[tor-bugs] #20991 [Core Tor/Tor]: hs: Move end_sig_fields field of ESTABLISH_INTRO v3 cell before sig_len

Fri Dec 16 13:57:31 UTC 2016

#20991: hs: Move end_sig_fields field of ESTABLISH_INTRO v3 cell before sig_len
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 Reporter:  dgoulet          |          Owner:  dgoulet
     Type:  defect           |         Status:  accepted
 Priority:  Medium           |      Milestone:  Tor: 0.3.0.x-final
Component:  Core Tor/Tor     |        Version:
 Severity:  Normal           |     Resolution:
 Keywords:  tor-hs, prop224  |  Actual Points:
Parent ID:  #17241           |         Points:
 Reviewer:                   |        Sponsor:  SponsorR-must
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Comment (by nickm):

 The signature length IMO _needs_ to be unauthenticated, or we'll never be
 able to support another signature method with variable-length keys.

 Imagine if we were doing this with RSA instead of Ed25519: If we had to
 authenticate the signature length, we couldn't actually sign anything
 reliably, since we wouldn't know the signature length for sure until we
 had made the signature.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20991#comment:5>
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