Software TKIP group rekeying and phase1 issue

[Bernhard Schmidt]

Hi,

When hostapd triggers rekeying of the group key, wpa_supplicant successfully 
sets the correct new key. On first use of the new key tkip_mixing_phase1() 
should be applied before decrypting any frames, tkip_decrypt() does this as

if (iv32 != (u32)(key->wk_keyrsc[tid] >> 16) || !ctx->rx_phase1_done) {
	tkip_mixing_phase1(ctx->rx_ttak, key->wk_key,
		wh->i_addr2, iv32);
	ctx->rx_phase1_done = 1;
}

But, after a rekeying event, neither of this condition match, especially as 
rx_phase1_done is no longer zero, therefore tkip_mixing_phase1() isn't called 
which leads to dropped frames with "TKIP ICV mismatch on decrypt" messages.

A working solution for that is to set rx_phase1_done to zero inside 
tkip_setkey(). I'm not sure whether that is the best solution or if it is 
better to set/reset the wk_keyrsc sequence, at least this diff works for me 
and few other over at the Forums.

Index: sys/net80211/ieee80211_crypto_tkip.c
===================================================================
--- sys/net80211/ieee80211_crypto_tkip.c	(revision 203242)
+++ sys/net80211/ieee80211_crypto_tkip.c	(working copy)
@@ -144,6 +144,8 @@ tkip_setkey(struct ieee80211_key *k)
 		return 0;
 	}
 	k->wk_keytsc = 1;		/* TSC starts at 1 */
+	if (k->wk_flags & IEEE80211_KEY_GROUP)
+		ctx->rx_phase1_done = 0;
 	return 1;
 }

-- 
Bernhard