The original motivation behind the sign/complete split was to avoid
needlessly hashing the input on each pass through the state machine, but
we're payload-based now and, in all cases, the payload is either cheap
to compute or readily available. (Even the hashing worry was probably
unnecessary.)
Tweak ssl_private_key_{sign,decrypt} to automatically call
ssl_private_key_complete as needed and take advantage of this in the
handshake state machines:
- TLS 1.3 signing now computes the payload each pass. The payload is
small and we're already allocating a comparable-sized buffer each
iteration to hold the signature. This shouldn't be a big deal.
- TLS 1.2 decryption code still needs two states due to reading the
message (fixed in new state machine style), but otherwise it just
performs cheap idempotent tasks again. The PSK code is reshuffled to
guarantee the callback is not called twice (though this was impossible
anyway because we don't support RSA_PSK).
- TLS 1.2 CertificateVerify signing is easy as the transcript is readily
available. The buffer is released very slightly later, but it
shouldn't matter.
- TLS 1.2 ServerKeyExchange signing required some reshuffling.
Assembling the ServerKeyExchange parameters is moved to the previous
state. The signing payload has some randoms prepended. This is cheap
enough, but a nuisance in C. Pre-prepend the randoms in
hs->server_params.
With this change, we are *nearly* rid of the A/B => same function
pattern.
BUG=128
Change-Id: Iec4fe0be7cfc88a6de027ba2760fae70794ea810
Reviewed-on: https://boringssl-review.googlesource.com/17265
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>
4414874f1f