// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2020 Hannes Reinecke, SUSE Linux
 */

#include <linux/module.h>
#include <linux/crc32.h>
#include <linux/base64.h>
#include <linux/prandom.h>
#include <linux/scatterlist.h>
#include <linux/unaligned.h>
#include <crypto/hash.h>
#include <crypto/dh.h>
#include <crypto/hkdf.h>
#include <linux/nvme.h>
#include <linux/nvme-auth.h>

#define HKDF_MAX_HASHLEN 64

static u32 nvme_dhchap_seqnum;
static DEFINE_MUTEX(nvme_dhchap_mutex);

u32 nvme_auth_get_seqnum(void)
{
        u32 seqnum;

        mutex_lock(&nvme_dhchap_mutex);
        if (!nvme_dhchap_seqnum)
                nvme_dhchap_seqnum = get_random_u32();
        else {
                nvme_dhchap_seqnum++;
                if (!nvme_dhchap_seqnum)
                        nvme_dhchap_seqnum++;
        }
        seqnum = nvme_dhchap_seqnum;
        mutex_unlock(&nvme_dhchap_mutex);
        return seqnum;
}
EXPORT_SYMBOL_GPL(nvme_auth_get_seqnum);

static struct nvme_auth_dhgroup_map {
        const char name[16];
        const char kpp[16];
} dhgroup_map[] = {
        [NVME_AUTH_DHGROUP_NULL] = {
                .name = "null", .kpp = "null" },
        [NVME_AUTH_DHGROUP_2048] = {
                .name = "ffdhe2048", .kpp = "ffdhe2048(dh)" },
        [NVME_AUTH_DHGROUP_3072] = {
                .name = "ffdhe3072", .kpp = "ffdhe3072(dh)" },
        [NVME_AUTH_DHGROUP_4096] = {
                .name = "ffdhe4096", .kpp = "ffdhe4096(dh)" },
        [NVME_AUTH_DHGROUP_6144] = {
                .name = "ffdhe6144", .kpp = "ffdhe6144(dh)" },
        [NVME_AUTH_DHGROUP_8192] = {
                .name = "ffdhe8192", .kpp = "ffdhe8192(dh)" },
};

const char *nvme_auth_dhgroup_name(u8 dhgroup_id)
{
        if (dhgroup_id >= ARRAY_SIZE(dhgroup_map))
                return NULL;
        return dhgroup_map[dhgroup_id].name;
}
EXPORT_SYMBOL_GPL(nvme_auth_dhgroup_name);

const char *nvme_auth_dhgroup_kpp(u8 dhgroup_id)
{
        if (dhgroup_id >= ARRAY_SIZE(dhgroup_map))
                return NULL;
        return dhgroup_map[dhgroup_id].kpp;
}
EXPORT_SYMBOL_GPL(nvme_auth_dhgroup_kpp);

u8 nvme_auth_dhgroup_id(const char *dhgroup_name)
{
        int i;

        if (!dhgroup_name || !strlen(dhgroup_name))
                return NVME_AUTH_DHGROUP_INVALID;
        for (i = 0; i < ARRAY_SIZE(dhgroup_map); i++) {
                if (!strlen(dhgroup_map[i].name))
                        continue;
                if (!strncmp(dhgroup_map[i].name, dhgroup_name,
                             strlen(dhgroup_map[i].name)))
                        return i;
        }
        return NVME_AUTH_DHGROUP_INVALID;
}
EXPORT_SYMBOL_GPL(nvme_auth_dhgroup_id);

static struct nvme_dhchap_hash_map {
        int len;
        const char hmac[15];
        const char digest[8];
} hash_map[] = {
        [NVME_AUTH_HASH_SHA256] = {
                .len = 32,
                .hmac = "hmac(sha256)",
                .digest = "sha256",
        },
        [NVME_AUTH_HASH_SHA384] = {
                .len = 48,
                .hmac = "hmac(sha384)",
                .digest = "sha384",
        },
        [NVME_AUTH_HASH_SHA512] = {
                .len = 64,
                .hmac = "hmac(sha512)",
                .digest = "sha512",
        },
};

