src/crypto/crypto_internal-modexp.c

   1 /*
   2  * Crypto wrapper for internal crypto implementation - modexp
   3  * Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
   4  *
   5  * This software may be distributed under the terms of the BSD license.
   6  * See README for more details.
   7  */
   8
   9 #include "includes.h"
  10
  11 #include "common.h"
  12 #include "tls/bignum.h"
  13 #include "crypto.h"
  14
  15
  16 int crypto_dh_init(u8 generator, const u8 *prime, size_t prime_len, u8 *privkey,
  17                    u8 *pubkey)
  18 {
  19         size_t pubkey_len, pad;
  20
  21         if (os_get_random(privkey, prime_len) < 0)
  22                 return -1;
  23         if (os_memcmp(privkey, prime, prime_len) > 0) {
  24                 /* Make sure private value is smaller than prime */
  25                 privkey[0] = 0;
  26         }
  27
  28         pubkey_len = prime_len;
  29         if (crypto_mod_exp(&generator, 1, privkey, prime_len, prime, prime_len,
  30                            pubkey, &pubkey_len) < 0)
  31                 return -1;
  32         if (pubkey_len < prime_len) {
  33                 pad = prime_len - pubkey_len;
  34                 os_memmove(pubkey + pad, pubkey, pubkey_len);
  35                 os_memset(pubkey, 0, pad);
  36         }
  37
  38         return 0;
  39 }
  40
  41
  42 int crypto_dh_derive_secret(u8 generator, const u8 *prime, size_t prime_len,
  43                             const u8 *privkey, size_t privkey_len,
  44                             const u8 *pubkey, size_t pubkey_len,
  45                             u8 *secret, size_t *len)
  46 {
  47         return crypto_mod_exp(pubkey, pubkey_len, privkey, privkey_len,
  48                               prime, prime_len, secret, len);
  49 }
  50
  51
  52 int crypto_mod_exp(const u8 *base, size_t base_len,
  53                    const u8 *power, size_t power_len,
  54                    const u8 *modulus, size_t modulus_len,
  55                    u8 *result, size_t *result_len)
  56 {
  57         struct bignum *bn_base, *bn_exp, *bn_modulus, *bn_result;
  58         int ret = -1;
  59
  60         bn_base = bignum_init();
  61         bn_exp = bignum_init();
  62         bn_modulus = bignum_init();
  63         bn_result = bignum_init();
  64
  65         if (bn_base == NULL || bn_exp == NULL || bn_modulus == NULL ||
  66             bn_result == NULL)
  67                 goto error;
  68
  69         if (bignum_set_unsigned_bin(bn_base, base, base_len) < 0 ||
  70             bignum_set_unsigned_bin(bn_exp, power, power_len) < 0 ||
  71             bignum_set_unsigned_bin(bn_modulus, modulus, modulus_len) < 0)
  72                 goto error;
  73
  74         if (bignum_exptmod(bn_base, bn_exp, bn_modulus, bn_result) < 0)
  75                 goto error;
  76
  77         ret = bignum_get_unsigned_bin(bn_result, result, result_len);
  78
  79 error:
  80         bignum_deinit(bn_base);
  81         bignum_deinit(bn_exp);
  82         bignum_deinit(bn_modulus);
  83         bignum_deinit(bn_result);
  84         return ret;
  85 }