DPP: Support retrieving of configurator's private key

To retain configurator information across hostapd/wpa_supplicant
restart, private key need to be maintained to generate a valid pair of
authentication keys (connector, netaccess_key, csign) for new enrollees
in the network.

Add a DPP_CONFIGURATOR_GET_KEY control interface API through which the
private key of an existing configurator can be fetched.

Command format:
DPP_CONFIGURATOR_GET_KEY <configurator_id>

The output from this command can then be used with
"DPP_CONFIGURATOR_ADD key=<hexdump>" to create the same key again.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

hostapd/ctrl_iface.c

@@ -3171,6 +3171,10 @@ static int hostapd_ctrl_iface_receive_process(struct hostapd_data *hapd,
 	} else if (os_strncmp(buf, "DPP_CONFIGURATOR_SIGN ", 22) == 0) {
 		if (hostapd_dpp_configurator_sign(hapd, buf + 22) < 0)
 			reply_len = -1;
+	} else if (os_strncmp(buf, "DPP_CONFIGURATOR_GET_KEY ", 25) == 0) {
+		reply_len = hostapd_dpp_configurator_get_key(hapd,
+							     atoi(buf + 25),
+							     reply, reply_size);
 	} else if (os_strncmp(buf, "DPP_PKEX_ADD ", 13) == 0) {
 		res = hostapd_dpp_pkex_add(hapd, buf + 12);
 		if (res < 0) {

hostapd/hostapd_cli.c

@@ -1436,6 +1436,13 @@ static int hostapd_cli_cmd_dpp_configurator_remove(struct wpa_ctrl *ctrl,
 }
 
 
+static int hostapd_cli_cmd_dpp_configurator_get_key(struct wpa_ctrl *ctrl,
+						    int argc, char *argv[])
+{
+	return hostapd_cli_cmd(ctrl, "DPP_CONFIGURATOR_GET_KEY", 1, argc, argv);
+}
+
+
 static int hostapd_cli_cmd_dpp_pkex_add(struct wpa_ctrl *ctrl, int argc,
 					char *argv[])
 {
@@ -1623,6 +1630,9 @@ static const struct hostapd_cli_cmd hostapd_cli_commands[] = {
 	{ "dpp_configurator_remove", hostapd_cli_cmd_dpp_configurator_remove,
 	  NULL,
 	  "*|<id> = remove DPP configurator" },
+	{ "dpp_configurator_remove", hostapd_cli_cmd_dpp_configurator_get_key,
+	  NULL,
+	  "<id> = Get DPP configurator's private key" },
 	{ "dpp_pkex_add", hostapd_cli_cmd_dpp_pkex_add, NULL,
 	  "add PKEX code" },
 	{ "dpp_pkex_remove", hostapd_cli_cmd_dpp_pkex_remove, NULL,

src/ap/dpp_hostapd.c

@@ -1881,6 +1881,19 @@ int hostapd_dpp_configurator_sign(struct hostapd_data *hapd, const char *cmd)
 }
 
 
+int hostapd_dpp_configurator_get_key(struct hostapd_data *hapd, unsigned int id,
+				     char *buf, size_t buflen)
+{
+	struct dpp_configurator *conf;
+
+	conf = hostapd_dpp_configurator_get_id(hapd, id);
+	if (!conf)
+		return -1;
+
+	return dpp_configurator_get_key(conf, buf, buflen);
+}
+
+
 int hostapd_dpp_pkex_add(struct hostapd_data *hapd, const char *cmd)
 {
 	struct dpp_bootstrap_info *own_bi;

src/ap/dpp_hostapd.h

@@ -30,6 +30,8 @@ void hostapd_dpp_gas_status_handler(struct hostapd_data *hapd, int ok);
 int hostapd_dpp_configurator_add(struct hostapd_data *hapd, const char *cmd);
 int hostapd_dpp_configurator_remove(struct hostapd_data *hapd, const char *id);
 int hostapd_dpp_configurator_sign(struct hostapd_data *hapd, const char *cmd);
+int hostapd_dpp_configurator_get_key(struct hostapd_data *hapd, unsigned int id,
+				     char *buf, size_t buflen);
 int hostapd_dpp_pkex_add(struct hostapd_data *hapd, const char *cmd);
 int hostapd_dpp_pkex_remove(struct hostapd_data *hapd, const char *id);
 void hostapd_dpp_stop(struct hostapd_data *hapd);

src/common/dpp.c

@@ -5510,6 +5510,30 @@ void dpp_configurator_free(struct dpp_configurator *conf)
 }
 
