tor-dev July 2014

tor-dev@lists.torproject.org

79 participants
83 discussions

What are some aspects of Tor that are suffering right now due to lack of speed?
by Virgil Griffith 25 Jul '14

25 Jul '14

Hidden services quickly come to mind. Are there other candidates? I can imagine people deciding not to view certain content through Tor because of speed (e.g., pornhub). But I suspect I am missing some use cases. -V

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DEFAULT_ROUTE_LEN [was: Silly (or not so silly) question]
by grarpamp 24 Jul '14

24 Jul '14

On Wed, Jul 23, 2014 at 6:34 PM, Roger Dingledine <arma(a)mit.edu> wrote: > On Wed, Jul 23, 2014 at 11:24:47PM +0100, Noel David Torres Taño wrote: >> What would happen if a Tor node changes behaviour and uses four or five >> relay steps instead of three? At around DEFAULT_ROUTE_LEN 8 or above I get a lot of these, with EXTEND being shown in various command locations, and no connectivity to hidden services. Lower values or 4 or 5 probably work just fine but I didn't bother testing more than a couple clearnet and onion circuits since it's not yet a controller/config tunable and thus takes edit/compile/run time. So even my test of 9 > 5 > 7 > 8 take with salt. Don't know if this likely represent a bug to test more, or just timeouts... the circuits that did work setup in times not feeling much more than time/3*LEN. I'd suggest an undocumented tunable and unit test if it's worth research/statistic/function_checking purpose. relay_send_command_from_edge_(): Bug: Uh-oh. We're sending a RELAY_COMMAND_EXTEND cell, but we have run out of RELAY_EARLY cells on that circuit. Commands sent before: (unrecognized),(unrecognized),(unrecognized),(unrecognized),EXTEND,EXTEND,(unrecognized) >> Would it enhance Tor's security? > > I assume you mean a Tor client? > > https://www.torproject.org/docs/faq#ChoosePathLength > >> Is it possible to relay Tor through a Tor connection? I mean using Tor >> with its three steps to reach a Tor entry node to get three extra steps. > > Yes, it is possible. But it is currently considered a flaw, because it > can be used to work around the 'infinite path length' defenses. > http://freehaven.net/anonbib/#congestion-longpaths > https://gitweb.torproject.org/torspec.git/blob/HEAD:/proposals/110-avoid-in… > https://trac.torproject.org/projects/tor/ticket/2667 > >> Would that difficult correlation attacks? > > Defending against correlation attacks is an open research, so "maybe". > But it's not clear how it would, since an adversary who can see or > measure your first hop (on the first circuit) and also your last hop > (on the last circuit) would still be in the right place to do the attack.

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New Version of OnionMail 1.6.0.667B is Out
by Liste 24 Jul '14

24 Jul '14

* Thunderbird autoconfiguraticon. * Web Server. * User subscription webpages. * Full integrated PGP key generation and keyServer sender. * Mail Queue (onli exit/enter server). * Bash OnionMail Setup wizard. * And much more... You can activate an OnionMail server in 5 minutes! You can create a new user account in 100 seconds! The mode is easier to get a mail box is described here: http://onionmail.info/network/ >From this new version you can get a mail box via web directly. Download the new version at: http://onionmail.info/download/ User Manual: http://www.onionmail.info/manual.html What is OnionMail? http://onionmail.info/paper.html OnionMail Project http://onionmail.info

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channel_t to IP Address
by Gareth Owen 24 Jul '14

24 Jul '14

Hi all Quick question, how does one turn channel_t into an IP address, e.g. given a circuit_t how do I get the IP address of the previous and next hop (noting that they might not be in the consensus so I cant use the identity hash). I can see the information is in the connection_t struct but I don't know how to get that from the channel/circuit. Any help appreciated. Thanks Gareth -- Dr Gareth Owen Senior Lecturer School of Computing, University of Portsmouth Tel: 02392 846423 Web: ghowen.me

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Silly (or not so silly) question
by Noel David Torres Taño 23 Jul '14

