- tor-dev - lists.torproject.org

Development of an HTTP PT
by dardok 25 Nov '13

25 Nov '13

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi, I am quite new in here but I am interested to help and improve the TOR system. I am interested in PTs and particularly in developing a HTTP PT. I've read some papers [0],[1],[2],[3] and the ticket #8676 and I consider that it would be a good idea to make an effort and try to implement the HTTP PT as is stated in the ticket, that is using real browser and server services. After talking with asn, we conclude that a good point to start this development may be to focus on the HTTP transport part, that is to know how to control the browser or the server and how to embed the TOR traffic into the HTTP protocol (requests and responses). Things such as the data obfuscation, the delays in the communications and the packet chopping won't be considered, because it may be used another PT such Scramblesuit to do that task. The CLIENT side: TBB <-> Scramblesuit PT <-> HTTP PT <-> CENSOR NET and the SERVER side: CENSOR NET <-> HTTP PT <-> Scramblesuit PT <-> TOR bridge The important is to know how to embed the TOR traffic already obfuscated into the requests and responses to avoid suspicion. Also as I said before, to know how to control a browser binary to make the HTTP traffic from the client side as much traditional as possible, for instance using a firefox binary or something like that. The same must be applied to the server side, implementing a real NGINX server or an Apache server on port 80 and writting some CGI to classify the traffic incoming from the TOR clients through the HTTP requests. The same server may have another CGI to write and send the HTTP responses to those TOR clients with the traffic into them. I would like to find someone interested to work on this topic. Thanks and I wait for your comments or suggestions! [0] http://www.owlfolio.org/media/2010/05/stegotorus.pdf [1] http://www.cs.kau.se/philwint/pdf/wpes2013.pdf [2] https://www.ieee-security.org/TC/SP2013/papers/4977a065.pdf [3] https://github.com/sjmurdoch/http-transport/blob/master/design.md -----BEGIN PGP SIGNATURE----- iQEcBAEBCgAGBQJSarhoAAoJEFz9RJtDk2+MsnwH/2MugLeUH+EOc6bzyKJ25W/N 5Kf9w1YdU276z5eba6+fY38H6l3hwErT6TaiWcULiVra1JshLLWaTGHS9AiP4Nf3 QTUVjUMQNiqGkLvNBIkxwqe8MQo1d5GgEhul4fYzMKS46clhmkb6lILIfZ4bRDyc 8bctM8qOk7mLVkp9Ip+ehv/J6S4wmSNtKUIj88mUyfRDDXn/+r7OQx+FDoC/3YiL XzFpaeofPgdWb35cieQvR2wWqWN3N5BRK1R7o0g02BfOYEXOxQ2KaIWUqJBiyKqo uzSAkic1a5qDpJImAQhjAVrqZi1NKZbQQM+33caWm8T9fWkNojClQZ2PzbJn0os= =zI1W -----END PGP SIGNATURE-----

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FTE v0.2 Release Candidate
by Kevin P Dyer 25 Nov '13

25 Nov '13

I'm pleased to announce the release candidate of a pluggable transport powered by Format-Transforming Encryption. Cross-platform PTTBBs are available on the FTE website: https://fteproxy.org/download dcf - I've added a patch to ticket #9941. This patch can be applied to [2], to integrate FTE into the PTTBB. My fork is available at [3]. The source code [4] for fteproxy is available on github. -Kevin [1] https://trac.torproject.org/projects/tor/ticket/9941 [2] https://git.torproject.org/pluggable-transports/bundle.git [3] https://github.com/kpdyer/bundle [4] https://github.com/kpdyer/fteproxy

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Re: [tor-dev] bananaphone obfsproxy module
by George Kadianakis 25 Nov '13

