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Repo Admin 2002-10-19 07:55:27 +00:00
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g10/cipher.c
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/* cipher.c - En-/De-ciphering filter
* Copyright (C) 1998, 1999, 2000, 2001 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"
#include "main.h"
#include "status.h"
#define MIN_PARTIAL_SIZE 512
static void
write_header( cipher_filter_context_t *cfx, IOBUF a )
{
PACKET pkt;
PKT_encrypted ed;
byte temp[18];
unsigned blocksize;
unsigned nprefix;
blocksize = cipher_get_blocksize( cfx->dek->algo );
if( blocksize < 8 || blocksize > 16 )
log_fatal("unsupported blocksize %u\n", blocksize );
memset( &ed, 0, sizeof ed );
ed.len = cfx->datalen;
ed.extralen = blocksize+2;
ed.new_ctb = !ed.len && !opt.rfc1991;
if( cfx->dek->use_mdc ) {
ed.mdc_method = DIGEST_ALGO_SHA1;
cfx->mdc_hash = md_open( DIGEST_ALGO_SHA1, 0 );
if ( DBG_HASHING )
md_start_debug( cfx->mdc_hash, "creatmdc" );
}
{
char buf[20];
sprintf (buf, "%d %d", ed.mdc_method, cfx->dek->algo);
write_status_text (STATUS_BEGIN_ENCRYPTION, buf);
}
init_packet( &pkt );
pkt.pkttype = cfx->dek->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;
randomize_buffer( temp, nprefix, 1 );
temp[nprefix] = temp[nprefix-2];
temp[nprefix+1] = temp[nprefix-1];
print_cipher_algo_note( cfx->dek->algo );
cfx->cipher_hd = cipher_open( cfx->dek->algo,
cfx->dek->use_mdc? CIPHER_MODE_CFB
: CIPHER_MODE_AUTO_CFB, 1 );
/* log_hexdump( "thekey", cfx->dek->key, cfx->dek->keylen );*/
cipher_setkey( cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen );
cipher_setiv( cfx->cipher_hd, NULL, 0 );
/* log_hexdump( "prefix", temp, nprefix+2 ); */
if( cfx->mdc_hash ) /* hash the "IV" */
md_write( cfx->mdc_hash, temp, nprefix+2 );
cipher_encrypt( cfx->cipher_hd, temp, temp, nprefix+2);
cipher_sync( cfx->cipher_hd );
iobuf_write(a, temp, nprefix+2);
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 );
}
if( cfx->mdc_hash )
md_write( cfx->mdc_hash, buf, size );
cipher_encrypt( cfx->cipher_hd, buf, buf, size);
if( iobuf_write( a, buf, size ) )
rc = G10ERR_WRITE_FILE;
}
else if( control == IOBUFCTRL_FREE ) {
if( cfx->mdc_hash ) {
byte *hash;
int hashlen = md_digest_length( 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;
md_putc( cfx->mdc_hash, temp[0] );
md_putc( cfx->mdc_hash, temp[1] );
md_final( cfx->mdc_hash );
hash = md_read( cfx->mdc_hash, 0 );
memcpy(temp+2, hash, 20);
cipher_encrypt( cfx->cipher_hd, temp, temp, 22 );
md_close( cfx->mdc_hash ); cfx->mdc_hash = NULL;
if( iobuf_write( a, temp, 22 ) )
log_error("writing MDC packet failed\n" );
}
cipher_close(cfx->cipher_hd);
}
else if( control == IOBUFCTRL_DESC ) {
*(char**)buf = "cipher_filter";
}
return rc;
}