Date: Thu, 4 Feb 2010 09:15:04 +0100 From: Bernhard Schmidt <bschmidt@techwires.net> To: freebsd-net@freebsd.org Subject: Software TKIP group rekeying and phase1 issue Message-ID: <201002040915.04470.bschmidt@techwires.net>
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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
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