xref: /openssl/crypto/cast/c_cfb64.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  * CAST low level APIs are deprecated for public use, but still ok for
12  * internal use.
13  */
14 #include "internal/deprecated.h"
15 
16 #include <openssl/cast.h>
17 #include "cast_local.h"
18 
19 /*
20  * The input and output encrypted as though 64bit cfb mode is being used.
21  * The extra state information to record how much of the 64bit block we have
22  * used is contained in *num;
23  */
24 
CAST_cfb64_encrypt(const unsigned char * in,unsigned char * out,long length,const CAST_KEY * schedule,unsigned char * ivec,int * num,int enc)25 void CAST_cfb64_encrypt(const unsigned char *in, unsigned char *out,
26                         long length, const CAST_KEY *schedule,
27                         unsigned char *ivec, int *num, int enc)
28 {
29     register CAST_LONG v0, v1, t;
30     register int n = *num;
31     register long l = length;
32     CAST_LONG ti[2];
33     unsigned char *iv, c, cc;
34 
35     iv = ivec;
36     if (enc) {
37         while (l--) {
38             if (n == 0) {
39                 n2l(iv, v0);
40                 ti[0] = v0;
41                 n2l(iv, v1);
42                 ti[1] = v1;
43                 CAST_encrypt((CAST_LONG *)ti, schedule);
44                 iv = ivec;
45                 t = ti[0];
46                 l2n(t, iv);
47                 t = ti[1];
48                 l2n(t, iv);
49                 iv = ivec;
50             }
51             c = *(in++) ^ iv[n];
52             *(out++) = c;
53             iv[n] = c;
54             n = (n + 1) & 0x07;
55         }
56     } else {
57         while (l--) {
58             if (n == 0) {
59                 n2l(iv, v0);
60                 ti[0] = v0;
61                 n2l(iv, v1);
62                 ti[1] = v1;
63                 CAST_encrypt((CAST_LONG *)ti, schedule);
64                 iv = ivec;
65                 t = ti[0];
66                 l2n(t, iv);
67                 t = ti[1];
68                 l2n(t, iv);
69                 iv = ivec;
70             }
71             cc = *(in++);
72             c = iv[n];
73             iv[n] = cc;
74             *(out++) = c ^ cc;
75             n = (n + 1) & 0x07;
76         }
77     }
78     v0 = v1 = ti[0] = ti[1] = t = c = cc = 0;
79     *num = n;
80 }
81