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 License
   7  * as published by the Free Software Foundation; either version
   8  * 2 of the License, 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) + 4 * sizeof(int))
  18
  19 static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
  20 {
  21         if (!dst || size > end - dst)
  22                 return NULL;
  23         memcpy(dst, src, size);
  24         return dst + size;
  25 }
  26
  27 static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
  28 {
  29         memcpy(dst, src, size);
  30         return src + size;
  31 }
  32
  33 static inline unsigned int dh_data_size(const struct dh *p)
  34 {
  35         return p->key_size + p->p_size + p->q_size + p->g_size;
  36 }
  37
  38 unsigned int crypto_dh_key_len(const struct dh *p)
  39 {
  40         return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
  41 }
  42 EXPORT_SYMBOL_GPL(crypto_dh_key_len);
  43
  44 int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
  45 {
  46         u8 *ptr = buf;
  47         u8 * const end = ptr + len;
  48         struct kpp_secret secret = {
  49                 .type = CRYPTO_KPP_SECRET_TYPE_DH,
  50                 .len = len
  51         };
  52
  53         if (unlikely(!len))
  54                 return -EINVAL;
  55
  56         ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
  57         ptr = dh_pack_data(ptr, end, &params->key_size,
  58                            sizeof(params->key_size));
  59         ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
  60         ptr = dh_pack_data(ptr, end, &params->q_size, sizeof(params->q_size));
  61         ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
  62         ptr = dh_pack_data(ptr, end, params->key, params->key_size);
  63         ptr = dh_pack_data(ptr, end, params->p, params->p_size);
  64         ptr = dh_pack_data(ptr, end, params->q, params->q_size);
  65         ptr = dh_pack_data(ptr, end, params->g, params->g_size);
  66         if (ptr != end)
  67                 return -EINVAL;
  68         return 0;
  69 }
  70 EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
  71
  72 int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
  73 {
  74         const u8 *ptr = buf;
  75         struct kpp_secret secret;
  76
  77         if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
  78                 return -EINVAL;
  79
  80         ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
  81         if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
  82                 return -EINVAL;
  83
  84         ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
  85         ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
  86         ptr = dh_unpack_data(&params->q_size, ptr, sizeof(params->q_size));
  87         ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
  88         if (secret.len != crypto_dh_key_len(params))
  89                 return -EINVAL;
  90
  91         /*
  92          * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
  93          * some drivers assume otherwise.
  94          */
  95         if (params->key_size > params->p_size ||
  96             params->g_size > params->p_size || params->q_size > params->p_size)
  97                 return -EINVAL;
  98
  99         /* Don't allocate memory. Set pointers to data within
 100          * the given buffer
 101          */
 102         params->key = (void *)ptr;
 103         params->p = (void *)(ptr + params->key_size);
 104         params->q = (void *)(ptr + params->key_size + params->p_size);
 105         params->g = (void *)(ptr + params->key_size + params->p_size +
 106                              params->q_size);
 107
 108         /*
 109          * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
 110          * to corner cases such as 'mod 0' being undefined or
 111          * crypto_kpp_maxsize() returning 0.
 112          */
 113         if (memchr_inv(params->p, 0, params->p_size) == NULL)
 114                 return -EINVAL;
 115
 116         /* It is permissible to not provide Q. */
 117         if (params->q_size == 0)
 118                 params->q = NULL;
 119
 120         return 0;
 121 }
 122 EXPORT_SYMBOL_GPL(crypto_dh_decode_key);