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

<h2>Three things everyone can do now:</h2>
<ol>
<li>Please consider <a href="<page docs/tor-doc-server>">running
a server</a> to help the Tor network grow.</li>
<li>Tell your friends! Get them to run servers. 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 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>
<ul>
<li>We need to <a
href="http://wiki.noreply.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
<i>mapaddress</i> 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 <i>torify</i> 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>People running servers 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. Perhaps it would run out
of cron, or perhaps it would sleep until appropriate times and then do
its tweak (that's probably more portable). Can somebody write one for us
and we'll put it into <a href="<svnsandbox>contrib/">contrib/</a>?
This is a good entry for the <a href="<page gui/index>">Tor GUI
competition</a>.
  
</li>
<li>Tor can <a
href="http://wiki.noreply.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 server. 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>We hear that Tor users can fall victim to anonymity-breaking attacks
from javascript, java, activex, flash, etc, if they don't disable
them. Are there plugins out there (like NoScript for Firefox) that make
it easier for users to manage this risk? What is the risk exactly?</li>
<li>Is there a full suite of plugins that will replace all of Privoxy's
functionality for Firefox 1.5+? We hear Tor is much faster when you take
Privoxy out of the loop.</li>
<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="http://wiki.noreply.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="http://wiki.noreply.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 also need people to help
maintain the existing Italian, French, and Swedish translations -
see the <a href="<page translation-status>">translation status
overview</a>.</li>
<li>Can somebody walk us through whether we want to go the
<a href="http://www.cacert.org/">cacert</a> route for our
SSL <a href="<page documentation>#Developers">SVN repository?</a></li>
</ol>

<a id="Coding"></a>
<h2><a class="anchor" href="#Coding">Coding and Design</a></h2>
<p>Want to spend your Google Summer of Code working on Tor? Great. More
details coming soon. In the mean time, see if any of these ideas catch
your eye.</p>
<ol>
<li>Tor servers 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 server will empty the non-page pool, <a
href="http://wiki.noreply.org/noreply/TheOnionRouter/WindowsBufferProblems">causing
havoc and crashes</a>. We should probably be using overlapped IO
instead. One solution would be to teach libevent how to use overlapped IO
rather than select() on Windows, and then adapt Tor to the new libevent
interface.</li>
<li>Because Tor servers need to store-and-forward each cell they handle,
high-bandwidth Tor servers end up using dozens of megabytes of memory
just for buffers. We need better heuristics for when to shrink/expand
buffers. Maybe this should be modelled after the Linux kernel buffer
design, where we have many smaller buffers that link to each other,
rather than monolithic buffers?</li>
<li>We need an official central site to answer "Is this IP address a Tor
exit server?" questions. This should provide several interfaces, including
a web interface and a DNSBL-style interface. It can provide the most
up-to-date answers by keeping a local mirror of the Tor directory
information. The tricky point is that being an exit server is not a
boolean: so the question is actually "Is this IP address a Tor exit
server that can exit to my IP address:port?" The DNSBL interface
will probably receive hundreds of queries a minute, so some smart
algorithms are in order. Bonus points if it does active testing through
each exit node to find out what IP address it's really exiting from.</li>
<li>It would be great to have a LiveCD that includes the latest
versions of Tor, Polipo or Privoxy, Firefox, Gaim+OTR, etc. There are
two challenges here: first is documenting the system and choices well
enough that security people can form an opinion on whether it should be
secure, and the second is figuring out how to make it easily maintainable,
so it doesn't become quickly obsolete like AnonymOS. Bonus points if
the CD image fits on one of those small-form-factor CDs.</li>
<li>Related to the LiveCD image, we should work on an intuitively secure
and well-documented USB image for Tor and supporting applications. A
lot of the hard part here is deciding what configurations are secure,
documentating these decisions, and making something that is easy to
maintain going forward.</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, working
on a <a href="http://vidalia-project.net/">GUI</a> that's intuitive,
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>We need a measurement study of <a
href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a>
vs <a href="http://www.privoxy.org/">Privoxy</a>. Is Polipo in fact
significantly faster, once you factor in the slow-down from Tor? Are the
results the same on both Linux and Windows? Related, does Polipo handle
more web sites correctly than Privoxy, or vice versa? Are there stability
issues on any common platforms, e.g. Windows?</li>
<li>Related on the above, would you like to help port <a
href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a> so it
runs stably and efficiently on Windows?</li>
<li>We need a distributed testing framework. We have unit tests,
but it would be great to have a script that starts up a Tor network, uses
it for a while, and verifies that at least parts of it are working.</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="http://wiki.noreply.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>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>Tor doesn't work very well when servers 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 "help China" 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? Probably needs to work on a
human-trust level. See our <a
href="http://wiki.noreply.org/noreply/TheOnionRouter/TorFAQ#China">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 server 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 servers or dirservers. 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>

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