WPS: Make it possible to use PSKs loaded from the PSK file

By default, when configuration file set wpa_psk_file, hostapd generated
a random PSK for each Enrollee provisioned using WPS and appended that
PSK to wpa_psk_file.

Changes that behavior by adding a new step. WPS will first try to use a
PSK from wpa_psk_file. It will only try PSKs with wps=1 tag.
Additionally it'll try to match enrollee's MAC address (if provided). If
it fails to find an appropriate PSK, it falls back to generating a new
PSK.

Signed-off-by: Tomasz Jankowski <tomasz.jankowski@plume.com>

hostapd/hostapd.wpa_psk

@@ -7,9 +7,15 @@
 # keyid=<keyid_string>
 # An optional VLAN ID can be specified by prefixing the line with
 # vlanid=<VLAN ID>.
+# An optional WPS tag can be added by prefixing the line with
+# wps=<0/1> (default: 0). Any matching entry with that tag will be used when
+# generating a PSK for a WPS Enrollee instead of generating a new random
+# per-Enrollee PSK.
 00:00:00:00:00:00 secret passphrase
 00:11:22:33:44:55 another passphrase
 00:22:33:44:55:66 0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
 keyid=example_id 00:11:22:33:44:77 passphrase with keyid
 vlanid=3 00:00:00:00:00:00 passphrase with vlanid
+wps=1 00:00:00:00:00:00 passphrase for WPS
+wps=1 11:22:33:44:55:00 dev-specific passphrase for WPS
 00:00:00:00:00:00 another passphrase for all STAs

src/ap/ap_config.c

@@ -301,6 +301,7 @@ static int hostapd_config_read_wpa_psk(const char *fname,
 
 	while (fgets(buf, sizeof(buf), f)) {
 		int vlan_id = 0;
+		int wps = 0;
 
 		line++;
 
@@ -331,6 +332,8 @@ static int hostapd_config_read_wpa_psk(const char *fname,
 				value = "";
 			if (!os_strcmp(name, "keyid")) {
 				keyid = value;
+			} else if (!os_strcmp(name, "wps")) {
+				wps = atoi(value);
 			} else if (!os_strcmp(name, "vlanid")) {
 				vlan_id = atoi(value);
 			} else {
@@ -406,6 +409,8 @@ static int hostapd_config_read_wpa_psk(const char *fname,
 			}
 		}
 
+		psk->wps = wps;
+
 		psk->next = ssid->wpa_psk;
 		ssid->wpa_psk = psk;
 	}

src/ap/ap_config.h

@@ -152,6 +152,7 @@ struct hostapd_wpa_psk {
 	struct hostapd_wpa_psk *next;
 	int group;
 	char keyid[KEYID_LEN];
+	int wps;
 	u8 psk[PMK_LEN];
 	u8 addr[ETH_ALEN];
 	u8 p2p_dev_addr[ETH_ALEN];

src/ap/wps_hostapd.c

@@ -269,6 +269,44 @@ static void hostapd_wps_enrollee_seen_cb(void *ctx, const u8 *addr,
 }
 
 
+static int hostapd_wps_lookup_pskfile_cb(void *ctx, const u8 *mac_addr,
+					 const u8 **psk)
+{
+	const struct hostapd_data *hapd = ctx;
+	const struct hostapd_wpa_psk *wpa_psk;
+	const u8 *any_psk = NULL;
+	const u8 *dev_psk = NULL;
+
+	for (wpa_psk = hapd->conf->ssid.wpa_psk; wpa_psk;
+	     wpa_psk = wpa_psk->next) {
+		if (!wpa_psk->wps)
+			continue;
+
+		if (!any_psk && is_zero_ether_addr(wpa_psk->addr))
+			any_psk = wpa_psk->psk;
+
+		if (mac_addr && !dev_psk &&
+		    os_memcmp(mac_addr, wpa_psk->addr, ETH_ALEN) == 0) {
+			dev_psk = wpa_psk->psk;
+			break;
+		}
+	}
+
+	if (dev_psk) {
+		*psk = dev_psk;
+	} else if (any_psk) {
+		*psk = any_psk;
+	} else {
+		*psk = NULL;
+		wpa_printf(MSG_DEBUG,
+			   "WPS: No appropriate PSK in wpa_psk_file");
+		return 0;
+	}
+
+	return 1;
+}
+
+
 static void wps_reload_config(void *eloop_data, void *user_ctx)
 {
 	struct hostapd_iface *iface = eloop_data;
@@ -1213,6 +1251,7 @@ int hostapd_init_wps(struct hostapd_data *hapd,
 	cfg.pin_needed_cb = hostapd_wps_pin_needed_cb;
 	cfg.reg_success_cb = hostapd_wps_reg_success_cb;
 	cfg.enrollee_seen_cb = hostapd_wps_enrollee_seen_cb;
+	cfg.lookup_pskfile_cb = hostapd_wps_lookup_pskfile_cb;
 	cfg.cb_ctx = hapd;
 	cfg.skip_cred_build = conf->skip_cred_build;
 	cfg.extra_cred = conf->extra_cred;

src/wps/wps.h

@@ -344,6 +344,14 @@ struct wps_registrar_config {
 				 u16 dev_password_id, u8 request_type,
 				 const char *dev_name);
 
