June 2012 - tor-dev - lists.torproject.org

Help with pf and iOS
by sid77＠slackware.it 28 Sep '12

28 Sep '12

Hi all, it took me a year or so but I've finally managed to build Tor for iOS with a working support for TransPort, as you can see on: https://github.com/sid77/evelyn/blob/master/tor/make.sh The next natural step is to hack together full device torification as iOS jailbroken devices can run pf (without ALTQ support). I'm not very comfortable with pf and pfctl so my first step was to head out to https://trac.torproject.org/projects/tor/wiki/doc/TransparentProxy#BSDPF looking for some clue. … [View More]

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[GSoC] APAF Report
by Michele Orrù 21 Aug '12

21 Aug '12

Hello, As Daniel suggested, I'm writing this email to keep you updated on my Google Summer of Code Project - APAF. Following the hackathon of the 18-21 May, we reached a working build environment, and a primitive administration page. Below follows a brief update about what is the current status of the software: Development: I've defined what a service really is in terms of implementation, and approached the administration service (the "panel") in such a way that any future application may … [View More]

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First-time tails/tor user feedback
by Andrew Lewman 18 Jul '12

18 Jul '12

I spent the past week in Sweden, attending the Stockholm Internet Forum, http://www.stockholminternetforum.se/, for part of it. I made a number of tails 0.10.2 usb sticks for people on request. I also asked a lot of people their impressions of Tor and Tails. I received a plethora of feedback. All 8 people are involved in the Internet Freedom policy, technology, or freedom of speech communities. They had very different levels of self-assessed technical skill. The 8 people represented 6 countries.… [View More] tldr; 8 people were tested, 8 people had trouble doing simple things with tor browser in Tails. Issues 4-6 are directly related to Tor. And by asked, I mean, I stuck them in front of my laptop, put the usb stick in the computer, and asked them to browse to their favorite site. No one wanted to be video recorded, even if I offered to only record the screen and not audio. Everyone managed to power on the laptop and wait for Tails to boot. # First issue: Language selection The first issue was on the language selection screen. 4 of 8 people were confused why it was called "Debian Live System" and not "Tails Live System". 8 of 8 knew what language selection meant, but weren't sure how this mapped to Tails. # Second issue: wifi and tor browser The tor browser starts up before the wireless is configured. The tor browser then reports a proxy error. With some prompting, all 8 figured out the wifi and then didn't know what to do. Tor does keep trying to load, and takes forever because it needs to download the entire directory. Users have no feedback as to what's going on behind the scenes because vidalia is hidden. 8 of 8 waited patiently for something to happen on the screen. # Third issue: green onion 3 of 8 people saw the green onion appear in the menu bar up top. These three people hovered over it and saw the 'Connected to the Tor Network' message. No one knew to double-click on it to get a menu of other things to do. No one knew to right-click on it to get the drop-down menu. They were presented with the default check.torproject.org 'congratulations' page and then sat there. # Fourth issue: check.tpo is not helpful 8 of 8 people saw the default check.torproject.org site telling them 'congratulations. Your browser is configured to use tor.' 7 of 8 people asked 'where is my browser?' The one who didn't ask this question was already a firefox user and recognized the interface. 0 of 8 understood what the IP address message meant. Comments ranged from 'is that different than my current IP address?' to 'what's an ip address?' As an aside, when showing someone TBB on their own laptop, they saw the check.tpo site, and then went to Safari and started it up. When asked why they did this, the answer was 'safari is my browser. this says your browser is configured to use tor.' No one used the language selections at the bottom of check.tpo, nor even understood why they were there. # Fifth issue: exit relay congestion/failures 8 of 8 people tried to get to their own sites. 'I wonder what my site looks like when I'm anonymous' was the most common comment (5 of 8). For 6 of 8 people, their site didn't load at all, and tor browser reported their site was unreachable. All 6 then tried to go to google search in their own language; meaning google.es, google.se, etc. For 3 of those 6, this didn't work either. They gave up and assumed tor was broken or was censoring their destinations. I intervened, opened the vidalia network map, closed the circuit in question, and asked them to repeat their browsing. 5 of 6 were able to get to their sites now. The one that was not able to had the same exit relay as last time, Amunet1, in a new circuit and just couldn't get anywhere through it. After yet another new circuit, they could get through to everything. The user has no feedback as to why their site didn't work. And tor assumes everything is working fine. When asked "please find a video you like", they all went to youtube. Most of the videos they wanted to see resulted in 'This video is currently unavailable.' 8 of 8 assumed it was because youtube was blocking tor, not because the video is flash-required. 2 of 8 started randomly clicking videos suggested by youtube to see if any of them worked. Eventually, 2 of 8 got videos to work with youtube and were amazed it worked at all. # Sixth issue: no flash, no warning 2 of 8 people had flash apps on their website. 4 of 8 had ad banners that used flash. All were surprised at the red outline with a snake in it appearing instead of their flash apps. None understood what happened. After an explanation, one person suggested changing the red outline with snake to an actual message written inside, along the lines of 'this app blocked for your protection. click here to unblock it.' I explained why that wouldn't work (because there is no flash, java, silverlight plugins installed) and their answer was 'then do not show it at all'. Inside noscript, I unchecked the 'show placeholder..' option and had them browse again. they were happy. It seems if the user cannot do anything about the blocked apps, not showing them may be preferred. # Seventh issue: shutdown I asked all 8 to shutdown tails and let me know when they thought their data was safely no longer on the system. 1 of 8 figured out how to shutdown tails by clicking the big red button in the upper right corner. The rest hit the power button on the laptop. After rebooting, i showed them all they could just pull the usb drive to do it as well. As soon as tails started shutting down, they all assumed everything was safe and tried to power off the laptop. -- Andrew http://tpo.is/contact pgp 0x6B4D6475 [View Less]

