Hi Luiz,
>>> 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.
we should give this a try ..
>
>> 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.
.. however maybe we just deprecate BT_SECURITY or migrate it into something that allows specifying the details of a security level with extra parameters. I made the BT_SECURITY implementation in the kernel extendable. So we could also just add extra possible settings.
Regards
Marcel
