This was a mess. HMAC_CTX_copy_ex would avoid having to cleanup and init
the HMAC_CTX repeatedly, but even that is unnecessary. hctx_tpl was just
to reuse the key. Instead, HMAC_CTX already can be reset with the same
key. (Alas, with a slightly odd API, but so it goes.) Do that, and use
goto err to cleanup the error-handling.
Thanks to upstream's b98530d6e09f4cb34c791b8840e936c1fc1467cf for
drawing attention to this. (Though we've diverged significantly from
upstream with all the heap-allocated bits, so I didn't use the change
itself.)
While I'm here, tidy up some variable names and cite the newer RFC.
Change-Id: Ic1259f46b7c5a14dc341b8cee385be5508ac4daf
Reviewed-on: https://boringssl-review.googlesource.com/14605
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
42329a828b