Hi Johan,
> Bluetooth 5.0 introduces a new H7 key generation function that's used
> when both sides of the pairing set the CT2 authentication flag to 1.
>
> Signed-off-by: Johan Hedberg <johan.hedberg@xxxxxxxxx>
> ---
> net/bluetooth/smp.c | 83 ++++++++++++++++++++++++++++++++++++++++++-----------
> net/bluetooth/smp.h | 1 +
> 2 files changed, 67 insertions(+), 17 deletions(-)
>
> diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
> index 43faf2aea2ab..069436767d0e 100644
> --- a/net/bluetooth/smp.c
> +++ b/net/bluetooth/smp.c
> @@ -57,7 +57,7 @@
> #define SMP_TIMEOUT msecs_to_jiffies(30000)
>
> #define AUTH_REQ_MASK(dev) (hci_dev_test_flag(dev, HCI_SC_ENABLED) ? \
> - 0x1f : 0x07)
> + 0x3f : 0x07)
> #define KEY_DIST_MASK 0x07
>
> /* Maximum message length that can be passed to aes_cmac */
> @@ -76,6 +76,7 @@ enum {
> SMP_FLAG_DHKEY_PENDING,
> SMP_FLAG_REMOTE_OOB,
> SMP_FLAG_LOCAL_OOB,
> + SMP_FLAG_CT2,
> };
>
> struct smp_dev {
> @@ -357,6 +358,22 @@ static int smp_h6(struct crypto_shash *tfm_cmac, const u8 w[16],
> return err;
> }
>
> +static int smp_h7(struct crypto_shash *tfm_cmac, const u8 w[16],
> + const u8 salt[16], u8 res[16])
> +{
> + int err;
> +
> + SMP_DBG("w %16phN salt %16phN", w, salt);
> +
> + err = aes_cmac(tfm_cmac, salt, w, 16, res);
> + if (err)
> + return err;
> +
> + SMP_DBG("res %16phN", res);
> +
> + return err;
> +}
> +
> /* The following functions map to the legacy SMP crypto functions e, c1,
> * s1 and ah.
> */
> @@ -1130,20 +1147,30 @@ static void sc_add_ltk(struct smp_chan *smp)
>
> static void sc_generate_link_key(struct smp_chan *smp)
> {
> - /* These constants are as specified in the core specification.
> - * In ASCII they spell out to 'tmp1' and 'lebr'.
> - */
> - const u8 tmp1[4] = { 0x31, 0x70, 0x6d, 0x74 };
> + /* From core spec. Spells out in ASCII as 'lebr'. */
> const u8 lebr[4] = { 0x72, 0x62, 0x65, 0x6c };
>
> smp->link_key = kzalloc(16, GFP_KERNEL);
> if (!smp->link_key)
> return;
>
> - if (smp_h6(smp->tfm_cmac, smp->tk, tmp1, smp->link_key)) {
> - kzfree(smp->link_key);
> - smp->link_key = NULL;
> - return;
> + if (test_bit(SMP_FLAG_CT2, &smp->flags)) {
> + const u8 salt[16] = { 0x31, 0x70, 0x6d, 0x74 };
I think this one needs a comment. Especially since we only use 4 octets out of the 16 in the array.
> +
> + if (smp_h7(smp->tfm_cmac, smp->tk, salt, smp->link_key)) {
> + kzfree(smp->link_key);
> + smp->link_key = NULL;
> + return;
> + }
> + } else {
> + /* From core spec. Spells out in ASCII as 'tmp1'. */
> + const u8 tmp1[4] = { 0x31, 0x70, 0x6d, 0x74 };
> +
> + if (smp_h6(smp->tfm_cmac, smp->tk, tmp1, smp->link_key)) {
> + kzfree(smp->link_key);
> + smp->link_key = NULL;
> + return;
> + }
> }
>
> if (smp_h6(smp->tfm_cmac, smp->link_key, lebr, smp->link_key)) {
> @@ -1169,10 +1196,7 @@ static void smp_allow_key_dist(struct smp_chan *smp)
>
> static void sc_generate_ltk(struct smp_chan *smp)
> {
> - /* These constants are as specified in the core specification.
> - * In ASCII they spell out to 'tmp2' and 'brle'.
> - */
> - const u8 tmp2[4] = { 0x32, 0x70, 0x6d, 0x74 };
> + /* From core spec. Spells out in ASCII as 'brle'. */
> const u8 brle[4] = { 0x65, 0x6c, 0x72, 0x62 };
> struct hci_conn *hcon = smp->conn->hcon;
> struct hci_dev *hdev = hcon->hdev;
> @@ -1187,8 +1211,18 @@ static void sc_generate_ltk(struct smp_chan *smp)
> if (key->type == HCI_LK_DEBUG_COMBINATION)
> set_bit(SMP_FLAG_DEBUG_KEY, &smp->flags);
>
> - if (smp_h6(smp->tfm_cmac, key->val, tmp2, smp->tk))
> - return;
> + if (test_bit(SMP_FLAG_CT2, &smp->flags)) {
> + const u8 salt[16] = { 0x32, 0x70, 0x6d, 0x74 };
Same as above, we document where the magic comes from everywhere else. And if it is zero padded, we should mention that.
