Line data Source code
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 <https://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 :
27 : #include "gpg.h"
28 : #include "status.h"
29 : #include "iobuf.h"
30 : #include "util.h"
31 : #include "filter.h"
32 : #include "packet.h"
33 : #include "options.h"
34 : #include "main.h"
35 : #include "status.h"
36 :
37 :
38 : #define MIN_PARTIAL_SIZE 512
39 :
40 :
41 : static void
42 302 : write_header( cipher_filter_context_t *cfx, IOBUF a )
43 : {
44 : gcry_error_t err;
45 : PACKET pkt;
46 : PKT_encrypted ed;
47 : byte temp[18];
48 : unsigned int blocksize;
49 : unsigned int nprefix;
50 :
51 302 : blocksize = openpgp_cipher_get_algo_blklen (cfx->dek->algo);
52 302 : if ( blocksize < 8 || blocksize > 16 )
53 0 : log_fatal("unsupported blocksize %u\n", blocksize );
54 :
55 302 : memset( &ed, 0, sizeof ed );
56 302 : ed.len = cfx->datalen;
57 302 : ed.extralen = blocksize+2;
58 302 : ed.new_ctb = !ed.len;
59 302 : if( cfx->dek->use_mdc ) {
60 244 : ed.mdc_method = DIGEST_ALGO_SHA1;
61 244 : gcry_md_open (&cfx->mdc_hash, DIGEST_ALGO_SHA1, 0);
62 244 : if ( DBG_HASHING )
63 0 : gcry_md_debug (cfx->mdc_hash, "creatmdc");
64 : }
65 :
66 : {
67 : char buf[20];
68 :
69 302 : sprintf (buf, "%d %d", ed.mdc_method, cfx->dek->algo);
70 302 : write_status_text (STATUS_BEGIN_ENCRYPTION, buf);
71 : }
72 :
73 302 : init_packet( &pkt );
74 302 : pkt.pkttype = cfx->dek->use_mdc? PKT_ENCRYPTED_MDC : PKT_ENCRYPTED;
75 302 : pkt.pkt.encrypted = &ed;
76 302 : if( build_packet( a, &pkt ))
77 0 : log_bug("build_packet(ENCR_DATA) failed\n");
78 302 : nprefix = blocksize;
79 302 : gcry_randomize (temp, nprefix, GCRY_STRONG_RANDOM );
80 302 : temp[nprefix] = temp[nprefix-2];
81 302 : temp[nprefix+1] = temp[nprefix-1];
82 302 : print_cipher_algo_note( cfx->dek->algo );
83 302 : err = openpgp_cipher_open (&cfx->cipher_hd,
84 : cfx->dek->algo,
85 : GCRY_CIPHER_MODE_CFB,
86 : (GCRY_CIPHER_SECURE
87 : | ((cfx->dek->use_mdc || cfx->dek->algo >= 100)?
88 : 0 : GCRY_CIPHER_ENABLE_SYNC)));
89 302 : if (err) {
90 : /* We should never get an error here cause we already checked,
91 : * that the algorithm is available. */
92 0 : BUG();
93 : }
94 :
95 :
96 : /* log_hexdump( "thekey", cfx->dek->key, cfx->dek->keylen );*/
97 302 : gcry_cipher_setkey( cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen );
98 302 : gcry_cipher_setiv( cfx->cipher_hd, NULL, 0 );
99 : /* log_hexdump( "prefix", temp, nprefix+2 ); */
100 302 : if (cfx->mdc_hash) /* Hash the "IV". */
101 244 : gcry_md_write (cfx->mdc_hash, temp, nprefix+2 );
102 302 : gcry_cipher_encrypt (cfx->cipher_hd, temp, nprefix+2, NULL, 0);
103 302 : gcry_cipher_sync (cfx->cipher_hd);
104 302 : iobuf_write(a, temp, nprefix+2);
105 302 : cfx->header=1;
106 302 : }
107 :
108 :
109 :
110 : /****************
111 : * This filter is used to en/de-cipher data with a conventional algorithm
112 : */
113 : int
114 1898 : cipher_filter( void *opaque, int control,
115 : IOBUF a, byte *buf, size_t *ret_len)
116 : {
117 1898 : size_t size = *ret_len;
118 1898 : cipher_filter_context_t *cfx = opaque;
119 1898 : int rc=0;
120 :
121 1898 : if( control == IOBUFCTRL_UNDERFLOW ) { /* decrypt */
122 0 : rc = -1; /* not yet used */
123 : }
124 1898 : else if( control == IOBUFCTRL_FLUSH ) { /* encrypt */
125 1294 : log_assert(a);
126 1294 : if( !cfx->header ) {
127 302 : write_header( cfx, a );
128 : }
129 1294 : if (cfx->mdc_hash)
130 1058 : gcry_md_write (cfx->mdc_hash, buf, size);
131 1294 : gcry_cipher_encrypt (cfx->cipher_hd, buf, size, NULL, 0);
132 1294 : rc = iobuf_write( a, buf, size );
133 : }
134 604 : else if( control == IOBUFCTRL_FREE ) {
135 302 : if( cfx->mdc_hash ) {
136 : byte *hash;
137 244 : int hashlen = gcry_md_get_algo_dlen (gcry_md_get_algo
138 : (cfx->mdc_hash));
139 : byte temp[22];
140 :
141 244 : log_assert( hashlen == 20 );
142 : /* We must hash the prefix of the MDC packet here. */
143 244 : temp[0] = 0xd3;
144 244 : temp[1] = 0x14;
145 244 : gcry_md_putc (cfx->mdc_hash, temp[0]);
146 244 : gcry_md_putc (cfx->mdc_hash, temp[1]);
147 :
148 244 : gcry_md_final (cfx->mdc_hash);
149 244 : hash = gcry_md_read (cfx->mdc_hash, 0);
150 244 : memcpy(temp+2, hash, 20);
151 244 : gcry_cipher_encrypt (cfx->cipher_hd, temp, 22, NULL, 0);
152 244 : gcry_md_close (cfx->mdc_hash); cfx->mdc_hash = NULL;
153 244 : if( iobuf_write( a, temp, 22 ) )
154 0 : log_error("writing MDC packet failed\n" );
155 : }
156 302 : gcry_cipher_close (cfx->cipher_hd);
157 : }
158 302 : else if( control == IOBUFCTRL_DESC ) {
159 0 : mem2str (buf, "cipher_filter", *ret_len);
160 : }
161 1898 : return rc;
162 : }
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