- tor-dev - lists.torproject.org

torrouter development
by ficus＠robocracy.org 12 Sep '12

12 Sep '12

Hello tor-dev! I would like to contribute to the torouter (aka TorRouter, aka OnionBox?) project, with the intention of getting a "functional" development image for the DreamPlug hardware released in the next few weeks. The goals of the torouter project seem a bit vague (especially w/r/t a transparent torified WiFi access point), perhaps this is why development slowed down previously. I will attempt a design document and specification, but mostly focus on making the core components (debian, tor, web interface) functional and configurable, such that they could be leveraged by others as solutions to specific use cases. Will this be useful to others? It seems like the preferred collaboration tool is the trac wiki and tickets. Many of the torouter tickets seem stale and incomplete, and the roadmap on the trac wiki is very out of date. Unless there is advice i'll ignore those but continue discussion on tickets like #3854 (Summary of outstanding things with Torouter) and #3453 (Torouter desires and features). cheers!

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Format-Transforming Encryption for Censorship Circumvention
by Kevin P Dyer 11 Sep '12

11 Sep '12

Following my email to this list, dated 29/07/2012, I direct your attention to the IACR eprint document http://eprint.iacr.org/2012/494, "Format-Transforming Encryption: More than Meets the DPI". In it, we present our framework for steganographic encoding of messages using regular languages, along with initial findings for a Python/C++ based implementation. To briefly highlight some of the main things we deliver: * A record-layer, powered by format-transforming encryption, that can tunnel arbitrary SOCKS streams. * Algorithms that allow efficient and invertible mapping between bit strings and elements of a regular language L. These allow us to encode traditional encryptions of plaintexts into strings from L in a way that maximizes the number of bits that are encoded. * A framework for the creation of good regular languages, "good" with respect to performance and security. In particular, our language-learning framework produces sets of regular expressions (compact representations of the languages) that are learned from real traffic. Our system also allows you to use off-the-shelf regular expressions, like those from appid [1] and l7-filter [2] that are designed to detect HTTP traffic. We consider this preliminary technical report on a work-in-progress. In fact, we can already do more than what is reported (e.g. greater variety of languages, better system performance), but we will save these advances for a future release. Cheers, Kevin P Dyer (and his co-authors) [1] http://code.google.com/p/appid/ [2] http://l7-filter.sourceforge.net/

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Integration of Tor, Tor Browser, Tor IM, Tor Birdy, Vidalia, Tor Router, Tails, etc.
by adrelanos 10 Sep '12

10 Sep '12

Hello, the current integration has a lot open issues and feature requests. [2] Because there might come a proposal [1] to solve this cleanly, I created an overview of all related open issues. [2] There are just so many issues I though it makes sense to create an overview so nothing gets forgotten. Feel free to edit/correct/expand the wiki site. Add your wishes. I cc'ed all effected people, if someone has been forgotten, feel free to forward this mail. Can we have this discussion on tor-dev? Cheers, adrelanos [1] https://trac.torproject.org/projects/tor/ticket/5611#comment:43 [2] https://trac.torproject.org/projects/tor/wiki/doc/TB

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[GSoC] [Stegotorus] Code submission and more curl
by vmon 10 Sep '12

10 Sep '12

Hello Zack, 1) I would like to ask your permission to submit the whole code for code submission. First because my task in the summer wasn't only to write the parts that I wrote but also to read the code and debug it as well. Secondly because the git log shows who wrote what. Thirdly, It's easier. 2) I had more discussion on libcurl-dev with the libcurl main developer. He thinks despite the fact my approach is working right now, it isn't stable and can break down in a different environment. To solve this, I'm going to let curl also read from the socket instead of libevent, this isn't very hard (I'll disable both EV_READ and EV_WRITE as soon as I'm handing the socket to curl). I confirmed with Nick that (unlike libcurl) libevent support this. 3) Thank you for telling me about fts. I'm going to replace boost code with fts soon. 4) >I still don't see the problem. If you do exactly that, and don't use >he DECLARE macros for http_apache_steg, what breaks? If I don't use the DECLARE then I can't specify http_apache as the steg protocol in the command line . Best, vmon

