FT: Allow PMK-R0 and PMK-R1 for FT-PSK to be generated locally

Station should be able to connect initially without ft_pmk_cache filled,
so the target AP has the PSK available and thus the same information as
the origin AP. Therefore neither caching nor communication between the
APs with respect to PMK-R0 or PMK-R1 or VLANs is required if the target
AP derives the required PMKs locally.

This patch introduces the generation of the required PMKs locally for
FT-PSK. Additionally, PMK-R0 is not stored (and thus pushed) for FT-PSK.

So for FT-PSK networks, no configuration of inter-AP communication is
needed anymore when using ft_psk_generate_local=1 configuration. The
default behavior (ft_psk_generate_local=0) remains to use the pull/push
protocol.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>

hostapd/config_file.c

@@ -2559,6 +2559,8 @@ static int hostapd_config_fill(struct hostapd_config *conf,
 		bss->pmk_r1_push = atoi(pos);
 	} else if (os_strcmp(buf, "ft_over_ds") == 0) {
 		bss->ft_over_ds = atoi(pos);
+	} else if (os_strcmp(buf, "ft_psk_generate_local") == 0) {
+		bss->ft_psk_generate_local = atoi(pos);
 #endif /* CONFIG_IEEE80211R */
 #ifndef CONFIG_NO_CTRL_IFACE
 	} else if (os_strcmp(buf, "ctrl_interface") == 0) {

hostapd/hostapd.conf

@@ -1326,6 +1326,14 @@ own_ip_addr=127.0.0.1
 # 1 = FT-over-DS enabled (default)
 #ft_over_ds=1
 
+# Whether to generate FT response locally for PSK networks
+# This avoids use of PMK-R1 push/pull from other APs with FT-PSK networks as
+# the required information (PSK and other session data) is already locally
+# available.
+# 0 = disabled (default)
+# 1 = enabled
+#ft_psk_generate_local=0
+
 ##### Neighbor table ##########################################################
 # Maximum number of entries kept in AP table (either for neigbor table or for
 # detecting Overlapping Legacy BSS Condition). The oldest entry will be

src/ap/ap_config.h

@@ -339,6 +339,7 @@ struct hostapd_bss_config {
 	struct ft_remote_r1kh *r1kh_list;
 	int pmk_r1_push;
 	int ft_over_ds;
+	int ft_psk_generate_local;
 #endif /* CONFIG_IEEE80211R */
 
 	char *ctrl_interface; /* directory for UNIX domain sockets */

src/ap/wpa_auth.h

@@ -170,6 +170,7 @@ struct wpa_auth_config {
 	struct ft_remote_r1kh *r1kh_list;
 	int pmk_r1_push;
 	int ft_over_ds;
+	int ft_psk_generate_local;
 #endif /* CONFIG_IEEE80211R */
 	int disable_gtk;
 	int ap_mlme;

src/ap/wpa_auth_ft.c

@@ -51,6 +51,17 @@ static int wpa_ft_action_send(struct wpa_authenticator *wpa_auth,
 }
 
 
+static const u8 * wpa_ft_get_psk(struct wpa_authenticator *wpa_auth,
+				 const u8 *addr, const u8 *p2p_dev_addr,
+				 const u8 *prev_psk)
+{
+	if (wpa_auth->cb.get_psk == NULL)
+		return NULL;
+	return wpa_auth->cb.get_psk(wpa_auth->cb.ctx, addr, p2p_dev_addr,
+				    prev_psk);
+}
+
+
 static struct wpa_state_machine *
 wpa_ft_add_sta(struct wpa_authenticator *wpa_auth, const u8 *sta_addr)
 {
@@ -373,6 +384,7 @@ int wpa_auth_derive_ptk_ft(struct wpa_state_machine *sm, const u8 *pmk,
 	const u8 *r1kh = sm->wpa_auth->conf.r1_key_holder;
 	const u8 *ssid = sm->wpa_auth->conf.ssid;
 	size_t ssid_len = sm->wpa_auth->conf.ssid_len;
+	int psk_local = sm->wpa_auth->conf.ft_psk_generate_local;
 
 	if (sm->xxkey_len == 0) {
 		wpa_printf(MSG_DEBUG, "FT: XXKey not available for key "
@@ -384,16 +396,18 @@ int wpa_auth_derive_ptk_ft(struct wpa_state_machine *sm, const u8 *pmk,
 			  r0kh, r0kh_len, sm->addr, pmk_r0, pmk_r0_name);
 	wpa_hexdump_key(MSG_DEBUG, "FT: PMK-R0", pmk_r0, PMK_LEN);
 	wpa_hexdump(MSG_DEBUG, "FT: PMKR0Name", pmk_r0_name, WPA_PMK_NAME_LEN);
-	wpa_ft_store_pmk_r0(sm->wpa_auth, sm->addr, pmk_r0, pmk_r0_name,
-			    sm->pairwise);
+	if (!psk_local || !wpa_key_mgmt_ft_psk(sm->wpa_key_mgmt))
+		wpa_ft_store_pmk_r0(sm->wpa_auth, sm->addr, pmk_r0, pmk_r0_name,
+				    sm->pairwise);
 
