Hi Chun-Yi, On Fri, Jul 14, 2023 at 9:14 AM Lee, Chun-Yi <joeyli.kernel@xxxxxxxxx> wrote: > > 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. Base on the paper, attacker can induce the > attacked target to generate null link key (zero key) without PIN code. > > 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] > > Closes: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-26555 [1] > Closes: https://ieeexplore.ieee.org/abstract/document/9474325/authors#authors [2] > Closes: https://github.com/bluekitchen/btstack/blob/master/src/hci.c#L3722 [3] Shouldn't the last 2 be using Link: instead? > Signed-off-by: "Lee, Chun-Yi" <jlee@xxxxxxxx> > --- > net/bluetooth/hci_event.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > index 95816a938cea..e81b8d6c13ba 100644 > --- a/net/bluetooth/hci_event.c > +++ b/net/bluetooth/hci_event.c > @@ -4684,6 +4684,12 @@ static void hci_link_key_notify_evt(struct hci_dev *hdev, void *data, > bool persistent; > u8 pin_len = 0; > > + /* Ignore NULL link key against CVE-2020-26555 */ > + if (!memcmp(ev->link_key, ZERO_KEY, HCI_LINK_KEY_SIZE)) { > + BT_DBG("Ignore NULL link key (ZERO KEY) for %pMR", &ev->bdaddr); Please use bt_dev_dbg instead. > + return; > + } > + > bt_dev_dbg(hdev, ""); > > hci_dev_lock(hdev); > -- > 2.35.3 > -- Luiz Augusto von Dentz
