
to make Tor more scanning-resistant. Right now, an adversary can identify
<a href="<svnsandbox>doc/spec/proposals/125-bridges.txt">Tor bridges</a>
just by trying to connect to them, following the Tor protocol, and 
seeing if they respond. To solve this, bridges could
<a href="<svnsandbox>doc/design-paper/blocking.html#tth_sEc9.3">act like
webservers</a> (HTTP or HTTPS) when contacted by port-scanning tools,
and not act like bridges until the user provides a bridge-specific key.
 
This project involves a lot of research and design. One of the big
challenges will be identifying and crafting approaches that can still
resist an adversary even after the adversary knows the design, and
then trading off censorship resistance with usability and robustness.
</li>

<li>
Libevent and Tor integration improvements
 
Priority: Medium
 
Effort Level: High
 
Skill Level: Medium to High
 
Likely Mentors: Nick
 
Tor should make better use of the more recent features of Niels
Provos's <a href="http://monkey.org/~provos/libevent/">Libevent</a>
library. Tor already uses Libevent for its low-level asynchronous IO
calls, and could also use Libevent's increasingly good implementations
of network buffers and of HTTP. This wouldn't be simply a matter of
replacing Tor's internal calls with calls to Libevent: instead, we'll
need to refactor Tor to use Libevent calls that do not follow the
same models as Tor's existing backends. Also, we'll need to add
missing functionality to Libevent as needed &mdash; most difficult likely
will be adding OpenSSL support on top of Libevent's buffer abstraction.
Also tricky will be adding rate-limiting to Libevent.
</li>

<li>
Tuneup Tor!
 
Priority: Medium
 
Effort Level: Medium
 
Skill Level: Medium to High
 
Likely Mentors: Nick, Roger, Mike
 
Right now, Tor relays measure and report their own bandwidth, and Tor
clients choose which relays to use in part based on that bandwidth.
This approach is vulnerable to
<a href="http://freehaven.net/anonbib/#bauer:wpes2007">attacks where
relays lie about their bandwidth</a>;
to address this, Tor currently caps the maximum bandwidth
it's willing to believe any relay provides. This is a limited fix, and
a waste of bandwidth capacity to boot. Instead,
Tor should possibly measure bandwidth in a more distributed way, perhaps
as described in the
<a href="http://freehaven.net/anonbib/author.html#snader08">"A Tune-up for
Tor"</a> paper
by Snader and Borisov. A student could use current testing code to
double-check this paper's findings and verify the extent to which they
dovetail with Tor as deployed in the wild, and determine good ways to
incorporate them into their suggestions Tor network without adding too
much communications overhead between relays and directory
authorities.
</li>

<li>
Improve our unit testing process
 
Priority: Medium
 
Effort Level: Medium
 
Skill Level: Medium
 
Likely Mentors: Nick
 
Tor needs to be far more tested. This is a multi-part effort. To start
with, our unit test coverage should rise substantially, especially in
the areas outside the utility functions. This will require significant
refactoring of some parts of Tor, in order to dissociate as much logic
as possible from globals.
 
Additionally, we need to automate our performance testing. We've got
buildbot to automate our regular integration and compile testing already
(though we need somebody to set it up on Windows),
but we need to get our network simulation tests (as built in TorFlow: see
the "Tor Node Scanner improvements" item)
updated for more recent versions of Tor, and designed to launch a test
network either on a single machine, or across several, so we can test
changes in performance on machines in different roles automatically.
</li>

<li>
Help revive an independent Tor client implementation
 
Priority: Medium
 
Effort Level: High
 
Skill Level: Medium to High
 
Likely Mentors: Karsten, Nick
 
Reanimate one of the approaches to implement a Tor client in Java,
e.g. the <a href="http://onioncoffee.sourceforge.net/">OnionCoffee
project</a>, and make it run on <a
href="http://code.google.com/android/">Android</a>. The first step
would be to port the existing code and execute it in an Android
environment. Next, the code should be updated to support the newer Tor
protocol versions like the <a href="<svnsandbox>doc/spec/dir-spec.txt">v3
directory protocol</a>. Further, support for requesting or even
providing Tor hidden services would be neat, but not required.
 
