net/bluetooth/smp.c

/*
   BlueZ - Bluetooth protocol stack for Linux
   Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License version 2 as
   published by the Free Software Foundation;

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
   IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
   CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

   ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
   COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
   SOFTWARE IS DISCLAIMED.
*/

#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <crypto/b128ops.h>

#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/hci_core.h>
#include <net/bluetooth/l2cap.h>
#include <net/bluetooth/mgmt.h>

#include "smp.h"

#define SMP_TIMEOUT	msecs_to_jiffies(30000)

#define AUTH_REQ_MASK   0x07

static inline void swap128(const u8 src[16], u8 dst[16])
{
	int i;
	for (i = 0; i < 16; i++)
		dst[15 - i] = src[i];
}

static inline void swap56(const u8 src[7], u8 dst[7])
{
	int i;
	for (i = 0; i < 7; i++)
		dst[6 - i] = src[i];
}

static int smp_e(struct crypto_blkcipher *tfm, const u8 *k, u8 *r)
{
	struct blkcipher_desc desc;
	struct scatterlist sg;
	int err;

	if (tfm == NULL) {
		BT_ERR("tfm %p", tfm);
		return -EINVAL;
	}

	desc.tfm = tfm;
	desc.flags = 0;

	err = crypto_blkcipher_setkey(tfm, k, 16);
	if (err) {
		BT_ERR("cipher setkey failed: %d", err);
		return err;
	}

	sg_init_one(&sg, r, 16);

	err = crypto_blkcipher_encrypt(&desc, &sg, &sg, 16);
	if (err)
		BT_ERR("Encrypt data error %d", err);

	return err;
}

static int smp_ah(struct crypto_blkcipher *tfm, u8 irk[16], u8 r[3], u8 res[3])
{
	u8 _res[16], k[16];
	int err;

	/* r' = padding || r */
	memset(_res, 0, 13);
	_res[13] = r[2];
	_res[14] = r[1];
	_res[15] = r[0];

	swap128(irk, k);
	err = smp_e(tfm, k, _res);
	if (err) {
		BT_ERR("Encrypt error");
		return err;
	}

	/* The output of the random address function ah is:
	 *	ah(h, r) = e(k, r') mod 2^24
	 * The output of the security function e is then truncated to 24 bits
	 * by taking the least significant 24 bits of the output of e as the
	 * result of ah.
	 */
	res[0] = _res[15];
	res[1] = _res[14];
	res[2] = _res[13];

	return 0;
}

bool smp_irk_matches(struct crypto_blkcipher *tfm, u8 irk[16],
		     bdaddr_t *bdaddr)
{
	u8 hash[3];
	int err;

	BT_DBG("RPA %pMR IRK %*phN", bdaddr, 16, irk);

	err = smp_ah(tfm, irk, &bdaddr->b[3], hash);
	if (err)
		return false;

	return !memcmp(bdaddr->b, hash, 3);
}

int smp_generate_rpa(struct crypto_blkcipher *tfm, u8 irk[16], bdaddr_t *rpa)
{
	int err;

	get_random_bytes(&rpa->b[3], 3);

	rpa->b[5] &= 0x3f;	/* Clear two most significant bits */
	rpa->b[5] |= 0x40;	/* Set second most significant bit */

	err = smp_ah(tfm, irk, &rpa->b[3], rpa->b);
	if (err < 0)
		return err;

	BT_DBG("RPA %pMR", rpa);

	return 0;
}

static int smp_c1(struct crypto_blkcipher *tfm, u8 k[16], u8 r[16],
		  u8 preq[7], u8 pres[7], u8 _iat, bdaddr_t *ia,
		  u8 _rat, bdaddr_t *ra, u8 res[16])
{
	u8 p1[16], p2[16];
	int err;

	memset(p1, 0, 16);

	/* p1 = pres || preq || _rat || _iat */
	swap56(pres, p1);
	swap56(preq, p1 + 7);
	p1[14] = _rat;
	p1[15] = _iat;

	memset(p2, 0, 16);

	/* p2 = padding || ia || ra */
	baswap((bdaddr_t *) (p2 + 4), ia);
	baswap((bdaddr_t *) (p2 + 10), ra);

	/* res = r XOR p1 */
	u128_xor((u128 *) res, (u128 *) r, (u128 *) p1);

	/* res = e(k, res) */
	err = smp_e(tfm, k, res);
	if (err) {
		BT_ERR("Encrypt data error");
		return err;
	}

	/* res = res XOR p2 */
	u128_xor((u128 *) res, (u128 *) res, (u128 *) p2);