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Proposal 203: Avoiding censorship by impersonating an HTTPS server
by Nick Mathewson 11 Jul '12

11 Jul '12

Hi all. Here's a proposal for ticket #5548. Let's discuss! Filename: 203-https-frontend.txt Title: Avoiding censorship by impersonating an HTTPS server Author: Nick Mathewson Created: 24 Jun 2012 Status: Draft Overview: One frequently proposed approach for censorship resistance is that Tor bridges ought to act like another TLS-based service, and deliver traffic to Tor only if the client can demonstrate some shared knowledge with the bridge. In this document, I discuss some … [View More]design considerations for building such systems, and propose a few possible architectures and designs. Background: Most of our previous work on censorship resistance has focused on preventing passive attackers from identifying Tor bridges, or from doing so cheaply. But active attackers exist, and exist in the wild: right now, the most sophisticated censors use their anti-Tor passive attacks only as a first round of filtering before launching a secondary active attack to confirm suspected Tor nodes. One idea we've been talking about for a while is that of having a service that looks like an HTTPS service unless a client does some particular secret thing to prove it is allowed to use it as a Tor bridge. Such a system would still succumb to passive traffic analysis attacks (since the packet timings and sizes for HTTPS don't look that much like Tor), but it would be enough to beat many current censors. Goals and requirements: We should make it impossible for a passive attacker who examines only a few packets at a time to distinguish Tor->Bridge traffic from an HTTPS client talking to an HTTPS server. We should make it impossible for an active attacker talking to the server to tell a Tor bridge server from regular HTTPS server. We should make it impossible for an active attacker who can MITM the server to learn from the client whether it thought it was connecting to an HTTPS server or a Tor bridge. (This implies that an MITM attacker shouldn't be able to learn anything that would help it convince the server to act like a bridge.) It would be nice to minimize the required code changes to Tor, and the required code changes to any other software. It would be good to avoid any requirement of close integration with any particular HTTP or HTTPS implementation. If we're replacing our own profile with that of an HTTPS service, we should do so in a way that lets us use a the profile of a popular HTTPS implementation. Efficiency would be good: layering TLS inside TLS is best avoided if we can. Discussion: We need an actual web server; HTTP and HTTPS are so complicated that there's no practical way to behave in a bug-compatible way with any popular webserver short of running that webserver. More obviously, we need a TLS implementation (or we can't implement HTTPS), and we need a Tor bridge (since that's the whole point of this exercise). So from a top-level point of view, the question becomes: how shall we wire these together? There are three obvious ways; I'll discuss them in turn below. Design #1: TLS in Tor Under this design, Tor accepts HTTPS connections, decides which ones don't look like the Tor protocol, and relays them to a webserver. +--------------------------------------+ +------+ TLS | +------------+ http +-----------+ | | User |<------> | Tor Bridge |<----->| Webserver | | +------+ | +------------+ +-----------+ | | trusted host/network | +--------------------------------------+ This approach would let us use a completely unmodified webserver implementation, but would require the most extensive changes in Tor: we'd need to add yet another flavor to Tor's TLS ice cream parlor, and try to emulate a popular webserver's TLS behavior even more thoroughly. To authenticate, we would need to take a hybrid approach, and begin forwarding traffic to the webserver as soon as soon as a webserver might respond to the traffic. This could be pretty complicated, since it requires us to have a model of how the webserver would respond to any given set of bytes. As a workaround, we might try relaying _all_ input to the webserver, and only replying as Tor in the cases where the website hasn't replied. (This would likely to create recognizable timing patterns, though.) The authentication itself could use a system akin to Tor proposals 189/190, where an early AUTHORIZE cell shows knowledge of a shared secret if the client is a Tor client. Design #2: TLS in the web server +----------------------------------+ +------+ TLS | +------------+ tor0 +-----+ | | User |<------> | Webserver |<------->| Tor | | +------+ | +------------+ +-----+ | | trusted host/network | +----------------------------------+ In this design, we write an Apache module or something that can recognize an authenticator of some kind in an HTTPS header, or recognize a valid AUTHORIZE cell, and respond by forwarding the traffic to a Tor instance. To avoid the efficiency issue of doing an extra local encrypt/decrypt, we need to have the webserver talk to Tor over a local unencrypted connection. (I've denoted this as "tor0" in the diagram above.) For implementation convenience, we might want to implement that as a NULL TLS connection, so that the Tor server code wouldn't have to change except to allow local NULL TLS connections in this configuration. For the Tor handshake to work properly here, we'll need