// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) 2016, Intel Corporation
 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
 */
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/err.h>
#include <linux/string.h>
#include <crypto/ecdh.h>
#include <crypto/kpp.h>

#define ECDH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + sizeof(short))

static inline u8 *ecdh_pack_data(void *dst, const void *src, size_t sz)
{
        memcpy(dst, src, sz);
        return dst + sz;
}

static inline const u8 *ecdh_unpack_data(void *dst, const void *src, size_t sz)
{
        memcpy(dst, src, sz);
        return src + sz;
}

unsigned int crypto_ecdh_key_len(const struct ecdh *params)
{
        return ECDH_KPP_SECRET_MIN_SIZE + params->key_size;
}
EXPORT_SYMBOL_GPL(crypto_ecdh_key_len);

int crypto_ecdh_encode_key(char *buf, unsigned int len,
                           const struct ecdh *params)
{
        u8 *ptr = buf;
        struct kpp_secret secret = {
                .type = CRYPTO_KPP_SECRET_TYPE_ECDH,
                .len = len
        };

        if (unlikely(!buf))
                return -EINVAL;

        if (len != crypto_ecdh_key_len(params))
                return -EINVAL;

        ptr = ecdh_pack_data(ptr, &secret, sizeof(secret));
        ptr = ecdh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
        ecdh_pack_data(ptr, params->key, params->key_size);

        return 0;
}
EXPORT_SYMBOL_GPL(crypto_ecdh_encode_key);

int crypto_ecdh_decode_key(const char *buf, unsigned int len,
                           struct ecdh *params)
{
        const u8 *ptr = buf;
        struct kpp_secret secret;

        if (unlikely(!buf || len < ECDH_KPP_SECRET_MIN_SIZE))
                return -EINVAL;

        ptr = ecdh_unpack_data(&secret, ptr, sizeof(secret));
        if (secret.type != CRYPTO_KPP_SECRET_TYPE_ECDH)
                return -EINVAL;

        if (unlikely(len < secret.len))
                return -EINVAL;

        ptr = ecdh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
        if (secret.len != crypto_ecdh_key_len(params))
                return -EINVAL;

        /* Don't allocate memory. Set pointer to data
         * within the given buffer
         */
        params->key = (void *)ptr;

        return 0;
}
EXPORT_SYMBOL_GPL(crypto_ecdh_decode_key);