	/* res = e(k, res) */
	err = smp_e(tfm, k, res);
	if (err)
		BT_ERR("Encrypt data error");

	return err;
}

static int smp_s1(struct crypto_blkcipher *tfm, u8 k[16], u8 r1[16],
		  u8 r2[16], u8 _r[16])
{
	int err;

	/* Just least significant octets from r1 and r2 are considered */
	memcpy(_r, r1 + 8, 8);
	memcpy(_r + 8, r2 + 8, 8);

	err = smp_e(tfm, k, _r);
	if (err)
		BT_ERR("Encrypt data error");

	return err;
}

static struct sk_buff *smp_build_cmd(struct l2cap_conn *conn, u8 code,
				     u16 dlen, void *data)
{
	struct sk_buff *skb;
	struct l2cap_hdr *lh;
	int len;

	len = L2CAP_HDR_SIZE + sizeof(code) + dlen;

	if (len > conn->mtu)
		return NULL;

	skb = bt_skb_alloc(len, GFP_ATOMIC);
	if (!skb)
		return NULL;

	lh = (struct l2cap_hdr *) skb_put(skb, L2CAP_HDR_SIZE);
	lh->len = cpu_to_le16(sizeof(code) + dlen);
	lh->cid = cpu_to_le16(L2CAP_CID_SMP);

	memcpy(skb_put(skb, sizeof(code)), &code, sizeof(code));

	memcpy(skb_put(skb, dlen), data, dlen);

	return skb;
}

static void smp_send_cmd(struct l2cap_conn *conn, u8 code, u16 len, void *data)
{
	struct sk_buff *skb = smp_build_cmd(conn, code, len, data);

	BT_DBG("code 0x%2.2x", code);

	if (!skb)
		return;

	skb->priority = HCI_PRIO_MAX;
	hci_send_acl(conn->hchan, skb, 0);

	cancel_delayed_work_sync(&conn->security_timer);
	schedule_delayed_work(&conn->security_timer, 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)
{
	struct smp_chan *smp = conn->smp_chan;
	struct hci_conn *hcon = conn->hcon;
	struct hci_dev *hdev = hcon->hdev;
	u8 local_dist = 0, remote_dist = 0;

	if (test_bit(HCI_PAIRABLE, &conn->hcon->hdev->dev_flags)) {
		local_dist = SMP_DIST_ENC_KEY | SMP_DIST_SIGN;
		remote_dist = SMP_DIST_ENC_KEY | SMP_DIST_SIGN;
		authreq |= SMP_AUTH_BONDING;
	} else {
		authreq &= ~SMP_AUTH_BONDING;
	}

	if (test_bit(HCI_RPA_RESOLVING, &hdev->dev_flags))
		remote_dist |= SMP_DIST_ID_KEY;

	if (test_bit(HCI_PRIVACY, &hdev->dev_flags))
		local_dist |= SMP_DIST_ID_KEY;

	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 = local_dist;
		req->resp_key_dist = remote_dist;
		req->auth_req = (authreq & AUTH_REQ_MASK);

		smp->remote_key_dist = remote_dist;
		return;
	}

	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 & remote_dist;
	rsp->resp_key_dist = req->resp_key_dist & local_dist;
	rsp->auth_req = (authreq & AUTH_REQ_MASK);

	smp->remote_key_dist = rsp->init_key_dist;
}

static u8 check_enc_key_size(struct l2cap_conn *conn, __u8 max_key_size)
{
	struct smp_chan *smp = conn->smp_chan;

	if ((max_key_size > SMP_MAX_ENC_KEY_SIZE) ||
	    (max_key_size < SMP_MIN_ENC_KEY_SIZE))
		return SMP_ENC_KEY_SIZE;

	smp->enc_key_size = max_key_size;

	return 0;
}

static void smp_failure(struct l2cap_conn *conn, u8 reason)
{
	struct hci_conn *hcon = conn->hcon;

	if (reason)
		smp_send_cmd(conn, SMP_CMD_PAIRING_FAIL, sizeof(reason),
			     &reason);

	clear_bit(HCI_CONN_ENCRYPT_PEND, &hcon->flags);
	mgmt_auth_failed(hcon->hdev, &hcon->dst, hcon->type, hcon->dst_type,
			 HCI_ERROR_AUTH_FAILURE);

	cancel_delayed_work_sync(&conn->security_timer);

	if (test_and_clear_bit(HCI_CONN_LE_SMP_PEND, &hcon->flags))
		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[remote_io][local_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, &hcon->dst,
						hcon->type, hcon->dst_type);
	else
		ret = mgmt_user_confirm_request(hcon->hdev, &hcon->dst,
						hcon->type, hcon->dst_type,
						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);
	struct l2cap_conn *conn = smp->conn;
	struct hci_dev *hdev = conn->hcon->hdev;
	struct crypto_blkcipher *tfm = hdev->tfm_aes;
	struct smp_cmd_pairing_confirm cp;
	int ret;
	u8 res[16], reason;

