- tor-dev - lists.torproject.org

Re: [tor-dev] Proposal 274: A Name System API for Tor Onion Services
by Hugo Maxwell Connery 08 Oct '16

08 Oct '16

Hi, I think that this work is extremely important, and I applaud the authors and contributors for their work. It seems that it will also be complicated, semantically. What lies where, and which thing does what? The example recently about what is sent in the Host header is a good example of this challenge. I have below, in situ, made a few suggested corrections, and offered my suggestions on a few topics. I am not precious about my opinions and am happy to have them shot down by people with a deeper understanding of the challenge at hand. My overriding suggestion is to keep this as simple as possible in its initial iteration. It will almost certainly get more complex down the line, and working out what the core principles are early on will help guard against "feature creep". Well done, and good luck, Hugo NB: all comments prefixed with '> ' --- Filename: 274-naming-layer-api.txt Title: A Name System API for Tor Onion Services Author: George Kadianakis, Yawning Angel, David Goulet Created: 04-Oct-2016 Status: Draft Table Of Contents: 1. Introduction 1.1. Motivation 1.2. Design overview and rationale 2. System Specification 2.1. System overview [SYSTEMOVERVIEW] 2.2. System Illustration 2.3. System configuration [TORRC] 2.3.1. Tor name resolution logic 2.4. Name system initialization [INITPROTOCOL] 2.5. Name resolution using NS API 2.5.1. Message format 2.5.2. RESOLVED status codes 2.5.3. Further name resolution behavior 2.6. Cancelling a name resolution request 2.7. Launching name plugins [INITENVVARS] 2.8. Name plugin workflow [NSBEHAVIOR] 2.8.1. Name plugin shutdown [NSSHUTDOWN] 2.9. Further details of stdin/stdout communication 2.9.1. Message Format 3. Discussion 3.1. Using second-level domains instead of tld 3.2. Name plugins handling all tlds '*' 3.3. Deployment strategy 3.4. Miscellaneous discussion topics 4. Acknowledgements A.1: Example communication Tor <-> name plugin [PROTOEXAMPLE] A.2: Example plugins [PLUGINEXAMPLES] 1. Introduction This proposal specifies a modular API for integrating name systems with Tor. 1.1. Motivation Tor onion service addresses are decentralized and self-authenticated but they are not human-memorable (e.g. 3g2upl4pq6kufc4m.onion). This is a source of poor usability, since Internet users are familiar with the convenient naming of DNS and are not used to addresses being random text. In particular, onion addresses are currently composed of 16 random base32 characters, and they look like this: 3g2upl4pq6kufc4m.onion vwakviie2ienjx7t.onion idnxcnkne4qt76tg.onion vwakviie2ienjx6t.onion When Proposal 224 get deployed, onion addresses will become even bigger: 53 base32 characters. That's: llamanymityx4fi3l6x2gyzmtmgxjyqyorj9qsb5r543izcwymle.onion lfels7g3rbceenuuqmpsz45z3lswakqf56n5i3bvqhc22d5rrsza.onion odmmeotgcfx65l5hn6ejkaruvai222vs7o7tmtllszqk5xbysola.onion qw3yvgovok3dsarhqephpu2pkiwzjdk2fgdfwwf3tb3vgzxr5kba.onion Over the years Tor users have come up with various ad-hoc ways of handling onion addresses. For example people memorize them, or use third-party centralized directories, or just google them everytime. > Additionally, onion service providers have sometimes placed effort > in creating more readable and memorable names, for example: > > facebookcorewwwi.onion We believe that the UX problem of non-human-memorable problems is not actually solved with the above ad-hoc solutions and remains a critical usability barrier that prevents onion services from being used by a wider audience. 1.2. Design overview and rationale During the past years there has been lots of research on secure naming and various such systems have been proposed (e.g. GNS, Namecoin, etc.). Turns out securely naming things is a very hard research problem, and hence > It turns out that .. none of the proposed systems is a clear winner: all of them carry various trade-offs. Furthermore, none of the proposed systems has seen widespread use so far, which makes it even harder to pick a single project. Given the plenitude of options, one approach to decide which system > Given the plentitude ... is best is to make various decent name systems available and let the Tor community and the sands of time pick the winner. Also, it might be that there is no single winner, and perhaps different specialized name system should be used in different situations. We believe that by getting secure name systems actually get utilized by real users, the whole field will mature and existing systems will get battle-hardened. Hence, the contribution of this proposal is a modular Name System API (NSA) that allows developers to integrate their own name systems in Tor. The interface design is name-system-agnostic, and it's heavily based on the pluggable transports API (proposal 180). It should be flexible enough to accommodate all sorts of name systems (see [PLUGINEXAMPLES]). 