> +
> + if (smp_h7(smp->tfm_cmac, key->val, salt, smp->tk))
> + return;
> + } else {
> + /* From core spec. Spells out in ASCII as 'tmp2'. */
> + const u8 tmp2[4] = { 0x32, 0x70, 0x6d, 0x74 };
> +
> + if (smp_h6(smp->tfm_cmac, key->val, tmp2, smp->tk))
> + return;
> + }
>
> if (smp_h6(smp->tfm_cmac, smp->tk, brle, smp->tk))
> return;
> @@ -1669,6 +1703,7 @@ static void build_bredr_pairing_cmd(struct smp_chan *smp,
> if (!rsp) {
> memset(req, 0, sizeof(*req));
>
> + req->auth_req = SMP_AUTH_CT2;
> req->init_key_dist = local_dist;
> req->resp_key_dist = remote_dist;
> req->max_key_size = conn->hcon->enc_key_size;
> @@ -1680,6 +1715,7 @@ static void build_bredr_pairing_cmd(struct smp_chan *smp,
>
> memset(rsp, 0, sizeof(*rsp));
>
> + rsp->auth_req = SMP_AUTH_CT2;
> rsp->max_key_size = conn->hcon->enc_key_size;
> rsp->init_key_dist = req->init_key_dist & remote_dist;
> rsp->resp_key_dist = req->resp_key_dist & local_dist;
> @@ -1744,6 +1780,9 @@ static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb)
>
> build_bredr_pairing_cmd(smp, req, &rsp);
>
> + if (req->auth_req & SMP_AUTH_CT2)
> + set_bit(SMP_FLAG_CT2, &smp->flags);
> +
> key_size = min(req->max_key_size, rsp.max_key_size);
> if (check_enc_key_size(conn, key_size))
> return SMP_ENC_KEY_SIZE;
> @@ -1761,9 +1800,13 @@ static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb)
>
> build_pairing_cmd(conn, req, &rsp, auth);
>
> - if (rsp.auth_req & SMP_AUTH_SC)
> + if (rsp.auth_req & SMP_AUTH_SC) {
> set_bit(SMP_FLAG_SC, &smp->flags);
>
> + if (rsp.auth_req & SMP_AUTH_CT2)
> + set_bit(SMP_FLAG_CT2, &smp->flags);
> + }
> +
> if (conn->hcon->io_capability == HCI_IO_NO_INPUT_OUTPUT)
> sec_level = BT_SECURITY_MEDIUM;
> else
> @@ -1917,6 +1960,9 @@ static u8 smp_cmd_pairing_rsp(struct l2cap_conn *conn, struct sk_buff *skb)
> */
> smp->remote_key_dist &= rsp->resp_key_dist;
>
> + if ((req->auth_req & SMP_AUTH_CT2) && (auth & SMP_AUTH_CT2))
> + set_bit(SMP_FLAG_CT2, &smp->flags);
> +
> /* For BR/EDR this means we're done and can start phase 3 */
> if (conn->hcon->type == ACL_LINK) {
> /* Clear bits which are generated but not distributed */
> @@ -2312,8 +2358,11 @@ int smp_conn_security(struct hci_conn *hcon, __u8 sec_level)
>
> authreq = seclevel_to_authreq(sec_level);
>
> - if (hci_dev_test_flag(hcon->hdev, HCI_SC_ENABLED))
> + if (hci_dev_test_flag(hcon->hdev, HCI_SC_ENABLED)) {
> authreq |= SMP_AUTH_SC;
> + if (hci_dev_test_flag(hcon->hdev, HCI_SSP_ENABLED))
> + authreq |= SMP_AUTH_CT2;
> + }
>
> /* Require MITM if IO Capability allows or the security level
> * requires it.
> diff --git a/net/bluetooth/smp.h b/net/bluetooth/smp.h
> index ffcc70b6b199..0ff6247eaa6c 100644
> --- a/net/bluetooth/smp.h
> +++ b/net/bluetooth/smp.h
> @@ -57,6 +57,7 @@ struct smp_cmd_pairing {
> #define SMP_AUTH_MITM 0x04
> #define SMP_AUTH_SC 0x08
> #define SMP_AUTH_KEYPRESS 0x10
> +#define SMP_AUTH_CT2 0x20
>
> #define SMP_CMD_PAIRING_CONFIRM 0x03
> struct smp_cmd_pairing_confirm {
Regards
Marcel
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