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gnupg/g10/cipher.c

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/* cipher.c - En-/De-ciphering filter
* Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
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*
* This file is part of GnuPG.
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*
* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <gcrypt.h>
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#include "errors.h"
#include "iobuf.h"
#include "util.h"
#include "filter.h"
#include "packet.h"
#include "options.h"
#include "main.h"
#include "status.h"
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#define MIN_PARTIAL_SIZE 512
static void
write_header( cipher_filter_context_t *cfx, IOBUF a )
{
PACKET pkt;
PKT_encrypted ed;
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byte temp[18];
unsigned int blocksize;
unsigned int nprefix;
int rc;
int use_mdc = opt.force_mdc;
blocksize = gcry_cipher_get_algo_blklen( cfx->dek->algo );
if( blocksize < 8 || blocksize > 16 )
log_fatal("unsupported blocksize %u\n", blocksize );
if( blocksize != 8 )
use_mdc = 1; /* enable it for all modern ciphers */
if( opt.rfc2440 )
use_mdc = 0; /* override - rfc2440 does not know about MDC */
memset( &ed, 0, sizeof ed );
ed.len = cfx->datalen;
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ed.new_ctb = !ed.len && !opt.rfc1991;
if( use_mdc ) {
ed.mdc_method = GCRY_MD_SHA1;
cfx->mdc_hash = gcry_md_open( GCRY_MD_SHA1, 0 );
if( !cfx->mdc_hash )
BUG();
if ( DBG_HASHING )
gcry_md_start_debug( cfx->mdc_hash, "creatmdc" );
}
init_packet( &pkt );
pkt.pkttype = use_mdc? PKT_ENCRYPTED_MDC : PKT_ENCRYPTED;
pkt.pkt.encrypted = &ed;
if( build_packet( a, &pkt ))
log_bug("build_packet(ENCR_DATA) failed\n");
nprefix = blocksize;
gcry_randomize( temp, nprefix, GCRY_STRONG_RANDOM );
temp[nprefix] = temp[nprefix-2];
temp[nprefix+1] = temp[nprefix-1];
print_cipher_algo_note( cfx->dek->algo );
if( !(cfx->cipher_hd = gcry_cipher_open( cfx->dek->algo,
GCRY_CIPHER_MODE_CFB,
GCRY_CIPHER_SECURE
| ((use_mdc || cfx->dek->algo >= 100) ?
0 : GCRY_CIPHER_ENABLE_SYNC)))
) {
/* we should never get an error here cause we already checked, that
* the algorithm is available. */
BUG();
}
/* log_hexdump( "thekey", cfx->dek->key, cfx->dek->keylen );*/
rc = gcry_cipher_setkey( cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen );
if( !rc )
rc = gcry_cipher_setiv( cfx->cipher_hd, NULL, 0 );
if( rc )
log_fatal("set key or IV failed: %s\n", gcry_strerror(rc) );
/* log_hexdump( "prefix", temp, nprefix+2 ); */
if( cfx->mdc_hash )
gcry_md_write( cfx->mdc_hash, temp, nprefix+2 );
rc = gcry_cipher_encrypt( cfx->cipher_hd, temp, nprefix+2, NULL, 0 );
if( !rc )
rc = gcry_cipher_sync( cfx->cipher_hd );
if( rc )
log_fatal("encrypt failed: %s\n", gcry_strerror(rc) );
iobuf_write(a, temp, nprefix+2);
cfx->header=1;
}
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/****************
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* This filter is used to en/de-cipher data with a conventional algorithm
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*/
int
cipher_filter( void *opaque, int control,
IOBUF a, byte *buf, size_t *ret_len)
{
size_t size = *ret_len;
cipher_filter_context_t *cfx = opaque;
int rc=0;
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if( control == IOBUFCTRL_UNDERFLOW ) { /* decrypt */
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rc = -1; /* not yet used */
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}
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else if( control == IOBUFCTRL_FLUSH ) { /* encrypt */
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assert(a);
if( !cfx->header ) {
write_status( STATUS_BEGIN_ENCRYPTION );
write_header( cfx, a );
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}
if( cfx->mdc_hash )
gcry_md_write( cfx->mdc_hash, buf, size );
rc = gcry_cipher_encrypt( cfx->cipher_hd, buf, size, NULL, 0);
if( rc )
log_fatal("encrypt failed: %s\n", gcry_strerror(rc) );
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if( iobuf_write( a, buf, size ) )
rc = GPGERR_WRITE_FILE;
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}
else if( control == IOBUFCTRL_FREE ) {
if( cfx->mdc_hash ) {
byte *hash;
int hashlen = gcry_md_get_algo_dlen( gcry_md_get_algo( cfx->mdc_hash ) );
byte temp[22];
assert( hashlen == 20 );
/* we must hash the prefix of the MDC packet here */
temp[0] = 0xd3;
temp[1] = 0x14;
gcry_md_putc( cfx->mdc_hash, temp[0] );
gcry_md_putc( cfx->mdc_hash, temp[1] );
hash = gcry_md_read( cfx->mdc_hash, 0 );
memcpy(temp+2, hash, 20);
rc = gcry_cipher_encrypt( cfx->cipher_hd, temp, 22, NULL, 0 );
if( rc )
log_fatal("encrypt failed: %s\n", gcry_strerror(rc) );
gcry_md_close( cfx->mdc_hash ); cfx->mdc_hash = NULL;
if( iobuf_write( a, temp, 22 ) )
log_error("writing MDC packet failed\n" );
}
gcry_cipher_close(cfx->cipher_hd);
write_status( STATUS_END_ENCRYPTION );
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}
else if( control == IOBUFCTRL_DESC ) {
*(char**)buf = "cipher_filter";
}
return rc;
}