tor-dev

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5 participants
3594 discussions

obfs4 questions
by Michael Rogers 29 Nov '14

29 Nov '14

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Hi, In the obfs4 spec I couldn't find a description of how the secretbox nonces for the frames are constructed. A 16-byte nonce prefix comes from the KDF, but what about the remaining 8 (presumably frame-specific) bytes? If an attacker changes the order of the secretboxes so that the recipient tries to open a secretbox with the wrong nonce, is that guaranteed to fail, as it would if the secretbox had been modified? I can make a hand-wavy argument for why I think it will fail, but I don't know whether the secretbox construct is designed to ensure this. Any particular reason for using two different MACs (HMAC-SHA256-128 for the handshake, Poly1305 for the frames) and two different hashes (SHA-256 for the handshake, SipHash-2-4 for obfuscation)? Cheers, Michael -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBCAAGBQJUeHO0AAoJEBEET9GfxSfMcPEH/iEYxlXtceeG3/wzp97oW/He lPNqqowyXczlyJO0SDG8L96hG6RYQZb7M0t8KJsYJapAznioZi2/qRQEC2/VFXg1 1EN//Bd9iO7QUXaIo1djC97Qoq3qmR/GY50xKYIjxr/gZSLk2dAAtleFUuerBrl9 nLrTr7kSKk3xzY0GFYtYKbj3bvuGusGrFioAIgfnKtF8iAlSjEIo8uE2Y1RFVu2d Q9GOake1VjC5V7Ue/MDCpWagwebPhnDHXSCWSXhvrYT5rmkjrkR2nhl2hAIq/0pA sfjsGquMrT5fdXcRrQaxHsamCt1228/ZlEAkCep/PRpS0NgLDJlRtPe49RD44Gk= =OHtY -----END PGP SIGNATURE-----

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Stormy - request for feedback
by Griffin Boyce 28 Nov '14

28 Nov '14

Hello all, So as some of you know, I've been working on installers for hidden services, to ideally make very common services (such as blogs and plain websites) easy to deploy and automatically update. This is a very rough version of the one-click hidden service installer, but I'd love to get feedback on places where it breaks and where it could use a major structural change. Script is here, please feel free to flag bugs or tell me how I'm doing it wrong: https://github.com/glamrock/Stormy/blob/master/one-click-blog.sh Q: Can I use this right now to set up a hidden service? A: Please don't use this in production until firewall settings are in place. Q: Are there firewall settings in place? A: Not yet - the current setup is entirely for development and should not be used as-is. best, Griffin -- "I believe that usability is a security concern; systems that do not pay close attention to the human interaction factors involved risk failing to provide security by failing to attract users." ~Len Sassaman

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The Sniper Attack: Anonymously Deanonymizing and Disabling the Tor Network
by Liste 27 Nov '14

27 Nov '14

http://www.nrl.navy.mil/itd/chacs/biblio/sniper-attack-anonymously-deanonym…

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Potential projects for SponsorR (Hidden Services)
by George Kadianakis 27 Nov '14

