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From:   Johannes Berg <johannes@sipsolutions.net>
To:     linux-wireless@vger.kernel.org
Cc:     stable@vger.kernel.org, Johannes Berg <johannes.berg@intel.com>
Subject: [PATCH v4.14 05/10] mac80211: drop A-MSDUs on old ciphers
Date:   Mon, 31 May 2021 22:31:30 +0200
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From: Johannes Berg <johannes.berg@intel.com>

commit 270032a2a9c4535799736142e1e7c413ca7b836e upstream.

With old ciphers (WEP and TKIP) we shouldn't be using A-MSDUs
since A-MSDUs are only supported if we know that they are, and
the only practical way for that is HT support which doesn't
support old ciphers.

However, we would normally accept them anyway. Since we check
the MMIC before deaggregating A-MSDUs, and the A-MSDU bit in
the QoS header is not protected in TKIP (or WEP), this enables
attacks similar to CVE-2020-24588. To prevent that, drop A-MSDUs
completely with old ciphers.

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210511200110.076543300172.I548e6e71f1ee9cad4b9a37bf212ae7db723587aa@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/mac80211/rx.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index be7e37edad12..d6cdd0c025ca 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2455,6 +2455,23 @@ ieee80211_rx_h_amsdu(struct ieee80211_rx_data *rx)
 					  true))
 		return RX_DROP_UNUSABLE;
 
+	if (rx->key) {
+		/*
+		 * We should not receive A-MSDUs on pre-HT connections,
+		 * and HT connections cannot use old ciphers. Thus drop
+		 * them, as in those cases we couldn't even have SPP
+		 * A-MSDUs or such.
+		 */
+		switch (rx->key->conf.cipher) {
+		case WLAN_CIPHER_SUITE_WEP40:
+		case WLAN_CIPHER_SUITE_WEP104:
+		case WLAN_CIPHER_SUITE_TKIP:
+			return RX_DROP_UNUSABLE;
+		default:
+			break;
+		}
+	}
+
 	ieee80211_amsdu_to_8023s(skb, &frame_list, dev->dev_addr,
 				 rx->sdata->vif.type,
 				 rx->local->hw.extra_tx_headroom,
-- 
2.31.1