	BT_DBG("conn %p", conn);

	/* Prevent mutual access to hdev->tfm_aes */
	hci_dev_lock(hdev);

	ret = smp_c1(tfm, smp->tk, smp->prnd, smp->preq, smp->prsp,
		     conn->hcon->init_addr_type, &conn->hcon->init_addr,
		     conn->hcon->resp_addr_type, &conn->hcon->resp_addr, res);

	hci_dev_unlock(hdev);

	if (ret) {
		reason = SMP_UNSPECIFIED;
		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);

	return;

error:
	smp_failure(conn, reason);
}

static void random_work(struct work_struct *work)
{
	struct smp_chan *smp = container_of(work, struct smp_chan, random);
	struct l2cap_conn *conn = smp->conn;
	struct hci_conn *hcon = conn->hcon;
	struct hci_dev *hdev = hcon->hdev;
	struct crypto_blkcipher *tfm = hdev->tfm_aes;
	u8 reason, confirm[16], res[16], key[16];
	int ret;

	if (IS_ERR_OR_NULL(tfm)) {
		reason = SMP_UNSPECIFIED;
		goto error;
	}

	BT_DBG("conn %p %s", conn, conn->hcon->out ? "master" : "slave");

	/* Prevent mutual access to hdev->tfm_aes */
	hci_dev_lock(hdev);

	ret = smp_c1(tfm, smp->tk, smp->rrnd, smp->preq, smp->prsp,
		     hcon->init_addr_type, &hcon->init_addr,
		     hcon->resp_addr_type, &hcon->resp_addr, res);

	hci_dev_unlock(hdev);

	if (ret) {
		reason = SMP_UNSPECIFIED;
		goto error;
	}

	swap128(res, confirm);

	if (memcmp(smp->pcnf, confirm, sizeof(smp->pcnf)) != 0) {
		BT_ERR("Pairing failed (confirmation values mismatch)");
		reason = SMP_CONFIRM_FAILED;
		goto error;
	}

	if (hcon->out) {
		u8 stk[16];
		__le64 rand = 0;
		__le16 ediv = 0;

		smp_s1(tfm, smp->tk, smp->rrnd, smp->prnd, key);
		swap128(key, stk);

		memset(stk + smp->enc_key_size, 0,
		       SMP_MAX_ENC_KEY_SIZE - smp->enc_key_size);

		if (test_and_set_bit(HCI_CONN_ENCRYPT_PEND, &hcon->flags)) {
			reason = SMP_UNSPECIFIED;
			goto error;
		}

		hci_le_start_enc(hcon, ediv, rand, stk);
		hcon->enc_key_size = smp->enc_key_size;
	} else {
		u8 stk[16], r[16];
		__le64 rand = 0;
		__le16 ediv = 0;

		swap128(smp->prnd, r);
		smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(r), r);

		smp_s1(tfm, smp->tk, smp->prnd, smp->rrnd, key);
		swap128(key, stk);

		memset(stk + smp->enc_key_size, 0,
		       SMP_MAX_ENC_KEY_SIZE - smp->enc_key_size);

		hci_add_ltk(hcon->hdev, &hcon->dst, hcon->dst_type,
			    HCI_SMP_STK_SLAVE, 0, stk, smp->enc_key_size,
			    ediv, rand);
	}

	return;

error:
	smp_failure(conn, reason);
}

static void smp_reencrypt(struct work_struct *work)
{
	struct smp_chan *smp = container_of(work, struct smp_chan,
					    reencrypt.work);
	struct l2cap_conn *conn = smp->conn;
	struct hci_conn *hcon = conn->hcon;
	struct smp_ltk *ltk = smp->ltk;

	BT_DBG("");

	hci_le_start_enc(hcon, ltk->ediv, ltk->rand, ltk->val);
	hcon->enc_key_size = ltk->enc_size;
}

static struct smp_chan *smp_chan_create(struct l2cap_conn *conn)
{
	struct smp_chan *smp;

	smp = kzalloc(sizeof(*smp), GFP_ATOMIC);
	if (!smp)
		return NULL;

	INIT_WORK(&smp->confirm, confirm_work);
	INIT_WORK(&smp->random, random_work);
	INIT_DELAYED_WORK(&smp->reencrypt, smp_reencrypt);

	smp->conn = conn;
	conn->smp_chan = smp;
	conn->hcon->smp_conn = conn;

	hci_conn_hold(conn->hcon);

	return smp;
}

void smp_chan_destroy(struct l2cap_conn *conn)
{
	struct smp_chan *smp = conn->smp_chan;
	bool complete;