2. System Specification A developer that wants to integrate a name system with Tor needs to first write a wrapper that understands the Tor Name System API (NS API). Using the Name System API, Tor asks the name system to perform name queries, and receives the query results. The NS API works using environment variables and stdin/stdout communication. It aims to be portable and easy to implement. 2.1. System overview [SYSTEMOVERVIEW] Here is an overview of the Tor name system: Alice, a Tor user, can activate various name systems by editing her torrc file and specifying which tld each name system is responsible for. For this section, let's consider a simple fictional name system, unicorn, which magically maps domains with the .corn tld to the correct onion address. Here it is: OnionNamePlugin 0 .corn /usr/local/bin/unicorn After Alice enables the unicorn plugin, she attempts connecting to elephantforum.corn. Tor will intercept the SOCKS request, and use the executable at /usr/local/bin/unicorn to query the unicorn name system for elephantforum.corn. Tor communicates with the unicorn plugin using the Tor NS API through which name queries and their results can be transported using stdin/stdout. If elephantforum.corn corresponds to an onion address in the unicorn name system, unicorn should return the onion address to Tor using the Tor NS API. Tor must then internally rewrite the elephantforum.corn address to the actual onion address, and initiate a connection to it. 2.2. System Illustration Here is a diagram illustrating how the Tor Name System API works. The name system used in this example is GNS, but there is nothing GNS-specific here and GNS could be swapped for any other name system (like hosts files, or Namecoin). The example below illustrates how a user who types debian.zkey in their Tor browser gets redirected to sejnfjrq6szgca7v.onion after Tor consults the GNS network. Please revisit this illustration after reading the rest of the proposal. | $~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~$ | 1. $ 4. GNS magic!! $ | User: SOCKS CONNECT to $ debian.zkey -> sejnfjrq6szgca7v.onion$ | http://debian.zkey/ $~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~$~~~~~~~$ | $ +-----|-----------------------------------------+ $ |+----v-----+ 2. +---------+| 3. $ ||Tor | debian.zkey |Tor || debian.zkey +-$-------+ ||Networking------------------------->Naming -------------------------> | ||Submodule | |Submodule|| Tor Name System API | GNS | || <------------------------- <------------------------- wrapper| || | 6. | ||5. | | |+----|-----+ sejnfjrq6szgca7v.onion +---------+|sejnfjrq6szgca7v.onion +---------+ +-----|-----------------------------------------+ | 7. | Tor: Connect to | http://sejnfjrq6szgca7v.onion/ v > Points for the phrase "GNS magic!!" (A little humor goes a long way in technical > specification documents) 2.3. System configuration [TORRC] As demonstrated in [SYSTEMOVERVIEW], a Tor user who wants to use a name system has to edit their configuration file appropriately. Here is the torrc line format: OnionNamePlugin <priority> <tld> <path> where <priority> is a positive integer denoting the priority with which this > where <priority> is a non-negative integer ... name plugin should be consulted. <tld> is a string which restricts the scope of this plugin to a particular tld. Finally, <path> is a filesystem path to an executable that speaks the Tor Name System API and can act as an intermediary between Tor and the name system. For example here is a snippet from a torrc file: OnionNamePlugin 0 .hosts /usr/local/bin/local-hosts-file OnionNamePlugin 1 .zkey /usr/local/bin/gns-tor-wrapper OnionNamePlugin 2 .bit /usr/local/bin/namecoin-tor-wrapper OnionNamePlugin 