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cipher-cbc.c
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/* cipher-cbc.c - Generic CBC mode implementation
* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003
* 2005, 2007, 2008, 2009, 2011 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Libgcrypt is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser general Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* Libgcrypt is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "g10lib.h"
#include "cipher.h"
#include "./cipher-internal.h"
#include "bufhelp.h"
gcry_err_code_t
_gcry_cipher_cbc_encrypt (gcry_cipher_hd_t c,
unsigned char *outbuf, size_t outbuflen,
const unsigned char *inbuf, size_t inbuflen)
{
size_t n;
unsigned char *ivp;
int i;
size_t blocksize = c->spec->blocksize;
gcry_cipher_encrypt_t enc_fn = c->spec->encrypt;
size_t nblocks = inbuflen / blocksize;
unsigned int burn, nburn;
if (outbuflen < ((c->flags & GCRY_CIPHER_CBC_MAC)? blocksize : inbuflen))
return GPG_ERR_BUFFER_TOO_SHORT;
if ((inbuflen % blocksize)
&& !(inbuflen > blocksize
&& (c->flags & GCRY_CIPHER_CBC_CTS)))
return GPG_ERR_INV_LENGTH;
burn = 0;
if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
{
if ((inbuflen % blocksize) == 0)
nblocks--;
}
if (c->bulk.cbc_enc)
{
c->bulk.cbc_enc (&c->context.c, c->u_iv.iv, outbuf, inbuf, nblocks,
(c->flags & GCRY_CIPHER_CBC_MAC));
inbuf += nblocks * blocksize;
if (!(c->flags & GCRY_CIPHER_CBC_MAC))
outbuf += nblocks * blocksize;
}
else
{
ivp = c->u_iv.iv;
for (n=0; n < nblocks; n++ )
{
buf_xor (outbuf, inbuf, ivp, blocksize);
nburn = enc_fn ( &c->context.c, outbuf, outbuf );
burn = nburn > burn ? nburn : burn;
ivp = outbuf;
inbuf += blocksize;
if (!(c->flags & GCRY_CIPHER_CBC_MAC))
outbuf += blocksize;
}
if (ivp != c->u_iv.iv)
buf_cpy (c->u_iv.iv, ivp, blocksize );
}
if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
{
/* We have to be careful here, since outbuf might be equal to
inbuf. */
size_t restbytes;
unsigned char b;
if ((inbuflen % blocksize) == 0)
restbytes = blocksize;
else
restbytes = inbuflen % blocksize;
outbuf -= blocksize;
for (ivp = c->u_iv.iv, i = 0; i < restbytes; i++)
{
b = inbuf[i];
outbuf[blocksize + i] = outbuf[i];
outbuf[i] = b ^ *ivp++;
}
for (; i < blocksize; i++)
outbuf[i] = 0 ^ *ivp++;
nburn = enc_fn (&c->context.c, outbuf, outbuf);
burn = nburn > burn ? nburn : burn;
buf_cpy (c->u_iv.iv, outbuf, blocksize);
}
if (burn > 0)
_gcry_burn_stack (burn + 4 * sizeof(void *));
return 0;
}
gcry_err_code_t
_gcry_cipher_cbc_decrypt (gcry_cipher_hd_t c,
unsigned char *outbuf, size_t outbuflen,
const unsigned char *inbuf, size_t inbuflen)
{
size_t n;
int i;
size_t blocksize = c->spec->blocksize;
gcry_cipher_decrypt_t dec_fn = c->spec->decrypt;
size_t nblocks = inbuflen / blocksize;
unsigned int burn, nburn;
if (outbuflen < inbuflen)
return GPG_ERR_BUFFER_TOO_SHORT;
if ((inbuflen % blocksize)
&& !(inbuflen > blocksize
&& (c->flags & GCRY_CIPHER_CBC_CTS)))
return GPG_ERR_INV_LENGTH;
burn = 0;
if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
{
nblocks--;
if ((inbuflen % blocksize) == 0)
nblocks--;
buf_cpy (c->lastiv, c->u_iv.iv, blocksize);
}
if (c->bulk.cbc_dec)
{
c->bulk.cbc_dec (&c->context.c, c->u_iv.iv, outbuf, inbuf, nblocks);
inbuf += nblocks * blocksize;
outbuf += nblocks * blocksize;
}
else
{
for (n=0; n < nblocks; n++ )
{
/* Because outbuf and inbuf might be the same, we must not overwrite
the original ciphertext block. We use LASTIV as intermediate
storage here because it is not used otherwise. */
nburn = dec_fn ( &c->context.c, c->lastiv, inbuf );
burn = nburn > burn ? nburn : burn;
buf_xor_n_copy_2(outbuf, c->lastiv, c->u_iv.iv, inbuf, blocksize);
inbuf += blocksize;
outbuf += blocksize;
}
}
if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
{
size_t restbytes;
if ((inbuflen % blocksize) == 0)
restbytes = blocksize;
else
restbytes = inbuflen % blocksize;
buf_cpy (c->lastiv, c->u_iv.iv, blocksize ); /* Save Cn-2. */
buf_cpy (c->u_iv.iv, inbuf + blocksize, restbytes ); /* Save Cn. */
nburn = dec_fn ( &c->context.c, outbuf, inbuf );
burn = nburn > burn ? nburn : burn;
buf_xor(outbuf, outbuf, c->u_iv.iv, restbytes);
buf_cpy (outbuf + blocksize, outbuf, restbytes);
for(i=restbytes; i < blocksize; i++)
c->u_iv.iv[i] = outbuf[i];
nburn = dec_fn (&c->context.c, outbuf, c->u_iv.iv);
burn = nburn > burn ? nburn : burn;
buf_xor(outbuf, outbuf, c->lastiv, blocksize);
/* c->lastiv is now really lastlastiv, does this matter? */
}
if (burn > 0)
_gcry_burn_stack (burn + 4 * sizeof(void *));
return 0;
}

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