WPS: Do not increment wildcard_uuid when pin is locked

Commit 84751b98c151f70c322b6b7f70d967400e147852 ('WPS: Allow wildcard
UUID PIN to be used twice') relaxed the constraints on how many time a
wildcard PIN can be used to allow two attempts. However, it did this in
a way that could result in concurrent attempts resulting in the wildcard
PIN being invalidated even without the second attempt actually going as
far as trying to use the PIN and a WPS protocol run.

wildcard_uuid is a flag/counter set for wildcard PINs and it is
incremented whenever the PIN is retrieved by wps_registrar_get_pin().
Eventually it causes the wildcard PIN to be released, effectively
limiting the number of registration attempts with a wildcard PIN.

With the previous implementation, when the PIN is in use and locked
(PIN_LOCKED), it is not returned from wps_registrar_get_pin() but
wildcard_uuid is still incremented which can cause the PIN to be
released earlier and stations will have fewer registration attempts with
it. Fix this scenario by only incrementing wildcard_uuid if the PIN is
actually going to be returned and used.

Signed-off-by: Lior David <qca_liord@qca.qualcomm.com>

src/wps/wps_registrar.c

@@ -880,6 +880,7 @@ static const u8 * wps_registrar_get_pin(struct wps_registrar *reg,
 					const u8 *uuid, size_t *pin_len)
 {
 	struct wps_uuid_pin *pin, *found = NULL;
+	int wildcard = 0;
 
 	wps_registrar_expire_pins(reg);
 
@@ -899,7 +900,7 @@ static const u8 * wps_registrar_get_pin(struct wps_registrar *reg,
 			    pin->wildcard_uuid == 2) {
 				wpa_printf(MSG_DEBUG, "WPS: Found a wildcard "
 					   "PIN. Assigned it for this UUID-E");
-				pin->wildcard_uuid++;
+				wildcard = 1;
 				os_memcpy(pin->uuid, uuid, WPS_UUID_LEN);
 				found = pin;
 				break;
@@ -921,6 +922,8 @@ static const u8 * wps_registrar_get_pin(struct wps_registrar *reg,
 	}
 	*pin_len = found->pin_len;
 	found->flags |= PIN_LOCKED;
+	if (wildcard)
+		found->wildcard_uuid++;
 	return found->pin;
 }