3 .scallion /usr/local/bin/community-hosts-file 2.3.1. Tor name resolution logic When Tor receives a SOCKS request to an address that has a name plugin assigned to it, it needs to perform a query for that address using that name plugin. If there are multiple name plugins that correspond to the requested address, Tor queries all relevant plugins sorted by their priority value, until one of them returns a successful result. If two plugins have the same priority value, Tor MUST abort. If all plugins fail to successfuly perform the name resolution, Tor SHOULD default to using the exit node for name resolution. XXX or not? because of leaks? > I suggest that the decision of whether to fallback to "DNS at exit node" may > be a domain specific choice. i.e Yes for .scallion and .hosts, but No for > .zkey and .bit. Thus, perhaps an additional, mandatory configuration for each > OnionNamePlugin configuration line of Yes|No to indicate if fallback should > occur. > > Thus: > OnionNamePlugin 0 .hosts Yes /usr/local/bin/local-hosts-file yes > OnionNamePlugin 1 .zkey No /usr/local/bin/gns-tor-wrapper no > OnionNamePlugin 2 .bit No /usr/local/bin/namecoin-tor-wrapper > OnionNamePlugin 3 .scallion Yes /usr/local/bin/community-hosts-file > > Another way to handle this is for the NS API to provide "please use DNS at exit > node" as a valid response type. E.g Tor asks the Banana Name API to resolve > orange.banana and the Banana Name API responses with an NS API status code which > means "please use DNS at exit node". > > This second idea may be the best, as each Name system will have its own idea > as to whether this is a good idea or not and thus Tor does not need to decide > and no configuration is required. > > Additionally this makes writing the "No Op" name api as trivial as responding > successfully to INIT and then just always returning the status code for "please > use DNS at exit node". > > Furthermore, it allows a name system to be able to choose this behaviour based > on context. i.e the name system knows that the orange.banana domain/service > is happy to have its name resolved with normal DNS but also knows that > pear.banana does not wish to have normal DNS ever used to resolve it. > > This distinction is something that Tor will never be able to make by itself. 2.4. Name system initialization [INITPROTOCOL] When Tor finds OnionNamePlugin lines in torrc, it launches and initializes their respective executables. When launching name plugins, Tor sets various environment variables to pass data to the name plugin (e.g. NS API version, state directory, etc.). More information on the environment variables at [INITENVVARS]. After a name plugin initializes and parses all needed environment variables, it communicates with Tor using its stdin/stdout. The first line that a name plugin sends to stdout signifies that it's ready to receive name queries. This line looks like this: INIT <VERSION> <STATUS_CODE> [<STATUS_MSG>] where VERSION is the Tor NS API protocol version that the plugin supports, > where VERSION is a comma-separated list of the Tor NS API protocol versions ... STATUS_CODE is an integer status code, and STATUS_MSG is an optional string error message. STATUS_CODE value 0 is reserved for "success", and all other integers are error codes. See [PROTOEXAMPLE] for an example of this protocol. 2.5. Name resolution using NS API Here is how actual name resolution requests are performed in NS API. 2.5.1. Message format When Tor receives a SOCKS request to an address with a tld that has a name plugin assigned to it, Tor performs an NS API name query for that address. Tor does this by printing lines on the name plugin stdout as follows: RESOLVE <QUERY_ID> <NAME_STRING> where QUERY_ID is a unique integer corresponding to this query, and NAME_STRING is the name to be queried. When the name plugin completes the name resolution, it prints the following line in its stdout: RESOLVED <QUERY_ID> <STATUS_CODE> <RESULT> where QUERY_ID is the corresponding query ID and STATUS_CODE is an integer status code. RESULT is the resolution result (an onion address) or an error message if the resolution was not succesful. See [PROTOEXAMPLE] for an example of this protocol. XXX Should <RESULT> be optional in the case of failure? > Yes. In the case of failure the name service will almost certainly not be > able to provide a valid onion address. Thus, it cannot provide this field. 