integrity: support EC-RDSA signatures for asymmetric_verify

Allow to use EC-RDSA signatures for IMA by determining signature type by
the hash algorithm name. This works good for EC-RDSA since Streebog and
EC-RDSA should always be used together.

Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: linux-integrity@vger.kernel.org
Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

security/integrity/digsig_asymmetric.c

@@ -104,9 +104,16 @@ int asymmetric_verify(struct key *keyring, const char *sig,
 
 	memset(&pks, 0, sizeof(pks));
 
-	pks.pkey_algo = "rsa";
 	pks.hash_algo = hash_algo_name[hdr->hash_algo];
-	pks.encoding = "pkcs1";
+	if (hdr->hash_algo == HASH_ALGO_STREEBOG_256 ||
+	    hdr->hash_algo == HASH_ALGO_STREEBOG_512) {
+		/* EC-RDSA and Streebog should go together. */
+		pks.pkey_algo = "ecrdsa";
+		pks.encoding = "raw";
+	} else {
+		pks.pkey_algo = "rsa";
+		pks.encoding = "pkcs1";
+	}
 	pks.digest = (u8 *)data;
 	pks.digest_size = datalen;
 	pks.s = hdr->sig;