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      310654 : _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      310654 :   gcry_cipher_encrypt_t enc_fn = c->spec->encrypt;
      41      310654 :   unsigned int blocksize = c->spec->blocksize;
      42             :   size_t nblocks;
      43             :   unsigned int burn, nburn;
      44             : 
      45             :   /* Tell compiler that we require a cipher with a 64bit or 128 bit block
      46             :    * length, to allow better optimization of this function.  */
      47      310654 :   if (blocksize > 16 || blocksize < 8 || blocksize & (8 - 1))
      48           0 :     return GPG_ERR_INV_LENGTH;
      49             : 
      50      310654 :   if (outbuflen < inbuflen)
      51          80 :     return GPG_ERR_BUFFER_TOO_SHORT;
      52             : 
      53      310574 :   burn = 0;
      54             : 
      55             :   /* First process a left over encrypted counter.  */
      56      310574 :   if (c->unused)
      57             :     {
      58       68112 :       gcry_assert (c->unused < blocksize);
      59       68112 :       i = blocksize - c->unused;
      60       68112 :       n = c->unused > inbuflen ? inbuflen : c->unused;
      61       68112 :       buf_xor(outbuf, inbuf, &c->lastiv[i], n);
      62       68112 :       c->unused -= n;
      63       68112 :       inbuf  += n;
      64       68112 :       outbuf += n;
      65       68112 :       inbuflen -= n;
      66             :     }
      67             : 
      68             :   /* Use a bulk method if available.  */
      69      310574 :   nblocks = inbuflen / blocksize;
      70      310574 :   if (nblocks && c->bulk.ctr_enc)
      71             :     {
      72      201344 :       c->bulk.ctr_enc (&c->context.c, c->u_ctr.ctr, outbuf, inbuf, nblocks);
      73      201344 :       inbuf  += nblocks * blocksize;
      74      201344 :       outbuf += nblocks * blocksize;
      75      201344 :       inbuflen -= nblocks * blocksize;
      76             :     }
      77             : 
      78             :   /* If we don't have a bulk method use the standard method.  We also
      79             :      use this method for the a remaining partial block.  */
      80      310574 :   if (inbuflen)
      81             :     {
      82             :       unsigned char tmp[MAX_BLOCKSIZE];
      83             : 
      84             :       do {
      85     4497412 :         nburn = enc_fn (&c->context.c, tmp, c->u_ctr.ctr);
      86     4497412 :         burn = nburn > burn ? nburn : burn;
      87             : 
      88     4512220 :         for (i = blocksize; i > 0; i--)
      89             :           {
      90     4512220 :             c->u_ctr.ctr[i-1]++;
      91     4512220 :             if (c->u_ctr.ctr[i-1] != 0)
      92     4497412 :               break;
      93             :           }
      94             : 
      95     4497412 :         n = blocksize < inbuflen ? blocksize : inbuflen;
      96     4497412 :         buf_xor(outbuf, inbuf, tmp, n);
      97             : 
      98     4497412 :         inbuflen -= n;
      99     4497412 :         outbuf += n;
     100     4497412 :         inbuf += n;
     101     4497412 :       } while (inbuflen);
     102             : 
     103             :       /* Save the unused bytes of the counter.  */
     104      103934 :       c->unused = blocksize - n;
     105      103934 :       if (c->unused)
     106       73706 :         buf_cpy (c->lastiv+n, tmp+n, c->unused);
     107             : 
     108      103934 :       wipememory (tmp, sizeof tmp);
     109             :     }
     110             : 
     111      310574 :   if (burn > 0)
     112       84228 :     _gcry_burn_stack (burn + 4 * sizeof(void *));
     113             : 
     114      310574 :   return 0;
     115             : }