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Feasibility of using a Tor Browser plugin as a PT component?
by David Fifield 16 Mar '14

16 Mar '14

We're making progress on meek (https://trac.torproject.org/projects/tor/wiki/doc/meek) the transport that hides your traffic in HTTPS requests to an unblockable web site. It's already doing a good job at reliably transfering bits. What we'd like to do next is remove trivial means of blocking it based on network fingerprinting. We're currently using the golang HTTPS library, and at https://trac.torproject.org/projects/tor/wiki/doc/meek#Distinguishability you can see meek's TLS differs from Chromium's in its ciphersuites and extensions. It seems the right thing to do is mimic a browser, and I can think of at least three ways to do that: 1. Try really hard, using NSS or some other library, to look like a particular browser. 2. Run a second browser, apart from Tor Browser, that receives commands from a client PT program and makes the HTTPS requests it is commanded to. 3. Run a browser plugin *inside* Tor Browser, that makes HTTPS requests *directly on the Internet, without going through Tor*. That is, the plugin receives commands from the client PT program, and then bypasses all of Tor Browser's proxy settings in order to send HTTPS requests to the web site fronting the circumvention. It's the third option I want to ask about. The first option puts us on the parrot treadmill. The second has the usability and distribution problems of running two browsers at once. The third is slightly crazy, but more usable and easier to deploy. The third option is definitely what I would do if I were using a browser other than Tor Browser and designing purely for circumvention and not anonymity. Is it even possible to run a plugin that bypasses the proxy settings? (I know a binary plugin like Flash can do it--but does that use the browser's HTTP engine or do they cook up their own HTTP with sockets?) Would Tor Browser's customizations, for example the modified User-Agent string, defeat the purpose of looking like an ordinary browser? Anything else I'm missing? This is just brainstorming; negative answers won't be the end of the project. The first option might not be too bad if we use NSS directly. David Fifield

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inTORface - a potential GSoC idea
by Jacek Wielemborek 15 Mar '14

15 Mar '14

Hi, I know there's not much time to apply, but I figured that it's worth asking anyway. I recently gave Tails a try and I have to admit that I wasn't exactly happy with how it routes the traffic through Tor. I basically wanted a ready-to- use airgapped VM and I realized that torsocks doesn't exactly do what I want in all cases. Then I had this idea - wouldn't it be nice to add another virtual NIC to your system that routes all the traffic via Tor and attach a VM to this traffic only? It'd emulate TCP/IP (and maybe some UDP to catch DNS requests) so that if the VM sends a SYN, it notes this fact and tries to establish a real connection. I'm not sure I could hasten to build a prototype, but I wanted to throw the idea there nonetheless. What do you think about it? Yours, Jacek Wielemborek

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GSoC - Tor pluggable transports project
by quinn jarrell 15 Mar '14

15 Mar '14

Hi Tor Devs, I'm a computer engineering undergrad at University of Illinois Urbana-Champaign. I am interested in working on a GSoC pluggable transports project. I mainly code in python or common lisp and have worked with asynchronous programming before (albeit it was a java framework not twisted). The two projects I am interested in are the pluggable transports combiner or building the CBR transport plugin. I really like the idea of the transport combiner but I have a few questions about how far along the design/implementation is. I noticed that there is a prototype called obfs-flash proxy and am wondering if I would work on extending that to work with other plugins or if I would work on a separate combiner. Is the design set in stone yet or is the spec for it still shifting? And if the spec is still shifting, how should I address that in my GSoC proposal. I also talked with Yawning in IRC who pointed me to the CBR transport plugin/unix like plugins to change data length/obfuscate data/add noise. I love the idea that with the combiner a CBR transport could be easily added to any existing transport but if the combiner has not been built/the spec is still developing, I wonder how useful it would be. Also the CBR plugin does not seem to be enough work for a GSoC project but I could definitely be underestimating the difficulty. I would like to work on either of these projects but I do not know which one would be the more helpful/necessary so i would love to hear your opinions on which would be better to work on. Thanks, Quinn

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GSOC Proposal - Improving test coverage in tor
by Punit 15 Mar '14

15 Mar '14

Hello, I have uploaded my GSOC Proposal for the project - "Improving test coverage in tor" at the Melange site. An external link to the same is :- http://punitkoura.github.io/GSOC_proposal.html I would like to know your comments on the same. Thanks, Punit PS - I am working on ConnectionEdge.c in making test cases for connection_edge_process_inbuf function. I will update the proposal when done.

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test_memcpy() on Windows
by Gisle Vanem 14 Mar '14

14 Mar '14

The 'test_memcpy()' in tinytest_demo.c assumes there is a NUL in one of the buffers. (the comment says so). That's not the case here on Windows. At least not in MSVC debug-mode where malloc'ed buffers are filled with '0xCD'. A snippet from my output: ../ext/tinytest_demo.c:159: assert(db->buffer1 < db->buffer2): 537472696E67203000CDCDCDCDCDCDCDCDCDCDCDCDCD ... vs 537472696E67203000CDCDCDCDCDCDCDCDCDCDCDCD ... [memcpy FAILED] I assume this test works on Linux where AFAICS malloc() returns a buffer with zeros. If so, shouldn't calloc() be used in 'setup_data_buffer()' instead? --gv

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[Patch] tinytest_demo.c
by Gisle Vanem 14 Mar '14

14 Mar '14

Since tinytest_demo.c now calls Sleep(), we must include <windows.h>. Patch: --- Git-latest/src/ext/tinytest_demo.c 2014-03-13 20:44:56 +0000 +++ src/ext/tinytest_demo.c 2014-03-14 11:21:56 +0000 @@ -36,7 +36,10 @@ #include <string.h> #include <errno.h> #include <time.h> -#ifndef _WIN32 + +#ifdef _WIN32 +#include <windows.h> +#else #include <unistd.h> #endif -------------- Ref. Nicks commit here: https://gitweb.torproject.org/tor.git/commitdiff/1365ff5b9a04a7da2acc2e52df… --gv

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No IRC meeting to discuss Tor Instant Messaging Bundle today
by Karsten Loesing 14 Mar '14

14 Mar '14

Hi devs, we had an IRC meeting last week, on March 7, to discuss next steps for the Tor Instant Messaging Bundle (TIMB). At the end of that meeting we decided to have another meeting 1 week later, so today. However, there will be no such meeting today! The main reason for today's meeting was to make a decision on an instant messaging client to use in the new bundle. But we already made this decision in internal discussions with the main developers Arlo and Sukhbir. The final decision is that we're going to use Instantbird. The wiki page states some reasons for this decision: https://trac.torproject.org/projects/tor/wiki/org/sponsors/SponsorO/TIMB If you had planned to attend today's meeting to find out how to best help out with the project, please be patient. The project is still in an early state, and we don't have a good list of things that we need help with. Maybe take a look at the Trac tickets in the TIMB component and at the wiki page linked above. There will be IRC meetings in the future to discuss progress on this project, I just can't say when that will be. Thanks for your patience, and thanks for wanting to help out! All the best, Karsten

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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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