/*
   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/scatterlist.h>
#include <linux/crypto.h>
#include <crypto/aes.h>
#include <crypto/algapi.h>
#include <crypto/hash.h>
#include <crypto/kpp.h>

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

#include "ecdh_helper.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
 * accidentally 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) ? \
                                 0x3f : 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,
        SMP_FLAG_CT2,
};

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

        struct crypto_shash     *tfm_cmac;
        struct crypto_kpp       *tfm_ecdh;
};

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 *responder_csrk;
        struct smp_ltk  *ltk;
        struct smp_ltk  *responder_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                      remote_pk[64];
        u8                      dhkey[32];
        u8                      mackey[16];

        struct crypto_shash     *tfm_cmac;
        struct crypto_kpp       *tfm_ecdh;
};

/* 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_shash *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];
        int err;

        if (len > CMAC_MSG_MAX)
                return -EFBIG;

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

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

        err = crypto_shash_tfm_digest(tfm, msg_msb, len, mac_msb);
        if (err) {
                BT_ERR("Hash computation error %d", err);
                return err;
        }

        swap_buf(mac_msb, mac, 16);

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

        return 0;
}

static int smp_f4(struct crypto_shash *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_shash *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_shash *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_shash *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_shash *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;
}

static int smp_h7(struct crypto_shash *tfm_cmac, const u8 w[16],
                  const u8 salt[16], u8 res[16])
{
        int err;

        SMP_DBG("w %16phN salt %16phN", w, salt);

        err = aes_cmac(tfm_cmac, salt, w, 16, 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(const u8 *k, u8 *r)
{
        struct crypto_aes_ctx ctx;
        uint8_t tmp[16], data[16];
        int err;

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

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

        err = aes_expandkey(&ctx, 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);

        aes_encrypt(&ctx, data, data);

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

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

        memzero_explicit(&ctx, sizeof(ctx));
        return err;
}

static int smp_c1(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 */
        crypto_xor_cpy(res, r, p1, sizeof(p1));

        /* res = e(k, res) */
        err = smp_e(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 */
        crypto_xor(res, p2, sizeof(p2));

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

        return err;
}

static int smp_s1(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(k, _r);
        if (err)
                BT_ERR("Encrypt data error");

        return err;
}

static int smp_ah(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(irk, _res);
        if (err) {
                BT_ERR("Encrypt error");
                return err;
        }

        /* The output of the random address function ah is:
         *      ah(k, 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;
        u8 hash[3];
        int err;

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

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

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

        return !crypto_memneq(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;
        int err;

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

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

        bt_dev_dbg(hdev, "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_dev_dbg(hdev, "Using debug keys");
                err = set_ecdh_privkey(smp->tfm_ecdh, debug_sk);
                if (err)
                        return err;
                memcpy(smp->local_pk, debug_pk, 64);
                smp->debug_key = true;
        } else {
                while (true) {
                        /* Generate key pair for Secure Connections */
                        err = generate_ecdh_keys(smp->tfm_ecdh, smp->local_pk);
                        if (err)
                                return err;

                        /* This is unlikely, but we need to check that
                         * we didn't accidentally generate a debug key.
                         */
                        if (crypto_memneq(smp->local_pk, debug_pk, 64))
                                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);

        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);

        smp->local_oob = true;

        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_dev_dbg(conn->hcon->hdev, "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, 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 = hdev->le_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 = hdev->le_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 (conn->hcon->pending_sec_level == BT_SECURITY_FIPS &&
            max_key_size != SMP_MAX_ENC_KEY_SIZE)
                return SMP_ENC_KEY_SIZE;

        if (max_key_size > hdev->le_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);

        kfree_sensitive(smp->csrk);
        kfree_sensitive(smp->responder_csrk);
        kfree_sensitive(smp->link_key);

        crypto_free_shash(smp->tfm_cmac);
        crypto_free_kpp(smp->tfm_ecdh);

        /* 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->responder_ltk) {
                        list_del_rcu(&smp->responder_ltk->list);
                        kfree_rcu(smp->responder_ltk, rcu);
                }

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

        chan->data = NULL;
        kfree_sensitive(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);

        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;

        /* Initialize key for JUST WORKS */
        memset(smp->tk, 0, sizeof(smp->tk));
        clear_bit(SMP_FLAG_TK_VALID, &smp->flags);

        bt_dev_dbg(hcon->hdev, "auth:%u lcl:%u rem:%u", 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 and ask user-space for
         * confirmation */
        if (smp->method == JUST_WORKS) {
                ret = mgmt_user_confirm_request(hcon->hdev, &hcon->dst,
                                                hcon->type,
                                                hcon->dst_type,
                                                passkey, 1);
                if (ret)
                        return ret;
                set_bit(SMP_FLAG_WAIT_USER, &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 Keyboard-Display I/O, the initiator
         * Confirms and the responder 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_dev_dbg(hcon->hdev, "PassKey: %u", 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_dev_dbg(conn->hcon->hdev, "conn %p", conn);

        ret = smp_c1(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;

        bt_dev_dbg(conn->hcon->hdev, "conn %p %s", conn,
                   conn->hcon->out ? "initiator" : "responder");

        ret = smp_c1(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 (crypto_memneq(smp->pcnf, confirm, sizeof(smp->pcnf))) {
                bt_dev_err(hcon->hdev, "pairing failed "
                           "(confirmation values mismatch)");
                return SMP_CONFIRM_FAILED;
        }

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

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

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

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

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

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

                if (hcon->pending_sec_level == BT_SECURITY_HIGH)
                        auth = 1;
                else
                        auth = 0;

                /* Even though there's no _RESPONDER suffix this is the
                 * responder STK we're adding for later lookup (the initiator
                 * STK never needs to be stored).
                 */
                hci_add_ltk(hcon->hdev, &hcon->dst, hcon->dst_type,
                            SMP_STK, auth, stk, smp->enc_key_size, ediv, rand);
        }

        return 0;
}

static void smp_notify_keys(struct l2cap_conn *conn)
{
        struct l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;
        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 (hcon->type == ACL_LINK) {
                if (hcon->key_type == HCI_LK_DEBUG_COMBINATION)
                        persistent = false;
                else
                        persistent = !test_bit(HCI_CONN_FLUSH_KEY,
                                               &hcon->flags);
        } else {
                /* The LTKs, IRKs 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->remote_irk) {
                mgmt_new_irk(hdev, smp->remote_irk, persistent);

                /* Now that user space can be considered to know the
                 * identity address track the connection based on it
                 * from now on (assuming this is an LE link).
                 */
                if (hcon->type == LE_LINK) {
                        bacpy(&hcon->dst, &smp->remote_irk->bdaddr);
                        hcon->dst_type = smp->remote_irk->addr_type;
                        queue_work(hdev->workqueue, &conn->id_addr_update_work);
                }
        }

        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->responder_csrk) {
                smp->responder_csrk->bdaddr_type = hcon->dst_type;
                bacpy(&smp->responder_csrk->bdaddr, &hcon->dst);
                mgmt_new_csrk(hdev, smp->responder_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->responder_ltk) {
                smp->responder_ltk->bdaddr_type = hcon->dst_type;
                bacpy(&smp->responder_ltk->bdaddr, &hcon->dst);
                mgmt_new_ltk(hdev, smp->responder_ltk, persistent);
        }

        if (smp->link_key) {
                struct link_key *key;
                u8 type;

                if (test_bit(SMP_FLAG_DEBUG_KEY, &smp->flags))
                        type = HCI_LK_DEBUG_COMBINATION;
                else if (hcon->sec_level == BT_SECURITY_FIPS)
                        type = HCI_LK_AUTH_COMBINATION_P256;
                else
                        type = HCI_LK_UNAUTH_COMBINATION_P256;

                key = hci_add_link_key(hdev, smp->conn->hcon, &hcon->dst,
                                       smp->link_key, type, 0, &persistent);
                if (key) {
                        mgmt_new_link_key(hdev, key, persistent);

