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1111da19a8
symmetric compressed files. * encode.c (encode_simple, encode_crypt): If we are not using a MDC, compress even if a file is already compressed. This is to help against the chosen ciphertext attack. * pkclist.c (select_algo_from_prefs): Fix requested algorithm bug so the request succeeds even if the requested algorithm is not the first found. * cipher.c (write_header), encode.c (use_mdc, encode_simple, encode_crypt, encrypt_filter), g10.c (main): Be more eager to use a MDC. We use a MDC if the keys directly support it, if the keys list AES (any) or TWOFISH anywhere in the prefs, or if the cipher chosen does not have a 64 bit blocksize.
153 lines
4.4 KiB
C
153 lines
4.4 KiB
C
/* cipher.c - En-/De-ciphering filter
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* Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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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
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* 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
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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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 <assert.h>
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#include "errors.h"
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#include "iobuf.h"
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#include "memory.h"
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#include "util.h"
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#include "filter.h"
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#include "packet.h"
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#include "options.h"
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#include "main.h"
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#include "status.h"
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#define MIN_PARTIAL_SIZE 512
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static void
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write_header( cipher_filter_context_t *cfx, IOBUF a )
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{
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PACKET pkt;
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PKT_encrypted ed;
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byte temp[18];
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unsigned blocksize;
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unsigned nprefix;
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blocksize = cipher_get_blocksize( cfx->dek->algo );
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if( blocksize < 8 || blocksize > 16 )
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log_fatal("unsupported blocksize %u\n", blocksize );
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memset( &ed, 0, sizeof ed );
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ed.len = cfx->datalen;
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ed.extralen = blocksize+2;
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ed.new_ctb = !ed.len && !opt.rfc1991;
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if( cfx->dek->use_mdc ) {
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ed.mdc_method = DIGEST_ALGO_SHA1;
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cfx->mdc_hash = md_open( DIGEST_ALGO_SHA1, 0 );
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if ( DBG_HASHING )
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md_start_debug( cfx->mdc_hash, "creatmdc" );
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}
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{
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char buf[20];
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sprintf (buf, "%d %d", ed.mdc_method, cfx->dek->algo);
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write_status_text (STATUS_BEGIN_ENCRYPTION, buf);
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}
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init_packet( &pkt );
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pkt.pkttype = cfx->dek->use_mdc? PKT_ENCRYPTED_MDC : PKT_ENCRYPTED;
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pkt.pkt.encrypted = &ed;
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if( build_packet( a, &pkt ))
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log_bug("build_packet(ENCR_DATA) failed\n");
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nprefix = blocksize;
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randomize_buffer( temp, nprefix, 1 );
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temp[nprefix] = temp[nprefix-2];
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temp[nprefix+1] = temp[nprefix-1];
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print_cipher_algo_note( cfx->dek->algo );
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cfx->cipher_hd = cipher_open( cfx->dek->algo,
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cfx->dek->use_mdc? CIPHER_MODE_CFB
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: CIPHER_MODE_AUTO_CFB, 1 );
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/* log_hexdump( "thekey", cfx->dek->key, cfx->dek->keylen );*/
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cipher_setkey( cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen );
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cipher_setiv( cfx->cipher_hd, NULL, 0 );
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/* log_hexdump( "prefix", temp, nprefix+2 ); */
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if( cfx->mdc_hash ) /* hash the "IV" */
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md_write( cfx->mdc_hash, temp, nprefix+2 );
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cipher_encrypt( cfx->cipher_hd, temp, temp, nprefix+2);
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cipher_sync( cfx->cipher_hd );
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iobuf_write(a, temp, nprefix+2);
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cfx->header=1;
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}
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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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*/
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int
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cipher_filter( void *opaque, int control,
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IOBUF a, byte *buf, size_t *ret_len)
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{
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size_t size = *ret_len;
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cipher_filter_context_t *cfx = opaque;
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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);
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if( !cfx->header ) {
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write_header( cfx, a );
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}
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if( cfx->mdc_hash )
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md_write( cfx->mdc_hash, buf, size );
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cipher_encrypt( cfx->cipher_hd, buf, buf, size);
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if( iobuf_write( a, buf, size ) )
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rc = G10ERR_WRITE_FILE;
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}
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else if( control == IOBUFCTRL_FREE ) {
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if( cfx->mdc_hash ) {
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byte *hash;
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int hashlen = md_digest_length( md_get_algo( cfx->mdc_hash ) );
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byte temp[22];
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assert( hashlen == 20 );
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/* we must hash the prefix of the MDC packet here */
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temp[0] = 0xd3;
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temp[1] = 0x14;
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md_putc( cfx->mdc_hash, temp[0] );
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md_putc( cfx->mdc_hash, temp[1] );
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md_final( cfx->mdc_hash );
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hash = md_read( cfx->mdc_hash, 0 );
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memcpy(temp+2, hash, 20);
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cipher_encrypt( cfx->cipher_hd, temp, temp, 22 );
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md_close( cfx->mdc_hash ); cfx->mdc_hash = NULL;
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if( iobuf_write( a, temp, 22 ) )
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log_error("writing MDC packet failed\n" );
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}
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cipher_close(cfx->cipher_hd);
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}
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else if( control == IOBUFCTRL_DESC ) {
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*(char**)buf = "cipher_filter";
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}
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return rc;
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}
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