Hey everyone! Here are our meeting logs: http://meetbot.debian.net/tor-meeting/2025/tor-meeting.2025-08-28-16.00.html And our meeting pad: Anti-censorship work meeting pad -------------------------------- Anti-censorship -------------------------------- Next meeting: Thursday, Sep 04 16:00 UTC Facilitator: onyinyang ^^^(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: shelikoo == 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 ==     * (Aug 28 New:)     * WebTunnel container's setuid volume migration trade-off         * https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtu...         * The problem was initially reported by gus at https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtu...         * The issue is that changing the base of the container from Debian bullseye to bookworm changed the uid of the system debian-tor user from 101 to 100. The unpatched new bookworm container image assumes a uid of 100, so permissions are wrong.         * Instructions for affected users have been published:             * https://forum.torproject.org/t/tor-relays-bridge-operators-fix-required-for-...         * There has already been a merged change for the debian-tor UID to be pinned at 101 (but it can only be compatible with one or the other, not both)             * https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtu...         * Proposal in !33 is to add a setuid binary to the container (with attendant security risks) whose purpose is to chown the relevant files and force them to correct UID for debian-tor, whatever that UID may be.         * How many WebTunnel bridges are affected?             * This would tell us how important it is to take the step of installing a setuid binary. If only a small number of bridges are affected, than maybe it's not worth it.             * Affected bridges won't even get to the bridgestrap step, so we won't have those logs.             * We could get a quick approximate count (to see if the number of webtunnel bridges has declined and how much) with https://metrics.torproject.org/collector.html#bridgedb-metrics.                 * Never mind, actually what we need are the extra-info descriptors.                 * Rough counts from the tor-metrics tarballs, shows a decrease of about 400 or 14% compared to 7 days earlier:                     $ tar -O -xf bridge-extra-infos-2025-08.tar.xz | grep -B3 '^transport webtunnel' | grep '^published '|grep 2025-08-21|wc -l                     3011                     $ tar -O -xf bridge-extra-infos-2025-08.tar.xz | grep -B3 '^transport webtunnel' | grep '^published '|grep 2025-08-27|wc -l                     2597         * We will take another sample from bridge metrics in 1 week, see how much the count has recovered, and then reevaluate the need for a setuid binary. == Actions == == Interesting links ==     * == Reading group ==     * We will discuss "IRBlock: A Large-Scale Measurement Study of the Great Firewall of Iran" on September 11         * https://www.petsymposium.org/foci/2025/foci-2025-0016.pdf         * 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): 2025-08-28     Last week:         - reviewed lots of MRs         - finished an updated of kcp-go and fixed some race conditions in the tests (snowflake#40483)         - worked on tracking down reason for snowflake rendezvous failures (snowflake#40447)     Next week:         - follow up on snowflake rendezvous failures         - take a look at potential snowflake orbot bug             - https://github.com/guardianproject/orbot-android/issues/1183 dcf: 2025-08-28     Last week:         - redeployed snowflake-server on snowflake-02 for golang.org/x/net security fix https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...         - opened issue to redeploy snowflake-server on snowflake-01 for golang.org/x/net security fix https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...     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: 2024-08-21     Last week:         - restore /bridges in telegram distributor (team#146)         - work with TPA to improve prometheus anti-censorship alerts         - many merge reviews     Next week:         - AFK Shelikhoo: 2024-08-28     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          - [Done] Create new webtunnel release( (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtu...)         - Merge request reviews         - [Done] Draft: Feature / SNI spoofing functionality for WebTunnel PT (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/lyreb...)     Next (working) Week/TODO:         - Merge request reviews         - Support the Testing of domain fronting sites ( https://gitlab.torproject.org/tpo/anti-censorship/connectivity-measurement/l... ) (cont.)         - [Deploy] Add Domain Fronting Test Support to probeobserver onyinyang: 2025-08-28     Last week(s):         - Monitoring fix for: https://gitlab.torproject.org/tpo/anti-censorship/rdsys/-/issues/249 https://gitlab.torproject.org/tpo/anti-censorship/rdsys/-/merge_requests/562         - Created visualizations for flickering bridges         - Fixing up translatable elements on bridges.torproject.org https://gitlab.torproject.org/tpo/anti-censorship/rdsys/-/merge_requests/574... Next week:         -Finish up with !574         - Deploy rdsys!567 when rdsys!562 is confirmed to be fixed and remove extra logs from rdsys!562         - Look into  why we are distributing malfunctioning webtunnel bridges https://gitlab.torproject.org/tpo/anti-censorship/bridgestrap/-/issues/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