xref: /freebsd/crypto/openssh/cipher-aesctr.c (revision d9b9dae1a954c5a277eada994d268f88eb5f3f20)
1*bc5531deSDag-Erling Smørgrav /* $OpenBSD: cipher-aesctr.c,v 1.2 2015/01/14 10:24:42 markus Exp $ */
2a0ee8cc6SDag-Erling Smørgrav /*
3*bc5531deSDag-Erling Smørgrav  * Copyright (c) 2003 Markus Friedl.  All rights reserved.
4a0ee8cc6SDag-Erling Smørgrav  *
5a0ee8cc6SDag-Erling Smørgrav  * Permission to use, copy, modify, and distribute this software for any
6a0ee8cc6SDag-Erling Smørgrav  * purpose with or without fee is hereby granted, provided that the above
7a0ee8cc6SDag-Erling Smørgrav  * copyright notice and this permission notice appear in all copies.
8a0ee8cc6SDag-Erling Smørgrav  *
9a0ee8cc6SDag-Erling Smørgrav  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10a0ee8cc6SDag-Erling Smørgrav  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11a0ee8cc6SDag-Erling Smørgrav  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12a0ee8cc6SDag-Erling Smørgrav  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13a0ee8cc6SDag-Erling Smørgrav  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14a0ee8cc6SDag-Erling Smørgrav  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15a0ee8cc6SDag-Erling Smørgrav  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16a0ee8cc6SDag-Erling Smørgrav  */
17a0ee8cc6SDag-Erling Smørgrav 
18*bc5531deSDag-Erling Smørgrav #include "includes.h"
19*bc5531deSDag-Erling Smørgrav 
20a0ee8cc6SDag-Erling Smørgrav #include <sys/types.h>
21a0ee8cc6SDag-Erling Smørgrav #include <string.h>
22a0ee8cc6SDag-Erling Smørgrav 
23*bc5531deSDag-Erling Smørgrav #ifndef WITH_OPENSSL
24*bc5531deSDag-Erling Smørgrav 
25a0ee8cc6SDag-Erling Smørgrav #include "cipher-aesctr.h"
26a0ee8cc6SDag-Erling Smørgrav 
27a0ee8cc6SDag-Erling Smørgrav /*
28a0ee8cc6SDag-Erling Smørgrav  * increment counter 'ctr',
29a0ee8cc6SDag-Erling Smørgrav  * the counter is of size 'len' bytes and stored in network-byte-order.
30a0ee8cc6SDag-Erling Smørgrav  * (LSB at ctr[len-1], MSB at ctr[0])
31a0ee8cc6SDag-Erling Smørgrav  */
32*bc5531deSDag-Erling Smørgrav static inline void
aesctr_inc(u8 * ctr,u32 len)33a0ee8cc6SDag-Erling Smørgrav aesctr_inc(u8 *ctr, u32 len)
34a0ee8cc6SDag-Erling Smørgrav {
35a0ee8cc6SDag-Erling Smørgrav 	ssize_t i;
36a0ee8cc6SDag-Erling Smørgrav 
37a0ee8cc6SDag-Erling Smørgrav #ifndef CONSTANT_TIME_INCREMENT
38a0ee8cc6SDag-Erling Smørgrav 	for (i = len - 1; i >= 0; i--)
39a0ee8cc6SDag-Erling Smørgrav 		if (++ctr[i])	/* continue on overflow */
40a0ee8cc6SDag-Erling Smørgrav 			return;
41a0ee8cc6SDag-Erling Smørgrav #else
42a0ee8cc6SDag-Erling Smørgrav 	u8 x, add = 1;
43a0ee8cc6SDag-Erling Smørgrav 
44a0ee8cc6SDag-Erling Smørgrav 	for (i = len - 1; i >= 0; i--) {
45a0ee8cc6SDag-Erling Smørgrav 		ctr[i] += add;
46a0ee8cc6SDag-Erling Smørgrav 		/* constant time for: x = ctr[i] ? 1 : 0 */
47a0ee8cc6SDag-Erling Smørgrav 		x = ctr[i];
48a0ee8cc6SDag-Erling Smørgrav 		x = (x | (x >> 4)) & 0xf;
49a0ee8cc6SDag-Erling Smørgrav 		x = (x | (x >> 2)) & 0x3;
50a0ee8cc6SDag-Erling Smørgrav 		x = (x | (x >> 1)) & 0x1;
51a0ee8cc6SDag-Erling Smørgrav 		add *= (x^1);
52a0ee8cc6SDag-Erling Smørgrav 	}
53a0ee8cc6SDag-Erling Smørgrav #endif
54a0ee8cc6SDag-Erling Smørgrav }
55a0ee8cc6SDag-Erling Smørgrav 
56a0ee8cc6SDag-Erling Smørgrav void
aesctr_keysetup(aesctr_ctx * x,const u8 * k,u32 kbits,u32 ivbits)57a0ee8cc6SDag-Erling Smørgrav aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
58a0ee8cc6SDag-Erling Smørgrav {
59a0ee8cc6SDag-Erling Smørgrav 	x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits);
60a0ee8cc6SDag-Erling Smørgrav }
61a0ee8cc6SDag-Erling Smørgrav 
62a0ee8cc6SDag-Erling Smørgrav void
aesctr_ivsetup(aesctr_ctx * x,const u8 * iv)63a0ee8cc6SDag-Erling Smørgrav aesctr_ivsetup(aesctr_ctx *x,const u8 *iv)
64a0ee8cc6SDag-Erling Smørgrav {
65a0ee8cc6SDag-Erling Smørgrav 	memcpy(x->ctr, iv, AES_BLOCK_SIZE);
66a0ee8cc6SDag-Erling Smørgrav }
67a0ee8cc6SDag-Erling Smørgrav 
68a0ee8cc6SDag-Erling Smørgrav void
aesctr_encrypt_bytes(aesctr_ctx * x,const u8 * m,u8 * c,u32 bytes)69a0ee8cc6SDag-Erling Smørgrav aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes)
70a0ee8cc6SDag-Erling Smørgrav {
71a0ee8cc6SDag-Erling Smørgrav 	u32 n = 0;
72a0ee8cc6SDag-Erling Smørgrav 	u8 buf[AES_BLOCK_SIZE];
73a0ee8cc6SDag-Erling Smørgrav 
74a0ee8cc6SDag-Erling Smørgrav 	while ((bytes--) > 0) {
75a0ee8cc6SDag-Erling Smørgrav 		if (n == 0) {
76a0ee8cc6SDag-Erling Smørgrav 			rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf);
77a0ee8cc6SDag-Erling Smørgrav 			aesctr_inc(x->ctr, AES_BLOCK_SIZE);
78a0ee8cc6SDag-Erling Smørgrav 		}
79a0ee8cc6SDag-Erling Smørgrav 		*(c++) = *(m++) ^ buf[n];
80a0ee8cc6SDag-Erling Smørgrav 		n = (n + 1) % AES_BLOCK_SIZE;
81a0ee8cc6SDag-Erling Smørgrav 	}
82a0ee8cc6SDag-Erling Smørgrav }
83*bc5531deSDag-Erling Smørgrav #endif /* !WITH_OPENSSL */
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