 	wpa_derive_pmk_r1(pmk_r0, pmk_r0_name, r1kh, sm->addr,
 			  pmk_r1, sm->pmk_r1_name);
 	wpa_hexdump_key(MSG_DEBUG, "FT: PMK-R1", pmk_r1, PMK_LEN);
 	wpa_hexdump(MSG_DEBUG, "FT: PMKR1Name", sm->pmk_r1_name,
 		    WPA_PMK_NAME_LEN);
-	wpa_ft_store_pmk_r1(sm->wpa_auth, sm->addr, pmk_r1, sm->pmk_r1_name,
-			    sm->pairwise);
+	if (!psk_local || !wpa_key_mgmt_ft_psk(sm->wpa_key_mgmt))
+		wpa_ft_store_pmk_r1(sm->wpa_auth, sm->addr, pmk_r1,
+				    sm->pmk_r1_name, sm->pairwise);
 
 	return wpa_pmk_r1_to_ptk(pmk_r1, sm->SNonce, sm->ANonce, sm->addr,
 				 sm->wpa_auth->addr, sm->pmk_r1_name,
@@ -795,6 +809,89 @@ void wpa_ft_install_ptk(struct wpa_state_machine *sm)
 }
 
 
+/* Derive PMK-R1 from PSK, check all available PSK */
+static int wpa_ft_psk_pmk_r1(struct wpa_state_machine *sm,
+			     const u8 *req_pmk_r1_name,
+			     u8 *out_pmk_r1, int *out_pairwise)
+{
+	const u8 *pmk = NULL;
+	u8 pmk_r0[PMK_LEN], pmk_r0_name[WPA_PMK_NAME_LEN];
+	u8 pmk_r1[PMK_LEN], pmk_r1_name[WPA_PMK_NAME_LEN];
+	struct wpa_authenticator *wpa_auth = sm->wpa_auth;
+	const u8 *mdid = wpa_auth->conf.mobility_domain;
+	const u8 *r0kh = sm->r0kh_id;
+	size_t r0kh_len = sm->r0kh_id_len;
+	const u8 *r1kh = wpa_auth->conf.r1_key_holder;
+	const u8 *ssid = wpa_auth->conf.ssid;
+	size_t ssid_len = wpa_auth->conf.ssid_len;
+	int pairwise;
+
+	pairwise = sm->pairwise;
+
+	for (;;) {
+		pmk = wpa_ft_get_psk(wpa_auth, sm->addr, sm->p2p_dev_addr,
+				     pmk);
+		if (pmk == NULL)
+			break;
+
+		wpa_derive_pmk_r0(pmk, PMK_LEN, ssid, ssid_len, mdid, r0kh,
+				  r0kh_len, sm->addr, pmk_r0, pmk_r0_name);
+		wpa_derive_pmk_r1(pmk_r0, pmk_r0_name, r1kh, sm->addr,
+				  pmk_r1, pmk_r1_name);
+
+		if (os_memcmp_const(pmk_r1_name, req_pmk_r1_name,
+				    WPA_PMK_NAME_LEN) != 0)
+			continue;
+
+		/* We found a PSK that matches the requested pmk_r1_name */
+		wpa_printf(MSG_DEBUG,
+			   "FT: Found PSK to generate PMK-R1 locally");
+		os_memcpy(out_pmk_r1, pmk_r1, PMK_LEN);
+		if (out_pairwise)
+			*out_pairwise = pairwise;
+		return 0;
+	}
+
+	wpa_printf(MSG_DEBUG,
+		   "FT: Did not find PSK to generate PMK-R1 locally");
+	return -1;
+}
+
+
+/* Detect the configuration the station asked for.
+ * Required to detect FT-PSK and pairwise cipher.
+ */
+static int wpa_ft_set_key_mgmt(struct wpa_state_machine *sm,
+			       struct wpa_ft_ies *parse)
+{
+	int key_mgmt, ciphers;
+
+	if (sm->wpa_key_mgmt)
+		return 0;
+
+	key_mgmt = parse->key_mgmt & sm->wpa_auth->conf.wpa_key_mgmt;
+	if (!key_mgmt) {
+		wpa_printf(MSG_DEBUG, "FT: Invalid key mgmt (0x%x) from "
+			   MACSTR, parse->key_mgmt, MAC2STR(sm->addr));
+		return -1;
+	}
+	if (key_mgmt & WPA_KEY_MGMT_FT_IEEE8021X)
+		sm->wpa_key_mgmt = WPA_KEY_MGMT_FT_IEEE8021X;
+	else if (key_mgmt & WPA_KEY_MGMT_FT_PSK)
+		sm->wpa_key_mgmt = WPA_KEY_MGMT_FT_PSK;
+	ciphers = parse->pairwise_cipher & sm->wpa_auth->conf.rsn_pairwise;
+	if (!ciphers) {
+		wpa_printf(MSG_DEBUG, "FT: Invalid pairwise cipher (0x%x) from "
+			   MACSTR,
+			   parse->pairwise_cipher, MAC2STR(sm->addr));
+		return -1;
+	}
+	sm->pairwise = wpa_pick_pairwise_cipher(ciphers, 0);
+
+	return 0;
+}
+
+
 static int wpa_ft_process_auth_req(struct wpa_state_machine *sm,
 				   const u8 *ies, size_t ies_len,
 				   u8 **resp_ies, size_t *resp_ies_len)
@@ -856,6 +953,9 @@ static int wpa_ft_process_auth_req(struct wpa_state_machine *sm,
 		return WLAN_STATUS_INVALID_PMKID;
 	}
 