a way for the Tor instance to know which public key the webserver is configured to use. We wouldn't need to support the parts of the Tor link protocol used to authenticate clients to servers: relays shouldn't be using this subsystem at all. The Tor client would need to connect and prove its status as a Tor client. If the client uses some means other then AUTHORIZE cells, or if we want to do the authentication in a pluggable transport, and we therefore decided to offload the responsibility TLS itself to the pluggable transport, that would scare me: Supporting pluggable transports that have the responsibility for TLS would make it fairly easy to mess up the crypto, and I'd rather not have it be so easy to write a pluggable transport that accidentally makes Tor less secure. Design #3: Reverse proxy +----------------------------------+ | +-------+ http +-----------+ | | | |<------>| Webserver | | +------+ TLS | | | +-----------+ | | User |<------> | Proxy | | +------+ | | | tor0 +-----------+ | | | |<------>| Tor | | | +-------+ +-----------+ | | trusted host/network | +----------------------------------+ In this design, we write a server-side proxy to sit in front of Tor and a webserver, or repurpose some existing HTTPS proxy. Its role will be to do TLS, and then forward connections to Tor or the webserver as appropriate. (In the web world, this kind of thing is called a "reverse proxy", so that's the term I'm using here.) To avoid fingerprinting, we should choose a proxy that's already in common use as a TLS frontend for webservers -- nginx, perhaps. Unfortunately, the more popular tools here seem to be pretty complex, and the simpler tools less widely deployed. More investigation would be needed. The authorization considerations would be as in Design #2 above; for the reasons discussed there, it's probably a good idea to build the necessary authorization into Tor itself. I generally like this design best: it lets us isolate the "Check for a valid authenticator and/or a valid or invalid HTTP header, and react accordingly" question to a single program. How to authenticate: The easiest way Designing a good MITM-resistant AUTHORIZE cell, or an equivalent HTTP header, is an open problem that we should solve in proposals 190 and 191 and their successors. I'm calling it out-of-scope here; please see those proposals, their attendant discussion, and their eventual successors How to authenticate: a slightly harder way Some proposals in this vein have in the past suggested a special HTTP header to distinguish Tor connections from non-Tor connections. This could work too, though it would require substantially larger changes on the Tor client's part, would still require the client take measures to avoid MITM attacks, and would also require the client to implement a particular browser's http profile. Some considerations on distinguishability Against a passive eavesdropper, the easiest way to avoid distinguishability in server responses will be to use an actual web server or reverse web proxy's TLS implementation. (Distinguishability based on client TLS use is another topic entirely.) Against an active non-MITM attacker, the best probing attacks will be ones designed to provoke the system in acting in ways different from those in which a webserver would act: responding earlier than a web server would respond, or later, or differently. We need to make sure that, whatever the front-end program is, it answers anything that would qualify as a well-formed or ill-formed HTTP request whenever the web server would. This must mean, for example, that whatever the correct form of client authorization turns out to be, no prefix of that authorization is ever something that the webserver would respond to. With some web servers (I believe), that's as easy as making sure that any valid authenticator isn't too long, and doesn't contain a CR or LF character. With others, the authenticator would need to be a valid HTTP request, with all the attendant difficulty that would raise. Against an attacker who can MITM the bridge, the best attacks will be to wait for clients to connect and see how they behave. In this case, the client probably needs to be able to authenticate the bridge certificate as presented in the initial TLS handshake -- or some other aspect of the TLS handshake if we're feeling insane. If the certificate or handshake isn't as expected, the client should behave as a web browser that's just received a bad TLS certificate. (The alternative there would be to try to impersonate an HTTPS client that has just accepted a self-signed certificate. But that would probably require the Tor client to impersonate a full web browser, which isn't realistic.) Side note: What to put on the webserver? To credibly pretend not to be ourselves, we must pretend to be something else in particular -- and something not easily identifiable or inherently worthless. We should not, for example, have all deployments of this kind use a fixed website, even if that website is the default "Welcome to Apache" configuration: A censor would probably feel that they weren't breaking anything important by blocking all unconfigured websites with nothing on them. Therefore, we should probably conceive of a system like this as "Something to add to your HTTPS website" rather than as a standalone installation. [View Less]

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Tor proposals implemented in Tor 0.2.3.x
by Nick Mathewson 01 Jul '12

