1/*
2 * Copyright 2008-2021 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (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 <string.h>
11#include <openssl/crypto.h>
12#include "crypto/modes.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    if (*num < 0) {
33        /* There is no good way to signal an error return from here */
34        *num = -1;
35        return;
36    }
37    n = *num;
38
39#if !defined(OPENSSL_SMALL_FOOTPRINT)
40    if (16 % sizeof(size_t) == 0) { /* always true actually */
41        do {
42            while (n && len) {
43                *(out++) = *(in++) ^ ivec[n];
44                --len;
45                n = (n + 1) % 16;
46            }
47# if defined(STRICT_ALIGNMENT)
48            if (((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) !=
49                0)
50                break;
51# endif
52            while (len >= 16) {
53                (*block) (ivec, ivec, key);
54                for (; n < 16; n += sizeof(size_t))
55                    *(size_t_aX *)(out + n) =
56                        *(size_t_aX *)(in + n)
57                        ^ *(size_t_aX *)(ivec + n);
58                len -= 16;
59                out += 16;
60                in += 16;
61                n = 0;
62            }
63            if (len) {
64                (*block) (ivec, ivec, key);
65                while (len--) {
66                    out[n] = in[n] ^ ivec[n];
67                    ++n;
68                }
69            }
70            *num = n;
71            return;
72        } while (0);
73    }
74    /* the rest would be commonly eliminated by x86* compiler */
75#endif
76    while (l < len) {
77        if (n == 0) {
78            (*block) (ivec, ivec, key);
79        }
80        out[l] = in[l] ^ ivec[n];
81        ++l;
82        n = (n + 1) % 16;
83    }
84
85    *num = n;
86}
87