From patchwork Wed Feb 12 13:23:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Howard Chung X-Patchwork-Id: 11378541 X-Patchwork-Delegate: marcel@holtmann.org Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BA0CC13A4 for ; Wed, 12 Feb 2020 13:23:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FF092086A for ; Wed, 12 Feb 2020 13:23:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CSRbTp0c" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727698AbgBLNXg (ORCPT ); Wed, 12 Feb 2020 08:23:36 -0500 Received: from mail-pj1-f74.google.com ([209.85.216.74]:37059 "EHLO mail-pj1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727662AbgBLNXb (ORCPT ); Wed, 12 Feb 2020 08:23:31 -0500 Received: by mail-pj1-f74.google.com with SMTP id dw15so1358885pjb.2 for ; Wed, 12 Feb 2020 05:23:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=w10epyxLvI1AMDusIOewZ9Hw+W4QXY5j4khGzCFE/qU=; b=CSRbTp0cgmvvYED86UShjM6ebVFBVWmoUEIeo7pq2N59MZTYbk+bADSbZt33gVePGq dphTBNLWIxyja9ri+3b1r98pQnYg/8UpvMhP+xiOBweai1HRwiziWao2g2GZivD+iW6n swP+Kr511KN0bQbdAH5H/t0NT1Cwp83IYTNQBJ7E9hGIqvoqFEa1KAyur0IxjadrQnaW RvzFWsbu0AHdSM8TF51meWPdH76N2QWOTjknXzJ7Lz2KMgrePb25g3IG6+btvzEtfiMc 6kr5YOvTb81FA7625/4YvW1/UarZctyDBxz9w76Fiz6AbXuzATd4bRmJxPPlOrgugZWF 697A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=w10epyxLvI1AMDusIOewZ9Hw+W4QXY5j4khGzCFE/qU=; b=d50noLjwzqff6WP6IgAIs+ySxp3yhNUBIaI+90e9XNF39jawVSwz+Nk4Np4qDGrA6+ pkZqVKrBBhlHZ9JK0SLVJJcpQjGwW6QBI+G7XuMnTqx1gZmnA7b9flfmeG6LBDStZbSK 2KSbrWO5pJF4gIcTQMYVNviI9GzGscEebUzr7XQnoGhZ8x1I/y7NyMJkPRxz1et7+Cpa 9ovEBZ7ENyWn3pwd52BMtt+0IEzVrYstXeN5xjJcBvkRFYk+6G/HzvhLMGG7UWk9OaeS fdAaxEGR2qNf+BrFcbvIKpuAyEaE+SHxZLs8RAnmZfZioCM55GRi1q/aaSrEyCpMZvBN 4lYw== X-Gm-Message-State: APjAAAWLbEa8TR4tn4u3G+Nxj4NJiNSMtbAUE0bU3nOUZQIvcpPS+Cg8 g//dnTkbNqXBfraLgn1PqETOiYoHfXiUMKX76+eRa959mBiUulC2qYmO1chdb+smMetz34cuthL 6Xq2Tm+60lbWrvSbLlYA9dwTD5wK7hGE+8VZ9g8cObY1Odyu4E033qYx5n62UohBKS5GDakEiiB t6ygG5I+q1X90= X-Google-Smtp-Source: APXvYqweIa+s3oYripbme3DsFRlxtH2ALwUEkVJB/JEHC77sTiqqrkzOYJqa4fBbraA0805Q2Wx0aFP/FapyKstnIA== X-Received: by 2002:a63:7412:: with SMTP id p18mr8348417pgc.361.1581513809481; Wed, 12 Feb 2020 05:23:29 -0800 (PST) Date: Wed, 12 Feb 2020 21:23:23 +0800 Message-Id: <20200212212316.Bluez.v3.1.Ia71869d2f3e19a76a6a352c61088a085a1d41ba6@changeid> Mime-Version: 1.0 X-Mailer: git-send-email 2.25.0.225.g125e21ebc7-goog Subject: [Bluez PATCH v3] bluetooth: secure bluetooth stack from bluedump attack From: Howard Chung To: linux-bluetooth@vger.kernel.org, marcel@holtmann.org Cc: chromeos-bluetooth-upstreaming@chromium.org, Howard Chung , "David S. Miller" , Johan Hedberg , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Sender: linux-bluetooth-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org Attack scenario: 1. A Chromebook (let's call this device A) is paired to a legitimate Bluetooth classic device (e.g. a speaker) (let's call this device B). 2. A malicious device (let's call this device C) pretends to be the Bluetooth speaker by using the same BT address. 3. If device A is not currently connected to device B, device A will be ready to accept connection from device B in the background (technically, doing Page Scan). 4. Therefore, device C can initiate connection to device A (because device A is doing Page Scan) and device A will accept the connection because device A trusts device C's address which is the same as device B's address. 5. Device C won't be able to communicate at any high level Bluetooth profile with device A because device A enforces that device C is encrypted with their common Link Key, which device C doesn't have. But device C can initiate pairing with device A with just-works model without requiring user interaction (there is only pairing notification). After pairing, device A now trusts device C with a new different link key, common between device A and C. 6. From now on, device A trusts device C, so device C can at anytime connect to device A to do any kind of high-level hijacking, e.g. speaker hijack or mouse/keyboard hijack. Since we don't know whether the repairing is legitimate or not, leave the decision to user space if all the conditions below are met. - the pairing is initialized by peer - the authorization method is just-work - host already had the link key to the peer Signed-off-by: Howard Chung Acked-by: Johan Hedberg --- Changes in v3: - Change confirm_hint from 2 to 1 - Fix coding style (declaration order) Changes in v2: - Remove the HCI_PERMIT_JUST_WORK_REPAIR debugfs option - Fix the added code in classic - Add a similar fix for LE net/bluetooth/hci_event.c | 10 ++++++++++ net/bluetooth/smp.c | 18 ++++++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c index 2c833dae9366..e6982f4f51ea 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -4571,6 +4571,16 @@ static void hci_user_confirm_request_evt(struct hci_dev *hdev, goto confirm; } + /* If there already exists link key in local host, leave the + * decision to user space since the remote device could be + * legitimate or malicious. + */ + if (hci_find_link_key(hdev, &ev->bdaddr)) { + bt_dev_warn(hdev, "Local host already has link key"); + confirm_hint = 1; + goto confirm; + } + BT_DBG("Auto-accept of user confirmation with %ums delay", hdev->auto_accept_delay); diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c index 2cba6e07c02b..1483ceea3bab 100644 --- a/net/bluetooth/smp.c +++ b/net/bluetooth/smp.c @@ -2139,6 +2139,7 @@ static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb) struct l2cap_chan *chan = conn->smp; struct smp_chan *smp = chan->data; struct hci_conn *hcon = conn->hcon; + struct smp_ltk *key; u8 *pkax, *pkbx, *na, *nb; u32 passkey; int err; @@ -2192,6 +2193,23 @@ static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb) smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(smp->prnd), smp->prnd); SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK); + + key = hci_find_ltk(hcon->hdev, &hcon->dst, hcon->dst_type, + hcon->role); + + /* If there already exists link key in local host, leave the + * decision to user space since the remote device could be + * legitimate or malicious. + */ + if (smp->method == JUST_WORKS && key) { + err = mgmt_user_confirm_request(hcon->hdev, &hcon->dst, + hcon->type, + hcon->dst_type, passkey, + 1); + if (err) + return SMP_UNSPECIFIED; + set_bit(SMP_FLAG_WAIT_USER, &smp->flags); + } } mackey_and_ltk: