cipher-ctr.c revision 295367 
1/* $OpenBSD: cipher-ctr.c,v 1.11 2010/10/01 23:05:32 djm Exp $ */
2/*
3 * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
4 *
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#include "includes.h"
18
19#if defined(WITH_OPENSSL) && !defined(OPENSSL_HAVE_EVPCTR)
20#include <sys/types.h>
21
22#include <stdarg.h>
23#include <string.h>
24
25#include <openssl/evp.h>
26
27#include "xmalloc.h"
28#include "log.h"
29
30/* compatibility with old or broken OpenSSL versions */
31#include "openbsd-compat/openssl-compat.h"
32
33#ifndef USE_BUILTIN_RIJNDAEL
34#include <openssl/aes.h>
35#endif
36
37struct ssh_aes_ctr_ctx
38{
39	AES_KEY		aes_ctx;
40	u_char		aes_counter[AES_BLOCK_SIZE];
41};
42
43/*
44 * increment counter 'ctr',
45 * the counter is of size 'len' bytes and stored in network-byte-order.
46 * (LSB at ctr[len-1], MSB at ctr[0])
47 */
48static void
49ssh_ctr_inc(u_char *ctr, size_t len)
50{
51	int i;
52
53	for (i = len - 1; i >= 0; i--)
54		if (++ctr[i])	/* continue on overflow */
55			return;
56}
57
58static int
59ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
60    LIBCRYPTO_EVP_INL_TYPE len)
61{
62	struct ssh_aes_ctr_ctx *c;
63	size_t n = 0;
64	u_char buf[AES_BLOCK_SIZE];
65
66	if (len == 0)
67		return (1);
68	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
69		return (0);
70
71	while ((len--) > 0) {
72		if (n == 0) {
73			AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
74			ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
75		}
76		*(dest++) = *(src++) ^ buf[n];
77		n = (n + 1) % AES_BLOCK_SIZE;
78	}
79	return (1);
80}
81
82static int
83ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
84    int enc)
85{
86	struct ssh_aes_ctr_ctx *c;
87
88	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
89		c = xmalloc(sizeof(*c));
90		EVP_CIPHER_CTX_set_app_data(ctx, c);
91	}
92	if (key != NULL)
93		AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
94		    &c->aes_ctx);
95	if (iv != NULL)
96		memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
97	return (1);
98}
99
100static int
101ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
102{
103	struct ssh_aes_ctr_ctx *c;
104
105	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
106		memset(c, 0, sizeof(*c));
107		free(c);
108		EVP_CIPHER_CTX_set_app_data(ctx, NULL);
109	}
110	return (1);
111}
112
113void
114ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, size_t len)
115{
116	struct ssh_aes_ctr_ctx *c;
117
118	if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
119		fatal("ssh_aes_ctr_iv: no context");
120	if (doset)
121		memcpy(c->aes_counter, iv, len);
122	else
123		memcpy(iv, c->aes_counter, len);
124}
125
126const EVP_CIPHER *
127evp_aes_128_ctr(void)
128{
129	static EVP_CIPHER aes_ctr;
130
131	memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
132	aes_ctr.nid = NID_undef;
133	aes_ctr.block_size = AES_BLOCK_SIZE;
134	aes_ctr.iv_len = AES_BLOCK_SIZE;
135	aes_ctr.key_len = 16;
136	aes_ctr.init = ssh_aes_ctr_init;
137	aes_ctr.cleanup = ssh_aes_ctr_cleanup;
138	aes_ctr.do_cipher = ssh_aes_ctr;
139#ifndef SSH_OLD_EVP
140	aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
141	    EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
142#endif
143	return (&aes_ctr);
144}
145
146#endif /* defined(WITH_OPENSSL) && !defined(OPENSSL_HAVE_EVPCTR) */
147