Most of the logic was redundant with checks already made in
ssl3_get_server_certificate. The DHE check was missing an ECDHE half
(and was impossible). The ECDSA check allowed an ECDSA certificate for
RSA. The only non-redundant check was a key usage check which,
strangely, is only done for ECDSA ciphers.
(Although this function called X509_certificate_type and checked sign
bits, those bits in X509_certificate_type are purely a function of the
key type and don't do anything.)
Change-Id: I8df7eccc0ffff49e4cfd778bd91058eb253b13cb
Reviewed-on: https://boringssl-review.googlesource.com/5047
Reviewed-by: Adam Langley <agl@google.com>
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