1/*	$NetBSD: cipher-aesctr.c,v 1.2 2018/04/06 18:59:00 christos Exp $	*/
2/* $OpenBSD: cipher-aesctr.c,v 1.2 2015/01/14 10:24:42 markus Exp $ */
3/*
4 * Copyright (c) 2003 Markus Friedl.  All rights reserved.
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18#include "includes.h"
19__RCSID("$NetBSD: cipher-aesctr.c,v 1.2 2018/04/06 18:59:00 christos Exp $");
20
21#include <sys/types.h>
22#include <string.h>
23
24#include "cipher-aesctr.h"
25
26/*
27 * increment counter 'ctr',
28 * the counter is of size 'len' bytes and stored in network-byte-order.
29 * (LSB at ctr[len-1], MSB at ctr[0])
30 */
31static __inline__ void
32aesctr_inc(u8 *ctr, u32 len)
33{
34	ssize_t i;
35
36#ifndef CONSTANT_TIME_INCREMENT
37	for (i = len - 1; i >= 0; i--)
38		if (++ctr[i])	/* continue on overflow */
39			return;
40#else
41	u8 x, add = 1;
42
43	for (i = len - 1; i >= 0; i--) {
44		ctr[i] += add;
45		/* constant time for: x = ctr[i] ? 1 : 0 */
46		x = ctr[i];
47		x = (x | (x >> 4)) & 0xf;
48		x = (x | (x >> 2)) & 0x3;
49		x = (x | (x >> 1)) & 0x1;
50		add *= (x^1);
51	}
52#endif
53}
54
55void
56aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
57{
58	x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits);
59}
60
61void
62aesctr_ivsetup(aesctr_ctx *x,const u8 *iv)
63{
64	memcpy(x->ctr, iv, AES_BLOCK_SIZE);
65}
66
67void
68aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes)
69{
70	u32 n = 0;
71	u8 buf[AES_BLOCK_SIZE];
72
73	while ((bytes--) > 0) {
74		if (n == 0) {
75			rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf);
76			aesctr_inc(x->ctr, AES_BLOCK_SIZE);
77		}
78		*(c++) = *(m++) ^ buf[n];
79		n = (n + 1) % AES_BLOCK_SIZE;
80	}
81}
82