121 строка
3.3 KiB
C
121 строка
3.3 KiB
C
/* cipher-ctr.c - Generic CTR mode implementation
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* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003
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* 2005, 2007, 2008, 2009, 2011 Free Software Foundation, Inc.
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*
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* This file is part of Libgcrypt.
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*
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* Libgcrypt is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser general Public License as
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* published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* Libgcrypt is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include "g10lib.h"
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#include "cipher.h"
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#include "bufhelp.h"
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#include "./cipher-internal.h"
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gcry_err_code_t
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_gcry_cipher_ctr_encrypt (gcry_cipher_hd_t c,
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unsigned char *outbuf, size_t outbuflen,
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const unsigned char *inbuf, size_t inbuflen)
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{
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size_t n;
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int i;
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gcry_cipher_encrypt_t enc_fn = c->spec->encrypt;
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size_t blocksize_shift = _gcry_blocksize_shift(c);
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size_t blocksize = 1 << blocksize_shift;
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size_t nblocks;
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unsigned int burn, nburn;
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if (outbuflen < inbuflen)
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return GPG_ERR_BUFFER_TOO_SHORT;
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burn = 0;
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/* First process a left over encrypted counter. */
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if (c->unused)
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{
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gcry_assert (c->unused < blocksize);
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i = blocksize - c->unused;
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n = c->unused > inbuflen ? inbuflen : c->unused;
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buf_xor(outbuf, inbuf, &c->lastiv[i], n);
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c->unused -= n;
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inbuf += n;
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outbuf += n;
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inbuflen -= n;
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}
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/* Use a bulk method if available. */
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nblocks = inbuflen >> blocksize_shift;
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if (nblocks && c->bulk.ctr_enc)
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{
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c->bulk.ctr_enc (&c->context.c, c->u_ctr.ctr, outbuf, inbuf, nblocks);
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inbuf += nblocks << blocksize_shift;
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outbuf += nblocks << blocksize_shift;
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inbuflen -= nblocks << blocksize_shift;
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}
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/* If we don't have a bulk method use the standard method. We also
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use this method for the a remaining partial block. */
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if (inbuflen)
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{
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unsigned char tmp[MAX_BLOCKSIZE];
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n = blocksize;
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do
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{
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nburn = enc_fn (&c->context.c, tmp, c->u_ctr.ctr);
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burn = nburn > burn ? nburn : burn;
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cipher_block_add(c->u_ctr.ctr, 1, blocksize);
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if (inbuflen < blocksize)
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break;
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cipher_block_xor(outbuf, inbuf, tmp, blocksize);
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inbuflen -= n;
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outbuf += n;
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inbuf += n;
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}
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while (inbuflen);
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if (inbuflen)
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{
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n = inbuflen;
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buf_xor(outbuf, inbuf, tmp, inbuflen);
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inbuflen -= n;
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outbuf += n;
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inbuf += n;
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}
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/* Save the unused bytes of the counter. */
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c->unused = blocksize - n;
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if (c->unused)
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buf_cpy (c->lastiv+n, tmp+n, c->unused);
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wipememory (tmp, sizeof tmp);
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}
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if (burn > 0)
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_gcry_burn_stack (burn + 4 * sizeof(void *));
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return 0;
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}
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