lib/gnutls_mpi.c

   1 /*
   2  * Copyright (C) 2001, 2002, 2003, 2004, 2005, 2008, 2010 Free Software
   3  * Foundation, Inc.
   4  *
   5  * Author: Nikos Mavrogiannopoulos
   6  *
   7  * This file is part of GnuTLS.
   8  *
   9  * The GnuTLS is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public License
  11  * as published by the Free Software Foundation; either version 2.1 of
  12  * the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful, but
  15  * WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  22  * USA
  23  *
  24  */
  25
  26 /* Here lie everything that has to do with large numbers, libgcrypt and
  27  * other stuff that didn't fit anywhere else.
  28  */
  29
  30 #include <gnutls_int.h>
  31 #include <libtasn1.h>
  32 #include <gnutls_errors.h>
  33 #include <gnutls_num.h>
  34 #include <gnutls_mpi.h>
  35 #include <random.h>
  36
  37 /* Functions that refer to the mpi library.
  38  */
  39
  40 #define clearbit(v,n)    ((unsigned char)(v) & ~( (unsigned char)(1) << (unsigned)(n)))
  41
  42 bigint_t
  43 _gnutls_mpi_randomize (bigint_t r, unsigned int bits,
  44                        gnutls_rnd_level_t level)
  45 {
  46   size_t size = 1 + (bits / 8);
  47   int ret;
  48   int rem, i;
  49   bigint_t tmp;
  50   char tmpbuf[512];
  51   opaque *buf;
  52   int buf_release = 0;
  53
  54   if (size < sizeof (tmpbuf))
  55     {
  56       buf = tmpbuf;
  57     }
  58   else
  59     {
  60       buf = gnutls_malloc (size);
  61       if (buf == NULL)
  62         {
  63           gnutls_assert ();
  64           goto cleanup;
  65         }
  66       buf_release = 1;
  67     }
  68
  69
  70   ret = _gnutls_rnd (level, buf, size);
  71   if (ret < 0)
  72     {
  73       gnutls_assert ();
  74       goto cleanup;
  75     }
  76
  77   /* mask the bits that weren't requested */
  78   rem = bits % 8;
  79
  80   if (rem == 0)
  81     {
  82       buf[0] = 0;
  83     }
  84   else
  85     {
  86       for (i = 8; i >= rem; i--)
  87         buf[0] = clearbit (buf[0], i);
  88     }
  89
  90   ret = _gnutls_mpi_scan (&tmp, buf, size);
  91   if (ret < 0)
  92     {
  93       gnutls_assert ();
  94       goto cleanup;
  95     }
  96
  97   if (buf_release != 0)
  98     {
  99       gnutls_free (buf);
 100       buf = NULL;
 101     }
 102
 103   if (r != NULL)
 104     {
 105       _gnutls_mpi_set (r, tmp);
 106       _gnutls_mpi_release (&tmp);
 107       return r;
 108     }
 109
 110   return tmp;
 111
 112 cleanup:
 113   if (buf_release != 0)
 114     gnutls_free (buf);
 115   return NULL;
 116 }
 117
 118 void
 119 _gnutls_mpi_release (bigint_t * x)
 120 {
 121   if (*x == NULL)
 122     return;
 123
 124   _gnutls_mpi_ops.bigint_release (*x);
 125   *x = NULL;
 126 }
 127
 128 /* returns zero on success
 129  */
 130 int
 131 _gnutls_mpi_scan (bigint_t * ret_mpi, const void *buffer, size_t nbytes)
 132 {
 133   *ret_mpi =
 134     _gnutls_mpi_ops.bigint_scan (buffer, nbytes, GNUTLS_MPI_FORMAT_USG);
 135   if (*ret_mpi == NULL)
 136     {
 137       gnutls_assert ();
 138       return GNUTLS_E_MPI_SCAN_FAILED;
 139     }
 140
 141   return 0;
 142 }
 143
 144 /* returns zero on success. Fails if the number is zero.
