michaelh/zephyr
1
0
Fork 0
Code Releases Activity

Bluetooth: SMP: Add Encryption Key distribution support

Browse source 
Add support for distributing our LTK to the remote side. Normally we
would generate the needed random bytes when the connection becomes
encrypted, however using bt_hci_cmd_send_sync() from a HCI event
handler (which the encryption_change is) is not possible and will
deadlock (because it needs to wait for a HCI command of its own to
complete). Instead, pre-generate the LTK as part of the SMP context
when we receive the SMP Random PDU from the remote.

Change-Id: Id9cc34b7ddfd1804626cf8bdc81c25aa8cc7943c
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
This commit is contained in:
Johan Hedberg 2015-05-22 13:57:56 +03:00 • committed by Anas Nashif
commit 544cb1433c
1 changed files with 79 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

80
net/bluetooth/smp.c
View file

@ -69,6 +69,14 @@ struct bt_smp {
/* Temporary key */
uint8_t tk[16];
/* Local key distribution */
uint8_t local_dist;
/* Locally generated LTK */
uint8_t ltk[16];
uint64_t rand;
uint16_t ediv;
};
static struct bt_smp bt_smp_pool[CONFIG_BLUETOOTH_MAX_CONN];
@ -328,7 +336,9 @@ static int smp_pairing_req(struct bt_conn *conn, struct bt_buf *buf)
rsp->oob_flag = BT_SMP_OOB_NOT_PRESENT;
rsp->max_key_size = req->max_key_size;
rsp->init_key_dist = 0;
rsp->resp_key_dist = 0;
rsp->resp_key_dist = (req->resp_key_dist & BT_SMP_DIST_ENC_KEY);
smp->local_dist = rsp->resp_key_dist;
memset(smp->tk, 0, sizeof(smp->tk));
@ -443,6 +453,15 @@ static int smp_pairing_random(struct bt_conn *conn, struct bt_buf *buf)
BT_DBG("generated STK %s\n", h(keys->slave_ltk.val, 16));
/* Generate LTK here since doing it in the encrypt_change
* handler would cause a deadlock for hci_cmd_send_sync.
*/
if (smp->local_dist & BT_SMP_DIST_ENC_KEY) {
le_rand(smp->ltk, sizeof(smp->ltk));
le_rand(&smp->rand, sizeof(smp->rand));
le_rand(&smp->ediv, sizeof(smp->ediv));
}
rsp_buf = bt_smp_create_pdu(conn, BT_SMP_CMD_PAIRING_RANDOM,
sizeof(*rsp));
if (!rsp_buf) {
@ -529,6 +548,64 @@ static void bt_smp_disconnected(struct bt_conn *conn)
memset(smp, 0, sizeof(*smp));
}
static void bt_smp_encrypt_change(struct bt_conn *conn)
{
struct bt_smp *smp = conn->smp;
struct bt_keys *keys;
struct bt_buf *buf;
BT_DBG("conn %p handle %u encrypt 0x%02x\n", conn, conn->handle,
conn->encrypt);
if (!smp || !conn->encrypt) {
return;
}
keys = bt_keys_find(conn->dst, conn->dst_type);
if (!keys) {
BT_ERR("Unable to look up keys for conn %p\n");
return;
}
if (!smp->local_dist) {
return;
}
if (smp->local_dist & BT_SMP_DIST_ENC_KEY) {
struct bt_smp_encrypt_info *info;
struct bt_smp_master_ident *ident;
memcpy(keys->slave_ltk.val, smp->ltk, 16);
keys->slave_ltk.rand = smp->rand;
keys->slave_ltk.ediv = smp->ediv;
buf = bt_smp_create_pdu(conn, BT_SMP_CMD_ENCRYPT_INFO,
sizeof(*info));
if (!buf) {
BT_ERR("Unable to allocate Encrypt Info buffer\n");
return;
}
info = bt_buf_add(buf, sizeof(*info));
memcpy(info->ltk, smp->ltk, sizeof(info->ltk));
bt_l2cap_send(conn, BT_L2CAP_CID_SMP, buf);
buf = bt_smp_create_pdu(conn, BT_SMP_CMD_MASTER_IDENT,
sizeof(*ident));
if (!buf) {
BT_ERR("Unable to allocate Master Ident buffer\n");
return;
}
ident = bt_buf_add(buf, sizeof(*ident));
ident->rand = smp->rand;
ident->ediv = smp->ediv;
bt_l2cap_send(conn, BT_L2CAP_CID_SMP, buf);
}
}
void bt_smp_init(void)
{
static struct bt_l2cap_chan chan = {
@ -536,6 +613,7 @@ void bt_smp_init(void)
.recv = bt_smp_recv,
.connected = bt_smp_connected,
.disconnected = bt_smp_disconnected,
.encrypt_change = bt_smp_encrypt_change,
};
bt_l2cap_chan_register(&chan);