2.5.2. RESOLVED status codes Name plugins can deliver the following status codes: 0 -- The name resolution was successful. 1 -- Name resolution generic failure. 2 -- Name tld not recognized. 3 -- Name not registered. 4 -- Name resolution timeout exceeded. XXX add more status codes here as needed > As mentioned above, I suggest that one of these RESOLVED status codes is > > <some number> -- Name use DNS at the exit node > > I suggest that the number is 1. 2.5.3. Further name resolution behavior Tor and name plugins MAY cache name resolution results in memory as needed. Caching results on disk should be avoided. > ... Caching results on disk SHOULD be avoided. > perhaps even MUST be avoided. Tor SHOULD abort (or cancel) an ongoing name resolution request, if it takes more than NAME_RESOLUTION_TIMEOUT seconds. XXX NAME_RESOLUTION_TIMEOUT = ??? > 4 seconds ? Tor MUST validate that the resolution result is a valid .onion name. XXX should we also accept IPs and regular domain results??? > A very good question. I suggest that the answer is No for both. > The NS API is designed to allow people to map various domain systems > into onion addresses, and thus, only onion addresses should be accepted. > > What is happening here is similar to the getent(1) and /etc/nsswitch.conf > We dont want getent passwd foo to return data about groups, but only those > about user accounts. XXX perhaps we should make sure that results are not names that need additional name resolution to avoid endless loops. e.g. imagine some sort of loop like this: debian.zkey -> debian-bla.zkey -> debian.zkey -> etc. > Yes, as expressed above. 2.6. Cancelling a name resolution request Tor might need to cancel an ongoing name resolution request (e.g. because a timeout passed, or the client is not interested in that address anymore). In this case, Tor sends the following line to the plugin stdout as follows: CANCEL <QUERY_ID> to which the name plugin, after performing the cancellation, SHOULD answer with: CANCELED <QUERY_ID> 2.7. Launching name plugins [INITENVVARS] As described in [INITPROTOCOL], when Tor launches a name plugin, it sets certain environment variables. At a minimum, it sets (in addition to the normal environment variables inherited from Tor): "TOR_NS_STATE_LOCATION" -- A filesystem directory path where the plugin should store state if it wants to. This directory is not required to exist, but the plugin SHOULD be able to create it if it doesn't. The plugin MUST NOT store state elsewhere. Example: TOR_NS_STATE_LOCATION=/var/lib/tor/ns_state/ > Where does Tor get this information? torrc I suppose. Thus, you need to > define the namespaces in torrc for setting these things. "TOR_NS_PROTO_VERSION" -- To tell the plugin which versions of this configuration protocol Tor supports. Future versions will give a comma-separated list. Plugins MUST accept comma-separated lists containing any version that they recognize, and MUST work correctly even if some of the versions they don't recognize are non-numeric. Valid version characters are non-space, non-comma printing ASCII characters. Example: TOR_NS_PROTO_VERSION=1,1a,2,4B "TOR_NS_PLUGIN_OPTIONS" -- Specifies configuration options for this name plugin as a semicolon-separated list of k=v strings with options that are to be passed to the plugin. Colons, semicolons, equal signs and backslashes MUST be escaped with a backslash. If there are no arguments that need to be passed to any of the plugins, "TOR_NS_PLUGIN_OPTIONS" MAY be omitted. For example consider the following options for the "banana" name plugin: TOR_NS_PLUGIN_OPTIONS=timeout=5;url=https://bananacake.com Will pass to banana the parameters 'timeout=5' and 'url=https://bananacake.com'. XXX Do we like this option-passing interface? Do we have any lessons from our PT experiences? XXX Add ControlPort/SocksPort environment variables. > Yes, this is almost certainly required. A name service may wish to use Tor's > network services to perform communication with its external name services. > OnioNS is a good example of this. It uses other onion services to do name services :) See [PROTOEXAMPLE] for an example of this environment 2.8. Name plugin workflow [NSBEHAVIOR] Name plugins follow the following workflow: 1) Tor sets the required environment values and launches the name plugin as a sub-process (fork()/exec()). See [INITENVVARS]. 