	BUG_ON(!smp);

	cancel_delayed_work_sync(&smp->reencrypt);

	complete = test_bit(SMP_FLAG_COMPLETE, &smp->smp_flags);
	mgmt_smp_complete(conn->hcon, complete);

	kfree(smp->csrk);
	kfree(smp->slave_csrk);

	/* If pairing failed clean up any keys we might have */
	if (!complete) {
		if (smp->ltk) {
			list_del(&smp->ltk->list);
			kfree(smp->ltk);
		}

		if (smp->slave_ltk) {
			list_del(&smp->slave_ltk->list);
			kfree(smp->slave_ltk);
		}

		if (smp->remote_irk) {
			list_del(&smp->remote_irk->list);
			kfree(smp->remote_irk);
		}
	}

	kfree(smp);
	conn->smp_chan = NULL;
	conn->hcon->smp_conn = NULL;
	hci_conn_drop(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);
		return 0;
	default:
		smp_failure(conn, SMP_PASSKEY_ENTRY_FAILED);
		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 (skb->len < sizeof(*req))
		return SMP_UNSPECIFIED;

	if (conn->hcon->link_mode & HCI_LM_MASTER)
		return SMP_CMD_NOTSUPP;

	if (!test_and_set_bit(HCI_CONN_LE_SMP_PEND, &conn->hcon->flags))
		smp = smp_chan_create(conn);
	else
		smp = conn->smp_chan;

	if (!smp)
		return SMP_UNSPECIFIED;

	smp->preq[0] = SMP_CMD_PAIRING_REQ;
	memcpy(&smp->preq[1], req, sizeof(*req));
	skb_pull(skb, sizeof(*req));

	/* We didn't start the pairing, so match remote */
	if (req->auth_req & SMP_AUTH_BONDING)
		auth = req->auth_req;

	conn->hcon->pending_sec_level = authreq_to_seclevel(auth);

	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;

	get_random_bytes(smp->prnd, sizeof(smp->prnd));

	smp->prsp[0] = SMP_CMD_PAIRING_RSP;
	memcpy(&smp->prsp[1], &rsp, sizeof(rsp));

	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;
}

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, auth = SMP_AUTH_NONE;
	int ret;

	BT_DBG("conn %p", conn);

	if (skb->len < sizeof(*rsp))
		return SMP_UNSPECIFIED;

	if (!(conn->hcon->link_mode & HCI_LM_MASTER))
		return SMP_CMD_NOTSUPP;

	skb_pull(skb, sizeof(*rsp));

	req = (void *) &smp->preq[1];

	key_size = min(req->max_key_size, rsp->max_key_size);
	if (check_enc_key_size(conn, key_size))
		return SMP_ENC_KEY_SIZE;

	get_random_bytes(smp->prnd, sizeof(smp->prnd));

	smp->prsp[0] = SMP_CMD_PAIRING_RSP;
	memcpy(&smp->prsp[1], rsp, sizeof(*rsp));

	/* Update remote key distribution in case the remote cleared
	 * some bits that we had enabled in our request.
	 */
	smp->remote_key_dist &= rsp->resp_key_dist;

	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, req->io_capability, rsp->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;
}

static u8 smp_cmd_pairing_confirm(struct l2cap_conn *conn, struct sk_buff *skb)
{
	struct smp_chan *smp = conn->smp_chan;
	struct hci_dev *hdev = conn->hcon->hdev;

	BT_DBG("conn %p %s", conn, conn->hcon->out ? "master" : "slave");

	if (skb->len < sizeof(smp->pcnf))
		return SMP_UNSPECIFIED;

	memcpy(smp->pcnf, skb->data, sizeof(smp->pcnf));
	skb_pull(skb, sizeof(smp->pcnf));

	if (conn->hcon->out) {
		u8 random[16];

		swap128(smp->prnd, random);
		smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(random),
			     random);
	} 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;
}

static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
{
	struct smp_chan *smp = conn->smp_chan;
	struct hci_dev *hdev = conn->hcon->hdev;