25 Nov '13

David Stainton <dstainton415(a)gmail.com> writes: > Hi, > > Yeah... I should add a doc string to the BaseTransport __init__ > explaining that it runs upon connect. > > OK yesterday I implemented transport class method called setup()... > The BananaphoneTransport overrides setup()... storing the markov model > in a class attribute. > I had to modify pyobfsproxy.py and run the class setup() method after > the external cli args are parsed. > > I made it work for external cli mode... by making pyobfsproxy.py run > the setup method for each transport after > args.validation_function(args) runs... because the setup method needs > some args to read the corpus file and build the markov model. > > What should I do to get arguments passed to obfsproxy when running in > managed mode? > Hm. Good question. You probably want to go to obfsproxy/managed/server.py and obfsproxy/managed/client.py and place a strategic run_transport_setup() hook. I would place it before the launch_transport_listener() call. You might also need to use obfsproxy/transports/get_transport_class() somewhere in there. Another nice thing would be if you could pass the pt_config struct in setup(), so that transports can use pt_config elements during initialization. As an example, see how obfs2 configures its shared-secret in its __init__ using getServerTransportOptions(). That could be done in its setup(), I think. Does this make sense? If you don't want to do this coding, I can do it at some point next week. Cheers! ( And while I'm on it, let me tell you about the different ways that you can pass parameters to obfsproxy. I wanted to document this somewhere, and this thread seems like a good excuse :) - External mode: You can pass global parameters to external mode transports by using the register_external_mode_cli() and validate_external_mode_cli() functions. - Managed mode: - Global parameters: These are parameters that are passed to obfsproxy on startup. - Server: On the server-side we can pass global parameters to obfsproxy by using the TOR_PT_SERVER_TRANSPORT_OPTIONS environment variable. Obfsproxy exposes those parameters using the transport_config struct and obfsproxy/common/transport_config.py:getServerTransportOptions . - Client: On the client-side we don't have a way to pass global parameters to obfsproxy yet. If we ever need to, we can do it with environment variables here too. - Per-connection parameters: These are parameters which are supposed to be different for each connection. An example of such a parameter can be a shared-secret used for a specific bridge connection. - Server: On the server-side we don't have a way to pass per-connection parameters at the moment. - Client: On the client-side we pass per-connection parameters using the SOCKS handshake as a covert channel. Transports can retrieve these parameters using the handle_socks_args() method. )

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Fwd: [guardian-dev] Orfox: first step towards Tor Browser on Android
by Nathan Freitas 24 Nov '13

24 Nov '13

First small step towards a true Tor Browser on Android. -------- Original Message -------- Subject: [guardian-dev] Orfox: first step towards Tor Browser on Android Date: Sat, 23 Nov 2013 23:18:30 -0500 From: Nathan of Guardian <nathan(a)guardianproject.info> To: Guardian Dev <guardian-dev(a)lists.mayfirst.org> Since Android 4.4 replaced the guts of the WebView component with Chrome, and there is no apparent way to set a proxy anymore (even through tricks like reflection), I decided to accelerate our move towards an entirely new approach to privacy-enhanced browsing. I discovered two projects that provide a full standalone browser component that you can embed in an app. ChromeView, based on Chromium, and very much a drop-in replacement for WebView: https://github.com/pwnall/chromeview GeckoView, Mozilla's own attempt to turn their browser engine into an Android developer component: http://starkravingfinkle.org/blog/2013/10/geckoview-embedding-gecko-in-your… I started with ChromeView, but got stuck just trying to get it to run. Both approaches require some strange use of putting .so and .pak binaries into asset folders and such. I don't entirely understand why yet. I ended up getting the GeckoView project's GeckoBrowser sample running easily, and very quickly, started hacking in all the privacy-enhancing Firefox "about:config" preferences I know. All the SOCKS and HTTP proxying stuff works well, and I have even gotten to a fairly decent report back on ip-check.info in terms of cookies, referrals, user-agents, etc. You can find the repo here, if you want to build and try yourself. No binaries posted yet: https://github.com/guardianproject/Orfox I am aiming to do a release fairly quickly, at least for the Android 4.4 users who are currently left in a lurch. Otherwise, if anyone wants to help build the best, most secure and privacy-enhancing mobile browser in the world, what we need to do from here is: 1) Start building the GeckoView library from source ourselves, and figure out which components we really need. It is very bloated, and the current APK is humongous. 2) Re-implement Orweb's various preferences into the new Orfox app, so that users can easily choose to turn on/off javascript, clear cookies, and so forth. 3) Connect with Mike Perry of Tor Project and start figuring out how the Firefox patches / modifications he makes for Tor Browser can be applied to the GeckoView builds. Best, Nathan _______________________________________________ Guardian-dev mailing list Post: Guardian-dev(a)lists.mayfirst.org List info: https://lists.mayfirst.org/mailman/listinfo/guardian-dev To Unsubscribe Send email to: Guardian-dev-unsubscribe(a)lists.mayfirst.org Or visit: https://lists.mayfirst.org/mailman/options/guardian-dev/nathan%40guardianpr… You are subscribed as: nathan(a)guardianproject.info

