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/* cipher.c - En-/De-ciphering filter
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* Copyright (C) 1998, 1999, 2000, 2001, 2003 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
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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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* 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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* 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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#define MIN_PARTIAL_SIZE 512
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write_header( cipher_filter_context_t *cfx, iobuf_t a )
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unsigned int blocksize;
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blocksize = gcry_cipher_get_algo_blklen ( 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 && !RFC1991;
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if( cfx->dek->use_mdc ) {
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ed.mdc_method = DIGEST_ALGO_SHA1;
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gcry_md_open (&cfx->mdc_hash, GCRY_MD_SHA1, 0 );
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gcry_md_start_debug ( cfx->mdc_hash, "creatmdc" );
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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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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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gcry_randomize ( temp, nprefix, GCRY_STRONG_RANDOM);
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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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rc = gcry_cipher_open (&cfx->cipher_hd, cfx->dek->algo,
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| ((cfx->dek->use_mdc || cfx->dek->algo >= 100) ?
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0 : GCRY_CIPHER_ENABLE_SYNC));
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/* we should never get an error here cause we already checked, that
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* the algorithm is available. */
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/* log_hexdump( "thekey", cfx->dek->key, cfx->dek->keylen );*/
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gcry_cipher_setkey( cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen );
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gcry_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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gcry_md_write( cfx->mdc_hash, temp, nprefix+2 );
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gcry_cipher_encrypt( cfx->cipher_hd, temp, nprefix+2, NULL, 0);
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gcry_cipher_sync( cfx->cipher_hd );
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iobuf_write(a, temp, nprefix+2);
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* This filter is used to en/de-cipher data with a conventional algorithm
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cipher_filter( void *opaque, int control,
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iobuf_t a, byte *buf, size_t *ret_len)
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size_t size = *ret_len;
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cipher_filter_context_t *cfx = opaque;
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if( control == IOBUFCTRL_UNDERFLOW ) { /* decrypt */
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rc = -1; /* not yet used */
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else if( control == IOBUFCTRL_FLUSH ) { /* encrypt */
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write_header( cfx, a );
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gcry_md_write( cfx->mdc_hash, buf, size );
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gcry_cipher_encrypt( cfx->cipher_hd, buf, size, NULL, 0);
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rc = iobuf_write( a, buf, size );
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else if( control == IOBUFCTRL_FREE ) {
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if( cfx->mdc_hash ) {
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int hashlen = gcry_md_get_algo_dlen (gcry_md_get_algo (
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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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gcry_md_putc ( cfx->mdc_hash, temp[0] );
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gcry_md_putc ( cfx->mdc_hash, temp[1] );
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gcry_md_final ( cfx->mdc_hash );
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hash = gcry_md_read ( cfx->mdc_hash, 0 );
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memcpy(temp+2, hash, 20);
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gcry_cipher_encrypt( cfx->cipher_hd, temp, 22, NULL, 0 );
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gcry_md_close ( cfx->mdc_hash ); cfx->mdc_hash = NULL;
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rc = iobuf_write( a, temp, 22 );
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log_error("writing MDC packet failed\n" );
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gcry_cipher_close (cfx->cipher_hd);
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else if( control == IOBUFCTRL_DESC ) {
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*(char**)buf = "cipher_filter";