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Tenative schedule for Tor 0.2.4 [Or, why I might reject your patches in November->March]
by Nick Mathewson 07 Sep '12

07 Sep '12

Hi, all! Last year, I announced a tenative schedule for 0.2.3.x. We didn't stick to it, and things have gone a little pear-shaped with getting 0.2.3.x stabilized, but I think with a few tweaks we can use something similar to get a good schedule out for 0.2.4.x. My goals remain about what they were before: get release out faster by getting better at saying "no" to features after a release window. My target is March or April 2013. To that end: October 10, 2012: Big feature proposal checkpoint. Any large complicated feature which requires a design proposal must have its first design proposal draft by this date. November 10, 2012: Big feature checkpoint. If I don't know about a large feature by this date, it might have to wait. November 10, 2012: Big feature proposal freeze. Any small feature which requires a design proposal must have its design proposal finished by this date. December 10, 2012: Big feature merge freeze. No big features will be merged after this date. December 10, 2012: Small feature proposal freeze. Any small feature which requires a design proposal must have its design proposal finished by this date. January 10, 2013: Feature merge freeze. No features after this date. I mean it. Feb 20, 2013: Buggy feature backout date. Any feature which seems intractably buggy by this date may be disabled, deprecated, or removed until the next release. On the meaning of "feature": I'm probably going to argue that some things that you think are bugfixes are features. I'm probably going to argue that your security bugfix is actually a security feature. I'm probably even going to argue that most non-regression bugfixes are features. Let's try to get a release out *early* in 2013 this time, come heck or high water. (This is all subject to change, but let's not push it.) [0] https://lists.torproject.org/pipermail/tor-dev/2011-July/002851.html happy hacking, -- Nick

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Parallel release series for directory authorities?
by Nick Mathewson 06 Sep '12

06 Sep '12

Hi, all! Here's an idea I had for directory authorities and the 0.2.3 release series. "As you know Bob," Tor 0.2.3 will be stable very soon, and I'm hoping not to take any more patches for it except for important security issues. I want 0.2.4 to come out very early next year. But in the meantime, to support 0.2.4, and to deploy security/reliability features to the network early, there are some directory consensus features that we'd want to deploy before the rest of 0.2.4 is done and stable. In particular, I'd like directories to be able to reach consensus on IPv6 addresses (6363), and I'd like to try out the code that Mike wrote to make the bandwidth voting system more robust against dishonest during its startup phase (2286). So here's my plan: Make a "maint-0.2.3-da" branch based on 0.2.3, plus feature patches for directory authorities. It gets patches from the stable series (0.2.3), plus directory-authority features under development. It would get merged-forward into 0.2.4, to make sure that 0.2.3-da and 0.2.4 behavior stay in sync. This way we can get new authority features working in time to support 0.2.4 clients, but without forcing too many authorities to run 0.2.4 before it's ready, and without forcing us to make feature changes in 0.2.3 proper. Thoughts? yrs, -- Nick

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(FWD) Re: known attacks on Tor
by Roger Dingledine 05 Sep '12

