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Diffstat (limited to 'g10/cipher.c')
| -rw-r--r-- | g10/cipher.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/g10/cipher.c b/g10/cipher.c new file mode 100644 index 0000000..f7332ba --- /dev/null +++ b/g10/cipher.c @@ -0,0 +1,153 @@ +/* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, + * 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 && !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; +} |