2) The name plugin checks its environment, and determines the supported NS API versions using the env variable TOR_NS_PROTO_VERSION. 2.1) If there are no compatible versions, the name plugin writes an INIT message with a failure status code as in [INITPROTOCOL], and then shuts down. 3) The name plugin parses and handles the rest of the environment values. 3.1) If the environment variables are malformed, or otherwise invalid, the name plugin writes an INIT message with a failure status code as in [INITPROTOCOL], and then shuts down. 4) After the name plugin completely initializes, it sends a successful INIT message to stdout as in [INITPROTOCOL]. Then it continues monitoring its stdin for incoming RESOLVE messages. 6) When the name plugin receives a RESOLVE message, it performs the name resolution and replies with the appropriate RESOLVED message. 7) Upon being signaled to terminate by the parent process [NSSHUTDOWN], the name plugin gracefully shuts down. 2.8.1. Name plugin shutdown [NSSHUTDOWN] To ensure clean shutdown of all name plugins when Tor shuts down, the following rules apply for name plugins: Name plugins MUST handle OS specific mechanisms to gracefully terminate (e.g. SIGTERM). > I think that it would be valuable to be a little more specific here. Name plugins SHOULD monitor their stdin and exit gracefully when it is closed. > A very important point. This may obviate the need for "being more explicit" > as called for above. 2.9. Further details of stdin/stdout communication 2.9.1. Message Format Tor communicates with its name plugins by writing NL-terminated lines to stdout. The line metaformat is <Line> ::= <Keyword> <OptArgs> <NL> <Keyword> ::= <KeywordChar> | <Keyword> <KeywordChar> <KeyWordChar> ::= <any US-ASCII alphanumeric, dash, and underscore> <OptArgs> ::= <Args>* <Args> ::= <SP> <ArgChar> | <Args> <ArgChar> <ArgChar> ::= <any US-ASCII character but NUL or NL> <SP> ::= <US-ASCII whitespace symbol (32)> <NL> ::= <US-ASCII newline (line feed) character (10)> Tor MUST ignore lines with keywords that it doesn't recognize. 3. Discussion 3.1. Using second-level domains instead of tld People have suggested that users should try to connect to reddit.zkey.onion instead of reddit.zkey. That is, we should always preserve .onion as the tld, and only utilize second-level domains for naming. The argument for this is that this way users cannot accidentally leak addresses to DNS, as the .onion domain is reserved by RFC 7686. The counter-argument here is that this might be confusing to users since they are not used to the second-level domain being special (e.g. co.uk). Also, what happens when someone registers a 16-character name, that matches the length of a vanilla onion address? We should consider the concerns here and take the right decision. > As mentioned several times above, my opinion is that the NS API is > a mechanism for mapping other name systems into onion addresses. > If people want to do other "more interesting things" then they are > welcome to do that with their own overlay networks (e.g p2p, gnunet etc.). > > i.e what NS API is doing is allowing them to utilise their name system > through Tor if they have set up an onion service within Tor. If they have > just set up their service within their overlay network, then they can just > use its own infrastructure to assist people in reaching that service. > > I am rather confident that other people will have other opinions, > and I am happy to be "wrong" about this. 3.2. Name plugins handling all tlds '*' In [TORRC], we assigned a single tld to each name plugin. Should we also accept catch-all tlds using '*'? I'm afraid that this way a name system could try to resolve even normal domains like reddit.com . Perhaps we trust the name plugin itself, but maybe the name system network could exploit this? Also, the catch-all tld will probably cause some engineering complications in this proposal (as it did for PTs). > The only existing name system that can "reliably" handle * is DNS. > Thus, this is the 'no configuration required default' (DNS-at-exit-node). > However, it may be some peoples desire to override this 'no configuration > default'. So, perhaps allow it to be specificed in torrc. 3.3. Deployment strategy [snip ; no further comment by me].

