netdev - Re: [PATCH] mac80211: Do not send Layer 2 Update frame before authorization

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Date:   Wed, 11 Sep 2019 15:06:03 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Jouni Malinen <jouni@...eaurora.org>
Cc:     linux-wireless@...r.kernel.org, David Miller <davem@...emloft.net>,
        netdev@...r.kernel.org
Subject: Re: [PATCH] mac80211: Do not send Layer 2 Update frame before
 authorization

On Wed, 2019-09-11 at 16:03 +0300, Jouni Malinen wrote:
> The Layer 2 Update frame is used to update bridges when a station roams
> to another AP even if that STA does not transmit any frames after the
> reassociation. This behavior was described in IEEE Std 802.11F-2003 as
> something that would happen based on MLME-ASSOCIATE.indication, i.e.,
> before completing 4-way handshake. However, this IEEE trial-use
> recommended practice document was published before RSN (IEEE Std
> 802.11i-2004) and as such, did not consider RSN use cases. Furthermore,
> IEEE Std 802.11F-2003 was withdrawn in 2006 and as such, has not been
> maintained amd should not be used anymore.
> 
> Sending out the Layer 2 Update frame immediately after association is
> fine for open networks (and also when using SAE, FT protocol, or FILS
> authentication when the station is actually authenticated by the time
> association completes). However, it is not appropriate for cases where
> RSN is used with PSK or EAP authentication since the station is actually
> fully authenticated only once the 4-way handshake completes after
> authentication and attackers might be able to use the unauthenticated
> triggering of Layer 2 Update frame transmission to disrupt bridge
> behavior.
> 
> Fix this by postponing transmission of the Layer 2 Update frame from
> station entry addition to the point when the station entry is marked
> authorized. Similarly, send out the VLAN binding update only if the STA
> entry has already been authorized.

Reviewed-by: Johannes Berg <johannes@...solutions.net>

Dave, if you were still planning to send a pull request to Linus before
he closes the tree on Sunday this would be good to include (and we
should also backport it to stable later).

If not, I can pick it up afterwards, let me know.

Thanks,
johannes