01 Jul '12

Hi, all! Since 0.2.3 just entered beta (and will be in release-candidate status soon if I have anything to say about it!) I wanted to put out a summary of the Tor proposals that got merged, to the best of my knowledge, in the Tor 0.2.3.x series. My next email will summarize still-open proposals. (Note on credits: I'm copying the listed credits from the proposals, their acknowledgments sections, and my incredibly lossy memory. But in every case, these designs were improved enormously through … [View More]feedback from the entire Tor community, including some design stalwarts who take the time to give feedback on all nearly all the proposals they see. Thanks to everyone, and apologies to everybody whom I'm forgetting here.) IMPLEMENTED IN 0.2.3.x 110 Avoiding infinite length circuits We started this one a while ago back in 0.2.1.3-alpha. It provides a mechanism to try to limit the resource-multiplier that a DOS attacker can get against the Tor network by building very long circuits, by limiting the maximum circuit length. We had clients implement the new behavior in 0.2.1.3-alpha, and fixed some bugs related to it in the 0.2.2.x series. It's only now that all of the older versions that don't support it are obsolete that we can actually turn on the attack prevention. (Proposal by Roger Dingledine based on ideas by Christian Grothoff.) 158 Clients download consensus + microdescriptors 162 Publish the consensus in multiple flavors In the "Microdescriptors" design, clients download a summary of router descriptors rather than the entire set of signed router descriptors. This can save a large amount of directory bandwidth -- both because microdescriptors are smaller than router descriptors, and because they're designed to change much less frequently. Rather than being signed by the routers themselves, microdescriptors are listed by their digests in a consensus document signed by a threshold of directory authorities. (This change doesn't change the threat model, since a successful attack against either system requires adversary who can subvert a majority of directory authorities.) We anticipate that we might want to serve the consensus in more than one format in the future, so proposal 162 introduces a notion of "consensus flavors" such that any every consensus vote produces a signed consensus in all the formats, caches cache all the formats, and clients download only those they need. (Proposal 158 by Roger Dingledine, revised a bunch by Nick Mathewson. Proposal 162 by Nick Mathewson, influenced by design discussions with Marian on IRC.) 180 Pluggable transports for circumvention We introduce "Pluggable transports": a specified way for Tor bridges and Tor bridge users to configure external programs to obfuscate or re-route traffic to avoid censorship. This is a pretty big deal: it's what lets Tor integrate will with Obfsproxy and similar tools. As we've hoped, having a specified way to integrate with Tor has encouraged others to work on obfuscation tools. Having it ready to go has helped us deal with unexpected censorship events over the past year, and we think that having a couple of other obfuscators up our sleeve will help more in the future. (Proposal by Jacob Appelbaum and Nick Mathewson, with heavy revisions based on George Kadianakis's experience implementing it.) 171 Separate streams across circuits by connection metadata Here's a big security improvement. In earlier versions of Tor, there wasn't a good way to force streams onto separate circuits. This could make for trouble, since all streams sent over the same circuit are definitively linkable by the exit node, and probabilistically linkable by the destinations. (For example, if you make a connection to an SSH host and log into a website over the same circuit, the exit node can learn that the same person has accounts both at the SSH host and the website. If the SSH host and website are colluding, then over time, they can become certain which account on the SSH host corresponds with which activities on the website.) Starting with Tor 0.2.3, we provide a number of ways for users and integrators to tell Tor not to put the two streams on the same circuit. By default, two streams won't go on the same circuit if they arrive at different Tor client ports (one goes to SOCKSPort 9050 and one goes to SOCKSPort 9051); or if they come from different client addresses (one came from 127.0.0.1, the other from 10.0.10.10); or if they provide different username/password information in their SOCKS handshakes. Additionally, you can configure Tor to isolate connections by destination address, destination port, and chosen client protocol. See the manual page for SOCKSPort for more information. (Proposal by Robert Hogan, Jacob Appelbaum, Damon McCoy, and Nick Mathewson, based on ideas from a whole bunch of people.) 