@@ -4571,6 +4571,16 @@ static void hci_user_confirm_request_evt(struct hci_dev *hdev,
goto confirm;
}
+ /* If there already exists link key in local host, leave the
+ * decision to user space since the remote device could be
+ * legitimate or malicious.
+ */
+ if (hci_find_link_key(hdev, &ev->bdaddr)) {
+ bt_dev_warn(hdev, "Local host already has link key");
+ confirm_hint = 1;
+ goto confirm;
+ }
+
BT_DBG("Auto-accept of user confirmation with %ums delay",
hdev->auto_accept_delay);
@@ -2139,6 +2139,7 @@ static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
struct l2cap_chan *chan = conn->smp;
struct smp_chan *smp = chan->data;
struct hci_conn *hcon = conn->hcon;
+ struct smp_ltk *key;
u8 *pkax, *pkbx, *na, *nb;
u32 passkey;
int err;
@@ -2192,6 +2193,23 @@ static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(smp->prnd),
smp->prnd);
SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
+
+ key = hci_find_ltk(hcon->hdev, &hcon->dst, hcon->dst_type,
+ hcon->role);
+
+ /* If there already exists link key in local host, leave the
+ * decision to user space since the remote device could be
+ * legitimate or malicious.
+ */
+ if (smp->method == JUST_WORKS && key) {
+ err = mgmt_user_confirm_request(hcon->hdev, &hcon->dst,
+ hcon->type,
+ hcon->dst_type, passkey,
+ 1);
+ if (err)
+ return SMP_UNSPECIFIED;
+ set_bit(SMP_FLAG_WAIT_USER, &smp->flags);
+ }
}
mackey_and_ltk:
Attack scenario: 1. A Chromebook (let's call this device A) is paired to a legitimate Bluetooth classic device (e.g. a speaker) (let's call this device B). 2. A malicious device (let's call this device C) pretends to be the Bluetooth speaker by using the same BT address. 3. If device A is not currently connected to device B, device A will be ready to accept connection from device B in the background (technically, doing Page Scan). 4. Therefore, device C can initiate connection to device A (because device A is doing Page Scan) and device A will accept the connection because device A trusts device C's address which is the same as device B's address. 5. Device C won't be able to communicate at any high level Bluetooth profile with device A because device A enforces that device C is encrypted with their common Link Key, which device C doesn't have. But device C can initiate pairing with device A with just-works model without requiring user interaction (there is only pairing notification). After pairing, device A now trusts device C with a new different link key, common between device A and C. 6. From now on, device A trusts device C, so device C can at anytime connect to device A to do any kind of high-level hijacking, e.g. speaker hijack or mouse/keyboard hijack. Since we don't know whether the repairing is legitimate or not, leave the decision to user space if all the conditions below are met. - the pairing is initialized by peer - the authorization method is just-work - host already had the link key to the peer Signed-off-by: Howard Chung <howardchung@google.com> --- Changes in v3: - Change confirm_hint from 2 to 1 - Fix coding style (declaration order) Changes in v2: - Remove the HCI_PERMIT_JUST_WORK_REPAIR debugfs option - Fix the added code in classic - Add a similar fix for LE net/bluetooth/hci_event.c | 10 ++++++++++ net/bluetooth/smp.c | 18 ++++++++++++++++++ 2 files changed, 28 insertions(+)