TLS: Use os_memcmp_const() for hash/password comparisons

This makes the implementation less likely to provide useful timing
information to potential attackers from comparisons of information
received from a remote device and private material known only by the
authorized devices.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/tls/pkcs1.c

@@ -298,7 +298,7 @@ int pkcs1_v15_sig_ver(struct crypto_public_key *pk,
 		    hdr.payload, hdr.length);
 
 	if (hdr.length != hash_len ||
-	    os_memcmp(hdr.payload, hash, hdr.length) != 0) {
+	    os_memcmp_const(hdr.payload, hash, hdr.length) != 0) {
 		wpa_printf(MSG_INFO, "PKCS #1: Digest value does not match calculated hash");
 		os_free(decrypted);
 		return -1;

src/tls/tlsv1_client_read.c

@@ -962,7 +962,7 @@ static int tls_process_server_finished(struct tlsv1_client *conn, u8 ct,
 	wpa_hexdump_key(MSG_DEBUG, "TLSv1: verify_data (server)",
 			verify_data, TLS_VERIFY_DATA_LEN);
 
-	if (os_memcmp(pos, verify_data, TLS_VERIFY_DATA_LEN) != 0) {
+	if (os_memcmp_const(pos, verify_data, TLS_VERIFY_DATA_LEN) != 0) {
 		wpa_printf(MSG_INFO, "TLSv1: Mismatch in verify_data");
 		tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
 			  TLS_ALERT_DECRYPT_ERROR);

src/tls/tlsv1_common.c

@@ -481,7 +481,8 @@ int tls_verify_signature(u16 tls_version, struct crypto_public_key *pk,
 	}
 #endif /* CONFIG_TLSV12 */
 
-	if (buflen != data_len || os_memcmp(decrypted, data, data_len) != 0) {
+	if (buflen != data_len ||
+	    os_memcmp_const(decrypted, data, data_len) != 0) {
 		wpa_printf(MSG_DEBUG, "TLSv1: Invalid Signature in CertificateVerify - did not match calculated hash");
 		os_free(buf);
 		*alert = TLS_ALERT_DECRYPT_ERROR;

src/tls/tlsv1_record.c

@@ -456,7 +456,7 @@ int tlsv1_record_receive(struct tlsv1_record_layer *rl,
 			return -1;
 		}
 		if (hlen != rl->hash_size ||
-		    os_memcmp(hash, out_data + plen, hlen) != 0 ||
+		    os_memcmp_const(hash, out_data + plen, hlen) != 0 ||
 		    force_mac_error) {
 			wpa_printf(MSG_DEBUG, "TLSv1: Invalid HMAC value in "
 				   "received message (force_mac_error=%d)",

src/tls/tlsv1_server_read.c

@@ -1135,7 +1135,7 @@ static int tls_process_client_finished(struct tlsv1_server *conn, u8 ct,
 	wpa_hexdump_key(MSG_DEBUG, "TLSv1: verify_data (client)",
 			verify_data, TLS_VERIFY_DATA_LEN);
 
-	if (os_memcmp(pos, verify_data, TLS_VERIFY_DATA_LEN) != 0) {
+	if (os_memcmp_const(pos, verify_data, TLS_VERIFY_DATA_LEN) != 0) {
 		tlsv1_server_log(conn, "Mismatch in verify_data");
 		return -1;
 	}

src/tls/x509v3.c

@@ -1776,7 +1776,7 @@ skip_digest_oid:
 	}
 
 	if (hdr.length != hash_len ||
-	    os_memcmp(hdr.payload, hash, hdr.length) != 0) {
+	    os_memcmp_const(hdr.payload, hash, hdr.length) != 0) {
 		wpa_printf(MSG_INFO, "X509: Certificate Digest does not match "
 			   "with calculated tbsCertificate hash");
 		os_free(data);