#24469: Cannibalizing a circuit should check that first hop is in our guard state --------------------------+------------------------------------ Reporter: dgoulet | Owner: (none) Type: defect | Status: new Priority: Medium | Milestone: Tor: 0.3.3.x-final Component: Core Tor/Tor | Version: Severity: Normal | Resolution: Keywords: tor-circuit | Actual Points: Parent ID: | Points: Reviewer: | Sponsor: --------------------------+------------------------------------
Comment (by dgoulet): Replying to [ticket:24469 dgoulet]: > I noticed this on my v3 hidden service info logs which happened on Nov 22nd: > > {{{ > Nov 22 20:04:24.000 [info] internal (high-uptime) circ (length 4, last hop ThomasBernhardsHose): $175921396C7C426309AB03775A9930B6F611F794(open) $77159B89F39708B27CAC528FF32DD786569A11A5(open) $EE2D39A31F09EDD15B887B6EE7AB1396E52C3730(open) $A40E1C039224FA8072C7C84F729236FD738C69DA(open) > Nov 22 20:04:24.000 [info] connection_edge_process_relay_cell(): circuit_send_next_onion_skin() failed. > Nov 22 20:04:24.000 [warn] connection_edge_process_relay_cell (at origin) failed. > Nov 22 20:04:24.000 [warn] circuit_receive_relay_cell (backward) failed. Closing. > }}} > > So that circuit above has a Guard (`175921396C7C426309AB03775A9930B6F611F794`) that was removed a minute or so before: > > {{{ > Nov 22 20:03:39.000 [info] sampled_guards_update_from_consensus(): Removing sampled guard lovejoy ($175921396C7C426309AB03775A9930B6F611F794): it was sampled over 120 days ago, and confirmed over 60 days ago. > }}} > > Turns out that the circuit was cannibalized but tor made it failed because I assume our guard state wasn't available for that circuit which ultimately triggered those warnings. asn informed me that it is important that the circuit with old guard(s) stay alive for a while to help mitigate Guard discovery attacks. > > Bottom line, I think our cannibalized function should exclude any circuit that doesn't match our guard state. In the meantime, those warnings will appear in the logs. -- Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24469#comment:1> Tor Bug Tracker & Wiki <https://trac.torproject.org/> The Tor Project: anonymity online
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