                        /* Don't keep debug keys around if the relevant
                         * flag is not set.
                         */
                        if (!hci_dev_test_flag(hdev, HCI_KEEP_DEBUG_KEYS) &&
                            key->type == HCI_LK_DEBUG_COMBINATION) {
                                list_del_rcu(&key->list);
                                kfree_rcu(key, rcu);
                        }
                }
        }
}

static void sc_add_ltk(struct smp_chan *smp)
{
        struct hci_conn *hcon = smp->conn->hcon;
        u8 key_type, auth;

        if (test_bit(SMP_FLAG_DEBUG_KEY, &smp->flags))
                key_type = SMP_LTK_P256_DEBUG;
        else
                key_type = SMP_LTK_P256;

        if (hcon->pending_sec_level == BT_SECURITY_FIPS)
                auth = 1;
        else
                auth = 0;

        smp->ltk = hci_add_ltk(hcon->hdev, &hcon->dst, hcon->dst_type,
                               key_type, auth, smp->tk, smp->enc_key_size,
                               0, 0);
}

static void sc_generate_link_key(struct smp_chan *smp)
{
        /* From core spec. Spells out in ASCII as 'lebr'. */
        const u8 lebr[4] = { 0x72, 0x62, 0x65, 0x6c };

        smp->link_key = kzalloc(16, GFP_KERNEL);
        if (!smp->link_key)
                return;

        if (test_bit(SMP_FLAG_CT2, &smp->flags)) {
                /* SALT = 0x000000000000000000000000746D7031 */
                const u8 salt[16] = { 0x31, 0x70, 0x6d, 0x74 };

                if (smp_h7(smp->tfm_cmac, smp->tk, salt, smp->link_key)) {
                        kfree_sensitive(smp->link_key);
                        smp->link_key = NULL;
                        return;
                }
        } else {
                /* From core spec. Spells out in ASCII as 'tmp1'. */
                const u8 tmp1[4] = { 0x31, 0x70, 0x6d, 0x74 };

                if (smp_h6(smp->tfm_cmac, smp->tk, tmp1, smp->link_key)) {
                        kfree_sensitive(smp->link_key);
                        smp->link_key = NULL;
                        return;
                }
        }

        if (smp_h6(smp->tfm_cmac, smp->link_key, lebr, smp->link_key)) {
                kfree_sensitive(smp->link_key);
                smp->link_key = NULL;
                return;
        }
}

static void smp_allow_key_dist(struct smp_chan *smp)
{
        /* Allow the first expected phase 3 PDU. The rest of the PDUs
         * will be allowed in each PDU handler to ensure we receive
         * them in the correct order.
         */
        if (smp->remote_key_dist & SMP_DIST_ENC_KEY)
                SMP_ALLOW_CMD(smp, SMP_CMD_ENCRYPT_INFO);
        else if (smp->remote_key_dist & SMP_DIST_ID_KEY)
                SMP_ALLOW_CMD(smp, SMP_CMD_IDENT_INFO);
        else if (smp->remote_key_dist & SMP_DIST_SIGN)
                SMP_ALLOW_CMD(smp, SMP_CMD_SIGN_INFO);
}

static void sc_generate_ltk(struct smp_chan *smp)
{
        /* From core spec. Spells out in ASCII as 'brle'. */
        const u8 brle[4] = { 0x65, 0x6c, 0x72, 0x62 };
        struct hci_conn *hcon = smp->conn->hcon;
        struct hci_dev *hdev = hcon->hdev;
        struct link_key *key;

        key = hci_find_link_key(hdev, &hcon->dst);
        if (!key) {
                bt_dev_err(hdev, "no Link Key found to generate LTK");
                return;
        }

        if (key->type == HCI_LK_DEBUG_COMBINATION)
                set_bit(SMP_FLAG_DEBUG_KEY, &smp->flags);

        if (test_bit(SMP_FLAG_CT2, &smp->flags)) {
                /* SALT = 0x000000000000000000000000746D7032 */
                const u8 salt[16] = { 0x32, 0x70, 0x6d, 0x74 };

                if (smp_h7(smp->tfm_cmac, key->val, salt, smp->tk))
                        return;
        } else {
                /* From core spec. Spells out in ASCII as 'tmp2'. */
                const u8 tmp2[4] = { 0x32, 0x70, 0x6d, 0x74 };

                if (smp_h6(smp->tfm_cmac, key->val, tmp2, smp->tk))
                        return;
        }

        if (smp_h6(smp->tfm_cmac, smp->tk, brle, smp->tk))
                return;

        sc_add_ltk(smp);
}

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

        bt_dev_dbg(hdev, "conn %p", conn);

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

        /* The responder sends its keys first */
        if (hcon->out && (smp->remote_key_dist & KEY_DIST_MASK)) {
                smp_allow_key_dist(smp);
                return;
        }

        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;
        }

        if (test_bit(SMP_FLAG_SC, &smp->flags)) {
                if (hcon->type == LE_LINK && (*keydist & SMP_DIST_LINK_KEY))
                        sc_generate_link_key(smp);
                if (hcon->type == ACL_LINK && (*keydist & SMP_DIST_ENC_KEY))
                        sc_generate_ltk(smp);

                /* Clear the keys which are generated but not distributed */
                *keydist &= ~SMP_SC_NO_DIST;
        }

        bt_dev_dbg(hdev, "keydist 0x%x", *keydist);

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

                /* Make sure we generate only the significant amount of
                 * bytes based on the encryption key size, and set the rest
                 * of the value to zeroes.
                 */
                get_random_bytes(enc.ltk, smp->enc_key_size);
                memset(enc.ltk + smp->enc_key_size, 0,
                       sizeof(enc.ltk) - smp->enc_key_size);

                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,
                                  SMP_LTK_RESPONDER, authenticated, enc.ltk,
                                  smp->enc_key_size, ediv, rand);
                smp->responder_ltk = ltk;

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

                smp_send_cmd(conn, SMP_CMD_INITIATOR_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) {
                        if (hcon->sec_level > BT_SECURITY_MEDIUM)
                                csrk->type = MGMT_CSRK_LOCAL_AUTHENTICATED;
                        else
                                csrk->type = MGMT_CSRK_LOCAL_UNAUTHENTICATED;
                        memcpy(csrk->val, sign.csrk, sizeof(csrk->val));
                }
                smp->responder_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 & KEY_DIST_MASK) {
                smp_allow_key_dist(smp);
                return;
        }

        set_bit(SMP_FLAG_COMPLETE, &smp->flags);
        smp_notify_keys(conn);

        smp_chan_destroy(conn);
}

static void smp_timeout(struct work_struct *work)
{
        struct smp_chan *smp = container_of(work, struct smp_chan,
                                            security_timer.work);
        struct l2cap_conn *conn = smp->conn;

        bt_dev_dbg(conn->hcon->hdev, "conn %p", conn);

        hci_disconnect(conn->hcon, HCI_ERROR_REMOTE_USER_TERM);
}

static struct smp_chan *smp_chan_create(struct l2cap_conn *conn)
{
        struct hci_conn *hcon = conn->hcon;
        struct l2cap_chan *chan = conn->smp;
        struct smp_chan *smp;

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

        smp->tfm_cmac = crypto_alloc_shash("cmac(aes)", 0, 0);
        if (IS_ERR(smp->tfm_cmac)) {
                bt_dev_err(hcon->hdev, "Unable to create CMAC crypto context");
                goto zfree_smp;
        }

        smp->tfm_ecdh = crypto_alloc_kpp("ecdh-nist-p256", 0, 0);
        if (IS_ERR(smp->tfm_ecdh)) {
                bt_dev_err(hcon->hdev, "Unable to create ECDH crypto context");
                goto free_shash;
        }

        smp->conn = conn;
        chan->data = smp;

        SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_FAIL);

        INIT_DELAYED_WORK(&smp->security_timer, smp_timeout);

        hci_conn_hold(hcon);

        return smp;

free_shash:
        crypto_free_shash(smp->tfm_cmac);
zfree_smp:
        kfree_sensitive(smp);
        return NULL;
}

static int sc_mackey_and_ltk(struct smp_chan *smp, u8 mackey[16], u8 ltk[16])
{
        struct hci_conn *hcon = smp->conn->hcon;
        u8 *na, *nb, a[7], b[7];

        if (hcon->out) {
                na   = smp->prnd;
                nb   = smp->rrnd;
        } else {
                na   = smp->rrnd;
                nb   = smp->prnd;
        }

        memcpy(a, &hcon->init_addr, 6);
        memcpy(b, &hcon->resp_addr, 6);
        a[6] = hcon->init_addr_type;
        b[6] = hcon->resp_addr_type;

        return smp_f5(smp->tfm_cmac, smp->dhkey, na, nb, a, b, mackey, ltk);
}

static void sc_dhkey_check(struct smp_chan *smp)
{
        struct hci_conn *hcon = smp->conn->hcon;
        struct smp_cmd_dhkey_check check;
        u8 a[7], b[7], *local_addr, *remote_addr;
        u8 io_cap[3], r[16];

        memcpy(a, &hcon->init_addr, 6);
        memcpy(b, &hcon->resp_addr, 6);
        a[6] = hcon->init_addr_type;
        b[6] = hcon->resp_addr_type;

        if (hcon->out) {
                local_addr = a;
                remote_addr = b;
                memcpy(io_cap, &smp->preq[1], 3);
        } else {
                local_addr = b;
                remote_addr = a;
                memcpy(io_cap, &smp->prsp[1], 3);
        }

        memset(r, 0, sizeof(r));

        if (smp->method == REQ_PASSKEY || smp->method == DSP_PASSKEY)
                put_unaligned_le32(hcon->passkey_notify, r);

        if (smp->method == REQ_OOB)
                memcpy(r, smp->rr, 16);

        smp_f6(smp->tfm_cmac, smp->mackey, smp->prnd, smp->rrnd, r, io_cap,
               local_addr, remote_addr, check.e);

        smp_send_cmd(smp->conn, SMP_CMD_DHKEY_CHECK, sizeof(check), &check);
}

static u8 sc_passkey_send_confirm(struct smp_chan *smp)
{
        struct l2cap_conn *conn = smp->conn;
        struct hci_conn *hcon = conn->hcon;
        struct smp_cmd_pairing_confirm cfm;
        u8 r;

        r = ((hcon->passkey_notify >> smp->passkey_round) & 0x01);
        r |= 0x80;

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

        if (smp_f4(smp->tfm_cmac, smp->local_pk, smp->remote_pk, smp->prnd, r,
                   cfm.confirm_val))
                return SMP_UNSPECIFIED;

        smp_send_cmd(conn, SMP_CMD_PAIRING_CONFIRM, sizeof(cfm), &cfm);

        return 0;
}

static u8 sc_passkey_round(struct smp_chan *smp, u8 smp_op)
{
        struct l2cap_conn *conn = smp->conn;
        struct hci_conn *hcon = conn->hcon;
        struct hci_dev *hdev = hcon->hdev;
        u8 cfm[16], r;

        /* Ignore the PDU if we've already done 20 rounds (0 - 19) */
        if (smp->passkey_round >= 20)
                return 0;

        switch (smp_op) {
        case SMP_CMD_PAIRING_RANDOM:
                r = ((hcon->passkey_notify >> smp->passkey_round) & 0x01);
                r |= 0x80;

                if (smp_f4(smp->tfm_cmac, smp->remote_pk, smp->local_pk,
                           smp->rrnd, r, cfm))
                        return SMP_UNSPECIFIED;

                if (crypto_memneq(smp->pcnf, cfm, 16))
                        return SMP_CONFIRM_FAILED;

                smp->passkey_round++;

                if (smp->passkey_round == 20) {
                        /* Generate MacKey and LTK */
                        if (sc_mackey_and_ltk(smp, smp->mackey, smp->tk))
                                return SMP_UNSPECIFIED;
                }

                /* The round is only complete when the initiator
                 * receives pairing random.
                 */
                if (!hcon->out) {
                        smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM,
                                     sizeof(smp->prnd), smp->prnd);
                        if (smp->passkey_round == 20)
                                SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
                        else
                                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_CONFIRM);
                        return 0;
                }

                /* Start the next round */
                if (smp->passkey_round != 20)
                        return sc_passkey_round(smp, 0);

                /* Passkey rounds are complete - start DHKey Check */
                sc_dhkey_check(smp);
                SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);

                break;

        case SMP_CMD_PAIRING_CONFIRM:
                if (test_bit(SMP_FLAG_WAIT_USER, &smp->flags)) {
                        set_bit(SMP_FLAG_CFM_PENDING, &smp->flags);
                        return 0;
                }

                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_RANDOM);

                if (hcon->out) {
                        smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM,
                                     sizeof(smp->prnd), smp->prnd);
                        return 0;
                }

                return sc_passkey_send_confirm(smp);

        case SMP_CMD_PUBLIC_KEY:
        default:
                /* Initiating device starts the round */
                if (!hcon->out)
                        return 0;

                bt_dev_dbg(hdev, "Starting passkey round %u",
                           smp->passkey_round + 1);

                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_CONFIRM);

                return sc_passkey_send_confirm(smp);
        }

        return 0;
}

static int sc_user_reply(struct smp_chan *smp, u16 mgmt_op, __le32 passkey)
{
        struct l2cap_conn *conn = smp->conn;
        struct hci_conn *hcon = conn->hcon;
        u8 smp_op;

        clear_bit(SMP_FLAG_WAIT_USER, &smp->flags);

        switch (mgmt_op) {
        case MGMT_OP_USER_PASSKEY_NEG_REPLY:
                smp_failure(smp->conn, SMP_PASSKEY_ENTRY_FAILED);
                return 0;
        case MGMT_OP_USER_CONFIRM_NEG_REPLY:
                smp_failure(smp->conn, SMP_NUMERIC_COMP_FAILED);
                return 0;
        case MGMT_OP_USER_PASSKEY_REPLY:
                hcon->passkey_notify = le32_to_cpu(passkey);
                smp->passkey_round = 0;

                if (test_and_clear_bit(SMP_FLAG_CFM_PENDING, &smp->flags))
                        smp_op = SMP_CMD_PAIRING_CONFIRM;
                else
                        smp_op = 0;

                if (sc_passkey_round(smp, smp_op))
                        return -EIO;

                return 0;
        }

        /* Initiator sends DHKey check first */
        if (hcon->out) {
                sc_dhkey_check(smp);
                SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
        } else if (test_and_clear_bit(SMP_FLAG_DHKEY_PENDING, &smp->flags)) {
                sc_dhkey_check(smp);
                sc_add_ltk(smp);
        }

        return 0;
}

int smp_user_confirm_reply(struct hci_conn *hcon, u16 mgmt_op, __le32 passkey)
{
        struct l2cap_conn *conn = hcon->l2cap_data;
        struct l2cap_chan *chan;
        struct smp_chan *smp;
        u32 value;
        int err;

        if (!conn)
                return -ENOTCONN;

        bt_dev_dbg(conn->hcon->hdev, "");

        chan = conn->smp;
        if (!chan)
                return -ENOTCONN;

        l2cap_chan_lock(chan);
        if (!chan->data) {
                err = -ENOTCONN;
                goto unlock;
        }