	BT_DBG("conn %p", conn);

	if (skb->len < sizeof(smp->rrnd))
		return SMP_UNSPECIFIED;

	swap128(skb->data, smp->rrnd);
	skb_pull(skb, sizeof(smp->rrnd));

	queue_work(hdev->workqueue, &smp->random);

	return 0;
}

static u8 smp_ltk_encrypt(struct l2cap_conn *conn, u8 sec_level)
{
	struct smp_ltk *key;
	struct hci_conn *hcon = conn->hcon;

	key = hci_find_ltk_by_addr(hcon->hdev, &hcon->dst, hcon->dst_type,
				   hcon->out);
	if (!key)
		return 0;

	if (sec_level > BT_SECURITY_MEDIUM && !key->authenticated)
		return 0;

	if (test_and_set_bit(HCI_CONN_ENCRYPT_PEND, &hcon->flags))
		return 1;

	hci_le_start_enc(hcon, key->ediv, key->rand, key->val);
	hcon->enc_key_size = key->enc_size;

	return 1;
}

static u8 smp_cmd_security_req(struct l2cap_conn *conn, struct sk_buff *skb)
{
	struct smp_cmd_security_req *rp = (void *) skb->data;
	struct smp_cmd_pairing cp;
	struct hci_conn *hcon = conn->hcon;
	struct smp_chan *smp;

	BT_DBG("conn %p", conn);

	if (skb->len < sizeof(*rp))
		return SMP_UNSPECIFIED;

	if (!(conn->hcon->link_mode & HCI_LM_MASTER))
		return SMP_CMD_NOTSUPP;

	hcon->pending_sec_level = authreq_to_seclevel(rp->auth_req);

	if (smp_ltk_encrypt(conn, hcon->pending_sec_level))
		return 0;

	if (test_and_set_bit(HCI_CONN_LE_SMP_PEND, &hcon->flags))
		return 0;

	smp = smp_chan_create(conn);

	skb_pull(skb, sizeof(*rp));

	memset(&cp, 0, sizeof(cp));
	build_pairing_cmd(conn, &cp, NULL, rp->auth_req);

	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);

	return 0;
}

bool smp_sufficient_security(struct hci_conn *hcon, u8 sec_level)
{
	if (sec_level == BT_SECURITY_LOW)
		return true;

	if (hcon->sec_level >= sec_level)
		return true;

	return false;
}

int smp_conn_security(struct hci_conn *hcon, __u8 sec_level)
{
	struct l2cap_conn *conn = hcon->l2cap_data;
	struct smp_chan *smp = conn->smp_chan;
	__u8 authreq;

	BT_DBG("conn %p hcon %p level 0x%2.2x", conn, hcon, sec_level);

	if (!test_bit(HCI_LE_ENABLED, &hcon->hdev->dev_flags))
		return 1;

	if (smp_sufficient_security(hcon, sec_level))
		return 1;

	if (hcon->link_mode & HCI_LM_MASTER)
		if (smp_ltk_encrypt(conn, sec_level))
			goto done;

	if (test_and_set_bit(HCI_CONN_LE_SMP_PEND, &hcon->flags))
		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, 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 = authreq;
		smp_send_cmd(conn, SMP_CMD_SECURITY_REQ, sizeof(cp), &cp);
	}

done:
	hcon->pending_sec_level = sec_level;

	return 0;
}

static int smp_cmd_encrypt_info(struct l2cap_conn *conn, struct sk_buff *skb)
{
	struct smp_cmd_encrypt_info *rp = (void *) skb->data;
	struct smp_chan *smp = conn->smp_chan;

	BT_DBG("conn %p", conn);

	if (skb->len < sizeof(*rp))
		return SMP_UNSPECIFIED;

	/* Ignore this PDU if it wasn't requested */
	if (!(smp->remote_key_dist & SMP_DIST_ENC_KEY))
		return 0;

	skb_pull(skb, sizeof(*rp));

	memcpy(smp->tk, rp->ltk, sizeof(smp->tk));

	return 0;
}

static int smp_cmd_master_ident(struct l2cap_conn *conn, struct sk_buff *skb)
{
	struct smp_cmd_master_ident *rp = (void *) skb->data;
	struct smp_chan *smp = conn->smp_chan;
	struct hci_dev *hdev = conn->hcon->hdev;
	struct hci_conn *hcon = conn->hcon;
	struct smp_ltk *ltk;
	u8 authenticated;

	BT_DBG("conn %p", conn);

	if (skb->len < sizeof(*rp))
		return SMP_UNSPECIFIED;

	/* Ignore this PDU if it wasn't requested */
	if (!(smp->remote_key_dist & SMP_DIST_ENC_KEY))
		return 0;