174 Optimistic Data for Tor: Server Side 181 Optimistic Data for Tor: Client Side This one is a performance hack that hasn't seen its full impact yet. Starting with Tor 0.2.3.x, clients MAY send data to the exit node before finding out whether the exit has been able to successfully connect to the destination server. Previously, it took an extra round trip for clients to wait to see whether the exit said "Yes, I'm connected" before they were allowed to send data for the exit. This should make connection startup faster in many protocols where the client speaks first (http, https), as more and more client programs gain support for it. (Proposal by Ian Goldberg.) 176 Proposed version-3 link handshake for Tor 184 Miscellaneous changes for a v3 Tor link protocol 187 Reserve a cell type to allow client authorization Here's the crypto-heavy one for 0.2.3. In earlier Tors, we used two different link protocol variants to get the TLS authentication we wanted without being too fingerprintable. In Tor before 0.2.0, we used a "v1" link protocol, where both sides swapped pretty stereotyped certificate chains in the initial handshake, and were as fingerprintable as all get-out. From 0.2.0 through 0.2.2, we've been using a "v2" link protocol, where the connection initiator launched a renegotiation immediately upon making a successful connection. But as anybody who's used TLS renegotiations knows, they are a pain to work with. Moreover, their presence on the wire is visible, and provides another fingerprint for Tor connections. With the new "v3" link protocol, clients perform an initial TLS handshake, and then use that handshake to bootstrap the trust and authentication they wanted in a less fragile, less fingerprintable manner. Proposal 184 made variable-length cells more pratical, and added a variable-length padding type. Since proposal 176 introduced a requirement that no extraneous cells be sent during the handshake, proposal 187 reserves an extra cell type for future use in pre-handshake authentication. (Proposal 176 by Nick Mathewson, based on an earlier idea by Steven Murdoch, with feedback from Gladys Shufflebottom. Proposal 184 by Nick Mathewson. Proposal 187 by Nick Mathewson based on/influenced by discussions with George Kadianakis and Robert Ransom.) 178 Require majority of authorities to vote for consensus parameters This one makes us more robust against a rogue directory authority. Previously, a misbehaving authority could set an integer parameter unilaterally, so long as it was the first to hear of that parameter, or the only one to have an opinion. With this proposal implemented, a larger number of authorities must want to vote on a consensus parameter for any vote on that parameter to take place. (Proposal by Sebastian Hahn.) 179 TLS certificate and parameter normalization This proposal made a bunch of small but important tweaks to try to emit more normal-looking TLS certificates, to help prevent certificate-based fingerprinting. It didn't all get implemented and stable in time for 0.2.3.x; the remainder is now proposal 195. (Proposal by Jacob Appelbaum and Gladys Shufflebottom.) 183 Refill Intervals Tor uses a token-bucket implementation for its rate- limiting strategy. Previously, Tor refilled these token buckets once per second. But this approach seems to have led to choppy behavior, where we exhaust our bandwidth early in the second, and spend the rest of the second sitting around. The new default is 100 msec, but now it's configurable. (Proposal by Florian Tschorsch and Bjorn Scheuermann.) PARTIALLY IMPLEMENTED IN 0.2.3.x 186 Multiple addresses for one OR or bridge We've implemented this to the extent of letting a bridge have a single IPv6 address. Supporting this for regular relays will need to wait for 0.2.4.x. We're still deciding on whether it's worthwhile to allow more than one IPv4 and one IPv6 address. (Proposal by Nick Mathewson, revised based on extensive feeback by Roger Dingledine and Linus Nordberg.) 198 Restore semantics of TLS ClientHello In an attempt to impersonate Firefox clients under the eyes of watchful censors, earlier versions of Tor would sometimes claim to support TLS ciphersuites that they didn't. This would cause trouble if we ever wanted to negotiate a cipher other than those which we happen to know that all Tor clients support, since we can't count on the TLS ClientHello actually telling which ciphers are supported. This proposal provides us with a backward compatible way to migrate ciphersuite lists, emulate new browser fingerprints, and actually use ciphersuites that didn't exist in 2005. The client side of this proposal is implemented in 0.2.3; the server side will have to wait for 0.2.4. (Proposal by Nick Mathewson.) [View Less]