27 Nov '14

Hello, this is an attempt to collect tasks that should be done for SponsorR. You can find the SponsorR page here: https://trac.torproject.org/projects/tor/wiki/org/sponsors/SponsorR I'm going to focus only on the subset of those categories that Roger/David told me are the most important for the sponsor. These are: - Safe statistics collection - Tor controller API improvements - Performance improvements - Opt-in HS indexing service I haven't yet split projects into deliverables; this is a middle step to getting there. Next step is to filter and then ticketify what we have. After that we need to prioritize and pick the projects that will become deliverables. In each category, I have slightly ordered the items (so, more important items will usually be on the top, but that's not always true). I have also tried to include all the tickets that are marked as SponsorR in trac. So, let's go: == Safe statistics collection == We've discussed this quite a bit over the past year and I think we all pretty much agree on which stats are safe to collect and which not. I think we all agree that collecting the number of HS circuits and traffic volume from RPs (#13192) is harmless [0] and useful information to have. We need to clean up Roger's patch to add that information in extra-info descriptors, and then do some visualisations. That would give us a good idea of how much HSes are used. OTOH, other statistics like "# of HS descriptors" are not that harmless and the upcoming HS redesign will block us from getting this information anyway. For now, I think we should focus on #13192 for this project. == Tor controller API improvements == To better refine this project, we should think about what we want to get out of it. Here are some outcomes: a) A better control API allows us to perform better performance measurements for HSes. Karsten in #1944 worked on performance measurements of HS circuit establishment. You can find his very useful results here: http://ec2-54-92-231-52.compute-1.amazonaws.com/ We should understand exactly how Karsten is gathering those events, and see whether we can improve the timing accuracy or if we are missing any events. We need to also figure out how to do useful measurements in causal events like the race between the INTRODUCE_ACK cell and the RENDEZVOUS2. We also need to find a way to match rendezvous circuits with introduction circuits: https://trac.torproject.org/projects/tor/ticket/1944#comment:35 All in all, this seems like a project worth doing right because it will be useful in the future. It can even act as an automated regression test. b) This might also be a good time to start working on automated integration tests for HSes. It should be possible to spin up private Chutney networks and test that particular HSes are reachable. Or perform regression tests; for example, Roger recently suggested writing a regression test to make sure that clocks don't need to be synchronized to build HS circuits (#13494). We should also make testing networks better for HS testing: - #13401 TestingTorNetwork should crank down RendPostPeriod too? c) Tor should better expose error messages of failed operations. For example, this could allow TBB to inform users whether they mistyped the onion address or the HS is actually down, and it would also let us do #13208. Proposal 229 and ticket #13212 are related to this. We should see whether the PT team is planning to implement proposal 229 and how we can synchronise. d) There are various projects that are using HSes these days (TorChat, Pond, GlobaLeaks, Ricochet, etc.). We should think whether we want to support these use cases and how we can make their life easier. For example, Fabio has been asking for a way to spin up HSes using the control port (#5976). What other features do people want from the control port? And here are some more tickets marked as SponsorR from this category: - #8993 Better hidden service support on Tor control interface - #13206 Write up walkthrough of control port events when accessing a hidden service - #2554 extend torperf to record hidden service time components == Performance Improvements == This is the most juicy section. How can we make HS performance better? IIUC, we are mainly interested in client-side performance, but if a change makes both sides faster that's even better. Some projects: a) Looking at Karsten's #1944 results http://ec2-54-92-231-52.compute-1.amazonaws.com/ we see that fetching HS descriptors takes much more time than it should. I wonder why this is the case. Is there another ntohl bug there? We should perform measurements and get a good understanding of what's going on in this step. Here are some tickets that Roger opened to do exactly that: - #13208 What's the average number of hsdir fetches before we get the hsdesc? - #13209 Write a hidden service hsdir health measurer And here is a ticket with a potential issue: - #13207 Is rend_cache_clean_v2_descs_as_dir cutoff crazy high? b) Improving the other parts of the circuit establishment process is also important: - #8239 Hidden services should try harder to reuse their old intro points - #3733 Tor should abandon rendezvous