+	if (wpa_ft_set_key_mgmt(sm, &parse) < 0)
+		return WLAN_STATUS_UNSPECIFIED_FAILURE;
+
 	wpa_hexdump(MSG_DEBUG, "FT: Requested PMKR0Name",
 		    parse.rsn_pmkid, WPA_PMK_NAME_LEN);
 	wpa_derive_pmk_r1_name(parse.rsn_pmkid,
@@ -864,8 +964,12 @@ static int wpa_ft_process_auth_req(struct wpa_state_machine *sm,
 	wpa_hexdump(MSG_DEBUG, "FT: Derived requested PMKR1Name",
 		    pmk_r1_name, WPA_PMK_NAME_LEN);
 
-	if (wpa_ft_fetch_pmk_r1(sm->wpa_auth, sm->addr, pmk_r1_name, pmk_r1,
-		    &pairwise) < 0) {
+	if (conf->ft_psk_generate_local &&
+	    wpa_key_mgmt_ft_psk(sm->wpa_key_mgmt)) {
+		if (wpa_ft_psk_pmk_r1(sm, pmk_r1_name, pmk_r1, &pairwise) < 0)
+			return WLAN_STATUS_INVALID_PMKID;
+	} else if (wpa_ft_fetch_pmk_r1(sm->wpa_auth, sm->addr, pmk_r1_name,
+				       pmk_r1, &pairwise) < 0) {
 		if (wpa_ft_pull_pmk_r1(sm, ies, ies_len, parse.rsn_pmkid) < 0) {
 			wpa_printf(MSG_DEBUG, "FT: Did not have matching "
 				   "PMK-R1 and unknown R0KH-ID");

src/ap/wpa_auth_glue.c

@@ -73,6 +73,7 @@ static void hostapd_wpa_auth_conf(struct hostapd_bss_config *conf,
 	wconf->r1kh_list = conf->r1kh_list;
 	wconf->pmk_r1_push = conf->pmk_r1_push;
 	wconf->ft_over_ds = conf->ft_over_ds;
+	wconf->ft_psk_generate_local = conf->ft_psk_generate_local;
 #endif /* CONFIG_IEEE80211R */
 #ifdef CONFIG_HS20
 	wconf->disable_gtk = conf->disable_dgaf;

src/common/defs.h

@@ -79,6 +79,11 @@ static inline int wpa_key_mgmt_ft(int akm)
 			 WPA_KEY_MGMT_FT_SAE));
 }
 
+static inline int wpa_key_mgmt_ft_psk(int akm)
+{
+	return !!(akm & WPA_KEY_MGMT_FT_PSK);
+}
+
 static inline int wpa_key_mgmt_sae(int akm)
 {
 	return !!(akm & (WPA_KEY_MGMT_SAE |

src/common/wpa_common.c

@@ -376,6 +376,8 @@ int wpa_ft_parse_ies(const u8 *ies, size_t ies_len,
 			}
 			if (data.num_pmkid == 1 && data.pmkid)
 				parse->rsn_pmkid = data.pmkid;
+			parse->key_mgmt = data.key_mgmt;
+			parse->pairwise_cipher = data.pairwise_cipher;
 			break;
 		case WLAN_EID_MOBILITY_DOMAIN:
 			if (len < sizeof(struct rsn_mdie))

src/common/wpa_common.h

@@ -430,6 +430,8 @@ struct wpa_ft_ies {
 	size_t igtk_len;
 	const u8 *ric;
 	size_t ric_len;
+	int key_mgmt;
+	int pairwise_cipher;
 };
 
 int wpa_ft_parse_ies(const u8 *ies, size_t ies_len, struct wpa_ft_ies *parse);