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Pluggable transports meeting tomorrow (Friday 22nd of November 2013)
by George Kadianakis 22 Nov '13

22 Nov '13

Greetings humans, this is an email to remind you that there 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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Help me guague how full your plate is via regular check-in conversations
by Tom Lowenthal 20 Nov '13

20 Nov '13

Hello fighters for freedom, When applying for grants, planning future work, and otherwise thinking about what capacity we have leftover to do things in the future, it's really useful to know who's doing what and how much of it. I get some of this information from our sponsor/project-specific meetings, but it doesn't seem to be the full picture, so I'd like to trot out that old chestnut of regular one-on-one chats. This means that I'd like to spend between thirty and sixty minutes talking with each of you, once every week or two. I'd like to calibrate the frequency so that we can get calls down to 30 minutes each, with room to kvetch and have a conversation that's a little more than just rattling off deliverable status and time assignments. I think that the right group for this is the folks who post to tor-reports. If you post to tor-reports, please get back to me by the end of the week with your availability for a regular weekly check-in, as well as any thoughts you have about medium, format, or anything else. If you're not currently on tor-reports and think you should check in, or vice versa, you should probably drop me a line too. Any questions or suggestions? -Tom

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Proposal 223: Ace: Improved circuit-creation key exchange
by Nick Mathewson 20 Nov '13

20 Nov '13

Hi, all! Here's Esfandiar Mohammadi's proposal for the Ace handshake. It should have been added as a numbered proposal back in July; I think I lost track of everything while the dev meeting was happening. Please let me know if you have more proposals that should be assigned numbers but haven't gotten one yet. Filename: 223-ace-handshake.txt Title: Ace: Improved circuit-creation key exchange Author: Esfandiar Mohammadi Created: 22-July-2013 Status: Open History: 22-July-2013 -- Submitted 20-Nov-2013 -- Reformatted slightly, wrapped lines, added references, adjusted the KDF [nickm] Summary: This is an attempt to translate the proposed circuit handshake from "Ace: An Efficient Key-Exchange Protocol for Onion Routing" by Backes, Kate, and Mohammadi into a Tor proposal format. The specification assumes an implementation of scalar multiplication and addition of two curve elements, as in Robert Ransom's celator library. Notation: Let a|b be the concatenation of a with b. Let H(x,t) be a tweakable hash function of output width H_LENGTH bytes. Let t_mac, t_key, and t_verify be a set of arbitrarily-chosen tweaks for the hash function. Let EXP(a,b) be a^b in some appropriate group G where the appropriate DH parameters hold. Let's say elements of this group, when represented as byte strings, are all G_LENGTH bytes long. Let's say we are using a generator g for this group. Let MUTLIEXPONEN (a,b,c,d) be (a^b)*(c^d) in some appropriate group G where the appropriate DH parameters hold. Let's say elements of this group, when represented as byte strings, are all G_LENGTH bytes long. Let's say we are using a generator g for this group. Let PROTOID be a string designating this variant of the protocol. Let KEYID be a collision-resistant (but not necessarily preimage-resistant) hash function on members of G, of output length H_LENGTH bytes. Instantiation: Let's call this PROTOID "ace-curve25519-ed-uncompressed-sha256-1" Set H(x,t) == HMAC_SHA256 with message x and key t. So H_LENGTH == 32. Set t_mac == PROTOID | ":mac" t_key == PROTOID | ":key" t_verify == PROTOID | ":verify" Set EXP(a,b) == scalar_mult_curve25519(a,b), MUTLIEXPONEN(a,b) == dblscalarmult_curve25519(a,b,c,d), and g == 9 . Set KEYID(B) == B. (We don't need to use a hash function here, since our keys are already very short. It is trivially collision-resistant, since KEYID(A)==KEYID(B) iff A==B.) Protocol: Take a router with identity key digest ID. As setup, the router generates a secret key b, and a public onion key B = EXP(g,b). The router publishes B in its server descriptor. To send a create cell, the client generates two keypairs of x_1, X_1=EXP(g,x_1) and x_2, X_2=EXP(g,x_2) and sends a CREATE cell with contents: NODEID: ID -- H_LENGTH bytes KEYID: KEYID(B) -- H_LENGTH bytes CLIENT_PK: X_1, X_2 -- 2 x G_LENGTH bytes The server checks X_1, X_2, generates a keypair of y, Y=EXP(g,y) and computes point = MUTLIEXPONEN(X_1,y,X_2,b) secret_input = point | ID | B | X_1 | X_2 | Y | PROTOID KEY_SEED = H(secret_input | "Key Seed", t_key) KEY_VERIFY = H(secret_input | "HMac Seed", t_verify) auth_input = ID | Y | X_1 | X_2 | PROTOID | "Server" The server sends a CREATED cell containing: SERVER_PK: Y -- G_LENGTH bytes AUTH: H(auth_input, KEY_VERIFY) -- H_LENGTH bytes The client then checks Y, and computes point = MUTLIEXPONEN(Y,x_1,B,x_2) secret_input = | ID | B | X_1 | X_2 | Y | PROTOID KEY_SEED = H(secret_input | "Key Seed", t_key) KEY_VERIFY = H(secret_input | "HMac Seed", t_verify) auth_input = ID | B | Y | X_1 | X_2 | PROTOID | "Server" The client verifies that AUTH == H(auth_input, KEY_VERIFY). Both parties now have a shared value for KEY_SEED. They expand this into the keys needed for the Tor relay protocol. Key expansion: When using this handshake, clients and servers should expand keys using HKDF as with the ntor handshake today. See also: http://www.infsec.cs.uni-saarland.de/~mohammadi/ace/ace.html for implementations, academic paper, and benchmarking code.

