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/debugfs.h>
#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 "ecc.h"
#include "smp.h"

#define SMP_DEV(hdev) \
	((struct smp_dev *)((struct l2cap_chan *)((hdev)->smp_data))->data)

/* Low-level debug macros to be used for stuff that we don't want
 * accidentially in dmesg, i.e. the values of the various crypto keys
 * and the inputs & outputs of crypto functions.
 */
#ifdef DEBUG
#define SMP_DBG(fmt, ...) printk(KERN_DEBUG "%s: " fmt, __func__, \
				 ##__VA_ARGS__)
#else
#define SMP_DBG(fmt, ...) no_printk(KERN_DEBUG "%s: " fmt, __func__, \
				    ##__VA_ARGS__)
#endif

#define SMP_ALLOW_CMD(smp, code)	set_bit(code, &smp->allow_cmd)

/* Keys which are not distributed with Secure Connections */
#define SMP_SC_NO_DIST (SMP_DIST_ENC_KEY | SMP_DIST_LINK_KEY);

#define SMP_TIMEOUT	msecs_to_jiffies(30000)

#define AUTH_REQ_MASK(dev)	(hci_dev_test_flag(dev, HCI_SC_ENABLED) ? \
				 0x1f : 0x07)
#define KEY_DIST_MASK		0x07

/* Maximum message length that can be passed to aes_cmac */
#define CMAC_MSG_MAX	80

enum {
	SMP_FLAG_TK_VALID,
	SMP_FLAG_CFM_PENDING,
	SMP_FLAG_MITM_AUTH,
	SMP_FLAG_COMPLETE,
	SMP_FLAG_INITIATOR,
	SMP_FLAG_SC,
	SMP_FLAG_REMOTE_PK,
	SMP_FLAG_DEBUG_KEY,
	SMP_FLAG_WAIT_USER,
	SMP_FLAG_DHKEY_PENDING,
	SMP_FLAG_REMOTE_OOB,
	SMP_FLAG_LOCAL_OOB,
};

struct smp_dev {
	/* Secure Connections OOB data */
	u8			local_pk[64];
	u8			local_sk[32];
	u8			local_rand[16];
	bool			debug_key;

	u8			min_key_size;
	u8			max_key_size;

	struct crypto_blkcipher	*tfm_aes;
	struct crypto_hash	*tfm_cmac;
};

struct smp_chan {
	struct l2cap_conn	*conn;
	struct delayed_work	security_timer;
	unsigned long           allow_cmd; /* Bitmask of allowed commands */

	u8		preq[7]; /* SMP Pairing Request */
	u8		prsp[7]; /* SMP Pairing Response */
	u8		prnd[16]; /* SMP Pairing Random (local) */
	u8		rrnd[16]; /* SMP Pairing Random (remote) */
	u8		pcnf[16]; /* SMP Pairing Confirm */
	u8		tk[16]; /* SMP Temporary Key */
	u8		rr[16]; /* Remote OOB ra/rb value */
	u8		lr[16]; /* Local OOB ra/rb value */
	u8		enc_key_size;
	u8		remote_key_dist;
	bdaddr_t	id_addr;
	u8		id_addr_type;
	u8		irk[16];
	struct smp_csrk	*csrk;
	struct smp_csrk	*slave_csrk;
	struct smp_ltk	*ltk;
	struct smp_ltk	*slave_ltk;
	struct smp_irk	*remote_irk;
	u8		*link_key;
	unsigned long	flags;
	u8		method;
	u8		passkey_round;

	/* Secure Connections variables */
	u8			local_pk[64];
	u8			local_sk[32];
	u8			remote_pk[64];
	u8			dhkey[32];
	u8			mackey[16];

	struct crypto_blkcipher	*tfm_aes;
	struct crypto_hash	*tfm_cmac;
};

