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A few questions about defenses against particular attacks
by Yuhao Dong 14 Mar '14

14 Mar '14

Hi, I am currently working on a personal project implementing an onion-router, vaguely similar to Tor (let's just call it Oor, other onion router, for the moment), and I have a few questions about attacks, which I think are not really protected by Tor, and whether my solution could possibly work. Of course, if Tor defends against such attacks, then please enlighten me. - Traffic volume correlation. Tor's FAQ says that it doesn't plan on defending against an adversary monitoring traffic volumes flowing through the Tor network. Oor tries to protect against this attack by: - Obfuscating every single link with a protocol derived by Tor's obfs3 protocol - No public list of all node addresses; this makes determining whether certain traffic is Oor traffic much harder. More at the next bulletpoint - Splitting each circuit (termed "onion stew") into many subcircuits, all terminating at the same exit node. à la multipath TCP. Cells going through the subcircuits have a randomly-determined *uneven *distribution of choice of subcircuit, barring attackers from deducing total traffic from observing one subcircuit. - Blanket blacklist attacks by censors. Censors can poll the directory and block all ordinary Tor nodes. (obfsproxy) bridges are a workaround. - Oor's directory maintains a *graph* of all nodes. Each node knows the public keys of all the other nodes, but each node only knows the addresses of *adjacent* nodes. - Note that this allows (sub)circuit-building along any path in the graph. The "extend circuit" command takes the next node's public key as the parameter, rather than the address. - This reduces the bootstrapping problem to distributing (an alias of) the directory server address. Unlike with Tor bridges, this does not create a bandwidth bottleneck, and no nodes need to be reserved for a special pool of bridges, unable to be used by usual users. Bridges often go offline, but this would work until the alias is blocked. However, as with Tor bridges, things like e-mail can be used to distribute many dynamically-generated aliases of the directory server. - Protocol recognition. In "free" countries like the US of A, Tor users see no pressure to use obfuscated bridges. Tor traffic is rather easily distinguished, and could be used to form suspicion on people. Even with obfsproxy, Tor's constant 512-byte cell length may be an issue. The "Stegotorus" paper presents a filter that finds cell lengths typical of Tor. - Every link is obfuscated in oor with obfs3. - obfs3 happens to create various cell lengths. This would be a problem for Tor-like circuits because it doesn't hide data sizes at all, but I think that breaking circuits into subcircuits solves this problem. There is a not-really-working but readable PoC implementation of everything except the "onion stewing" part, i.e. circuits can only work with one subcircuit, athttps://github.com/quantum1423/kirisurf-dev/ Current work is underway to rewrite a more robust version with various repos at https://github.com/KirisurfProject/ (yes, it is currently called Kirisurf, oor is just for short previously, and I want to change the kirisurf name anyways. You may find a "kirisurf" on sourceforge. That is a simple one-hop encrypted proxy I made a long time ago just for breaking censorship without privacy protection; Kirisurf gradually grew onion-routing things until I decided to redesign it; namechange probably needed to prevent misleading version numbers) I would be interested to know what research has been done on these areas in Tor (to avoid reinventing the wheel), and whether any of my ideas are novel. Thanks!

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Fwd: [Twisted-Python] Tor Project has GSoC projects which need Twisted developers!
by isis 14 Mar '14

14 Mar '14

I sent this to the Twisted mailing list at twisted-python(a)twistedmatrix.com -- ♥Ⓐ isis agora lovecruft _________________________________________________________ GPG: 4096R/A3ADB67A2CDB8B35 Current Keys: https://blog.patternsinthevoid.net/isis.txt

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Pluggable transports meeting tomorrow (Friday 14th of March 2014)
by George Kadianakis 13 Mar '14

13 Mar '14

Greetings humans, this is an email to remind you that the regular biweekly pluggable transports meeting is going to happen tomorrow. Place is the #tor-dev IRC channel in OFTC. Time is 17:00 UTC. Cheers!

