g10/cipher.c

   1 /* cipher.c - En-/De-ciphering filter
   2  * Copyright (C) 1998, 1999, 2000, 2001, 2003,
   3  *               2006, 2009 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 3 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, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <config.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <errno.h>
  26 #include <assert.h>
  27
  28 #include "gpg.h"
  29 #include "status.h"
  30 #include "iobuf.h"
  31 #include "util.h"
  32 #include "filter.h"
  33 #include "packet.h"
  34 #include "options.h"
  35 #include "main.h"
  36 #include "status.h"
  37
  38
  39 #define MIN_PARTIAL_SIZE 512
  40
  41
  42 static void
  43 write_header( cipher_filter_context_t *cfx, IOBUF a )
  44 {
  45     gcry_error_t err;
  46     PACKET pkt;
  47     PKT_encrypted ed;
  48     byte temp[18];
  49     unsigned int blocksize;
  50     unsigned int nprefix;
  51
  52     blocksize = openpgp_cipher_get_algo_blklen (cfx->dek->algo);
  53     if ( blocksize < 8 || blocksize > 16 )
  54         log_fatal("unsupported blocksize %u\n", blocksize );
  55
  56     memset( &ed, 0, sizeof ed );
  57     ed.len = cfx->datalen;
  58     ed.extralen = blocksize+2;
  59     ed.new_ctb = !ed.len && !RFC1991;
  60     if( cfx->dek->use_mdc ) {
  61         ed.mdc_method = DIGEST_ALGO_SHA1;
  62         gcry_md_open (&cfx->mdc_hash, DIGEST_ALGO_SHA1, 0);
  63         if ( DBG_HASHING )
  64             gcry_md_start_debug (cfx->mdc_hash, "creatmdc");
  65     }
  66
  67     {
  68         char buf[20];
  69
  70         sprintf (buf, "%d %d", ed.mdc_method, cfx->dek->algo);
  71         write_status_text (STATUS_BEGIN_ENCRYPTION, buf);
  72     }
  73
  74     init_packet( &pkt );
  75     pkt.pkttype = cfx->dek->use_mdc? PKT_ENCRYPTED_MDC : PKT_ENCRYPTED;
  76     pkt.pkt.encrypted = &ed;
  77     if( build_packet( a, &pkt ))
  78         log_bug("build_packet(ENCR_DATA) failed\n");
  79     nprefix = blocksize;
  80     gcry_randomize (temp, nprefix, GCRY_STRONG_RANDOM );
  81     temp[nprefix] = temp[nprefix-2];
  82     temp[nprefix+1] = temp[nprefix-1];
  83     print_cipher_algo_note( cfx->dek->algo );
  84     err = openpgp_cipher_open (&cfx->cipher_hd,
  85                                cfx->dek->algo,
  86                                GCRY_CIPHER_MODE_CFB,
  87                                (GCRY_CIPHER_SECURE
  88                                 | ((cfx->dek->use_mdc || cfx->dek->algo >= 100)?
  89                                    0 : GCRY_CIPHER_ENABLE_SYNC)));
  90     if (err) {
  91         /* We should never get an error here cause we already checked,
  92          * that the algorithm is available.  */
  93         BUG();
  94     }
  95
  96
  97 /*   log_hexdump( "thekey", cfx->dek->key, cfx->dek->keylen );*/
  98     gcry_cipher_setkey( cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen );
  99     gcry_cipher_setiv( cfx->cipher_hd, NULL, 0 );
 100 /*  log_hexdump( "prefix", temp, nprefix+2 ); */
 101     if (cfx->mdc_hash) /* Hash the "IV". */
 102         gcry_md_write (cfx->mdc_hash, temp, nprefix+2 );
 103     gcry_cipher_encrypt (cfx->cipher_hd, temp, nprefix+2, NULL, 0);
 104     gcry_cipher_sync (cfx->cipher_hd);
 105     iobuf_write(a, temp, nprefix+2);
 106     cfx->header=1;
 107 }
 108
 109
 110
 111 /****************
 112  * This filter is used to en/de-cipher data with a conventional algorithm
 113  */
 114 int
 115 cipher_filter( void *opaque, int control,
 116                IOBUF a, byte *buf, size_t *ret_len)
 117 {
 118     size_t size = *ret_len;
 119     cipher_filter_context_t *cfx = opaque;
 120     int rc=0;
 121
 122     if( control == IOBUFCTRL_UNDERFLOW ) { /* decrypt */
 123         rc = -1; /* not yet used */
 124     }
 125     else if( control == IOBUFCTRL_FLUSH ) { /* encrypt */
 126         assert(a);
 127         if( !cfx->header ) {
 128             write_header( cfx, a );
 129         }
 130         if (cfx->mdc_hash)
 131             gcry_md_write (cfx->mdc_hash, buf, size);
 132         gcry_cipher_encrypt (cfx->cipher_hd, buf, size, NULL, 0);
 133         rc = iobuf_write( a, buf, size );
 134     }
 135     else if( control == IOBUFCTRL_FREE ) {
 136         if( cfx->mdc_hash ) {
 137             byte *hash;
 138             int hashlen = gcry_md_get_algo_dlen (gcry_md_get_algo
 139                                                  (cfx->mdc_hash));
 140             byte temp[22];
 141
 142             assert( hashlen == 20 );
 143             /* We must hash the prefix of the MDC packet here. */
 144             temp[0] = 0xd3;
 145             temp[1] = 0x14;
 146             gcry_md_putc (cfx->mdc_hash, temp[0]);
 147             gcry_md_putc (cfx->mdc_hash, temp[1]);
 148
 149             gcry_md_final (cfx->mdc_hash);
 150             hash = gcry_md_read (cfx->mdc_hash, 0);
 151             memcpy(temp+2, hash, 20);
 152             gcry_cipher_encrypt (cfx->cipher_hd, temp, 22, NULL, 0);
 153             gcry_md_close (cfx->mdc_hash); cfx->mdc_hash = NULL;
 154             if( iobuf_write( a, temp, 22 ) )
 155                 log_error("writing MDC packet failed\n" );
 156         }
 157         gcry_cipher_close (cfx->cipher_hd);
 158     }
 159     else if( control == IOBUFCTRL_DESC ) {
 160         *(char**)buf = "cipher_filter";
 161     }
 162     return rc;
 163 }