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Linux/crypto/ecdh_helper.c

  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 
 19 static 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 
 25 static 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 
 31 int crypto_ecdh_key_len(const struct ecdh *params)
 32 {
 33         return ECDH_KPP_SECRET_MIN_SIZE + params->key_size;
 34 }
 35 EXPORT_SYMBOL_GPL(crypto_ecdh_key_len);
 36 
 37 int 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 }
 59 EXPORT_SYMBOL_GPL(crypto_ecdh_encode_key);
 60 
 61 int 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 }
 86 EXPORT_SYMBOL_GPL(crypto_ecdh_decode_key);
 87 

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