        smp = chan->data;

        if (test_bit(SMP_FLAG_SC, &smp->flags)) {
                err = sc_user_reply(smp, mgmt_op, passkey);
                goto unlock;
        }

        switch (mgmt_op) {
        case MGMT_OP_USER_PASSKEY_REPLY:
                value = le32_to_cpu(passkey);
                memset(smp->tk, 0, sizeof(smp->tk));
                bt_dev_dbg(conn->hcon->hdev, "PassKey: %u", value);
                put_unaligned_le32(value, smp->tk);
                fallthrough;
        case MGMT_OP_USER_CONFIRM_REPLY:
                set_bit(SMP_FLAG_TK_VALID, &smp->flags);
                break;
        case MGMT_OP_USER_PASSKEY_NEG_REPLY:
        case MGMT_OP_USER_CONFIRM_NEG_REPLY:
                smp_failure(conn, SMP_PASSKEY_ENTRY_FAILED);
                err = 0;
                goto unlock;
        default:
                smp_failure(conn, SMP_PASSKEY_ENTRY_FAILED);
                err = -EOPNOTSUPP;
                goto unlock;
        }

        err = 0;

        /* If it is our turn to send Pairing Confirm, do so now */
        if (test_bit(SMP_FLAG_CFM_PENDING, &smp->flags)) {
                u8 rsp = smp_confirm(smp);
                if (rsp)
                        smp_failure(conn, rsp);
        }

unlock:
        l2cap_chan_unlock(chan);
        return err;
}

static void build_bredr_pairing_cmd(struct smp_chan *smp,
                                    struct smp_cmd_pairing *req,
                                    struct smp_cmd_pairing *rsp)
{
        struct l2cap_conn *conn = smp->conn;
        struct hci_dev *hdev = conn->hcon->hdev;
        u8 local_dist = 0, remote_dist = 0;

        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;
        }

        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 (!rsp) {
                memset(req, 0, sizeof(*req));

                req->auth_req        = SMP_AUTH_CT2;
                req->init_key_dist   = local_dist;
                req->resp_key_dist   = remote_dist;
                req->max_key_size    = conn->hcon->enc_key_size;

                smp->remote_key_dist = remote_dist;

                return;
        }

        memset(rsp, 0, sizeof(*rsp));

        rsp->auth_req        = SMP_AUTH_CT2;
        rsp->max_key_size    = conn->hcon->enc_key_size;
        rsp->init_key_dist   = req->init_key_dist & remote_dist;
        rsp->resp_key_dist   = req->resp_key_dist & local_dist;

        smp->remote_key_dist = rsp->init_key_dist;
}

static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb)
{
        struct smp_cmd_pairing rsp, *req = (void *) skb->data;
        struct l2cap_chan *chan = conn->smp;
        struct hci_dev *hdev = conn->hcon->hdev;
        struct smp_chan *smp;
        u8 key_size, auth, sec_level;
        int ret;

        bt_dev_dbg(hdev, "conn %p", conn);

        if (skb->len < sizeof(*req))
                return SMP_INVALID_PARAMS;

        if (conn->hcon->role != HCI_ROLE_SLAVE)
                return SMP_CMD_NOTSUPP;

        if (!chan->data)
                smp = smp_chan_create(conn);
        else
                smp = chan->data;

        if (!smp)
                return SMP_UNSPECIFIED;

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

        if (!hci_dev_test_flag(hdev, HCI_BONDABLE) &&
            (auth & SMP_AUTH_BONDING))
                return SMP_PAIRING_NOTSUPP;

        if (hci_dev_test_flag(hdev, HCI_SC_ONLY) && !(auth & SMP_AUTH_SC))
                return SMP_AUTH_REQUIREMENTS;

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

        /* If the remote side's OOB flag is set it means it has
         * successfully received our local OOB data - therefore set the
         * flag to indicate that local OOB is in use.
         */
        if (req->oob_flag == SMP_OOB_PRESENT && SMP_DEV(hdev)->local_oob)
                set_bit(SMP_FLAG_LOCAL_OOB, &smp->flags);

        /* SMP over BR/EDR requires special treatment */
        if (conn->hcon->type == ACL_LINK) {
                /* We must have a BR/EDR SC link */
                if (!test_bit(HCI_CONN_AES_CCM, &conn->hcon->flags) &&
                    !hci_dev_test_flag(hdev, HCI_FORCE_BREDR_SMP))
                        return SMP_CROSS_TRANSP_NOT_ALLOWED;

                set_bit(SMP_FLAG_SC, &smp->flags);

                build_bredr_pairing_cmd(smp, req, &rsp);

                if (req->auth_req & SMP_AUTH_CT2)
                        set_bit(SMP_FLAG_CT2, &smp->flags);

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

                /* Clear bits which are generated but not distributed */
                smp->remote_key_dist &= ~SMP_SC_NO_DIST;

                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);

                smp_distribute_keys(smp);
                return 0;
        }

        build_pairing_cmd(conn, req, &rsp, auth);

        if (rsp.auth_req & SMP_AUTH_SC) {
                set_bit(SMP_FLAG_SC, &smp->flags);

                if (rsp.auth_req & SMP_AUTH_CT2)
                        set_bit(SMP_FLAG_CT2, &smp->flags);
        }

        if (conn->hcon->io_capability == HCI_IO_NO_INPUT_OUTPUT)
                sec_level = BT_SECURITY_MEDIUM;
        else
                sec_level = authreq_to_seclevel(auth);

        if (sec_level > conn->hcon->pending_sec_level)
                conn->hcon->pending_sec_level = sec_level;

        /* If we need MITM check that it can be achieved */
        if (conn->hcon->pending_sec_level >= BT_SECURITY_HIGH) {
                u8 method;

                method = get_auth_method(smp, conn->hcon->io_capability,
                                         req->io_capability);
                if (method == JUST_WORKS || method == JUST_CFM)
                        return SMP_AUTH_REQUIREMENTS;
        }

        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);

        clear_bit(SMP_FLAG_INITIATOR, &smp->flags);

        /* Strictly speaking we shouldn't allow Pairing Confirm for the
         * SC case, however some implementations incorrectly copy RFU auth
         * req bits from our security request, which may create a false
         * positive SC enablement.
         */
        SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_CONFIRM);

        if (test_bit(SMP_FLAG_SC, &smp->flags)) {
                SMP_ALLOW_CMD(smp, SMP_CMD_PUBLIC_KEY);
                /* Clear bits which are generated but not distributed */
                smp->remote_key_dist &= ~SMP_SC_NO_DIST;
                /* Wait for Public Key from Initiating Device */
                return 0;
        }

        /* 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 sc_send_public_key(struct smp_chan *smp)
{
        struct hci_dev *hdev = smp->conn->hcon->hdev;

        bt_dev_dbg(hdev, "");

        if (test_bit(SMP_FLAG_LOCAL_OOB, &smp->flags)) {
                struct l2cap_chan *chan = hdev->smp_data;
                struct smp_dev *smp_dev;

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

                smp_dev = chan->data;

                memcpy(smp->local_pk, smp_dev->local_pk, 64);
                memcpy(smp->lr, smp_dev->local_rand, 16);

                if (smp_dev->debug_key)
                        set_bit(SMP_FLAG_DEBUG_KEY, &smp->flags);

                goto done;
        }

        if (hci_dev_test_flag(hdev, HCI_USE_DEBUG_KEYS)) {
                bt_dev_dbg(hdev, "Using debug keys");
                if (set_ecdh_privkey(smp->tfm_ecdh, debug_sk))
                        return SMP_UNSPECIFIED;
                memcpy(smp->local_pk, debug_pk, 64);
                set_bit(SMP_FLAG_DEBUG_KEY, &smp->flags);
        } else {
                while (true) {
                        /* Generate key pair for Secure Connections */
                        if (generate_ecdh_keys(smp->tfm_ecdh, smp->local_pk))
                                return SMP_UNSPECIFIED;

