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From: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
Date: Tue, 11 May 2021 20:02:42 +0200
Subject: [PATCH] mac80211: assure all fragments are encrypted
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: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2204,6 +2204,16 @@ ieee80211_reassemble_find(struct ieee802
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)
{
@@ -2248,12 +2258,7 @@ ieee80211_rx_h_defragment(struct ieee802
/* 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
@@ -2295,11 +2300,7 @@ ieee80211_rx_h_defragment(struct ieee802
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--) {
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