about/gsocProposal/gsoc10-proposal-dnselRewrite.html (9be75c2bc)

gsoc10-proposal-dnselRewrite.html

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<h2><a href="http://torproject.org/">Tor Project</a> - DNSEL Rewrite</h2>
Google Summer of Code Student Application 
Harry Bock &lt;hbock AT ele DOT uri DOT edu&gt;
<blockquote>
<h2>Abstract:</h2>

The TorDNSEL project is concerned with identifying individual hosts
 as valid and accessible Tor exit relays. Each Tor exit relay has an
 associated exit policy governing what traffic may leave the Tor
 circuit and go out as requests to the internet. A public database
 that can be easily queried or scraped would be of huge benefit to
 the Tor community and to services that are interested in whether
 clients originate from the Tor network, such as Wikipedia and IRC
 networks.

</blockquote>

<ol>
<li>
 
 What project would you like to work on? Use our ideas lists as a
 starting point or make up your own idea. Your proposal should
 include high-level descriptions of what you're going to do, with
 more details about the parts you expect to be tricky. Your
 proposal should also try to break down the project into tasks of a
 fairly fine granularity, and convince us you have a plan for
 finishing it.
 
 
 My primary interest is in the TorDNSEL rewrite. Currently
 unmaintained and written in Haskell, I would like to rework it
 from the ground up using Python and the Torflow interface.
 
 <ul>
 <li>
 Prior to actually building the new TorDNSEL, some time must be
 spent researching and testing strategies for identifying and verifying
 recent Tor exit relays.
 <ul>
 <li>
	Much of this information is available straight from the
	cached-descriptors file distributed to running Tor relays, but
	not all of it is accurate or up-to-date.
 </li>
 <li>
	
	 To ensure the honesty of advertised exit nodes, the program
	 must actively build circuits over the Tor network to the
	 intended exit node and verify the IP address and exit policies
	 listed in the cached router list. This will be accomplished via
	 TorFlow, most likely using the NetworkScanners tool SoaT. If
	 more detailed checking is required than provided by SoaT, it will
	 be modified and extended to suit the new requirements.
	
 </li>
 <li>
	
	 Since new relays entering the Tor network are almost
	 immediately available for use, it is important that new
	 relays are checked and added as quickly as possible.
	 Testing ExitPolicy honesty may be time-consuming for
	 certain relays, destinations, and services.
	
	
	 To improve exit honesty checking latency, hosts that have
	 complex exit policies may be checked incrementally; for
	 example, if popular services such as http/https/domain/ssh
	 are allowed by the relay's ExitPolicy, these should be
	 checked first and the relay can be marked as "honest
	 (preliminary)", so that partial results may be listed
	 earlier pending more thorough circuit testing.
	
 </li>
 </ul>
 </li><li>
 Once the desired method for compiling and verifying exit relays
 is tested, a formal design specification for the following operations
 must be compiled:
 <ol>
 <li>Scraping of all known exit relays and their exit
	policies. As noted in the Tor dir-spec v3, in the future
	it will not scale to have every Tor client/directory cache know
	the IP of every other router. We need to be able to accurately
	obtain this data, up-to-date and in bulk, from an authoritative
	source. The DNSEL should be able to verify all exit relays,
	in the shortest time span allowable.
 </li>
 <li>
	Active testing for valid exit IP addresses and policies.
 </li>
 <li>
	Parameters and raw format of the resulting data.
 </li>
 <li>
	Formal mechanisms and formats for access by consumers of this
	data. As a minimal starting point, SQLite and JSON should be
	supported for build data sets, as both are well-structured,
	standardised formats that have cross-platform open-source
	support for the most widely used programming languages. One this
	data is readily available, it would be extremely useful to provide
	a simple API in Python to improve ease-of-use and integration of
	this data with existing services.
 </li>
 </ol>
 </li>
 <li>
 
