Messages in this thread | | | Date | Tue, 1 Jun 2021 11:26:19 +0200 | From | Pavel Machek <> | Subject | Re: [PATCH 5.10 024/252] mac80211: prevent mixed key and fragment cache attacks |
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Hi!
> From: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be> > > 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
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