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Sun, 1 Oct 2023 08:54:03 +0000 Received: from DB8PR04MB7164.eurprd04.prod.outlook.com ([fe80::8647:4673:b19:acc2]) by DB8PR04MB7164.eurprd04.prod.outlook.com ([fe80::8647:4673:b19:acc2%4]) with mapi id 15.20.6813.027; Sun, 1 Oct 2023 08:54:03 +0000 Date: Sun, 1 Oct 2023 16:53:52 +0800 From: "Lee, Chun-Yi" To: Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz Cc: linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org Subject: [PATCH 1/2] Bluetooth: hci_event: Ignore NULL link key Message-ID: <20231001084934.GA16906@linux-691t> References: <20231001084934.GA16906@linux-691t> Content-Disposition: inline User-Agent: Mutt/1.11.4 (2019-03-13) X-ClientProxiedBy: TYCPR01CA0181.jpnprd01.prod.outlook.com (2603:1096:400:2b0::10) To DB8PR04MB7164.eurprd04.prod.outlook.com (2603:10a6:10:129::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DB8PR04MB7164:EE_|VI1PR04MB10050:EE_ X-MS-Office365-Filtering-Correlation-Id: 3d99cf5a-1704-4e7d-30a0-08dbc25bf5f5 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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The description of the CVE: Bluetooth legacy BR/EDR PIN code pairing in Bluetooth Core Specification 1.0B through 5.2 may permit an unauthenticated nearby device to spoof the BD_ADDR of the peer device to complete pairing without knowledge of the PIN. [1] The detail of this attack is in IEEE paper: BlueMirror: Reflections on Bluetooth Pairing and Provisioning Protocols [2] It's a reflection attack. The paper mentioned that attacker can induce the attacked target to generate null link key (zero key) without PIN code. In BR/EDR, the key generation is actually handled in the controller which is below HCI. Thus, we can ignore null link key in the handler of "Link Key Notification event" to relieve the attack. A similar implementation also shows in btstack project. [3] v3: Drop the connection when null link key be detected. v2: - Used Link: tag instead of Closes: - Used bt_dev_dbg instead of BT_DBG - Added Fixes: tag Fixes: 55ed8ca10f35 ("Bluetooth: Implement link key handling for the management interface") Link: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-26555 [1] Link: https://ieeexplore.ieee.org/abstract/document/9474325/authors#authors [2] Link: https://github.com/bluekitchen/btstack/blob/master/src/hci.c#L3722 [3] Signed-off-by: Lee, Chun-Yi --- net/bluetooth/hci_event.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c index 35f251041eeb..2830abbdd329 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -4741,6 +4741,14 @@ static void hci_link_key_notify_evt(struct hci_dev *hdev, void *data, if (!conn) goto unlock; + /* Ignore NULL link key against CVE-2020-26555 */ + if (!memcmp(ev->link_key, ZERO_KEY, HCI_LINK_KEY_SIZE)) { + bt_dev_dbg(hdev, "Ignore NULL link key (ZERO KEY) for %pMR", &ev->bdaddr); + hci_disconnect(conn, HCI_ERROR_AUTH_FAILURE); + hci_conn_drop(conn); + goto unlock; + } + hci_conn_hold(conn); conn->disc_timeout = HCI_DISCONN_TIMEOUT; hci_conn_drop(conn);