WPA-EAP/802.1x AP mode without NL80211_CMD_SET_STATION driver support

[Pali Rohár]

PING?

On Monday 11 May 2020 12:37:50 Pali Rohár wrote:
> Hello Jouni!
> 
> When hostapd is compiled without CONFIG_NO_VLAN option then
> WPA-EAP/802.1x AP mode is not working with wifi card which does not
> support NL80211_CMD_SET_STATION command and uses nl80211 hostapd driver.
> 
> NL80211_CMD_SET_STATION command is used by nl80211 hostapd driver to
> configure NL80211_ATTR_STA_VLAN, see i802_set_sta_vlan() function.
> 
> Here is hostapd log from Turris MOX router when is configured in WPA-EAP
> AP mode. It has SDIO wifi card managed by kernel driver mwifiex_sdio
> which does not implement NL80211_CMD_SET_STATION command when card is in
> AP mode.
> 
> May 11 09:31:28 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 RADIUS: Received RADIUS packet matched with a pending request, round trip time 0.00 sec
> May 11 09:31:28 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.11: binding station to interface 'wlan1'
> May 11 09:31:28 turris hostapd: nl80211: NL80211_ATTR_STA_VLAN (addr=c4:d9:87:6c:38:01 ifname=wlan1 vlan_id=0) failed: -524 (No error information)
> May 11 09:31:28 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.11: could not bind the STA entry to vlan_id=0
> May 11 09:31:28 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: decapsulated EAP packet (code=3 id=27 len=4) from RADIUS server: EAP Success
> May 11 09:31:28 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: Sending EAP Packet (identifier 27)
> May 11 09:31:31 turris hostapd: wlan1: CTRL-EVENT-EAP-RETRANSMIT2 c4:d9:87:6c:38:01
> May 11 09:31:31 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: Sending EAP Packet (identifier 27)
> May 11 09:31:37 turris hostapd: wlan1: CTRL-EVENT-EAP-RETRANSMIT2 c4:d9:87:6c:38:01
> May 11 09:31:37 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: Sending EAP Packet (identifier 27)
> May 11 09:31:47 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.11: disassociated
> May 11 09:31:47 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 WPA: event 2 notification
> 
> EAP authentication from radius server is successful, wpa_supplicant on
> client side also see successful authentication, but link is not
> established.
> 
> That failed error code 524 is internal Linux kernel number for ENOTSUPP
> (double PP), see [1]. Userspace uses ENOTSUP (single P) code 95.
> 
> Error printed in hostapd log is triggered by ap_sta_bind_vlan() call
> from ieee802_1x_receive_auth() function located in src/ap/ieee802_1x.c
> file.
> 
> ap_sta_bind_vlan() calls hostapd_drv_set_sta_vlan() which for
> unsupported hostapd driver returns zero and for supported hostapd driver
> calls appropriate kernel interface, i.e. hostapd_drv_set_sta_vlan().
> Which for card with unsupported NL80211_CMD_SET_STATION command returns
> error code -524.
> 
> When hostapd is compiled with CONFIG_NO_VLAN then ap_sta_bind_vlan()
> always returns zero.
> 
> I applied following change to hostapd sources:
> 
> diff --git a/src/ap/sta_info.c b/src/ap/sta_info.c
> index 93f1f0c20..9059162a8 100644
> --- a/src/ap/sta_info.c
> +++ b/src/ap/sta_info.c
> @@ -1092,6 +1092,10 @@ skip_counting:
>  		hostapd_logger(hapd, sta->addr, HOSTAPD_MODULE_IEEE80211,
>  			       HOSTAPD_LEVEL_DEBUG, "could not bind the STA "
>  			       "entry to vlan_id=%d", sta->vlan_id);
> +		/* Ignore error when driver does not support setting vlan
> +		 * and we were not requested to set non-zero vlan id */
> +		if (ret == -ENOTSUP && sta->vlan_id == 0)
> +			ret = 0;
>  	}
>  
>  	/* During 1x reauth, if the vlan id changes, then remove the old id. */
> diff --git a/src/drivers/driver_nl80211.c b/src/drivers/driver_nl80211.c
> index d48f8cb76..0906508d4 100644
> --- a/src/drivers/driver_nl80211.c
> +++ b/src/drivers/driver_nl80211.c
