g10/cipher.c

   1 /* cipher.c - En-/De-ciphering filter
   2  * Copyright (C) 1998, 1999, 2000, 2001, 2003,
   3  *               2006 Free Software Foundation, Inc.
   4  *
   5  * This file is part of GnuPG.
   6  *
   7  * GnuPG is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * GnuPG is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  20  * USA.
  21  */
  22
  23 #include <config.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <errno.h>
  28 #include <assert.h>
  29
  30 #include "gpg.h"
  31 #include "errors.h"
  32 #include "iobuf.h"
  33 #include "util.h"
  34 #include "filter.h"
  35 #include "packet.h"
  36 #include "options.h"
  37 #include "main.h"
  38 #include "status.h"
  39
  40
  41 #define MIN_PARTIAL_SIZE 512
  42
  43
  44 static void
  45 write_header( cipher_filter_context_t *cfx, IOBUF a )
  46 {
  47     gcry_error_t err;
  48     PACKET pkt;
  49     PKT_encrypted ed;
  50     byte temp[18];
  51     unsigned int blocksize;
  52     unsigned int nprefix;
  53
  54     blocksize = gcry_cipher_get_algo_blklen (cfx->dek->algo);
  55     if ( blocksize < 8 || blocksize > 16 )
  56         log_fatal("unsupported blocksize %u\n", blocksize );
  57
  58     memset( &ed, 0, sizeof ed );
  59     ed.len = cfx->datalen;
  60     ed.extralen = blocksize+2;
  61     ed.new_ctb = !ed.len && !RFC1991;
  62     if( cfx->dek->use_mdc ) {
  63         ed.mdc_method = DIGEST_ALGO_SHA1;
  64         gcry_md_open (&cfx->mdc_hash, DIGEST_ALGO_SHA1, 0);
  65         if ( DBG_HASHING )
  66             gcry_md_start_debug (cfx->mdc_hash, "creatmdc");
  67     }
  68
  69     {
  70         char buf[20];
  71
  72         sprintf (buf, "%d %d", ed.mdc_method, cfx->dek->algo);
  73         write_status_text (STATUS_BEGIN_ENCRYPTION, buf);
  74     }
  75
  76     init_packet( &pkt );
  77     pkt.pkttype = cfx->dek->use_mdc? PKT_ENCRYPTED_MDC : PKT_ENCRYPTED;
  78     pkt.pkt.encrypted = &ed;
  79     if( build_packet( a, &pkt ))
  80         log_bug("build_packet(ENCR_DATA) failed\n");
  81     nprefix = blocksize;
  82     gcry_randomize (temp, nprefix, GCRY_STRONG_RANDOM );
  83     temp[nprefix] = temp[nprefix-2];
  84     temp[nprefix+1] = temp[nprefix-1];
  85     print_cipher_algo_note( cfx->dek->algo );
  86     err = gcry_cipher_open (&cfx->cipher_hd,
  87                             cfx->dek->algo,
  88                             GCRY_CIPHER_MODE_CFB,
  89                             (GCRY_CIPHER_SECURE
  90                              | ((cfx->dek->use_mdc || cfx->dek->algo >= 100)?
  91                                 0 : GCRY_CIPHER_ENABLE_SYNC)));
  92     if (err) {
  93         /* We should never get an error here cause we already checked,
  94          * that the algorithm is available.  */
  95         BUG();
  96     }
  97
  98
  99 /*   log_hexdump( "thekey", cfx->dek->key, cfx->dek->keylen );*/
 100     gcry_cipher_setkey( cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen );
 101     gcry_cipher_setiv( cfx->cipher_hd, NULL, 0 );
 102 /*  log_hexdump( "prefix", temp, nprefix+2 ); */
 103     if (cfx->mdc_hash) /* Hash the "IV". */
 104         gcry_md_write (cfx->mdc_hash, temp, nprefix+2 );
 105     gcry_cipher_encrypt (cfx->cipher_hd, temp, nprefix+2, NULL, 0);
 106     gcry_cipher_sync (cfx->cipher_hd);
 107     iobuf_write(a, temp, nprefix+2);
 108     cfx->header=1;
 109 }
 110
 111
 112
 113 /****************
 114  * This filter is used to en/de-cipher data with a conventional algorithm
 115  */
 116 int
 117 cipher_filter( void *opaque, int control,
 118                IOBUF a, byte *buf, size_t *ret_len)
 119 {
 120     size_t size = *ret_len;
 121     cipher_filter_context_t *cfx = opaque;
 122     int rc=0;
 123
 124     if( control == IOBUFCTRL_UNDERFLOW ) { /* decrypt */
 125         rc = -1; /* not yet used */
 126     }
 127     else if( control == IOBUFCTRL_FLUSH ) { /* encrypt */
 128         assert(a);
 129         if( !cfx->header ) {
 130             write_header( cfx, a );
 131         }
 132         if (cfx->mdc_hash)
 133             gcry_md_write (cfx->mdc_hash, buf, size);
 134         gcry_cipher_encrypt (cfx->cipher_hd, buf, size, NULL, 0);
 135         rc = iobuf_write( a, buf, size );
 136     }
 137     else if( control == IOBUFCTRL_FREE ) {
 138         if( cfx->mdc_hash ) {
 139             byte *hash;
 140             int hashlen = gcry_md_get_algo_dlen (gcry_md_get_algo
 141                                                  (cfx->mdc_hash));
 142             byte temp[22];
 143
 144             assert( hashlen == 20 );
 145             /* We must hash the prefix of the MDC packet here. */
 146             temp[0] = 0xd3;
 147             temp[1] = 0x14;
 148             gcry_md_putc (cfx->mdc_hash, temp[0]);
 149             gcry_md_putc (cfx->mdc_hash, temp[1]);
 150
 151             gcry_md_final (cfx->mdc_hash);
 152             hash = gcry_md_read (cfx->mdc_hash, 0);
 153             memcpy(temp+2, hash, 20);
 154             gcry_cipher_encrypt (cfx->cipher_hd, temp, 22, NULL, 0);
 155             gcry_md_close (cfx->mdc_hash); cfx->mdc_hash = NULL;
 156             if( iobuf_write( a, temp, 22 ) )
 157                 log_error("writing MDC packet failed\n" );
 158         }
 159         gcry_cipher_close (cfx->cipher_hd);
 160     }
 161     else if( control == IOBUFCTRL_DESC ) {
 162         *(char**)buf = "cipher_filter";
 163     }
 164     return rc;
 165 }