const char *nvme_auth_hmac_name(u8 hmac_id)
{
        if (hmac_id >= ARRAY_SIZE(hash_map))
                return NULL;
        return hash_map[hmac_id].hmac;
}
EXPORT_SYMBOL_GPL(nvme_auth_hmac_name);

const char *nvme_auth_digest_name(u8 hmac_id)
{
        if (hmac_id >= ARRAY_SIZE(hash_map))
                return NULL;
        return hash_map[hmac_id].digest;
}
EXPORT_SYMBOL_GPL(nvme_auth_digest_name);

u8 nvme_auth_hmac_id(const char *hmac_name)
{
        int i;

        if (!hmac_name || !strlen(hmac_name))
                return NVME_AUTH_HASH_INVALID;

        for (i = 0; i < ARRAY_SIZE(hash_map); i++) {
                if (!strlen(hash_map[i].hmac))
                        continue;
                if (!strncmp(hash_map[i].hmac, hmac_name,
                             strlen(hash_map[i].hmac)))
                        return i;
        }
        return NVME_AUTH_HASH_INVALID;
}
EXPORT_SYMBOL_GPL(nvme_auth_hmac_id);

size_t nvme_auth_hmac_hash_len(u8 hmac_id)
{
        if (hmac_id >= ARRAY_SIZE(hash_map))
                return 0;
        return hash_map[hmac_id].len;
}
EXPORT_SYMBOL_GPL(nvme_auth_hmac_hash_len);

u32 nvme_auth_key_struct_size(u32 key_len)
{
        struct nvme_dhchap_key key;

        return struct_size(&key, key, key_len);
}
EXPORT_SYMBOL_GPL(nvme_auth_key_struct_size);

struct nvme_dhchap_key *nvme_auth_extract_key(unsigned char *secret,
                                              u8 key_hash)
{
        struct nvme_dhchap_key *key;
        unsigned char *p;
        u32 crc;
        int ret, key_len;
        size_t allocated_len = strlen(secret);

        /* Secret might be affixed with a ':' */
        p = strrchr(secret, ':');
        if (p)
                allocated_len = p - secret;
        key = nvme_auth_alloc_key(allocated_len, 0);
        if (!key)
                return ERR_PTR(-ENOMEM);

        key_len = base64_decode(secret, allocated_len, key->key, true, BASE64_STD);
        if (key_len < 0) {
                pr_debug("base64 key decoding error %d\n",
                         key_len);
                ret = key_len;
                goto out_free_secret;
        }

        if (key_len != 36 && key_len != 52 &&
            key_len != 68) {
                pr_err("Invalid key len %d\n", key_len);
                ret = -EINVAL;
                goto out_free_secret;
        }

        /* The last four bytes is the CRC in little-endian format */
        key_len -= 4;
        /*
         * The linux implementation doesn't do pre- and post-increments,
         * so we have to do it manually.
         */
        crc = ~crc32(~0, key->key, key_len);

        if (get_unaligned_le32(key->key + key_len) != crc) {
                pr_err("key crc mismatch (key %08x, crc %08x)\n",
                       get_unaligned_le32(key->key + key_len), crc);
                ret = -EKEYREJECTED;
                goto out_free_secret;
        }
        key->len = key_len;
        key->hash = key_hash;
        return key;
out_free_secret:
        nvme_auth_free_key(key);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(nvme_auth_extract_key);

struct nvme_dhchap_key *nvme_auth_alloc_key(u32 len, u8 hash)
{
        u32 num_bytes = nvme_auth_key_struct_size(len);
        struct nvme_dhchap_key *key = kzalloc(num_bytes, GFP_KERNEL);

        if (key) {
                key->len = len;
                key->hash = hash;
        }
        return key;
}
EXPORT_SYMBOL_GPL(nvme_auth_alloc_key);

void nvme_auth_free_key(struct nvme_dhchap_key *key)
{
        if (!key)
                return;
        kfree_sensitive(key);
}
EXPORT_SYMBOL_GPL(nvme_auth_free_key);

