X.509: Check the algorithm IDs obtained from parsing an X.509 certificate

Check that the algorithm IDs obtained from the ASN.1 parse by OID lookup
corresponds to algorithms that are available to us.
Reported-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NDavid Howells <dhowells@redhat.com>

crypto/asymmetric_keys/x509_public_key.c

@@ -119,6 +119,17 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 
 	pr_devel("Cert Issuer: %s\n", cert->issuer);
 	pr_devel("Cert Subject: %s\n", cert->subject);
+
+	if (cert->pub->pkey_algo >= PKEY_ALGO__LAST ||
+	    cert->sig.pkey_algo >= PKEY_ALGO__LAST ||
+	    cert->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
+	    !pkey_algo[cert->pub->pkey_algo] ||
+	    !pkey_algo[cert->sig.pkey_algo] ||
+	    !pkey_hash_algo_name[cert->sig.pkey_hash_algo]) {
+		ret = -ENOPKG;
+		goto error_free_cert;
+	}
+
 	pr_devel("Cert Key Algo: %s\n", pkey_algo_name[cert->pub->pkey_algo]);
 	pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
 		 cert->valid_from.tm_year + 1900, cert->valid_from.tm_mon + 1,