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Commit 29bc5b2b authored by Mathy Vanhoef's avatar Mathy Vanhoef Committed by Greg Kroah-Hartman
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mac80211: assure all fragments are encrypted 



commit 965a7d72e798eb7af0aa67210e37cf7ecd1c9cad upstream.

Do not mix plaintext and encrypted fragments in protected Wi-Fi
networks. This fixes CVE-2020-26147.

Previously, an attacker was able to first forward a legitimate encrypted
fragment towards a victim, followed by a plaintext fragment. The
encrypted and plaintext fragment would then be reassembled. For further
details see Section 6.3 and Appendix D in the paper "Fragment and Forge:
Breaking Wi-Fi Through Frame Aggregation and Fragmentation".

Because of this change there are now two equivalent conditions in the
code to determine if a received fragment requires sequential PNs, so we
also move this test to a separate function to make the code easier to
maintain.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarMathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
Link: https://lore.kernel.org/r/20210511200110.30c4394bb835.I5acfdb552cc1d20c339c262315950b3eac491397@changeid


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e410dd4f

net/mac80211/rx.c

+12 −11
Original line number Diff line number Diff line
@@ -1942,6 +1942,16 @@ ieee80211_reassemble_find(struct ieee80211_sub_if_data *sdata, 
	return NULL;

}



static bool requires_sequential_pn(struct ieee80211_rx_data *rx, __le16 fc)

{

	return rx->key &&

		(rx->key->conf.cipher == WLAN_CIPHER_SUITE_CCMP ||

		 rx->key->conf.cipher == WLAN_CIPHER_SUITE_CCMP_256 ||

		 rx->key->conf.cipher == WLAN_CIPHER_SUITE_GCMP ||

		 rx->key->conf.cipher == WLAN_CIPHER_SUITE_GCMP_256) &&

		ieee80211_has_protected(fc);

}



static ieee80211_rx_result debug_noinline

ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)

{
@@ -1987,12 +1997,7 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx) 
		/* This is the first fragment of a new frame. */

		entry = ieee80211_reassemble_add(rx->sdata, frag, seq,

						 rx->seqno_idx, &(rx->skb));

		if (rx->key &&

		    (rx->key->conf.cipher == WLAN_CIPHER_SUITE_CCMP ||

		     rx->key->conf.cipher == WLAN_CIPHER_SUITE_CCMP_256 ||

		     rx->key->conf.cipher == WLAN_CIPHER_SUITE_GCMP ||

		     rx->key->conf.cipher == WLAN_CIPHER_SUITE_GCMP_256) &&

		    ieee80211_has_protected(fc)) {

		if (requires_sequential_pn(rx, fc)) {

			int queue = rx->security_idx;



			/* Store CCMP/GCMP PN so that we can verify that the
@@ -2034,11 +2039,7 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx) 
		u8 pn[IEEE80211_CCMP_PN_LEN], *rpn;

		int queue;



		if (!rx->key ||

		    (rx->key->conf.cipher != WLAN_CIPHER_SUITE_CCMP &&

		     rx->key->conf.cipher != WLAN_CIPHER_SUITE_CCMP_256 &&

		     rx->key->conf.cipher != WLAN_CIPHER_SUITE_GCMP &&

		     rx->key->conf.cipher != WLAN_CIPHER_SUITE_GCMP_256))

		if (!requires_sequential_pn(rx, fc))

			return RX_DROP_UNUSABLE;

		memcpy(pn, entry->last_pn, IEEE80211_CCMP_PN_LEN);

		for (i = IEEE80211_CCMP_PN_LEN - 1; i >= 0; i--) {