Hi!
> From: Mathy Vanhoef <Mathy.Vanhoef@xxxxxxxxxxx>
>
> commit 94034c40ab4a3fcf581fbc7f8fdf4e29943c4a24 upstream.
>
> Simultaneously prevent mixed key attacks (CVE-2020-24587) and fragment
> cache attacks (CVE-2020-24586). This is accomplished by assigning a
> unique color to every key (per interface) and using this to track which
> key was used to decrypt a fragment. When reassembling frames, it is
> now checked whether all fragments were decrypted using the same key.
>
> To assure that fragment cache attacks are also prevented, the ID that is
> assigned to keys is unique even over (re)associations and (re)connects.
> This means fragments separated by a (re)association or (re)connect will
> not be reassembled. Because mac80211 now also prevents the reassembly of
> mixed encrypted and plaintext fragments, all cache attacks are
> prevented.
> --- a/net/mac80211/key.c
> +++ b/net/mac80211/key.c
> @@ -799,6 +799,7 @@ int ieee80211_key_link(struct ieee80211_
> struct ieee80211_sub_if_data *sdata,
> struct sta_info *sta)
> {
> + static atomic_t key_color = ATOMIC_INIT(0);
> struct ieee80211_key *old_key;
This is nice and simple, but does not include any kind of overflow
handling. sparc32 moved away from 24-bit atomics, which is good I
guess. OTOH if this is incremented 10 times a second, we'll still
overflow in 6 years or so. Can attacker make it overflow?
Should this have a note why overflow is not possible / why it is not a
problem?
Best regards,
Pavel
--
http://www.livejournal.com/~pavelmachek
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