[tor-project] Anti-censorship team meeting notes, 2023-03-09

Thu Mar 9 17:08:28 UTC 2023

Hey everyone!

Here are our meeting logs:

http://meetbot.debian.net/tor-meeting/2023/tor-meeting.2023-03-09-15.58.html

And our meeting pad:

Anti-censorship
--------------------------------

Next meeting: Thursday, March 16 16:00 UTC

Weekly meetings, every Thursday at 16:00 UTC, in #tor-meeting at OFTC
(channel is logged while meetings are in progress)

== 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 sponsors, we are working on:
		* All needs review tickets:
			* https://gitlab.torproject.org/groups/tpo/anti-censorship/-/merge_requests?scope=all&utf8=%E2%9C%93&state=opened&assignee_id=None
		* Sponsor 28
			* must-do tickets: https://gitlab.torproject.org/groups/tpo/-/milestones/10
			* possible-do tickets: https://gitlab.torproject.org/groups/tpo/-/issues?scope=all&utf8=%E2%9C%93&state=opened&label_name%5b%5d=Sponsor%2028&milestone_title=None
		* Sponsor 96
			* https://gitlab.torproject.org/groups/tpo/-/milestones/24
		* Sponsor 139 <-- hackerncoder, irl, joydeep, meskio, emmapeel working on it
			* https://pad.riseup.net/p/sponsor139-meeting-pad

== Announcements ==

== Discussion ==

	* No news yet about the inclusion of snowflake-02 in Orbot, after asking at S96 meeting.
		* the are asking meskio by email privately, but he didn't answer being in vacation, will do today

	* What is the procedure for creating a new repository under https://gitlab.torproject.org/tpo/anti-censorship ? Do I need to ask someone to create a repository or can I just do it?
		* dcf wants to move other repositories there:
			* https://gitlab.torproject.org/dcf/extor-static-cookie
			* https://gitweb.torproject.org/pluggable-transports/goptlib.git
		* It should be possible to just create new repos.
		* dcf will try it, and report back if there's trouble.

	* Resynchronization with Upsteamed Remove HelloVerify countermeasure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/issues/40258#note_2883726)
		* Syncing with upstream will require dropping one version of golang from CI, are we okay with that?
		* https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/merge_requests/131#note_2869188 "The only problem I'm having with this is that it no longer builds with go1.15 due to the x/crypto dependency update. Is it possible to keep the old version or perhaps rebase these changes off of the versions of pion/dtls and pion/webrtc that we currently have pinned rather than the master branches?"
		* go1.15 is the version in current Debian stable (bullseye), go1.19 is available in backports. go1.19 will be the version in the next stable (bookworm) coming in a few months.

== Actions ==

	* move the ampcache snowflake fallback forward

== Interesting links ==

	* 

== Reading group ==

This paper is about detecting Tor-in-obfs4 when you only have a traffic sample; e.g., you only get to look at every 100th packet that passes through a router that handles both obfs4 and non-obfs4 flows. Traffic sampling means you cannot use features like "look at the first n packets of a flow" or "compare the timing of two consecutive packets". Instead, you can only look at aggregate statistical features and have to be memory-efficient.
The system collects 12 statistics (Table III in the appendix) and stores them in a data structure called a nest count Bloom filter (NCBF), which essentially is just a composition of 12 counting Bloom filters (https://en.wikipedia.org/wiki/Counting_Bloom_filter). The statistics are things like "number of non-empty upstream packets" (C₂) and "number of downstream packets with payload length between 62 and 465" (C₁₁). From these 12 statistics, they derive 14 features (mostly ratios of statistics) and feed them to a random forest classifier.
For evaluation they use a 15-minute sample of backbone traffic provided by a third party, MAWI (https://mawi.wide.ad.jp/mawi/ditl/ditl2019-G/201904090000.html) and insert their own self-collected obfs4 traffic into it. They say the detection has few false negatives (finds almost all obfs4 bridges), but too many false positives to be usable directly for blocking decisions; they mention the need for "secondary testing" of suspected bridges.

	* We will discuss "Detecting Tor Bridge from Sampled Traffic in Backbone Networks" on March 9
		* https://www.ndss-symposium.org/wp-content/uploads/madweb2021_23011_paper.pdf
		* https://www.youtube.com/watch?v=kL7YCRer3To&list=PLfUWWM-POgQvGOVAk1HjP3uFKoY93_-q9&index=5
		* 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): last updated 2023-03-02
Last week:
    - Lox tor browser integration work in progress
        - https://gitlab.torproject.org/tpo/anti-censorship/team/-/issues/116
        - Finished getting the wasm client integrated as a Tor Browser module
This week:
    - continue Lox tor browser integration
        - find a better way to generate and call wasm client in tor-browser-build
        - make team repos for Lox pieces
        - expand client-side support for more Lox features
    - continue work on conjure client-side recovery
Needs help with:

