From patchwork Mon Feb 17 04:05:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Howard Chung X-Patchwork-Id: 11385167 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 C4C7E1395 for ; Mon, 17 Feb 2020 04:05:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9669B2072C for ; Mon, 17 Feb 2020 04:05:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="SJ77Fa0b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727889AbgBQEFR (ORCPT ); Sun, 16 Feb 2020 23:05:17 -0500 Received: from mail-pg1-f201.google.com ([209.85.215.201]:40136 "EHLO mail-pg1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726498AbgBQEFO (ORCPT ); Sun, 16 Feb 2020 23:05:14 -0500 Received: by mail-pg1-f201.google.com with SMTP id n7so10873339pgt.7 for ; Sun, 16 Feb 2020 20:05:12 -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=KMuOOh+un+YCPFr8b6yeijMH6rF3UsQjfTXq1dL+TiU=; b=SJ77Fa0bkktg3YOKVByovnXj1UUsGEqdC5K+iVXXrTrxzeIRcidVk/fb4NFEOOfdL9 s0Yu+L/nPWd7PXyqy09zpbxxm189pl7CeTweBTyyoz6p4FiNHjBNF49IpkdGiI3xYYwI b+plMsujhnnabbL5x7aybaprN4E2Sc/Z+F5EPRIYi3Gs4s8da0aNsQeL5B/DXstv1jfq hUMPBwt5R9Idh1OSifE2GZJjuozkR0R5obF1KZXr15l7gnJOJ+svm4z2mM9xV5UCCypd OF5WWC8exZ8FxkPaU/qsEXC7fokFwlJ5zInZGF5vWYxkNGPbyLBSrCshThNm89/PAXZZ UgqA== 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=KMuOOh+un+YCPFr8b6yeijMH6rF3UsQjfTXq1dL+TiU=; b=jIa9VPZv656f1YIPUdGhpqwZJJQoGWOacS1ZzmCS5NAxqf94E2408GYYjG/T+JAQjn X5XK9BcNcfWvIy1RDFOVl4UDzhyUPgLTQaKyUgrd42KrgbmsWCMJ0TS3SqpZFudl+QW8 5oDS1OVHJF8OnI0SotPlmSsOAjurR/GhdUmuxlco1ii3bAMS+ncVvQv9bZAnT0B2vlG2 tyihOoENxBTfUqTTtjKMHA31ixvMv9qe73+5Fxv8zAAZZmiYtp9NCufsSYhEAMKSiklM Vef49H7l2qEG0g/i3S7z+iYFv+eBOJwEOH3jHUrjKlpkOgxHKlGmHyQgI4ho2LMs6tOv r76Q== X-Gm-Message-State: APjAAAWcDXpmOtughpoawOObZIaOHKCzkMT93sv9j01R56giDHY/0W+i BgTTb5LTLjOMVt01TpLU84XPObVBAl943U0tENEEhmR/fQJaGeS6gMNOr68Xol0w1/0NQQGGspm nrP2W/o1i6bRQDljAqKJw6y6tqCjDC6RLrakqaCUbVxZyqDkOjTAX99WwrLg4XK5X4T/y2P9ptG C4TMrAZrC7Bqk= X-Google-Smtp-Source: APXvYqwzecOqFqAQbDjGxkj8H9g1SfJhMVodrpAyj+HwltbP1RJUNeMBDIJ9Xo+HM4GK8bjoqzV6361fiRur36qs1g== X-Received: by 2002:a63:d18:: with SMTP id c24mr15930889pgl.218.1581912312201; Sun, 16 Feb 2020 20:05:12 -0800 (PST) Date: Mon, 17 Feb 2020 12:05:03 +0800 Message-Id: <20200217120454.Bluez.v6.1.Ia71869d2f3e19a76a6a352c61088a085a1d41ba6@changeid> Mime-Version: 1.0 X-Mailer: git-send-email 2.25.0.265.gbab2e86ba0-goog Subject: [Bluez PATCH v6] 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 v6: - Fix passkey uninitialized issue 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 | 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..2b6fb7454add 100644 --- a/net/bluetooth/smp.c +++ b/net/bluetooth/smp.c @@ -2192,6 +2192,24 @@ 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, 0, 1); + if (err) + return SMP_UNSPECIFIED; + set_bit(SMP_FLAG_WAIT_USER, &smp->flags); + } } mackey_and_ltk: