[PATCH 1/5] PASN: Derive KDK only when required

[Ilan Peer]

When a PTK derivation is done as part of PASN authentication
flow, a KDK derivation should be done iff higher layer protocol
is supported by both parties.

Fix the code accordingly, so KDK would be derived iff both sides
support Secure LTF.

Signed-off-by: Ilan Peer <ilan.peer at intel.com>
---
 src/ap/ieee802_11.c               | 15 +++++++++++++--
 src/ap/sta_info.h                 |  1 +
 wpa_supplicant/pasn_supplicant.c  | 15 ++++++++++++++-
 wpa_supplicant/wpa_supplicant_i.h |  1 +
 4 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/ap/ieee802_11.c b/src/ap/ieee802_11.c
index 877d03e3aa..e4dd2b4b3f 100644
--- a/src/ap/ieee802_11.c
+++ b/src/ap/ieee802_11.c
@@ -2646,7 +2646,7 @@ static void pasn_fils_auth_resp(struct hostapd_data *hapd,
 			      wpabuf_head(pasn->secret),
 			      wpabuf_len(pasn->secret),
 			      &sta->pasn->ptk, sta->pasn->akmp,
-			      sta->pasn->cipher, WPA_KDK_MAX_LEN);
+			      sta->pasn->cipher, sta->pasn->kdk_len);
 	if (ret) {
 		wpa_printf(MSG_DEBUG, "PASN: FILS: Failed to derive PTK");
 		goto fail;
@@ -2883,7 +2883,7 @@ pasn_derive_keys(struct hostapd_data *hapd, struct sta_info *sta,
 	ret = pasn_pmk_to_ptk(pmk, pmk_len, sta->addr, hapd->own_addr,
 			      wpabuf_head(secret), wpabuf_len(secret),
 			      &sta->pasn->ptk, sta->pasn->akmp,
-			      sta->pasn->cipher, WPA_KDK_MAX_LEN);
+			      sta->pasn->cipher, sta->pasn->kdk_len);
 	if (ret) {
 		wpa_printf(MSG_DEBUG, "PASN: Failed to derive PTK");
 		return -1;
@@ -3151,6 +3151,17 @@ static void handle_auth_pasn_1(struct hostapd_data *hapd, struct sta_info *sta,
 	sta->pasn->akmp = rsn_data.key_mgmt;
 	sta->pasn->cipher = rsn_data.pairwise_cipher;
 
+	if (hapd->conf->force_kdk_derivation ||
+	    ((hapd->iface->drv_flags2 & WPA_DRIVER_FLAGS2_SEC_LTF) &&
+	     elems.rsnxe && elems.rsnxe_len >= 2 &&
+	     (WPA_GET_LE16(elems.rsnxe) & BIT(WLAN_RSNX_CAPAB_SECURE_LTF)))) {
+		sta->pasn->kdk_len = WPA_KDK_MAX_LEN;
+	} else {
+		sta->pasn->kdk_len = 0;
+	}
+
+	wpa_printf(MSG_DEBUG, "PASN: kdk_len=%zu", sta->pasn->kdk_len);
+
 	if (!elems.pasn_params || !elems.pasn_params_len) {
 		wpa_printf(MSG_DEBUG,
 			   "PASN: No PASN Parameters element found");
diff --git a/src/ap/sta_info.h b/src/ap/sta_info.h
index efa48e7e3d..27e72f9a01 100644
--- a/src/ap/sta_info.h
+++ b/src/ap/sta_info.h
@@ -88,6 +88,7 @@ struct pasn_data {
 	u16 group;
 	u8 trans_seq;
 	u8 wrapped_data_format;
+	size_t kdk_len;
 
 	u8 hash[SHA384_MAC_LEN];
 	struct wpa_ptk ptk;
diff --git a/wpa_supplicant/pasn_supplicant.c b/wpa_supplicant/pasn_supplicant.c
index 53ba21c5a8..c0db686dfe 100644
--- a/wpa_supplicant/pasn_supplicant.c
+++ b/wpa_supplicant/pasn_supplicant.c
@@ -1052,6 +1052,19 @@ static int wpas_pasn_start(struct wpa_supplicant *wpa_s, const u8 *bssid,
 	pasn->cipher = cipher;
 	pasn->group = group;
 	pasn->freq = freq;
+
+	if (wpa_s->conf->force_kdk_derivation ||
+	    (wpa_s->drv_flags2 & WPA_DRIVER_FLAGS2_SEC_LTF &&
+	     beacon_rsnxe && beacon_rsnxe_len >= 4 &&
+	     (WPA_GET_LE16(beacon_rsnxe + 2) &
+	      BIT(WLAN_RSNX_CAPAB_SECURE_LTF)))) {
+		pasn->kdk_len = WPA_KDK_MAX_LEN;
+	} else {
+		pasn->kdk_len = 0;
+	}
+
+	wpa_printf(MSG_DEBUG, "PASN: kdk_len=%zu", pasn->kdk_len);
+
 	os_memcpy(pasn->bssid, bssid, ETH_ALEN);
 
 	wpa_printf(MSG_DEBUG,
@@ -1480,7 +1493,7 @@ int wpas_pasn_auth_rx(struct wpa_supplicant *wpa_s,
 			      wpa_s->own_addr, pasn->bssid,
 			      wpabuf_head(secret), wpabuf_len(secret),
 			      &pasn->ptk, pasn->akmp, pasn->cipher,
-			      WPA_KDK_MAX_LEN);
+			      pasn->kdk_len);
 	if (ret) {
 		wpa_printf(MSG_DEBUG, "PASN: Failed to derive PTK");
 		goto fail;
diff --git a/wpa_supplicant/wpa_supplicant_i.h b/wpa_supplicant/wpa_supplicant_i.h
index 8813ddb710..49007cfc2e 100644
--- a/wpa_supplicant/wpa_supplicant_i.h
+++ b/wpa_supplicant/wpa_supplicant_i.h
@@ -539,6 +539,7 @@ struct wpas_pasn {
 	int cipher;
 	u16 group;
 	int freq;
+	size_t kdk_len;
 
 	u8 trans_seq;
 	u8 status;
-- 
2.17.1