                        /* This is unlikely, but we need to check that
                         * we didn't accidentally generate a debug key.
                         */
                        if (crypto_memneq(smp->local_pk, debug_pk, 64))
                                break;
                }
        }

done:
        SMP_DBG("Local Public Key X: %32phN", smp->local_pk);
        SMP_DBG("Local Public Key Y: %32phN", smp->local_pk + 32);

        smp_send_cmd(smp->conn, SMP_CMD_PUBLIC_KEY, 64, smp->local_pk);

        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 l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;
        struct hci_dev *hdev = conn->hcon->hdev;
        u8 key_size, auth;
        int ret;

        bt_dev_dbg(hdev, "conn %p", conn);

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

        if (conn->hcon->role != HCI_ROLE_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;

        auth = rsp->auth_req & AUTH_REQ_MASK(hdev);

        if (hci_dev_test_flag(hdev, HCI_SC_ONLY) && !(auth & SMP_AUTH_SC))
                return SMP_AUTH_REQUIREMENTS;

        /* If the remote side's OOB flag is set it means it has
         * successfully received our local OOB data - therefore set the
         * flag to indicate that local OOB is in use.
         */
        if (rsp->oob_flag == SMP_OOB_PRESENT && SMP_DEV(hdev)->local_oob)
                set_bit(SMP_FLAG_LOCAL_OOB, &smp->flags);

        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_CT2) && (auth & SMP_AUTH_CT2))
                set_bit(SMP_FLAG_CT2, &smp->flags);

        /* For BR/EDR this means we're done and can start phase 3 */
        if (conn->hcon->type == ACL_LINK) {
                /* Clear bits which are generated but not distributed */
                smp->remote_key_dist &= ~SMP_SC_NO_DIST;
                smp_distribute_keys(smp);
                return 0;
        }

        if ((req->auth_req & SMP_AUTH_SC) && (auth & SMP_AUTH_SC))
                set_bit(SMP_FLAG_SC, &smp->flags);
        else if (conn->hcon->pending_sec_level > BT_SECURITY_HIGH)
                conn->hcon->pending_sec_level = BT_SECURITY_HIGH;

        /* If we need MITM check that it can be achieved */
        if (conn->hcon->pending_sec_level >= BT_SECURITY_HIGH) {
                u8 method;

                method = get_auth_method(smp, req->io_capability,
                                         rsp->io_capability);
                if (method == JUST_WORKS || method == JUST_CFM)
                        return SMP_AUTH_REQUIREMENTS;
        }

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

        /* 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 (test_bit(SMP_FLAG_SC, &smp->flags)) {

                /* Clear bits which are generated but not distributed */
                smp->remote_key_dist &= ~SMP_SC_NO_DIST;
                SMP_ALLOW_CMD(smp, SMP_CMD_PUBLIC_KEY);
                return sc_send_public_key(smp);
        }

        auth |= req->auth_req;

        ret = tk_request(conn, 0, auth, req->io_capability, rsp->io_capability);
        if (ret)
                return SMP_UNSPECIFIED;

        set_bit(SMP_FLAG_CFM_PENDING, &smp->flags);

        /* Can't compose response until we have been confirmed */
        if (test_bit(SMP_FLAG_TK_VALID, &smp->flags))
                return smp_confirm(smp);

        return 0;
}

static u8 sc_check_confirm(struct smp_chan *smp)
{
        struct l2cap_conn *conn = smp->conn;

        bt_dev_dbg(conn->hcon->hdev, "");

        if (smp->method == REQ_PASSKEY || smp->method == DSP_PASSKEY)
                return sc_passkey_round(smp, SMP_CMD_PAIRING_CONFIRM);

        if (conn->hcon->out) {
                smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(smp->prnd),
                             smp->prnd);
                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_RANDOM);
        }

        return 0;
}

/* Work-around for some implementations that incorrectly copy RFU bits
 * from our security request and thereby create the impression that
 * we're doing SC when in fact the remote doesn't support it.
 */
static int fixup_sc_false_positive(struct smp_chan *smp)
{
        struct l2cap_conn *conn = smp->conn;
        struct hci_conn *hcon = conn->hcon;
        struct hci_dev *hdev = hcon->hdev;
        struct smp_cmd_pairing *req, *rsp;
        u8 auth;

        /* The issue is only observed when we're in responder role */
        if (hcon->out)
                return SMP_UNSPECIFIED;

        if (hci_dev_test_flag(hdev, HCI_SC_ONLY)) {
                bt_dev_err(hdev, "refusing legacy fallback in SC-only mode");
                return SMP_UNSPECIFIED;
        }

        bt_dev_err(hdev, "trying to fall back to legacy SMP");

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

        /* Rebuild key dist flags which may have been cleared for SC */
        smp->remote_key_dist = (req->init_key_dist & rsp->resp_key_dist);

        auth = req->auth_req & AUTH_REQ_MASK(hdev);

        if (tk_request(conn, 0, auth, rsp->io_capability, req->io_capability)) {
                bt_dev_err(hdev, "failed to fall back to legacy SMP");
                return SMP_UNSPECIFIED;
        }

        clear_bit(SMP_FLAG_SC, &smp->flags);

        return 0;
}

static u8 smp_cmd_pairing_confirm(struct l2cap_conn *conn, struct sk_buff *skb)
{
        struct l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;
        struct hci_conn *hcon = conn->hcon;
        struct hci_dev *hdev = hcon->hdev;

        bt_dev_dbg(hdev, "conn %p %s", conn,
                   hcon->out ? "initiator" : "responder");

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

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

        if (test_bit(SMP_FLAG_SC, &smp->flags)) {
                int ret;

                /* Public Key exchange must happen before any other steps */
                if (test_bit(SMP_FLAG_REMOTE_PK, &smp->flags))
                        return sc_check_confirm(smp);

                bt_dev_err(hdev, "Unexpected SMP Pairing Confirm");

                ret = fixup_sc_false_positive(smp);
                if (ret)
                        return ret;
        }

        if (conn->hcon->out) {
                smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(smp->prnd),
                             smp->prnd);
                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_RANDOM);
                return 0;
        }

        if (test_bit(SMP_FLAG_TK_VALID, &smp->flags))
                return smp_confirm(smp);

        set_bit(SMP_FLAG_CFM_PENDING, &smp->flags);

        return 0;
}

static u8 smp_cmd_pairing_random(struct l2cap_conn *conn, struct sk_buff *skb)
{
        struct l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;
        struct hci_conn *hcon = conn->hcon;
        u8 *pkax, *pkbx, *na, *nb, confirm_hint;
        u32 passkey;
        int err;

        bt_dev_dbg(hcon->hdev, "conn %p", conn);

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

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

        if (!test_bit(SMP_FLAG_SC, &smp->flags))
                return smp_random(smp);

        if (hcon->out) {
                pkax = smp->local_pk;
                pkbx = smp->remote_pk;
                na   = smp->prnd;
                nb   = smp->rrnd;
        } else {
                pkax = smp->remote_pk;
                pkbx = smp->local_pk;
                na   = smp->rrnd;
                nb   = smp->prnd;
        }

        if (smp->method == REQ_OOB) {
                if (!hcon->out)
                        smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM,
                                     sizeof(smp->prnd), smp->prnd);
                SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
                goto mackey_and_ltk;
        }

        /* Passkey entry has special treatment */
        if (smp->method == REQ_PASSKEY || smp->method == DSP_PASSKEY)
                return sc_passkey_round(smp, SMP_CMD_PAIRING_RANDOM);

