- tor-dev - lists.torproject.org

Criteria for prioritizing pluggable transport work
by Roger Dingledine 30 Sep '13

30 Sep '13

Below is my first go at a list of criteria to consider when evaluating pluggable transports for readiness of deployment to users. The goal isn't to say that every transport has to "pass" each question -- rather, I'm hoping to fund a researcher-developer at some point soon to polish some of the research prototypes so we can include them in the PT TBB, and I wanted to think about guidelines for how they should prioritize which PTs to work on. What points is it missing? What points does it mis-… [View More]explain? See also George's "How the pluggable transports factory works" mail: https://lists.torproject.org/pipermail/tor-dev/2013-August/005231.html Thanks! --Roger ---- Section one, how reviewed / reviewable is it: 1) Is the software published, and is it entirely free and open source? Some designs call for non-free (and non-distributable) components like Skype, a copy of Windows in a VM image, etc. 2) Is there a published design document, including a threat model? Is there a specification? How testable are its security / unblockability claims? We should also consider how much peer review the design has received, and whether the project is getting continued attention by its inventors. 3) What is its deployment history? What kind of users did it have and how many? How much publicity? Did it get blocked? Section two, evaluation of design: 4) How difficult or expensive will it be to block the design (by protocol, by endpoints, etc)? For example, what services or protocols does it rely on being usable or reachable? Expense could include actual cost or could include collateral damage. Another way to measure might be the fraction of censoring countries where the technique is expected to work. 5) What anonymity improvements does the design provide, if any? While many pluggable transports focus only on reachability and leave anonymity properties to Tor, some research designs use the pluggable transport interface to experiment with improved traffic analysis resistance, such as by adding padding to defend better against website fingerprinting attacks. 6) What's the bandwidth overhead? Some transports like Obfsproxy don't inflate communication size, while others like Stegotorus wrap their communications in a more innocuous protocol at a cost of sending and receiving more bytes. Designs with higher bandwidth overhead can provide better blocking-resistance, but are also less suited for low-bandwidth environments. 7) Scanning-resistance: how does the design fare against active probing attacks, like China's follow-up connections that test for vanilla Tor traffic? ("How the Great Firewall of China is Blocking Tor", Philipp Winter, FOCI 2012). Section three, evaluation of implementation: 8) Does the implementation use Tor's Pluggable Transport (PT) Application Programming Interface (API) already? Tor has a standard recommended approach so transport modules can be invoked and managed by the Tor process. The PT API also allows Tor to automatically publish capabilities of the transport, collect user and usage statistics from the transport, and so on. 9) Is the implementation cross-platform (Windows, OS X, Linux at least)? How about support for mobile platforms? 10) How easy is the build process, and how easy is deployment and scaling? For example, what software libraries does it require, how likely are we to get enough bridge-side addresses, etc? 11) How is the code from a security and maintainability perspective? Are there unit tests, integration tests, etc? While the underlying Tor channel provides security properties like encryption and authentication, pluggable transports can still introduce new security risks if designed or built improperly. [View Less]

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Announcing liballium (A C Tor Pluggable Transports Utility Library)
by Yawning Angel 30 Sep '13

30 Sep '13

Hello, For those aspiring Pluggable Transports authors out there, I've recently written a simple library that handles the Tor Pluggable Transport Configuration protocol. The idea is for this library to be the C/C++ equivalent to pyptlib (and maybe more, depending on how much time I have to work on it). The code is available at: https://github.com/Yawning/liballium It still needs more documentation, but all of the use cases are covered by a reasonably well commented example (examples/… [View More]

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HTTPS Server Impersonation
by Rohit 30 Sep '13

30 Sep '13

Hi, I was thinking about proposal #203 (Avoiding censorship by impersonating an HTTPS server) and have a few thoughts. I'm not sure if I've understood how everything fits correctly but here goes: For each bridge, we give their identity fingerprint and a shared secret along with their IP address and port. ie: bridge <ipaddress:port> <fingerprint> <shared_secret> The fingerprint allows the client to verify the identity of the bridge (via signed certificate) while a TLS … [View More]

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Damian's Status Report - September 2013
by Damian Johnson 30 Sep '13

30 Sep '13

Hi all. Present status: gobbling birthday carrot cake. Before that, though, did a few things worth noting in September... ====================================================================== Stem: Connection Resolution Support ====================================================================== Stem can now provide you with the active connections belonging to a process. This is similar to arm, capable of doing lookups via seven *nix and FreeBSD resolution methods... https://stem.… [View More]

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File verification GUI tool
by Sherief Alaa 29 Sep '13

