crypto/dh_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/dh.h>
  11 #include <crypto/kpp.h>
  12
  13 #define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 4 * sizeof(int))
  14
  15 static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
  16 {
  17         if (!dst || size > end - dst)
  18                 return NULL;
  19         memcpy(dst, src, size);
  20         return dst + size;
  21 }
  22
  23 static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
  24 {
  25         memcpy(dst, src, size);
  26         return src + size;
  27 }
  28
  29 static inline unsigned int dh_data_size(const struct dh *p)
  30 {
  31         return p->key_size + p->p_size + p->q_size + p->g_size;
  32 }
  33
  34 unsigned int crypto_dh_key_len(const struct dh *p)
  35 {
  36         return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
  37 }
  38 EXPORT_SYMBOL_GPL(crypto_dh_key_len);
  39
  40 int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
  41 {
  42         u8 *ptr = buf;
  43         u8 * const end = ptr + len;
  44         struct kpp_secret secret = {
  45                 .type = CRYPTO_KPP_SECRET_TYPE_DH,
  46                 .len = len
  47         };
  48
  49         if (unlikely(!len))
  50                 return -EINVAL;
  51
  52         ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
  53         ptr = dh_pack_data(ptr, end, &params->key_size,
  54                            sizeof(params->key_size));
  55         ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
  56         ptr = dh_pack_data(ptr, end, &params->q_size, sizeof(params->q_size));
  57         ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
  58         ptr = dh_pack_data(ptr, end, params->key, params->key_size);
  59         ptr = dh_pack_data(ptr, end, params->p, params->p_size);
  60         ptr = dh_pack_data(ptr, end, params->q, params->q_size);
  61         ptr = dh_pack_data(ptr, end, params->g, params->g_size);
  62         if (ptr != end)
  63                 return -EINVAL;
  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->q_size, ptr, sizeof(params->q_size));
  83         ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
  84         if (secret.len != crypto_dh_key_len(params))
  85                 return -EINVAL;
  86
  87         /*
  88          * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
  89          * some drivers assume otherwise.
  90          */
  91         if (params->key_size > params->p_size ||
  92             params->g_size > params->p_size || params->q_size > params->p_size)
  93                 return -EINVAL;
  94
  95         /* Don't allocate memory. Set pointers to data within
  96          * the given buffer
  97          */
  98         params->key = (void *)ptr;
  99         params->p = (void *)(ptr + params->key_size);
 100         params->q = (void *)(ptr + params->key_size + params->p_size);
 101         params->g = (void *)(ptr + params->key_size + params->p_size +
 102                              params->q_size);
 103
 104         /*
 105          * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
 106          * to corner cases such as 'mod 0' being undefined or
 107          * crypto_kpp_maxsize() returning 0.
 108          */
 109         if (memchr_inv(params->p, 0, params->p_size) == NULL)
 110                 return -EINVAL;
 111
 112         /* It is permissible to not provide Q. */
 113         if (params->q_size == 0)
 114                 params->q = NULL;
 115
 116         return 0;
 117 }
 118 EXPORT_SYMBOL_GPL(crypto_dh_decode_key);