[tor-bugs] #22934 [Core Tor/Tor]: PADDING cells can't be sent immediately after a VERSIONS cell

Sat Jul 15 10:19:23 UTC 2017

#22934: PADDING cells can't be sent immediately after a VERSIONS cell
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 Reporter:  teor                 |          Owner:
     Type:  defect               |         Status:  new
 Priority:  Medium               |      Milestone:  Tor: 0.3.2.x-final
Component:  Core Tor/Tor         |        Version:
 Severity:  Normal               |     Resolution:
 Keywords:  tor-spec, tor-relay  |  Actual Points:
Parent ID:  #18856               |         Points:  0.5
 Reviewer:                       |        Sponsor:
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Comment (by teor):

 It appears that the channel state isn't updated until the read completes.
 If a send no or one VPADDING cell between VERSIONS and PADDING, the
 connection is closed.
 If a send 1000, the connection completes.

 For a script that demonstrates this, see:
 https://github.com/teor2345/endosome/blob/master/client-or-22934.py

 I think we should fix this by changing the channel state immediately after
 the VERSIONS cell is read, rather than after all the cells in the buffer
 are processed.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22934#comment:1>
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