	/* Mark the information as received */
	smp->remote_key_dist &= ~SMP_DIST_ENC_KEY;

	skb_pull(skb, sizeof(*rp));

	hci_dev_lock(hdev);
	authenticated = (hcon->sec_level == BT_SECURITY_HIGH);
	ltk = hci_add_ltk(hdev, &hcon->dst, hcon->dst_type, HCI_SMP_LTK,
			  authenticated, smp->tk, smp->enc_key_size,
			  rp->ediv, rp->rand);
	smp->ltk = ltk;
	if (!(smp->remote_key_dist & SMP_DIST_ID_KEY))
		smp_distribute_keys(conn);
	hci_dev_unlock(hdev);

	return 0;
}

static int smp_cmd_ident_info(struct l2cap_conn *conn, struct sk_buff *skb)
{
	struct smp_cmd_ident_info *info = (void *) skb->data;
	struct smp_chan *smp = conn->smp_chan;

	BT_DBG("");

	if (skb->len < sizeof(*info))
		return SMP_UNSPECIFIED;

	/* Ignore this PDU if it wasn't requested */
	if (!(smp->remote_key_dist & SMP_DIST_ID_KEY))
		return 0;

	skb_pull(skb, sizeof(*info));

	memcpy(smp->irk, info->irk, 16);

	return 0;
}

static int smp_cmd_ident_addr_info(struct l2cap_conn *conn,
				   struct sk_buff *skb)
{
	struct smp_cmd_ident_addr_info *info = (void *) skb->data;
	struct smp_chan *smp = conn->smp_chan;
	struct hci_conn *hcon = conn->hcon;
	bdaddr_t rpa;

	BT_DBG("");

	if (skb->len < sizeof(*info))
		return SMP_UNSPECIFIED;

	/* Ignore this PDU if it wasn't requested */
	if (!(smp->remote_key_dist & SMP_DIST_ID_KEY))
		return 0;

	/* Mark the information as received */
	smp->remote_key_dist &= ~SMP_DIST_ID_KEY;

	skb_pull(skb, sizeof(*info));

	/* Strictly speaking the Core Specification (4.1) allows sending
	 * an empty address which would force us to rely on just the IRK
	 * as "identity information". However, since such
	 * implementations are not known of and in order to not over
	 * complicate our implementation, simply pretend that we never
	 * received an IRK for such a device.
	 */
	if (!bacmp(&info->bdaddr, BDADDR_ANY)) {
		BT_ERR("Ignoring IRK with no identity address");
		smp_distribute_keys(conn);
		return 0;
	}

	bacpy(&smp->id_addr, &info->bdaddr);
	smp->id_addr_type = info->addr_type;

	if (hci_bdaddr_is_rpa(&hcon->dst, hcon->dst_type))
		bacpy(&rpa, &hcon->dst);
	else
		bacpy(&rpa, BDADDR_ANY);

	smp->remote_irk = hci_add_irk(conn->hcon->hdev, &smp->id_addr,
				      smp->id_addr_type, smp->irk, &rpa);

	/* Track the connection based on the Identity Address from now on */
	bacpy(&hcon->dst, &smp->id_addr);
	hcon->dst_type = smp->id_addr_type;

	l2cap_conn_update_id_addr(hcon);

	smp_distribute_keys(conn);

	return 0;
}

static int smp_cmd_sign_info(struct l2cap_conn *conn, struct sk_buff *skb)
{
	struct smp_cmd_sign_info *rp = (void *) skb->data;
	struct smp_chan *smp = conn->smp_chan;
	struct hci_dev *hdev = conn->hcon->hdev;
	struct smp_csrk *csrk;

	BT_DBG("conn %p", conn);

	if (skb->len < sizeof(*rp))
		return SMP_UNSPECIFIED;

	/* Ignore this PDU if it wasn't requested */
	if (!(smp->remote_key_dist & SMP_DIST_SIGN))
		return 0;

	/* Mark the information as received */
	smp->remote_key_dist &= ~SMP_DIST_SIGN;

	skb_pull(skb, sizeof(*rp));

	hci_dev_lock(hdev);
	csrk = kzalloc(sizeof(*csrk), GFP_KERNEL);
	if (csrk) {
		csrk->master = 0x01;
		memcpy(csrk->val, rp->csrk, sizeof(csrk->val));
	}
	smp->csrk = csrk;
	if (!(smp->remote_key_dist & SMP_DIST_SIGN))
		smp_distribute_keys(conn);
	hci_dev_unlock(hdev);

	return 0;
}

int smp_sig_channel(struct l2cap_conn *conn, struct sk_buff *skb)
{
	struct hci_conn *hcon = conn->hcon;
	__u8 code, reason;
	int err = 0;

	if (hcon->type != LE_LINK) {
		kfree_skb(skb);
		return 0;
	}

	if (skb->len < 1) {
		kfree_skb(skb);
		return -EILSEQ;
	}

	if (!test_bit(HCI_LE_ENABLED, &hcon->hdev->dev_flags)) {
		err = -ENOTSUPP;
		reason = SMP_PAIRING_NOTSUPP;
		goto done;
	}

	code = skb->data[0];
	skb_pull(skb, sizeof(code));

