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      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)
     15 typedef size_t size_t_aX __attribute((__aligned__(1)));
     16 #else
     17 typedef 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  */
     25 void 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