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GSoC - Search Engine for Hidden services
by Nurmi, Juha 13 Mar '14

13 Mar '14

Hi All, Ahmia.fi interested in participating in GSoC. Ahmia.fi's back-end is designed by Kordex (Mikko Kortelainen) and I (Juha Nurmi) have built the front-end. In practise, I will apply as a student. Also, kordex might apply. Ahmia.fi is a HS search engine that needs improvements. At the moment, we are using YaCy in the back-end and have developed Django based front-end (Python). Kordex is a Customer Service Architect, CEO of the Fail-Safe IT solutions and software designer. I am a research, postgraduate student and university lecturer. I have a long work experience with web services. At the moment, ahmia.fi has integration to Tor2web and Globaleaks. We have hidden service online cheker, RESTful API for the resources, tested idea how hidden services could publish their information ( https://ahmia.fi/documentation/descriptionProposal/) and a lot of good ideas. Unfortunately, we do not have any funding. We would like to release the source code of ahmia.fi and develop our search engine in GSoC. Greetings Juha Nurmi

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GoSC - Website Fingerprinting project
by Marc Juarez 12 Mar '14

12 Mar '14

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi all, I'm a PhD student at COSIC (COmputer Security and Industrial Cryptography) in KU Leuven, Belgium. My research topic is related to network traffic analysis and I'm now focused in the more specific problem of website fingerprinting (http://homes.esat.kuleuven.be/~mjuarezm/) I think website fingerprinting is one of the most threatening attacks to Tor because it can be deployed with moderate resources and the information that can be extracted as a result is highly sensitive (e.g., browsing history). It basically defeats one of the main privacy guarantees offered by Tor which is unlinkability between sender and recipient or, in this particular case, between the user and the web server. However, I couldn't find any open project that tackles this problem in https://www.torproject.org/getinvolved/volunteer.html.en#Projects. That is why I'd like to propose a GoSC project for the implementation of tools (packages, classes, etc.) that contribute in the development of a countermeasure against this attack. Regarding countermeasures, since Tor is oriented to low-latency applications like web browsing, delaying strategies are unacceptable and, therefore, they must necessarily be based on link-padding. Link-padding normally incurs in high bandwidth overheads, however the increasing broadband bandwidth capacity available makes it a relevant feasible defence. Some capabilities for link-padding have been already specified for Tor by Steven Murdoch (https://gitweb.torproject.org/torspec.git?a=blob_plain;hb=HEAD;f=tor-spec.t…, Section 7.2). This functionality is very useful for such a countermeasure but more sophisticated protocols are required for countermeasures that try to adjust the bandwidth overhead. There are several proposed countermeasures based on link-padding that strive for such a trade-off that might be interesting to implement: - Congestion-Sensitive BuFLO (http://arxiv.org/abs/1401.6022) - Adaptive Padding (http://freehaven.net/anonbib/cache/ShWa-Timing06.pdf) Both countermeasures have some building blocks in common (e.g., a control logic to adapt padding under some specific conditions and reduce the overhead). The core of the project would be to implement them in the most general way as possible so they can be useful for other link-padding applications. For example, to implement the basis for a statistical model in the onion proxy and the entry guard that generates the appropriate cover traffic in both directions, where ?appropriate? would be abstracted as it would be defined by each specific countermeasure. I would like to have some feedback from the Tor developers about this project (advices, comments..). I plan to specify it in more detail in the application and to start coding some module that could be shown. But I would like to know if the underlying idea is something that could be of interest for the community. Also, as a PhD student I'm also committed with my research group during the summer so I would like to know if I could work as a part-time student. Best, - -- marc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJTHe+dAAoJEGfJ5xfgazlxYewH/jHv3843o0lQHpHksur86dih u1MtFOpo3RvzdOLNAjdMpnV14Giy8cg0mIcYdCgwCy8jyUgBS5ipX49582Tmf6FT sPYYWOSIBEJVG3DYsD2PwU+XJAiyR9GqdiMiP9MeCJHWP33TBL5hY1TExBejiH+J XsAWo8D2MkzycKITF1leuX4n2eCqncDIy+owU4faYIRj5wPtqwztWDX4ErfdFhws sb/wLF8Wb0tKio/ybkuy5UZeJi0UBF9hAh5UJfZRSllfMFN9g29pJPmTsenMTBS0 XxEEG8gNjHgxpV4rkcTMQBeNp+CAEBsZ7qjxo6IXvLIe0P6zutyQysu9hJCvvY4= =AZG8 -----END PGP SIGNATURE-----