 Currently, users can check the TorBulkExitList on
 check.torproject.org or perform DNS queries against
 exitlist.torproject.org, but this is not ideal for all consumers
 of this data; currently it is expensive to perform these queries
 and they must be done one at a time over the network. While this
 is less of an issue for services that need to perform infrequent
 exit checks, I propose that this mechanism can actually harm
 anonymity, as an adversary that can track these queries (those
 with access to the network of the querying service, or those
 running rogue DNSEL implementations, should it become more
 distributed) can determine, for example, what exit nodes are
 currently serving a large amount of IRC connections. This is
 more important for services that do frequent queries on a wide
 range of IP addresses. By encouraging these queries to be done
 locally, we can improve network latency, throughput, and
 anonymity together.
 
 
 On the other hand, for some services, requiring services to
 download the entire exit set when they only need to query a few
 addresses daily would be a waste of valuable resources on both
 ends. Thus, both single-exit queries and bulk exit description
 lists must be provided; raw queries would be used by services
 that are simply doing manual checks of possible Tor addresses,
 or infrequent automated checks.
 
 
 The primary consumers of bulk data are services that need
 to do frequent automated checks and benefit strongly from
 local caching of data. Some prominent examples would be:
 <ul>
	<li>The Tor project itself (see TorBulkExitList.py,
	 check.torproject.org, etc.).</li>
	<li>IRC networks such as Freenode and OFTC that
	 automatically scrub any potentially identifiable
	 information from WHOIS queries.</li>
	<li>Social networks or collaborative communities such as
	 Wikipedia that would benefit from knowing if a
	 particular IP address is shared, allowing them to
	 (possibly) be more lenient towards abuse from
	 anonymizing services.
	</li>
 </ul>
 
 
 A particularly important goal is to ensure that Tor users
 that also happen to run Tor relays are not automatically
 blocked by services simply because they are relays or exit
 nodes. If a service is able to ascertain that an IP address
 corresponds to a Tor relay, but its exit policy would not
 allow traffic to access the service from Tor, ideally it
 should not block access to its resources. The cheaper and
 easier it is for a service operator to validate this kind of
 information, the more likely the service is to use it and
 collaborate with the Tor community. The more the service is
 used, the more likely we are to get feedback, whether
 it be able the data format, false positives or negatives,
 invalid/incorrect exit policies, etc.
 
 </li>
 <li>
 The TorDNSEL project itself will likely benefit from being broken
 into several components that interact with each other and operate on
 exit list data sets.
 <ul>
 <li>Data scraper and honesty checking daemon: constantly runs in
 the background, fetching new information about Tor relays and
 their exit policies and updating the raw journal. As new relays
 come in, they are accessed and verified for honesty and
 correctness. As relay data becomes stale according to a
 configurable TTL, they are re-checked.
 </li>
 <li>
	Data compiler: Manages, updates, and merges exit lists. Can
	import and export data from bulk formats and provide
	statistics about data sets.
 </li>
 <li>
	Single-query engine: Allows applications and external services
	to query about a single IP address and exit policy at a time.
	Can interface via several convenient methods, starting out
	simple (e.g., Python API requests or HTTP requests) and
	eventually working up to RBL-style DNS queries, like the
	original DNSEL, should time permit.
 </li>
 <li>
	Data distribution: How do clients actually access bulk data?
	This doesn't necessarily have to be its own application, but
	it must be feasible for clients to easily scrape and update
	their local caches. The data may be served by a static web
	server, like lighttpd, or via other mechanisms (sftp, or dns
	zone transfer as a more convoluted example).
 </li>
 </ul>
 </li>
 <li>
 As an aside, there are several open and accepted Tor proposals
 that are relevant to the work I will complete:
 <ul>
 <li>140 Provide diffs between consensuses (ACCEPTED)</li>
 <li>146 Add new flag to reflect long-term stability (OPEN)</li>
 <li>147 Eliminate the need for v2 directories in generating v3 directories (ACCEPTED)</li>
 <li>159 Exit Scanning (OPEN)</li>
 </ul>
 </li>

</ul>

Estimated timeline:
For each weekly milestone, appropriate documentation should be written to
coincide with the completed work. For example, end-user tools should have
manual pages at the very least, and preferably include a LaTeX manual. Milestones
that are primarily experimental in nature should include complete descriptions and
proposals in plain-text where appropriate. All source code will be thoroughly
commented and include documentation useful to developers.
 

