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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>
Link: https://lore.kernel.org/r/20210511200110.30c4394bb835.I5acfdb552cc1d20c339c262315950b3eac491397@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Mathy Vanhoef 2021-05-11 20:02:42 +02:00 committed by Johannes Berg
parent 297c4de6f7
commit 965a7d72e7
1 changed files with 12 additions and 11 deletions
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23
net/mac80211/rx.c
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@ -2194,6 +2194,16 @@ 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)
{
@ -2238,12 +2248,7 @@ 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
@ -2285,11 +2290,7 @@ 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--) {