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Weekly Tor dev meeting today, in 90 minutes. (19:00 UTC!)
by Nick Mathewson 12 Mar '14

12 Mar '14

Oh dear. Daylight Savings Time has struck again. The dev meeting this week needs to be at 19:00 UTC, so that I can be done by 4 pm. If you can make it then, great! Else, next week at 19:00 UTC. yrs, -- Nick

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Minutes from Weather rewrite meeting on March 5
by Karsten Loesing 12 Mar '14

12 Mar '14

- only participants today: baumanno and karsten - karsten starts reporting what he did since last meeting - karsten reviewed two tickets - karsten wrote down GSoC idea (u. Rewrite Tor Weather on https://www.torproject.org/getinvolved/volunteer.html.en#Projects) - karsten defined criteria for sending out welcome mails using Onionoo's details documents (#11084) - baumanno starts reporting what he did since last meeting - baumanno closed issue reported by karsten on GitHub repo - baumanno and karsten agreed that there should be unit tests in weather; baumanno is going to create a ticket for this after the meeting; there should be some unit testing framework that plays well with Django - baumanno used most of the existing weather code for scraping emails from relay descriptors - baumanno went on to begin implementation of the welcome script, which leads to #11084 - baumanno notes that we're still missing the script nufuk is working on; baumanno is going to ping him via email and suggest that either feverDream or baumanno takes over - baumanno and karsten wonder how far feverDream is with the vagrant box; this will be very useful to have - baumanno says that utility scripts are ready, so that branching off stable weather would make sense - karsten asked tor's git admins for a user/karsten/weather.git repo that we can use as new stable for now; this is going to be much easier than for feverDream or baumanno to ask for a repo on tor's git - baumanno is going to keep tickets open until we merged them into user/karsten/weather.git - baumanno will create a new branch from atagar's weather repo, add commits, push to a new branch on github, and comment on a trac ticket to pull/review/merge; he's going to cc karsten on the ticket - next meeting is next wednesday at 18:00 utc

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Re: [tor-dev] Volunteering
by Damian Johnson 11 Mar '14

11 Mar '14

> Hi, > > I've been directed to this email address by Matt in regards to volunteering > for the project. Currently I work as a consultant that specialises in > providing hosted services to my clients. I am a keen learner of technology > and have learnt (mostly self taught) various languages (C/C++, python, > Java), where I would like to further improve my knowledge through > volunteering for the Tor project. > > I've browsed through the list of project currently available and have > watched the video, although I cannot decide which project currently > interests me the most. In the past I had used Vidalia when I worked in China > with some limited success, which could be something that I can look to help > upon if possible. > > Thanks, > > Jialu Hi Jialu, glad you want to get involved! Adding tor-dev@ in case the wider community wants to chime in with ideas. The first step of getting involved is to figure out what strikes your fancy and that, obviously, nobody but you can decide. ;) Since you mentioned Vidalia one thing you might want to consider is if you like to work on projects alone or collaborate with others. I include the 'Activity' column on... https://www.torproject.org/getinvolved/volunteer.html.en#Projects ... so you can easily determine for any given project if you would be working with others or adopting a space all your own. Vidalia is firmly in the later camp. Nobody has been actively working on Vidalia for almost a year since chiiph departed. If GUIs strike your fancy then a project you might want to consider is a new stem-based UI. This is an idea we've been batting around for a while now but has yet to get off the ground. Kamran created a python GTK UI a few years back as part of GSoC... http://inspirated.com/2011/07/17/summer-of-code-progress-garm-0-1 This piggybacked on arm, but since his work our controller libraries have greatly improved to a point where we should be able to make a solid, new Tor GUI without that sort of kludge. Like Vidalia, though, nobody else is working in this space so it would involve taking the lead on a new project of your own. If any of the projects on the volunteer table strike your fancy then my best suggestion is to dive in and get involved. Try to fix a minor issue or two then reach out to the maintainer mentioned on the table. Cheers! -Damian

