cfb128.c revision 296341 
1/* ====================================================================
2 * Copyright (c) 2008 The OpenSSL Project.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in
13 *    the documentation and/or other materials provided with the
14 *    distribution.
15 *
16 * 3. All advertising materials mentioning features or use of this
17 *    software must display the following acknowledgment:
18 *    "This product includes software developed by the OpenSSL Project
19 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
20 *
21 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
22 *    endorse or promote products derived from this software without
23 *    prior written permission. For written permission, please contact
24 *    openssl-core@openssl.org.
25 *
26 * 5. Products derived from this software may not be called "OpenSSL"
27 *    nor may "OpenSSL" appear in their names without prior written
28 *    permission of the OpenSSL Project.
29 *
30 * 6. Redistributions of any form whatsoever must retain the following
31 *    acknowledgment:
32 *    "This product includes software developed by the OpenSSL Project
33 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
34 *
35 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
36 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
38 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
39 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
40 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
41 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
42 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
43 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
44 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
45 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
46 * OF THE POSSIBILITY OF SUCH DAMAGE.
47 * ====================================================================
48 *
49 */
50
51#include <openssl/crypto.h>
52#include "modes_lcl.h"
53#include <string.h>
54
55#ifndef MODES_DEBUG
56# ifndef NDEBUG
57#  define NDEBUG
58# endif
59#endif
60#include <assert.h>
61
62/*
63 * The input and output encrypted as though 128bit cfb mode is being used.
64 * The extra state information to record how much of the 128bit block we have
65 * used is contained in *num;
66 */
67void CRYPTO_cfb128_encrypt(const unsigned char *in, unsigned char *out,
68                           size_t len, const void *key,
69                           unsigned char ivec[16], int *num,
70                           int enc, block128_f block)
71{
72    unsigned int n;
73    size_t l = 0;
74
75    assert(in && out && key && ivec && num);
76
77    n = *num;
78
79    if (enc) {
80#if !defined(OPENSSL_SMALL_FOOTPRINT)
81        if (16 % sizeof(size_t) == 0) { /* always true actually */
82            do {
83                while (n && len) {
84                    *(out++) = ivec[n] ^= *(in++);
85                    --len;
86                    n = (n + 1) % 16;
87                }
88# if defined(STRICT_ALIGNMENT)
89                if (((size_t)in | (size_t)out | (size_t)ivec) %
90                    sizeof(size_t) != 0)
91                    break;
92# endif
93                while (len >= 16) {
94                    (*block) (ivec, ivec, key);
95                    for (; n < 16; n += sizeof(size_t)) {
96                        *(size_t *)(out + n) =
97                            *(size_t *)(ivec + n) ^= *(size_t *)(in + n);
98                    }
99                    len -= 16;
100                    out += 16;
101                    in += 16;
102                    n = 0;
103                }
104                if (len) {
105                    (*block) (ivec, ivec, key);
106                    while (len--) {
107                        out[n] = ivec[n] ^= in[n];
108                        ++n;
109                    }
110                }
111                *num = n;
112                return;
113            } while (0);
114        }
115        /* the rest would be commonly eliminated by x86* compiler */
116#endif
117        while (l < len) {
118            if (n == 0) {
119                (*block) (ivec, ivec, key);
120            }
121            out[l] = ivec[n] ^= in[l];
122            ++l;
123            n = (n + 1) % 16;
124        }
125        *num = n;
126    } else {
127#if !defined(OPENSSL_SMALL_FOOTPRINT)
128        if (16 % sizeof(size_t) == 0) { /* always true actually */
129            do {
130                while (n && len) {
131                    unsigned char c;
