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         /*
  87          * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
  88          * some drivers assume otherwise.
  89          */
  90         if (params->key_size > params->p_size ||
  91             params->g_size > params->p_size)
  92                 return -EINVAL;
  93
  94         /* Don't allocate memory. Set pointers to data within
  95          * the given buffer
  96          */
  97         params->key = (void *)ptr;
  98         params->p = (void *)(ptr + params->key_size);
  99         params->g = (void *)(ptr + params->key_size + params->p_size);
 100
 101         /*
 102          * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
 103          * to corner cases such as 'mod 0' being undefined or
 104          * crypto_kpp_maxsize() returning 0.
 105          */
 106         if (memchr_inv(params->p, 0, params->p_size) == NULL)
 107                 return -EINVAL;
 108
 109         return 0;
 110 }
 111 EXPORT_SYMBOL_GPL(crypto_dh_decode_key);