/* These debug key values are defined in the SMP section of the core
 * specification. debug_pk is the public debug key and debug_sk the
 * private debug key.
 */
static const u8 debug_pk[64] = {
		0xe6, 0x9d, 0x35, 0x0e, 0x48, 0x01, 0x03, 0xcc,
		0xdb, 0xfd, 0xf4, 0xac, 0x11, 0x91, 0xf4, 0xef,
		0xb9, 0xa5, 0xf9, 0xe9, 0xa7, 0x83, 0x2c, 0x5e,
		0x2c, 0xbe, 0x97, 0xf2, 0xd2, 0x03, 0xb0, 0x20,

		0x8b, 0xd2, 0x89, 0x15, 0xd0, 0x8e, 0x1c, 0x74,
		0x24, 0x30, 0xed, 0x8f, 0xc2, 0x45, 0x63, 0x76,
		0x5c, 0x15, 0x52, 0x5a, 0xbf, 0x9a, 0x32, 0x63,
		0x6d, 0xeb, 0x2a, 0x65, 0x49, 0x9c, 0x80, 0xdc,
};

static const u8 debug_sk[32] = {
		0xbd, 0x1a, 0x3c, 0xcd, 0xa6, 0xb8, 0x99, 0x58,
		0x99, 0xb7, 0x40, 0xeb, 0x7b, 0x60, 0xff, 0x4a,
		0x50, 0x3f, 0x10, 0xd2, 0xe3, 0xb3, 0xc9, 0x74,
		0x38, 0x5f, 0xc5, 0xa3, 0xd4, 0xf6, 0x49, 0x3f,
};

static inline void swap_buf(const u8 *src, u8 *dst, size_t len)
{
	size_t i;

	for (i = 0; i < len; i++)
		dst[len - 1 - i] = src[i];
}

/* The following functions map to the LE SC SMP crypto functions
 * AES-CMAC, f4, f5, f6, g2 and h6.
 */

static int aes_cmac(struct crypto_hash *tfm, const u8 k[16], const u8 *m,
		    size_t len, u8 mac[16])
{
	uint8_t tmp[16], mac_msb[16], msg_msb[CMAC_MSG_MAX];
	struct hash_desc desc;
	struct scatterlist sg;
	int err;

	if (len > CMAC_MSG_MAX)
		return -EFBIG;

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

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

	crypto_hash_init(&desc);

	/* Swap key and message from LSB to MSB */
	swap_buf(k, tmp, 16);
	swap_buf(m, msg_msb, len);

	SMP_DBG("msg (len %zu) %*phN", len, (int) len, m);
	SMP_DBG("key %16phN", k);

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

	sg_init_one(&sg, msg_msb, len);

	err = crypto_hash_update(&desc, &sg, len);
	if (err) {
		BT_ERR("Hash update error %d", err);
		return err;
	}

	err = crypto_hash_final(&desc, mac_msb);
	if (err) {
		BT_ERR("Hash final error %d", err);
		return err;
	}

	swap_buf(mac_msb, mac, 16);

	SMP_DBG("mac %16phN", mac);

	return 0;
}

static int smp_f4(struct crypto_hash *tfm_cmac, const u8 u[32], const u8 v[32],
		  const u8 x[16], u8 z, u8 res[16])
{
	u8 m[65];
	int err;

	SMP_DBG("u %32phN", u);
	SMP_DBG("v %32phN", v);
	SMP_DBG("x %16phN z %02x", x, z);

	m[0] = z;
	memcpy(m + 1, v, 32);
	memcpy(m + 33, u, 32);

	err = aes_cmac(tfm_cmac, x, m, sizeof(m), res);
	if (err)
		return err;