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Mockup for a hidden services publishing tool
by Matt Pagan 10 Mar '14

10 Mar '14

Please see the image file for what I have in mind here. http://oi62.tinypic.com/10x80ok.jpg I hope this tool, when completed, can help reduce the barrier for people seeking to set up hidden services. I anticipate this tool being able to connect to a running tor and write to that tor's torrc file. This tool will be able to connect to the network through a proxy, a standard bridge, or a pluggable transport. It will be able to send a HUP signal to tor. It will be able to read from tor's hidden service directory and tor's log. This mockup was made with wxPython 2.8. This is partially because I'm somewhat familiar with wxWidgets already, and partially because I thought incorporating stem might be a good plan. Here are some pitfalls and shortcomings: * * * By it's current design, this tool has less functionality than Vidalia. As a security property, there's no interface for setting up a relay. This tool's primary focus will be running a hidden service. By it's current design, this tool does not ship with any hosting software. The tool will inform the user that she still needs to run XAMPP or ApacheGUI to host a web page. There's no interface for setting up or designing a blog, only for hosting one that's already designed. I'm still investigating Python's multithreading capabilities so that the Tor log can be continuously read and reported. If I discovered that I didn't need a controller library at all, I'd consider using wxGo instead of wxPython (although writing in Go would be a new experience for me and would take longer). * * * Perhaps some or all of these shortcomings could be overcome given time and community feedback. I'm still not entirely sure where to take this project, if anywhere. Before I get much further with this idea, is this project worth pursuing at all? Does this look like something that could benefit Tor users, given that Vidalia still works for many people? Do you think this tool has potential to function as a point-click-publish hidden services software?

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Re: [tor-dev] [tor-commits] [flashproxy/master] remove failed connections from proxy_pairs as well
by David Fifield 10 Mar '14

