EAP-GPSK: 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_gpsk.c

@@ -565,7 +565,7 @@ static const u8 * eap_gpsk_validate_gpsk_3_mic(struct eap_gpsk_data *data,
 		wpa_printf(MSG_DEBUG, "EAP-GPSK: Failed to compute MIC");
 		return NULL;
 	}
-	if (os_memcmp(mic, pos, miclen) != 0) {
+	if (os_memcmp_const(mic, pos, miclen) != 0) {
 		wpa_printf(MSG_INFO, "EAP-GPSK: Incorrect MIC in GPSK-3");
 		wpa_hexdump(MSG_DEBUG, "EAP-GPSK: Received MIC", pos, miclen);
 		wpa_hexdump(MSG_DEBUG, "EAP-GPSK: Computed MIC", mic, miclen);

src/eap_server/eap_server_gpsk.c

@@ -433,7 +433,7 @@ static void eap_gpsk_process_gpsk_2(struct eap_sm *sm,
 		eap_gpsk_state(data, FAILURE);
 		return;
 	}
-	if (os_memcmp(mic, pos, miclen) != 0) {
+	if (os_memcmp_const(mic, pos, miclen) != 0) {
 		wpa_printf(MSG_INFO, "EAP-GPSK: Incorrect MIC in GPSK-2");
 		wpa_hexdump(MSG_DEBUG, "EAP-GPSK: Received MIC", pos, miclen);
 		wpa_hexdump(MSG_DEBUG, "EAP-GPSK: Computed MIC", mic, miclen);
@@ -502,7 +502,7 @@ static void eap_gpsk_process_gpsk_4(struct eap_sm *sm,
 		eap_gpsk_state(data, FAILURE);
 		return;
 	}
-	if (os_memcmp(mic, pos, miclen) != 0) {
+	if (os_memcmp_const(mic, pos, miclen) != 0) {
 		wpa_printf(MSG_INFO, "EAP-GPSK: Incorrect MIC in GPSK-4");
 		wpa_hexdump(MSG_DEBUG, "EAP-GPSK: Received MIC", pos, miclen);
 		wpa_hexdump(MSG_DEBUG, "EAP-GPSK: Computed MIC", mic, miclen);