Hi Marcel,
On Wed, May 20, 2020 at 7:23 AM Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
>
> Hi Luiz,
>
> > E0 is not allowed with Level 4:
> >
> > BLUETOOTH CORE SPECIFICATION Version 5.2 | Vol 3, Part C page 1319:
> >
> > '128-bit equivalent strength for link and encryption keys
> > required using FIPS approved algorithms (E0 not allowed,
> > SAFER+ not allowed, and P-192 not allowed; encryption key
> > not shortened'
> >
> > SC enabled:
> >
> >> HCI Event: Read Remote Extended Features (0x23) plen 13
> > Status: Success (0x00)
> > Handle: 256
> > Page: 1/2
> > Features: 0x0b 0x00 0x00 0x00 0x00 0x00 0x00 0x00
> > Secure Simple Pairing (Host Support)
> > LE Supported (Host)
> > Secure Connections (Host Support)
> >> HCI Event: Encryption Change (0x08) plen 4
> > Status: Success (0x00)
> > Handle: 256
> > Encryption: Enabled with AES-CCM (0x02)
> >
> > SC disabled:
> >
> >> HCI Event: Read Remote Extended Features (0x23) plen 13
> > Status: Success (0x00)
> > Handle: 256
> > Page: 1/2
> > Features: 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00
> > Secure Simple Pairing (Host Support)
> > LE Supported (Host)
> >> HCI Event: Encryption Change (0x08) plen 4
> > Status: Success (0x00)
> > Handle: 256
> > Encryption: Enabled with E0 (0x01)
> > [May 8 20:23] Bluetooth: hci0: Invalid security: expect AES but E0 was used
> > < HCI Command: Disconnect (0x01|0x0006) plen 3
> > Handle: 256
> > Reason: Authentication Failure (0x05)
> >
> > Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
> > ---
> > net/bluetooth/hci_conn.c | 17 +++++++++++++++++
> > net/bluetooth/hci_event.c | 6 ++----
> > 2 files changed, 19 insertions(+), 4 deletions(-)
> >
> > diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> > index 07c34c55fc50..0c1cae83c8dc 100644
> > --- a/net/bluetooth/hci_conn.c
> > +++ b/net/bluetooth/hci_conn.c
> > @@ -1325,6 +1325,23 @@ int hci_conn_check_link_mode(struct hci_conn *conn)
> > return 0;
> > }
> >
> > + /* AES encryption is required for Level 4:
> > + *
> > + * BLUETOOTH CORE SPECIFICATION Version 5.2 | Vol 3, Part C
> > + * page 1319:
> > + *
> > + * 128-bit equivalent strength for link and encryption keys
> > + * required using FIPS approved algorithms (E0 not allowed,
> > + * SAFER+ not allowed, and P-192 not allowed; encryption key
> > + * not shortened)
> > + */
> > + if (conn->sec_level == BT_SECURITY_FIPS &&
> > + !test_bit(HCI_CONN_AES_CCM, &conn->flags)) {
> > + bt_dev_err(conn->hdev, "Invalid security: expect AES but E0 "
> > + "was used");
>
> make this bt_dev_warn since it is something that can happen. We fail appropriately now. Also try to fit the error in a single line. “Invalid security: Missing AES-CCM usage”.
Sure will update this.
> > + return 0;
> > + }
> > +
> > if (hci_conn_ssp_enabled(conn) &&
> > !test_bit(HCI_CONN_ENCRYPT, &conn->flags))
> > return 0;
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index 006c24e04b44..dc1cc3c4348c 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -3078,10 +3078,8 @@ static void hci_encrypt_change_evt(struct hci_dev *hdev, struct sk_buff *skb)
> > * that are not encrypted with AES-CCM using a P-256 authenticated
> > * combination key.
> > */
> > - if (hci_dev_test_flag(hdev, HCI_SC_ONLY) &&
> > - (!test_bit(HCI_CONN_AES_CCM, &conn->flags) ||
> > - conn->key_type != HCI_LK_AUTH_COMBINATION_P256)) {
> > - hci_connect_cfm(conn, HCI_ERROR_AUTH_FAILURE);
> > + if (!hci_conn_check_link_mode(conn)) {
> > + hci_disconnect(conn, HCI_ERROR_AUTH_FAILURE);
>
> Why is this a disconnect now? If this is better, then this needs to be explained above, but I have the feeling we really want to respond to the connect request in a clean fashion.
While testing this I discover that calling connect_cfm doesn't
actually cause a disconnect, at least not immediately, and by
disconnecting it actually provides the right error to the remote. Note
that there is a similar usage in the if statement right above this
code, but I believe that even in case we want to cleanup the earlier
what we should be calling is hci_encrypt_cfm.
> > hci_conn_drop(conn);
> > goto unlock;
>
> Regards
>
> Marcel
>
--
Luiz Augusto von Dentz
