From patchwork Fri Feb 14 11:16:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Howard Chung X-Patchwork-Id: 11382115 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 E840C13A4 for ; Fri, 14 Feb 2020 11:16:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC9FC222C4 for ; Fri, 14 Feb 2020 11:16:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="iQAkM9Mj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729229AbgBNLQv (ORCPT ); Fri, 14 Feb 2020 06:16:51 -0500 Received: from mail-vs1-f73.google.com ([209.85.217.73]:37212 "EHLO mail-vs1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728522AbgBNLQu (ORCPT ); Fri, 14 Feb 2020 06:16:50 -0500 Received: by mail-vs1-f73.google.com with SMTP id n129so675205vsd.4 for ; Fri, 14 Feb 2020 03:16:48 -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=c3okqhGXbbn+0UGnWI89nn927kUSh19dp4ivRMVKM2U=; b=iQAkM9MjICHpGcWO1za9HTHfLgysGmX4AvNhv0qrE8Eyc53ngdh1T8OpbzVHWkZ0fo KXNxqzuGBpFGVRu6EGDu2mxLR0mSVHjrqSUBirnlt6TtXajhTXSJzPQN561gCblVT/Bm d9O2k3B5DaTnJAJp0+Uqkkj3DsaCIjuER6vwEbnL9WeFAg5PoyCzy6tVwlZ0NRSe6DXP a6wDsljFgIyHhEKyFUHsfdZgua/fcyGPgCG3RcScdrCZTj6P15ukbzTPk6xjHhIjHzo/ +3bn0EzWxXjzTivBC5zTYDoqdIGI63+qWx2PwA0Qdm2jglKCm5R1JWJPtZISzQNrKglc jexQ== 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=c3okqhGXbbn+0UGnWI89nn927kUSh19dp4ivRMVKM2U=; b=Fvj5LmY/dahIk5AXIWjsmp5R/YHA+RYonSN10UH4v7ct5FizbJX5DLPWu4tvE8DV50 Hmu8mJabbwv78IEJ5chVCKJ62GhdMfRHKW51TGrY30Af1t5Sgqy3LYB4fzXa77c5yLWa k11u41uUlYDY2NMRJ3grJ1UDNBBZqX/q2joAi2C7w3PRitx8YIssOmk+kYziXBz2BNW8 BNskDn4kP7VPDjIEYjvK388sMJs1gNMNdayW8bBL7IzbdFxyACshxvMmHIL6Q69+sDZR lKdn3wr4nVu3QhPetYgusQvPCK+sQLUKIJqvDi2MP3yrzS7pr+SLCWpTfwBVi6vI7tWT TQcA== X-Gm-Message-State: APjAAAWvi7jGQ1KJqIxkmXq7ct4fKaVhBWVFzJI2nzokiD3AeRKhqE5s CWsg7JY/OA8F/qQ/WgDRvJNdu75prHThBTyYkZG+uBjmIY6NjLmzNDrKBoOCdd7u4C2tLDN2SD8 gX24KDwnrvuTvFuFr9JKM2+ue4BHVnn1c3MC+7pEnsKFFOeuPDRUrxagq0i9bq94s9LkxqyxuX2 QKzC+dFx/3sNk= X-Google-Smtp-Source: APXvYqzsIA3nUi3NBbhp5dI9jRoSYsoMZCDaMZ07OVCCBOj8uKzTu0JiMAsaZ8k19Z0h13CTZjvl3d3xNuD/pHp54g== X-Received: by 2002:ab0:2859:: with SMTP id c25mr1216302uaq.79.1581679007748; Fri, 14 Feb 2020 03:16:47 -0800 (PST) Date: Fri, 14 Feb 2020 19:16:41 +0800 Message-Id: <20200214191609.Bluez.v5.1.Ia71869d2f3e19a76a6a352c61088a085a1d41ba6@changeid> Mime-Version: 1.0 X-Mailer: git-send-email 2.25.0.265.gbab2e86ba0-goog Subject: [Bluez PATCH v5] 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 --- Changes in v5: - Rephrase the comment Changes in v4: - optimise the check in smp.c. 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 | 19 +++++++++++++++++++ 2 files changed, 29 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..25dbf77d216b 100644 --- a/net/bluetooth/smp.c +++ b/net/bluetooth/smp.c @@ -2192,6 +2192,25 @@ 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); + + /* Only Just-Works pairing requires extra checks */ + if (smp->method != JUST_WORKS) + goto mackey_and_ltk; + + /* 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_ltk(hcon->hdev, &hcon->dst, hcon->dst_type, + hcon->role)) { + 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: