Reposting here for more exposure as intrigeri advised. Updated with new info:
Hi Whonix dev here. We are currently working on tackling multiple side and covert channels of TCP which was inspired by your previous research and solution for TCP Timestamps. I would appreciate your help in thinking about and testing the suggested mitigation for an attack related to CPU load effect on inter-packet timing. A Tor user posted an attack he discovered about possibility of influencing packet latency (ping in this case) by manipulating CPU load thanks to CPU powersaving features (C-states). An attacker would easily use this as a covert channel to deanonymize users: https://lists.torproject.org/pipermail/tor-talk/2016-July/041908.html We discussed solutions with him and the most feasible I thought of was withholding groups of packets for a random time delay to destroy any covert messaging an adversary might attempt. He wrote some code at the time where unfortunately 1) The package doesn’t build 2) pulls dependencies from unsecure sources outside Debian then he stopped communicating. https://github.com/ethan2-0/nfqueue-packet-delay Fast forward years later, I am revisiting this with a fresh perspective and manage to find a utility on Linux and that’s packaged in Debian that readily induces package delays on a chosen interface. tc-netem part of the iproute2 suite does what we need using Kernel features. Turns out the Tor Project had this same attack on their radar, but they are swamped with lots of more urgent tasks. What remains is to come up with the right parameters for tc that provide measurable protection against this attack while not disrupting network performance. The math behind the defenses and testing that they work is admittedly above my pay grade. I hope to kickstart the conversation here with capable minds who can collaborate with them and fix this. https://github.com/mikeperry-tor/vanguards/issues/46 *** Offtopic: Cyrus a PhD student has kindly authored Tirdad a kernel module for mitgating another related problem, that of TCP ISNs. Feel free to deploy the package in in Tails. https://github.com/Whonix/tirdad _______________________________________________ Tails-dev mailing list [email protected] https://www.autistici.org/mailman/listinfo/tails-dev To unsubscribe from this list, send an empty email to [email protected].