10 Mar '14

On Fri, Mar 07, 2014 at 02:39:18PM +0000, infinity0(a)torproject.org wrote: > commit 05b9c101ba9afe4653d1eff6f5414f90f22ef042 > Author: Ximin Luo <infinity0(a)torproject.org> > Date: Fri Mar 7 13:39:31 2014 +0000 > > remove failed connections from proxy_pairs as well > - this is a pretty major fix, as the previous behaviour effectively disabled a proxy after 5 failed connections (= max_num_proxy_pairs / 2) Can you say some more about the circumstances of this fix? What behavior changed for you after making it? I can't reproduce what's described in the commit message. With 9dea0c6c90dedc868dfaa84add2bfa19a2039281, I set up a phony facilitator with ncat -v -lk 7000 --sh-exec "./facilitator.py" where facilitator.py has the contents #!/usr/bin/env python import random import sys port = random.randint(10000,11000) print "HTTP/1.0 200 OK\r" print "Content-Type: application/x-www-form-urlencoded\r" print "Cache-Control: no-cache\r" print "Access-Control-Allow-Origin: *\r" print "\r" sys.stdout.write("check-back-in=10&client=127.0.0.1:"+str(port)+"&relay=173.255.221.44:9901") I then browse to file:///home/david/flashproxy/proxy/embed.html?debug&facilitator=http://127.0.0.1:7000&initial_facilitator_poll_interval=1&unsafe_logging&max_clients=2 All the "client" connections are going to closed ports, but the "Client: error" lines still appear and clients don't accumulate in the request URL. The same happens if I use an open port with a Ncat listener that just closes the connection. The same happens if I change to a non-listening Internet address like 1.1.1.1. 2014-03-10T16:28:48.173Z | Starting; will contact facilitator in 1 seconds. 2014-03-10T16:28:49.179Z | Facilitator: connecting to http://127.0.0.1:7000?r=1&transport=websocket. 2014-03-10T16:28:49.203Z | Next check in 10 seconds. 2014-03-10T16:28:49.204Z | Facilitator: got client:{ host: "127.0.0.1", port: 10782 } relay:{ host: "173.255.221.44", port: 9901 }. 2014-03-10T16:28:49.205Z | 127.0.0.1:10782|173.255.221.44:9901 : Client: connecting. 2014-03-10T16:28:49.206Z | 127.0.0.1:10782|173.255.221.44:9901 : Client: connecting. 2014-03-10T16:28:49.207Z | 127.0.0.1:10782|173.255.221.44:9901 : Client: error. 2014-03-10T16:28:49.208Z | 127.0.0.1:10782|173.255.221.44:9901 : Client: closed. 2014-03-10T16:28:49.209Z | Complete. 2014-03-10T16:28:49.209Z | 127.0.0.1:10782|173.255.221.44:9901 : Client: error. 2014-03-10T16:28:49.209Z | 127.0.0.1:10782|173.255.221.44:9901 : Client: closed. 2014-03-10T16:28:49.210Z | Complete. 2014-03-10T16:28:59.205Z | Facilitator: connecting to http://127.0.0.1:7000?r=1&transport=websocket. 2014-03-10T16:28:59.226Z | Next check in 10 seconds. 2014-03-10T16:28:59.227Z | Facilitator: got client:{ host: "127.0.0.1", port: 10221 } relay:{ host: "173.255.221.44", port: 9901 }. 2014-03-10T16:28:59.227Z | 127.0.0.1:10221|173.255.221.44:9901 : Client: connecting. 2014-03-10T16:28:59.227Z | 127.0.0.1:10221|173.255.221.44:9901 : Client: connecting. 2014-03-10T16:28:59.229Z | 127.0.0.1:10221|173.255.221.44:9901 : Client: error. 2014-03-10T16:28:59.229Z | 127.0.0.1:10221|173.255.221.44:9901 : Client: closed. 2014-03-10T16:28:59.230Z | Complete. 2014-03-10T16:28:59.230Z | 127.0.0.1:10221|173.255.221.44:9901 : Client: error. 2014-03-10T16:28:59.230Z | 127.0.0.1:10221|173.255.221.44:9901 : Client: closed. 2014-03-10T16:28:59.231Z | Complete. 2014-03-10T16:29:09.227Z | Facilitator: connecting to http://127.0.0.1:7000?r=1&transport=websocket. 2014-03-10T16:29:09.249Z | Next check in 10 seconds. 2014-03-10T16:29:09.250Z | Facilitator: got client:{ host: "127.0.0.1", port: 10069 } relay:{ host: "173.255.221.44", port: 9901 }. Now what *does* seem to be happening, and what had me confused for a while, is that Firefox seems to be artificially delaying repeated WebSocket connections to the same port with some kind of exponential delay. I originally had a hardcoded port in facilitator.py, and the delay made it appear that something like what the commit message describes was happening. Since WebSocket connections eventually start waiting a long time to fail, it looks like they are not being closed. https://people.torproject.org/~dcf/graphs/firefox-exponential-delay.png is a screenshot showing what looks like exponential growth in the Network panel. Chromium doesn't appear to have the same issue; the requests are linearly spaced in the network pane. Are you able to confirm any of the above? When you discovered the bug, were you testing with Firefox or Chromium? How did you find the bug, and what did you do (differently from the above) to reproduce it? In any case, what's going on must be different than what's described in the commit message, because even before the fix the proxy continues running for me with max_clients=2. David

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