[tor-bugs] #7139 [Tor]: Tor involuntarily sets TLS session tickets

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#7139: Tor involuntarily sets TLS session tickets
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    Reporter:  nextgens            |        Type:  defect                        
      Status:  needs_review        |    Priority:  major                         
   Milestone:  Tor: 0.2.2.x-final  |   Component:  Tor                           
     Version:                      |    Keywords:  tor-relay ssl tls security pfs
      Parent:                      |      Points:                                
Actualpoints:                      |  
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Comment(by nextgens):

 You're not. PFS can't be achieved if you swap to disk... regardless of
 whether you use TLS session tickets or not.


 Now: another amendment of what I wrote above: for the record: OpenSSL does
 stores the ticket's encryption key in SSL_CTX, which in Tor's case is
 renewed every MAX_SSL_KEY_LIFETIME_INTERNAL... So that's your current PFS
 interval... and my initial report was accurately describing what is
 happening.


 The reasons to disable TLS session tickets in Tor's case are:
 - Not required / used at all (waste of CPU cycles and bandwidth)
 - Less attack surface exposed (hardening)
 - The PFS interval is MAX_SSL_KEY_LIFETIME_INTERNAL as you use 'ephemeral
 certificates' (keep in mind if you plan on increasing it)
 - The cipher negotiated is irrelevant ... No one will attack DHE-RSA-
 AES256-SHA if the ticket is encrypted using AES-128... so that's
 yetAnotherWaste of CPU cycles

 There is no direct security implication warranting an emergency release
 IMHO.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7139#comment:8>
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