05 Sep '12

Hi folks, Here's an email I wrote to a researcher who is working on categorizing anonymity attacks. I figured I should share it with you in case it's useful in some way. It's also related to my talk at https://www.cosic.esat.kuleuven.be/ecrypt/provpriv2012/program.html and I expect to use it as background for my discussions at the upcoming Dagstuhl: http://www.dagstuhl.de/no_cache/en/program/calendar/semhp/?semnr=12381 --Roger ----- Forwarded message from Roger Dingledine <arma(a)mit.edu> ----- > If you have any suggestions about which paper on each attack is most > likely to provide such an explanation, please send them to me as soon > as possible. > > > - "Traffic confirmation attack". If he can see/measure the traffic flow > > between the user and the Tor network, and also the traffic flow between > > the Tor network and the destination, he can realize that the two flows > > correspond to the same circuit: > > http://freehaven.net/anonbib/#SS03 > > http://freehaven.net/anonbib/#timing-fc2004 > > http://freehaven.net/anonbib/#danezis:pet2004 > > http://freehaven.net/anonbib/#ShWa-Timing06 > > http://freehaven.net/anonbib/#murdoch-pet2007 > > http://freehaven.net/anonbib/#ccs2008:wang > > http://freehaven.net/anonbib/#active-pet2010 It depends in what way you want to become more precise. I think the #SS03 paper might have the simplest version of the attack ("count up the number of packets you see on each end"). The #timing-fc2004 paper introduces the notion of a sliding window of counts on each side. The #murdoch-pet2007 one looks at how much statistical similarity you can notice between the flows when you are only sampling a small fraction of packets on each side. > > - "Congestion attack". An adversary can send traffic through nodes or > > links in the network, then try to detect whether the user's traffic > > flow slows down: > > http://freehaven.net/anonbib/#torta05 > > http://freehaven.net/anonbib/#torspinISC08 > > http://freehaven.net/anonbib/#congestion-longpaths Section 2 and the first part of Section 3 in #congestion-longpaths is probably your best bet here. It actually provides a good pretty overview of related work including the passive correlation attacks above. If by 'more precise' you mean you want to know exactly what the threat model is for this attack, I'm afraid it varies by paper. In #torta05 they assume the adversary runs the website, and when the target user starts to fetch a large file, they congest (DoS) relays one at a time until they see the download slow down. In #congestion-longpaths they assume the adversary runs the exit relay as well, so they know the middle relay, and the only question is which relay is the guard (first) relay. In #torspinISC08 on the other hand, they preemptively try to DoS the whole network except the malicious relays, so the target user will end up using malicious relays for her circuit. > > - "Latency or throughput fingerprinting". While congestion attacks > > by themselves typically just learn what relays the user picked (but > > don't break anonymity as defined above), they can be combined with > > other attacks: > > http://freehaven.net/anonbib/#tissec-latency-leak > > http://freehaven.net/anonbib/#ccs2011-stealthy > > http://freehaven.net/anonbib/#tcp-tor-pets12 These are three separate attacks. In #tissec-latency-leak, they assume the above congestion attacks work great to identify Alice's path, and then the attacker builds a parallel circuit using the same path, finds out the latency from them to the (adversary-controlled) website that Alice went to, and then subtracts out to find the latency between Alice and the first hop. #ccs2011-stealthy actually proposes a variety of variations on these attacks. They show that if Alice uses two streams on the same circuit, the two websites she visits can use throughput fingerprinting to realize they're the same circuit. They also show that by looking at the throughput Alice gets from her circuit, you can rule out a lot of relays that wouldn't have been able to provide that throughput at that time. And finally, they show that if you build test circuits through the network and then compare the throughput your test circuit gets with the throughput Alice gets, you can guess whether your circuit shares a bottleneck relay with Alice's circuit. Where "show" should probably be in quotes, since it probably works sometimes and not other times, and nobody has explored how robust the attack is. #tcp-tor-pets12 has the adversary watching