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markus@openbsd.org60c2c4e2015-01-14 10:24:42 +00001/* $OpenBSD: cipher-aesctr.c,v 1.2 2015/01/14 10:24:42 markus Exp $ */
Damien Miller1f0311c2014-05-15 14:24:09 +10002/*
markus@openbsd.org60c2c4e2015-01-14 10:24:42 +00003 * Copyright (c) 2003 Markus Friedl. All rights reserved.
Damien Miller1f0311c2014-05-15 14:24:09 +10004 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#include <sys/types.h>
19#include <string.h>
20
Damien Miller72ef7c12015-01-15 02:21:31 +110021#ifndef WITH_OPENSSL
22
Damien Miller1f0311c2014-05-15 14:24:09 +100023#include "cipher-aesctr.h"
24
25/*
26 * increment counter 'ctr',
27 * the counter is of size 'len' bytes and stored in network-byte-order.
28 * (LSB at ctr[len-1], MSB at ctr[0])
29 */
Tim Rice1221b222015-02-23 21:50:34 -080030static inline void
Damien Miller1f0311c2014-05-15 14:24:09 +100031aesctr_inc(u8 *ctr, u32 len)
32{
33 ssize_t i;
34
35#ifndef CONSTANT_TIME_INCREMENT
36 for (i = len - 1; i >= 0; i--)
37 if (++ctr[i]) /* continue on overflow */
38 return;
39#else
40 u8 x, add = 1;
41
42 for (i = len - 1; i >= 0; i--) {
43 ctr[i] += add;
44 /* constant time for: x = ctr[i] ? 1 : 0 */
45 x = ctr[i];
46 x = (x | (x >> 4)) & 0xf;
47 x = (x | (x >> 2)) & 0x3;
48 x = (x | (x >> 1)) & 0x1;
49 add *= (x^1);
50 }
51#endif
52}
53
54void
55aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
56{
57 x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits);
58}
59
60void
61aesctr_ivsetup(aesctr_ctx *x,const u8 *iv)
62{
63 memcpy(x->ctr, iv, AES_BLOCK_SIZE);
64}
65
66void
67aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes)
68{
69 u32 n = 0;
70 u8 buf[AES_BLOCK_SIZE];
71
72 while ((bytes--) > 0) {
73 if (n == 0) {
74 rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf);
75 aesctr_inc(x->ctr, AES_BLOCK_SIZE);
76 }
77 *(c++) = *(m++) ^ buf[n];
78 n = (n + 1) % AES_BLOCK_SIZE;
79 }
80}
Damien Miller72ef7c12015-01-15 02:21:31 +110081#endif /* !WITH_OPENSSL */