	SMP_DBG("res %16phN", res);

	return err;
}

static int smp_f5(struct crypto_hash *tfm_cmac, const u8 w[32],
		  const u8 n1[16], const u8 n2[16], const u8 a1[7],
		  const u8 a2[7], u8 mackey[16], u8 ltk[16])
{
	/* The btle, salt and length "magic" values are as defined in
	 * the SMP section of the Bluetooth core specification. In ASCII
	 * the btle value ends up being 'btle'. The salt is just a
	 * random number whereas length is the value 256 in little
	 * endian format.
	 */
	const u8 btle[4] = { 0x65, 0x6c, 0x74, 0x62 };
	const u8 salt[16] = { 0xbe, 0x83, 0x60, 0x5a, 0xdb, 0x0b, 0x37, 0x60,
			      0x38, 0xa5, 0xf5, 0xaa, 0x91, 0x83, 0x88, 0x6c };
	const u8 length[2] = { 0x00, 0x01 };
	u8 m[53], t[16];
	int err;

	SMP_DBG("w %32phN", w);
	SMP_DBG("n1 %16phN n2 %16phN", n1, n2);
	SMP_DBG("a1 %7phN a2 %7phN", a1, a2);

	err = aes_cmac(tfm_cmac, salt, w, 32, t);
	if (err)
		return err;

	SMP_DBG("t %16phN", t);

	memcpy(m, length, 2);
	memcpy(m + 2, a2, 7);
	memcpy(m + 9, a1, 7);
	memcpy(m + 16, n2, 16);
	memcpy(m + 32, n1, 16);
	memcpy(m + 48, btle, 4);

	m[52] = 0; /* Counter */

	err = aes_cmac(tfm_cmac, t, m, sizeof(m), mackey);
	if (err)
		return err;

	SMP_DBG("mackey %16phN", mackey);

	m[52] = 1; /* Counter */

	err = aes_cmac(tfm_cmac, t, m, sizeof(m), ltk);
	if (err)
		return err;

	SMP_DBG("ltk %16phN", ltk);

	return 0;
}

static int smp_f6(struct crypto_hash *tfm_cmac, const u8 w[16],
		  const u8 n1[16], const u8 n2[16], const u8 r[16],
		  const u8 io_cap[3], const u8 a1[7], const u8 a2[7],
		  u8 res[16])
{
	u8 m[65];
	int err;

	SMP_DBG("w %16phN", w);
	SMP_DBG("n1 %16phN n2 %16phN", n1, n2);
	SMP_DBG("r %16phN io_cap %3phN a1 %7phN a2 %7phN", r, io_cap, a1, a2);

	memcpy(m, a2, 7);
	memcpy(m + 7, a1, 7);
	memcpy(m + 14, io_cap, 3);
	memcpy(m + 17, r, 16);
	memcpy(m + 33, n2, 16);
	memcpy(m + 49, n1, 16);

	err = aes_cmac(tfm_cmac, w, m, sizeof(m), res);
	if (err)
		return err;

	SMP_DBG("res %16phN", res);

	return err;
}

static int smp_g2(struct crypto_hash *tfm_cmac, const u8 u[32], const u8 v[32],
		  const u8 x[16], const u8 y[16], u32 *val)
{
	u8 m[80], tmp[16];
	int err;

	SMP_DBG("u %32phN", u);
	SMP_DBG("v %32phN", v);
	SMP_DBG("x %16phN y %16phN", x, y);

	memcpy(m, y, 16);
	memcpy(m + 16, v, 32);
	memcpy(m + 48, u, 32);

	err = aes_cmac(tfm_cmac, x, m, sizeof(m), tmp);
	if (err)
		return err;

	*val = get_unaligned_le32(tmp);
	*val %= 1000000;

	SMP_DBG("val %06u", *val);

	return 0;
}

static int smp_h6(struct crypto_hash *tfm_cmac, const u8 w[16],
		  const u8 key_id[4], u8 res[16])
{
	int err;

	SMP_DBG("w %16phN key_id %4phN", w, key_id);

	err = aes_cmac(tfm_cmac, w, key_id, 4, 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.
 */

static int smp_e(struct crypto_blkcipher *tfm, const u8 *k, u8 *r)
{
	struct blkcipher_desc desc;
	struct scatterlist sg;
	uint8_t tmp[16], data[16];
	int err;

	SMP_DBG("k %16phN r %16phN", k, r);

