WPS: Use only os_get_random() for PIN generation

Remove the fallback dependency on os_random() when generating a WPS pin.
This is exceptionally unlikely to ever be called as the call to
os_get_random() is unlikely to fail. The intention is to facilitate
future removal of os_random() as it uses a low quality PRNG.

Signed-off-by: Nick Lowe <nick.lowe@lugatech.com>

src/ap/wps_hostapd.c

@@ -1627,7 +1627,8 @@ const char * hostapd_wps_ap_pin_random(struct hostapd_data *hapd, int timeout)
 	unsigned int pin;
 	struct wps_ap_pin_data data;
 
-	pin = wps_generate_pin();
+	if (wps_generate_pin(&pin) < 0)
+		return NULL;
 	os_snprintf(data.pin_txt, sizeof(data.pin_txt), "%08u", pin);
 	data.timeout = timeout;
 	hostapd_wps_for_each(hapd, wps_ap_pin_set, &data);

src/wps/wps.h

@@ -837,7 +837,7 @@ int wps_build_credential_wrap(struct wpabuf *msg,
 
 unsigned int wps_pin_checksum(unsigned int pin);
 unsigned int wps_pin_valid(unsigned int pin);
-unsigned int wps_generate_pin(void);
+int wps_generate_pin(unsigned int *pin);
 int wps_pin_str_valid(const char *pin);
 void wps_free_pending_msgs(struct upnp_pending_message *msgs);
 

src/wps/wps_common.c

@@ -235,20 +235,18 @@ unsigned int wps_pin_valid(unsigned int pin)
  * wps_generate_pin - Generate a random PIN
  * Returns: Eight digit PIN (i.e., including the checksum digit)
  */
-unsigned int wps_generate_pin(void)
+int wps_generate_pin(unsigned int *pin)
 {
 	unsigned int val;
 
 	/* Generate seven random digits for the PIN */
-	if (random_get_bytes((unsigned char *) &val, sizeof(val)) < 0) {
-		struct os_time now;
-		os_get_time(&now);
-		val = os_random() ^ now.sec ^ now.usec;
-	}
+	if (random_get_bytes((unsigned char *) &val, sizeof(val)) < 0)
+		return -1;
 	val %= 10000000;
 
 	/* Append checksum digit */
-	return val * 10 + wps_pin_checksum(val);
+	*pin = val * 10 + wps_pin_checksum(val);
+	return 0;
 }
 
 

wpa_supplicant/ap.c

@@ -915,7 +915,10 @@ int wpa_supplicant_ap_wps_pin(struct wpa_supplicant *wpa_s, const u8 *bssid,
 		return -1;
 
 	if (pin == NULL) {
-		unsigned int rpin = wps_generate_pin();
+		unsigned int rpin;
+
+		if (wps_generate_pin(&rpin) < 0)
+			return -1;
 		ret_len = os_snprintf(buf, buflen, "%08d", rpin);
 		if (os_snprintf_error(buflen, ret_len))
 			return -1;
@@ -981,7 +984,8 @@ const char * wpas_wps_ap_pin_random(struct wpa_supplicant *wpa_s, int timeout)
 	if (wpa_s->ap_iface == NULL)
 		return NULL;
 	hapd = wpa_s->ap_iface->bss[0];
-	pin = wps_generate_pin();
+	if (wps_generate_pin(&pin) < 0)
+		return NULL;
 	os_snprintf(pin_txt, sizeof(pin_txt), "%08u", pin);
 	os_free(hapd->conf->ap_pin);
 	hapd->conf->ap_pin = os_strdup(pin_txt);

wpa_supplicant/ctrl_iface.c

@@ -956,7 +956,8 @@ static int wpa_supplicant_ctrl_iface_wps_pin(struct wpa_supplicant *wpa_s,
 	if (os_strcmp(cmd, "any") == 0)
 		_bssid = NULL;
 	else if (os_strcmp(cmd, "get") == 0) {
-		ret = wps_generate_pin();
+		if (wps_generate_pin((unsigned int *) &ret) < 0)
+			return -1;
 		goto done;
 	} else if (hwaddr_aton(cmd, bssid)) {
 		wpa_printf(MSG_DEBUG, "CTRL_IFACE WPS_PIN: invalid BSSID '%s'",

wpa_supplicant/p2p_supplicant.c

@@ -2578,7 +2578,13 @@ static void wpas_prov_disc_req(void *ctx, const u8 *peer, u16 config_methods,
 	params[sizeof(params) - 1] = '\0';
 
 	if (config_methods & WPS_CONFIG_DISPLAY) {
-		generated_pin = wps_generate_pin();
+		if (wps_generate_pin(&generated_pin) < 0) {
+			wpa_printf(MSG_DEBUG, "P2P: Could not generate PIN");
+			wpas_notify_p2p_provision_discovery(
+				wpa_s, peer, 0 /* response */,
+				P2P_PROV_DISC_INFO_UNAVAILABLE, 0, 0);
+			return;
+		}
 		wpas_prov_disc_local_display(wpa_s, peer, params,
 					     generated_pin);
 	} else if (config_methods & WPS_CONFIG_KEYPAD)
@@ -2623,7 +2629,13 @@ static void wpas_prov_disc_resp(void *ctx, const u8 *peer, u16 config_methods)
 	if (config_methods & WPS_CONFIG_DISPLAY)
 		wpas_prov_disc_local_keypad(wpa_s, peer, params);
 	else if (config_methods & WPS_CONFIG_KEYPAD) {
-		generated_pin = wps_generate_pin();
+		if (wps_generate_pin(&generated_pin) < 0) {
+			wpa_printf(MSG_DEBUG, "P2P: Could not generate PIN");
+			wpas_notify_p2p_provision_discovery(
+				wpa_s, peer, 0 /* response */,
+				P2P_PROV_DISC_INFO_UNAVAILABLE, 0, 0);
+			return;
+		}
 		wpas_prov_disc_local_display(wpa_s, peer, params,
 					     generated_pin);
 	} else if (config_methods & WPS_CONFIG_PUSHBUTTON)
@@ -5366,7 +5378,8 @@ int wpas_p2p_connect(struct wpa_supplicant *wpa_s, const u8 *peer_addr,
 	if (pin)
 		os_strlcpy(wpa_s->p2p_pin, pin, sizeof(wpa_s->p2p_pin));
 	else if (wps_method == WPS_PIN_DISPLAY) {
-		ret = wps_generate_pin();
+		if (wps_generate_pin((unsigned int *) &ret) < 0)
+			return -1;
 		res = os_snprintf(wpa_s->p2p_pin, sizeof(wpa_s->p2p_pin),
 				  "%08d", ret);
 		if (os_snprintf_error(sizeof(wpa_s->p2p_pin), res))

wpa_supplicant/wps_supplicant.c

@@ -1236,7 +1236,10 @@ static int wpas_wps_start_dev_pw(struct wpa_supplicant *wpa_s,
 		os_snprintf(val, sizeof(val), "\"dev_pw_id=%u%s\"",
 			    dev_pw_id, hash);
 	} else {
-		rpin = wps_generate_pin();
+		if (wps_generate_pin(&rpin) < 0) {
+			wpa_printf(MSG_DEBUG, "WPS: Could not generate PIN");
+			return -1;
+		}
 		os_snprintf(val, sizeof(val), "\"pin=%08d dev_pw_id=%u%s\"",
 			    rpin, dev_pw_id, hash);
 	}