dcf: 2023-03-09
	Last week:
		- drafted snowflake-01 bridge update for February 2023 https://opencollective.com/censorship-circumvention/projects/snowflake-daily-operations/updates/2023-february-update1
		- attended 2023-03-04 relay operators meetup and answered questions about snowflake https://lists.torproject.org/pipermail/tor-relays/2023-March/021080.html
		- documented further sporadic blocking of cdn.sstatic.net in some networks in Iran https://gitlab.torproject.org/tpo/anti-censorship/team/-/issues/115#note_2883298
		- made a graph of users in Russia since Tor Browser 12.0.3 and the Hello Verify mitigation; curiously it increased users in snowflake-02 but not snowflake-01 https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/merge_requests/131#note_2883300
		- noticed that conntrack changes did not persist after a reboot on the snowflake bridges, and started an experiment to measure the effect https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/issues/40259
	Next week:
		- migrate goptlib to gitlab https://gitlab.torproject.org/tpo/anti-censorship/team/-/issues/86#note_2823122 (for real)
	Help with:

meskio: 2023-03-09
   Last week:
       - catch up (or fail to) after vacation
       - deploy and break bridgedb (bridgedb#40064)
       - test bridges without ORPort public (rdsys#154)
       - review nil pointer fix in webtunnel (webtunnel!5)
       - coordinate the update of pion libraries and snowflake in debian, including the HelloVerify patch
   Next week:
       - rdsys fixes to use onbasca (rdsys#153)

Shelikhoo: 2023-03-09
   Last Week:
		- [Merge Request Awaiting] Add SOCKS5 forward proxy support to snowflake (snowflake!64)
		- [Research] HTTPT Planning https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/httpt/-/issues/1
		- WebTunnel @ TorBrowser mobile(https://gitlab.torproject.org/tpo/applications/tor-browser-build/-/merge_requests/663#note_2882700)
		- Upstreaming Remove HelloVerify countermeasure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/issues/40249)
		- Fix return nil error on unrecognized request http upgrade failure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtunnel/-/merge_requests/5)
		- Research on dynamic bridge DOL in china(https://gitlab.torproject.org/tpo/anti-censorship/connectivity-measurement/logcollector-admin/-/issues/7#note_2881520)
		- meta: fill the "donate" link on addons.mozilla.org (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake-webext/-/issues/79#note_2884226)
		- consider propagating 2FA everywhere, maybe at the April Tor Meeting (https://gitlab.torproject.org/tpo/tpa/team/-/issues/41083#note_2884138)
		- Review Proxy: add an option to bind to a specific address  (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/merge_requests/136#note_2883837)
		- Resynchronization with Upsteamed Remove HelloVerify countermeasure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/issues/40258#note_2883726)
   Next Week:
		- [Research] WebTunnel planning (Continue)
		- Try to find a place to host another vantage point
		- Fix return nil error on unrecognized request http upgrade failure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtunnel/-/merge_requests/5)
		- Resynchronization with Upsteamed Remove HelloVerify countermeasure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/issues/40258#note_2883726)

onyinyang: 2023-03-09
    Last week:
        - Working on distributor backend for Lox server (integration with rdsys)
	        - enabling Lox server to communicate with rdsys through rdsys-backend-api
    This week:
        - Continuing work on Lox server integration with rdsys
	        - Reconfigure Lox Bridgeline to fit with Tor's bridge info
	        - Figure out the proper multithreading in Rust to add bridges to Lox's bridgedb
				- (later) Consider a reasonable approach for bridge groupings for Lox buckets

Itchy Onion: 2023-03-08
    Last week:
		- Finished most of issue #40252 (Standalone proxy outbound address) (!136)
		- Worked on issue #40252 (NAT probetest for standalone proxy)
		- Started looking at #40231 (Client sometimes send offer with no ICE candidates)
    This week:
		- Add warning message if the user provided IP address is not used by proxy to establish WebRTC connection (issue #40252 !136). In my testing, sometimes the IP obtained from Pion's selectedCandidatePair is not accurate. I chatted with Pion dev and think there might a bug in Pion. But from my testing it only happens on the first peerconnecion so not a huge problem for us.
		- Closed issue #40252 (NAT probetest for standalone proxy)
		- Working on #40231 (Client sometimes send offer with no ICE candidates). My current understanding is that this shouldn't happen. There was a similar issue but is fixed and merged: https://github.com/pion/webrtc/issues/1143. Doing more research on it.

hackerncoder: 2023-03-09
    last week:
    Next week:
        - getting ooni-exporter to work with torsf (snowflake)
        - ooni-exporter web_connectivity
        - work on "bridgetester"?
        - how does iran block bridges

cece: 2022-12-22
    This week:
        - working on creating a dummy WhatsApp bot
    Next week:
        - My bot is not yet working as expected s? still trying to figure that out
    Help with:
	     - resources

-- 
meskio | https://meskio.net/
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 My contact info: https://meskio.net/crypto.txt
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Nos vamos a Croatan.
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