tor

Tor-0.2.0.26-rc replaces several V3 directory authority keys affected by a recent Debian OpenSSL bug.

This is a security-critical release.

Everybody running any version in the 0.2.0.x series should upgrade, whether
they are running Debian or not. Also, all servers running any version of Tor
whose keys were generated by Debian, Ubuntu, or any derived distribution may
have to replace their identity keys. See our security advisory for full details. As always, you can find Tor 0.2.0.26-rc on the downloads page.

Changes in version 0.2.0.26-rc - 2008-05-13
Major security fixes:

• Use new V3 directory authority keys on the tor26, gabelmoo, and moria1 V3 directory authorities. The old keys were generated with a vulnerable version of Debian's OpenSSL package, and must be considered compromised. Other authorities' keys were not generatedwith an affected version of OpenSSL.

Major bugfixes:

• List authority signatures as "unrecognized" based on DirServer lines, not on cert cache. Bugfix on 0.2.0.x.

Minor features:

• Add a new V3AuthUseLegacyKey option to make it easier for authorities to change their identity keys if they have to.

Tor 0.2.0.20-rc (released Feb 24) is the first release candidate for the 0.2.0 series. It makes more progress towards normalizing Tor's TLS handshake, makes hidden services work better again, helps relays bootstrap if they don't know their IP address, adds optional support for linking in openbsd's allocator or tcmalloc, allows really fast relays to scale past 15000 sockets, and fixes a bunch of minor bugs reported by Veracode.
http://archives.seul.org/or/talk/Feb-2008/msg00279.html

Tor 0.2.0.19-alpha (released Feb 9) makes more progress towards normalizing Tor's TLS handshake, makes path selection for relays more secure and IP address guessing more robust, and generally fixes a lot of bugs in preparation for calling the 0.2.0 branch stable.
http://archives.seul.org/or/talk/Feb-2008/msg00134.html

Torbutton 1.1.13 (released Feb 1), 1.1.14 (released Feb 24), and 1.1.15 (released Feb 26) fix many more potential privacy and identity leaks, mostly based on exploits found by Greg Fleischer. They also add support for automatic updates via the usual Firefox extension upgrade approach.
https://torbutton.torproject.org/dev/CHANGELOG

Work continued toward the upcoming Vidalia 0.1.0 release (which came out March 1): support for launching Firefox and Polipo as supporting applications; support for learning from Tor when the first circuit is ready so it can inform the user; and many other bugfixes including a few security fixes.
http://trac.vidalia-project.net/browser/vidalia/releases/vidalia-0.1.0/C...

The Tor 0.2.0.19-alpha release contained many security-related cleanups based on an anonymously submitted code review from a static analysis tool. The Tor 0.2.0.20-rc release contained even more security-related cleanups, based on an external security analysis and audit by Veracode. Hopefully cleanups at this stage will reduce the number of times we need to push out an urgent new stable "0.2.0" release for security reasons. read more »

Tor 0.2.0.18-alpha (released Jan 25) adds a sixth v3 directory authority run by CCC, fixes a big memory leak in 0.2.0.17-alpha, and adds new config options that can warn or reject connections to ports generally associated with vulnerable-plaintext protocols.
http://archives.seul.org/or/talk/Jan-2008/msg00442.html

Tor 0.2.0.16-alpha and 0.2.0.17-alpha (released Jan 17) add a fifth v3 directory authority run by Karsten Loesing, and generally clean up a lot of features and minor bugs.
http://archives.seul.org/or/talk/Jan-2008/msg00254.html

Tor 0.1.2.19 (released Jan 17) fixes a huge memory leak on exit relays, makes the default exit policy a little bit more conservative so it's safer to run an exit relay on a home system, and fixes a variety of smaller issues.
http://archives.seul.org/or/announce/Jan-2008/msg00000.html

We continued work on the "BridgeDB" module: major progress on January was to improve robustness of the email subsystem so it is better at detecting forged mails that claim to be from gmail but are actually from elsewhere.

Work continued toward the upcoming Torbutton 1.1.13 release (which came out Feb 1). This new release has several significant security-related fixes:
https://torbutton.torproject.org/dev/CHANGELOG

Work continued toward the upcoming Vidalia 0.1.0 release: support for launching Firefox and Polipo as supporting applications; support for learning from Tor when the first circuit is ready so it can inform the user; and many other bugfixes including a few security fixes:
http://trac.vidalia-project.net/browser/vidalia/trunk/CHANGELOG

We added a "How do I find a bridge?" link and corresponding help text to Vidalia's 'Network' settings page.

From the Tor 0.2.0.16-alpha ChangeLog:
“Do not try to download missing certificates until we have tried to check our fallback consensus.” This change gets us closer to being able to bootstrap without ever needing to contact the central directory authorities. read more »

Over the past few days there has been some coverage of my PhD thesis, and its relationship to Tor, on blogs and online news sites. It seems like this wave started with a column by Russ Cooper, which triggered articles in PC World and Dark Reading. The media attention came as a bit of a surprise to me, since nobody asked to interview me over this. I'd encourage other journalists writing about Tor to contact someone from the project as we're happy to help give some context.

My thesis is a fairly diverse collection of work, but the articles emphasize the impact of the attacks I discuss on users of anonymity networks like Tor. Actually, my thesis doesn't aim to show that Tor is insecure; the reason I selected Tor as a test case was that it's one of the few (and by far the largest) low-latency system that aims to stand up to observation. Other, simpler, systems have comparatively well understood weaknesses, and so there is less value in researching them.

Quantifying the security of anonymity systems is a difficult question and still being actively worked on. Comparing different systems is even harder since they make different assumptions on the capabilities of attackers (the “threat model”). The mere chance of attacks doesn't indicate that a system is insecure, since they might make assumptions about the environment that are not met, or are insufficiently reliable for the scenario being considered.

The actual goal of my thesis was try to better understand the strengths and weaknesses of systems like Tor, but more importantly to also to suggest a more general methodology for discovering, and resolving flaws. I proposed that the work from the well-established field of covert channels could be usefully applied, and used examples, including Tor, to justify this.

There remains much work to be done before it's possible to be sure how secure anonymity systems are, but hopefully this framework will be a useful one in moving forward. Since in September 2007 I joined the Tor project, I hope I'll also help in other ways too.

Welcome to the official Tor Project blog. We post a few times a month to discuss topics such as Tor development, recent press, and other related memes.