Re: mac80211 drops packet with old IV after rekeying

[Ben Greear <greearb@candelatech.com>]

On 05/18/2015 01:03 AM, Janusz Dziedzic wrote:
> On 18 May 2015 at 08:14, Peer, Ilan <ilan.peer@intel.com> wrote:
>>
>>
>>> -----Original Message-----
>>> From: linux-wireless-owner@vger.kernel.org [mailto:linux-wireless-
>>> owner@vger.kernel.org] On Behalf Of Johannes Berg
>>> Sent: Sunday, May 17, 2015 23:22
>>> To: Emmanuel Grumbach
>>> Cc: alexander.wetzel@web.de; Jouni Malinen; linux-wireless
>>> Subject: Re: mac80211 drops packet with old IV after rekeying
>>>
>>> On Sun, 2015-05-17 at 23:13 +0300, Emmanuel Grumbach wrote:
>>>
>>>>>> Yeah - ok. But how come we *already* set the pointer to the new key
>>>>>> while the HW is still successfully decrypting with the old key.
>>>>>> This is the point I can' figure out. I'd expect the transmitting
>>>>>> side to stop using the old key prior to sending the EAPOL (which
>>
>> There is probably no synchronization between the 4way HS and other data traffic on the transmitter side, as these are different processes. So it is possible that after receiving message 3 and before setting the keys, the HW would be able to decrypt additional frames with the old key.
>>
> In ath10k hw we have peer flag WMI_PEER_NEED_PTK_4_WAY.
> This will lock tx (discard data) until PTK_M4_SENT and install key
> after 4way HS.
> But I didn't check ptk_rekey and I am not sure this will help with all races.

I think at least the 10.1 firmware has bugs that keep this from actually working
just right.  Maybe later firmware works better.

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com