// 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/dh.h>
#include <crypto/kpp.h>

#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))

static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
{
        if (!dst || size > end - dst)
                return NULL;
        memcpy(dst, src, size);
        return dst + size;
}

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

static inline unsigned int dh_data_size(const struct dh *p)
{
        return p->key_size + p->p_size + p->g_size;
}

unsigned int crypto_dh_key_len(const struct dh *p)
{
        return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
}
EXPORT_SYMBOL_GPL(crypto_dh_key_len);

int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
{
        u8 *ptr = buf;
        u8 * const end = ptr + len;
        struct kpp_secret secret = {
                .type = CRYPTO_KPP_SECRET_TYPE_DH,
                .len = len
        };

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

        ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
        ptr = dh_pack_data(ptr, end, &params->key_size,
                           sizeof(params->key_size));
        ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
        ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
        ptr = dh_pack_data(ptr, end, params->key, params->key_size);
        ptr = dh_pack_data(ptr, end, params->p, params->p_size);
        ptr = dh_pack_data(ptr, end, params->g, params->g_size);
        if (ptr != end)
                return -EINVAL;
        return 0;
}
EXPORT_SYMBOL_GPL(crypto_dh_encode_key);

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

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

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

        ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
        ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
        ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
        if (secret.len != crypto_dh_key_len(params))
                return -EINVAL;

        /* Don't allocate memory. Set pointers to data within
         * the given buffer
         */
        params->key = (void *)ptr;
        params->p = (void *)(ptr + params->key_size);
        params->g = (void *)(ptr + params->key_size + params->p_size);

        return 0;
}

int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
{
        int err;

        err = __crypto_dh_decode_key(buf, len, params);
        if (err)
                return err;

        /*
         * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
         * some drivers assume otherwise.
         */
        if (params->key_size > params->p_size ||
            params->g_size > params->p_size)
                return -EINVAL;

        /*
         * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
         * to corner cases such as 'mod 0' being undefined or
         * crypto_kpp_maxsize() returning 0.
         */
        if (memchr_inv(params->p, 0, params->p_size) == NULL)
                return -EINVAL;

        return 0;
}
EXPORT_SYMBOL_GPL(crypto_dh_decode_key);