xref: /openssl/crypto/des/ofb_enc.c (revision 33388b44)
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  */
DES_ofb_encrypt(const unsigned char * in,unsigned char * out,int numbits,long length,DES_key_schedule * schedule,DES_cblock * ivec)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 }
89