The student should be able to understand and write new Java code, including
a Java cryptography API. Being able to read C code would be helpful,
too. The student should be willing to read the existing documentation,
implement code based on it, and refine the documentation
when things are underdocumented. This project is mostly about coding and
to a small degree about design.
</li>

<li>
Automatic system tests and automatically starting private Tor networks
 
Priority: Medium
 
Effort Level: Medium
 
Skill Level: Medium
 
Likely Mentors: Karsten, Nick, Roger
 
Write a tool that runs automatic system tests in addition
to the existing unit tests. The Java-based Tor simulator <a
href="https://tor-svn.freehaven.net/svn/puppetor/trunk/">PuppeTor</a>
might be a good start for starting up a private Tor network, using it
for a while, and verifying that at least parts of it are working. This
project requires to conceive a blueprint for performing system tests
of private Tor networks, before starting to code. Typical types of
tests range from performing single requests over the private network to
manipulating exchanged messages and see if nodes handle corrupt messages
appropriately.
 
The student should be able to obtain a good understanding
of how Tor works and what problems and bugs could arise to design good
test cases. Understanding the existing Tor code structure and documentation is
vital. If PuppeTor is used, the student should also be able to understand
and possibly extend an existing Java application. This project is partly
about design and partly about coding.
</li>

<li>
Bring moniTor to life
 
Priority: Medium
 
Effort Level: Medium
 
Skill Level: Low to Medium
 
Likely Mentors: Karsten, Jacob
 
Implement a <a href="http://www.ss64.com/bash/top.html">top-like</a>
management tool for Tor relays. The purpose of such a tool would be
to monitor a local Tor relay via its control port and include useful
system information of the underlying machine. When running this tool, it
would dynamically update its content like top does for Linux processes.
<a href="http://archives.seul.org/or/dev/Jan-2008/msg00005.html">This
or-dev post</a> might be a good first read.
 
The student should be familiar
with or willing to learn about administering a Tor relay and configuring
it via its control port. As an initial prototype is written in Python,
some knowledge about writing Python code would be helpful, too. This
project is one part about identifying requirements to such a
tool and designing its interface, and one part lots of coding.
</li>

<li>
Tor Exit Scanner improvements
 
Priority: High
 
Effort Level: High
 
Skill Level: High
 
Likely Mentors: Mike
 
The Tor exit node scanner 'SoaT', part of the <a
href="<svnsandbox>torflow/">Torflow project</a>, makes connections out
of each Tor exit node and compares the content it gets back with what it
"should" get back. The goal is to notice misconfigured, broken, and even
malicious exit relays. Alas, the code is
currently written in rather rickety perl and relies on MD5sums of
entire documents in order to determine if exit nodes are modifying
content. The problem with this is threefold: 1) Perl sucks at life.
2) The scanner can't verify pages that are dynamic, and attackers can
focus malicious content injection on only those dynamic pages. 3)
Pages change after a while (or based on GeoIP) and begin generating
false positives.
 
Ideally, soat.pl would be reimplemented in a sane language with a
robust html parser library (since the rest of Torflow is in Python
that would be nice, but it is not required), and calculate signatures only for
tags and content likely to be targeted by a malicious attacker (script
tags, object links, images, css). It should also be robust in the face of
changes to content outside of Tor, and ultimately even GeoIP localized
content.
 
This scanner would likely be run by the Directory Authorities and
report its results to the control port via the AuthDirBadExit config
setting.
 