Alice's local network, and wanting to know whether she visited a certain website. The adversary exploits vulnerabilities in TCP's window design to spoof RST packets between every exit relay and the website in question. If they do it right, the connection between the exit relay and the website cuts its TCP congestion window in response, leading to a drop in throughput on the flow between the Tor network and Alice. In theory. It also works in the lab, sometimes. I also left out http://freehaven.net/anonbib/date.html#esorics10-bandwidth which uses a novel remote bandwidth estimation algorithm to try to estimate whether various physical Internet links have less bandwidth when Alice is fetching her file. In theory this lets them walk back towards Alice, one traceroute-style hop at a time. In practice they need an Internet routing map (these are notoriously messy for the same reasons the Decoy Routing people are realizing), and also Alice's flows have to be quite high throughput for a long time. > > - "Website fingerprinting". If the adversary can watch the user's > > connection into the Tor network, and also has a database of traces of > > what the user looks like while visiting each of a variety of pages, > > and the user's destination page is in the database, then in some cases > > the attacker can guess the page she's going to: > > http://freehaven.net/anonbib/#hintz02 > > http://freehaven.net/anonbib/#TrafHTTP > > http://freehaven.net/anonbib/#pet05-bissias > > http://freehaven.net/anonbib/#Liberatore:2006 > > http://freehaven.net/anonbib/#ccsw09-fingerprinting > > http://freehaven.net/anonbib/#wpes11-panchenko > > http://freehaven.net/anonbib/#oakland2012-peekaboo #oakland2012-peekaboo aims to be a survey paper for the topic, so it's probably the right one to look at first. > > - "Correlating bridge availability with client activity." > > http://freehaven.net/anonbib/#wpes09-bridge-attack If you run a relay and also use it as a client, the fact that the adversary can route traffic through you lets him learn about your client activity. Section 1.1 summarizes: 2. A bridge always accepts connections when its operator is using Tor. Because of this, an attacker can compile a list of times when a given operator was either possibly or certainly not using Tor, by repeatedly attempting to connect to the bridge. This list can be used to eliminate bridge operators as candidates for the originator of a series of connections exiting Tor. We demonstrate empirically that typically, a small set of linkable connections is sufficient to eliminate all but a few bridges as likely originators. 3. Traffic to and from clients connected to a bridge interferes with traffic to and from a bridge operator. We demonstrate empirically that this makes it possible to test via a circuit-clogging attack [17, 15] which of a small number of bridge operators is connecting to a malicious server over Tor. Combined with the previous two observations, this means that any bridge operator that connects several times, via Tor, to a web-site that can link users across visits could be identified by the site's operator. > > I tried to keep this list of "excepts" as small as possible so it's not > > overwhelming, but I think the odds are very high that if the ratpac comes > > up with other issues, I'll be able to point to papers on anonbib that > > discuss these issues too. For example, these two papers are interesting: > > http://freehaven.net/anonbib/#ccs07-doa Traditionally, we calculate the risk that Alice's circuit is controlled by the adversary as the chance that she chooses a bad first hop and a bad last hop. They're assumed to be independent. But if an adversary's relay is chosen anywhere in the circuit yet he *doesn't* have both the first and last hop, he should tear down the circuit, forcing Alice to make a new one and roll the dice again. Longer path lengths (once thought to make the circuit safer) *increase* vulnerability to this attack. I think the guard node design helps here, but whether that's true is an area of active research. > > http://freehaven.net/anonbib/#bauer:wpes2007 If you lie about your bandwidth, you can get more traffic than you "should" get based on bandwidth investment. In theory we've solved this by doing active bandwidth measurement: https://blog.torproject.org/blog/torflow-node-capacity-integrity-and-reliab… but in practice it's not fully solved: https://trac.torproject.org/projects/tor/ticket/2286 --Roger ----- End forwarded message -----