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

                err = smp_f4(smp->tfm_cmac, smp->remote_pk, smp->local_pk,
                             smp->rrnd, 0, cfm);
                if (err)
                        return SMP_UNSPECIFIED;

                if (crypto_memneq(smp->pcnf, cfm, 16))
                        return SMP_CONFIRM_FAILED;
        } else {
                smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM, sizeof(smp->prnd),
                             smp->prnd);
                SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);

                /* Only Just-Works pairing requires extra checks */
                if (smp->method != JUST_WORKS)
                        goto mackey_and_ltk;

                /* If there already exists long term key in local host, leave
                 * the decision to user space since the remote device could
                 * be legitimate or malicious.
                 */
                if (hci_find_ltk(hcon->hdev, &hcon->dst, hcon->dst_type,
                                 hcon->role)) {
                        /* Set passkey to 0. The value can be any number since
                         * it'll be ignored anyway.
                         */
                        passkey = 0;
                        confirm_hint = 1;
                        goto confirm;
                }
        }

mackey_and_ltk:
        /* Generate MacKey and LTK */
        err = sc_mackey_and_ltk(smp, smp->mackey, smp->tk);
        if (err)
                return SMP_UNSPECIFIED;

        if (smp->method == REQ_OOB) {
                if (hcon->out) {
                        sc_dhkey_check(smp);
                        SMP_ALLOW_CMD(smp, SMP_CMD_DHKEY_CHECK);
                }
                return 0;
        }

        err = smp_g2(smp->tfm_cmac, pkax, pkbx, na, nb, &passkey);
        if (err)
                return SMP_UNSPECIFIED;

        confirm_hint = 0;

confirm:
        if (smp->method == JUST_WORKS)
                confirm_hint = 1;

        err = mgmt_user_confirm_request(hcon->hdev, &hcon->dst, hcon->type,
                                        hcon->dst_type, passkey, confirm_hint);
        if (err)
                return SMP_UNSPECIFIED;

        set_bit(SMP_FLAG_WAIT_USER, &smp->flags);

        return 0;
}

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

        key = hci_find_ltk(hcon->hdev, &hcon->dst, hcon->dst_type, hcon->role);
        if (!key)
                return false;

        if (smp_ltk_sec_level(key) < sec_level)
                return false;

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

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

        /* We never store STKs for initiator role, so clear this flag */
        clear_bit(HCI_CONN_STK_ENCRYPT, &hcon->flags);

        return true;
}

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

        /* If we're encrypted with an STK but the caller prefers using
         * LTK claim insufficient security. This way we allow the
         * connection to be re-encrypted with an LTK, even if the LTK
         * provides the same level of security. Only exception is if we
         * don't have an LTK (e.g. because of key distribution bits).
         */
        if (key_pref == SMP_USE_LTK &&
            test_bit(HCI_CONN_STK_ENCRYPT, &hcon->flags) &&
            hci_find_ltk(hcon->hdev, &hcon->dst, hcon->dst_type, hcon->role))
                return false;

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

        return false;
}

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 hci_dev *hdev = hcon->hdev;
        struct smp_chan *smp;
        u8 sec_level, auth;

        bt_dev_dbg(hdev, "conn %p", conn);

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

        if (hcon->role != HCI_ROLE_MASTER)
                return SMP_CMD_NOTSUPP;

        auth = rp->auth_req & AUTH_REQ_MASK(hdev);

        if (hci_dev_test_flag(hdev, HCI_SC_ONLY) && !(auth & SMP_AUTH_SC))
                return SMP_AUTH_REQUIREMENTS;

        if (hcon->io_capability == HCI_IO_NO_INPUT_OUTPUT)
                sec_level = BT_SECURITY_MEDIUM;
        else
                sec_level = authreq_to_seclevel(auth);

        if (smp_sufficient_security(hcon, sec_level, SMP_USE_LTK)) {
                /* If link is already encrypted with sufficient security we
                 * still need refresh encryption as per Core Spec 5.0 Vol 3,
                 * Part H 2.4.6
                 */
                smp_ltk_encrypt(conn, hcon->sec_level);
                return 0;
        }

        if (sec_level > hcon->pending_sec_level)
                hcon->pending_sec_level = sec_level;

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

        smp = smp_chan_create(conn);
        if (!smp)
                return SMP_UNSPECIFIED;

        if (!hci_dev_test_flag(hdev, HCI_BONDABLE) &&
            (auth & SMP_AUTH_BONDING))
                return SMP_PAIRING_NOTSUPP;

        skb_pull(skb, sizeof(*rp));

        memset(&cp, 0, sizeof(cp));
        build_pairing_cmd(conn, &cp, NULL, auth);

        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);
        SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_RSP);

        return 0;
}

int smp_conn_security(struct hci_conn *hcon, __u8 sec_level)
{
        struct l2cap_conn *conn = hcon->l2cap_data;
        struct l2cap_chan *chan;
        struct smp_chan *smp;
        __u8 authreq;
        int ret;

        bt_dev_dbg(hcon->hdev, "conn %p hcon %p level 0x%2.2x", conn, hcon,
                   sec_level);

        /* This may be NULL if there's an unexpected disconnection */
        if (!conn)
                return 1;

        if (!hci_dev_test_flag(hcon->hdev, HCI_LE_ENABLED))
                return 1;

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

        if (sec_level > hcon->pending_sec_level)
                hcon->pending_sec_level = sec_level;

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

        chan = conn->smp;
        if (!chan) {
                bt_dev_err(hcon->hdev, "security requested but not available");
                return 1;
        }

        l2cap_chan_lock(chan);

        /* If SMP is already in progress ignore this request */
        if (chan->data) {
                ret = 0;
                goto unlock;
        }

        smp = smp_chan_create(conn);
        if (!smp) {
                ret = 1;
                goto unlock;
        }

        authreq = seclevel_to_authreq(sec_level);

        if (hci_dev_test_flag(hcon->hdev, HCI_SC_ENABLED)) {
                authreq |= SMP_AUTH_SC;
                if (hci_dev_test_flag(hcon->hdev, HCI_SSP_ENABLED))
                        authreq |= SMP_AUTH_CT2;
        }

        /* Don't attempt to set MITM if setting is overridden by debugfs
         * Needed to pass certification test SM/MAS/PKE/BV-01-C
         */
        if (!hci_dev_test_flag(hcon->hdev, HCI_FORCE_NO_MITM)) {
                /* Require MITM if IO Capability allows or the security level
                 * requires it.
                 */
                if (hcon->io_capability != HCI_IO_NO_INPUT_OUTPUT ||
                    hcon->pending_sec_level > BT_SECURITY_MEDIUM)
                        authreq |= SMP_AUTH_MITM;
        }

        if (hcon->role == HCI_ROLE_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);
                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_RSP);
        } else {
                struct smp_cmd_security_req cp;
                cp.auth_req = authreq;
                smp_send_cmd(conn, SMP_CMD_SECURITY_REQ, sizeof(cp), &cp);
                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_REQ);
        }

        set_bit(SMP_FLAG_INITIATOR, &smp->flags);
        ret = 0;

unlock:
        l2cap_chan_unlock(chan);
        return ret;
}

int smp_cancel_and_remove_pairing(struct hci_dev *hdev, bdaddr_t *bdaddr,
                                  u8 addr_type)
{
        struct hci_conn *hcon;
        struct l2cap_conn *conn;
        struct l2cap_chan *chan;
        struct smp_chan *smp;
        int err;

        err = hci_remove_ltk(hdev, bdaddr, addr_type);
        hci_remove_irk(hdev, bdaddr, addr_type);

        hcon = hci_conn_hash_lookup_le(hdev, bdaddr, addr_type);
        if (!hcon)
                goto done;

        conn = hcon->l2cap_data;
        if (!conn)
                goto done;

        chan = conn->smp;
        if (!chan)
                goto done;

        l2cap_chan_lock(chan);

        smp = chan->data;
        if (smp) {
                /* Set keys to NULL to make sure smp_failure() does not try to
                 * remove and free already invalidated rcu list entries. */
                smp->ltk = NULL;
                smp->responder_ltk = NULL;
                smp->remote_irk = NULL;

                if (test_bit(SMP_FLAG_COMPLETE, &smp->flags))
                        smp_failure(conn, 0);
                else
                        smp_failure(conn, SMP_UNSPECIFIED);
                err = 0;
        }

        l2cap_chan_unlock(chan);

done:
        return err;
}

static int smp_cmd_encrypt_info(struct l2cap_conn *conn, struct sk_buff *skb)
{
        struct smp_cmd_encrypt_info *rp = (void *) skb->data;
        struct l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;

        bt_dev_dbg(conn->hcon->hdev, "conn %p", conn);

