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/* cipher.c - En-/De-ciphering filter
* Copyright (C) 1998 Free Software Foundation, Inc.
*
* This file is part of GNUPG.
*
* GNUPG is free software; you can redistribute it and/or modify
* 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,
* 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 "errors.h"
#include "iobuf.h"
#include "memory.h"
#include "util.h"
#include "filter.h"
#include "packet.h"
#include "options.h"
#define MIN_PARTIAL_SIZE 512
static void
write_header( cipher_filter_context_t *cfx, IOBUF a )
{
PACKET pkt;
PKT_encrypted ed;
byte temp[10];
memset( &ed, 0, sizeof ed );
ed.len = cfx->datalen;
ed.new_ctb = !ed.len && !opt.rfc1991;
init_packet( &pkt );
pkt.pkttype = PKT_ENCRYPTED;
pkt.pkt.encrypted = &ed;
if( build_packet( a, &pkt ))
log_bug("build_packet(ENCR_DATA) failed\n");
randomize_buffer( temp, 8, 1 );
temp[8] = temp[6];
temp[9] = temp[7];
cfx->cipher_hd = cipher_open( cfx->dek->algo, CIPHER_MODE_AUTO_CFB, 1 );
cipher_setkey( cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen );
cipher_setiv( cfx->cipher_hd, NULL );
cipher_encrypt( cfx->cipher_hd, temp, temp, 10);
cipher_sync( cfx->cipher_hd );
iobuf_write(a, temp, 10);
cfx->header=1;
}
/****************
* This filter is used to en/de-cipher data with a conventional algorithm
*/
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;
if( control == IOBUFCTRL_UNDERFLOW ) { /* decrypt */
rc = -1; /* not yet used */
}
else if( control == IOBUFCTRL_FLUSH ) { /* encrypt */
assert(a);
if( !cfx->header ) {
write_header( cfx, a );
}
cipher_encrypt( cfx->cipher_hd, buf, buf, size);
if( iobuf_write( a, buf, size ) )
rc = G10ERR_WRITE_FILE;
}
else if( control == IOBUFCTRL_FREE ) {
cipher_close(cfx->cipher_hd);
}
else if( control == IOBUFCTRL_DESC ) {
*(char**)buf = "cipher_filter";
}
return rc;
}
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