rsa-decrypt-tr.c

   1 /* rsa-decrypt-tr.c
   2
   3    RSA decryption, using randomized RSA blinding to be more resistant
   4    to timing attacks.
   5
   6    Copyright (C) 2001, 2012 Niels Möller, Nikos Mavrogiannopoulos
   7
   8    This file is part of GNU Nettle.
   9
  10    GNU Nettle is free software: you can redistribute it and/or
  11    modify it under the terms of either:
  12
  13      * the GNU Lesser General Public License as published by the Free
  14        Software Foundation; either version 3 of the License, or (at your
  15        option) any later version.
  16
  17    or
  18
  19      * the GNU General Public License as published by the Free
  20        Software Foundation; either version 2 of the License, or (at your
  21        option) any later version.
  22
  23    or both in parallel, as here.
  24
  25    GNU Nettle is distributed in the hope that it will be useful,
  26    but WITHOUT ANY WARRANTY; without even the implied warranty of
  27    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  28    General Public License for more details.
  29
  30    You should have received copies of the GNU General Public License and
  31    the GNU Lesser General Public License along with this program.  If
  32    not, see http://www.gnu.org/licenses/.
  33 */
  34
  35 #if HAVE_CONFIG_H
  36 # include "config.h"
  37 #endif
  38
  39 #include "rsa-internal.h"
  40 #include "pkcs1-internal.h"
  41 #include "gmp-glue.h"
  42
  43 int
  44 rsa_decrypt_tr(const struct rsa_public_key *pub,
  45                const struct rsa_private_key *key,
  46                void *random_ctx, nettle_random_func *random,
  47                size_t *length, uint8_t *message,
  48                const mpz_t gibberish)
  49 {
  50   TMP_GMP_DECL (m, mp_limb_t);
  51   TMP_GMP_DECL (em, uint8_t);
  52   mp_size_t key_limb_size;
  53   int res;
  54
  55   /* First check that input is in range. */
  56   if (mpz_sgn (gibberish) < 0 || mpz_cmp (gibberish, pub->n) >= 0)
  57     return 0;
  58
  59   key_limb_size = mpz_size(pub->n);
  60
  61   TMP_GMP_ALLOC (m, key_limb_size);
  62   TMP_GMP_ALLOC (em, key->size);
  63   mpz_limbs_copy(m, gibberish, key_limb_size);
  64
  65   res = _rsa_sec_compute_root_tr (pub, key, random_ctx, random, m, m);
  66
  67   mpn_get_base256 (em, key->size, m, key_limb_size);
  68
  69   res &= _pkcs1_sec_decrypt_variable (length, message, key->size, em);
  70
  71   TMP_GMP_FREE (em);
  72   TMP_GMP_FREE (m);
  73   return res;
  74 }