Line data    Source code

       1             : /* cipher-ctr.c  - Generic CTR mode implementation
       2             :  * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003
       3             :  *               2005, 2007, 2008, 2009, 2011 Free Software Foundation, Inc.
       4             :  *
       5             :  * This file is part of Libgcrypt.
       6             :  *
       7             :  * Libgcrypt is free software; you can redistribute it and/or modify
       8             :  * it under the terms of the GNU Lesser general Public License as
       9             :  * published by the Free Software Foundation; either version 2.1 of
      10             :  * the License, or (at your option) any later version.
      11             :  *
      12             :  * Libgcrypt is distributed in the hope that it will be useful,
      13             :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      14             :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      15             :  * GNU Lesser General Public License for more details.
      16             :  *
      17             :  * You should have received a copy of the GNU Lesser General Public
      18             :  * License along with this program; if not, see <http://www.gnu.org/licenses/>.
      19             :  */
      20             : 
      21             : #include <config.h>
      22             : #include <stdio.h>
      23             : #include <stdlib.h>
      24             : #include <string.h>
      25             : #include <errno.h>
      26             : 
      27             : #include "g10lib.h"
      28             : #include "cipher.h"
      29             : #include "bufhelp.h"
      30             : #include "./cipher-internal.h"
      31             : 
      32             : 
      33             : gcry_err_code_t
      34           0 : _gcry_cipher_ctr_encrypt (gcry_cipher_hd_t c,
      35             :                           unsigned char *outbuf, size_t outbuflen,
      36             :                           const unsigned char *inbuf, size_t inbuflen)
      37             : {
      38             :   size_t n;
      39             :   int i;
      40           0 :   gcry_cipher_encrypt_t enc_fn = c->spec->encrypt;
      41           0 :   unsigned int blocksize = c->spec->blocksize;
      42             :   size_t nblocks;
      43             :   unsigned int burn, nburn;
      44             : 
      45           0 :   if (outbuflen < inbuflen)
      46           0 :     return GPG_ERR_BUFFER_TOO_SHORT;
      47             : 
      48           0 :   burn = 0;
      49             : 
      50             :   /* First process a left over encrypted counter.  */
      51           0 :   if (c->unused)
      52             :     {
      53           0 :       gcry_assert (c->unused < blocksize);
      54           0 :       i = blocksize - c->unused;
      55           0 :       n = c->unused > inbuflen ? inbuflen : c->unused;
      56           0 :       buf_xor(outbuf, inbuf, &c->lastiv[i], n);
      57           0 :       c->unused -= n;
      58           0 :       inbuf  += n;
      59           0 :       outbuf += n;
      60           0 :       inbuflen -= n;
      61             :     }
      62             : 
      63             :   /* Use a bulk method if available.  */
      64           0 :   nblocks = inbuflen / blocksize;
      65           0 :   if (nblocks && c->bulk.ctr_enc)
      66             :     {
      67           0 :       c->bulk.ctr_enc (&c->context.c, c->u_ctr.ctr, outbuf, inbuf, nblocks);
      68           0 :       inbuf  += nblocks * blocksize;
      69           0 :       outbuf += nblocks * blocksize;
      70           0 :       inbuflen -= nblocks * blocksize;
      71             :     }
      72             : 
      73             :   /* If we don't have a bulk method use the standard method.  We also
      74             :      use this method for the a remaining partial block.  */
      75           0 :   if (inbuflen)
      76             :     {
      77             :       unsigned char tmp[MAX_BLOCKSIZE];
      78             : 
      79             :       do {
      80           0 :         nburn = enc_fn (&c->context.c, tmp, c->u_ctr.ctr);
      81           0 :         burn = nburn > burn ? nburn : burn;
      82             : 
      83           0 :         for (i = blocksize; i > 0; i--)
      84             :           {
      85           0 :             c->u_ctr.ctr[i-1]++;
      86           0 :             if (c->u_ctr.ctr[i-1] != 0)
      87           0 :               break;
      88             :           }
      89             : 
      90           0 :         n = blocksize < inbuflen ? blocksize : inbuflen;
      91           0 :         buf_xor(outbuf, inbuf, tmp, n);
      92             : 
      93           0 :         inbuflen -= n;
      94           0 :         outbuf += n;
      95           0 :         inbuf += n;
      96           0 :       } while (inbuflen);
      97             : 
      98             :       /* Save the unused bytes of the counter.  */
      99           0 :       c->unused = blocksize - n;
     100           0 :       if (c->unused)
     101           0 :         buf_cpy (c->lastiv+n, tmp+n, c->unused);
     102             : 
     103           0 :       wipememory (tmp, sizeof tmp);
     104             :     }
     105             : 
     106           0 :   if (burn > 0)
     107           0 :     _gcry_burn_stack (burn + 4 * sizeof(void *));
     108             : 
     109           0 :   return 0;
     110             : }