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

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

	/* The most significant octet of key corresponds to k[0] */
	swap_buf(k, tmp, 16);

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

	/* Most significant octet of plaintextData corresponds to data[0] */
	swap_buf(r, data, 16);

	sg_init_one(&sg, data, 16);

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

	/* Most significant octet of encryptedData corresponds to data[0] */
	swap_buf(data, r, 16);

	SMP_DBG("r %16phN", r);

	return err;
}

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

	SMP_DBG("k %16phN r %16phN", k, r);
	SMP_DBG("iat %u ia %6phN rat %u ra %6phN", _iat, ia, _rat, ra);
	SMP_DBG("preq %7phN pres %7phN", preq, pres);

	memset(p1, 0, 16);

	/* p1 = pres || preq || _rat || _iat */
	p1[0] = _iat;
	p1[1] = _rat;
	memcpy(p1 + 2, preq, 7);
	memcpy(p1 + 9, pres, 7);

	SMP_DBG("p1 %16phN", p1);

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

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

	/* p2 = padding || ia || ra */
	memcpy(p2, ra, 6);
	memcpy(p2 + 6, ia, 6);
	memset(p2 + 12, 0, 4);

	SMP_DBG("p2 %16phN", p2);

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

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

	return err;
}

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

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

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

	return err;
}

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

	/* r' = padding || r */
	memcpy(_res, r, 3);
	memset(_res + 3, 0, 13);

	err = smp_e(tfm, irk, _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.
	 */
	memcpy(res, _res, 3);

	return 0;
}

bool smp_irk_matches(struct hci_dev *hdev, const u8 irk[16],
		     const bdaddr_t *bdaddr)
{
	struct l2cap_chan *chan = hdev->smp_data;
	struct smp_dev *smp;
	u8 hash[3];
	int err;

	if (!chan || !chan->data)
		return false;

	smp = chan->data;

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

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

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

int smp_generate_rpa(struct hci_dev *hdev, const u8 irk[16], bdaddr_t *rpa)
{
	struct l2cap_chan *chan = hdev->smp_data;
	struct smp_dev *smp;
	int err;

	if (!chan || !chan->data)
		return -EOPNOTSUPP;

	smp = chan->data;

	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(smp->tfm_aes, irk, &rpa->b[3], rpa->b);
	if (err < 0)
		return err;

	BT_DBG("RPA %pMR", rpa);

	return 0;
}

int smp_generate_oob(struct hci_dev *hdev, u8 hash[16], u8 rand[16])
{
	struct l2cap_chan *chan = hdev->smp_data;
	struct smp_dev *smp;
	int err;

	if (!chan || !chan->data)
		return -EOPNOTSUPP;

	smp = chan->data;

	if (hci_dev_test_flag(hdev, HCI_USE_DEBUG_KEYS)) {
		BT_DBG("Using debug keys");
		memcpy(smp->local_pk, debug_pk, 64);
		memcpy(smp->local_sk, debug_sk, 32);
		smp->debug_key = true;
	} else {
		while (true) {
			/* Generate local key pair for Secure Connections */
			if (!ecc_make_key(smp->local_pk, smp->local_sk))
				return -EIO;

			/* This is unlikely, but we need to check that
			 * we didn't accidentially generate a debug key.
			 */
			if (memcmp(smp->local_sk, debug_sk, 32))
				break;
		}
		smp->debug_key = false;
	}

	SMP_DBG("OOB Public Key X: %32phN", smp->local_pk);
	SMP_DBG("OOB Public Key Y: %32phN", smp->local_pk + 32);
	SMP_DBG("OOB Private Key:  %32phN", smp->local_sk);

	get_random_bytes(smp->local_rand, 16);

	err = smp_f4(smp->tfm_cmac, smp->local_pk, smp->local_pk,
		     smp->local_rand, 0, hash);
	if (err < 0)
		return err;

	memcpy(rand, smp->local_rand, 16);

	return 0;
}

static void smp_send_cmd(struct l2cap_conn *conn, u8 code, u16 len, void *data)
{
	struct l2cap_chan *chan = conn->smp;
	struct smp_chan *smp;
	struct kvec iv[2];
	struct msghdr msg;

	if (!chan)
		return;

