linux/crypto/ecdh_helper.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Copyright (c) 2016, Intel Corporation
   4 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
   5 */
   6#include <linux/kernel.h>
   7#include <linux/export.h>
   8#include <linux/err.h>
   9#include <linux/string.h>
  10#include <crypto/ecdh.h>
  11#include <crypto/kpp.h>
  12
  13#define ECDH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + sizeof(short))
  14
  15static inline u8 *ecdh_pack_data(void *dst, const void *src, size_t sz)
  16{
  17        memcpy(dst, src, sz);
  18        return dst + sz;
  19}
  20
  21static inline const u8 *ecdh_unpack_data(void *dst, const void *src, size_t sz)
  22{
  23        memcpy(dst, src, sz);
  24        return src + sz;
  25}
  26
  27unsigned int crypto_ecdh_key_len(const struct ecdh *params)
  28{
  29        return ECDH_KPP_SECRET_MIN_SIZE + params->key_size;
  30}
  31EXPORT_SYMBOL_GPL(crypto_ecdh_key_len);
  32
  33int crypto_ecdh_encode_key(char *buf, unsigned int len,
  34                           const struct ecdh *params)
  35{
  36        u8 *ptr = buf;
  37        struct kpp_secret secret = {
  38                .type = CRYPTO_KPP_SECRET_TYPE_ECDH,
  39                .len = len
  40        };
  41
  42        if (unlikely(!buf))
  43                return -EINVAL;
  44
  45        if (len != crypto_ecdh_key_len(params))
  46                return -EINVAL;
  47
  48        ptr = ecdh_pack_data(ptr, &secret, sizeof(secret));
  49        ptr = ecdh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
  50        ecdh_pack_data(ptr, params->key, params->key_size);
  51
  52        return 0;
  53}
  54EXPORT_SYMBOL_GPL(crypto_ecdh_encode_key);
  55
  56int crypto_ecdh_decode_key(const char *buf, unsigned int len,
  57                           struct ecdh *params)
  58{
  59        const u8 *ptr = buf;
  60        struct kpp_secret secret;
  61
  62        if (unlikely(!buf || len < ECDH_KPP_SECRET_MIN_SIZE))
  63                return -EINVAL;
  64
  65        ptr = ecdh_unpack_data(&secret, ptr, sizeof(secret));
  66        if (secret.type != CRYPTO_KPP_SECRET_TYPE_ECDH)
  67                return -EINVAL;
  68
  69        if (unlikely(len < secret.len))
  70                return -EINVAL;
  71
  72        ptr = ecdh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
  73        if (secret.len != crypto_ecdh_key_len(params))
  74                return -EINVAL;
  75
  76        /* Don't allocate memory. Set pointer to data
  77         * within the given buffer
  78         */
  79        params->key = (void *)ptr;
  80
  81        return 0;
  82}
  83EXPORT_SYMBOL_GPL(crypto_ecdh_decode_key);
  84
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