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Tor bufferbloat
by David Goulet 05 Sep '12

05 Sep '12

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi everyone, I discovered, during a presentation at this year LinuxCon in San Diego, the problem of "bufferbloat" which is encountered in network bottlenecks. https://en.wikipedia.org/wiki/Bufferbloat http://www.bufferbloat.net/ There is been a good amount of work done so far to fix this problem ending up with the CoDel algorithm (http://queue.acm.org/detail.cfm?id=2209336) The Linux kernel is about to accept this policy as default. Anyhow, I looked around for some recent studies on the Tor network about such congestion issues but I can't find any information on if this phenomenon is observed on the Tor network. Someone knows about that? Thanks a lot! David -----BEGIN PGP SIGNATURE----- iQEcBAEBCgAGBQJQR59ZAAoJEELoaioR9I02nkkH/0NYYnaca6N5pbDDbu96klff BGVmxcO8TEbbdI41HBWaJJHyUSi1CDbfZXcK6eaqRgDhj/yGcTN4YKgU/fP7LQFw /rp+MnWxPt7uqfrso+jSgvpDX6FS8r9cXwG6aMd9V39CuLRoVHYnNAMQrwHMyXud bMk0cHe71FGcyW+BGxZwrbjtvP3gcIZH9r/LNGaJepRzn+vB0NcwVpUG08D50Nxe M/3Lhokrc/IqaFi0+FX5fUoc8TALsjgjPZ672DdsY1CMwxbPMxpBKadJ9TWA906U QNxZb/lOa/fSWrnjY3nDaFJNppmyqYgoC1iJNJiCiJC8Jbxgj0/gyQjhY1d11Qc= =yFyg -----END PGP SIGNATURE-----

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Damian's Status Report - August 2012
by Damian Johnson 04 Sep '12

04 Sep '12

Hi all. I spent most of August, like the prior month, traveling. This time I attended Toorcamp [1] and went on vacation. Both were pleasant and relaxing, but not terribly conducive to coding so I don't have much to report... * Descriptor CSV Export Functionality Naif proposed export functionality for Tor server descriptors a while back [1], which Eric and Megan took the first stab at [2]. I ended up revising this quite a bit [4], but it turned out nicely. * Caching Expansion and Test Prompt Added caching for GETCONF and static GETINFO queries. I also added a handy little script for a debugging interpretor. It kicks off Tor, then provides an interactive python prompt with a controller instance to it (optionally shutting Tor down afterward). Ravi code reviewed these changes [5] and volunteered to do code reviews of my future work as well. * Consensus Parsing Over the last few weeks Ravi's been working on a patch to parse network status documents [6]. It's functional, but missing unit tests and deviates from the parsing style and strict validation done for the other descriptor types so I'm taking a turn with the code. Thus far I'm done revising and adding tests for router status entries, and now working on the document. Changes are available in the 'document-parsing' branch of my repo [7]. Parsing these documents is a far larger task than I thought (especially if you include v2 documents and microdescriptors), so working on this branch will probably keep me occupied for much of September. * Controller Expansion Ravi has gone on a hacking binge, adding support for USEFEATURE [8], SIGNAL [9], EXTENDCIRCUIT [10], and SETCIRCUITPURPOSE [11]. Cheers! -Damian [1] http://www.toorcamp.org/ [2] https://trac.torproject.org/6171 [3] https://trac.torproject.org/6512 [4] https://gitweb.torproject.org/stem.git/commitdiff/7022021c4207a0066cb932616… [5] https://trac.torproject.org/6631 [6] https://trac.torproject.org/6569 [7] https://gitweb.torproject.org/user/atagar/stem.git/shortlog/refs/heads/docu… [8] https://trac.torproject.org/6417 [9] https://trac.torproject.org/6659 [10] https://trac.torproject.org/6666 [11] https://trac.torproject.org/6670

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Tor on IPv6 roadmap and status page
by Linus Nordberg 02 Sep '12

02 Sep '12

Hi, The roadmaps/Tor/IPv6 [1] wiki page has been started with the goal of communicating the status of the work with Tor on IPv6. Additionally, searching for Trac tickets with the keyword "ipv6" [2] might give a picture of what's going on. Asking here or highlighting ln5 on #tor-dev is of course another perfectly fine option. [1] https://trac.torproject.org/projects/tor/wiki/org/roadmaps/Tor/IPv6 [2] https://trac.torproject.org/projects/tor/query?keywords=~ipv6 -- Linus

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