</li>

<li>
Tor Node Scanner improvements
 
Priority: High
 
Effort Level: Medium to High
 
Skill Level: Medium to High
 
Likely Mentors: Mike
 
Similar to the exit scanner (or perhaps even during exit scanning),
statistics can be gathered about the reliability of nodes. Nodes that
fail too high a percentage of their circuits should not be given
Guard status. Perhaps they should have their reported bandwidth
penalized by some ratio as well, or just get marked as Invalid. In
addition, nodes that exhibit a very low average stream capacity but
advertise a very high node bandwidth can also be marked as Invalid.
Much of this statistics gathering is already done, it just needs to be
transformed into something that can be reported to the Directory
Authorities to blacklist/penalize nodes in such a way that clients
will listen.
 
In addition, these same statistics can be gathered about the traffic
through a node. Events can be added to the <a
href="https://www.torproject.org/svn/torctl/doc/howto.txt">Tor Control
Protocol</a> to
report if a circuit extend attempt through the node succeeds or fails, and
passive statistics can be gathered on both bandwidth and reliability
of other nodes via a node-based monitor using these events. Such a
scanner would also report information on oddly-behaving nodes to
the Directory Authorities, but a communication channel for this
currently does not exist and would need to be developed as well.
</li>

<li>
Help track the overall Tor Network status
 
Priority: High
 
Effort Level: Medium
 
Skill Level: Medium
 
Likely Mentors: Roger, Nick, Mike
 
It would be great to set up an automated system for tracking network
health over time, graphing it, etc. Part of this project would involve
inventing better metrics for assessing network health and growth. Is the
average uptime of the network increasing? How many relays are qualifying
for Guard status this month compared to last month? What's the turnover
in terms of new relays showing up and relays shutting off? Periodically
people collect brief snapshots, but where it gets really interesting is
when we start tracking data points over time.
 
Data could be collected from the "Tor Node Scanner" item above, from
the server descriptors that each relay publishes, and from other
sources. Results over time could be integrated into one of the <a
href="https://torstatus.blutmagie.de/">Tor Status</a> web pages, or be
kept separate. Speaking of the Tor Status pages, take a look at Roger's
<a href="http://archives.seul.org/or/talk/Jan-2008/msg00300.html">Tor
Status wish list</a>.
</li>

<li>
Tor path selection improvements
 
Priority: High
 
Effort Level: Low to Medium
 
Skill Level: High
 
Likely Mentors: Roger, Nick, Mike
 
Some simple improvements can be made to Tor's path selection to vastly
improve Tor speed. For instance, some of the (unofficial) <a
href="http://wiki.noreply.org/noreply/TheOnionRouter/FireFoxTorPerf">Tor
Performance Recommendations</a> on the wiki are to increase the number of
guards and decrease the CircuitBuildTimeout. Ideally, the client would
<a href="http://archives.seul.org/or/talk/Feb-2008/msg00012.html">learn
these values by gathering statistics on circuit construction
time</a> (and/or using values gained from Torflow), and set the timeouts
low enough such that some high percentile (75%, 90%, 1-stddev?) of
circuits succeed, yet extremely slow nodes are avoided. This would
involve some statistics gathering+basic research, and some changes to 
Tor path selection code.
 
In addition, to improve path security, some elements from the <a
href="http://www.torproject.org/svn/trunk/doc/spec/proposals/115-two-hop-paths.txt">Two
Hop Paths proposal</a> could be done as part of this (since it will
likely touch the same code anyways), regardless of the adoption of
that proposal. In particular, clients probably should avoid guards that
seem to fail an excessive percentage of their circuits through them,
and non-firewalled clients should issue a warning if they are only able
to connect to a limited set of guard nodes. See also
<a href="http://archives.seul.org/or/dev/Feb-2008/msg00003.html">this
or-dev post</a>.
</li>

<li>
Torbutton improvements
 
Priority: Medium
 
Effort Level: High
 
Skill Level: High
 
Likely Mentors: Mike
 
Torbutton has a number of improvements that can be made in the post-1.2
timeframe. Most of these are documented as feature requests in the <a
href="https://bugs.torproject.org/flyspray/index.php?tasks=all&project=5">Torbutton
flyspray section</a>. Good examples include: stripping off node.exit on http
headers, more fine-grained control over formfill blocking, improved referrer
spoofing based on the domain of the site (a-la <a
href="http://addons.mozilla.org/firefox/addon/4513">refspoof extension</a>),
tighter integration with Vidalia for reporting Tor status, a New Identity
button with Tor integration and multiple identity management, and anything
else you might think of.
 
