From patchwork Thu May 13 07:03:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Felix Fietkau X-Patchwork-Id: 437686 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60C76C433B4 for ; Thu, 13 May 2021 07:03:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2499761285 for ; Thu, 13 May 2021 07:03:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231451AbhEMHES (ORCPT ); Thu, 13 May 2021 03:04:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56716 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230246AbhEMHER (ORCPT ); Thu, 13 May 2021 03:04:17 -0400 Received: from nbd.name (nbd.name [IPv6:2a01:4f8:221:3d45::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03210C061574 for ; Thu, 13 May 2021 00:03:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=nbd.name; s=20160729; h=Content-Transfer-Encoding:MIME-Version:Message-Id:Date:Subject :Cc:To:From:Sender:Reply-To:Content-Type:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: In-Reply-To:References:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=EqLaSyzcSCBfBlTR/kEof3rcsA9sQ2ZSIrNmQ6zcbG8=; b=UhD32vclZHPgpYkaoDIA0sKAp3 LZEXhqBtpRg3kq7dt0BQD5OAubUux6J3Q0ecuZ6aPwOv7758hutnI2zy/7kB64hzDHlatRzpxrtAZ kj0pRQZroasGf7HcVLC0Xv+JjMWi3Q64qF4J5ifffMY3od+GpP7dz0ib/3x6fB5EjjaQ=; Received: from p54ae9ff2.dip0.t-ipconnect.de ([84.174.159.242] helo=localhost.localdomain) by ds12 with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from ) id 1lh5NB-0002Nm-GB; Thu, 13 May 2021 09:03:05 +0200 From: Felix Fietkau To: linux-wireless@vger.kernel.org Cc: kvalo@codeaurora.org Subject: [PATCH 5.13] mt76: validate rx A-MSDU subframes Date: Thu, 13 May 2021 09:03:03 +0200 Message-Id: <20210513070303.20253-1-nbd@nbd.name> X-Mailer: git-send-email 2.30.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org 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". Signed-off-by: Felix Fietkau --- drivers/net/wireless/mediatek/mt76/mac80211.c | 26 +++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/drivers/net/wireless/mediatek/mt76/mac80211.c b/drivers/net/wireless/mediatek/mt76/mac80211.c index 977acab0360a..03fe62837557 100644 --- a/drivers/net/wireless/mediatek/mt76/mac80211.c +++ b/drivers/net/wireless/mediatek/mt76/mac80211.c @@ -514,10 +514,36 @@ EXPORT_SYMBOL_GPL(mt76_free_device); static void mt76_rx_release_amsdu(struct mt76_phy *phy, enum mt76_rxq_id q) { struct sk_buff *skb = phy->rx_amsdu[q].head; + struct mt76_rx_status *status = (struct mt76_rx_status *)skb->cb; struct mt76_dev *dev = phy->dev; phy->rx_amsdu[q].head = NULL; phy->rx_amsdu[q].tail = NULL; + + /* + * Validate if the amsdu has a proper first subframe. + * A single MSDU can be parsed as A-MSDU when the unauthenticated A-MSDU + * flag of the QoS header gets flipped. In such cases, the first + * subframe has a LLC/SNAP header in the location of the destination + * address. + */ + if (skb_shinfo(skb)->frag_list) { + int offset = 0; + + if (!(status->flag & RX_FLAG_8023)) { + offset = ieee80211_get_hdrlen_from_skb(skb); + + if ((status->flag & + (RX_FLAG_DECRYPTED | RX_FLAG_IV_STRIPPED)) == + RX_FLAG_DECRYPTED) + offset += 8; + } + + if (ether_addr_equal(skb->data + offset, rfc1042_header)) { + dev_kfree_skb(skb); + return; + } + } __skb_queue_tail(&dev->rx_skb[q], skb); }