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)?
If not then we might want to add a socket option to set min/max encryption key size requirement on a per socket basis.
Regards
Marcel
