Bluetooth: SMP: Fail if remote and local public keys are identical

This fails the pairing procedure when both remote and local non-debug
public keys are identical.
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/smp.c

@@ -2732,6 +2732,15 @@ static int smp_cmd_public_key(struct l2cap_conn *conn, struct sk_buff *skb)
 	if (skb->len < sizeof(*key))
 		return SMP_INVALID_PARAMS;
 
+	/* Check if remote and local public keys are the same and debug key is
+	 * not in use.
+	 */
+	if (!test_bit(SMP_FLAG_DEBUG_KEY, &smp->flags) &&
+	    !crypto_memneq(key, smp->local_pk, 64)) {
+		bt_dev_err(hdev, "Remote and local public keys are identical");
+		return SMP_UNSPECIFIED;
+	}
+
 	memcpy(smp->remote_pk, key, 64);
 
 	if (test_bit(SMP_FLAG_REMOTE_OOB, &smp->flags)) {