circuits that cause a client request to time out - #13222 Clients accessing a hidden service can establish their rend point in parallel to fetching the hsdesc Furthermore, an area of Tor that might give us better performance but we haven't really explored yet is preemptive circuits. #13239 is about building more internal circuits for HSes. And here is a ticket suggesting more measurements: - #13194 Track time between ESTABLISH_RENDEZVOUS and RENDEZVOUS1 cell c) Another important project in this area is parallelizing HS crypto. I haven't looked at what this would actually entail, but it will probably involve implementing the undone parts of proposal 220/224. d) This might be the time to implement Encrypted Services? Many people have been asking for this feature and this might be the right time to do it: https://gitweb.torproject.org/torspec.git/blob/HEAD:/proposals/ideas/xxx-en… e) Following the trail of #13207, we should look at all the magic numbers currently used by HSes, document them and see if they make sense. This includes the number of IPs (#8950), the number of HSDirs/replicas, the intro point expiration date, etc. Also, we should revisit the flags used when doing path selection for RPs, IPs, etc. f) On a more researchy tone, this might also be a good point to start poking at the HS scalability project since it will really affect HS performance. We should look at Christopher Baines' ideas and write a Tor proposal out of them: https://lists.torproject.org/pipermail/tor-dev/2014-April/006788.html https://lists.torproject.org/pipermail/tor-dev/2014-May/006812.html Last time I looked, Christopher's ideas required implementing proposal225 and #8239. g) All the projects above are aiming at improving circuit establishment performance, but none of them are dealing with performance improvements after the HS circuit has been established. On an even more researchy tone, Qingping Hou et al wrote a proposal to reduce the length of HS circuits to 5 hops (down from 6). You can find their proposal here: https://lists.torproject.org/pipermail/tor-dev/2014-February/006198.html The project is crazy and dangerous and needs lots of analysis, but it's something worth considering. Maybe this is a good time to do this analysis? h) Back to the community again. There have recently appeared a few messaging protocols that are inherently using HSes to provide link layer confidentiality and anonymity [1]. Examples include Pond, Ricochet and TorChat. Some of these applications are creating one or more HSes per user, with the assumption that HSes are something easy to make and there is no problem in having lots of them. People are wondering how well these applications scale and whether they are using the Tor network the right way. See John Brooks' mail for a small analysis: https://moderncrypto.org/mail-archive/messaging/2014/000434.html It might be worth researching these use cases to see how well Tor supports them and how they can be supported better (or whether they are a bad idea entirely). == Opt-in HS indexing service == This seems like a fun project that can be used in various ways in the future. Of course, the feature must remain opt-in so that only services that want to be public will surface. For this project, we could make some sort of 'HS authority' which collects HS information (the HS descriptor?) from volunteering HSes. It's unclear who will run an HS authority; maybe we can work with ahmia so that they integrate it in their infrastructure? If we are more experimental, we can even build a basic petname system using the HS authority [2]. Maybe just a "simple" NAME <-> PUBKEY database where HSes can register themselves in a FIFO fashion. This might cause tons of domain camping and attempts for dirty sybil attacks, but it might develop into something useful. Worst case we can shut it down and call the experiment done? AFAIK, I2P has been doing something similar at https://geti2p.net/en/docs/naming == Security / Miscellaneous == I also noticed that some tickets on trac were assigned to SponsorR but I couldn't fit them in the above categories. They are mainly security enhancements or code improvements. Here is a dump of the tickets: Security: - #13214 HS clients don't validate descriptor-id returned by HSDir - #7803 Clients shouldn't send timestamps in INTRODUCE1 cells - #8243 Getting the HSDir flag should require more effort - #2715 Is rephist-calculated uptime the right metric for HSDir assignment? Miscellaneous: - #13223 Refactor rend_client_refetch_v2_renddesc() - #13287 Investigate mysterious 24-hour lump in hsdir desc fetches - #8902 Rumors that hidden services have trouble scaling to 100 concurrent connections == Epilogue == What useful projects/tickets did I forget here? Which tasks from the above we should not do? I just went ahead and wrote down all the projects I could think of, with the idea that we will filter stuff later. Thanks! Footnotes: [0]: since RPs are picked at random by the client and not by the HS. [1]: see https://moderncrypto.org/mail-archive/messaging/2014/000434.html [2]: or if someone is more crazy, try to integrate GNUnet's GNS: https://gnunet.org/gns