struct nvme_dhchap_key *nvme_auth_transform_key(
                struct nvme_dhchap_key *key, char *nqn)
{
        const char *hmac_name;
        struct crypto_shash *key_tfm;
        SHASH_DESC_ON_STACK(shash, key_tfm);
        struct nvme_dhchap_key *transformed_key;
        int ret, key_len;

        if (!key) {
                pr_warn("No key specified\n");
                return ERR_PTR(-ENOKEY);
        }
        if (key->hash == 0) {
                key_len = nvme_auth_key_struct_size(key->len);
                transformed_key = kmemdup(key, key_len, GFP_KERNEL);
                if (!transformed_key)
                        return ERR_PTR(-ENOMEM);
                return transformed_key;
        }
        hmac_name = nvme_auth_hmac_name(key->hash);
        if (!hmac_name) {
                pr_warn("Invalid key hash id %d\n", key->hash);
                return ERR_PTR(-EINVAL);
        }

        key_tfm = crypto_alloc_shash(hmac_name, 0, 0);
        if (IS_ERR(key_tfm))
                return ERR_CAST(key_tfm);

        key_len = crypto_shash_digestsize(key_tfm);
        transformed_key = nvme_auth_alloc_key(key_len, key->hash);
        if (!transformed_key) {
                ret = -ENOMEM;
                goto out_free_key;
        }

        shash->tfm = key_tfm;
        ret = crypto_shash_setkey(key_tfm, key->key, key->len);
        if (ret < 0)
                goto out_free_transformed_key;
        ret = crypto_shash_init(shash);
        if (ret < 0)
                goto out_free_transformed_key;
        ret = crypto_shash_update(shash, nqn, strlen(nqn));
        if (ret < 0)
                goto out_free_transformed_key;
        ret = crypto_shash_update(shash, "NVMe-over-Fabrics", 17);
        if (ret < 0)
                goto out_free_transformed_key;
        ret = crypto_shash_final(shash, transformed_key->key);
        if (ret < 0)
                goto out_free_transformed_key;

        crypto_free_shash(key_tfm);

        return transformed_key;

out_free_transformed_key:
        nvme_auth_free_key(transformed_key);
out_free_key:
        crypto_free_shash(key_tfm);

        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(nvme_auth_transform_key);

static int nvme_auth_hash_skey(int hmac_id, u8 *skey, size_t skey_len, u8 *hkey)
{
        const char *digest_name;
        struct crypto_shash *tfm;
        int ret;

        digest_name = nvme_auth_digest_name(hmac_id);
        if (!digest_name) {
                pr_debug("%s: failed to get digest for %d\n", __func__,
                         hmac_id);
                return -EINVAL;
        }
        tfm = crypto_alloc_shash(digest_name, 0, 0);
        if (IS_ERR(tfm))
                return -ENOMEM;

        ret = crypto_shash_tfm_digest(tfm, skey, skey_len, hkey);
        if (ret < 0)
                pr_debug("%s: Failed to hash digest len %zu\n", __func__,
                         skey_len);

        crypto_free_shash(tfm);
        return ret;
}

int nvme_auth_augmented_challenge(u8 hmac_id, u8 *skey, size_t skey_len,
                u8 *challenge, u8 *aug, size_t hlen)
{
        struct crypto_shash *tfm;
        u8 *hashed_key;
        const char *hmac_name;
        int ret;

        hashed_key = kmalloc(hlen, GFP_KERNEL);
        if (!hashed_key)
                return -ENOMEM;

        ret = nvme_auth_hash_skey(hmac_id, skey,
                                  skey_len, hashed_key);
        if (ret < 0)
                goto out_free_key;

        hmac_name = nvme_auth_hmac_name(hmac_id);
        if (!hmac_name) {
                pr_warn("%s: invalid hash algorithm %d\n",
                        __func__, hmac_id);
                ret = -EINVAL;
                goto out_free_key;
        }

        tfm = crypto_alloc_shash(hmac_name, 0, 0);
        if (IS_ERR(tfm)) {
                ret = PTR_ERR(tfm);
                goto out_free_key;
        }

        ret = crypto_shash_setkey(tfm, hashed_key, hlen);
        if (ret)
                goto out_free_hash;

