Line data Source code
1 : /* cipher-cbc.c - Generic CBC mode implementation
2 : * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003
3 : * 2005, 2007, 2008, 2009, 2011 Free Software Foundation, Inc.
4 : *
5 : * This file is part of Libgcrypt.
6 : *
7 : * Libgcrypt is free software; you can redistribute it and/or modify
8 : * it under the terms of the GNU Lesser general Public License as
9 : * published by the Free Software Foundation; either version 2.1 of
10 : * the License, or (at your option) any later version.
11 : *
12 : * Libgcrypt 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 Lesser General Public License for more details.
16 : *
17 : * You should have received a copy of the GNU Lesser General Public
18 : * License 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 :
27 : #include "g10lib.h"
28 : #include "cipher.h"
29 : #include "./cipher-internal.h"
30 : #include "bufhelp.h"
31 :
32 :
33 :
34 : gcry_err_code_t
35 0 : _gcry_cipher_cbc_encrypt (gcry_cipher_hd_t c,
36 : unsigned char *outbuf, size_t outbuflen,
37 : const unsigned char *inbuf, size_t inbuflen)
38 : {
39 : size_t n;
40 : unsigned char *ivp;
41 : int i;
42 0 : size_t blocksize = c->spec->blocksize;
43 0 : gcry_cipher_encrypt_t enc_fn = c->spec->encrypt;
44 0 : size_t nblocks = inbuflen / blocksize;
45 : unsigned int burn, nburn;
46 :
47 0 : if (outbuflen < ((c->flags & GCRY_CIPHER_CBC_MAC)? blocksize : inbuflen))
48 0 : return GPG_ERR_BUFFER_TOO_SHORT;
49 :
50 0 : if ((inbuflen % blocksize)
51 0 : && !(inbuflen > blocksize
52 0 : && (c->flags & GCRY_CIPHER_CBC_CTS)))
53 0 : return GPG_ERR_INV_LENGTH;
54 :
55 0 : burn = 0;
56 :
57 0 : if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
58 : {
59 0 : if ((inbuflen % blocksize) == 0)
60 0 : nblocks--;
61 : }
62 :
63 0 : if (c->bulk.cbc_enc)
64 : {
65 0 : c->bulk.cbc_enc (&c->context.c, c->u_iv.iv, outbuf, inbuf, nblocks,
66 0 : (c->flags & GCRY_CIPHER_CBC_MAC));
67 0 : inbuf += nblocks * blocksize;
68 0 : if (!(c->flags & GCRY_CIPHER_CBC_MAC))
69 0 : outbuf += nblocks * blocksize;
70 : }
71 : else
72 : {
73 0 : ivp = c->u_iv.iv;
74 :
75 0 : for (n=0; n < nblocks; n++ )
76 : {
77 0 : buf_xor (outbuf, inbuf, ivp, blocksize);
78 0 : nburn = enc_fn ( &c->context.c, outbuf, outbuf );
79 0 : burn = nburn > burn ? nburn : burn;
80 0 : ivp = outbuf;
81 0 : inbuf += blocksize;
82 0 : if (!(c->flags & GCRY_CIPHER_CBC_MAC))
83 0 : outbuf += blocksize;
84 : }
85 :
86 0 : if (ivp != c->u_iv.iv)
87 0 : buf_cpy (c->u_iv.iv, ivp, blocksize );
88 : }
89 :
90 0 : if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
91 : {
92 : /* We have to be careful here, since outbuf might be equal to
93 : inbuf. */
94 : size_t restbytes;
95 : unsigned char b;
96 :
97 0 : if ((inbuflen % blocksize) == 0)
98 0 : restbytes = blocksize;
99 : else
100 0 : restbytes = inbuflen % blocksize;
101 :
102 0 : outbuf -= blocksize;
103 0 : for (ivp = c->u_iv.iv, i = 0; i < restbytes; i++)
104 : {
105 0 : b = inbuf[i];
106 0 : outbuf[blocksize + i] = outbuf[i];
107 0 : outbuf[i] = b ^ *ivp++;
108 : }
