Re: [PATCH 2/3] Replace WPA_ALG_PMK with KEY_FLAG_PMK

On Thu, Feb 27, 2020 at 10:52:47PM +0100, Alexander Wetzel wrote:
> Drop the no longer needed internal alg WPA_ALG_PMK and use KEY_FLAG_PMK
> as replacement.

> This is of course fully optional. With the key_flag API now merged WPA_ALG_PMK
> just looks redundant and the few users of it are easily converted.

This is probably fine as a general direction, but I'm a bit concerned
about the use of this type of comparison of key_flag which is defined as
a bitmap:

> @@ -3093,7 +3092,7 @@ static int wpa_driver_nl80211_set_key(struct i802_bss *bss,
> -	if (alg == WPA_ALG_PMK &&
> +	if (key_flag == KEY_FLAG_PMK &&

Sure, we do not really use KEY_FLAG_PMK with any other bit set, but
still, comparing key_flag to any fixed value looks a bit strange and
potentially easy to break should we ever add some more flag bits that
could be used even with KEY_FLAG_PMK.

>  	    (drv->capa.flags & WPA_DRIVER_FLAGS_4WAY_HANDSHAKE_8021X))
>  		return nl80211_set_pmk(drv, key, key_len, addr);
>  	if (key_flag & KEY_FLAG_PMK)

And here is the way of comparing it against the specific bit for PMK in
a manner that survives addition of new bits to the key_flag bitmap.

-- 
Jouni Malinen                                            PGP id EFC895FA