crypto/modes/ofb128.c

   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 }