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Open Proposals as of June 2012
by Nick Mathewson 01 Jul '12

01 Jul '12

This list of open Tor proposals is based on one I sent out in May of last year. Since I'd like to do this more regularly, I have added to each description the date when I wrote it. Most of the summaries from older proposals are unchanged since last May; the later ones in the list for 6/2012 I wrote pretty quickly since I want to get out the door tonight for an appointment, but I want to send this list out without further delay. OPEN, DRAFT, AND ACCEPTED PROPOSALS: 117 IPv6 exits … [View More]IPv6 is still the future, but now it's the kind of future that's unevenly distributed. It's time to do this one so that IPv6 traffic can be sent over Tor. It needs updating to work properly with microdescriptors; it also has some open questions about DNS. (6/2012) 127 Relaying dirport requests to Tor download site / website The idea here was to make it easier to fetch and learn about Tor by making it easy for relays to automatically act as proxies to the Tor website. It needs more discussion, and there are some significant details to work out. It's not at all clear whether this is actually a good idea or not. (5/2011) 131 Help users to verify they are using Tor Here's a proposal for making a torcheck-like website more reliable. If anybody wants to pick it up (especially somebody working on torcheck) and see whether it should be reopened or rejected, that would be a fine thing. (5/2011) 132 A Tor Web Service For Verifying Correct Browser Configuration This proposal was meant to give users a way to see if their browser and privoxy (yes, it was a while ago) are correctly configured by running a local webserver on 127.0.0.1. I'm not sure the status here. (5/2011) 133 Incorporate Unreachable ORs into the Tor Network This proposal had an idea for letting ORs that can only make outgoing connections still relay data usefully in the network. It's something we should keep in mind, and it's a pretty neat idea, but it radically changes the network topology. Anybody who wants to analyze new network topologies should definitely have a look. (5/2011) 140 Provide diffs between consensuses This proposal describes a way to transmit less directory traffic by sending only differences between consensuses, rather than the consensuses themselves. It is mainly languishing for lack of an appropriately licensed, well-written, very small, pure-C implementation of the "diff" and "patch" algorithms. (The good diffs seem to be GPL (which we can't use without changing Tor's license), or spaghetti code, or not easily usable as a library, or not written in C, or very large, or some combination of those.) (5/2011) 141 Download server descriptors on demand The idea of this proposal was for clients to only download the consensus, and later ask nodes for their own server descriptors while building the circuit through them. It would make each circuit more time-consuming to build, but make bootstrapping much cheaper. Microdescriptors obsolete a lot of this proposal, and present some difficulties in using in a way compatible with it. (6/2012) 143 Improvements of Distributed Storage for Tor Hidden Service Descriptors Here's a proposal from Karsten about making the hidden service DHT more reliable and secure to use. It could use more discussion and analysis. (5/2011) 144 Increase the diversity of circuits by detecting nodes belonging the same provider This is a version of the good idea, "Let's do routing in a way that tries to keep from routing traffic through the same provider too much!" There are complex issues here that the proposal doesn't completely address, but I think it might be a fine idea for somebody to see how much more we know now than we did in 2008, particularly in light of the relevant paper(s) by Matt Edmann and Paul Syverson. (5/2011) 145 Separate "suitable as a guard" from "suitable as a new guard" Currently, the Guard flag means both "You can use this node as a guard if you need to pick a new guard" and "If this node is currently your guard, you can keep using it as a guard." This proposal tries to separate these two concepts, so that clients can stop picking a router once it is full of existing clients using it as a guard, but the clients currently on it won't all drop it. It's not clear whether this has anonymity issues, and it's not clear whether the imagined performance gains are actually worthwhile. (5/2011) 146 Add new flag to reflect long-term stability From time to time we get the idea of having clients ship with a reasonably recent consensus (or a list of directory mirrors), so instead of bootstrapping from one of the authorities, they can bootstrap from a regular directory cache. The problem here is that by the time the client is run, most of the directory mirrors will be down or will have changed their IP. This proposal tries to address that. It needs analysis based on behavior of actual routers on the network to see whether it could work, and what parameters might work. Nevertheless, we should really do something like this, so that we can ship a list of initial directory mirrors with Tor (possibly via the "fallback consensus" deisgn), so that new bootstrapping Tor clients don't all hammer the directory authorities. (6/2012) 147 Eliminate the need for v2 directories in generating v3 directories This proposal explains a way that we can phase out the vestigial use of v2 directory documents in keeping authorities well-informed enough to generating the v3 consensus. It's still correct; somebody should implement it before the v2 directory code rots any further. (5/2011) 156 Tracking blocked ports on the client side This proposal provides a way for clients to learn which ports they are (and aren't) able to connect to, and connect to the ones that work. It comes with a patch, too. It also lets routers track ports that _they_ can't connect to. I'm a little unconvinced that this will help a great deal: most clients that have some ports blocked will need bridges, not just restriction to a smaller set of ports. This could be good behind restrictive firewalls, though. The router-side part is a little iffy: routers that can't connect to each other violate one of our network topology assumptions, and even if we do want to track failed router->router connections, the routers need to be sure that they aren't fooled into trying to connect repeatedly to a series of nonexistent addresses in an attempt to make them