        ret = crypto_shash_tfm_digest(tfm, challenge, hlen, aug);
out_free_hash:
        crypto_free_shash(tfm);
out_free_key:
        kfree_sensitive(hashed_key);
        return ret;
}
EXPORT_SYMBOL_GPL(nvme_auth_augmented_challenge);

int nvme_auth_gen_privkey(struct crypto_kpp *dh_tfm, u8 dh_gid)
{
        int ret;

        ret = crypto_kpp_set_secret(dh_tfm, NULL, 0);
        if (ret)
                pr_debug("failed to set private key, error %d\n", ret);

        return ret;
}
EXPORT_SYMBOL_GPL(nvme_auth_gen_privkey);

int nvme_auth_gen_pubkey(struct crypto_kpp *dh_tfm,
                u8 *host_key, size_t host_key_len)
{
        struct kpp_request *req;
        struct crypto_wait wait;
        struct scatterlist dst;
        int ret;

        req = kpp_request_alloc(dh_tfm, GFP_KERNEL);
        if (!req)
                return -ENOMEM;

        crypto_init_wait(&wait);
        kpp_request_set_input(req, NULL, 0);
        sg_init_one(&dst, host_key, host_key_len);
        kpp_request_set_output(req, &dst, host_key_len);
        kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
                                 crypto_req_done, &wait);

        ret = crypto_wait_req(crypto_kpp_generate_public_key(req), &wait);
        kpp_request_free(req);
        return ret;
}
EXPORT_SYMBOL_GPL(nvme_auth_gen_pubkey);

int nvme_auth_gen_shared_secret(struct crypto_kpp *dh_tfm,
                u8 *ctrl_key, size_t ctrl_key_len,
                u8 *sess_key, size_t sess_key_len)
{
        struct kpp_request *req;
        struct crypto_wait wait;
        struct scatterlist src, dst;
        int ret;

        req = kpp_request_alloc(dh_tfm, GFP_KERNEL);
        if (!req)
                return -ENOMEM;

        crypto_init_wait(&wait);
        sg_init_one(&src, ctrl_key, ctrl_key_len);
        kpp_request_set_input(req, &src, ctrl_key_len);
        sg_init_one(&dst, sess_key, sess_key_len);
        kpp_request_set_output(req, &dst, sess_key_len);
        kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
                                 crypto_req_done, &wait);

        ret = crypto_wait_req(crypto_kpp_compute_shared_secret(req), &wait);

        kpp_request_free(req);
        return ret;
}
EXPORT_SYMBOL_GPL(nvme_auth_gen_shared_secret);

int nvme_auth_generate_key(u8 *secret, struct nvme_dhchap_key **ret_key)
{
        struct nvme_dhchap_key *key;
        u8 key_hash;

        if (!secret) {
                *ret_key = NULL;
                return 0;
        }

        if (sscanf(secret, "DHHC-1:%hhd:%*s:", &key_hash) != 1)
                return -EINVAL;

        /* Pass in the secret without the 'DHHC-1:XX:' prefix */
        key = nvme_auth_extract_key(secret + 10, key_hash);
        if (IS_ERR(key)) {
                *ret_key = NULL;
                return PTR_ERR(key);
        }

        *ret_key = key;
        return 0;
}
EXPORT_SYMBOL_GPL(nvme_auth_generate_key);

/**
 * nvme_auth_generate_psk - Generate a PSK for TLS
 * @hmac_id: Hash function identifier
 * @skey: Session key
 * @skey_len: Length of @skey
 * @c1: Value of challenge C1
 * @c2: Value of challenge C2
 * @hash_len: Hash length of the hash algorithm
 * @ret_psk: Pointer to the resulting generated PSK
 * @ret_len: length of @ret_psk
 *
 * Generate a PSK for TLS as specified in NVMe base specification, section
 * 8.13.5.9: Generated PSK for TLS
 *
 * The generated PSK for TLS shall be computed applying the HMAC function
 * using the hash function H( ) selected by the HashID parameter in the
 * DH-HMAC-CHAP_Challenge message with the session key KS as key to the
 * concatenation of the two challenges C1 and C2 (i.e., generated
 * PSK = HMAC(KS, C1 || C2)).
 *
 * Returns 0 on success with a valid generated PSK pointer in @ret_psk and
 * the length of @ret_psk in @ret_len, or a negative error number otherwise.
 */
int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
                u8 *c1, u8 *c2, size_t hash_len, u8 **ret_psk, size_t *ret_len)
{
        struct crypto_shash *tfm;
        SHASH_DESC_ON_STACK(shash, tfm);
        u8 *psk;
        const char *hmac_name;
        int ret, psk_len;

