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Re: [tor-bugs] #30921 [Core Tor/Tor]: hs-v3: Close intro circuits when cleaning up the client descriptor cache
#30921: hs-v3: Close intro circuits when cleaning up the client descriptor cache
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Reporter: dgoulet | Owner: dgoulet
Type: defect | Status: needs_revision
Priority: Medium | Milestone: Tor: 0.4.2.x-final
Component: Core Tor/Tor | Version:
Severity: Normal | Resolution:
Keywords: tor-hs, tor-client | Actual Points: 0.1
Parent ID: #28970 | Points: 0.1
Reviewer: asn | Sponsor: Sponsor27-must
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Comment (by asn):
Replying to [comment:5 dgoulet]:
> Replying to [comment:4 asn]:
> > Hmm, some questions about this fix:
> >
> > - I'm not sure if the identified race condition is the cause of this
assert. Looking at #28970, there are two asserts and the second one is on
`hs_ident_intro_circ_is_valid()` which imples that the hs_ident exists but
is zeroed out. IIUC, this seems to be the reason that we can't find a
descriptor here, and not a race condition.
>
> I would argue that the "!desc" assert could be caused by what I outlined
and fixed in the patch. The "has opened" code path can't return an error
so after that assert is hit, we end up trying to send an INTRODUCE1 on the
circuit and then you hit the second assert.
>
> The reason why the `intro_auth_pk` key is zeroed is because the
`setup_intro_circ_auth_key()` failed before it could be filled (by not
finding the descriptor).
>
ACK agreed.
One last thing: Can you please outline the exact steps to enter this edge
case? IIUC, it's about a client who gets their intro circ opened at the
exact same second that their descriptor expired? This seems extremely rare
to me, and I wonder if there is a simpler explanation.
In particular, descriptors expire at "the start of the next time period",
and the logs in question were at 05:31, so not sure how expiry could work
this way.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30921#comment:6>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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