[PATCH] AP: save EAPOL received before assoc resp

[Jouni Malinen]

On Wed, Mar 02, 2016 at 06:50:26PM +0200, Eliad Peller wrote:
> There is a race condition in which wpa_supplicant might
> receive the EAPOL-Start frame (from the just-associated
> station) before the tx completion of the assoc response.

What is the point of that wpa_supplicant reference here? Isn't this
supposed to apply to AP side functionality? In other words, this applies
to both hostapd and wpa_supplicant (if using AP mode).

> This in turn will cause the EAPOL-Start frame to get
> dropped, and potentially failing the connection.

What kind of connection fails due to one EAPOL-Start frame being
dropped?

> Solve this by saving EAPOLs from authenticated-but-not-
> associated stations, and handling them during the assoc
> response tx completion processing.

I'm probably fine with this change in general, but couple of comments on
the implementation:

> diff --git a/src/ap/ieee802_11.c b/src/ap/ieee802_11.c
> @@ -2782,6 +2782,25 @@ static void handle_assoc_cb(struct hostapd_data *hapd,
> +	if (sta->pending_eapol_rx) {
> +		struct os_reltime now, age;
> +		os_get_reltime(&now);
> +		os_reltime_sub(&now, &sta->pending_eapol_rx_time, &age);
> +		if (age.sec == 0 && age.usec < 200000 &&
> +		    os_memcmp(sta->pending_eapol_rx_src,
> +			      mgmt->da, ETH_ALEN) == 0) {

What is the point of comparing sta->pending_eapol_rx_src to mgmt->da?
This is after sta = ap_get_sta(hapd, mgmt->da) and there is not really
any possibility for these to be different..

> diff --git a/src/ap/ieee802_1x.c b/src/ap/ieee802_1x.c
> @@ -891,6 +891,18 @@ void ieee802_1x_receive(struct hostapd_data *hapd, const u8 *sa, const u8 *buf,
> +		if (sta && (sta->flags & WLAN_STA_AUTH)) {
> +			wpa_printf(MSG_DEBUG, "Saving EAPOL for later use");
> +			wpabuf_free(sta->pending_eapol_rx);
> +			sta->pending_eapol_rx = wpabuf_alloc_copy(buf, len);
> +			if (sta->pending_eapol_rx) {
> +				os_get_reltime(&sta->pending_eapol_rx_time);
> +				os_memcpy(sta->pending_eapol_rx_src, sa,
> +					  ETH_ALEN);

Similarly here.. Why is sa copied into sta->pending_eapol_rx_src when
sta->addr already contains the MAC address of the STA which is sa here
after sta = ap_get_sta(hapd, sa).

> diff --git a/src/ap/sta_info.h b/src/ap/sta_info.h
> @@ -113,6 +113,10 @@ struct sta_info {
> +	struct wpabuf *pending_eapol_rx;
> +	struct os_reltime pending_eapol_rx_time;
> +	u8 pending_eapol_rx_src[ETH_ALEN];

pending_eapol_rx_src should go away. One allocation could be used to
store both the pending frame and pending_eapol_rx_time to reduce the
size of struct sta_info due to this type of short-lived data.

-- 
Jouni Malinen                                            PGP id EFC895FA