Hey everyone! Here are our meeting logs: http://meetbot.debian.net/tor-meeting/2025/tor-meeting.2025-09-25-16.00.html And our meeting pad: Anti-censorship work meeting pad -------------------------------- Anti-censorship -------------------------------- Next meeting: Thursday, October 2 16:00 UTC Facilitator: meskio ^^^(See Facilitator Queue at tail) Weekly meetings, every Thursday at 16:00 UTC, in #tor-meeting at OFTC (channel is logged while meetings are in progress) This week's Facilitator: onyinyang == Goal of this meeting == Weekly check-in about the status of anti-censorship work at Tor. Coordinate collaboration between people/teams on anti-censorship at the Tor Project and Tor community. == Links to Useful documents ==     * Our anti-censorship roadmap:         * Roadmap:https://gitlab.torproject.org/groups/tpo/anti-censorship/-/boards     * The anti-censorship team's wiki page:         * https://gitlab.torproject.org/tpo/anti-censorship/team/-/wikis/home     * Past meeting notes can be found at:         * https://lists.torproject.org/pipermail/tor-project/     * Tickets that need reviews: from projects, we are working on:         * All needs review tickets:             * https://gitlab.torproject.org/groups/tpo/anti-censorship/-/merge_requests?sc...         * Project 158 <-- meskio working on it             * https://gitlab.torproject.org/groups/tpo/anti-censorship/-/issues/?label_nam... == Announcements == == Discussion ==     * Dual-stack bridges         * Serge has been change not to test reachability, so its opinion on "Running" is useful again.         * Now need to work on Onionoo and metrics.         * But: the data that bridgestrap sends to CollecTor is incorrect for bridges that run multiple transports.             * "collector output doesn't handle multiple transports correctly" https://gitlab.torproject.org/tpo/anti-censorship/bridgestrap/-/issues/48             * (A bridge can be "Running" with respect to one transport but not "Running" with respect to another transport.)         * Related: obfs4 (say) bridges that run on multiple IPv4 addresses.             * This is not generally technically possible at the moment, because both torrc syntax and the PT protocol have limitations that assume there is at most one instance of any transport name.                 * "Multiple ServerTransportListenAddr entries should be allowed per transport" https://gitlab.torproject.org/tpo/core/tor/-/issues/11211             * But it is possible with dual-stack (IPv4 and IPv6) bridges: they effectively have 2 IP addresses (one IPv4, one IPv6) that they listen on, with the same relay fingerprint and obfs4 cert.             * A desired feature is the ability to run multiple instances of obfs4, with a *different* obfs4 cert per listening IP address. For this, just being able to pass multiple bindaddrs would suffice.         * Another desired feature: run a single bridge with many listening IP addresses, an IPv4 /24 or IPv6 /56 for example.         * Where to send a written-up change proposal?             * There is a repo for spec proposals, https://gitlab.torproject.org/tpo/core/torspec/, but for this it's probably better to write it up in https://gitlab.torproject.org/tpo/anti-censorship/bridgestrap/-/issues/48.             * "for the format changes, i would suggest specing out what those would look like more precisely and the changes they'd require in onionoo and metrics so that meskio and someone from the metrics team can review it and discuss" == Actions ==     * Remove webtunnel setuid script in 3 weeks.(decrease this by one every week) == Interesting links ==     * == Reading group ==     * We will discuss "The Internet Coup" on October 23rd         * https://interseclab.org/wp-content/uploads/2025/09/The-Internet-Coup_Septemb...         * Particularly relevant sections: "Blocking online privacy and circumvention tools" section of InterSecLab report on Geedge Networks, mentions Tor, Snowflake, WebTunnel         * Notes: https://github.com/net4people/bbs/issues/519#issuecomment-3282101626         * Questions to ask and goals to have:             * What aspects of the paper are questionable?             * Are there immediate actions we can take based on this work?             * Are there long-term actions we can take based on this work?             * Is there future work that we want to call out in hopes that others will pick it up? == Updates == Name:         This week:             - What you worked on this week.         Next week:             - What you are planning to work on next week.         Help with:             - Something you need help with. cecylia (cohosh): 2025-09-25     Last week:         - released new version of snowflake webext with translation fix         - cleaned up some remaining snowflake website decoupling tasks (snowflake-webext#121)             - bug fix for available translations         - wrote shadow experiment generation scripts         - started researching proxy distribution changes and enumeration attacks on snowflake     Next week:         - release a new webext version to fix available translation bug         - follow up on snowflake rendezvous failures         - deploy new snowflake webextension with translation fixes         - take a look at potential snowflake orbot bug             - https://github.com/guardianproject/orbot-android/issues/1183 dcf: 2025-09-25     Last week:         - merged a metrics timeline event https://gitlab.torproject.org/tpo/network-health/metrics/timeline/-/merge_re...         - updated links gitweb→gitlab in metrics-timeline https://gitlab.torproject.org/tpo/network-health/metrics/timeline/-/issues/1...         - closed a metrics-timeline issue about automatically importing events from outside sources as not planned https://gitlab.torproject.org/tpo/network-health/metrics/timeline/-/issues/7     Next week:         - open issue to have snowflake-client log whenever KCPInErrors is nonzero https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...             - parent: https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf... Help with: meskio: 2024-09-11     Last week:         - brainstorm on dual stack bridges (tor!786)         - catch up with emails and fail     Next week: Shelikhoo: 2024-09-18     Last Week:          - [Testing] Unreliable+unordered WebRTC data channel transport for Snowflake rev2 (cont.)( https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf... ) testing environment setup/research          - Compiled patched tor browser for snowflake udp transport mode          - parpared test instruction for snowflake udp transport mode ( https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf... )     Next (working) Week/TODO:         - Merge request reviews         - [Deployment]Unreliable+unordered WebRTC data channel transport for Snowflake rev2 (cont.)( https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf... ) Building custom Tor Browser with patch applied         - repair russian vantage point issues onyinyang: 2025-09-25     Last week(s):         - Refactored solution for distributing a proportion of webtunnel bridges to telegram users with new accounts https://gitlab.torproject.org/tpo/anti-censorship/rdsys/-/issues/283         - #249 bug is back: https://gitlab.torproject.org/tpo/anti-censorship/rdsys/-/merge_requests/593         - Looked into conjure issue from China Next week:         - Continue looking into bridgestrap#47         - Lox still seems to be filling up the disk on the rdsys-test server despite changes made to delete old entries, look into what's going wrong       Switch back to some of these:           As time allows:                Blog post for conjure: https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/conju...               - review Tor browser Lox integration https://gitlab.torproject.org/tpo/applications/tor-browser/-/merge_requests/...               - add TTL cache to lox MR for duplicate responses: https://gitlab.torproject.org/tpo/anti-censorship/lox/-/merge_requests/305         - Work on outstanding milestone issues:             - key rotation automation         Later:         pending decision on abandoning lox wasm in favour of some kind of FFI? https://gitlab.torproject.org/tpo/applications/tor-browser/-/issues/43096):             - add pref to handle timing for pubkey checks in Tor browser             - add trusted invitation logic to tor browser integration: https://gitlab.torproject.org/tpo/applications/tor-browser/-/issues/42974         - improve metrics collection/think about how to show Lox is working/valuable         - sketch out Lox blog post/usage notes for forum     (long term things were discussed at the meeting!):         - brainstorming grouping strategies for Lox buckets (of bridges) and gathering context on how types of bridges are distributed/use in practice             Question: What makes a bridge usable for a given user, and how can we encode that to best ensure we're getting the most appropriate resources to people?                 1. Are there some obvious grouping strategies that we can already consider?                     e.g., by PT, by bandwidth (lower bandwidth bridges sacrificed to open-invitation buckets?), by locale (to be matched with a requesting user's geoip or something?)                 2. Does it make sense to group 3 bridges/bucket, so trusted users have access to 3 bridges (and untrusted users have access to 1)? More? Less? theodorsm: 2025-06-12         Last weeks:             - Applying for funding from NLnet to implement DTLS 1.3 in Pion. Got through the first round.             - Writing paper for FOCI: continuation of master thesis about reducing distinguishability of DTLS in Snowflake by implementing covert-dtls, further analysis of collected browser fingerprint and stability test of covert-dtls in snowflake proxies. Draft: https://theodorsm.net/FOCI25             - Key takeaways:                 * covert-dtls is stable when mimicking DTLS 1.2 handshakes, while the randomization approach— though more resistant to fingerprinting — tends to be less stable.                 * Chrome webextensions are more unstable than standalone proxies                 * covert-dtls should be integrated in Snowflake proxies as they produce the ClientHello messages during the DTLS handshake.                 * Chrome randomizes the order of extension list.                 * Firefox uses DTLS 1.3 by default in WebRTC.                 * A prompt adoption of DTLS 1.3 in both Snowflake and our fingerprint-resistant library is needed to keep up with browsers                 * The evolution of browsers’ fingerprints had no noticeable effect on Snowflake’s number of daily users over the last year.                 * Even with a sharp drop in the amount of proxies, it does not seem to affect the number of Snowflake users.                 * Browser extensions make Snowflake resistant to ClientHello fingerprinting.                 * Standalone proxies can serve more Snowflake clients per volunteer than webextensions.                 * We need metrics on which types of proxies are actually being matched and successfully used by clients.         Next weeks:             - Getting paper camera ready.             - Fix merge conflicts in MR (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...).         Help with:             - Should we do user testing of covert-dtls? Facilitator Queue:     meskio onyinyang shelikhoo 1. First available staff in the Facilitator Queue will be the facilitator for the meeting 2. After facilitating the meeting, the facilitator will be moved to the tail of the queue -- --- onyinyang GPG Fingerprint 3CC3 F8CC E9D0 A92F A108 38EF 156A 6435 430C 2036