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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>
This commit is contained in:
Brian Gix 2011-12-21 16:12:12 -08:00 committed by Gustavo F. Padovan
parent 371fd83563
commit 2b64d153a0
3 changed files with 211 additions and 22 deletions
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1
include/net/bluetooth/hci_core.h
View File

@ -310,6 +310,7 @@ struct hci_conn {
struct hci_dev *hdev;
void *l2cap_data;
void *sco_data;
void *smp_conn;
struct hci_conn *link;

6
include/net/bluetooth/smp.h
View File

@ -115,6 +115,10 @@ struct smp_cmd_security_req {
#define SMP_MIN_ENC_KEY_SIZE 7
#define SMP_MAX_ENC_KEY_SIZE 16
#define SMP_FLAG_TK_VALID 1
#define SMP_FLAG_CFM_PENDING 2
#define SMP_FLAG_MITM_AUTH 3
struct smp_chan {
struct l2cap_conn *conn;
u8 preq[7]; /* SMP Pairing Request */
@ -124,6 +128,7 @@ struct smp_chan {
u8 pcnf[16]; /* SMP Pairing Confirm */
u8 tk[16]; /* SMP Temporary Key */
u8 smp_key_size;
unsigned long smp_flags;
struct crypto_blkcipher *tfm;
struct work_struct confirm;
struct work_struct random;
@ -134,6 +139,7 @@ struct smp_chan {
int smp_conn_security(struct l2cap_conn *conn, __u8 sec_level);
int smp_sig_channel(struct l2cap_conn *conn, struct sk_buff *skb);
int smp_distribute_keys(struct l2cap_conn *conn, __u8 force);
int smp_user_confirm_reply(struct hci_conn *conn, u16 mgmt_op, __le32 passkey);
void smp_chan_destroy(struct l2cap_conn *conn);

226
net/bluetooth/smp.c
View File

@ -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 @@ static void smp_send_cmd(struct l2cap_conn *conn, u8 code, u16 len, void *data)
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 @@ static void build_pairing_cmd(struct l2cap_conn *conn,
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 @@ static void smp_failure(struct l2cap_conn *conn, u8 reason, u8 send)
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 @@ static void confirm_work(struct work_struct *work)
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 @@ static struct smp_chan *smp_chan_create(struct l2cap_conn *conn)
smp->conn = conn;
conn->smp_chan = smp;
conn->hcon->smp_conn = conn;
hci_conn_hold(conn->hcon);
@ -399,18 +513,64 @@ void smp_chan_destroy(struct l2cap_conn *conn)
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 @@ static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb)
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 @@ static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb)
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 @@ static u8 smp_cmd_pairing_rsp(struct l2cap_conn *conn, struct sk_buff *skb)
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 @@ static u8 smp_cmd_pairing_rsp(struct l2cap_conn *conn, struct sk_buff *skb)
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 @@ static u8 smp_cmd_pairing_rsp(struct l2cap_conn *conn, struct sk_buff *skb)
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 @@ static u8 smp_cmd_pairing_confirm(struct l2cap_conn *conn, struct sk_buff *skb)
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 @@ static u8 smp_cmd_security_req(struct l2cap_conn *conn, struct sk_buff *skb)
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 @@ int smp_conn_security(struct l2cap_conn *conn, __u8 sec_level)
{
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 @@ int smp_conn_security(struct l2cap_conn *conn, __u8 sec_level)
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);
}