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

        /* Pairing is aborted if any blocked keys are distributed */
        if (hci_is_blocked_key(conn->hcon->hdev, HCI_BLOCKED_KEY_TYPE_LTK,
                               rp->ltk)) {
                bt_dev_warn_ratelimited(conn->hcon->hdev,
                                        "LTK blocked for %pMR",
                                        &conn->hcon->dst);
                return SMP_INVALID_PARAMS;
        }

        SMP_ALLOW_CMD(smp, SMP_CMD_INITIATOR_IDENT);

        skb_pull(skb, sizeof(*rp));

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

        return 0;
}

static int smp_cmd_initiator_ident(struct l2cap_conn *conn, struct sk_buff *skb)
{
        struct smp_cmd_initiator_ident *rp = (void *)skb->data;
        struct l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;
        struct hci_dev *hdev = conn->hcon->hdev;
        struct hci_conn *hcon = conn->hcon;
        struct smp_ltk *ltk;
        u8 authenticated;

        bt_dev_dbg(hdev, "conn %p", conn);

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

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

        if (smp->remote_key_dist & SMP_DIST_ID_KEY)
                SMP_ALLOW_CMD(smp, SMP_CMD_IDENT_INFO);
        else if (smp->remote_key_dist & SMP_DIST_SIGN)
                SMP_ALLOW_CMD(smp, SMP_CMD_SIGN_INFO);

        skb_pull(skb, sizeof(*rp));

        authenticated = (hcon->sec_level == BT_SECURITY_HIGH);
        ltk = hci_add_ltk(hdev, &hcon->dst, hcon->dst_type, SMP_LTK,
                          authenticated, smp->tk, smp->enc_key_size,
                          rp->ediv, rp->rand);
        smp->ltk = ltk;
        if (!(smp->remote_key_dist & KEY_DIST_MASK))
                smp_distribute_keys(smp);

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

        bt_dev_dbg(conn->hcon->hdev, "");

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

        /* Pairing is aborted if any blocked keys are distributed */
        if (hci_is_blocked_key(conn->hcon->hdev, HCI_BLOCKED_KEY_TYPE_IRK,
                               info->irk)) {
                bt_dev_warn_ratelimited(conn->hcon->hdev,
                                        "Identity key blocked for %pMR",
                                        &conn->hcon->dst);
                return SMP_INVALID_PARAMS;
        }

        SMP_ALLOW_CMD(smp, SMP_CMD_IDENT_ADDR_INFO);

        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 l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;
        struct hci_conn *hcon = conn->hcon;
        bdaddr_t rpa;

        bt_dev_dbg(hcon->hdev, "");

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

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

        if (smp->remote_key_dist & SMP_DIST_SIGN)
                SMP_ALLOW_CMD(smp, SMP_CMD_SIGN_INFO);

        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.
         *
         * The Identity Address must also be a Static Random or Public
         * Address, which hci_is_identity_address() checks for.
         */
        if (!bacmp(&info->bdaddr, BDADDR_ANY) ||
            !hci_is_identity_address(&info->bdaddr, info->addr_type)) {
                bt_dev_err(hcon->hdev, "ignoring IRK with no identity address");
                goto distribute;
        }

        /* Drop IRK if peer is using identity address during pairing but is
         * providing different address as identity information.
         *
         * Microsoft Surface Precision Mouse is known to have this bug.
         */
        if (hci_is_identity_address(&hcon->dst, hcon->dst_type) &&
            (bacmp(&info->bdaddr, &hcon->dst) ||
             info->addr_type != hcon->dst_type)) {
                bt_dev_err(hcon->hdev,
                           "ignoring IRK with invalid identity address");
                goto distribute;
        }

        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);

distribute:
        if (!(smp->remote_key_dist & KEY_DIST_MASK))
                smp_distribute_keys(smp);

        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 l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;
        struct smp_csrk *csrk;

        bt_dev_dbg(conn->hcon->hdev, "conn %p", conn);

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

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

        skb_pull(skb, sizeof(*rp));

        csrk = kzalloc(sizeof(*csrk), GFP_KERNEL);
        if (csrk) {
                if (conn->hcon->sec_level > BT_SECURITY_MEDIUM)
                        csrk->type = MGMT_CSRK_REMOTE_AUTHENTICATED;
                else
                        csrk->type = MGMT_CSRK_REMOTE_UNAUTHENTICATED;
                memcpy(csrk->val, rp->csrk, sizeof(csrk->val));
        }
        smp->csrk = csrk;
        smp_distribute_keys(smp);

        return 0;
}

static u8 sc_select_method(struct smp_chan *smp)
{
        struct l2cap_conn *conn = smp->conn;
        struct hci_conn *hcon = conn->hcon;
        struct smp_cmd_pairing *local, *remote;
        u8 local_mitm, remote_mitm, local_io, remote_io, method;

        if (test_bit(SMP_FLAG_REMOTE_OOB, &smp->flags) ||
            test_bit(SMP_FLAG_LOCAL_OOB, &smp->flags))
                return REQ_OOB;

        /* The preq/prsp contain the raw Pairing Request/Response PDUs
         * which are needed as inputs to some crypto functions. To get
         * the "struct smp_cmd_pairing" from them we need to skip the
         * first byte which contains the opcode.
         */
        if (hcon->out) {
                local = (void *) &smp->preq[1];
                remote = (void *) &smp->prsp[1];
        } else {
                local = (void *) &smp->prsp[1];
                remote = (void *) &smp->preq[1];
        }

        local_io = local->io_capability;
        remote_io = remote->io_capability;

        local_mitm = (local->auth_req & SMP_AUTH_MITM);
        remote_mitm = (remote->auth_req & SMP_AUTH_MITM);

        /* If either side wants MITM, look up the method from the table,
         * otherwise use JUST WORKS.
         */
        if (local_mitm || remote_mitm)
                method = get_auth_method(smp, local_io, remote_io);
        else
                method = JUST_WORKS;

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

        return method;
}

static int smp_cmd_public_key(struct l2cap_conn *conn, struct sk_buff *skb)
{
        struct smp_cmd_public_key *key = (void *) skb->data;
        struct hci_conn *hcon = conn->hcon;
        struct l2cap_chan *chan = conn->smp;
        struct smp_chan *smp = chan->data;
        struct hci_dev *hdev = hcon->hdev;
        struct crypto_kpp *tfm_ecdh;
        struct smp_cmd_pairing_confirm cfm;
        int err;

        bt_dev_dbg(hdev, "conn %p", conn);

        if (skb->len < sizeof(*key))
                return SMP_INVALID_PARAMS;

