Re: [PATCH 1/8] Bluetooth: Add structures for the new LTK exchange messages

[Brian Gix <bgix@codeaurora.org>]

Hi Vinicius,

On 12/6/2011 4:48 PM, Vinicius Costa Gomes wrote:
> This defines two in the kernel side of BlueZ two new messages, one
> event that will inform userspace that a new Long Term Key was
> exchanged and one that will allow userspace to load LTKs into
> the kernel.
>
> Acked-by: Marcel Holtmann<marcel@holtmann.org>
> Signed-off-by: Vinicius Costa Gomes<vinicius.gomes@openbossa.org>
> ---
>   include/net/bluetooth/mgmt.h |   21 +++++++++++++++++++++
>   1 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/include/net/bluetooth/mgmt.h b/include/net/bluetooth/mgmt.h
> index 3b68806..0f100fa9 100644
> --- a/include/net/bluetooth/mgmt.h
> +++ b/include/net/bluetooth/mgmt.h
> @@ -264,6 +264,21 @@ struct mgmt_cp_user_passkey_neg_reply {
>   	bdaddr_t bdaddr;
>   } __packed;
>
> +struct mgmt_ltk_info {
> +	bdaddr_t bdaddr;
> +	__u8 pin_len;
> +	__u8 enc_size;
> +	__le16 ediv;
> +	__u8 rand[8];
> +	__u8 val[16];
> +} __packed;

I think we definitely want to store the auth level (octet) that was used 
to generate this key and/or the sec_level. Some profiles may require 
MITM (high sec_level) and from this key definition, there is no way to 
tell if it is Medium (no MITM) or High.

This then needs to be used L2CAP to map the sock options, and 
potentially trigger a re-bonding.  Not that it is likely to happen, 
since devices are suppose to pair with the Highest security level they 
have available, but there could be malicious devices which could gain 
access to "High" security services without performing MITM authentication.

Also, I will harp once again that anything with an LE bdaddr should 
include the Public vs Random flag because the two address types are 
*not* interchangeable.  I would like to see Johan's "mgmt_addr_info" 
structure used in place of the bdaddr_t here.


> +
> +#define MGMT_OP_LOAD_LONG_TERM_KEYS	0x0023
> +struct mgmt_cp_load_long_term_keys {
> +	__u16 key_count;
> +	struct mgmt_ltk_info keys[0];
> +} __packed;
> +
>   #define MGMT_EV_CMD_COMPLETE		0x0001
>   struct mgmt_ev_cmd_complete {
>   	__le16 opcode;
> @@ -363,3 +378,9 @@ struct mgmt_ev_device_unblocked {
>   struct mgmt_ev_user_passkey_request {
>   	bdaddr_t bdaddr;
>   } __packed;
> +
> +#define MGMT_EV_NEW_LONG_TERM_KEY	0x0018
> +struct mgmt_ev_new_long_term_key {
> +	__u8 store_hint;
> +	struct mgmt_ltk_info key;
> +} __packed;


-- 
Brian Gix
bgix@codeaurora.org
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum