Bluetooth: Add MITM mechanism to LE-SMP
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@codeaurora.org>
Acked-by: Marcel Holtmann<marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 0ee2905..9fea4bf 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -23,6 +23,7 @@
#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/hci_core.h>
#include <net/bluetooth/l2cap.h>
+#include <net/bluetooth/mgmt.h>
#include <net/bluetooth/smp.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
@@ -189,24 +190,45 @@
msecs_to_jiffies(SMP_TIMEOUT));
}
+static __u8 authreq_to_seclevel(__u8 authreq)
+{
+ if (authreq & SMP_AUTH_MITM)
+ return BT_SECURITY_HIGH;
+ else
+ return BT_SECURITY_MEDIUM;
+}
+
+static __u8 seclevel_to_authreq(__u8 sec_level)
+{
+ switch (sec_level) {
+ case BT_SECURITY_HIGH:
+ return SMP_AUTH_MITM | SMP_AUTH_BONDING;
+ case BT_SECURITY_MEDIUM:
+ return SMP_AUTH_BONDING;
+ default:
+ return SMP_AUTH_NONE;
+ }
+}
+
static void build_pairing_cmd(struct l2cap_conn *conn,
struct smp_cmd_pairing *req,
struct smp_cmd_pairing *rsp,
__u8 authreq)
{
- u8 dist_keys;
+ u8 dist_keys = 0;
- dist_keys = 0;
if (test_bit(HCI_PAIRABLE, &conn->hcon->hdev->flags)) {
dist_keys = SMP_DIST_ENC_KEY;
authreq |= SMP_AUTH_BONDING;
+ } else {
+ authreq &= ~SMP_AUTH_BONDING;
}
if (rsp == NULL) {
req->io_capability = conn->hcon->io_capability;
req->oob_flag = SMP_OOB_NOT_PRESENT;
req->max_key_size = SMP_MAX_ENC_KEY_SIZE;
- req->init_key_dist = dist_keys;
+ req->init_key_dist = 0;
req->resp_key_dist = dist_keys;
req->auth_req = authreq;
return;
@@ -215,7 +237,7 @@
rsp->io_capability = conn->hcon->io_capability;
rsp->oob_flag = SMP_OOB_NOT_PRESENT;
rsp->max_key_size = SMP_MAX_ENC_KEY_SIZE;
- rsp->init_key_dist = req->init_key_dist & dist_keys;
+ rsp->init_key_dist = 0;
rsp->resp_key_dist = req->resp_key_dist & dist_keys;
rsp->auth_req = authreq;
}
@@ -245,6 +267,95 @@
smp_chan_destroy(conn);
}
+#define JUST_WORKS 0x00
+#define JUST_CFM 0x01
+#define REQ_PASSKEY 0x02
+#define CFM_PASSKEY 0x03
+#define REQ_OOB 0x04
+#define OVERLAP 0xFF
+
+static const u8 gen_method[5][5] = {
+ { JUST_WORKS, JUST_CFM, REQ_PASSKEY, JUST_WORKS, REQ_PASSKEY },
+ { JUST_WORKS, JUST_CFM, REQ_PASSKEY, JUST_WORKS, REQ_PASSKEY },
+ { CFM_PASSKEY, CFM_PASSKEY, REQ_PASSKEY, JUST_WORKS, CFM_PASSKEY },
+ { JUST_WORKS, JUST_CFM, JUST_WORKS, JUST_WORKS, JUST_CFM },
+ { CFM_PASSKEY, CFM_PASSKEY, REQ_PASSKEY, JUST_WORKS, OVERLAP },
+};
+
+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 for 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 */
+ /* Otherwise, look up method from the table */
+ if (!(auth & SMP_AUTH_MITM) ||
+ local_io > SMP_IO_KEYBOARD_DISPLAY ||
+ remote_io > SMP_IO_KEYBOARD_DISPLAY)
+ method = JUST_WORKS;
+ else
+ method = gen_method[local_io][remote_io];
+
+ /* If not bonding, don't ask user to confirm a Zero TK */
+ if (!(auth & SMP_AUTH_BONDING) && method == JUST_CFM)
+ method = JUST_WORKS;
+
+ /* If Just Works, Continue with Zero TK */
+ if (method == JUST_WORKS) {
+ set_bit(SMP_FLAG_TK_VALID, &smp->smp_flags);
+ return 0;
+ }
+
+ /* Not Just Works/Confirm results in MITM Authentication */
+ if (method != JUST_CFM)
+ set_bit(SMP_FLAG_MITM_AUTH, &smp->smp_flags);
+
+ /* If both devices have Keyoard-Display I/O, the master
+ * Confirms and the slave Enters the passkey.
+ */
+ if (method == OVERLAP) {
+ if (hcon->link_mode & HCI_LM_MASTER)
+ method = CFM_PASSKEY;
+ else
+ method = REQ_PASSKEY;
+ }
+
+ /* Generate random passkey. Not valid until confirmed. */
+ if (method == CFM_PASSKEY) {
+ u8 key[16];
+
+ 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);
+ }
+
+ hci_dev_lock(hcon->hdev);
+
+ if (method == REQ_PASSKEY)
+ ret = mgmt_user_passkey_request(hcon->hdev, conn->dst);
+ else
+ ret = mgmt_user_confirm_request(hcon->hdev, conn->dst,
+ cpu_to_le32(passkey), 0);
+
+ hci_dev_unlock(hcon->hdev);
+
+ return ret;
+}
+
static void confirm_work(struct work_struct *work)
{
struct smp_chan *smp = container_of(work, struct smp_chan, confirm);
@@ -277,6 +388,8 @@
goto error;
}
+ clear_bit(SMP_FLAG_CFM_PENDING, &smp->smp_flags);
+
swap128(res, cp.confirm_val);
smp_send_cmd(smp->conn, SMP_CMD_PAIRING_CONFIRM, sizeof(cp), &cp);
@@ -382,6 +495,7 @@
smp->conn = conn;
conn->smp_chan = smp;
+ conn->hcon->smp_conn = conn;
hci_conn_hold(conn->hcon);
@@ -399,18 +513,64 @@
kfree(smp);
conn->smp_chan = NULL;
+ conn->hcon->smp_conn = NULL;
hci_conn_put(conn->hcon);
}
+int smp_user_confirm_reply(struct hci_conn *hcon, u16 mgmt_op, __le32 passkey)
+{
+ struct l2cap_conn *conn = hcon->smp_conn;
+ struct smp_chan *smp;
+ u32 value;
+ u8 key[16];
+
+ BT_DBG("");
+
+ if (!conn)
+ return -ENOTCONN;
+
+ smp = conn->smp_chan;
+
+ switch (mgmt_op) {
+ case MGMT_OP_USER_PASSKEY_REPLY:
+ value = le32_to_cpu(passkey);
+ memset(key, 0, sizeof(key));
+ BT_DBG("PassKey: %d", value);
+ put_unaligned_le32(value, key);
+ swap128(key, smp->tk);
+ /* Fall Through */
+ case MGMT_OP_USER_CONFIRM_REPLY:
+ set_bit(SMP_FLAG_TK_VALID, &smp->smp_flags);
+ break;
+ case MGMT_OP_USER_PASSKEY_NEG_REPLY:
+ case MGMT_OP_USER_CONFIRM_NEG_REPLY:
+ smp_failure(conn, SMP_PASSKEY_ENTRY_FAILED, 1);
+ return 0;
+ default:
+ smp_failure(conn, SMP_PASSKEY_ENTRY_FAILED, 1);
+ return -EOPNOTSUPP;
+ }
+
+ /* If it is our turn to send Pairing Confirm, do so now */
+ if (test_bit(SMP_FLAG_CFM_PENDING, &smp->smp_flags))
+ queue_work(hcon->hdev->workqueue, &smp->confirm);
+
+ return 0;
+}
+
static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb)
{
struct smp_cmd_pairing rsp, *req = (void *) skb->data;
struct smp_chan *smp;
u8 key_size;
+ u8 auth = SMP_AUTH_NONE;
int ret;
BT_DBG("conn %p", conn);
+ if (conn->hcon->link_mode & HCI_LM_MASTER)
+ return SMP_CMD_NOTSUPP;
+
if (!test_and_set_bit(HCI_CONN_LE_SMP_PEND, &conn->hcon->pend))
smp = smp_chan_create(conn);
@@ -420,19 +580,16 @@
memcpy(&smp->preq[1], req, sizeof(*req));
skb_pull(skb, sizeof(*req));
- if (req->oob_flag)
- return SMP_OOB_NOT_AVAIL;
+ /* We didn't start the pairing, so match remote */
+ if (req->auth_req & SMP_AUTH_BONDING)
+ auth = req->auth_req;
- /* We didn't start the pairing, so no requirements */
- build_pairing_cmd(conn, req, &rsp, SMP_AUTH_NONE);
+ build_pairing_cmd(conn, req, &rsp, auth);
key_size = min(req->max_key_size, rsp.max_key_size);
if (check_enc_key_size(conn, key_size))
return SMP_ENC_KEY_SIZE;
- /* Just works */
- memset(smp->tk, 0, sizeof(smp->tk));
-
ret = smp_rand(smp->prnd);
if (ret)
return SMP_UNSPECIFIED;
@@ -442,6 +599,11 @@
smp_send_cmd(conn, SMP_CMD_PAIRING_RSP, sizeof(rsp), &rsp);
+ /* Request setup of TK */
+ ret = tk_request(conn, 0, auth, rsp.io_capability, req->io_capability);
+ if (ret)
+ return SMP_UNSPECIFIED;
+
return 0;
}
@@ -450,11 +612,14 @@
struct smp_cmd_pairing *req, *rsp = (void *) skb->data;
struct smp_chan *smp = conn->smp_chan;
struct hci_dev *hdev = conn->hcon->hdev;
- u8 key_size;
+ u8 key_size, auth = SMP_AUTH_NONE;
int ret;
BT_DBG("conn %p", conn);
+ if (!(conn->hcon->link_mode & HCI_LM_MASTER))
+ return SMP_CMD_NOTSUPP;
+
skb_pull(skb, sizeof(*rsp));
req = (void *) &smp->preq[1];
@@ -463,12 +628,6 @@
if (check_enc_key_size(conn, key_size))
return SMP_ENC_KEY_SIZE;
- if (rsp->oob_flag)
- return SMP_OOB_NOT_AVAIL;
-
- /* Just works */
- memset(smp->tk, 0, sizeof(smp->tk));
-
ret = smp_rand(smp->prnd);
if (ret)
return SMP_UNSPECIFIED;
@@ -476,6 +635,22 @@
smp->prsp[0] = SMP_CMD_PAIRING_RSP;
memcpy(&smp->prsp[1], rsp, sizeof(*rsp));
+ if ((req->auth_req & SMP_AUTH_BONDING) &&
+ (rsp->auth_req & SMP_AUTH_BONDING))
+ auth = SMP_AUTH_BONDING;
+
+ auth |= (req->auth_req | rsp->auth_req) & SMP_AUTH_MITM;
+
+ ret = tk_request(conn, 0, auth, rsp->io_capability, req->io_capability);
+ if (ret)
+ return SMP_UNSPECIFIED;
+
+ set_bit(SMP_FLAG_CFM_PENDING, &smp->smp_flags);
+
+ /* Can't compose response until we have been confirmed */
+ if (!test_bit(SMP_FLAG_TK_VALID, &smp->smp_flags))
+ return 0;
+
queue_work(hdev->workqueue, &smp->confirm);
return 0;
@@ -497,8 +672,10 @@
swap128(smp->prnd, random);
smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(random),
random);
- } else {
+ } else if (test_bit(SMP_FLAG_TK_VALID, &smp->smp_flags)) {
queue_work(hdev->workqueue, &smp->confirm);
+ } else {
+ set_bit(SMP_FLAG_CFM_PENDING, &smp->smp_flags);
}
return 0;
@@ -551,7 +728,7 @@
BT_DBG("conn %p", conn);
- hcon->pending_sec_level = BT_SECURITY_MEDIUM;
+ hcon->pending_sec_level = authreq_to_seclevel(rp->auth_req);
if (smp_ltk_encrypt(conn))
return 0;
@@ -578,6 +755,7 @@
{
struct hci_conn *hcon = conn->hcon;
struct smp_chan *smp = conn->smp_chan;
+ __u8 authreq;
BT_DBG("conn %p hcon %p level 0x%2.2x", conn, hcon, sec_level);
@@ -598,18 +776,22 @@
return 0;
smp = smp_chan_create(conn);
+ if (!smp)
+ return 1;
+
+ authreq = seclevel_to_authreq(sec_level);
if (hcon->link_mode & HCI_LM_MASTER) {
struct smp_cmd_pairing cp;
- build_pairing_cmd(conn, &cp, NULL, SMP_AUTH_NONE);
+ build_pairing_cmd(conn, &cp, NULL, authreq);
smp->preq[0] = SMP_CMD_PAIRING_REQ;
memcpy(&smp->preq[1], &cp, sizeof(cp));
smp_send_cmd(conn, SMP_CMD_PAIRING_REQ, sizeof(cp), &cp);
} else {
struct smp_cmd_security_req cp;
- cp.auth_req = SMP_AUTH_NONE;
+ cp.auth_req = authreq;
smp_send_cmd(conn, SMP_CMD_SECURITY_REQ, sizeof(cp), &cp);
}