- tor-dev - lists.torproject.org

Fwd: Plan of attack for part (c)
by Watson Ladd 17 Feb '12

17 Feb '12

I'm forwarding the following 2 messages about work that I'm thinking about doing to the Tor code to pave the way towards multiple cryptographic methods for route extension. Feel free to comment critically on the proposed design, especially if it impacts areas you are working on or know about. If you have alternative ideas that's also good. Sincerely, Watson Ladd ---------- Forwarded message ---------- From: Robert Ransom <rransom.8774(a)gmail.com> Date: Thu, Feb 16, 2012 at 8:03 PM Subject: Fwd: Plan of attack for part (c) To: Nick Mathewson <nickm(a)torproject.org>, George Kadianakis <desnacked(a)riseup.net> Cc: Watson Ladd <watsonbladd(a)gmail.com> Forwarding to Nick and George (who has looked at the crypto code before), because I'm not going to be able to think about this much today. This sort of discussion should probably be on the tor-dev mailing list. ---------- Forwarded message ---------- From: Watson Ladd <watsonbladd(a)gmail.com> Date: Thu, 16 Feb 2012 13:15:58 -0600 Subject: Plan of attack for part (c) To: "rransom.8774" <rransom.8774(a)gmail.com> Dear Robert, I've come up with the following sketch of a plan to handle the obstacle of crypt_path_t to multiple negotiation methods. It isn't actually the problem. The problem is the crypto_dh_t * dh_handshake_state. I propose defining an enum handshake_methods_t and a handshake_state that looks like typedef struct { enum method; union { crypto_dh_t *dh_handshake; } u; } handshake_state; The extend_info_t structure will need to be modified to point to a list of similar handshake_key structures, probably in the form of a linked list. This involves modifying the functions that allocate extend_info_t's, of which thankfully there are few. Once this is done we can genericize the onion_skin functions by making new functions which essentially consist of a switch statement on the value of method. One unresolved issue is selecting the method to be used when multiple methods are available: I'll probably just take the first handshake_key and complain if it doesn't match what the handshake_state should be when processing the response. Servers are a trickier issue, but if they have a list of handshake_keys we can sort through it to find the key that matches a particular method, and rely on the new CREATE2 cell mechanism to tell us what the method is. Are there requirements for a fix that this idea doesn't meet? Any hard decisions that I've made the wrong call on? And thank you very much for taking the time to help me through working with the tor code. Sincerely, Watson Ladd -- "Those who would give up Essential Liberty to purchase a little Temporary Safety deserve neither Liberty nor Safety." -- Benjamin Franklin

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Talk on flash proxies Feb. 17
by David Fifield 13 Feb '12

13 Feb '12

If anyone is interested in the bay area, I'll be giving a short tech talk on flash proxies 6:30–7:00 PM on February 17. Gates Computer Science building room 104 353 Serra Street Stanford, CA 94305 http://infolab.stanford.edu/pub/keller/gates-map.html David Fifield

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Obfsproxy client for Android
by Nathan Freitas 12 Feb '12

12 Feb '12

Thoughts on attempting to port and ship Obfsproxy client functionality to Android? We have a good number of Iranian users it seems, and I think we can pull it off in a few days, if it isn't insanely complex. Where should we begin? Any details on exactly what was done for the new TBB? +n

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First test "report"
by Esteban Manchado Velázquez 12 Feb '12