 145  */
 146 int
 147 _gnutls_mpi_scan_nz (bigint_t * ret_mpi, const void *buffer, size_t nbytes)
 148 {
 149   int ret;
 150
 151   ret = _gnutls_mpi_scan (ret_mpi, buffer, nbytes);
 152   if (ret < 0)
 153     return ret;
 154
 155   /* MPIs with 0 bits are illegal
 156    */
 157   if (_gnutls_mpi_get_nbits (*ret_mpi) == 0)
 158     {
 159       _gnutls_mpi_release (ret_mpi);
 160       return GNUTLS_E_MPI_SCAN_FAILED;
 161     }
 162
 163   return 0;
 164 }
 165
 166 int
 167 _gnutls_mpi_scan_pgp (bigint_t * ret_mpi, const void *buffer, size_t nbytes)
 168 {
 169   *ret_mpi =
 170     _gnutls_mpi_ops.bigint_scan (buffer, nbytes, GNUTLS_MPI_FORMAT_PGP);
 171   if (*ret_mpi == NULL)
 172     {
 173       gnutls_assert ();
 174       return GNUTLS_E_MPI_SCAN_FAILED;
 175     }
 176
 177   return 0;
 178 }
 179
 180 /* Always has the first bit zero */
 181 int
 182 _gnutls_mpi_dprint_lz (const bigint_t a, gnutls_datum_t * dest)
 183 {
 184   int ret;
 185   opaque *buf = NULL;
 186   size_t bytes = 0;
 187
 188   if (dest == NULL || a == NULL)
 189     return GNUTLS_E_INVALID_REQUEST;
 190
 191   _gnutls_mpi_print_lz (a, NULL, &bytes);
 192
 193   if (bytes != 0)
 194     buf = gnutls_malloc (bytes);
 195   if (buf == NULL)
 196     return GNUTLS_E_MEMORY_ERROR;
 197
 198   ret = _gnutls_mpi_print_lz (a, buf, &bytes);
 199   if (ret < 0)
 200     {
 201       gnutls_free (buf);
 202       return ret;
 203     }
 204
 205   dest->data = buf;
 206   dest->size = bytes;
 207   return 0;
 208 }
 209
 210 int
 211 _gnutls_mpi_dprint (const bigint_t a, gnutls_datum_t * dest)
 212 {
 213   int ret;
 214   opaque *buf = NULL;
 215   size_t bytes = 0;
 216
 217   if (dest == NULL || a == NULL)
 218     return GNUTLS_E_INVALID_REQUEST;
 219
 220   _gnutls_mpi_print (a, NULL, &bytes);
 221   if (bytes != 0)
 222     buf = gnutls_malloc (bytes);
 223   if (buf == NULL)
 224     return GNUTLS_E_MEMORY_ERROR;
 225
 226   ret = _gnutls_mpi_print (a, buf, &bytes);
 227   if (ret < 0)
 228     {
 229       gnutls_free (buf);
 230       return ret;
 231     }
 232
 233   dest->data = buf;
 234   dest->size = bytes;
 235   return 0;
 236 }
 237
 238 /* This function will copy the mpi data into a datum,
 239  * but will set minimum size to 'size'. That means that
 240  * the output value is left padded with zeros.