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0.2.9 freeze dates, and fun bugs to work on, and important code to review
by Nick Mathewson 07 Oct '16

07 Oct '16

Hello, all! Here is an incomplete list of takeaways from network-team meeting last week, plus some more scheduling things, and other fun stuff for new (and experienced) Tor developers! * 0.2.9 is now frozen for big/risky changes. I'll put out the final alpha around 14 or 17 Oct, and fork 0.3.0 then too. * I'll continue to accept small, safe changes in 0.2.9 through the final alpha. Maybe a couple of days after. After that, I only plan to take fixes for critical bugs, regressions, and security issues. * Here are the open tickets in the 0.2.9 milestone [1]. Note that some of them have no owner! Many of them would be pretty easy for somebody to fix, if you want something to work on over the next few days. On the other hand, almost none of them seem must-fix-before-0.2.9-or-the-sky-falls to me. So if nobody works on a patch for them over the next week or so, they're probably going to have to wait for 0.3.0. * Here is the latest "review group" [2] -- a list of tickets where I'm not planning to review new big stuff outside of this group until everything in this group. During the 0.2.9 development period, using this method has gotten us to the point where we are reaching the final weeks of development without a huge backlog of unreviewed code. Writing reviews for this code can be a fun introduction to how Tor works! [1] Open 0.2.9 tickets: https://trac.torproject.org/projects/tor/query?status=!closed&milestone=Tor… [2] review-group-10: https://trac.torproject.org/projects/tor/query?status=!closed&keywords=~rev… all best wishes, -- Nick

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CollecTor Release 1.0.2
by iwakeh 07 Oct '16

07 Oct '16

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Hi there! CollecTor continues with a smaller release: https://dist.torproject.org/collector/1.0.2/ This release makes features available that have been running on the main CollecTor [4] instance for a while now. The three most significant changes for release 1.0.2: * CollecTor provides Bifroest's descriptor data [1]. * A shutdown hook gives the running threads time to complete properly instead of simply terminating them [2]. * TCP ports are now replaced with hashes in @type bridge-network-status 1.1 and @type bridge-server-descriptor 1.2 descriptors [3]. and some more listed in CHANGELOG.md of the tar-ball. Cheers, iwakeh [0] https://dist.torproject.org/collector/1.0.2/ [1] https://trac.torproject.org/projects/tor/ticket/20037 [2] https://trac.torproject.org/projects/tor/ticket/19016 [3] https://trac.torproject.org/projects/tor/ticket/19317 [4] https://collector.torproject.org -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iF4EAREIAAYFAlf3ukkACgkQsANAxTOj/abFvwD/ap0UWbyMVUm/gL7zZarslLuM ocTxr7Xr3VUjznxLPHsA/0it/ia7Ym1RvgB/bxKuefxcGB9n20dC4tVCAlJFwDAJ =QgO8 -----END PGP SIGNATURE-----

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txtorcon 0.17.0
by meejah 04 Oct '16

04 Oct '16

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I'm pleased to announce txtorcon 0.17.0, largely to fix a bug with Unix-socket control-ports: * issue 187: fix unix-socket control endpoints * sometimes mapping streams to hostnames wasn't working properly * backwards-compatibility API for `socks_hostname` was incorrectly named You can download the release from PyPI or GitHub (or of course "pip install txtorcon"): https://pypi.python.org/pypi/txtorcon/0.17.0 https://github.com/meejah/txtorcon/releases/tag/v0.17.0 Releases are also available from the hidden service: http://timaq4ygg2iegci7.onion/txtorcon-0.17.0.tar.gz http://timaq4ygg2iegci7.onion/txtorcon-0.17.0.tar.gz.asc You can verify the sha256sum of both by running the following 4 lines in a shell wherever you have the files downloaded: cat <<EOF | sha256sum --check 5e321387ab56f22d184b18d91a60c30dd1f72575d9e32ff3614ef911bce49daa txtorcon-0.17.0.tar.gz e1da13cc43328e040335d091e2ef15717a2b836b48fbede31fc6a7e332b699b4 txtorcon-0.17.0-py2-none-any.whl EOF thanks, meejah -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJX9B8gAAoJEMJgKAMSgGmnCLoH/jZNzTG4QRRKk54XkFCbSmBh Qg0YAmWVa4iFMkjidawyfZ8Cocje+yROMiuvH2VWNCcI809q96TB06caNJS0w5c3 I10i9N9xY2S13/yVzW/izW3HMPR+Sdi0Hod9UGTQ0F2Vpcs+g8bpPyKvMK+mPm+L P0QwyejOAO/FzTndA73T5o2bVKdR3NkK1EfY0FRTjQsD71UZlVJa4AK828v1EMi3 0oNXDny+H9xzJu/i03zFX3zSL1jb69KCxkLyUBIuj5Vg+3by8FwbBa1G3Ehcs70C RV6ew6WLa0Ty7fnUBy18Z3gFx9+4Ew/Eq/t7weVgRiW0VCAHwgOKx0D4wqSMeH8= =nyB6 -----END PGP SIGNATURE-----

