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. A condition of this attack is that attacker should change the BR_ADDR of his hacking device (Host B) to equal to the BR_ADDR with the target device being attacked (Host A). Thus, we reject the connection with device which has same BD_ADDR both on HCI_Create_Connection and HCI_Connection_Request to prevent the attack. A similar implementation also shows in btstack project. [3][4] 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#L3523 [3] Link: https://github.com/bluekitchen/btstack/blob/master/src/hci.c#L7297 [4] Signed-off-by: Lee, Chun-Yi <jlee@xxxxxxxx> --- net/bluetooth/hci_conn.c | 7 +++++++ net/bluetooth/hci_event.c | 8 ++++++++ 2 files changed, 15 insertions(+) diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c index 9d5057cef30a..21c831f1fec6 100644 --- a/net/bluetooth/hci_conn.c +++ b/net/bluetooth/hci_conn.c @@ -1627,6 +1627,13 @@ struct hci_conn *hci_connect_acl(struct hci_dev *hdev, bdaddr_t *dst, return ERR_PTR(-EOPNOTSUPP); } + /* Reject outgoing connection to device with same BD ADDR against CVE-2020-26555 */ + if (!bacmp(&hdev->bdaddr, dst)) + { + bt_dev_dbg(hdev, "Reject connection to the device with same BD_ADDR %pMR\n", dst); + return ERR_PTR(-ECONNREFUSED); + } + acl = hci_conn_hash_lookup_ba(hdev, ACL_LINK, dst); if (!acl) { acl = hci_conn_add(hdev, ACL_LINK, dst, HCI_ROLE_MASTER); diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c index 2830abbdd329..df97dd64be6a 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -3267,6 +3267,14 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data, bt_dev_dbg(hdev, "bdaddr %pMR type 0x%x", &ev->bdaddr, ev->link_type); + /* Reject incoming connection from device with same BD ADDR against CVE-2020-26555 */ + if (!bacmp(&hdev->bdaddr, &ev->bdaddr)) + { + bt_dev_dbg(hdev, "Reject connection from the device with same BD_ADDR %pMR\n", &ev->bdaddr); + hci_reject_conn(hdev, &ev->bdaddr); + return; + } + mask |= hci_proto_connect_ind(hdev, &ev->bdaddr, ev->link_type, &flags); -- 2.35.3