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

	iv[0].iov_base = &code;
	iv[0].iov_len = 1;

	iv[1].iov_base = data;
	iv[1].iov_len = len;

	memset(&msg, 0, sizeof(msg));

	iov_iter_kvec(&msg.msg_iter, WRITE | ITER_KVEC, iv, 2, 1 + len);

	l2cap_chan_send(chan, &msg, 1 + len);

	if (!chan->data)
		return;

	smp = chan->data;

	cancel_delayed_work_sync(&smp->security_timer);
	schedule_delayed_work(&smp->security_timer, SMP_TIMEOUT);
}

static u8 authreq_to_seclevel(u8 authreq)
{
	if (authreq & SMP_AUTH_MITM) {
		if (authreq & SMP_AUTH_SC)
			return BT_SECURITY_FIPS;
		else
			return BT_SECURITY_HIGH;
	} else {
		return BT_SECURITY_MEDIUM;
	}
}

static __u8 seclevel_to_authreq(__u8 sec_level)
{
	switch (sec_level) {
	case BT_SECURITY_FIPS:
	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 l2cap_chan *chan = conn->smp;
	struct smp_chan *smp = chan->data;
	struct hci_conn *hcon = conn->hcon;
	struct hci_dev *hdev = hcon->hdev;
	u8 local_dist = 0, remote_dist = 0, oob_flag = SMP_OOB_NOT_PRESENT;

	if (hci_dev_test_flag(hdev, HCI_BONDABLE)) {
		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 (hci_dev_test_flag(hdev, HCI_RPA_RESOLVING))
		remote_dist |= SMP_DIST_ID_KEY;

	if (hci_dev_test_flag(hdev, HCI_PRIVACY))
		local_dist |= SMP_DIST_ID_KEY;

	if (hci_dev_test_flag(hdev, HCI_SC_ENABLED) &&
	    (authreq & SMP_AUTH_SC)) {
		struct oob_data *oob_data;
		u8 bdaddr_type;

		if (hci_dev_test_flag(hdev, HCI_SSP_ENABLED)) {
			local_dist |= SMP_DIST_LINK_KEY;
			remote_dist |= SMP_DIST_LINK_KEY;
		}

		if (hcon->dst_type == ADDR_LE_DEV_PUBLIC)
			bdaddr_type = BDADDR_LE_PUBLIC;
		else
			bdaddr_type = BDADDR_LE_RANDOM;

		oob_data = hci_find_remote_oob_data(hdev, &hcon->dst,
						    bdaddr_type);
		if (oob_data && oob_data->present) {
			set_bit(SMP_FLAG_REMOTE_OOB, &smp->flags);
			oob_flag = SMP_OOB_PRESENT;
			memcpy(smp->rr, oob_data->rand256, 16);
			memcpy(smp->pcnf, oob_data->hash256, 16);
			SMP_DBG("OOB Remote Confirmation: %16phN", smp->pcnf);
			SMP_DBG("OOB Remote Random: %16phN", smp->rr);
		}

	} else {
		authreq &= ~SMP_AUTH_SC;
	}

	if (rsp == NULL) {
		req->io_capability = conn->hcon->io_capability;
		req->oob_flag = oob_flag;
		req->max_key_size = SMP_DEV(hdev)->max_key_size;
		req->init_key_dist = local_dist;
		req->resp_key_dist = remote_dist;
		req->auth_req = (authreq & AUTH_REQ_MASK(hdev));

		smp->remote_key_dist = remote_dist;
		return;
	}

	rsp->io_capability = conn->hcon->io_capability;
	rsp->oob_flag = oob_flag;
	rsp->max_key_size = SMP_DEV(hdev)->max_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(hdev));

	smp->remote_key_dist = rsp->init_key_dist;
}

static u8 check_enc_key_size(struct l2cap_conn *conn, __u8 max_key_size)
{
	struct l2cap_chan *chan = conn->smp;
	struct hci_dev *hdev = conn->hcon->hdev;
	struct smp_chan *smp = chan->data;

	if (max_key_size > SMP_DEV(hdev)->max_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_chan_destroy(struct l2cap_conn *conn)
{
	struct l2cap_chan *chan = conn->smp;
	struct smp_chan *smp = chan->data;
	struct hci_conn *hcon = conn->hcon;
	bool complete;