        if (!c1 || !c2)
                return -EINVAL;

        hmac_name = nvme_auth_hmac_name(hmac_id);
        if (!hmac_name) {
                pr_warn("%s: invalid hash algorithm %d\n",
                        __func__, hmac_id);
                return -EINVAL;
        }

        tfm = crypto_alloc_shash(hmac_name, 0, 0);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        psk_len = crypto_shash_digestsize(tfm);
        psk = kzalloc(psk_len, GFP_KERNEL);
        if (!psk) {
                ret = -ENOMEM;
                goto out_free_tfm;
        }

        shash->tfm = tfm;
        ret = crypto_shash_setkey(tfm, skey, skey_len);
        if (ret)
                goto out_free_psk;

        ret = crypto_shash_init(shash);
        if (ret)
                goto out_free_psk;

        ret = crypto_shash_update(shash, c1, hash_len);
        if (ret)
                goto out_free_psk;

        ret = crypto_shash_update(shash, c2, hash_len);
        if (ret)
                goto out_free_psk;

        ret = crypto_shash_final(shash, psk);
        if (!ret) {
                *ret_psk = psk;
                *ret_len = psk_len;
        }

out_free_psk:
        if (ret)
                kfree_sensitive(psk);
out_free_tfm:
        crypto_free_shash(tfm);

        return ret;
}
EXPORT_SYMBOL_GPL(nvme_auth_generate_psk);

/**
 * nvme_auth_generate_digest - Generate TLS PSK digest
 * @hmac_id: Hash function identifier
 * @psk: Generated input PSK
 * @psk_len: Length of @psk
 * @subsysnqn: NQN of the subsystem
 * @hostnqn: NQN of the host
 * @ret_digest: Pointer to the returned digest
 *
 * Generate a TLS PSK digest as specified in TP8018 Section 3.6.1.3:
 *   TLS PSK and PSK identity Derivation
 *
 * The PSK digest shall be computed by encoding in Base64 (refer to RFC
 * 4648) the result of the application of the HMAC function using the hash
 * function specified in item 4 above (ie the hash function of the cipher
 * suite associated with the PSK identity) with the PSK as HMAC key to the
 * concatenation of:
 * - the NQN of the host (i.e., NQNh) not including the null terminator;
 * - a space character;
 * - the NQN of the NVM subsystem (i.e., NQNc) not including the null
 *   terminator;
 * - a space character; and
 * - the seventeen ASCII characters "NVMe-over-Fabrics"
 * (i.e., <PSK digest> = Base64(HMAC(PSK, NQNh || " " || NQNc || " " ||
 *  "NVMe-over-Fabrics"))).
 * The length of the PSK digest depends on the hash function used to compute
 * it as follows:
 * - If the SHA-256 hash function is used, the resulting PSK digest is 44
 *   characters long; or
 * - If the SHA-384 hash function is used, the resulting PSK digest is 64
 *   characters long.
 *
 * Returns 0 on success with a valid digest pointer in @ret_digest, or a
 * negative error number on failure.
 */
int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
                char *subsysnqn, char *hostnqn, u8 **ret_digest)
{
        struct crypto_shash *tfm;
        SHASH_DESC_ON_STACK(shash, tfm);
        u8 *digest, *enc;
        const char *hmac_name;
        size_t digest_len, hmac_len;
        int ret;

        if (WARN_ON(!subsysnqn || !hostnqn))
                return -EINVAL;

        hmac_name = nvme_auth_hmac_name(hmac_id);
        if (!hmac_name) {
                pr_warn("%s: invalid hash algorithm %d\n",
                        __func__, hmac_id);
                return -EINVAL;
        }