	/*
	 * The SMP context must be initialized for all other PDUs except
	 * pairing and security requests. If we get any other PDU when
	 * not initialized simply disconnect (done if this function
	 * returns an error).
	 */
	if (code != SMP_CMD_PAIRING_REQ && code != SMP_CMD_SECURITY_REQ &&
	    !conn->smp_chan) {
		BT_ERR("Unexpected SMP command 0x%02x. Disconnecting.", code);
		kfree_skb(skb);
		return -ENOTSUPP;
	}

	switch (code) {
	case SMP_CMD_PAIRING_REQ:
		reason = smp_cmd_pairing_req(conn, skb);
		break;

	case SMP_CMD_PAIRING_FAIL:
		smp_failure(conn, 0);
		reason = 0;
		err = -EPERM;
		break;

	case SMP_CMD_PAIRING_RSP:
		reason = smp_cmd_pairing_rsp(conn, skb);
		break;

	case SMP_CMD_SECURITY_REQ:
		reason = smp_cmd_security_req(conn, skb);
		break;

	case SMP_CMD_PAIRING_CONFIRM:
		reason = smp_cmd_pairing_confirm(conn, skb);
		break;

	case SMP_CMD_PAIRING_RANDOM:
		reason = smp_cmd_pairing_random(conn, skb);
		break;

	case SMP_CMD_ENCRYPT_INFO:
		reason = smp_cmd_encrypt_info(conn, skb);
		break;

	case SMP_CMD_MASTER_IDENT:
		reason = smp_cmd_master_ident(conn, skb);
		break;

	case SMP_CMD_IDENT_INFO:
		reason = smp_cmd_ident_info(conn, skb);
		break;

	case SMP_CMD_IDENT_ADDR_INFO:
		reason = smp_cmd_ident_addr_info(conn, skb);
		break;

	case SMP_CMD_SIGN_INFO:
		reason = smp_cmd_sign_info(conn, skb);
		break;

	default:
		BT_DBG("Unknown command code 0x%2.2x", code);

		reason = SMP_CMD_NOTSUPP;
		err = -EOPNOTSUPP;
		goto done;
	}

done:
	if (reason)
		smp_failure(conn, reason);

	kfree_skb(skb);
	return err;
}

static void smp_notify_keys(struct l2cap_conn *conn)
{
	struct smp_chan *smp = conn->smp_chan;
	struct hci_conn *hcon = conn->hcon;
	struct hci_dev *hdev = hcon->hdev;
	struct smp_cmd_pairing *req = (void *) &smp->preq[1];
	struct smp_cmd_pairing *rsp = (void *) &smp->prsp[1];
	bool persistent;

	if (smp->remote_irk)
		mgmt_new_irk(hdev, smp->remote_irk);

	/* The LTKs and CSRKs should be persistent only if both sides
	 * had the bonding bit set in their authentication requests.
	 */
	persistent = !!((req->auth_req & rsp->auth_req) & SMP_AUTH_BONDING);

	if (smp->csrk) {
		smp->csrk->bdaddr_type = hcon->dst_type;
		bacpy(&smp->csrk->bdaddr, &hcon->dst);
		mgmt_new_csrk(hdev, smp->csrk, persistent);
	}

	if (smp->slave_csrk) {
		smp->slave_csrk->bdaddr_type = hcon->dst_type;
		bacpy(&smp->slave_csrk->bdaddr, &hcon->dst);
		mgmt_new_csrk(hdev, smp->slave_csrk, persistent);
	}

	if (smp->ltk) {
		smp->ltk->bdaddr_type = hcon->dst_type;
		bacpy(&smp->ltk->bdaddr, &hcon->dst);
		mgmt_new_ltk(hdev, smp->ltk, persistent);
	}

	if (smp->slave_ltk) {
		smp->slave_ltk->bdaddr_type = hcon->dst_type;
		bacpy(&smp->slave_ltk->bdaddr, &hcon->dst);
		mgmt_new_ltk(hdev, smp->slave_ltk, persistent);
	}
}

int smp_distribute_keys(struct l2cap_conn *conn)
{
	struct smp_cmd_pairing *req, *rsp;
	struct smp_chan *smp = conn->smp_chan;
	struct hci_conn *hcon = conn->hcon;
	struct hci_dev *hdev = hcon->hdev;
	bool ltk_encrypt;
	__u8 *keydist;

