The 'client' and 'server' halves are remnants of SSL 3.0 and Go
(originally) lacking a way to clone hash.Hash. The Go limitation meant
that computing SSL 3.0's proto-HMAC construction mutated the running
hash on Finished, so crypto/tls just maintained two of them.
Without SSL 3.0, this is no longer needed. That, however, leaves us with
having both a crypto.Hash and a hash.Hash, and both can't be named
'hash'. I stepped around this by storing the cipher suite itself and
using cipherSuite.hash().
Change-Id: Ia38880ae446949baa2181d33136c748cf5374664
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/46626
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
David Benjamin