From c36219748ce2ee2d122dc25c14a617b39a827dd4 Mon Sep 17 00:00:00 2001 From: Mathy Vanhoef Date: Mon, 7 Jun 2021 22:38:56 +0800 Subject: [PATCH 1/2] cfg80211: mitigate A-MSDU aggregation attacks Signed-off-by: Kong Zhiquan ------------------------------------------------------- commit 2b8a1fee3488c602aca8bea004a087e60806a5cf upstream. Mitigate A-MSDU injection attacks (CVE-2020-24588) by detecting if the destination address of a subframe equals an RFC1042 (i.e., LLC/SNAP) header, and if so dropping the complete A-MSDU frame. This mitigates known attacks, although new (unknown) aggregation-based attacks may remain possible. This defense works because in A-MSDU aggregation injection attacks, a normal encrypted Wi-Fi frame is turned into an A-MSDU frame. This means the first 6 bytes of the first A-MSDU subframe correspond to an RFC1042 header. In other words, the destination MAC address of the first A-MSDU subframe contains the start of an RFC1042 header during an aggregation attack. We can detect this and thereby prevent this specific attack. For details, see Section 7.2 of "Fragment and Forge: Breaking Wi-Fi Through Frame Aggregation and Fragmentation". Note that for kernel 4.9 and above this patch depends on "mac80211: properly handle A-MSDUs that start with a rfc1042 header". Otherwise this patch has no impact and attacks will remain possible. Cc: stable@vger.kernel.org Signed-off-by: Mathy Vanhoef Link: https://lore.kernel.org/r/20210511200110.25d93176ddaf.I9e265b597f2cd23eb44573f35b625947b386a9de@changeid Signed-off-by: Johannes Berg Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang --- net/wireless/util.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/wireless/util.c b/net/wireless/util.c index 1a878b84cbd0..1b3e2d37cd57 100644 --- a/net/wireless/util.c +++ b/net/wireless/util.c @@ -652,6 +652,9 @@ void ieee80211_amsdu_to_8023s(struct sk_buff *skb, struct sk_buff_head *list, remaining = skb->len - offset; if (subframe_len > remaining) goto purge; + /* mitigate A-MSDU aggregation injection attacks */ + if (ether_addr_equal(eth.h_dest, rfc1042_header)) + goto purge; offset += sizeof(struct ethhdr); last = remaining <= subframe_len + padding; -- Gitee From 004fefe088043d26c42c892f70d6fff362fa6e9d Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Mon, 7 Jun 2021 22:38:57 +0800 Subject: [PATCH 2/2] mac80211: drop A-MSDUs on old ciphers Signed-off-by: Kong Zhiquan ----------------------------------------------------- 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 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang --- net/mac80211/rx.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c index 5e56719f999c..e07f17dd42b9 100644 --- a/net/mac80211/rx.c +++ b/net/mac80211/rx.c @@ -5,7 +5,7 @@ * Copyright 2007-2010 Johannes Berg * Copyright 2013-2014 Intel Mobile Communications GmbH * Copyright(c) 2015 - 2017 Intel Deutschland GmbH - * Copyright (C) 2018 Intel Corporation + * Copyright (C) 2018-2021 Intel Corporation * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as @@ -2607,6 +2607,23 @@ ieee80211_rx_h_amsdu(struct ieee80211_rx_data *rx) if (is_multicast_ether_addr(hdr->addr1)) 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; + } + } + return __ieee80211_rx_h_amsdu(rx, 0); } -- Gitee