[tor-bugs] #17796 [Core Tor/Tor]: Make crypto_digest_t allocated using minimal memory

Tor Bug Tracker & Wiki blackhole at torproject.org
Thu Jan 25 15:17:58 UTC 2018

#17796: Make crypto_digest_t allocated using minimal memory
 Reporter:  nickm         |          Owner:  (none)
     Type:  defect        |         Status:  closed
 Priority:  Low           |      Milestone:  Tor: 0.2.8.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:  implemented
 Keywords:                |  Actual Points:
Parent ID:                |         Points:
 Reviewer:                |        Sponsor:

Comment (by Hello71):

 I think that this is technically not defined by ISO C. it would be
 "better" to use a char flexible array member here. that would actually
 make the code simpler, since we use the digest as a "black box" anyways
 and just pass it to openssl. unfortunately, that requires C11 alignas.
 fortunately, MSVC supports that already.

 but... in practice, I highly doubt any compiler will compile this in an
 unexpected manner, especially since we only pass the buffer as a pointer
 to openssl anyways.

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17796#comment:9>
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