From mboxrd@z Thu Jan 1 00:00:00 1970 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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no 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 EBFE0C3B19F for ; Fri, 14 Feb 2020 14:58:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C284724649 for ; Fri, 14 Feb 2020 14:58:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729508AbgBNO6j (ORCPT ); Fri, 14 Feb 2020 09:58:39 -0500 Received: from coyote.holtmann.net ([212.227.132.17]:37432 "EHLO mail.holtmann.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729241AbgBNO6i (ORCPT ); Fri, 14 Feb 2020 09:58:38 -0500 Received: from marcel-macbook.fritz.box (p4FEFC5A7.dip0.t-ipconnect.de [79.239.197.167]) by mail.holtmann.org (Postfix) with ESMTPSA id 3FA2ACECE6; Fri, 14 Feb 2020 16:08:00 +0100 (CET) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3608.60.0.2.5\)) Subject: Re: [Bluez PATCH v5] bluetooth: secure bluetooth stack from bluedump attack From: Marcel Holtmann In-Reply-To: <20200214191609.Bluez.v5.1.Ia71869d2f3e19a76a6a352c61088a085a1d41ba6@changeid> Date: Fri, 14 Feb 2020 15:58:36 +0100 Cc: Bluez mailing list , chromeos-bluetooth-upstreaming@chromium.org, "David S. Miller" , Johan Hedberg , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit Message-Id: References: <20200214191609.Bluez.v5.1.Ia71869d2f3e19a76a6a352c61088a085a1d41ba6@changeid> To: Howard Chung X-Mailer: Apple Mail (2.3608.60.0.2.5) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Howard, > 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(+) patch has been applied to bluetooth-next tree. Regards Marcel