23 Jul '14

Hi all What would happen if a Tor node changes behaviour and uses four or five relay steps instead of three? Would it enhance Tor's security? Is it possible to relay Tor through a Tor connection? I mean using Tor with its three steps to reach a Tor entry node to get three extra steps. Would that difficult correlation attacks? Regards Noel er Envite

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Draft proposal: Tor Consensus Transparency
by Linus Nordberg 22 Jul '14

22 Jul '14

Hi Tor devs, It's surprisingly hard to work on Tor during the Tor developer meetings! My apologies for not publishing this text until now, despite my repeated ranting about the subject the last few days. Well, here it is, in an early draft version. Thank you all who've listened patiently and given valuable feedback. I welcome more feedback from the list. Thanks in advance. --8<---------------cut here---------------start------------->8--- Filename: xxx-tor-consensus-transparency.txt Title: Tor Consensus Transparency Author: Linus Nordberg Created: 2014-06-28 Status: Draft 0. Introduction WARNING!!! EARLY DRAFT -- MISSING IMPORTANT BITS AND PIECES! This document describes how to provide and use public, append-only, untrusted logs containing Tor consensus documents, much like what Certificate Transparency [RFC6962] does for X.509 certificates. Tor relays and clients can then refuse using a consensus not present in logs of their choosing. WARNING!!! EARLY DRAFT -- MISSING IMPORTANT BITS AND PIECES! 1. Overview Using a public, append-only, untrusted log like the history tree described in [CrosbyWallach], Tor clients and relays verify that consensus documents are present in one or more logs before using them. Consensus-users, i.e. Tor clients and relays, expect to receive one or more "proof of inclusions" with new consensus documents. A proof of inclusion is a hash sum representing the tree head of a log, signed by the logs private key, and an audit path listing the nodes in the tree needed to recreate the tree head. Consensus-users are configured to use one or more logs by listing a log address and a public key for each log. This is used to verify that a given consensus document is present in a given log. Anyone can submit a properly formatted and signed consensus document to a log and get a signed proof of inclusion in return. Directory authorities should do this and include the proofs when serving consensus documents. Directory caches and consensus-users receiving a consensus not including a proof of inclusion submit the document and use the proof they receive in return. Auditing log behaviour and monitoring the contents of logs is performed in cooperation between the Tor network and external services. Directory caches act as log auditors with help from Tor clients gossiping about what they see. Directory authorities are good candidates for monitoring log content since they know what documents they have issued. Anybody can run both an auditor and a monitor though, which is an important property of the proposed system. Summary of proposed changes to Tor: - Directory authorities start submitting newly created consensuses to at least one public log. - Tor clients and relays receiving a consensus not accompanied by a proof of inclusion start submitting that to at least one public log. - Consensus-users start rejecting consensuses accompanied by an invalid proof of inclusion. - A new cell type LOG_GOSSIP is defined, for clients and relays to exchange information about tree heads seen and their validity. - Consensus-users send LOG_GOSSIP cells with seen tree heads to relays. - Relays validate tree heads received in LOG_GOSSIP cells (section 3.2.2) and send results to consensus-users in LOG_GOSSIP cells. 2. Motivation Popping five boxes or factoring five RSA keys should not be ruled out as a possible attack against a subset of the Tor network. An attacker controlling a majority of the directory authorities signing keys can, using man-in-the-middle or man-on-the-side attacks, serve consensus documents listing relays under their control. If mounted on a small subset of the network, the chance of detection is probably low. This proposal increases the cost for such an attack by raising the chances of it to be detected. The complexity of the proposed solution is motivated by the value of the decentralisation given. Anybody can run their own log and use it. Anybody can audit any existing logs and verify their correct behaviour. This empowers people outside the group of Tor directory authority operators and the people who trust them on a personal basis. 3. Design Communication with logs is done over http(s) similar to what [RFC6962] defines. This proposal does not use [[the TLS data structures]] but instead structures based on [[FIXME]]. Parameters for POSTs and all responses are encoded as name/value pairs in JSON objects [RFC4627]. Definitions: - Log id: The SHA-256 hash of the log's public key, to be treated as an opaque byte string identifying the log. 3.1 Consensus submission Logs accept consensus submissions from anyone as long as the consensus is signed by a majority of the Tor directory authorities of the Tor network that the log is logging. [[TODO: Move most of this to "specification" section?]] Consensus documents are POST:ed to well-known URL https://<log server>/tct/v1/add Input: consensus: A consensus status document as defined in [dir-spec] section 3.4.1. Output: id: The log id, base64 encoded. tree_size: The size of the tree, in entries, in decimal. timestamp: The timestamp, in decimal. sha256_root_hash: The Merkle Tree Hash of a tree including the submitted entry, in base64. tree_head_signature: A TreeHeadSignature ([RFC6962] section 3.5) for the above data. audit_path: An array of base64-encoded Merkle tree nodes proving the inclusion of the submitted entry in the tree denoted by sha256_root_hash (see [RFC6962] section 2.1.1). The output is what we call a proof of inclusion. The tree_head_signature is signed with the private key of the log. 3.2 Consensus verification 3.2.1 Log entry membership Calculate a tree head from the hash of the received consensus and the audit path in proof. Verify that it's identical to the tree head in the proof. This can easily be done by consensus-users for each received consensus. We now know that the consensus is part of a tree which the log claims to be The Tree. Whether this tree is the same tree that everybody else see is unknown at this point. 3.2.2 Append-only property of the log Ask the log for a consistency proof between the received tree head and a previously known good tree head. The known good head can be the empty tree. [[TODO add text about how to deal with received heads that are older than the last known good tree.]] Communication with logs is done over http(s) [[as described in [RFC6962] section 4 -- TODO specify protocol and encoding]]. [[description of consistency verification goes here]] Tor relays may do this for tree heads received in LOG_GOSSIP cells and communicate results in the same cells. [[TODO: Do this synchronously or asynchronously?]] Relays cache results to minimise the need for communication with log servers and calculations. We now know that the received tree is a superset of the known good tree. 3.3 Log auditing A log auditor verifies that the log presents the same view to all its clients and its append-only property, i.e. that no entries once accepted by the log are ever changed or removed. [[TODO describe the Tor networks role in auditing a bit more than what's mentioned in 3.2.2]] 3.4 Log monitoring A log monitor verifies that the contents of the log is consistent with the rules of the Tor network, notably that all entries are properly formed and signed Tor consensus documents. Note that there can be more than one valid consensus documents for a given point in time. One reason for this is that the number of signatures can differ due to consensus voting timing details. [[Are there more?]] [[TODO expand on monitoring strategies -- even if this is not part of proposed extensions to the Tor network it's good for understanding]] 3.5 Consensus-user behaviour Keep an on-disk cache of consensus documents. Mark them as being in on of three states: LOG_STATE_UNKNOWN -- don't know whether it's present in enough logs or not LOG_STATE_LOGGED -- have seen good proof(s) of inclusion LOG_STATE_LOGGED_GOOD -- confident about the tree head representing a good tree Newly arrived consensus documents start in LOG_STATE_UNKNOWN or LOG_STATE_LOGGED depending on whether they are accompanied by enough proofs or not. There are two possible state transitions: - LOG_STATE_UNKNOWN --> LOG_STATE_LOGGED: Seen enough proofs of inclusion verifying correctly according to section 3.2.1. The number of good proofs needed is a policy setting in the configuration of the consensus-user. - LOG_STATE_LOGGED --> LOG_STATE_LOGGED_GOOD: Seen enough gossiping to know that the tree head in the proof belongs to a known log. Consensuses in state LOG_STATE_UNKNOWN are not used but are instead submitted to one or more logs. This may take the consensus to LOG_STATE_LOGGED. Consensuses in state LOG_STATE_LOGGED are used despite not being fully verified with regard to logging. LOG_GOSSIP cells with the tree heads from received proofs are being sent to relays for further verified. Clients send to all relays that they have a circuit to to. Relays send to three random relays that they have a circuit to. 3.6 Relay behaviour when acting as an auditor TODO 3.7 Notable differences from Certificate Transparency - The data logged is "strictly time-stamped", i.e. ordered. - Much shorter lifetime of logged data -- a day rather than a year. Is the effects of this difference of importance only for "one-shot attacks"? - Directory authorities have consensus about what they're signing -- there are no "web sites knowing better". - Submitters are not in the same hurry as CA:s and can wait minutes rather than seconds for a proof of inclusion. 4. Security implications TODO 5. Specification TODO ? Compatibility ? Implementation ? Performance and scalability notes A. Open issues - handle all consensus flavours (i.e. microdescriptor consensuses) - don't use "consensus verification" since that's misleading - maybe add hash function agility, i.e. don't fixate SHA-256 (but see CT discussion about why not and TODO summarize it here) - add a blurb about the values of publishing logs as Tor hidden services - should relays gossip amongst each others too? - discuss compromise of log keys - add 'version' and 'extensions' fields to the submission response? - maybe log votes as well B. Acknowledgements This proposal leans heavily on [RFC6962]. Some definitions are copied verbatim from that document. Valuable feedback has been received from Ben Laurie and Karsten Loesing. C. References [CrosbyWallach] http://static.usenix.org/event/sec09/tech/full_papers/crosby.pdf [dir-spec] https://gitweb.torproject.org/torspec.git/blob/HEAD:/dir-spec.txt [RFC4627] https://tools.ietf.org/html/rfc4627 [RFC6962] https://tools.ietf.org/html/rfc6962 --8<---------------cut here---------------end--------------->8---