This work would be independent coding in Javascript and the fun world of <a
href="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">XUL</a>,
with not too much involvement in the Tor internals.
</li>

<li>
Porting Polipo to Windows
 
Priority: Medium
 
Effort Level: Medium
 
Skill Level: Medium to High
 
Likely Mentors: Andrew, Steven, Roger
 
Help port <a
href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a> to
Windows. Example topics to tackle include:
1) handle spaces in path names and understand the filesystem
namespace &mdash; that is, where application data, personal data,
and program data typically reside in various versions of Windows. 2) the
ability to handle ipv6 communications. 3) the ability to asynchronously
query name servers, find the system nameservers, and manage netbios
and dns queries. 4) use native regex capabilities of Windows, rather
than using 3rd party GNU regex libraries. 5) manage events and buffers
natively (i.e. in Unix-like OSes, Polipo defaults to 25% of ram, in
Windows it's whatever the config specifies). 6) some sort of GUI config
and reporting tool, bonus if it has a systray icon with right clickable
menu options. Double bonus if it's cross-platform compatible.
</li>

<li>
Make our diagrams beautiful and automated
 
Priority: Medium
 
Effort Level: Low
 
Skill Level: Low
 
Likely Mentors: Andrew
 
We need a way to generate the website diagrams (for example, the "How
Tor Works" pictures on the <a href="<page overview>">overview page</a>
from source, so we can translate them as UTF-8 text rather than edit
them by hand with Gimp. We might want to
integrate this as an wml file so translations are easy and images are
generated in multiple languages whenever we build the website. See the
"Translation Wiki" idea above.
</li>

<li>
Improve the LiveCD offerings for the Tor community
 
Priority: Low
 
Effort Level: Low
 
Skill Level: Medium to High
 
Likely Mentors: Anonym, Jacob, Roger
 
How can we make the <a
href="http://anonymityanywhere.com/incognito/">Incognito LiveCD</a>
easier to maintain, improve, and document?
</li>

<li>
Bring up new ideas!
 
Don't like any of these? Look at the <a
href="<svnsandbox>doc/design-paper/roadmap-future.pdf">Tor development
roadmap</a> for more ideas.
</li>

