Allow group key handshake message 1/2 to be retransmitted for testing

The new hostapd control interface command "RESEND_GROUP_M1 <addr>" can
be used to request a retransmission of the Group Key Handshake message
1/2 for the current GTK.

This functionality is for testing purposes and included only in builds
with CONFIG_TESTING_OPTIONS=y.

Signed-off-by: Jouni Malinen <j@w1.fi>

hostapd/ctrl_iface.c

@@ -2033,6 +2033,26 @@ static int hostapd_ctrl_reset_pn(struct hostapd_data *hapd, const char *cmd)
 				   sta->last_tk, sta->last_tk_len);
 }
 
+
+static int hostapd_ctrl_resend_group_m1(struct hostapd_data *hapd,
+					const char *cmd)
+{
+	struct sta_info *sta;
+	u8 addr[ETH_ALEN];
+
+	if (hwaddr_aton(cmd, addr))
+		return -1;
+
+	sta = ap_get_sta(hapd, addr);
+	if (!sta || !sta->wpa_sm)
+		return -1;
+
+	wpa_printf(MSG_INFO,
+		   "TESTING: Send group M1 for the same GTK and zero RSC to "
+		   MACSTR, MAC2STR(sta->addr));
+	return wpa_auth_resend_group_m1(sta->wpa_sm);
+}
+
 #endif /* CONFIG_TESTING_OPTIONS */
 
 
@@ -2752,6 +2772,9 @@ static int hostapd_ctrl_iface_receive_process(struct hostapd_data *hapd,
 	} else if (os_strncmp(buf, "RESET_PN ", 9) == 0) {
 		if (hostapd_ctrl_reset_pn(hapd, buf + 9) < 0)
 			reply_len = -1;
+	} else if (os_strncmp(buf, "RESEND_GROUP_M1 ", 16) == 0) {
+		if (hostapd_ctrl_resend_group_m1(hapd, buf + 16) < 0)
+			reply_len = -1;
 #endif /* CONFIG_TESTING_OPTIONS */
 	} else if (os_strncmp(buf, "CHAN_SWITCH ", 12) == 0) {
 		if (hostapd_ctrl_iface_chan_switch(hapd->iface, buf + 12))

src/ap/wpa_auth.c

@@ -4501,3 +4501,58 @@ void wpa_auth_get_fils_aead_params(struct wpa_state_machine *sm,
 }
 
 #endif /* CONFIG_FILS */
+
+
+#if CONFIG_TESTING_OPTIONS
+int wpa_auth_resend_group_m1(struct wpa_state_machine *sm)
+{
+	u8 rsc[WPA_KEY_RSC_LEN];
+	struct wpa_group *gsm = sm->group;
+	const u8 *kde;
+	u8 *kde_buf = NULL, *pos, *opos, hdr[2];
+	size_t kde_len;
+	u8 *gtk;
+
+	/* Send EAPOL(1, 1, 1, !Pair, G, RSC, GNonce, MIC(PTK), GTK[GN]) */
+	os_memset(rsc, 0, WPA_KEY_RSC_LEN);
+	/* Use 0 RSC */
+	wpa_auth_logger(sm->wpa_auth, sm->addr, LOGGER_DEBUG,
+			"sending 1/2 msg of Group Key Handshake (TESTING)");
+
+	gtk = gsm->GTK[gsm->GN - 1];
+	if (sm->wpa == WPA_VERSION_WPA2) {
+		kde_len = 2 + RSN_SELECTOR_LEN + 2 + gsm->GTK_len +
+			ieee80211w_kde_len(sm);
+		kde_buf = os_malloc(kde_len);
+		if (kde_buf == NULL)
+			return -1;
+
+		kde = pos = kde_buf;
+		hdr[0] = gsm->GN & 0x03;
+		hdr[1] = 0;
+		pos = wpa_add_kde(pos, RSN_KEY_DATA_GROUPKEY, hdr, 2,
+				  gtk, gsm->GTK_len);
+		opos = pos;
+		pos = ieee80211w_kde_add(sm, pos);
+		if (pos - opos >= WPA_IGTK_KDE_PREFIX_LEN) {
+			opos += 2; /* skip keyid */
+			os_memset(opos, 0, 6); /* clear PN */
+		}
+		kde_len = pos - kde;
+	} else {
+		kde = gtk;
+		kde_len = gsm->GTK_len;
+	}
+
+	wpa_send_eapol(sm->wpa_auth, sm,
+		       WPA_KEY_INFO_SECURE |
+		       (wpa_mic_len(sm->wpa_key_mgmt, sm->pmk_len) ?
+			WPA_KEY_INFO_MIC : 0) |
+		       WPA_KEY_INFO_ACK |
+		       (!sm->Pair ? WPA_KEY_INFO_INSTALL : 0),
+		       rsc, NULL, kde, kde_len, gsm->GN, 1);
+
+	os_free(kde_buf);
+	return 0;
+}
+#endif /* CONFIG_TESTING_OPTIONS */

src/ap/wpa_auth.h

@@ -427,4 +427,6 @@ u8 * wpa_auth_write_assoc_resp_owe(struct wpa_state_machine *sm,
 				   u8 *pos, size_t max_len,
 				   const u8 *req_ies, size_t req_ies_len);
 
+int wpa_auth_resend_group_m1(struct wpa_state_machine *sm);
+
 #endif /* WPA_AUTH_H */