It doesn't depend on the cipher now that export ciphers are gone. It need only
be called once. Also remove the valid bit; nothing ever reads it. Its output is
also only used within a function, so make mask_k and mask_a local variables.
So all the configuration-based checks are in one place, change the input
parameter from CERT to SSL and move the PSK and ECDHE checks to the mask
computation. This avoids having to evaluate the temporary EC key for each
cipher.
The remaining uses are on the client which uses them differently (disabled
features rather than enabled ones). Those too may as well be local variables,
so leave a TODO.
Change-Id: Ibcb574341795d4016ea749f0290a793eed798874
Reviewed-on: https://boringssl-review.googlesource.com/2287
Reviewed-by: Adam Langley <agl@google.com>