SAE: Reuse previously generated PWE on a retry with the same AP

Do not start SAE authentication from scratch when the AP requests
anti-clogging token to be used. Instead, use the previously generated
PWE as-is if the retry is for the same AP and the same group. This saves
unnecessary processing on the station side in case the AP is under heavy
SAE authentiation load.

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

diff --git a/src/common/sae.h b/src/common/sae.h
index bb33761f9722faa64ea2eae09b0de2a26c1845e6..3eb6e323a68ffb2e019d07e6cfff4574cf71f2d1 100644 (file)
--- a/src/common/sae.h
+++ b/src/common/sae.h
@@ -41,6 +41,7 @@ struct sae_temporary_data {
        struct wpabuf *anti_clogging_token;
        char *pw_id;
        int vlan_id;
+       u8 bssid[ETH_ALEN];
 };
 
 enum sae_state {

diff --git a/wpa_supplicant/sme.c b/wpa_supplicant/sme.c
index c22ddba139f72c12ca88290ad71d753843c7fb82..925cfa0550ed99e4815dd5c41852bc83613946e4 100644 (file)
--- a/wpa_supplicant/sme.c
+++ b/wpa_supplicant/sme.c
@@ -84,7 +84,8 @@ static int sme_set_sae_group(struct wpa_supplicant *wpa_s)
 
 static struct wpabuf * sme_auth_build_sae_commit(struct wpa_supplicant *wpa_s,
                                                 struct wpa_ssid *ssid,
-                                                const u8 *bssid, int external)
+                                                const u8 *bssid, int external,
+                                                int reuse)
 {
        struct wpabuf *buf;
        size_t len;
@@ -111,6 +112,12 @@ static struct wpabuf * sme_auth_build_sae_commit(struct wpa_supplicant *wpa_s,
                return NULL;
        }
 
+       if (reuse && wpa_s->sme.sae.tmp &&
+           os_memcmp(bssid, wpa_s->sme.sae.tmp->bssid, ETH_ALEN) == 0) {
+               wpa_printf(MSG_DEBUG,
+                          "SAE: Reuse previously generated PWE on a retry with the same AP");
+               goto reuse_data;
+       }
        if (sme_set_sae_group(wpa_s) < 0) {
                wpa_printf(MSG_DEBUG, "SAE: Failed to select group");
                return NULL;
@@ -123,7 +130,10 @@ static struct wpabuf * sme_auth_build_sae_commit(struct wpa_supplicant *wpa_s,
                wpa_printf(MSG_DEBUG, "SAE: Could not pick PWE");
                return NULL;
        }
+       if (wpa_s->sme.sae.tmp)
+               os_memcpy(wpa_s->sme.sae.tmp->bssid, bssid, ETH_ALEN);
 
+reuse_data:
        len = wpa_s->sme.sae_token ? wpabuf_len(wpa_s->sme.sae_token) : 0;
        if (ssid->sae_password_id)
                len += 4 + os_strlen(ssid->sae_password_id);
@@ -631,7 +641,8 @@ static void sme_send_authentication(struct wpa_supplicant *wpa_s,
        if (!skip_auth && params.auth_alg == WPA_AUTH_ALG_SAE) {
                if (start)
                        resp = sme_auth_build_sae_commit(wpa_s, ssid,
-                                                        bss->bssid, 0);
+                                                        bss->bssid, 0,
+                                                        start == 2);
                else
                        resp = sme_auth_build_sae_confirm(wpa_s, 0);
                if (resp == NULL) {
@@ -914,7 +925,7 @@ static void sme_external_auth_send_sae_commit(struct wpa_supplicant *wpa_s,
 {
        struct wpabuf *resp, *buf;
 
-       resp = sme_auth_build_sae_commit(wpa_s, ssid, bssid, 1);
+       resp = sme_auth_build_sae_commit(wpa_s, ssid, bssid, 1, 0);
        if (!resp)
                return;
 
@@ -1065,7 +1076,7 @@ static int sme_sae_auth(struct wpa_supplicant *wpa_s, u16 auth_transaction,
                                                         len - sizeof(le16));
                if (!external)
                        sme_send_authentication(wpa_s, wpa_s->current_bss,
-                                               wpa_s->current_ssid, 1);
+                                               wpa_s->current_ssid, 2);
                else
                        sme_external_auth_send_sae_commit(
                                wpa_s, wpa_s->sme.ext_auth.bssid,