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Re: [tor-dev] Proposal for improving social incentives for relay operators
by George Kadianakis 22 Jul '14

22 Jul '14

Am 2014-06-10 02:26, schrieb Virgil Griffith: > For a while I've been seeking to grow the Tor network in both size and > goodput. Towards this end, I've explored various avenues such as > increasing user-awareness via tor2web. More recently, I've been exploring > financial incentives like TorCoin. > > Not wanting to strictly limit ourselves to financial incentives, I began > reading the literature on incentivizing volunteers. The most relevant > papers I found are: > > * http://www-2.rotman.utoronto.ca/facbios/file/LMS2_ManSci-Paper-Final.pdf > * http://pareto.uab.es/~prey/gneezy_254.pdf > * https://dl.dropboxusercontent.com/u/3308162/Slonim%202013.pdf > > The most relevant of these papers (Lacetera 2013) cites the major > motivations for volunteer labor are: "pure altruism, warm glow, self-image, > and reputation". Upon reading this I realized TorCoin's technical > interestingness had blinded me to much easier to leverage motivations of > "warm glow" and "reputation". > > I propose the following system for harnessing "warm glow" and "reputation" > for Tor relay operators. I am willing to fund this in its entirety. > > I propose establishing a subdomain on torproject.org giving each Tor relay > operator (hereafter affectionately called "Torati") his/her own page using > the information her machines provide to the Tor Directory Consensus. The > fields to show on her "Torati profile page" would be things like: > ContactInfo, PGP fingerprint, list of server nicknames, date the Directory > Authorities first saw her contact info, etc. You can also imagine a > receiving special "special recognition stars" for operating an exit or Here are some ideas on various achievements/badges that could be awarded to relay operators (in no particular order): - You earned a flag (fast/hsdir/stable/named/exit)! - Your uptime is over 9000 (seconds/days/months)! - You are part of a family! - You have the contact field set! - With PGP! - With a BTC address! - You are part of an organization (torservers/etc.)! - You are in an exotic location! (not many relays there) - You have IPv6 enabled! - You are running an experimental Tor version! - You are a bridge with many clients from China! - You are an obfsbridge! You can imagine more special achievements, like: - You were around during event X! (arab spring, etc.) - You were the top guard during event X! - You were the first big relay ever in Lithuania! - You were in the top 10 exits. - You survived an hour of anarchy! (awarded when the authorities fail to establish a consensus for an hour) etc. You can also imagine recurring (monthly) achievements, and more one-time achievements that tend to really motivate people in games. Also, some kind of point system and levels might be fun. To be honest, I don't know if such a thing would motivate people to start running relays, but it might motivate people whole already run relays to run even better ones (or try to hack the system just to collect achievements).

