[tor-bugs] #27971 [Core Tor/Tor]: Still supports 1024 bit keys

Tor Bug Tracker & Wiki blackhole at torproject.org
Wed Oct 10 17:14:09 UTC 2018


#27971: Still supports 1024 bit keys
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 Reporter:  kroeckx             |          Owner:  nickm
     Type:  defect              |         Status:  assigned
 Priority:  High                |      Milestone:  Tor: 0.3.5.x-final
Component:  Core Tor/Tor        |        Version:
 Severity:  Normal              |     Resolution:
 Keywords:  crypto regression?  |  Actual Points:
Parent ID:                      |         Points:
 Reviewer:                      |        Sponsor:
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Comment (by nickm):

 Okay, I've investigated this a bit more.

 Changing TLS_DH_PRIME to a 2048-bit prime is easy enough; after doing so,
 the 0.3.5 unit tests almost pass at security level 2, and "make test-
 network" passes.

 In 0.2.9, increasing the TLS prime length to 2048 is also okay. However,
 in 0.2.9, raising the security level to 2 makes a few dozen unit tests
 fail.

 Here's what I'd propose:
   * Raise the TLS prime size to the 2048-bit named prime from RFC7919 in
 0.2.9 and forward, fixing unit tests as needed.
   * In versions before 0.3.4 or 0.3.5, move the
 SSL_CTX_set_security_level(1) call to only happen in the unit tests.
   * In 0.3.5, remove the SSL_CTX_set_security_level() call entirely, and
 fix the one failing unit test.

 (I only tested this with OpenSSL 1.1.0i -- there might well be
 compatibility issues with other versions for us to sort out.)

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27971#comment:6>
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