Hi Brian,
On Tue, Dec 20, 2011 at 05:04:41PM -0800, Brian Gix wrote:
> To achive Man-In-The-Middle (MITM) level security with Low Energy,
> we have to enable User Passkey Comparison. This commit modifies the
> hard-coded JUST-WORKS pairing mechanism to support query via the MGMT
> interface of Passkey comparison and User Confirmation.
>
> Signed-off-by: Brian Gix <bgix@xxxxxxxxxxxxxx>
> ---
> include/net/bluetooth/hci_core.h | 1 +
> include/net/bluetooth/smp.h | 5 +
> net/bluetooth/smp.c | 227 ++++++++++++++++++++++++++++++++++----
> 3 files changed, 211 insertions(+), 22 deletions(-)
...
> +static int tk_request(struct l2cap_conn *conn, u8 remote_oob, u8 auth,
> + u8 local_io, u8 remote_io)
> +{
> + struct hci_conn *hcon = conn->hcon;
> + struct smp_chan *smp = conn->smp_chan;
> + u8 method;
> + u32 passkey = 0;
> + int ret = 0;
> +
> + /* Initialize key to JUST WORKS */
> + memset(smp->tk, 0, sizeof(smp->tk));
> + clear_bit(SMP_FLAG_TK_VALID, &smp->smp_flags);
> +
> + BT_DBG("tk_request: auth:%d lcl:%d rem:%d", auth, local_io, remote_io);
> +
> + /* If neither side wants MITM, use JUST WORKS */
> + /* If either side has unknown io_caps, use JUST_WORKS */
> + if (!(auth & SMP_AUTH_MITM) ||
> + local_io > SMP_IO_KEYBOARD_DISPLAY ||
> + remote_io > SMP_IO_KEYBOARD_DISPLAY) {
> + auth &= ~SMP_AUTH_MITM;
> + set_bit(SMP_FLAG_TK_VALID, &smp->smp_flags);
> + return 0;
> + }
> +
> + /* MITM is now officially requested, but not required */
> + /* Determine what we need (if anything) from the agent */
> + method = gen_method[local_io][remote_io];
> +
> + if (method == JUST_WORKS || method == JUST_CFM)
> + auth &= ~SMP_AUTH_MITM;
> +
> + /* Don't bother confirming unbonded JUST_WORKS */
> + if (!(auth & SMP_AUTH_BONDING) && method == JUST_CFM) {
> + set_bit(SMP_FLAG_TK_VALID, &smp->smp_flags);
> + return 0;
> + } else if (method == JUST_WORKS) {
> + set_bit(SMP_FLAG_TK_VALID, &smp->smp_flags);
> + return 0;
> + } else if (method == OVERLAP) {
> + if (hcon->link_mode & HCI_LM_MASTER)
> + method = CFM_PASSKEY;
> + else
> + method = REQ_PASSKEY;
> + }
> +
> + if (method == CFM_PASSKEY) {
> + u8 key[16];
> + /* Generate a passkey for display. It is not valid until
> + * confirmed.
> + */
> + memset(key, 0, sizeof(key));
> + get_random_bytes(&passkey, sizeof(passkey));
> + passkey %= 1000000;
> + put_unaligned_le32(passkey, key);
> + swap128(key, smp->tk);
> + BT_DBG("PassKey: %d", passkey);
> + }
Would it make sense to use switch(method) instead of [if/else/else if] ?
Best regards
Andrei Emeltchenko
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