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help with minimal Tor build for Shadow
by Rob Jansen 22 Jul '14

22 Jul '14

Hi, Shadow uses CMake and a custom build process to build the Tor source files into a shadow-plugin (using Clang/LLVM and a custom pass). However, because my CMake build file is not smart enough to know how to turn orconfig.h.in into orconfig.h, I still have to run Tor through autotools first (and then build again with Clang). I’m hoping to eliminate at least parts of the Tor configure/make build process. Shadow for sure needs orconfig.h to exist, and I presume ./autogen.sh and ./configure is the best way to generate that. Does anyone know of a faster approach? (I’d like to avoid adding the rules to my CMakeLists.txt file, as it will be hard to keep up with Tor’s upstream changes to its Makefile.in.) However, still missing after the configure is at least or_sha1.i, and possibly other files. Presumably these are generated when running make (after configure). My custom Clang build fails without them. Is there a special make target in Tor that generates these “helper” files without building the entire Tor binary? If not, should/can there be? All the best, Rob

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Typos in 224-rend-spec-ng.txt
by Tim 21 Jul '14

21 Jul '14

Hi All, I've found a few typos in the first few sections of 224-rend-spec-ng.txt at https://gitweb.torproject.org/torspec.git/blob/HEAD:/proposals/224-rend-spe… I tried finding an existing bug or wiki entry on trac to log these against, but I couldn't find anything relevant with: https://trac.torproject.org/projects/tor/search?q=proposal+264 The typos are: (I read from the start to Section 2.2.3) Line 392, S 1.3, [IMD:AC]: 'knowledge od the contents' (knowledge *of* the contents) Line 618, S 2.2.1, [TIME-PERIODS]: 'a single set of hidden service directory' (*directories*) S 2.2.3. Where to publish a service descriptor: Line 702 : 'hsdir_n_replicas' should be 'n_replicas' to be consistent with lines 710-711: 'where n_replicas is determined by the consensus parameter "hsdir_n_replicas"' Line 733: "An HSDir should rejects a descriptor" (should *reject*) Hope this helps. Tim

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Re: [tor-dev] [tor-relays] Hidden service policies
by grarpamp 21 Jul '14

21 Jul '14

On Sun, Jul 20, 2014 at 9:57 PM, Thomas White <thomaswhite(a)riseup.net> wrote: > Mike Hearn, > Simple. If you start filtering anything at all, regardless of what it > is ... then I will > block any connection of your relays to mine > ... > Freedom isn't free unless it is > totally free and a selective reading policy through Tor is not just a > bad idea as stated below, I find it outright insulting to me and > everyone else who cares about the free and open internet. The fact > somebody has the audacity to come to a project like Tor and propose > blacklisting mechanisms is jaw-dropping. > ... > As I recall, you are also the person who raised the idea of coin > tinting or a similar concept in the bitcoin community to identify > "suspect" coins and that backfired spectacularly on you. Yes, that is the person. Though the term is known as 'taint'. One of many discussions from that suggestion is here: https://bitcointalk.org/index.php?topic=333824.0 > so while you are reading this, let me know if you run any relays so I > can avoid them. router riker 207.12.89.16 9001 0 0 fingerprint 8657 6CF6 AA84 496F 62C0 5AFE 9F26 8962 A5F0 B2BD contact Mike Hearn <mike(a)plan99.net> accept *:8333 reject *:* Normally I would thank exits for passing BTC traffic, but now I'm unsure of this one (and a few others), especially given that's the only exit policy of the above node. To identify anon (Tor) coins for marking and tracking?

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tor-dev July 2014