certs: Add ECDSA signature verification self-test

certs: Add ECDSA signature verification self-test

Commit c27b2d2012e1 ("crypto: testmgr - allow ecdsa-nist-p256 and -p384
in FIPS mode") enabled support for ECDSA in crypto/testmgr.c. The
PKCS#7 signature verification API builds upon the KCAPI primitives to
perform its high-level operations. Therefore, this change in testmgr.c
also allows ECDSA to be used by the PKCS#7 signature verification API
(in FIPS mode).

However, from a FIPS perspective, the PKCS#7 signature verification API
is a distinct "service" from the KCAPI primitives. This is because the
PKCS#7 API performs a "full" signature verification, which consists of
both hashing the data to be verified, and the public key operation.
On the other hand, the KCAPI primitive does not perform this hashing
step - it accepts pre-hashed data from the caller and only performs the
public key operation.

For this reason, the ECDSA self-tests in crypto/testmgr.c are not
sufficient to cover ECDSA signature verification offered by the PKCS#7
API. This is reflected by the self-test already present in this file
for RSA PKCS#1 v1.5 signature verification.

The solution is simply to add a second self-test here for ECDSA. P-256
with SHA-256 hashing was chosen as those parameters should remain
FIPS-approved for the foreseeable future, while keeping the performance
impact to a minimum. The ECDSA certificate and PKCS#7 signed data was
generated using OpenSSL. The input data is identical to the input data
for the existing RSA self-test.

Signed-off-by: Joachim Vandersmissen <git@jvdsn.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>