4.19-stable review patch. If anyone has any objections, please let me know.
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From: Lee, Chun-Yi jlee@suse.com
commit 1ffc6f8cc33268731fcf9629fc4438f6db1191fc upstream.
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]
Cc: stable@vger.kernel.org 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@suse.com Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/bluetooth/hci_conn.c | 9 +++++++++ net/bluetooth/hci_event.c | 11 +++++++++++ 2 files changed, 20 insertions(+)
--- a/net/bluetooth/hci_conn.c +++ b/net/bluetooth/hci_conn.c @@ -1204,6 +1204,15 @@ struct hci_conn *hci_connect_acl(struct 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 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); --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -2510,6 +2510,17 @@ static void hci_conn_request_evt(struct BT_DBG("%s bdaddr %pMR type 0x%x", hdev->name, &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 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);