March 2021 - anti-censorship-team - lists.torproject.org

Microsoft announces shutting down domain fronting attempts in Azure
by Cecylia Bocovich 18 Nov '24

18 Nov '24

It looks like Azure is going to shutdown domain fronting: https://www.microsoft.com/security/blog/2021/03/26/securing-our-approach-to… There isn't a time frame listed in the article, and I haven't gotten any notifications through my Azure account yet. Cecylia

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Crash in Snowflake users since 2021-01-17
by David Fifield 17 Apr '21

17 Apr '21

I happened to look at the Snowflake bridge's bandwidth and user history page, and the counts are close to zero since yesterday. I haven't investigated it at all. https://metrics.torproject.org/rs.html#details/5481936581E23D2D178105D44DB6…

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TurboTunnel Packet Scheduler Tips and Traffic Analysis Benefits
by Mike Perry 31 Mar '21

31 Mar '21

Hi all, I recently posted a draft proposal for traffic splitting for Tor: https://gitlab.torproject.org/tpo/core/torspec/-/blob/master/proposals/329-… It has similar properties as TurboTunnel, but I put quite a bit of work and consulted with several TCP and multipath TCP researchers to develop the packet scheduling algorithms defined in Section 3: https://gitlab.torproject.org/tpo/core/torspec/-/blob/master/proposals/329-… You may be interested in adopting those algorithms, if possible. There are variants that optimize for latency, throughput, or both in combination. The proposal also supports resumption of closed circuits. I am writing this mail because while these things are nice, resumption in particular does not defend against all classes of issues I am worried about with respect to confirmation attacks from closing or blocking connections, particularly onion service connections: https://gitlab.torproject.org/tpo/core/torspec/-/blob/master/proposals/329-… Briefly, if an adversary suspects an onion service is in use at a particular guard, it can make a circuit to that onion service, hold it open, and then close TCP connections of that guard to see if the circuit closes. This can even be done on the side with TCP RST injection, and possibly even blindly with brute force RST spoofing and spamming, if a good enough guess can be made about the IP address range of the service. Worse, in this case, the resumption I specified for Conflux does not help here, because this adversary will see the service's resumption attempt, and use that for confirmation instead of circuit close. TurboTunnel's resumption and automatic bridge discovery and replacement should greatly mitigate this attack, because it happens at a layer that is not necessarily controlled by the adversary, and thus resumption is mostly invisible to them (save for delay, which Cecylia is working on minimizing). Additionally, since traffic splitting has been shown to help against website fingerprinting, it stands to reason that doing traffic splitting at multiple layers and multiple endpoints may actually be better than doing it at just one layer, and costs us little-to-nothing in terms of overhead: https://www.comsys.rwth-aachen.de/fileadmin/papers/2020/2020-delacadena-tra… So please, keep on improving TurboTunnel! And let's compare notes about what we learn! Looking forward to obfs4 TurboTunnel, too! -- Mike Perry

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Ansible role that installs snowflake proxy on Debian
by Jacobo Nájera 17 Mar '21

17 Mar '21

Hi, I wrote an ansible role to install snowflake proxy on Debian Buster. I will extend its support to Fedora and Ubuntu and improvements soon. https://galaxy.ansible.com/nvjacobo/snowflake Repo: https://github.com/nvjacobo/snowflake Feedback is welcome Thanks, Jacobo

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No time change for the anti-censorship meeting
by Cecylia Bocovich 17 Mar '21

17 Mar '21

Hey everyone, We can discuss this at the meeting, but I'd like to keep the meeting time at 16 UTC regardless of the time change in places that recognize a difference between daylight savings and standard time. So, if you are in the US or Canada our weekly meeting will be at a different wall clock time. But it will be at the same time in UTC :) Hopefully see you there! Cecylia

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Next anti-censorship reading group: 4 March 2021
by Cecylia Bocovich 01 Mar '21

01 Mar '21

Hey everyone! We will discuss "Investigating Large Scale HTTPS Interception in Kazakhstan" this week at our team meeting on 2021-03-04, at 16 UTC. Relevant links: - https://censoredplanet.org/assets/Kazakhstan.pdf - https://censoredplanet.org/kazakhstan Questions to ask and goals to have: - What can we learn from this work? - 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? Hope to see you all there! Cecylia

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