EAP-PSK: 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/eap_peer/eap_psk.c

@@ -237,7 +237,7 @@ static struct wpabuf * eap_psk_process_3(struct eap_psk_data *data,
 		return NULL;
 	}
 	os_free(buf);
-	if (os_memcmp(mac, hdr3->mac_s, EAP_PSK_MAC_LEN) != 0) {
+	if (os_memcmp_const(mac, hdr3->mac_s, EAP_PSK_MAC_LEN) != 0) {
 		wpa_printf(MSG_WARNING, "EAP-PSK: Invalid MAC_S in third "
 			   "message");
 		ret->methodState = METHOD_DONE;

src/eap_server/eap_server_psk.c

@@ -314,7 +314,7 @@ static void eap_psk_process_2(struct eap_sm *sm,
 	}
 	os_free(buf);
 	wpa_hexdump(MSG_DEBUG, "EAP-PSK: MAC_P", resp->mac_p, EAP_PSK_MAC_LEN);
-	if (os_memcmp(mac, resp->mac_p, EAP_PSK_MAC_LEN) != 0) {
+	if (os_memcmp_const(mac, resp->mac_p, EAP_PSK_MAC_LEN) != 0) {
 		wpa_printf(MSG_INFO, "EAP-PSK: Invalid MAC_P");
 		wpa_hexdump(MSG_MSGDUMP, "EAP-PSK: Expected MAC_P",
 			    mac, EAP_PSK_MAC_LEN);