[tor-bugs] #24659 [Core Tor/Tor]: Wrap our sha2 interface in Rust which implements the appropriate traits

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#24659: Wrap our sha2 interface in Rust which implements the appropriate traits
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 Reporter:  isis               |          Owner:  (none)
     Type:  enhancement        |         Status:  needs_review
 Priority:  Medium             |      Milestone:  Tor: 0.3.4.x-final
Component:  Core Tor/Tor       |        Version:
 Severity:  Normal             |     Resolution:
 Keywords:  rust, tor-crypto,  |  Actual Points:
Parent ID:                     |         Points:  1
 Reviewer:                     |        Sponsor:  Sponsor3-can
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Changes (by isis):

 * status:  new => needs_review
 * points:   => 1
 * sponsor:   => Sponsor3-can


Comment:

 I have a prototype (please don't merge! I have some cleanup work described
 in a couple XXX comments that I'd like to do first) just for SHA256. It
 could use a look over, just to make sure folks agree with the direction
 I've taken.  See my `bug24659`
 [https://github.com/isislovecruft/tor/tree/bug24659 branch] ([https
 ://travis-ci.org/isislovecruft/tor/builds/344169517 TravisCI results pass
 mostly], except for cargo in offline mode, because I added a dependency
 which isn't in the `tor-rust-dependencies` repo).

 Note on dependencies: the `digest` crate only contains traits, so that
 cryptographic code can implement the same interfaces and be inter-operable
 (with [https://crates.io/crates/digest/reverse_dependencies hundreds of
 other crates]!). Slightly unfortunately, at the moment, `digest` has a
 dependency on `generic_array`, but that'll be removed as soon as const
 generics are a thing in Rust (there's an accepted RFC, which is also IIUC
 available as a shepherded/mentored project for people wanting to
 contribute to Rust).

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24659#comment:4>
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