linux/crypto/ecdh_helper.c
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   1/*
   2 * Copyright (c) 2016, Intel Corporation
   3 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
   4 *
   5 * This program is free software; you can redistribute it and/or
   6 * modify it under the terms of the GNU General Public Licence
   7 * as published by the Free Software Foundation; either version
   8 * 2 of the Licence, or (at your option) any later version.
   9 */
  10#include <linux/kernel.h>
  11#include <linux/export.h>
  12#include <linux/err.h>
  13#include <linux/string.h>
  14#include <crypto/ecdh.h>
  15#include <crypto/kpp.h>
  16
  17#define ECDH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 2 * sizeof(short))
  18
  19static inline u8 *ecdh_pack_data(void *dst, const void *src, size_t sz)
  20{
  21        memcpy(dst, src, sz);
  22        return dst + sz;
  23}
  24
  25static inline const u8 *ecdh_unpack_data(void *dst, const void *src, size_t sz)
  26{
  27        memcpy(dst, src, sz);
  28        return src + sz;
  29}
  30
  31int crypto_ecdh_key_len(const struct ecdh *params)
  32{
  33        return ECDH_KPP_SECRET_MIN_SIZE + params->key_size;
  34}
  35EXPORT_SYMBOL_GPL(crypto_ecdh_key_len);
  36
  37int crypto_ecdh_encode_key(char *buf, unsigned int len,
  38                           const struct ecdh *params)
  39{
  40        u8 *ptr = buf;
  41        struct kpp_secret secret = {
  42                .type = CRYPTO_KPP_SECRET_TYPE_ECDH,
  43                .len = len
  44        };
  45
  46        if (unlikely(!buf))
  47                return -EINVAL;
  48
  49        if (len != crypto_ecdh_key_len(params))
  50                return -EINVAL;
  51
  52        ptr = ecdh_pack_data(ptr, &secret, sizeof(secret));
  53        ptr = ecdh_pack_data(ptr, &params->curve_id, sizeof(params->curve_id));
  54        ptr = ecdh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
  55        ecdh_pack_data(ptr, params->key, params->key_size);
  56
  57        return 0;
  58}
  59EXPORT_SYMBOL_GPL(crypto_ecdh_encode_key);
  60
  61int crypto_ecdh_decode_key(const char *buf, unsigned int len,
  62                           struct ecdh *params)
  63{
  64        const u8 *ptr = buf;
  65        struct kpp_secret secret;
  66
  67        if (unlikely(!buf || len < ECDH_KPP_SECRET_MIN_SIZE))
  68                return -EINVAL;
  69
  70        ptr = ecdh_unpack_data(&secret, ptr, sizeof(secret));
  71        if (secret.type != CRYPTO_KPP_SECRET_TYPE_ECDH)
  72                return -EINVAL;
  73
  74        ptr = ecdh_unpack_data(&params->curve_id, ptr, sizeof(params->curve_id));
  75        ptr = ecdh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
  76        if (secret.len != crypto_ecdh_key_len(params))
  77                return -EINVAL;
  78
  79        /* Don't allocate memory. Set pointer to data
  80         * within the given buffer
  81         */
  82        params->key = (void *)ptr;
  83
  84        return 0;
  85}
  86EXPORT_SYMBOL_GPL(crypto_ecdh_decode_key);
  87