> @@ -6848,6 +6848,8 @@ static int i802_set_sta_vlan(struct i802_bss *bss, const u8 *addr,
>  
>  	ret = send_and_recv_msgs(drv, msg, NULL, NULL);
>  	if (ret < 0) {
> +		if (ret == -524) /* 524 - Linux internal ENOTSUPP (double PP) */
> +			ret = -ENOTSUP;
>  		wpa_printf(MSG_ERROR, "nl80211: NL80211_ATTR_STA_VLAN (addr="
>  			   MACSTR " ifname=%s vlan_id=%d) failed: %d (%s)",
>  			   MAC2STR(addr), ifname, vlan_id, ret,
> 
> It changes error code from ENOTSUP (single P) and ENOTSUPP (double PP)
> to zero, which is propagated back to the ieee802_1x_receive_auth()
> function.
> 
> And with this change WPA-EAP/802.1x AP mode started working. Here is
> hostapd log:
> 
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 RADIUS: Received RADIUS packet matched with a pending request, round trip time 0.00 sec
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.11: binding station to interface 'wlan1'
> May 11 09:28:20 turris hostapd: nl80211: NL80211_ATTR_STA_VLAN (addr=c4:d9:87:6c:38:01 ifname=wlan1 vlan_id=0) failed: -95 (Not supported)
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.11: could not bind the STA entry to vlan_id=0
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: old identity 'anonymous' updated with User-Name from Access-Accept 'anonymous'
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: decapsulated EAP packet (code=3 id=27 len=4) from RADIUS server: EAP Success
> May 11 09:28:20 turris hostapd: wlan1: CTRL-EVENT-EAP-SUCCESS2 c4:d9:87:6c:38:01
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: Sending EAP Packet (identifier 27)
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 WPA: sending 1/4 msg of 4-Way Handshake
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 WPA: received EAPOL-Key frame (2/4 Pairwise)
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 WPA: sending 3/4 msg of 4-Way Handshake
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 WPA: received EAPOL-Key frame (4/4 Pairwise)
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 WPA: pairwise key handshake completed (RSN)
> May 11 09:28:20 turris hostapd: wlan1: AP-STA-CONNECTED c4:d9:87:6c:38:01
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: authorizing port
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 RADIUS: starting accounting session 0C7AC96B17442FD4
> May 11 09:28:20 turris hostapd: wlan1: RADIUS Sending RADIUS message to accounting server
> May 11 09:28:20 turris hostapd: wlan1: RADIUS Next RADIUS client retransmit in 3 seconds
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 IEEE 802.1X: authenticated - EAP type: 21 (TTLS)
> May 11 09:28:20 turris hostapd: wlan1: RADIUS Received 20 bytes from RADIUS server
> May 11 09:28:20 turris hostapd: wlan1: RADIUS Received RADIUS message
> May 11 09:28:20 turris hostapd: wlan1: STA c4:d9:87:6c:38:01 RADIUS: Received RADIUS packet matched with a pending request, round trip time 0.00 sec
> 
> Jouni, I think this is bug in hostapd's 802.1X code. Function
> ieee802_1x_receive_auth() skips whole processing of 802.1X path when
> receives RADIUS_CODE_ACCESS_ACCEPT response and ap_sta_bind_vlan()
> function fails.
> 
> The most suspicious part for me is why hostapd_drv_set_sta_vlan()
> function returns zero when hostapd driver does not support
> set_sta_vlan() function, but returns -ENOTSUP (or -ENOTSUPP) when kernel
> driver does not support this functionality. And also why this code path
> is ignored when hostapd is configured with CONFIG_NO_VLAN compile time
> option.
> 
> Do you have any suggestions how to make AP working in WPA-EAP/802.1x
> mode for cards without NL80211_CMD_SET_STATION command? I would like to
> avoid having custom hostapd patch (like one above) and have ability to
> use upstream unpatched hostapd daemon.
> 
> [1] - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/errno.h