Hi Marcel,
On Fri, Feb 26, 2021 at 12:23 PM Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
>
> Hi Magdalena,
>
> > This is required for the qualification test L2CAP/LE/CFC/BV-15-C
> >
> > Implementation does not allow to set different key size for SMP and
> > L2CAP, which is needed for a current specification of the test. This fix
> > workarounds it with the debugfs variable le_l2cap_min_key_size.
> >
> > Logs from the test when the IUT uses a min and max l2cap encryption key size 16.
> > $ echo 16 > /sys/kernel/debug/bluetooth/hci0/le_l2cap_min_key_size
> > The lower tester uses a key size 7.
> >
> >> ACL Data RX: Handle 99 flags 0x02 dlen 11 #34 [hci0] 25.007392
> > SMP: Pairing Request (0x01) len 6
> > IO capability: DisplayYesNo (0x01)
> > OOB data: Authentication data not present (0x00)
> > Authentication requirement: Bonding, No MITM, SC, No Keypresses (0x09)
> > Max encryption key size: 7
> > Initiator key distribution: <none> (0x00)
> > Responder key distribution: <none> (0x00)
> > < ACL Data TX: Handle 99 flags 0x00 dlen 11 #35 [hci0] 25.007591
> > SMP: Pairing Response (0x02) len 6
> > IO capability: KeyboardDisplay (0x04)
> > OOB data: Authentication data not present (0x00)
> > Authentication requirement: Bonding, No MITM, SC, No Keypresses (0x09)
> > Max encryption key size: 16
> > Initiator key distribution: <none> (0x00)
> > Responder key distribution: <none> (0x00)
> > @ MGMT Event: New Long Term Key (0x000a) plen 37 {0x0001} [hci0] 28.788872
> > Store hint: Yes (0x01)
> > LE Address: C0:DE:C0:FF:FF:01 (OUI C0-DE-C0)
> > Key type: Unauthenticated key from P-256 (0x02)
> > Master: 0x00
> > Encryption size: 7
> > Diversifier: 0000
> > Randomizer: 0000000000000000
> > Key: 529e11e8c7b9f5000000000000000000
> >
> > <snip>
> >
> > After pairing with key size 7, L2CAP connection is requested which
> > requires key size 16.
> >
> >> ACL Data RX: Handle 99 flags 0x02 dlen 18 #56 [hci0] 34.998084
> > LE L2CAP: LE Connection Request (0x14) ident 3 len 10
> > PSM: 244 (0x00f4)
> > Source CID: 64
> > MTU: 256
> > MPS: 284
> > Credits: 1
> > < ACL Data TX: Handle 99 flags 0x00 dlen 18 #57 [hci0] 34.998325
> > LE L2CAP: LE Connection Response (0x15) ident 3 len 10
> > Destination CID: 0
> > MTU: 0
> > MPS: 0
> > Credits: 0
> > Result: Connection refused - insufficient encryption key size (0x0007)
> >
> > Signed-off-by: Magdalena Kasenberg <magdalena.kasenberg@xxxxxxxxxxx>
> > Reviewed-by: Szymon Janc <szymon.janc@xxxxxxxxxxx>
> > Cc: Szymon Janc <szymon.janc@xxxxxxxxxxx>
> > ---
> > include/net/bluetooth/hci_core.h | 1 +
> > net/bluetooth/hci_core.c | 1 +
> > net/bluetooth/hci_debugfs.c | 30 ++++++++++++++++++++++++++++++
> > net/bluetooth/l2cap_core.c | 25 +++++++++++++++++++++++++
> > 4 files changed, 57 insertions(+)
> >
> > diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
> > index ebdd4afe30d2..0bf0543efec5 100644
> > --- a/include/net/bluetooth/hci_core.h
> > +++ b/include/net/bluetooth/hci_core.h
> > @@ -379,6 +379,7 @@ struct hci_dev {
> > __u16 auth_payload_timeout;
> > __u8 min_enc_key_size;
> > __u8 max_enc_key_size;
> > + __u8 le_l2cap_min_key_size;
> > __u8 pairing_opts;
> > __u8 ssp_debug_mode;
> > __u8 hw_error_code;
> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > index b0d9c36acc03..9ef4b39b380c 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -3788,6 +3788,7 @@ struct hci_dev *hci_alloc_dev(void)
> > hdev->conn_info_max_age = DEFAULT_CONN_INFO_MAX_AGE;
> > hdev->auth_payload_timeout = DEFAULT_AUTH_PAYLOAD_TIMEOUT;
> > hdev->min_enc_key_size = HCI_MIN_ENC_KEY_SIZE;
> > + hdev->le_l2cap_min_key_size = HCI_MIN_ENC_KEY_SIZE;
>
> so I am not a fan of doing this with another variable and managing through debugfs. Can we pass the qualification test case by using BT_SECURITY_FIPS (which will enforce 128-bit key size)?
I guess that will depend if PTS supports MITM which afaik it is
required with BT_SECURITY_FIPS, from the logs it looks like it doesn't
support it so we end up with an unauthenticated key so the error would
probably be different.
> If not then we might want to add a socket option to set min/max encryption key size requirement on a per socket basis.
Yep, it seems to be a common trend to have such tests on upper layers
(ATT/GATT also have such encryption key size), even though it is more
of a GAP test and perhaps could have been done at SMP level.
>
> Regards
>
> Marcel
>
--
Luiz Augusto von Dentz