 April 26 - May 24 (Pre-SoC): Get up to speed with Tor
 directory and caching architecture, pick apart existing Haskell
 implementation of TorDNSEL, and master TorFlow.


 May 31 (end of week 1): Have a working mechanism for
 compiling as much testable information about exit relays as
 possible. This data must be easily accessible for subsequent work.
 This may be taken, adapted, or abstracted from existing data directory crawling
 in TorFlow.


 June 14 (week 3): Working implementation of tests using TorFlow, especially
 ExitAuthority tools. This will probably be the most time-consuming period; may take
 up to a week more than anticipated.


 June 21 (week 4): Be able to produce consistent, constantly updating exit lists
 with tested and untested exit policies listed. Find Tor developer guinea pigs to
 test and hunt for glaring holes in exit relay honesty testing and verification. :)


 June 28 (week 5): Begin proof-of-concept production of bulk
 data formats (raw, SQLite and JSON), all of which should be similar
 in format. Consultations should be made with consumers of such data
 (Freenode, Wikipedia, etc.) to ensure the current data presentation
 is not overreaching or missing information that would be useful to
 them. 


 July 12 (week 7): Integrate existing functionality and data access methods into
 a Python API that is usable for consumers and the DNSEL application itself. Style should
 be similar to TorFlow where possible.

 July 16 (midterm evals): Completed specifications of TorDNSEL
 operation, basic data formats, and delivery methods. Completed
 first proof-of-concept implementation. First major review with
 mentors and as much of the Tor developer community as time permits.


 July 19 (week 8): Work on designing and testing exit list cache update mechanisms.
 Start with something similar to cached-descriptors.new journaling, and work up
 to something for useful for other data formats. Integrate mechanism into API.


 July 26 (week 9): Solidify main scrape/check application and
 perform as much real-world testing as time permits, adjusting for
 major setbacks, if any.


 August 2 (week 10): Make adjustments based on feedback from
 (hopefully) several real-world consumers of TorDNSEL data.
 Generally polish and improve usability of core application(s).


 August 9 ("pencils down"):: Start pumping out documentation and comprehensive
 code and review.


 August 16 ("okay really, pencils down"):Major remaining kinks
 should be ironed out; polish specification and documentation and
 begin writing final evaluations. Plan for future maintenance of
 TorDNSEL.

</li>

<li>
 Point us to a code sample: something good and clean to
 demonstrate that you know what you're doing, ideally from an
 existing project.
 
 
 Code from almost any project I've worked on is available at
 http://git.spanning-tree.org/. Some of my better code:
 <ul>
 <li><a href="http://git.spanning-tree.org/index.cgi/grizzlor/">libgrizzlor</a> [C, Common Lisp], an abstraction layer for the
	SILC client library focused on bots.
 </li>
 <li><a href="http://git.spanning-tree.org/index.cgi/rigel/tree/">rigel</a> [C], a UNIX PIC16/PIC18 program loader for use with the FIRST robotics competition.</li>
 <li><a href="http://git.spanning-tree.org/index.cgi/nis/">Network Subsystem Inventory</a> [Python], a Django web application for keeping an inventory of network resources on a large university network. </li>
 <li><a href="http://git.spanning-tree.org/index.cgi/Periscope/">Periscope</a>
 [Common Lisp], a network monitoring application inspired by IP-Audit, 
designed from the ground up to work with the Argus netflow application.</li>
 </ul>
 
</li>
<li> Why do you want to work with The Tor Project / EFF in particular?