        switch (nvme_auth_hmac_hash_len(hmac_id)) {
        case 32:
                hmac_len = 44;
                break;
        case 48:
                hmac_len = 64;
                break;
        default:
                pr_warn("%s: invalid hash algorithm '%s'\n",
                        __func__, hmac_name);
                return -EINVAL;
        }

        enc = kzalloc(hmac_len + 1, GFP_KERNEL);
        if (!enc)
                return -ENOMEM;

        tfm = crypto_alloc_shash(hmac_name, 0, 0);
        if (IS_ERR(tfm)) {
                ret = PTR_ERR(tfm);
                goto out_free_enc;
        }

        digest_len = crypto_shash_digestsize(tfm);
        digest = kzalloc(digest_len, GFP_KERNEL);
        if (!digest) {
                ret = -ENOMEM;
                goto out_free_tfm;
        }

        shash->tfm = tfm;
        ret = crypto_shash_setkey(tfm, psk, psk_len);
        if (ret)
                goto out_free_digest;

        ret = crypto_shash_init(shash);
        if (ret)
                goto out_free_digest;

        ret = crypto_shash_update(shash, hostnqn, strlen(hostnqn));
        if (ret)
                goto out_free_digest;

        ret = crypto_shash_update(shash, " ", 1);
        if (ret)
                goto out_free_digest;

        ret = crypto_shash_update(shash, subsysnqn, strlen(subsysnqn));
        if (ret)
                goto out_free_digest;

        ret = crypto_shash_update(shash, " NVMe-over-Fabrics", 18);
        if (ret)
                goto out_free_digest;

        ret = crypto_shash_final(shash, digest);
        if (ret)
                goto out_free_digest;

        ret = base64_encode(digest, digest_len, enc, true, BASE64_STD);
        if (ret < hmac_len) {
                ret = -ENOKEY;
                goto out_free_digest;
        }
        *ret_digest = enc;
        ret = 0;

out_free_digest:
        kfree_sensitive(digest);
out_free_tfm:
        crypto_free_shash(tfm);
out_free_enc:
        if (ret)
                kfree_sensitive(enc);

        return ret;
}
EXPORT_SYMBOL_GPL(nvme_auth_generate_digest);

/**
 * hkdf_expand_label - HKDF-Expand-Label (RFC 8846 section 7.1)
 * @hmac_tfm: hash context keyed with pseudorandom key
 * @label: ASCII label without "tls13 " prefix
 * @labellen: length of @label
 * @context: context bytes
 * @contextlen: length of @context
 * @okm: output keying material
 * @okmlen: length of @okm
 *
 * Build the TLS 1.3 HkdfLabel structure and invoke hkdf_expand().
 *
 * Returns 0 on success with output keying material stored in @okm,
 * or a negative errno value otherwise.
 */
static int hkdf_expand_label(struct crypto_shash *hmac_tfm,
                const u8 *label, unsigned int labellen,
                const u8 *context, unsigned int contextlen,
                u8 *okm, unsigned int okmlen)
{
        int err;
        u8 *info;
        unsigned int infolen;
        const char *tls13_prefix = "tls13 ";
        unsigned int prefixlen = strlen(tls13_prefix);

        if (WARN_ON(labellen > (255 - prefixlen)))
                return -EINVAL;
        if (WARN_ON(contextlen > 255))
                return -EINVAL;

        infolen = 2 + (1 + prefixlen + labellen) + (1 + contextlen);
        info = kzalloc(infolen, GFP_KERNEL);
        if (!info)
                return -ENOMEM;

        /* HkdfLabel.Length */
        put_unaligned_be16(okmlen, info);

        /* HkdfLabel.Label */
        info[2] = prefixlen + labellen;
        memcpy(info + 3, tls13_prefix, prefixlen);
        memcpy(info + 3 + prefixlen, label, labellen);

        /* HkdfLabel.Context */
        info[3 + prefixlen + labellen] = contextlen;
        memcpy(info + 4 + prefixlen + labellen, context, contextlen);

        err = hkdf_expand(hmac_tfm, info, infolen, okm, okmlen);
        kfree_sensitive(info);
        return err;
}