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Malicious relays and honeypots
by Gareth Owen 26 Nov '14

26 Nov '14

Hi all I wonder if it might be worth having a discussion on how to detect malicious and/or suspicious relays. To my knowledge, the project currently only scans for MITM and tries to detect larger Sybil attacks (but doesn't always act when detected). We have a lot of knowledge now about types of attacks and the unusual behaviours that might present if they are being deployed. For example: 1) Relays changing their ident every 24 hours are likely trying to be in a position to be the directory node for a HS (there are several of these relays active today). 2) Many relays being launched on sequential IP addresses, and/or with two nodes per IP - again - likely intercepting DHT publications or Sybil. 3) I have spotted several times a large number of relays in the same subnet, or adjacent /24 subnets. You could extend this to ASes. 4) Honeypot relays that try to spot unusual cells or traffic patterns traversing the tor network. For example, this could have detected the RELAY_EARLY attack if it was based on a different code base. One could define very robust and tight rules for what is permitted - flagging nodes sending unusual traffic. Additionally, PADDING cells are not currently used by the official client but are used very widely in traffic confirmation attacks - whilst intermediate relays wont be able to detect this, clients can and could flag it with an authority (via a 3-hop circuit). 5) One could scan for unusual descriptors being returned too - e.g., the descriptor is currently with in tight size bounds - but one could pad with bytes to support traffic confirmation if PADDING cells are put on the red flag list. 6) We also have the wider question of traffic tampering by exits, like the recent binary patching exit which I believe was not detected by the project. 7) And finally, Exits that only exit ports which permit tampering - e.g. the exits that only exit Bitcoin traffic for example. The question of course is where is the threshold and what does one do in the event of one of these.. Personally I am of the view that suspicious relays are not worth keeping in favour of diversity - but that view does contradict the project's I think. Best Gareth -- Dr Gareth Owen Senior Lecturer Forensic Computing Course Leader School of Computing, University of Portsmouth *Office:* BK1.25 *Tel:* +44 (0)2392 84 (6423) *Web*: ghowen.me

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Re: [tor-dev] Feedback on obfuscating hidden-service statistics
by George Kadianakis 25 Nov '14

25 Nov '14

"A. Johnson" <aaron.m.johnson(a)nrl.navy.mil> writes: >>>> George and I have been working on a small proposal to add two >>>> hidden-service related statistics: number of hidden services and >>>> total hidden-service traffic. >>> >>> Great, I’m starting to focus more on this project now. Well, >>> actually I’m going on a trip for a week today, but *then* I’m >>> focusing more on this project :-) >> >> Sounds great! We're meeting every Tuesday at 16:00 UTC in #tor-dev. >> Feel free to drop by. > > Excellent. I won’t be there this coming Tuesday, but I’ll be there the next Tuesday. > >> Replicas mean that each descriptor is stored under two identifiers, so >> that's two places. Further, descriptor identifiers change once per >> day, so during a 24-hour period, there are up to four descriptor >> identifiers for a hidden service. > > That makes sense. It would be nice if the statistics would allow you > to identify how long (i.e. how many hour periods) each descriptor was > observed being published. That would allow us to figure out if there > are lots of short-lived services or fewer long-lived > services. Publishing statistics every hour would pretty much take care > of this. If you are really set on 24 hours, then perhaps you could add > the total number of published descriptors in addition to the number of > *unique* published descriptors. > > Also, my suggestion about using additive noise applies equally well to > the descriptor statistics. And multiplicative noise is a *bad idea* if > you don’t have some adjustment for small values (e.g. 10% noise of a 0 > value is 0, and 10% of 1 is only 0.1). > >> We have been thinking about many more hidden-service related >> statistics in a separate document. We're currently discussing whether >> we should turn it into a tech report, because we'll probably not want >> to implement most of those statistics. If you have remarks or more >> ideas, please feel free to edit the document. We're going to have a >> public review round for this, too, but that might not happen in the >> next week or two. >> >> https://etherpad.wikimedia.org/p/hs_stats_78281091 > > Great! I think we should go for at least a little more data in the > current proposal (what is the timeline for this, btw?). I think we > should come up with a list of statistics we might imagine gathering > and identify the subset of those that we’re comfortable gathering at > this point. For example, I think failure statistics is much more > innocuous than other data, and those would be very useful. For > example, they would help us understand how to improve the protocol is > failing, and it might help us identify misuse of hidden services > (e.g. by botnets clients stupidly looking for non-existent descriptors > or by malicious crawlers attempting to brute force descriptors). So > here are some ideas: > 1. Number of fetch requests for descriptors that don’t exist (number of fetch requests that do succeed would of course be very useful as well) > 2. Number of descriptor publishes to the wrong HSDir (actually I suspect that the HSDir doesn’t check this and wants to be accepting of any publish) > 3. Number of rendezvous circuits that never connect (from the RP perspective) > 4. Number of rendezvous circuits on which no data cells are ever sent > (CC'ed [tor-dev]) Thanks for the input Aaron! The timeline here is that we are hoping the proposal _and_ the implementation to be ready by mid-December. Then we are hoping that we can deploy the code to a few relays so that we have some data by January. So, time is tight. I'm currently OK with the two statistics in: https://people.torproject.org/~karsten/volatile/238-hs-relay-stats.txt I feel that any other statistics will need to be carefully analyzed. We should add the ideas you mentioned in the etherpad, and get them included in the tech report (which we are also hoping to have ready in some form by mid-January). The tech report is supposed to contain and analyze most of the HS statistics we can think of. It will likely contain many stats that we will never do, but also some stats that might be a good idea. The good ones we should eventually integrate to the Tor proposal and write code for. >> Thanks for the very valuable input! Let me know if the following >> draft looks okay, and I'll start another thread on tor-dev@. >> >> https://people.torproject.org/~karsten/volatile/238-hs-relay-stats-2014-11-… > > "Lab(\epsilon/C)” -> "Lap(\epsilon/C)” (that was my mistake. I think > having the added noise both parameterized and included in the reported > statistics is an idea worth thinking about. Making it a parameter > allows you to easily change it without upgrading. Including it in the > statistics would allow us to correct better for noise if different > relays might be adding different amounts of noise due to inconsistent > opinions of the noise parameter (if this should never happen, then I > guess this wouldn’t be necessary). > > So again, sorry that I’m not going to be very responsive on this for the next week. I’m really happy that you’re working on it! > > Best, > Aaron