109 0 : for (; i < blocksize; i++)
110 0 : outbuf[i] = 0 ^ *ivp++;
111 :
112 0 : nburn = enc_fn (&c->context.c, outbuf, outbuf);
113 0 : burn = nburn > burn ? nburn : burn;
114 0 : buf_cpy (c->u_iv.iv, outbuf, blocksize);
115 : }
116 :
117 0 : if (burn > 0)
118 0 : _gcry_burn_stack (burn + 4 * sizeof(void *));
119 :
120 0 : return 0;
121 : }
122 :
123 :
124 : gcry_err_code_t
125 0 : _gcry_cipher_cbc_decrypt (gcry_cipher_hd_t c,
126 : unsigned char *outbuf, size_t outbuflen,
127 : const unsigned char *inbuf, size_t inbuflen)
128 : {
129 : size_t n;
130 : int i;
131 0 : size_t blocksize = c->spec->blocksize;
132 0 : gcry_cipher_decrypt_t dec_fn = c->spec->decrypt;
133 0 : size_t nblocks = inbuflen / blocksize;
134 : unsigned int burn, nburn;
135 :
136 0 : if (outbuflen < inbuflen)
137 0 : return GPG_ERR_BUFFER_TOO_SHORT;
138 :
139 0 : if ((inbuflen % blocksize)
140 0 : && !(inbuflen > blocksize
141 0 : && (c->flags & GCRY_CIPHER_CBC_CTS)))
142 0 : return GPG_ERR_INV_LENGTH;
143 :
144 0 : burn = 0;
145 :
146 0 : if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
147 : {
148 0 : nblocks--;
149 0 : if ((inbuflen % blocksize) == 0)
150 0 : nblocks--;
151 0 : buf_cpy (c->lastiv, c->u_iv.iv, blocksize);
152 : }
153 :
154 0 : if (c->bulk.cbc_dec)
155 : {
156 0 : c->bulk.cbc_dec (&c->context.c, c->u_iv.iv, outbuf, inbuf, nblocks);
157 0 : inbuf += nblocks * blocksize;
158 0 : outbuf += nblocks * blocksize;
159 : }
160 : else
161 : {
162 0 : for (n=0; n < nblocks; n++ )
163 : {
164 : /* Because outbuf and inbuf might be the same, we must not overwrite
165 : the original ciphertext block. We use LASTIV as intermediate
166 : storage here because it is not used otherwise. */
167 0 : nburn = dec_fn ( &c->context.c, c->lastiv, inbuf );
168 0 : burn = nburn > burn ? nburn : burn;
169 0 : buf_xor_n_copy_2(outbuf, c->lastiv, c->u_iv.iv, inbuf, blocksize);
170 0 : inbuf += blocksize;
171 0 : outbuf += blocksize;
172 : }
173 : }
174 :
175 0 : if ((c->flags & GCRY_CIPHER_CBC_CTS) && inbuflen > blocksize)
176 : {
177 : size_t restbytes;
178 :
179 0 : if ((inbuflen % blocksize) == 0)
180 0 : restbytes = blocksize;
181 : else
182 0 : restbytes = inbuflen % blocksize;
183 :
184 0 : buf_cpy (c->lastiv, c->u_iv.iv, blocksize ); /* Save Cn-2. */
185 0 : buf_cpy (c->u_iv.iv, inbuf + blocksize, restbytes ); /* Save Cn. */
186 :
187 0 : nburn = dec_fn ( &c->context.c, outbuf, inbuf );
188 0 : burn = nburn > burn ? nburn : burn;
189 0 : buf_xor(outbuf, outbuf, c->u_iv.iv, restbytes);
190 :
191 0 : buf_cpy (outbuf + blocksize, outbuf, restbytes);
192 0 : for(i=restbytes; i < blocksize; i++)
193 0 : c->u_iv.iv[i] = outbuf[i];
194 0 : nburn = dec_fn (&c->context.c, outbuf, c->u_iv.iv);
195 0 : burn = nburn > burn ? nburn : burn;
196 0 : buf_xor(outbuf, outbuf, c->lastiv, blocksize);
197 : /* c->lastiv is now really lastlastiv, does this matter? */
198 : }
199 :
200 0 : if (burn > 0)
201 0 : _gcry_burn_stack (burn + 4 * sizeof(void *));
202 :
203 0 : return 0;
204 : }
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