 
+int dpp_configurator_get_key(const struct dpp_configurator *conf, char *buf,
+			     size_t buflen)
+{
+	EC_KEY *eckey;
+	int key_len, ret = -1;
+	unsigned char *key = NULL;
+
+	if (!conf->csign)
+		return -1;
+
+	eckey = EVP_PKEY_get1_EC_KEY(conf->csign);
+	if (!eckey)
+		return -1;
+
+	key_len = i2d_ECPrivateKey(eckey, &key);
+	if (key_len > 0)
+		ret = wpa_snprintf_hex(buf, buflen, key, key_len);
+
+	EC_KEY_free(eckey);
+	OPENSSL_free(key);
+	return ret;
+}
+
+
 struct dpp_configurator *
 dpp_keygen_configurator(const char *curve, const u8 *privkey,
 			size_t privkey_len)

src/common/dpp.h

@@ -394,6 +394,8 @@ const u8 * dpp_get_attr(const u8 *buf, size_t len, u16 req_id, u16 *ret_len);
 int dpp_check_attrs(const u8 *buf, size_t len);
 int dpp_key_expired(const char *timestamp, os_time_t *expiry);
 const char * dpp_akm_str(enum dpp_akm akm);
+int dpp_configurator_get_key(const struct dpp_configurator *conf, char *buf,
+			     size_t buflen);
 void dpp_configurator_free(struct dpp_configurator *conf);
 struct dpp_configurator *
 dpp_keygen_configurator(const char *curve, const u8 *privkey,

wpa_supplicant/ctrl_iface.c

@@ -10576,6 +10576,9 @@ char * wpa_supplicant_ctrl_iface_process(struct wpa_supplicant *wpa_s,
 	} else if (os_strncmp(buf, "DPP_CONFIGURATOR_SIGN ", 22) == 0) {
 		if (wpas_dpp_configurator_sign(wpa_s, buf + 22) < 0)
 			reply_len = -1;
+	} else if (os_strncmp(buf, "DPP_CONFIGURATOR_GET_KEY ", 25) == 0) {
+		reply_len = wpas_dpp_configurator_get_key(wpa_s, atoi(buf + 25),
+							  reply, reply_size);
 	} else if (os_strncmp(buf, "DPP_PKEX_ADD ", 13) == 0) {
 		int res;
 

wpa_supplicant/dpp_supplicant.c

@@ -2275,6 +2275,19 @@ int wpas_dpp_configurator_sign(struct wpa_supplicant *wpa_s, const char *cmd)
 }
 
 
+int wpas_dpp_configurator_get_key(struct wpa_supplicant *wpa_s, unsigned int id,
+				  char *buf, size_t buflen)
+{
+	struct dpp_configurator *conf;
+
+	conf = dpp_configurator_get_id(wpa_s, id);
+	if (!conf)
+		return -1;
+
+	return dpp_configurator_get_key(conf, buf, buflen);
+}
+
+
 static void
 wpas_dpp_tx_introduction_status(struct wpa_supplicant *wpa_s,
 				unsigned int freq, const u8 *dst,

wpa_supplicant/dpp_supplicant.h

@@ -28,6 +28,8 @@ void wpas_dpp_rx_action(struct wpa_supplicant *wpa_s, const u8 *src,
 int wpas_dpp_configurator_add(struct wpa_supplicant *wpa_s, const char *cmd);
 int wpas_dpp_configurator_remove(struct wpa_supplicant *wpa_s, const char *id);
 int wpas_dpp_configurator_sign(struct wpa_supplicant *wpa_s, const char *cmd);
+int wpas_dpp_configurator_get_key(struct wpa_supplicant *wpa_s, unsigned int id,
+				  char *buf, size_t buflen);
 int wpas_dpp_pkex_add(struct wpa_supplicant *wpa_s, const char *cmd);
 int wpas_dpp_pkex_remove(struct wpa_supplicant *wpa_s, const char *id);
 void wpas_dpp_stop(struct wpa_supplicant *wpa_s);

wpa_supplicant/wpa_cli.c

@@ -2948,6 +2948,13 @@ static int wpa_cli_cmd_dpp_configurator_remove(struct wpa_ctrl *ctrl, int argc,
 }
 
 
+static int wpa_cli_cmd_dpp_configurator_get_key(struct wpa_ctrl *ctrl, int argc,
+						char *argv[])
+{
+	return wpa_cli_cmd(ctrl, "DPP_CONFIGURATOR_GET_KEY", 1, argc, argv);
+}
+
+
 static int wpa_cli_cmd_dpp_pkex_add(struct wpa_ctrl *ctrl, int argc,
 				    char *argv[])
 {
@@ -3604,6 +3611,9 @@ static const struct wpa_cli_cmd wpa_cli_commands[] = {
 	{ "dpp_configurator_remove", wpa_cli_cmd_dpp_configurator_remove, NULL,
 	  cli_cmd_flag_none,
 	  "*|<id> = remove DPP configurator" },
+	{ "dpp_configurator_get_key", wpa_cli_cmd_dpp_configurator_get_key,
+	  NULL, cli_cmd_flag_none,
+	  "<id> = Get DPP configurator's private key" },
 	{ "dpp_pkex_add", wpa_cli_cmd_dpp_pkex_add, NULL,
 	  cli_cmd_flag_sensitive,
 	  "add PKEX code" },