FT: Derive PMK-R1 locally if requested PMKR0Name is found

Derive PMK-R1 locally if the derived PMKR1Name is not found from the
local cache, but the request is for a key that was originally generated
locally (R0KH-ID matches) and the PMKR0Name is found in the local cache.
This was apparently not hit in the previously used FT sequences, but
this is useful to have available if a PMK-R1 entry is dropped from the
local cache before PMK-R0.

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

src/ap/wpa_auth_ft.c

@@ -2055,6 +2055,43 @@ static int wpa_ft_set_key_mgmt(struct wpa_state_machine *sm,
 }
 
 
+static int wpa_ft_local_derive_pmk_r1(struct wpa_authenticator *wpa_auth,
+				      struct wpa_state_machine *sm,
+				      const u8 *r0kh_id, size_t r0kh_id_len,
+				      const u8 *req_pmk_r0_name,
+				      const u8 *req_pmk_r1_name,
+				      u8 *out_pmk_r1, int *out_pairwise)
+{
+	struct wpa_auth_config *conf = &wpa_auth->conf;
+	const struct wpa_ft_pmk_r0_sa *r0;
+	u8 pmk_r1_name[WPA_PMK_NAME_LEN];
+
+	if (conf->r0_key_holder_len != r0kh_id_len ||
+	    os_memcmp(conf->r0_key_holder, r0kh_id, conf->r0_key_holder_len) !=
+	    0)
+		return -1; /* not our R0KH-ID */
+
+	wpa_printf(MSG_DEBUG, "FT: STA R0KH-ID matching local configuration");
+	if (wpa_ft_fetch_pmk_r0(sm->wpa_auth, sm->addr, req_pmk_r0_name, &r0) <
+	    0)
+		return -1; /* no matching PMKR0Name in local cache */
+
+	wpa_printf(MSG_DEBUG, "FT: Requested PMKR0Name found in local cache");
+
+	if (wpa_derive_pmk_r1(r0->pmk_r0, r0->pmk_r0_name, conf->r1_key_holder,
+			      sm->addr, out_pmk_r1, pmk_r1_name) < 0)
+		return -1;
+	wpa_hexdump_key(MSG_DEBUG, "FT: PMK-R1", out_pmk_r1, PMK_LEN);
+	wpa_hexdump(MSG_DEBUG, "FT: PMKR1Name", pmk_r1_name, WPA_PMK_NAME_LEN);
+
+	wpa_ft_store_pmk_r1(wpa_auth, sm->addr, out_pmk_r1, pmk_r1_name,
+			    sm->pairwise);
+
+	*out_pairwise = sm->pairwise;
+	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)
@@ -2132,8 +2169,22 @@ static int wpa_ft_process_auth_req(struct wpa_state_machine *sm,
 	    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;
+		wpa_printf(MSG_DEBUG,
+			   "FT: Generated PMK-R1 for FT-PSK locally");
 	} else if (wpa_ft_fetch_pmk_r1(sm->wpa_auth, sm->addr, pmk_r1_name,
 				       pmk_r1, &pairwise) < 0) {
+		wpa_printf(MSG_DEBUG,
+			   "FT: No PMK-R1 available in local cache for the requested PMKR1Name");
+		if (wpa_ft_local_derive_pmk_r1(sm->wpa_auth, sm,
+					       parse.r0kh_id, parse.r0kh_id_len,
+					       parse.rsn_pmkid,
+					       pmk_r1_name, pmk_r1, &pairwise)
+		    == 0) {
+			wpa_printf(MSG_DEBUG,
+				   "FT: Generated PMK-R1 based on local PMK-R0");
+			goto pmk_r1_derived;
+		}
+
 		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 either unknown or blocked R0KH-ID or NAK from R0KH");
@@ -2141,8 +2192,11 @@ static int wpa_ft_process_auth_req(struct wpa_state_machine *sm,
 		}
 
 		return -1; /* Status pending */
+	} else {
+		wpa_printf(MSG_DEBUG, "FT: Found PMKR1Name from local cache");
 	}
 
+pmk_r1_derived:
 	wpa_hexdump_key(MSG_DEBUG, "FT: Selected PMK-R1", pmk_r1, PMK_LEN);
 	sm->pmk_r1_name_valid = 1;
 	os_memcpy(sm->pmk_r1_name, pmk_r1_name, WPA_PMK_NAME_LEN);