</ol>

<h2><a class="anchor" href="#Coding">Coding and Design</a></h2>
<ol>
<li>Tor relays don't work well on Windows XP. On
Windows, Tor uses the standard <tt>select()</tt> system
call, which uses space in the non-page pool. This means
that a medium sized Tor relay will empty the non-page pool, <a
href="https://wiki.torproject.org/noreply/TheOnionRouter/WindowsBufferProblems">causing
havoc and system crashes</a>. We should probably be using overlapped IO
instead. One solution would be to teach <a
href="http://www.monkey.org/~provos/libevent/">libevent</a> how to use
overlapped IO rather than select() on Windows, and then adapt Tor to
the new libevent interface. Christian King made a
<a href="https://tor-svn.freehaven.net/svn/libevent-urz/trunk/">good
start</a> on this in the summer of 2007.</li>
<li>We need to actually start building our <a href="<page
documentation>#DesignDoc">blocking-resistance design</a>. This involves
fleshing out the design, modifying many different pieces of Tor, adapting
<a href="http://vidalia-project.net/">Vidalia</a> so it supports the
new features, and planning for deployment.</li>
<li>We need a flexible simulator framework for studying end-to-end
traffic confirmation attacks. Many researchers have whipped up ad hoc
simulators to support their intuition either that the attacks work
really well or that some defense works great. Can we build a simulator
that's clearly documented and open enough that everybody knows it's
giving a reasonable answer? This will spur a lot of new research.
See the entry <a href="#Research">below</a> on confirmation attacks for
details on the research side of this task &mdash; who knows, when it's
done maybe you can help write a paper or three also.</li>
<li>Tor 0.1.1.x and later include support for hardware crypto accelerators
via OpenSSL. Nobody has ever tested it, though. Does somebody want to get
a card and let us know how it goes?</li>
<li>Perform a security analysis of Tor with <a
href="http://en.wikipedia.org/wiki/Fuzz_testing">"fuzz"</a>. Determine
if there are good fuzzing libraries out there for what we want. Win fame by
getting credit when we put out a new release because of you!</li>
<li>Tor uses TCP for transport and TLS for link
encryption. This is nice and simple, but it means all cells
on a link are delayed when a single packet gets dropped, and
it means we can only reasonably support TCP streams. We have a <a
href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#TransportIPnotTCP">list
of reasons why we haven't shifted to UDP transport</a>, but it would
be great to see that list get shorter. We also have a proposed <a
href="<svnsandbox>doc/spec/proposals/100-tor-spec-udp.txt">specification
for Tor and
UDP</a> &mdash; please let us know what's wrong with it.</li>
<li>We're not that far from having IPv6 support for destination addresses
(at exit nodes). If you care strongly about IPv6, that's probably the
first place to start.</li>
</ol>