12 Feb '12

Hi there, I'm done with the first batch of work on the test side. You have the (rebased just now) work here: https://github.com/emanchado/tor/commits/master. The rest of this e-mail summarises what I've done and explains my plan for further work. The content of the commits -------------------------- I have reviewed the whole test_util.c and made three kinds of changes: 1. Added more tests. Some of them failed, and after checking with other people on IRC the conclusion seems to be that they should pass (ie. they reproduce actual bugs in the code). To keep the test suite from failing, they are inside "#if 0" blocks. So someone should look for "#if 0" inside test_util.c and fix the code that makes those fail. Or maybe I should file bugs for those? 2. In comparison assertions, the general convention seems to be to place the expected value first ("test_eq(0, functioncall(...))" rather than "test_eq(functioncall(...), 0)"). I have modified the assertions not following that convention, so they all look the same. 3. General clean up, small code reorganisations, fix typos and such. Eg, I have turned all the "tt_int_op(a, ==, b)" into "test_eq(a, b)". I was thinking of blogging about what I saw (esp. related to point 1). I think there are valuable lessons to be learned, which will help other people writing tests (both for Tor and outside of Tor). I'm not sure if there's enough content for a blog post, but if I do it after all, should I post the link here? Plan for the future ------------------- As I haven't explored coverage yet, I'll start with that for the code in src/common/ and see what I can do. My gut feeling (without having looked at other parts of the code yet!) is that tackling unit tests for code in src/or/ will be hard for me, and it seems better to explain what kind of things I have done in src/common/ so others, more familiar with that code, can fix/improve the unit tests for src/or/*. In other words, it seems much more effective for me to support someone who knows the code in src/or/*, rather than the other way around. After I'm done with what I think is easy enough for me to do with the unit tests, I'll have a look at Stem (Damian's suggestion) and chutney (Nick's suggestion), and decide what I do next. -- Esteban

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Tor developers: completed translations now in separate directories
by Runa A. Sandvik 09 Feb '12

09 Feb '12

Hi everyone, The latest version of the Transifex client allows users to specify a minimum percentage of completeness for the translations to be accepted by the client (that is, to be downloaded). The translation.git repository now has a _completed branch for each of our translation resources. If you only want to include 100% completed translations in your project, clone the _completed branch for your project from now on. -- Runa A. Sandvik

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Proposal xxx: Safe cookie authentication
by Robert Ransom 07 Feb '12

07 Feb '12

See attached, because GMail would wrap lines if I sent it inline. Robert Ransom

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Parallel Crypto - Library dep.
by David Goulet 03 Feb '12

03 Feb '12

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi everyone, To help the tor project, I'll contribute some of my spare time to improve multithreading for the Tor code base. I've speak a bit with Nick M. and it seems the crypto lib is an important part to begin with. The wiki page (https://trac.torproject.org/projects/tor/wiki/org/projects/Tor/Multithreade…) indicates, basically, that a worker thread pool with a work queue to dispatch crypto events should be the right approach and I do agree. Is it acceptable to link an external library to the project being a dependence? The library I'm thinking about is "liburcu" which stands for user-space RCU (http://lttng.org/urcu) It's a complete set of lockless data structure including wait-free queue which can be very useful for our case. It support a large variety of architecture and works on BSD and Linux. The Linux kernel use RCU mechanism for a lot of internal data structure today so it's quite tested and solid. The question I think is do we want lockless data structure in Tor or it's not and will not be necessary for the type of workload ? (lockless re-sizable hash tables, red-black tree, stack, linked-list (double also) and queue are available as of today). Waiting on your feedback guys, either way, I'll begin implementing parallel crypto largely based on the wiki page (really good ideas there). Thanks a lot! David -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQEcBAEBAgAGBQJPKET6AAoJEELoaioR9I02OO0H/2lxrvak2ItAdGsXHsyH2dgz U3ePxZUg8Ix5UuZXA/LnP3T7/HBa47mtPMj3hwuz2Wnarf6FulumYA3A9jKsZyxQ tf6azD+G7CbZjjYPbe8XYfOZC6+x58mF7SciM/maLoFQLzCvw7ruBBXu8j0Ghw5Q hcm8RMIa4UyB0szSpMqkt615sYQBgy7hhEkNKqxnfdP4zIqUIK8mJqBING6r7qU+ EhnIT5VNzKG9FZPkYNzXOvzbtH0MegNfePsi6gDYlkjR7gekiT9wYH9n5tFTPQUu 4BwqaaHR/Wk+zfHaQOmz+KC3eefUqcd+XP82mcPTSUDj4mzG1Sio2ZHKX0IeJVw= =r0da -----END PGP SIGNATURE-----