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Re: [tor-dev] Joining Tor Project's software infrastructure
by George Kadianakis 04 Oct '16

04 Oct '16

Paul Syverson <paul.syverson(a)nrl.navy.mil> writes: > [ text/plain ] > On Tue, Oct 04, 2016 at 12:54:55PM -0700, George Kadianakis wrote: >> >> BTW, monitor this list, there will soon be a proposal specifying a Tor >> API for naming systems like OnioNS, similar to the one we have for >> pluggable transports. >> > > There will? Was this discussed at tordev? How did I miss this? Who's > working on it? Is there a draft anywhere? > > (Feel free to respond to tor-dev. I just didn't want to spam the list > if good general answers to these were not quite ready.) > Hey Paul :) It was discussed on Sunday, the last day of the hackfest, so that's why you missed it :( Here are some spoilers: https://people.torproject.org/~asn/hs_notes/name_transport_plugin.jpg I hope to work on the proposal ASAP. [CCing tor-dev just for completeness]

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uProxy adds Tor support
by David Fifield 30 Sep '16

30 Sep '16

https://blog.uproxy.org/2016/09/uproxy-adds-tor-support.html This blog post says that uProxy gained support for proxying others' traffic through Tor. uProxy client → censor → uProxy server → Tor → destination In the classic uProxy deployment scenario, the client and server are people who know each other. (I say "classic" because there are other deployment modalities now.) They each run a browser extension. The client encapsulates its web traffic and sends it to the server over WebRTC. The server then issues the web requests and sends the responses back over the WebRTC channel. A potential problem is that the uProxy server's own web browsing gets mixed up with that of the client. The client could, for example, get the server in trouble by accessing sketchy web sites. That's what the Tor integration is meant to solve.

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Thesis using QUIC in Tor
by Ali Clark 30 Sep '16

30 Sep '16

Hi all, For my master's thesis this summer I looked into the performance impact from using QUIC instead of TCP/TLS as the relay transport. Results from the experiments look quite promising. For more details and the thesis, please see my blog post: https://www.benthamsgaze.org/2016/09/29/quux-a-quic-un-multiplexing-of-the-… I'm happy to respond to questions either here or in comments on the blog post. Ali

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Constraining Ephemeral Service Creation in Tor
by bancfc＠openmailbox.org 29 Sep '16

29 Sep '16

Hello, We are working on supporting ephemeral onion services in Whonix and one of the concerns brought up is how an attacker can potentially exhaust resources like RAM. CPU, entropy... on the Gateway (or system in the case of TAILS) by requesting an arbitrary number of services and ports to be created. In our opinion, options in core Tor for setting a maximum number of services and ports per service seems the right way to go about it. Also rate limiting the requests (like you do with NEWNYM) would be a sensible thing to do. What are your opinions about this?