	BT_DBG("conn %p", conn);

	if (!test_bit(HCI_CONN_LE_SMP_PEND, &hcon->flags))
		return 0;

	rsp = (void *) &smp->prsp[1];

	/* The responder sends its keys first */
	if (hcon->out && (smp->remote_key_dist & 0x07))
		return 0;

	req = (void *) &smp->preq[1];

	if (hcon->out) {
		keydist = &rsp->init_key_dist;
		*keydist &= req->init_key_dist;
	} else {
		keydist = &rsp->resp_key_dist;
		*keydist &= req->resp_key_dist;
	}

	BT_DBG("keydist 0x%x", *keydist);

	if (*keydist & SMP_DIST_ENC_KEY) {
		struct smp_cmd_encrypt_info enc;
		struct smp_cmd_master_ident ident;
		struct smp_ltk *ltk;
		u8 authenticated;
		__le16 ediv;
		__le64 rand;

		get_random_bytes(enc.ltk, sizeof(enc.ltk));
		get_random_bytes(&ediv, sizeof(ediv));
		get_random_bytes(&rand, sizeof(rand));

		smp_send_cmd(conn, SMP_CMD_ENCRYPT_INFO, sizeof(enc), &enc);

		authenticated = hcon->sec_level == BT_SECURITY_HIGH;
		ltk = hci_add_ltk(hdev, &hcon->dst, hcon->dst_type,
				  HCI_SMP_LTK_SLAVE, authenticated, enc.ltk,
				  smp->enc_key_size, ediv, rand);
		smp->slave_ltk = ltk;

		ident.ediv = ediv;
		ident.rand = rand;

		smp_send_cmd(conn, SMP_CMD_MASTER_IDENT, sizeof(ident), &ident);

		*keydist &= ~SMP_DIST_ENC_KEY;
	}

	if (*keydist & SMP_DIST_ID_KEY) {
		struct smp_cmd_ident_addr_info addrinfo;
		struct smp_cmd_ident_info idinfo;

		memcpy(idinfo.irk, hdev->irk, sizeof(idinfo.irk));

		smp_send_cmd(conn, SMP_CMD_IDENT_INFO, sizeof(idinfo), &idinfo);

		/* The hci_conn contains the local identity address
		 * after the connection has been established.
		 *
		 * This is true even when the connection has been
		 * established using a resolvable random address.
		 */
		bacpy(&addrinfo.bdaddr, &hcon->src);
		addrinfo.addr_type = hcon->src_type;

		smp_send_cmd(conn, SMP_CMD_IDENT_ADDR_INFO, sizeof(addrinfo),
			     &addrinfo);

		*keydist &= ~SMP_DIST_ID_KEY;
	}

	if (*keydist & SMP_DIST_SIGN) {
		struct smp_cmd_sign_info sign;
		struct smp_csrk *csrk;

		/* Generate a new random key */
		get_random_bytes(sign.csrk, sizeof(sign.csrk));

		csrk = kzalloc(sizeof(*csrk), GFP_KERNEL);
		if (csrk) {
			csrk->master = 0x00;
			memcpy(csrk->val, sign.csrk, sizeof(csrk->val));
		}
		smp->slave_csrk = csrk;

		smp_send_cmd(conn, SMP_CMD_SIGN_INFO, sizeof(sign), &sign);

		*keydist &= ~SMP_DIST_SIGN;
	}

	/* If there are still keys to be received wait for them */
	if ((smp->remote_key_dist & 0x07))
		return 0;

	/* Check if we should try to re-encrypt the link with the LTK.
	 * SMP_FLAG_LTK_ENCRYPT flag is used to track whether we've
	 * already tried this (in which case we shouldn't try again).
	 *
	 * The request will trigger an encryption key refresh event
	 * which will cause a call to auth_cfm and eventually lead to
	 * l2cap_core.c calling this smp_distribute_keys function again
	 * and thereby completing the process.
	 */
	if (smp->ltk)
		ltk_encrypt = !test_and_set_bit(SMP_FLAG_LTK_ENCRYPT,
						&smp->smp_flags);
	else
		ltk_encrypt = false;

	/* Re-encrypt the link with LTK if possible */
	if (ltk_encrypt && hcon->out) {
		queue_delayed_work(hdev->req_workqueue, &smp->reencrypt,
				   SMP_REENCRYPT_TIMEOUT);
	} else {
		clear_bit(HCI_CONN_LE_SMP_PEND, &hcon->flags);
		cancel_delayed_work_sync(&conn->security_timer);
		set_bit(SMP_FLAG_COMPLETE, &smp->smp_flags);
		smp_notify_keys(conn);
		smp_chan_destroy(conn);
	}

	return 0;
}