5.4-stable review patch. If anyone has any objections, please let me know.
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From: Lee, Chun-Yi jlee@suse.com
commit 33155c4aae5260475def6f7438e4e35564f4f3ba 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.
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
Cc: stable@vger.kernel.org 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 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_event.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -3935,6 +3935,15 @@ static void hci_link_key_notify_evt(stru 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);