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Re: [tor-dev] Simulating a slow connection
by Rob Jansen 02 Feb '12

02 Feb '12

> Date: Thu, 26 Jan 2012 16:39:34 +0000 > From: Steven Murdoch <Steven.Murdoch(a)cl.cam.ac.uk> > To: tor-dev(a)lists.torproject.org > Subject: Re: [tor-dev] Simulating a slow connection > Message-ID: <CAE309A8-034E-4E6A-B05C-6B9B3EA1CDBE(a)cl.cam.ac.uk> > Content-Type: text/plain; charset=us-ascii > > Hi Adam, > > On 20 Jan 2012, at 10:55, Adam Katz wrote: > >> Well, I myself didn't have anything specific in mind but i have some >> experience with the linux tc utility as well as with generating >> realistic background traffic. I was wondering whether I could help on >> any of the existing projects or help establish a new one. > > I think Nick's comments summarized the current state of thinking. ExperimenTor and Shadow are the best Tor simulators to use for this project. The big missing pieces are: > - an automated framework for setting up experiments with slow Internet connections with ExperimenTor and Shadow, then collecting and summarizing results > - Tools for generating realistic link characteristics (delay and packet dropping), and for collecting data on the link properties found in particular locations > > Steven. > As Steven stated, this would be very easy to explore with Shadow. The network topology is passed in as an XML file: node properties include bandwidth up/down and link properties include latency, jitter, and packetloss. I already have some python scripts to generate topologies, and would be happy to share them once you have realistic measurements/values for the slow links you'd like to explore. I'd also be happy to explain more about how Shadow works or the structure of the XML file. Rob

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Extending BridgeDB to reallocate bridges from a blocked country to others that do not block.
by Aaron 02 Feb '12

02 Feb '12

The following is a draft proposal of changes to BridgeDB to address the deliverable "Automated bridge allocation to reallocate bridges from a blocked country to others that do not block" (https://trac.torproject.org/projects/tor/wiki/org/sponsors/SponsorE/PhaseTh…) This draft proposes two different approaches -- any feedback or questions are very welcome! --Aaron ==== Filename: xxx-bridgedb-reallocates-bridges.txt Title: BridgeDB Reallocates Bridges Author: Aaron Gibson Created: 15 Jan 2015 Status: Draft Introduction: This proposal outlines the required changes for BridgeDB to reallocate bridges from a blocked country to others that do not block. Current Status: Presently, BridgeDB does not allocate bridges to specific countries. The HTTPS distributor divides bridges into a cluster of rings. Requests for bridges are mapped to a single ring in the cluster using the class C network of the client, so that the IPv4 space is divided amongst the rings in the cluster (presently 4 rings). For an attacker to obtain the complete set of bridges she must control a number of IP addresses in diverse networks. The email based distributor uses a single ring, and bridge buckets are dumped from a single pool of unallocated bridges. Required modifications: 1. BridgeDB must be able to produce an unblocked set of bridges for a specific country, if these bridges are available. 2. If a bridge is blocked in a country, it must be available to users in other countries. BridgeDB could be modified to assign bridges to geographic regions. To do so, the cluster concept must be extended to support 'geographic clusters' of bridges that correspond to a set of country codes, so that requests will be directed to a corresponding cluster, by either automatic geoip detection or by client choice. Alternately, BridgeDB could be modified to guarantee that a client requesting unblocked bridges for a region would receive these bridges, if unblocked bridges exist. Presently, patches exist for BridgeDB that mark known blocked bridges as "Might be blocked", but makes no further effort to respond with unblocked bridges, even if those bridges exist. Proposed Solution 1 Modify BridgeDB to assign bridges to geographic regions. Regions are designated by a list of country codes. Regions should be balanced in size, or proportional to the number of bridge users. If a bridge is blocked in a region, the bridge should be reallocated to another region. Bridges for a region are stored in a cluster of rings. Pitfalls Bridges assigned to one geographic area are not available to clients requesting bridges from other regions. Possible Solution 2 Modify BridgeDB to dynamically produce rings of bridges 'Not blocked in' a specified country. Bridges are not mapped to a specific country or region, but BridgeDB's response would contain only unblocked bridges (if available). Pitfalls As bridges are not allocated to a specific region, bridges could not be reserved for distribution to specific regions. Common pitfalls As BridgeDB learns about blocked bridges that it may no longer provide, BridgeDB replaces blocked bridges with good bridges. An attacker with control over addresses from many class C networks could iteratively request and block bridges, until the entire set has been consumed. The rate of consumption could be limited by the rate that blocked bridges are updated, but clients would be more likely to receive a bridge that has been blocked.