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Transport composition
by George Kadianakis 19 Nov '13

19 Nov '13

Hello Kevin, If you are interested in learning more about the transport combiner idea we were recently discussing, check out trac tickets #10061, #9744 and #7167. It would be awesome if you could comment with any ideas or criticisms you have. Cheers!

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Development Calendar
by Tom Lowenthal 18 Nov '13

18 Nov '13

Hello humans, I know that meetings and scheduling are a pain. That sucks. Here's a calendar of our regular meetings, which might make it easier: <https://www.google.com/calendar/embed?src=1gf7r9dh4bcv0vc926ipq5177g%40grou…> I hope that helps a bit. Here are some thoughts. It's a Google calendar. Yeah, about that. Calendars are hard, and I couldn't find anything free and open that seemed as easy and convenient as Google calendar. If you know of something FLOSS that's as easy and convenient, you should tell me, and help me move it over. In the mean time, you don't need a Google account to use it, and you can read it on the web or with an iCal feed. Complaints and suggestions welcome. Access/collaboration. I think you need a Google account to editing things. If you have a Google account and you want to edit this thing, drop me a line with a blurb and a Google account adress. I'll add you. If you don't have a Google account, fear not too hard. If you email me, I'll add something to the calendar for you. Here are things you should include in your email: * title for the event/meeting; * timezone, start, and end times; * location, IRC channel, phone access procedure, or whatever; * repeat schedule; * any content or description for the body; and * anything else you think is important. Updates. This calendar should remain accurate, especially for meetings which I plan or am at. I use it as *my* primary calendar of public Tor meetings, so it'll always represent my current view of the universe. Anything else? -Tom

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obfsproxy buffering
by David Stainton 18 Nov '13

18 Nov '13

Hi, I noticed that because the obfsproxy api can sometimes buffer and resend smaller chunks of data. My simple use of Nacl stream_crypto to wrap each incoming data buffers will not work... that is because the client and server must keep synchronized nonce counters for the decrypt/encrypt to work... and in this case the client may send one large buffer and the server may receive many smaller buffers... trying to decrypt them with different nonces will of course fail. https://github.com/david415/obfsproxy/tree/david-nacl-stream-withoutkeyexch… It seems like the solution is to write a super simple "framing protocol"... which is to say that I can first send a frame length; and on the receiving end simply read until frame length worth of data is consumed... and then apply the crypto_stream cipher on that frame with the correct corresponding nonce. David

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