[tor-bugs] #3122 [Tor Client]: Write and use constant-time comparison functions

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#3122: Write and use constant-time comparison functions
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 Reporter:  rransom      |          Owner:  ioerror
     Type:  enhancement  |         Status:  new    
 Priority:  major        |      Milestone:         
Component:  Tor Client   |        Version:         
 Keywords:               |         Parent:         
   Points:               |   Actualpoints:         
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Comment(by ioerror):

 Replying to [comment:6 rransom]:
 > Replying to [comment:2 cypherpunks]:
 > > There are a lot of places in the code where memcmp() is called on
 memory buffers that look like they might contain various hashes or
 digests:
 >
 > Applying memcmp to a hash or digest is not normally a problem.  memcmp
 is only dangerous when applied to a MAC, password, or other secret value
 which the attacker can attempt to guess one byte at a time.

 I'm not so sure that every digest we compare will be public or that every
 digest comparison is not a problem. I think that generally, we need to
 show that each one is safe based on some assumptions and then weigh the
 changes of those assumptions ever changing...

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3122#comment:7>
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