The Tor Project interests me primarily from architectural and
information security perspectives; my primary focus in information
security has always been authentication and authorization - verifying
the identity of a user to explicitly or implicitly control access to
machine and network resources. The goal of all forms of public-key
and secure hash cryptography is the authentication of a third party or
data, essentially pinning their identity down.


Tor greatly interests me because it has the opposite goal; it tries to
ensure that pinning down the identity of any particular user is
(ideally) impossible or at least greatly hindered for any non-global
adversary. Protecting the rights of network users by preserving their
anonymity is an incredibly important and complicated goal, and Tor's
role in increasing anonymity of internet access in the face of many
types of adversaries is extremely valuable. To this end, I hope that
my contributions will be found useful by the Tor project, its users,
and those working to protect these end users.

</li>
<li>
 
 Tell us about your experiences in free software development
 environments. We especially want to hear examples of how you have
 collaborated with others rather than just working on a project by
 yourself.
 
 While nearly all of the projects I've worked on have been free
 software, my experience working directly with the free software
 community at large is minimal. I have contributed briefly to the
 KDE project, working on their display configuration application,
 and submitted patches to other open source projects (QoSient's
 Argus netflow tools and Google's ipaddr-py, for example). I have
 collaborated with various universities in New England on
 development of the Nautilus project (http://nautilus.oshean.org/)
 and its main subproject, Periscope
 (http://nautilus.oshean.org/wiki/Periscope), while working at the
 OSHEAN non-profit consortium. 
 
I sincerely look forward to working with the vibrant development
community of the Tor project and hope to gain more experience in
collaborating with an experienced group of developers.

</li>

<li>
 
 Will you be working full-time on the project for the summer, or
 will you have other commitments too (a second job, classes, etc)?
 If you won't be available full-time, please explain, and list
 timing if you know them for other major deadlines
 (e.g. exams). Having other activities isn't a deal-breaker, but we
 don't want to be surprised.
 
 
 I will be working part-time at the University of Rhode Island
 Information Security Office, and will have one summer class for five
 weeks starting in late May. I don't anticipate either will
 significantly affect my involvement with the Tor project.
 
</li>
<li>
 
 Will your project need more work and/or maintenance after the
 summer ends? What are the chances you will stick around and help
 out with that and other related projects?
 

While I am confident I can produce a working initial implementation of
dnsel in the time allotted, I anticipate it will need more work at the
end of summer. One of my primary goals for the dnsel project is to
make it easier to maintain, as its operation will have to be adjusted
to fit with changes in the Tor architecture. Making the project more
accessible to other maintainers will allow for greater collaboration
and improvements to dnsel where development on the current
implementation has stagnated.

</li>
<li>
 
 What is your ideal approach to keeping everybody informed of your
 progress, problems, and questions over the course of the project? Said
 another way, how much of a "manager" will you need your mentor to be?
 
 
 I will do my best to communicate with my mentors and the Tor developer
 community at large as frequently and directly as possible, via
 #tor-dev and the mailing lists. I also hope to inform others of more
 major milestones in the project via a blog or web page, and keep
 detailed documentation and progress updates on the Tor wiki.
 
</li><li>
 What school are you attending? What year are you, and what's 
your major/degree/focus? If you're part of a research group, which one?
 
 I am currently attending the University of Rhode Island. This is my
 fourth year in college and second at URI; I am a Computer Engineering 
major, intending to graduate next year and obtain my masters degree the 
following year. My primary interests are low-level software development
 and systems programming, networking, information security, and signal 
processing.
 
</li>
<li>
 How can we contact you to ask you further questions? Google 
doesn't share your contact details with us automatically, so you should 
include that in your application. In addition, what's your IRC nickname?
 Interacting with us on IRC will help us get to know you, and help you 
get to know our community.
 
 You can contact me at hbock@ele.uri.edu; my nickname on IRC is hbock.
 
</li>
</ol>
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