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Linux/crypto/dh_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/dh.h>
 15 #include <crypto/kpp.h>
 16 
 17 #define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
 18 
 19 static inline u8 *dh_pack_data(void *dst, const void *src, size_t size)
 20 {
 21         memcpy(dst, src, size);
 22         return dst + size;
 23 }
 24 
 25 static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
 26 {
 27         memcpy(dst, src, size);
 28         return src + size;
 29 }
 30 
 31 static inline int dh_data_size(const struct dh *p)
 32 {
 33         return p->key_size + p->p_size + p->g_size;
 34 }
 35 
 36 int crypto_dh_key_len(const struct dh *p)
 37 {
 38         return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
 39 }
 40 EXPORT_SYMBOL_GPL(crypto_dh_key_len);
 41 
 42 int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
 43 {
 44         u8 *ptr = buf;
 45         struct kpp_secret secret = {
 46                 .type = CRYPTO_KPP_SECRET_TYPE_DH,
 47                 .len = len
 48         };
 49 
 50         if (unlikely(!buf))
 51                 return -EINVAL;
 52 
 53         if (len != crypto_dh_key_len(params))
 54                 return -EINVAL;
 55 
 56         ptr = dh_pack_data(ptr, &secret, sizeof(secret));
 57         ptr = dh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
 58         ptr = dh_pack_data(ptr, &params->p_size, sizeof(params->p_size));
 59         ptr = dh_pack_data(ptr, &params->g_size, sizeof(params->g_size));
 60         ptr = dh_pack_data(ptr, params->key, params->key_size);
 61         ptr = dh_pack_data(ptr, params->p, params->p_size);
 62         dh_pack_data(ptr, params->g, params->g_size);
 63 
 64         return 0;
 65 }
 66 EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
 67 
 68 int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 69 {
 70         const u8 *ptr = buf;
 71         struct kpp_secret secret;
 72 
 73         if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
 74                 return -EINVAL;
 75 
 76         ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
 77         if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
 78                 return -EINVAL;
 79 
 80         ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
 81         ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
 82         ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
 83         if (secret.len != crypto_dh_key_len(params))
 84                 return -EINVAL;
 85 
 86         /* Don't allocate memory. Set pointers to data within
 87          * the given buffer
 88          */
 89         params->key = (void *)ptr;
 90         params->p = (void *)(ptr + params->key_size);
 91         params->g = (void *)(ptr + params->key_size + params->p_size);
 92 
 93         return 0;
 94 }
 95 EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
 96 

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