/**
 * nvme_auth_derive_tls_psk - Derive TLS PSK
 * @hmac_id: Hash function identifier
 * @psk: generated input PSK
 * @psk_len: size of @psk
 * @psk_digest: TLS PSK digest
 * @ret_psk: Pointer to the resulting TLS PSK
 *
 * Derive a TLS PSK as specified in TP8018 Section 3.6.1.3:
 *   TLS PSK and PSK identity Derivation
 *
 * The TLS PSK shall be derived as follows from an input PSK
 * (i.e., either a retained PSK or a generated PSK) and a PSK
 * identity using the HKDF-Extract and HKDF-Expand-Label operations
 * (refer to RFC 5869 and RFC 8446) where the hash function is the
 * one specified by the hash specifier of the PSK identity:
 * 1. PRK = HKDF-Extract(0, Input PSK); and
 * 2. TLS PSK = HKDF-Expand-Label(PRK, "nvme-tls-psk", PskIdentityContext, L),
 * where PskIdentityContext is the hash identifier indicated in
 * the PSK identity concatenated to a space character and to the
 * Base64 PSK digest (i.e., "<hash> <PSK digest>") and L is the
 * output size in bytes of the hash function (i.e., 32 for SHA-256
 * and 48 for SHA-384).
 *
 * Returns 0 on success with a valid psk pointer in @ret_psk or a negative
 * error number otherwise.
 */
int nvme_auth_derive_tls_psk(int hmac_id, u8 *psk, size_t psk_len,
                u8 *psk_digest, u8 **ret_psk)
{
        struct crypto_shash *hmac_tfm;
        const char *hmac_name;
        const char *label = "nvme-tls-psk";
        static const char default_salt[HKDF_MAX_HASHLEN];
        size_t prk_len;
        const char *ctx;
        unsigned char *prk, *tls_key;
        int ret;

        hmac_name = nvme_auth_hmac_name(hmac_id);
        if (!hmac_name) {
                pr_warn("%s: invalid hash algorithm %d\n",
                        __func__, hmac_id);
                return -EINVAL;
        }
        if (hmac_id == NVME_AUTH_HASH_SHA512) {
                pr_warn("%s: unsupported hash algorithm %s\n",
                        __func__, hmac_name);
                return -EINVAL;
        }

        hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
        if (IS_ERR(hmac_tfm))
                return PTR_ERR(hmac_tfm);

        prk_len = crypto_shash_digestsize(hmac_tfm);
        prk = kzalloc(prk_len, GFP_KERNEL);
        if (!prk) {
                ret = -ENOMEM;
                goto out_free_shash;
        }

        if (WARN_ON(prk_len > HKDF_MAX_HASHLEN)) {
                ret = -EINVAL;
                goto out_free_prk;
        }
        ret = hkdf_extract(hmac_tfm, psk, psk_len,
                           default_salt, prk_len, prk);
        if (ret)
                goto out_free_prk;

        ret = crypto_shash_setkey(hmac_tfm, prk, prk_len);
        if (ret)
                goto out_free_prk;

        ctx = kasprintf(GFP_KERNEL, "%02d %s", hmac_id, psk_digest);
        if (!ctx) {
                ret = -ENOMEM;
                goto out_free_prk;
        }

        tls_key = kzalloc(psk_len, GFP_KERNEL);
        if (!tls_key) {
                ret = -ENOMEM;
                goto out_free_ctx;
        }
        ret = hkdf_expand_label(hmac_tfm,
                                label, strlen(label),
                                ctx, strlen(ctx),
                                tls_key, psk_len);
        if (ret) {
                kfree(tls_key);
                goto out_free_ctx;
        }
        *ret_psk = tls_key;

out_free_ctx:
        kfree(ctx);
out_free_prk:
        kfree(prk);
out_free_shash:
        crypto_free_shash(hmac_tfm);

        return ret;
}
EXPORT_SYMBOL_GPL(nvme_auth_derive_tls_psk);

MODULE_DESCRIPTION("NVMe Authentication framework");
MODULE_LICENSE("GPL v2");