[tor-bugs] #26122 [Obfuscation/Censorship analysis]: obfs4proxy: closeAfterDelay() should to conform to obfs4 spec

[Tor Bug Tracker & Wiki]

#26122: obfs4proxy: closeAfterDelay() should to conform to obfs4 spec
---------------------------------------------+---------------------
 Reporter:  cypherpunks                      |          Owner:  dcf
     Type:  defect                           |         Status:  new
 Priority:  Medium                           |      Milestone:
Component:  Obfuscation/Censorship analysis  |        Version:
 Severity:  Normal                           |     Resolution:
 Keywords:                                   |  Actual Points:
Parent ID:                                   |         Points:
 Reviewer:                                   |        Sponsor:
---------------------------------------------+---------------------

Comment (by cypherpunks):

 Proposed fix:
 {{{
 -       // Consume and discard data on this connection until either the
 specified
 -       // interval passes or a certain size has been reached.
 -       discarded := 0
 -       var buf [framing.MaximumSegmentLength]byte
 -       for discarded < int(sf.closeDelayBytes) {
 +       // Consume and discard data on this connection until the specified
 +       // interval passes.
 +       var buf [maxHandshakeLength]byte
 +       for {
                 n, err := conn.Conn.Read(buf[:])
                 if err != nil {
                         return
                 }
 -               discarded += n
         }
 }}}

 This fix can also to stop some form of active probing attack discovered by
 #26083

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26122#comment:1>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online