believe that (say) they can't reach port 443. This one is a paradigmatic "open" proposal: it needs more discussion. The patch probably also needs to be ported to 0.2.3.x; it touches some code that has changed. (5/2011) 157 Make certificate downloads specific This proposal added cross-certification and signing-key-specific download URLs for directory authority certificates. It is IIRC mostly implemented on the server side; there are just some SHOULDs that we should turn into MUSTS if all sufficiently old authority certificates are now obsolete, and a client-side portion that we need to implement. (6/2012) 159 Exit Scanning This is an overview of SoaT, with some ideas for how to integrate it into Tor. (5/2011) 162 Publish the consensus in multiple flavors The initial proposal here is done, but more work is needed for forward-compatibility: we'd like to have caches be willing to cache and serve consensus flavors which they do not currently recognize. (6/2012) 164 Reporting the status of server votes This proposal explains a way for authorities to provide a slightly more verbose document that relay operators can use to diagnose reasons that their router was or was not listed in the consensus. These documents would be like slightly more verbose versions of the authorities' votes, and would explain *why* the authority voted as it did. It wouldn't be too hard to implement, and would be a fine project for somebody who wants to get to know the directory code. (5/2011) 165 Easy migration for voting authority sets This is a design for how to change the set of authorities without having a flag day where the authority operators all reconfigure their authorities at once. It needs more discussion. One difficulty here is that we aren't talking much about changing the set of authorities, but that may be a chicken-and-egg issue, since changing the set is so onerous. If anybody is interested, it would be great to move the discussion ahead here. (5/2011) 168 Reduce default circuit window This proposal reduces the default window for circuit sendme cells. I think it's implemented, isn't it? If so, we should make sure that tor-spec.txt is updated and close it.XXXXXXX (5/2011) 172 GETINFO controller option for circuit information 173 GETINFO Option Expansion These would help controllers (particularly arm) provide more useful information about a running Tor process. They're accepted and some parts of 173 are even implemented: somebody just needs to implement the rest. (5/2011) 175 Automatically promoting Tor clients to nodes Here's Steven's proposal for adding a mode between "client mode" and "relay mode" for "self-test to see if you would be a good relay, and if so become one." It didn't get enough attention when it was posted to the list; more people should review it. (5/2011) 177 Abstaining from votes on individual flags Here's my proposal for letting authorities have opinions about some (flag,router) combinations without voting on whether _every_ router should have that flag. It's simple, and I think it's basically right. With more discussion and review, somebody could/should build it for 0.2.4.x, I think. (6/2012) 182 Credit Bucket This proposal suggests an alternative approach to our current token-bucket based rate-limiting, that promises better performance, less buffering insanity, and a possible end to double-gating issues. (6/2012) 185 Directory caches without DirPort The old HTTP directory port feature is no longer used by clients and relays under most circumstances. The proposal explains how we can get rid of the requirement that non-bridge directories have an open directory port. (6/2012) 186 Multiple addresses for one OR or bridge This one is partially implemented, in that bridges can have IPv6 addresses. Still to go: we need to let ORs have IPv6 addresses too. Undecided: is one IPv4 and one IPv6 enough for anybody? (6/2012) 188 Bridge Guards and other anti-enumeration defenses This proposal suggests some ways to make it harder for a relay on the Tor network to enumerate a list of Tor bridges. Worth investigating and possibly implementing. (6/2012) 189 AUTHORIZE and AUTHORIZED cells 190 Bridge Client Authorization Based on a Shared Secret 191 Bridge Detection Resistance against MITM-capable Adversaries Proposal 187 reserved the AUTHORIZE cell type; these proposals suggests how it could work to try to make it harder to probe for Tor bridges. They need more alternatives and attention, and possibly some revision and analysis. (6/2012) 192 Automatically retrieve and store information about bridges This proposal gives an enhancement to the bridge information protocol, where clients remember more things about bridges, and are able to update what they know about them over time. Could help a lot with bridge churn. (6/2012) 194 Mnemonic .onion URLs Here's one of several competing "let's make .onion URLs human-usable" proposals. This one makes sentences using a fixed map. (6/2012) 195 TLS certificate normalization for Tor 0.2.4.x Here's the followup to proposal 179, containing all the parts of proposal 179 that didn't get built, and a couple of other tricks besides to try to make Tor's default protocol less detectable. I'm pretty psychoed about the part where we let relays drop in any any self-signed or CA-issued certificate that they like. (6/2012) 196 Extended ORPort and TransportControlPort Here are some remaining pieces of the pluggable transport protocol that give Tor finer control over the behavior of its transports. (6/2012) 197 Message-based Inter-Controller IPC Channel This proposal is for an architectural enhancement in Tor deployments, where Tor coordinates communications between the various programs (Vidalia, TorBrowser, etc) that are using it. (6/2012) 198 Restore semantics of TLS ClientHello Partially implemented. We have the new client behavior in place in 0.2.3.x, but not the new server behavior which it permits. (6/2012) 199 Integration of BridgeFinder and BridgeFinderHelper Here's a proposal for how Tor can integrate with a client program that finds bridges for it. (6/2012) 200 Adding new, extensible CREATE, EXTEND, and related cells We'd like to moved to better authentication and key agreement mechanisms in future versions of Tor. This proposal gives us an extensible replacement for our current CREATE/CREATED cell mechanism. (6/2012) 201 Make bridges report statistics on daily v3 network status requests Here's a proposal for bridges to better estimate the number of bridge users. (6/2012) [View Less]

