[tor-bugs] #27471 [Core Tor/Tor]: HS intermittently fails: Non-fatal assertion failed in send_introduce1

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#27471: HS intermittently fails: Non-fatal assertion failed in send_introduce1
-------------------------------------------+-------------------------------
 Reporter:  tgragnato                      |          Owner:  dgoulet
     Type:  defect                         |         Status:  merge_ready
 Priority:  Very High                      |      Milestone:  Tor:
                                           |  0.3.5.x-final
Component:  Core Tor/Tor                   |        Version:  Tor:
                                           |  0.3.4.7-rc
 Severity:  Minor                          |     Resolution:
 Keywords:  tor-hs, regression?, 035-must  |  Actual Points:
Parent ID:                                 |         Points:
 Reviewer:  asn                            |        Sponsor:
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Changes (by dgoulet):

 * status:  needs_review => merge_ready


Comment:

 I'm happy with this! I thought of it a bit more and I think we should
 close the circuits here instead of re-extending on error. I think we'll
 fix more issues over time instead of dealing with an error because we have
 unusable circuits lying around.

 I thought of the attacker problem here where someone induces a client to
 fetch a descriptor (let say a malicious web page) and then somehow notices
 the close of the intro circuits and because the attacker would know the
 descriptor has new intro points, it could maybe deduce that it was in fact
 that .onion and thus I'm its Guard node.

 However, I doubt this is a practical attack considering the narrow window
 where we replace a descriptor while we have an intro circuit inflight. It
 can happen once at a client but I doubt it can happen enough to lead to
 information leak.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27471#comment:18>
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