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botnets+tor
by Enkidu Mo Shiri 25 Nov '14

25 Nov '14

nowadays using tor by botnet developers is bringing risk to tor network. the use hidden service feature in tor network ,install their IRC server and by hiding behind relays,packet encryption and layers of tor, control and command botnets and use them for attacks. 1.i am researching about any possibility if i can differentiate between botnet traffic and normal tor network traffic by sniffing and analysing network traffic at gateway of my campus. 2.any idea about this technique: i run a botnet in my computer (sandbox) attach a script to it(developed by myself) ang let botneet works. the botmaster (hacker) receives botnet report( after it pass by 2 relays) and my script runs in his computer and sends me his system information. 3. have a question about tor network structure: how many nodes are between user A 9 outside tor) and user B( in internet but outside tor) ? i dont their communication will pass by two nodes(relay) but what other node? how does hidden service provide service to them? any authentication stuff? sorry if its not related to this mailing list. *Ehsan Moshiri (Enkidu)* *Digital Forensic And Penetration testing Researcher * *H/P:+96 111 2868 696* *Linkedin: http://my.linkedin.com/pub/enkidu-moshiri/59/baa/90b/ <http://my.linkedin.com/pub/enkidu-moshiri/59/baa/90b/>* *Facebook: Enkidu Oshiri* *wechat: Enkidu-Moshiri* *whatsapp&viber:+961112868696*

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[PATCH] Pinning middle nodes for HSes: anti-guard-discovery
by George Kadianakis 25 Nov '14

