crypto/ecdh_helper.c

   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) + 2 * sizeof(short))
  14
  15 static 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
  21 static 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
  27 unsigned int crypto_ecdh_key_len(const struct ecdh *params)
  28 {
  29         return ECDH_KPP_SECRET_MIN_SIZE + params->key_size;
  30 }
  31 EXPORT_SYMBOL_GPL(crypto_ecdh_key_len);
  32
  33 int 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->curve_id, sizeof(params->curve_id));
  50         ptr = ecdh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
  51         ecdh_pack_data(ptr, params->key, params->key_size);
  52
  53         return 0;
  54 }
  55 EXPORT_SYMBOL_GPL(crypto_ecdh_encode_key);
  56
  57 int crypto_ecdh_decode_key(const char *buf, unsigned int len,
  58                            struct ecdh *params)
  59 {
  60         const u8 *ptr = buf;
  61         struct kpp_secret secret;
  62
  63         if (unlikely(!buf || len < ECDH_KPP_SECRET_MIN_SIZE))
  64                 return -EINVAL;
  65
  66         ptr = ecdh_unpack_data(&secret, ptr, sizeof(secret));
  67         if (secret.type != CRYPTO_KPP_SECRET_TYPE_ECDH)
  68                 return -EINVAL;
  69
  70         ptr = ecdh_unpack_data(&params->curve_id, ptr, sizeof(params->curve_id));
  71         ptr = ecdh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
  72         if (secret.len != crypto_ecdh_key_len(params))
  73                 return -EINVAL;
  74
  75         /* Don't allocate memory. Set pointer to data
  76          * within the given buffer
  77          */
  78         params->key = (void *)ptr;
  79
  80         return 0;
  81 }
  82 EXPORT_SYMBOL_GPL(crypto_ecdh_decode_key);