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Reducing initial onion descriptor upload delay (down to 0s?)
by Ivan Markin 29 Sep '16

29 Sep '16

Hi tor-dev@! Moving the discussion on the future of rendinitialpostdelay from ticket #20082 [1] here. Transcribing the issue: > At the moment descriptor is getting posted at > MIN_REND_INITIAL_POST_DELAY (30) seconds after onion service > initialization. For the use case of real-time one-time services > (like OnionShare, etc) one has to wait for 30 seconds until this > onion service can be reached. Besides, if a client tries to reach > the service before its descriptor is ever published, tor client gets > stuck preventing user from reaching this service after descriptor is > published. Like this: Could not pick one of the responsible hidden > service directories to fetch descriptors, because we already tried > them all unsuccessfully. > It has jumped to 30s from 5s due to "load on authorities". > 11d89141ac0ae0ff371e8da79abe218474e7365c: > > + o Minor bugfixes (hidden services): + - Upload hidden service > descriptors slightly less often, to reduce + load on > authorities. > > "Load on authorities" is not the point anymore because we don't use > V0 since 0.2.2.1-alpha. Thus I think it's safe to drop it back to at > least 5s (3s?) for all services. Or even remove it at all? The questions are: * Can we drop this delay? Why? * Can we set it back to 5s thus avoiding issues that can arise after removing the delay? * Should we do something now or postpone it to prop224? [1] https://trac.torproject.org/projects/tor/ticket/20082 -- Ivan Markin

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prop224: Ditching key blinding for shorter onion addresses
by George Kadianakis 29 Sep '16

29 Sep '16

Hello people, this is an experimental mail meant to address legitimate usability concerns with the size of onion addresses after proposal 224 gets implemented. It's meant for discussion and it's far from a full blown proposal. Anyway, after prop224 gets implemented, we will go from 16-character onion addresses to 52-character onion addresses. See here for more details: https://gitweb.torproject.org/torspec.git/tree/proposals/224-rend-spec-ng.t… This happens because we want the onion address to be a real public key, and not the truncated hash of a public key as it is now. We want that so that we can do fun cryptography with that public key. Specifically, we want to do key blinding as specified here: https://gitweb.torproject.org/torspec.git/tree/proposals/224-rend-spec-ng.t… As I understand it the key blinding scheme is trying to achieve the following properties: a) Every HS has a permanent identity onion address b) Clients use an ephemeral address to fetch descriptors from HSDir c) Knowing the ephemeral address never reveals the permanent onion address c) Descriptors are encrypted and can only be read by clients that know the identity onion key d) Descriptors are signed and verifiable by clients who know the identity onion key e) Descriptors are also verifiable in a weaker manner by HSDirs who know the ephemeral address In this email I'm going to sketch a scheme that has all above properties except from (e). The suggested scheme is basically the current HSDir protocol, but with clients using ephemeral addresses for fetching HS descriptors. Also, we truncate onion address hashes to something larger than 80bits. Here is a sketch of the scheme: ------ Hidden service Alice has a long-term public identity key: A Hidden service Alice has a long-term private identity key: a The onion address of Alice, as in the current scheme, is a truncated H(A). So let's say: onion_address = H(A) truncated to 128 bits. The full public key A is contained in Alice's descriptor as it's currently the case. When Alice wants to publish a descriptor she computes an ephemeral address based on the current time period 't': ephemeral_address = H(t || onion_address) Legitimate clients who want to fetch the descriptor also do the same, since they know both 't' and 'onion_address'. Descriptors are encrypted using a key derived from the onion_address. Hence, only clients that know the onion_address can decrypt it. Descriptors are signed using the long-term private key of the hidden service, and can be verified by clients who manage to decrypt the descriptor. --- Assuming the above is correct and makes sense (need more brain), it should maintain all the security properties above except from (e). So basically in this scheme, HSDirs won't be able to verify the signatures of received descriptors. The obvious question here is, is this a problem? IIUC, having the HSDirs verify those signatures does not offer any additional security, except from making sure that the descriptor signature was actually created using a legitimate ed25519 key. Other than that, I don't see it offering much. So, what does this additional HSDir verification offer? It seems like a weak way to ensure that no garbage is uploaded on the HSDir hash ring. However, any reasonable attacker will put their garbage in a descriptor and sign it with a random ed25519 key, and it will trivially pass the HSDir validation. So do we actually care about this property enough to introduce huge onion addresses to the system? Please discuss and poke holes at the above system. Cheers!

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