crypto/des/ofb_enc.c

   1 /*
   2  * Copyright 1995-2020 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 /*
  11  * DES low level APIs are deprecated for public use, but still ok for internal
  12  * use.
  13  */
  14 #include "internal/deprecated.h"
  15
  16 #include "des_local.h"
  17
  18 /*
  19  * The input and output are loaded in multiples of 8 bits. What this means is
  20  * that if you have numbits=12 and length=2 the first 12 bits will be
  21  * retrieved from the first byte and half the second.  The second 12 bits
  22  * will come from the 3rd and half the 4th byte.
  23  */
  24 void DES_ofb_encrypt(const unsigned char *in, unsigned char *out, int numbits,
  25                      long length, DES_key_schedule *schedule,
  26                      DES_cblock *ivec)
  27 {
  28     register DES_LONG d0, d1, vv0, vv1, v0, v1, n = (numbits + 7) / 8;
  29     register DES_LONG mask0, mask1;
  30     register long l = length;
  31     register int num = numbits;
  32     DES_LONG ti[2];
  33     unsigned char *iv;
  34
  35     if (num > 64)
  36         return;
  37     if (num > 32) {
  38         mask0 = 0xffffffffL;
  39         if (num >= 64)
  40             mask1 = mask0;
  41         else
  42             mask1 = (1L << (num - 32)) - 1;
  43     } else {
  44         if (num == 32)
  45             mask0 = 0xffffffffL;
  46         else
  47             mask0 = (1L << num) - 1;
  48         mask1 = 0x00000000L;
  49     }
  50
  51     iv = &(*ivec)[0];
  52     c2l(iv, v0);
  53     c2l(iv, v1);
  54     ti[0] = v0;
  55     ti[1] = v1;
  56     while (l-- > 0) {
  57         ti[0] = v0;
  58         ti[1] = v1;
  59         DES_encrypt1((DES_LONG *)ti, schedule, DES_ENCRYPT);
  60         vv0 = ti[0];
  61         vv1 = ti[1];
  62         c2ln(in, d0, d1, n);
  63         in += n;
  64         d0 = (d0 ^ vv0) & mask0;
  65         d1 = (d1 ^ vv1) & mask1;
  66         l2cn(d0, d1, out, n);
  67         out += n;
  68
  69         if (num == 32) {
  70             v0 = v1;
  71             v1 = vv0;
  72         } else if (num == 64) {
  73             v0 = vv0;
  74             v1 = vv1;
  75         } else if (num > 32) {  /* && num != 64 */
  76             v0 = ((v1 >> (num - 32)) | (vv0 << (64 - num))) & 0xffffffffL;
  77             v1 = ((vv0 >> (num - 32)) | (vv1 << (64 - num))) & 0xffffffffL;
  78         } else {                /* num < 32 */
  79
  80             v0 = ((v0 >> num) | (v1 << (32 - num))) & 0xffffffffL;
  81             v1 = ((v1 >> num) | (vv0 << (32 - num))) & 0xffffffffL;
  82         }
  83     }
  84     iv = &(*ivec)[0];
  85     l2c(v0, iv);
  86     l2c(v1, iv);
  87     v0 = v1 = d0 = d1 = ti[0] = ti[1] = vv0 = vv1 = 0;
  88 }