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George's status report: June 2012
by George Kadianakis 30 Jun '12

30 Jun '12

Hi, this is a list of some Tor stuff I did during June: - Provided patches for the rest of the tor-0.2.3.x tickets that were reported/assigned by/to me [0]. - Helped set up a mailing list to host daily censorship reports as reported by George Danezis' censorship anomaly detection tool [1]. I hope to speak with George soon to improve and finalize the second version of his script [2]. - Finished coding the automatic port forwarding for transport proxies (#4567). It needs some more … [View More]

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Andrea's status report for June 2012
by andrea＠persephoneslair.org 30 Jun '12

30 Jun '12

So, here's what I've been up to my first couple weeks with Tor: * Interviewed and got hired * Getting up to speed with everything, setting up git repository, etc. * Met ioerror for coffee and key-signing * Got my first patch merged! (bug 5235) * Fixed several other bugs: * 5452 * 5049 * 6028 * 2385 * 5557 * 5238 * Did code reviews for 6226, 6031, 5285, 4195 and 6255 * Talked to NickM about planning for 0.2.4.x, and made some time estimates. -- Andrea Shepard

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TLS warning using static OpenSSL 1.0.1c
by Gino Badouri 29 Jun '12

29 Jun '12

Hi there, My goal is to run Tor on small cluster of embedded mips devices. Because the platform runs on an older version of OpenSSL and libevent I have chosen to statically link them with Tor. So I went ahead to compile the components. I'm aiming at the beta version: 0.2.3.17 OpenSSL 1.0.1c has been build with: ./Configure debian-mipsel shared enable-tlsext zlib-dynamic no-ssl2 libevent-2.0.19-stable has been built with: ./configure --enable-openssl --disable-debug-mode --with-pic And of … [View More]course Tor: ./configure --prefix=/usr --libdir=/usr/lib --localstatedir=/var --sysconfdir=/etc \ --with-zlib-dir=/home/mastag/build-mipsel/tmp/staging/mipsel-linux/lib \ --with-openssl-dir=/home/mastag/build-mipsel/tmp/staging/mipsel-linux/lib \ --with-libevent-dir=/home/mastag/build-mipsel/tmp/staging/mipsel-linux/lib \ --disable-asciidoc --enable-static-openssl --enable-static-libevent \ --host=mipsel-linux --with-libnatpmp-dir=/home/mastag/build-mipsel/tmp/staging/mipsel-linux/lib \ --with-libminiupnpc-dir=/home/mastag/build-mipsel/tmp/staging/mipsel-linux/lib \ --enable-upnp --enable-nat-pmp --enable-bufferevents \ CPPFLAGS="-I/home/mastag/openpli/build-dm800/tmp/staging/mipsel-linux/include" This produces the src/or/Tor binary which runs great on the cluster. Only it's giving me the following messages: Jun 21 23:02:12.000 [notice] Tor 0.2.3.17-beta opening new log file. Jun 21 23:02:12.000 [warn] You are running Tor as root. You don't need to, and you probably shouldn't. Jun 21 23:02:13.000 [notice] No AES engine found; using AES_* functions. Jun 21 23:02:13.000 [notice] This OpenSSL has a good implementation of counter mode; using it. Jun 21 23:02:15.000 [notice] OpenSSL OpenSSL 1.0.1c 10 May 2012 looks like version 0.9.8m or later; I will try SSL_OP to enable renegotiation Jun 21 23:02:37.000 [notice] Reloaded microdescriptor cache. Found 4807 descriptors. Jun 21 23:02:42.000 [notice] We now have enough directory information to build circuits. Jun 21 23:02:42.000 [notice] Bootstrapped 80%: Connecting to the Tor network. Jun 21 23:02:43.000 [notice] Heartbeat: Tor's uptime is 0:00 hours, with 1 circuits open. I've sent 0 kB and received 0 kB. Jun 21 23:02:43.000 [notice] Bootstrapped 85%: Finishing handshake with first hop. Jun 21 23:02:43.000 [warn] TLS error while creating tor_tls_t object: could not load the shared library (in DSO support routines:DLFCN_LOAD:---) Jun 21 23:02:43.000 [warn] TLS error while creating tor_tls_t object: could not load the shared library (in DSO support routines:DSO_load:---) Jun 21 23:02:47.000 [notice] Bootstrapped 90%: Establishing a Tor circuit. Jun 21 23:02:53.000 [notice] Tor has successfully opened a circuit. Looks like client functionality is working. Jun 21 23:02:53.000 [notice] Bootstrapped 100%: Done. The warning about the AES engine is probably because OpenSSL has no engine for mips. However the following two lines bother me: [warn] TLS error while creating tor_tls_t object: could not load the shared library (in DSO support routines:DLFCN_LOAD:---) [warn] TLS error while creating tor_tls_t object: could not load the shared library (in DSO support routines:DSO_load:---) Any way to get rid of these? I did compile OpenSSL with "enable-tlsext" so I don't understand why it warns me about it. Thanks in advance! [View Less]

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Re: [tor-dev] Stem Proc Integration Tests
by Norman Danner 29 Jun '12

29 Jun '12

(Sorry, wasn't subscribed to tor-dev@, so these last couple of messages didn't go there...) On 6/29/12 4:09 PM, Damian Johnson wrote: >> I think the question here is that it seems like one should be able to get >> all the descriptors from the running Tor process via >> >> GETINFO desc/all-recent >> >> But there isn't any obvious stem API for this. One could work around it >> (e.g., do a get_info(), process a little, turn into a StringIO, and … [View More]

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