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Sun, 01 Oct 2023 00:48:42 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1778557641324145598 X-GMAIL-MSGID: 1778557641324145598 This change is used to relieve CVE-2020-26555. 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 95816a938cea..a20a94e85b1a 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -4692,6 +4692,14 @@ 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); -- 2.35.3 From 5fed42878147cffa22e695732d87a85c218d217f Mon Sep 17 00:00:00 2001 From: "Lee, Chun-Yi" Date: Fri, 14 Jul 2023 21:14:01 +0800 Subject: [PATCH 1/2] Bluetooth: hci_event: Ignore NULL link key In-Reply-To: <20231001074524.GA14361@linux-691t> References: <20231001074524.GA14361@linux-691t> This change is used to relieve CVE-2020-26555. 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 95816a938cea..a20a94e85b1a 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -4692,6 +4692,14 @@ 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);