        /* Check if remote and local public keys are the same and debug key is
         * not in use.
         */
        if (!test_bit(SMP_FLAG_DEBUG_KEY, &smp->flags) &&
            !crypto_memneq(key, smp->local_pk, 64)) {
                bt_dev_err(hdev, "Remote and local public keys are identical");
                return SMP_UNSPECIFIED;
        }

        memcpy(smp->remote_pk, key, 64);

        if (test_bit(SMP_FLAG_REMOTE_OOB, &smp->flags)) {
                err = smp_f4(smp->tfm_cmac, smp->remote_pk, smp->remote_pk,
                             smp->rr, 0, cfm.confirm_val);
                if (err)
                        return SMP_UNSPECIFIED;

                if (crypto_memneq(cfm.confirm_val, smp->pcnf, 16))
                        return SMP_CONFIRM_FAILED;
        }

        /* Non-initiating device sends its public key after receiving
         * the key from the initiating device.
         */
        if (!hcon->out) {
                err = sc_send_public_key(smp);
                if (err)
                        return err;
        }

        SMP_DBG("Remote Public Key X: %32phN", smp->remote_pk);
        SMP_DBG("Remote Public Key Y: %32phN", smp->remote_pk + 32);

        /* Compute the shared secret on the same crypto tfm on which the private
         * key was set/generated.
         */
        if (test_bit(SMP_FLAG_LOCAL_OOB, &smp->flags)) {
                struct l2cap_chan *hchan = hdev->smp_data;
                struct smp_dev *smp_dev;

                if (!hchan || !hchan->data)
                        return SMP_UNSPECIFIED;

                smp_dev = hchan->data;

                tfm_ecdh = smp_dev->tfm_ecdh;
        } else {
                tfm_ecdh = smp->tfm_ecdh;
        }

        if (compute_ecdh_secret(tfm_ecdh, smp->remote_pk, smp->dhkey))
                return SMP_UNSPECIFIED;

        SMP_DBG("DHKey %32phN", smp->dhkey);

        set_bit(SMP_FLAG_REMOTE_PK, &smp->flags);

        smp->method = sc_select_method(smp);

        bt_dev_dbg(hdev, "selected method 0x%02x", smp->method);

        /* JUST_WORKS and JUST_CFM result in an unauthenticated key */
        if (smp->method == JUST_WORKS || smp->method == JUST_CFM)
                hcon->pending_sec_level = BT_SECURITY_MEDIUM;
        else
                hcon->pending_sec_level = BT_SECURITY_FIPS;

        if (!crypto_memneq(debug_pk, smp->remote_pk, 64))
                set_bit(SMP_FLAG_DEBUG_KEY, &smp->flags);

        if (smp->method == DSP_PASSKEY) {
                get_random_bytes(&hcon->passkey_notify,
                                 sizeof(hcon->passkey_notify));
                hcon->passkey_notify %= 1000000;
                hcon->passkey_entered = 0;
                smp->passkey_round = 0;
                if (mgmt_user_passkey_notify(hdev, &hcon->dst, hcon->type,
                                             hcon->dst_type,
                                             hcon->passkey_notify,
                                             hcon->passkey_entered))
                        return SMP_UNSPECIFIED;
                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_CONFIRM);
                return sc_passkey_round(smp, SMP_CMD_PUBLIC_KEY);
        }

        if (smp->method == REQ_OOB) {
                if (hcon->out)
                        smp_send_cmd(conn, SMP_CMD_PAIRING_RANDOM,
                                     sizeof(smp->prnd), smp->prnd);

                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_RANDOM);

                return 0;
        }

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

        if (smp->method == REQ_PASSKEY) {
                if (mgmt_user_passkey_request(hdev, &hcon->dst, hcon->type,
                                              hcon->dst_type))
                        return SMP_UNSPECIFIED;
                SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_CONFIRM);
                set_bit(SMP_FLAG_WAIT_USER, &smp->flags);
                return 0;
        }

        /* The Initiating device waits for the non-initiating device to
         * send the confirm value.
         */
        if (conn->hcon->out)
                return 0;

        err = smp_f4(smp->tfm_cmac, smp->local_pk, smp->remote_pk, smp->prnd,
                     0, cfm.confirm_val);
        if (err)
                return SMP_UNSPECIFIED;

        smp_send_cmd(conn, SMP_CMD_PAIRING_CONFIRM, sizeof(cfm), &cfm);
        SMP_ALLOW_CMD(smp, SMP_CMD_PAIRING_RANDOM);

        return 0;
}

static int smp_cmd_dhkey_check(struct l2cap_conn *conn, struct sk_buff *skb)
{
        struct smp_cmd_dhkey_check *check = (void *) skb->data;
        struct l2cap_chan *chan = conn->smp;
        struct hci_conn *hcon = conn->hcon;
        struct smp_chan *smp = chan->data;
        u8 a[7], b[7], *local_addr, *remote_addr;
        u8 io_cap[3], r[16], e[16];
        int err;

        bt_dev_dbg(hcon->hdev, "conn %p", conn);

        if (skb->len < sizeof(*check))
                return SMP_INVALID_PARAMS;

        memcpy(a, &hcon->init_addr, 6);
        memcpy(b, &hcon->resp_addr, 6);
        a[6] = hcon->init_addr_type;
        b[6] = hcon->resp_addr_type;

        if (hcon->out) {
                local_addr = a;
                remote_addr = b;
                memcpy(io_cap, &smp->prsp[1], 3);
        } else {
                local_addr = b;
                remote_addr = a;
                memcpy(io_cap, &smp->preq[1], 3);
        }

        memset(r, 0, sizeof(r));

        if (smp->method == REQ_PASSKEY || smp->method == DSP_PASSKEY)
                put_unaligned_le32(hcon->passkey_notify, r);
        else if (smp->method == REQ_OOB)
                memcpy(r, smp->lr, 16);

        err = smp_f6(smp->tfm_cmac, smp->mackey, smp->rrnd, smp->prnd, r,
                     io_cap, remote_addr, local_addr, e);
        if (err)
                return SMP_UNSPECIFIED;

        if (crypto_memneq(check->e, e, 16))
                return SMP_DHKEY_CHECK_FAILED;

        if (!hcon->out) {
                if (test_bit(SMP_FLAG_WAIT_USER, &smp->flags)) {
                        set_bit(SMP_FLAG_DHKEY_PENDING, &smp->flags);
                        return 0;
                }

                /* Responder sends DHKey check as response to initiator */
                sc_dhkey_check(smp);
        }

        sc_add_ltk(smp);

        if (hcon->out) {
                hci_le_start_enc(hcon, 0, 0, smp->tk, smp->enc_key_size);
                hcon->enc_key_size = smp->enc_key_size;
        }

        return 0;
}

static int smp_cmd_keypress_notify(struct l2cap_conn *conn,
                                   struct sk_buff *skb)
{
        struct smp_cmd_keypress_notify *kp = (void *) skb->data;

        bt_dev_dbg(conn->hcon->hdev, "value 0x%02x", kp->value);

        return 0;
}

static int smp_sig_channel(struct l2cap_chan *chan, struct sk_buff *skb)
{
        struct l2cap_conn *conn = chan->conn;
        struct hci_conn *hcon = conn->hcon;
        struct smp_chan *smp;
        __u8 code, reason;
        int err = 0;

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

        if (!hci_dev_test_flag(hcon->hdev, HCI_LE_ENABLED)) {
                reason = SMP_PAIRING_NOTSUPP;
                goto done;
        }

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

        smp = chan->data;

        if (code > SMP_CMD_MAX)
                goto drop;

        if (smp && !test_and_clear_bit(code, &smp->allow_cmd))
                goto drop;

        /* If we don't have a context the only allowed commands are
         * pairing request and security request.
         */
        if (!smp && code != SMP_CMD_PAIRING_REQ && code != SMP_CMD_SECURITY_REQ)
                goto drop;

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

        case SMP_CMD_PAIRING_FAIL:
                smp_failure(conn, 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;