132                    *(out++) = ivec[n] ^ (c = *(in++));
133                    ivec[n] = c;
134                    --len;
135                    n = (n + 1) % 16;
136                }
137# if defined(STRICT_ALIGNMENT)
138                if (((size_t)in | (size_t)out | (size_t)ivec) %
139                    sizeof(size_t) != 0)
140                    break;
141# endif
142                while (len >= 16) {
143                    (*block) (ivec, ivec, key);
144                    for (; n < 16; n += sizeof(size_t)) {
145                        size_t t = *(size_t *)(in + n);
146                        *(size_t *)(out + n) = *(size_t *)(ivec + n) ^ t;
147                        *(size_t *)(ivec + n) = t;
148                    }
149                    len -= 16;
150                    out += 16;
151                    in += 16;
152                    n = 0;
153                }
154                if (len) {
155                    (*block) (ivec, ivec, key);
156                    while (len--) {
157                        unsigned char c;
158                        out[n] = ivec[n] ^ (c = in[n]);
159                        ivec[n] = c;
160                        ++n;
161                    }
162                }
163                *num = n;
164                return;
165            } while (0);
166        }
167        /* the rest would be commonly eliminated by x86* compiler */
168#endif
169        while (l < len) {
170            unsigned char c;
171            if (n == 0) {
172                (*block) (ivec, ivec, key);
173            }
174            out[l] = ivec[n] ^ (c = in[l]);
175            ivec[n] = c;
176            ++l;
177            n = (n + 1) % 16;
178        }
179        *num = n;
180    }
181}
182
183/*
184 * This expects a single block of size nbits for both in and out. Note that
185 * it corrupts any extra bits in the last byte of out
186 */
187static void cfbr_encrypt_block(const unsigned char *in, unsigned char *out,
188                               int nbits, const void *key,
189                               unsigned char ivec[16], int enc,
190                               block128_f block)
191{
192    int n, rem, num;
193    unsigned char ovec[16 * 2 + 1]; /* +1 because we dererefence (but don't
194                                     * use) one byte off the end */
195
196    if (nbits <= 0 || nbits > 128)
197        return;
198
199    /* fill in the first half of the new IV with the current IV */
200    memcpy(ovec, ivec, 16);
201    /* construct the new IV */
202    (*block) (ivec, ivec, key);
203    num = (nbits + 7) / 8;
204    if (enc)                    /* encrypt the input */
205        for (n = 0; n < num; ++n)
206            out[n] = (ovec[16 + n] = in[n] ^ ivec[n]);
207    else                        /* decrypt the input */
208        for (n = 0; n < num; ++n)
209            out[n] = (ovec[16 + n] = in[n]) ^ ivec[n];
210    /* shift ovec left... */
211    rem = nbits % 8;
212    num = nbits / 8;
213    if (rem == 0)
214        memcpy(ivec, ovec + num, 16);
215    else
216        for (n = 0; n < 16; ++n)
217            ivec[n] = ovec[n + num] << rem | ovec[n + num + 1] >> (8 - rem);
218
219    /* it is not necessary to cleanse ovec, since the IV is not secret */
220}
221
222/* N.B. This expects the input to be packed, MS bit first */
223void CRYPTO_cfb128_1_encrypt(const unsigned char *in, unsigned char *out,
224                             size_t bits, const void *key,
225                             unsigned char ivec[16], int *num,
226                             int enc, block128_f block)
227{
228    size_t n;
229    unsigned char c[1], d[1];
230
231    assert(in && out && key && ivec && num);
232    assert(*num == 0);
233
234    for (n = 0; n < bits; ++n) {
235        c[0] = (in[n / 8] & (1 << (7 - n % 8))) ? 0x80 : 0;
236        cfbr_encrypt_block(c, d, 1, key, ivec, enc, block);
237        out[n / 8] = (out[n / 8] & ~(1 << (unsigned int)(7 - n % 8))) |
238            ((d[0] & 0x80) >> (unsigned int)(n % 8));
239    }
240}
241
242void CRYPTO_cfb128_8_encrypt(const unsigned char *in, unsigned char *out,
243                             size_t length, const void *key,
244                             unsigned char ivec[16], int *num,
245                             int enc, block128_f block)
246{
247    size_t n;
248
249    assert(in && out && key && ivec && num);
250    assert(*num == 0);
251
252    for (n = 0; n < length; ++n)
253        cfbr_encrypt_block(&in[n], &out[n], 8, key, ivec, enc, block);
254}
255