Re: [RFC] Bluetooth: Check key sizes only when Secure Simple Pairing is enabled

[Vasily Khoruzhick <anarsoul@gmail.com>]

On Wed, May 22, 2019 at 12:05 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> The encryption is only mandatory to be enforced when both sides are using
> Secure Simple Pairing and this means the key size check makes only sense
> in that case.
>
> On legacy Bluetooth 2.0 and earlier devices like mice the encryption was
> optional and thus causing an issue if the key size check is not bound to
> using Secure Simple Pairing.
>
> Fixes: d5bb334a8e17 ("Bluetooth: Align minimum encryption key size for LE and BR/EDR connections")
> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
> Cc: stable@vger.kernel.org

Tested-by: Vasily Khoruzhick <anarsoul@gmail.com>

> ---
>  net/bluetooth/hci_conn.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index 3cf0764d5793..7516cdde3373 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -1272,8 +1272,13 @@ int hci_conn_check_link_mode(struct hci_conn *conn)
>                         return 0;
>         }
>
> -       if (hci_conn_ssp_enabled(conn) &&
> -           !test_bit(HCI_CONN_ENCRYPT, &conn->flags))
> +       /* If Secure Simple Pairing is not enabled, then legacy connection
> +        * setup is used and no encryption or key sizes can be enforced.
> +        */
> +       if (!hci_conn_ssp_enabled(conn))
> +               return 1;
> +
> +       if (!test_bit(HCI_CONN_ENCRYPT, &conn->flags))
>                 return 0;
>
>         /* The minimum encryption key size needs to be enforced by the
> --
> 2.20.1
>