+	/**
+	 * lookup_pskfile_cb - Callback for searching for PSK in wpa_psk_file
+	 * @ctx: Higher layer context data (cb_ctx)
+	 * @addr: Enrollee's MAC address
+	 * @psk: Pointer to found PSK (output arg)
+	 */
+	int (*lookup_pskfile_cb)(void *ctx, const u8 *mac_addr, const u8 **psk);
+
 	/**
 	 * cb_ctx: Higher layer context data for Registrar callbacks
 	 */

src/wps/wps_registrar.c

@@ -160,6 +160,7 @@ struct wps_registrar {
 				 const u8 *pri_dev_type, u16 config_methods,
 				 u16 dev_password_id, u8 request_type,
 				 const char *dev_name);
+	int (*lookup_pskfile_cb)(void *ctx, const u8 *mac_addr, const u8 **psk);
 	void *cb_ctx;
 
 	struct dl_list pins;
@@ -682,6 +683,7 @@ wps_registrar_init(struct wps_context *wps,
 	reg->reg_success_cb = cfg->reg_success_cb;
 	reg->set_sel_reg_cb = cfg->set_sel_reg_cb;
 	reg->enrollee_seen_cb = cfg->enrollee_seen_cb;
+	reg->lookup_pskfile_cb = cfg->lookup_pskfile_cb;
 	reg->cb_ctx = cfg->cb_ctx;
 	reg->skip_cred_build = cfg->skip_cred_build;
 	if (cfg->extra_cred) {
@@ -1291,6 +1293,15 @@ static void wps_cb_set_sel_reg(struct wps_registrar *reg)
 }
 
 
+static int wps_cp_lookup_pskfile(struct wps_registrar *reg, const u8 *mac_addr,
+				 const u8 **psk)
+{
+	if (!reg->lookup_pskfile_cb)
+		return 0;
+	return reg->lookup_pskfile_cb(reg->cb_ctx, mac_addr, psk);
+}
+
+
 static int wps_set_ie(struct wps_registrar *reg)
 {
 	struct wpabuf *beacon;
@@ -1645,6 +1656,8 @@ int wps_build_cred(struct wps_data *wps, struct wpabuf *msg)
 {
 	struct wpabuf *cred;
 	struct wps_registrar *reg = wps->wps->registrar;
+	const u8 *pskfile_psk;
+	char hex[65];
 
 	if (wps->wps->registrar->skip_cred_build)
 		goto skip_cred_build;
@@ -1760,9 +1773,14 @@ int wps_build_cred(struct wps_data *wps, struct wpabuf *msg)
 				      wps->new_psk, wps->new_psk_len);
 		os_memcpy(wps->cred.key, wps->new_psk, wps->new_psk_len);
 		wps->cred.key_len = wps->new_psk_len;
+	} else if (wps_cp_lookup_pskfile(reg, wps->mac_addr_e, &pskfile_psk)) {
+		wpa_hexdump_key(MSG_DEBUG, "WPS: Use PSK from wpa_psk_file",
+				pskfile_psk, PMK_LEN);
+		wpa_snprintf_hex(hex, sizeof(hex), pskfile_psk, PMK_LEN);
+		os_memcpy(wps->cred.key, hex, PMK_LEN * 2);
+		wps->cred.key_len = PMK_LEN * 2;
 	} else if (!wps->wps->registrar->force_per_enrollee_psk &&
 		   wps->use_psk_key && wps->wps->psk_set) {
-		char hex[65];
 		wpa_printf(MSG_DEBUG, "WPS: Use PSK format for Network Key");
 		wpa_snprintf_hex(hex, sizeof(hex), wps->wps->psk, PMK_LEN);
 		os_memcpy(wps->cred.key, hex, PMK_LEN * 2);
@@ -1773,7 +1791,6 @@ int wps_build_cred(struct wps_data *wps, struct wpabuf *msg)
 			  wps->wps->network_key_len);
 		wps->cred.key_len = wps->wps->network_key_len;
 	} else if (wps->auth_type & (WPS_AUTH_WPAPSK | WPS_AUTH_WPA2PSK)) {
-		char hex[65];
 		/* Generate a random per-device PSK */
 		os_free(wps->new_psk);
 		wps->new_psk_len = PMK_LEN;