	BUG_ON(!smp);

	cancel_delayed_work_sync(&smp->security_timer);

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

	kzfree(smp->csrk);
	kzfree(smp->slave_csrk);
	kzfree(smp->link_key);

	crypto_free_blkcipher(smp->tfm_aes);
	crypto_free_hash(smp->tfm_cmac);

	/* Ensure that we don't leave any debug key around if debug key
	 * support hasn't been explicitly enabled.
	 */
	if (smp->ltk && smp->ltk->type == SMP_LTK_P256_DEBUG &&
	    !hci_dev_test_flag(hcon->hdev, HCI_KEEP_DEBUG_KEYS)) {
		list_del_rcu(&smp->ltk->list);
		kfree_rcu(smp->ltk, rcu);
		smp->ltk = NULL;
	}

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

		if (smp->slave_ltk) {
			list_del_rcu(&smp->slave_ltk->list);
			kfree_rcu(smp->slave_ltk, rcu);
		}

		if (smp->remote_irk) {
			list_del_rcu(&smp->remote_irk->list);
			kfree_rcu(smp->remote_irk, rcu);
		}
	}

	chan->data = NULL;
	kzfree(smp);
	hci_conn_drop(hcon);
}

static void smp_failure(struct l2cap_conn *conn, u8 reason)
{
	struct hci_conn *hcon = conn->hcon;
	struct l2cap_chan *chan = conn->smp;

	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, HCI_ERROR_AUTH_FAILURE);

	if (chan->data)
		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 DSP_PASSKEY	0x05
#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 const u8 sc_method[5][5] = {
	{ JUST_WORKS,  JUST_CFM,    REQ_PASSKEY, JUST_WORKS, REQ_PASSKEY },
	{ JUST_WORKS,  CFM_PASSKEY, REQ_PASSKEY, JUST_WORKS, CFM_PASSKEY },
	{ DSP_PASSKEY, DSP_PASSKEY, REQ_PASSKEY, JUST_WORKS, DSP_PASSKEY },
	{ JUST_WORKS,  JUST_CFM,    JUST_WORKS,  JUST_WORKS, JUST_CFM    },
	{ DSP_PASSKEY, CFM_PASSKEY, REQ_PASSKEY, JUST_WORKS, CFM_PASSKEY },
};

static u8 get_auth_method(struct smp_chan *smp, u8 local_io, u8 remote_io)
{
	/* If either side has unknown io_caps, use JUST_CFM (which gets
	 * converted later to JUST_WORKS if we're initiators.
	 */
	if (local_io > SMP_IO_KEYBOARD_DISPLAY ||
	    remote_io > SMP_IO_KEYBOARD_DISPLAY)
		return JUST_CFM;

	if (test_bit(SMP_FLAG_SC, &smp->flags))
		return sc_method[remote_io][local_io];

	return gen_method[remote_io][local_io];
}

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 l2cap_chan *chan = conn->smp;
	struct smp_chan *smp = chan->data;
	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->flags);

	BT_DBG("tk_request: auth:%d lcl:%d rem:%d", auth, local_io, remote_io);

	/* If neither side wants MITM, either "just" confirm an incoming
	 * request or use just-works for outgoing ones. The JUST_CFM
	 * will be converted to JUST_WORKS if necessary later in this
	 * function. If either side has MITM look up the method from the
	 * table.
	 */
	if (!(auth & SMP_AUTH_MITM))
		smp->method = JUST_CFM;
	else
		smp->method = get_auth_method(smp, local_io, remote_io);

	/* Don't confirm locally initiated pairing attempts */
	if (smp->method == JUST_CFM && test_bit(SMP_FLAG_INITIATOR,
						&smp->flags))
		smp->method = JUST_WORKS;

	/* Don't bother user space with no IO capabilities */
	if (smp->method == JUST_CFM &&
	    hcon->io_capability == HCI_IO_NO_INPUT_OUTPUT)
		smp->method = JUST_WORKS;

	/* If Just Works, Continue with Zero TK */
	if (smp->method == JUST_WORKS) {
		set_bit(SMP_FLAG_TK_VALID, &smp->flags);
		return 0;
	}

	/* If this function is used for SC -> legacy fallback we
	 * can only recover the just-works case.
	 */
	if (test_bit(SMP_FLAG_SC, &smp->flags))
		return -EINVAL;

	/* Not Just Works/Confirm results in MITM Authentication */
	if (smp->method != JUST_CFM) {
		set_bit(SMP_FLAG_MITM_AUTH, &smp->flags);
		if (hcon->pending_sec_level < BT_SECURITY_HIGH)
			hcon->pending_sec_level = BT_SECURITY_HIGH;
	}

	/* If both devices have Keyoard-Display I/O, the master
	 * Confirms and the slave Enters the passkey.
	 */
	if (smp->method == OVERLAP) {
		if (hcon->role == HCI_ROLE_MASTER)
			smp->method = CFM_PASSKEY;
		else
			smp->method = REQ_PASSKEY;
	}

	/* Generate random passkey. */
	if (smp->method == CFM_PASSKEY) {
		memset(smp->tk, 0, sizeof(smp->tk));
		get_random_bytes(&passkey, sizeof(passkey));
		passkey %= 1000000;
		put_unaligned_le32(passkey, smp->tk);
		BT_DBG("PassKey: %d", passkey);
		set_bit(SMP_FLAG_TK_VALID, &smp->flags);
	}

	if (smp->method == REQ_PASSKEY)
		ret = mgmt_user_passkey_request(hcon->hdev, &hcon->dst,
						hcon->type, hcon->dst_type);
	else if (smp->method == JUST_CFM)
		ret = mgmt_user_confirm_request(hcon->hdev, &hcon->dst,
						hcon->type, hcon->dst_type,
						passkey, 1);
	else
		ret = mgmt_user_passkey_notify(hcon->hdev, &hcon->dst,
						hcon->type, hcon->dst_type,
						passkey, 0);

	return ret;
}

static u8 smp_confirm(struct smp_chan *smp)
{
	struct l2cap_conn *conn = smp->conn;
	struct smp_cmd_pairing_confirm cp;
	int ret;

	BT_DBG("conn %p", conn);

	ret = smp_c1(smp->tfm_aes, 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,
		     cp.confirm_val);
	if (ret)
		return SMP_UNSPECIFIED;

	clear_bit(SMP_FLAG_CFM_PENDING, &smp->flags);

	smp_send_cmd(smp->conn, SMP_CMD_PAIRING_CONFIRM, sizeof(cp), &cp);

	if (conn->hcon->out)
		SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_CONFIRM);
	else
		SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_RANDOM);

	return 0;
}

static u8 smp_random(struct smp_chan *smp)
{
	struct l2cap_conn *conn = smp->conn;
	struct hci_conn *hcon = conn->hcon;
	u8 confirm[16];
	int ret;

	if (IS_ERR_OR_NULL(smp->tfm_aes))
		return SMP_UNSPECIFIED;

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

	ret = smp_c1(smp->tfm_aes, smp->tk, smp->rrnd, smp->preq, smp->prsp,
		     hcon->init_addr_type, &hcon->init_addr,
		     hcon->resp_addr_type, &hcon->resp_addr, confirm);
	if (ret)
		return SMP_UNSPECIFIED;

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

	if (hcon->out) {