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DNS/DNSSEC resolving in Tor (PoC implementation)
by Ondrej Mikle 01 Feb '12

01 Feb '12

Hi, I decided to give it a shot in implementing full DNS/DNSSEC resolution support for Tor, here's the branch: https://github.com/hiviah/tor ATM the biggest limitation is that reply DNS packet must fit in a single cell (i.e. max size is RELAY_PAYLOAD_SIZE). How it's implemented: There's new command SOCKS_COMMAND_RESOLVE_FULL for SOCKS interface and new cells RELAY_COMMAND_RESOLVE(D)_FULL. The RESOLVE_FULL cell contains query string and RR-type, RESOLVED_FULL just the DNS packet in wire format. Resolving is implemented via libunbound on the relay's side, ldns parses packet on client's side. The tor-resolve now uses the new SOCKS command and accepts -t parameter with RR-type (numeric, default 1 - RR-type 'A'), e.g.: ./src/tools/tor-resolve -t 28 lupa.cz localhost:10050 Packet size: 319 Flags: qr: 1, aa: 0, tc: 0, rd: 1, cd: 0, ra: 1, ad: 1 -- Rcode: NOERROR -- Opcode: QUERY -- Question section lupa.cz. IN AAAA -- Answer section lupa.cz. 600 IN AAAA 2001:67c:68::7b lupa.cz. 600 IN RRSIG AAAA 5 2 600 20121022235305 20111023235305 8130 lupa.cz. wFdVqKCEh4Nmac3v5K9y6HT+aIBAtF4Q9QIqHjlAl/ljp4m5TKkgKCF083zFTMh0LqfwdODfQdSNTKAwO55hyw== -- Authority section lupa.cz. 600 IN NS ns.iinfo.cz. lupa.cz. 600 IN NS ns6.adminit.cz. lupa.cz. 600 IN RRSIG NS 5 2 600 20121022235305 20111023235305 8130 lupa.cz. SpqkpBlK1dzrfACHh3yfUp01Vr/w9qzVYQms4RDXNQZW1Hwr5WYMHIuGrFEgOOrjyg1vB01HENXJf4i2ISx51g== -- Additional section Other implementation notes: - some checks like whether private address is resolved are missing (also a whitelist of allowed RR-types might be implemented) - in the SOCKS5 request, RR-type is hacked onto port number - in SOCKS5 reply, high byte of length is hacked onto SOCKS5 reserved byte - libunbound supports async resolving, for now synchronous is used - there are more details, grep FIXDNS in code - Makefile.am's have -lldns and -lunbound hardwired - new code may not be pretty at some places (getting to know Tor code) Also, this seems to be a bug in relay.c:connection_edge_process_relay_cell_not_open(), the RELAY_COMMAND_RESOLVED case: answer_len = cell->payload[RELAY_HEADER_SIZE+1]; if (rh->length < 2 || answer_len+2>rh->length) {...} Payload is accessed before checking bounds. Ondrej

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