 241  */
 242 int
 243 _gnutls_mpi_dprint_size (const bigint_t a, gnutls_datum_t * dest, size_t size)
 244 {
 245   int ret;
 246   opaque *buf = NULL;
 247   size_t bytes = 0;
 248   unsigned int i;
 249
 250   if (dest == NULL || a == NULL)
 251     return GNUTLS_E_INVALID_REQUEST;
 252
 253   _gnutls_mpi_print (a, NULL, &bytes);
 254   if (bytes != 0)
 255     buf = gnutls_malloc (MAX (size, bytes));
 256   if (buf == NULL)
 257     return GNUTLS_E_MEMORY_ERROR;
 258
 259   if (bytes <= size)
 260     {
 261       size_t diff = size - bytes;
 262       for (i = 0; i < diff; i++)
 263         buf[i] = 0;
 264       ret = _gnutls_mpi_print (a, &buf[diff], &bytes);
 265     }
 266   else
 267     {
 268       ret = _gnutls_mpi_print (a, buf, &bytes);
 269     }
 270
 271   if (ret < 0)
 272     {
 273       gnutls_free (buf);
 274       return ret;
 275     }
 276
 277   dest->data = buf;
 278   dest->size = MAX (size, bytes);
 279   return 0;
 280 }
 281
 282 /* this function reads an integer
 283  * from asn1 structs. Combines the read and mpi_scan
 284  * steps.
 285  */
 286 int
 287 _gnutls_x509_read_int (ASN1_TYPE node, const char *value, bigint_t * ret_mpi)
 288 {
 289   int result;
 290   opaque *tmpstr = NULL;
 291   int tmpstr_size;
 292
 293   tmpstr_size = 0;
 294   result = asn1_read_value (node, value, NULL, &tmpstr_size);
 295   if (result != ASN1_MEM_ERROR)
 296     {
 297       gnutls_assert ();
 298       return _gnutls_asn2err (result);
 299     }
 300
 301   tmpstr = gnutls_malloc (tmpstr_size);
 302   if (tmpstr == NULL)
 303     {
 304       gnutls_assert ();
 305       return GNUTLS_E_MEMORY_ERROR;
 306     }
 307
 308   result = asn1_read_value (node, value, tmpstr, &tmpstr_size);
 309   if (result != ASN1_SUCCESS)
 310     {
 311       gnutls_assert ();
 312       gnutls_free (tmpstr);
 313       return _gnutls_asn2err (result);
 314     }
 315
 316   result = _gnutls_mpi_scan (ret_mpi, tmpstr, tmpstr_size);
 317   gnutls_free (tmpstr);
 318
 319   if (result < 0)
 320     {
 321       gnutls_assert ();
 322       return result;
 323     }
 324
 325   return 0;
 326 }
 327
 328 /* Writes the specified integer into the specified node.
 329  */
 330 int
 331 _gnutls_x509_write_int (ASN1_TYPE node, const char *value, bigint_t mpi,
 332                         int lz)
 333 {
 334   opaque *tmpstr;
 335   size_t s_len;
 336   int result;
 337
 338   s_len = 0;
 339   if (lz)
 340     result = _gnutls_mpi_print_lz (mpi, NULL, &s_len);
 341   else
 342     result = _gnutls_mpi_print (mpi, NULL, &s_len);
 343
 344   if (result != GNUTLS_E_SHORT_MEMORY_BUFFER)
 345     {
 346       gnutls_assert ();
 347       return result;
 348     }
 349
 350   tmpstr = gnutls_malloc (s_len);
 351   if (tmpstr == NULL)
 352     {
 353       gnutls_assert ();
 354       return GNUTLS_E_MEMORY_ERROR;
 355     }
 356
 357   if (lz)
 358     result = _gnutls_mpi_print_lz (mpi, tmpstr, &s_len);
 359   else
 360     result = _gnutls_mpi_print (mpi, tmpstr, &s_len);
 361
 362   if (result != 0)
 363     {
 364       gnutls_assert ();
 365       gnutls_free (tmpstr);
 366       return GNUTLS_E_MPI_PRINT_FAILED;
 367     }
 368
 369   result = asn1_write_value (node, value, tmpstr, s_len);
 370
 371   gnutls_free (tmpstr);
 372
 373   if (result != ASN1_SUCCESS)
 374     {
 375       gnutls_assert ();
 376       return _gnutls_asn2err (result);
 377     }
 378
 379   return 0;
 380 }