Defer passphrase-to-PSK hashing out of 802.11 authentication ACL check

Hashing takes quite some time (can be about one second on a low-power
CPU for each passphrase provided), so hostapd can easily hit the 900 ms
Wi-Fi client authentication deadline (mac80211 uses 3x 300 ms). This can
be fixed by storing the passphrase instead of PSK with the STA and defer
the hashing into the WPA/RSN 4-way handshake, when enumerating all PSKs.

This applies for the case where a RADIUS server is used to store the
per-STA passphrases and this passphrase is delivered as part of the MAC
ACL check during IEEE 802.11 Authentication frame processing.

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

src/ap/ap_config.h

@@ -128,9 +128,12 @@ struct hostapd_vlan {
 };
 
 #define PMK_LEN 32
+#define MAX_PASSPHRASE_LEN 63
 struct hostapd_sta_wpa_psk_short {
 	struct hostapd_sta_wpa_psk_short *next;
+	unsigned int is_passphrase:1;
 	u8 psk[PMK_LEN];
+	char passphrase[MAX_PASSPHRASE_LEN + 1];
 };
 
 struct hostapd_wpa_psk {

src/ap/ieee802_11_auth.c

@@ -15,7 +15,6 @@
 
 #include "utils/common.h"
 #include "utils/eloop.h"
-#include "crypto/sha1.h"
 #include "radius/radius.h"
 #include "radius/radius_client.h"
 #include "hostapd.h"
@@ -443,7 +442,7 @@ static void decode_tunnel_passwords(struct hostapd_data *hapd,
 				    struct hostapd_cached_radius_acl *cache)
 {
 	int passphraselen;
-	char *passphrase, *strpassphrase;
+	char *passphrase;
 	size_t i;
 	struct hostapd_sta_wpa_psk_short *psk;
 
@@ -464,19 +463,16 @@ static void decode_tunnel_passwords(struct hostapd_data *hapd,
 		 * passphrase does not contain the NULL termination.
 		 * Add it here as pbkdf2_sha1() requires it.
 		 */
-		strpassphrase = os_zalloc(passphraselen + 1);
 		psk = os_zalloc(sizeof(struct hostapd_sta_wpa_psk_short));
-		if (strpassphrase && psk) {
-			os_memcpy(strpassphrase, passphrase, passphraselen);
-			pbkdf2_sha1(strpassphrase,
-				    hapd->conf->ssid.ssid,
-				    hapd->conf->ssid.ssid_len, 4096,
-				    psk->psk, PMK_LEN);
+		if (psk) {
+			if (passphraselen > MAX_PASSPHRASE_LEN)
+				passphraselen = MAX_PASSPHRASE_LEN;
+			os_memcpy(psk->passphrase, passphrase, passphraselen);
+			psk->is_passphrase = 1;
 			psk->next = cache->psk;
 			cache->psk = psk;
 			psk = NULL;
 		}
-		os_free(strpassphrase);
 		os_free(psk);
 		os_free(passphrase);
 	}

src/ap/wpa_auth_glue.c

@@ -12,6 +12,7 @@
 #include "common/ieee802_11_defs.h"
 #include "common/sae.h"
 #include "common/wpa_ctrl.h"
+#include "crypto/sha1.h"
 #include "eapol_auth/eapol_auth_sm.h"
 #include "eapol_auth/eapol_auth_sm_i.h"
 #include "eap_server/eap.h"
@@ -246,6 +247,13 @@ static const u8 * hostapd_wpa_auth_get_psk(void *ctx, const u8 *addr,
 		struct hostapd_sta_wpa_psk_short *pos;
 		psk = sta->psk->psk;
 		for (pos = sta->psk; pos; pos = pos->next) {
+			if (pos->is_passphrase) {
+				pbkdf2_sha1(pos->passphrase,
+					    hapd->conf->ssid.ssid,
+					    hapd->conf->ssid.ssid_len, 4096,
+					    pos->psk, PMK_LEN);
+				pos->is_passphrase = 0;
+			}
 			if (pos->psk == prev_psk) {
 				psk = pos->next ? pos->next->psk : NULL;
 				break;