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Simplify certificate curve check for 1.2

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The comments were about the time we were using mbedtls_pk_ec(), which
can return NULL, which we don't want to propagate to other functions.

Now we're using mbedtls_pk_get_ec_group_id() with is a safer interface
(and works even when EC is provided by drivers).

The check for GROUP_NONE was an heritage from the previous NULL check.
However it's actually useless: if NONE were returned (which can't happen
or parsing of the certificate would have failed and we wouldn't be
here), then mbedtls_ssl_check_curve() would work and just say that the
curve wasn't valid, which is OK.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This commit is contained in:
Manuel Pégourié-Gonnard 2024-08-09 12:00:34 +02:00
parent 4938b693f3
commit 8a14aaaca5
1 changed files with 8 additions and 24 deletions
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26
library/ssl_tls.c
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@ -8050,35 +8050,19 @@ static int ssl_parse_certificate_verify(mbedtls_ssl_context *ssl,
* Secondary checks: always done, but change 'ret' only if it was 0
*/
/* Check curve for ECC certs */
#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
{
const mbedtls_pk_context *pk = &chain->pk;
/* If certificate uses an EC key, make sure the curve is OK.
* This is a public key, so it can't be opaque, so can_do() is a good
* enough check to ensure pk_ec() is safe to use here. */
if (mbedtls_pk_can_do(pk, MBEDTLS_PK_ECKEY)) {
/* and in the unlikely case the above assumption no longer holds
* we are making sure that pk_ec() here does not return a NULL
*/
mbedtls_ecp_group_id grp_id = mbedtls_pk_get_ec_group_id(pk);
if (grp_id == MBEDTLS_ECP_DP_NONE) {
MBEDTLS_SSL_DEBUG_MSG(1, ("invalid group ID"));
return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
}
if (mbedtls_ssl_check_curve(ssl, grp_id) != 0) {
ssl->session_negotiate->verify_result |=
MBEDTLS_X509_BADCERT_BAD_KEY;
if (mbedtls_pk_can_do(&chain->pk, MBEDTLS_PK_ECKEY) &&
mbedtls_ssl_check_curve(ssl, mbedtls_pk_get_ec_group_id(&chain->pk)) != 0) {
MBEDTLS_SSL_DEBUG_MSG(1, ("bad certificate (EC key curve)"));
ssl->session_negotiate->verify_result |= MBEDTLS_X509_BADCERT_BAD_KEY;
if (ret == 0) {
ret = MBEDTLS_ERR_SSL_BAD_CERTIFICATE;
}
}
}
}
#endif /* MBEDTLS_PK_HAVE_ECC_KEYS */
/* Check X.509 usage extensions (keyUsage, extKeyUsage) */
if (mbedtls_ssl_check_cert_usage(chain,
ciphersuite_info,
ssl->conf->endpoint,