29 Sep '13

Hi Everyone, (moving this email from the support-team ML to tor-dev as Runa suggested.) I am starting to work on a small GUI tool for file verification because I find guiding users through the verification process on Windows/Mac through the command line painful. Tools in use: - Python 3.3 or 2.7 (still didn't decide yet). - PyQT - python-gnupg-0.3.5 I might also add a log window and a save log button to see what went wrong during the verification process. Attached is a draft design of how … [View More]

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Re: [tor-dev] Pluggable Transport Browser Bundle FTE Integration
by David Fifield 29 Sep '13

29 Sep '13

On Sun, Sep 01, 2013 at 01:32:23PM +0300, George Kadianakis wrote: > Kevin P Dyer <kpdyer(a)gmail.com> writes: > > === How do we invoke PTs? > > I had this discussion with Roger, but I don't see any open tickets or clear > > discussion on this already. If we have N>1 PTs and at least one bridge per > > PT, how do we select which PT (and which bridge associated with that PT) to > > use? Determinism is bad because then only one PT is used. Booting up all … [View More]> > PTs is bad, especially if (say) the PTs make network connections prior to > > any incoming SOCKS connections. Selecting a random PT is potentially bad, > > too, depending upon how hostile and persistent and stateful the adversary > > is. > > That's an interesting question. I'm not sure if the process of Tor > picking bridges is deterministic or not. I should test it out. David > might know. > > (A good scenario would be that Tor treats bridges like guards and > selects some at random to build circuits.) I don't know how Tor decides which PT bridges to use. I would guess that it treats them like any other Bridge lines in torrc. You should see this ticket and blog post: "Config option to declare whether you're using bridges for reachability or for security" https://trac.torproject.org/projects/tor/ticket/4624 https://blog.torproject.org/blog/different-ways-use-bridge The idea behind it is that some users want covertness (I need to hide the fact that I am using Tor), and some users want reachability (I need some way to circumvent the firewall). The way I see it, the unstated policy of the PT bundles is to optimize for reachability. By default we launch all the transports we know about, so for example if three transports are blocked and one gets through, that is a success. This doesn't work for the first kind of user, for whom a blocked transport means they have been detected. This first kind of user is likely to have to take some extraordinary steps while using Tor in any case. I don't think we have a plan for how to make a bundle that, in its default configuration, is safe to use for all such users. However we can make a bundle that does reachability with no special configuration, so that's what we're doing. The new 3.0 series bundles ask you, on startup, whether you are able to connect directly to Tor or whether you have to do your own manual configuration (like adding bridges). The option to launch only one specific safe transport could in principle be added to such a UI. David Fifield [View Less]

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Help make the Tor stackexchange beta succeed
by Roger Dingledine 28 Sep '13

28 Sep '13

Hello Tor developers and anonymity researchers, Our Stackexchange beta is underway: http://area51.stackexchange.com/proposals/56447/tor and we could use some more participation from actual Tor developers, anonymity researchers, and so on. The goals include a) building a good set of answers to questions around Tor research and development, and b) growing a larger army of people who know these answers and can answer more such questions. If you can help out, please send me mail off-list, … [View More]

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New GPG key for Mike Perry
by Mike Perry 27 Sep '13

27 Sep '13

Hi everyone, I've finally made a new GPG key (after a scant 7 years!). This new key will be used to sign email from me going forward, and will be used to sign software releases until such time as I get around to creating a second set of keys on a hardware token for that purpose. While I dislike the Web of Trust for a number of reasons*, my plan is to cross-certify these two sets of new keys, and also sign both with my old key. Hence I will not immediately be issuing a revocation for my old … [View More]

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[tahoe-dev] the GNU 30th Birthday party!
by Eugen Leitl 27 Sep '13

27 Sep '13

----- Forwarded message from Zooko O'Whielacronx <zookog(a)gmail.com> ----- Date: Fri, 27 Sep 2013 05:00:04 +0000 From: Zooko O'Whielacronx <zookog(a)gmail.com> To: tahoe-dev <tahoe-dev(a)tahoe-lafs.org> Subject: [tahoe-dev] the GNU 30th Birthday party! Folks: Tahoe-LAFS is one of the featured projects at the GNU 30th Birthday Party Hackathon! https://www.gnu.org/gnu30/celebration I'm going to be there in person in Cambridge. What I want to do during the Hackathon is make … [View More]

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Pluggable transport biweekly meeting - Friday Sept 27
by vmonmoonshine＠gmail.com 27 Sep '13

27 Sep '13

Hello PT devs, We'll have our next meeting (almost) today Friday - Sept 27 at CEST: 18:00 BST (Summer GMT): 17:00 UTC: 16:00 EST: 12:00 MNT: 10:00 PST: 9:00 @ #tor-dev on irc.oftc.net As last time asn is going to take us through this after identifying the participant we go one by one and update the group about our recent progress and blockers. As people suggested last time after update we will have a brief code review session when each of us will take at piece of code of another … [View More]

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