1/*
2 * Copyright 2008-2020 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the OpenSSL license (the "License").  You may not use
5 * this file except in compliance with the License.  You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#include <openssl/crypto.h>
11#include "modes_local.h"
12#include <string.h>
13
14#if defined(__GNUC__) && !defined(STRICT_ALIGNMENT)
15typedef size_t size_t_aX __attribute((__aligned__(1)));
16#else
17typedef size_t size_t_aX;
18#endif
19
20/*
21 * The input and output encrypted as though 128bit ofb mode is being used.
22 * The extra state information to record how much of the 128bit block we have
23 * used is contained in *num;
24 */
25void CRYPTO_ofb128_encrypt(const unsigned char *in, unsigned char *out,
26                           size_t len, const void *key,
27                           unsigned char ivec[16], int *num, block128_f block)
28{
29    unsigned int n;
30    size_t l = 0;
31
32    n = *num;
33
34#if !defined(OPENSSL_SMALL_FOOTPRINT)
35    if (16 % sizeof(size_t) == 0) { /* always true actually */
36        do {
37            while (n && len) {
38                *(out++) = *(in++) ^ ivec[n];
39                --len;
40                n = (n + 1) % 16;
41            }
42# if defined(STRICT_ALIGNMENT)
43            if (((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) !=
44                0)
45                break;
46# endif
47            while (len >= 16) {
48                (*block) (ivec, ivec, key);
49                for (; n < 16; n += sizeof(size_t))
50                    *(size_t_aX *)(out + n) =
51                        *(size_t_aX *)(in + n)
52                        ^ *(size_t_aX *)(ivec + n);
53                len -= 16;
54                out += 16;
55                in += 16;
56                n = 0;
57            }
58            if (len) {
59                (*block) (ivec, ivec, key);
60                while (len--) {
61                    out[n] = in[n] ^ ivec[n];
62                    ++n;
63                }
64            }
65            *num = n;
66            return;
67        } while (0);
68    }
69    /* the rest would be commonly eliminated by x86* compiler */
70#endif
71    while (l < len) {
72        if (n == 0) {
73            (*block) (ivec, ivec, key);
74        }
75        out[l] = in[l] ^ ivec[n];
76        ++l;
77        n = (n + 1) % 16;
78    }
79
80    *num = n;
81}
82