25 Nov '14

Hello, inspired by the recent discussions on guard discovery, I went ahead and implemented a small patch for Tor that tries to help defend against Hidden Service guard discovery attacks. It basically allows the operator to specify a set of nodes that will be pinned as middle nodes in Hidden Service rendezvous circuits. The option only affects HS rendezvous circuits and nothing else. Of course, it doesn't fix guard discovery, it just pushes guard discovery to the next hop, so that they need to compromise two boxes to win. You can find my branch in 'sticky_mids' at https://git.torproject.org/user/asn/tor.git . (Here it is in HTTP shape: https://gitweb.torproject.org/user/asn/tor.git/shortlog/refs/heads/sticky_m… ) I don't expect this to be merged in mainline Tor, but if any HS operators feel like they need it, here it is. I coded it fast and it seems to work for me, but please inform me of any bugs. You can use it by adding a line like this in your torrc: """ HSRendezvousMiddleNodes TorLand1 """ (BTW, I'm not advocating TorLand1, it's just a random relay name I thought of. Please use your own web of trust.)

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doc/HARDENING Draft
by Libertas 24 Nov '14

24 Nov '14

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 I thought I'd share an initial draft of doc/HARDENING. Please share any opinions or contributions you have. This was written in a little more than an hour, so it's still a work in progress. However, in the spirit of prototyping before polishing, I thought I'd share early. Here's the relevant ticket: https://trac.torproject.org/projects/tor/ticket/13703 A specific topic of conversation is how much of the advice should be in the document itself as opposed to linked sources. It could also use more OS diversity. After reading it, you can probably guess which *nix flavors I'm familiar with. Enjoy, Libertas -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCAAGBQJUc7qtAAoJELxHvGCsI27NOwsP/1bP+g4W2y1NHefR5bd+5hwo V927TXzarNneNFxfhKJsVewVnU593Ex13iHv+WgA+XM39xiK8KkhpxOaw2IpahZp pIRCk4/XX78YaEc/K3ci2AsNGFVXPBX7nm4/VOZ5qiGfo+FVeipykweF1dF+X1Wc 1wr8Q9LWKoIab+klu/BG5nG5NtwICYslbgXMvNnapHuy0Xn1+fvBx3mW9teMkJ0N Npssiy7XUqJx1XpdYNJr4XI28aHOV2p4FeCdsAgaQ1OBkOvpzMd+fw2Yb3FOiX/l 5pNCPMXFsS/+OXp1qOFKDQoOb7fEP6mY4NqdSovuJU0oWdurnHVk/X3SidALfH/L vFPdTwpCJSMLuYO7HsLLiLx6LkDtrDZ2y9+tUfpqKGAN0upXrIi5GWsbUeLcCqwY UFYdSg1GHsWJz7fU6F1vDLpGsiXU5yVqgaxfP06+nZ/smRt5sA3nlMDCZJi3BDes k0+c4+tAPZ5Yt6kJ5b1GBgxQMokDqnLm/4pb/qlp0EzDfhWpA+Un2lGdvInrz1ds VsVvbq/LLuxYylC3hlF8pNxBVMdbXycWM1w/VHtDjPZFdo9AO4CJHXeShYQa2O0W cBXdU+O59wWoxiCuEfo0O2xaJw2UIRfxauQbcp/A0rg8FKU1c2QeP2t7y8VdVC1Y SgQNVCUKYPBMCywJw9PA =yY3r -----END PGP SIGNATURE-----

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Next OONI weekly meetings
by Arturo Filastò 24 Nov '14

24 Nov '14

Hello Oonitarians, Sorry for not sending this email sooner, but this week has been a bit hectic. A couple of people have said that they cannot attend the weekly meeting on thursday at 18:00, because it conflicts with another recurring appointment they have. For this reason I am going to suggest we reschedule the next OONI meetings to a date that works for everybody. Monday and Tuesdays seem to be the best option, so I am going to propose we skip next weeks meeting and instead opt for holding next weeks one on either a Monday or Tuesday at 18:00 UTC, 19:00 CET, 13:00 EST, 12:00 CST, 10:00:00 PST. How does this sound for everybody? I personally would prefer Monday over Tuesday, but if you would instead prefer Tuesday please send a reply to the ooni-dev mailing list. If nobody replies I am going to assume every Monday works for you all and the next meeting will be on Monday 24th of November. Have fun! ~ Arturo

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