[tor-bugs] #28398 [Core Tor/Stem]: Please provide a method on descriptors for calculating digests

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#28398: Please provide a method on descriptors for calculating digests
---------------------------+------------------------
 Reporter:  irl            |          Owner:  atagar
     Type:  enhancement    |         Status:  new
 Priority:  Medium         |      Milestone:
Component:  Core Tor/Stem  |        Version:
 Severity:  Normal         |     Resolution:
 Keywords:                 |  Actual Points:
Parent ID:                 |         Points:
 Reviewer:                 |        Sponsor:
---------------------------+------------------------

Comment (by irl):

 For ServerDescriptor and ExtraInfoDescriptor, the digest() method is
 exactly what I want for SHA-1, but there is no equivalent for SHA-256.

 https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n712

 {{{
        "sha256-digest" is a base64-encoded SHA256 digest of the extra-info
        document, computed over the same data.
 }}}

 For votes only SHA-1 seems to be specified but SHA-256 could be
 implemented in the same way as above:

 https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n2223

 {{{
         A digest of the vote from the authority that contributed to this
         consensus, as signed (that is, not including the signature).
         (Hex, upper-case.)
 }}}

 For flavoured consensuses:

 https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n3321

 {{{
     "additional-digest" SP flavor SP algname SP digest NL

         [Any number.]

         For each supported consensus flavor, every directory authority
         adds one or more "additional-digest" lines.  "flavor" is the name
         of the consensus flavor, "algname" is the name of the hash
         algorithm that is used to generate the digest, and "digest" is the
         hex-encoded digest.

         The hash algorithm for the microdescriptor consensus flavor is
         defined as SHA256 with algname "sha256".
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28398#comment:2>
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