<a id="Research"></a>
<h2><a class="anchor" href="#Research">Research</a></h2>
<ol>
<li>The "website fingerprinting attack": make a list of a few
hundred popular websites, download their pages, and make a set of
"signatures" for each site. Then observe a Tor client's traffic. As
you watch him receive data, you quickly approach a guess about which
(if any) of those sites he is visiting. First, how effective is
this attack on the deployed Tor codebase? Then start exploring
defenses: for example, we could change Tor's cell size from 512
bytes to 1024 bytes, we could employ padding techniques like <a
href="http://freehaven.net/anonbib/#timing-fc2004">defensive dropping</a>,
or we could add traffic delays. How much of an impact do these have,
and how much usability impact (using some suitable metric) is there from
a successful defense in each case?</li>
<li>The "end-to-end traffic confirmation attack":
by watching traffic at Alice and at Bob, we can <a
href="http://freehaven.net/anonbib/#danezis:pet2004">compare
traffic signatures and become convinced that we're watching the same
stream</a>. So far Tor accepts this as a fact of life and assumes this
attack is trivial in all cases. First of all, is that actually true? How
much traffic of what sort of distribution is needed before the adversary
is confident he has won? Are there scenarios (e.g. not transmitting much)
that slow down the attack? Do some traffic padding or traffic shaping
schemes work better than others?</li>
<li>A related question is: Does running a relay/bridge provide additional
protection against these timing attacks? Can an external adversary that can't
see inside TLS links still recognize individual streams reliably? 
Does the amount of traffic carried degrade this ability any? What if the
client-relay deliberately delayed upstream relayed traffic to create a queue
that could be used to mimic timings of client downstream traffic to make it
look like it was also relayed? This same queue could also be used for masking
timings in client upstream traffic with the techniques from <a
href="http://www.freehaven.net/anonbib/#ShWa-Timing06">adaptive padding</a>,
but without the need for additional traffic. Would such an interleaving of
client upstream traffic obscure timings for external adversaries? Would the
strategies need to be adjusted for asymmetric links? For example, on
asymmetric links, is it actually possible to differentiate client traffic from
natural bursts due to their asymmetric capacity? Or is it easier than
symmetric links for some other reason?</li>
<li>The "routing zones attack": most of the literature thinks of
the network path between Alice and her entry node (and between the
exit node and Bob) as a single link on some graph. In practice,
though, the path traverses many autonomous systems (ASes), and <a
href="http://freehaven.net/anonbib/#feamster:wpes2004">it's not uncommon
that the same AS appears on both the entry path and the exit path</a>.
Unfortunately, to accurately predict whether a given Alice, entry,
exit, Bob quad will be dangerous, we need to download an entire Internet
routing zone and perform expensive operations on it. Are there practical
approximations, such as avoiding IP addresses in the same /8 network?</li>
<li>Other research questions regarding geographic diversity consider
the tradeoff between choosing an efficient circuit and choosing a random
circuit. Look at Stephen Rollyson's <a
href="http://swiki.cc.gatech.edu:8080/ugResearch/uploads/7/ImprovingTor.pdf">position
paper</a> on how to discard particularly slow choices without hurting
anonymity "too much". This line of reasoning needs more work and more
thinking, but it looks very promising.</li>
<li>Tor doesn't work very well when relays have asymmetric bandwidth
(e.g. cable or DSL). Because Tor has separate TCP connections between
each hop, if the incoming bytes are arriving just fine and the outgoing
bytes are all getting dropped on the floor, the TCP push-back mechanisms
don't really transmit this information back to the incoming streams.
Perhaps Tor should detect when it's dropping a lot of outgoing packets,
and rate-limit incoming streams to regulate this itself? I can imagine
a build-up and drop-off scheme where we pick a conservative rate-limit,
slowly increase it until we get lost packets, back off, repeat. We
need somebody who's good with networks to simulate this and help design
solutions; and/or we need to understand the extent of the performance
degradation, and use this as motivation to reconsider UDP transport.</li>
<li>A related topic is congestion control. Is our
current design sufficient once we have heavy use? Maybe
we should experiment with variable-sized windows rather
than fixed-size windows? That seemed to go well in an <a
href="http://www.psc.edu/networking/projects/hpn-ssh/theory.php">ssh
throughput experiment</a>. We'll need to measure and tweak, and maybe
overhaul if the results are good.</li>
<li>To let dissidents in remote countries use Tor without being blocked
at their country's firewall, we need a way to get tens of thousands of
relays, not just a few hundred. We can imagine a Tor client GUI that
has a "Tor for Freedom" button at the top that opens a port and relays a
few KB/s of traffic into the Tor network. (A few KB/s shouldn't be too
much hassle, and there are few abuse issues since they're not being exit
nodes.) But how do we distribute a list of these volunteer clients to the
good dissidents in an automated way that doesn't let the country-level
firewalls intercept and enumerate them? This probably needs to work on a
human-trust level. See our <a href="<page documentation>#DesignDoc">early
blocking-resistance design document</a> and our
<a
href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#BlockingResistance">FAQ
entry</a> on this, and then read the <a
href="http://freehaven.net/anonbib/topic.html#Communications_20Censorship">censorship
resistance section of anonbib</a>.</li>
<li>Tor circuits are built one hop at a time, so in theory we have the
ability to make some streams exit from the second hop, some from the
third, and so on. This seems nice because it breaks up the set of exiting
streams that a given relay can see. But if we want each stream to be safe,
the "shortest" path should be at least 3 hops long by our current logic, so
the rest will be even longer. We need to examine this performance / security
tradeoff.</li>
<li>It's not that hard to DoS Tor relays or directory authorities. Are client
puzzles the right answer? What other practical approaches are there? Bonus
if they're backward-compatible with the current Tor protocol.</li>
</ol>

<a href="<page contact>">Let us know</a> if you've made progress on any
of these!

</div>

#include <foot.wmi>

tor-webwml.git

Add research idea re studying the effectiveness of timing attacks against relay nodes that are also used as clients. Also, toss in some ideas on relay queue manipulation to implement adaptive padding and other cover mechanisms without extra traffic overhead.