1/*
2 * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
3 *
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16/*
17 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
18 * Use is subject to license terms.
19 */
20
21#include "includes.h"
22RCSID("$OpenBSD: cipher-ctr.c,v 1.4 2004/02/06 23:41:13 dtucker Exp $");
23
24#include <openssl/evp.h>
25
26#include "log.h"
27#include "xmalloc.h"
28#include <openssl/aes.h>
29
30const EVP_CIPHER *evp_aes_128_ctr(void);
31void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
32
33struct ssh_aes_ctr_ctx
34{
35	AES_KEY		aes_ctx;
36	u_char		aes_counter[AES_BLOCK_SIZE];
37};
38
39/*
40 * increment counter 'ctr',
41 * the counter is of size 'len' bytes and stored in network-byte-order.
42 * (LSB at ctr[len-1], MSB at ctr[0])
43 */
44static void
45ssh_ctr_inc(u_char *ctr, u_int len)
46{
47	int i;
48
49	for (i = len - 1; i >= 0; i--)
50		if (++ctr[i])	/* continue on overflow */
51			return;
52}
53
54static int
55ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
56    u_int len)
57{
58	struct ssh_aes_ctr_ctx *c;
59	u_int n = 0;
60	u_char buf[AES_BLOCK_SIZE];
61
62	if (len == 0)
63		return (1);
64	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
65		return (0);
66
67	while ((len--) > 0) {
68		if (n == 0) {
69			AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
70			ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
71		}
72		*(dest++) = *(src++) ^ buf[n];
73		n = (n + 1) % AES_BLOCK_SIZE;
74	}
75	return (1);
76}
77
78static int
79ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
80    int enc)
81{
82	struct ssh_aes_ctr_ctx *c;
83
84	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
85		c = xmalloc(sizeof(*c));
86		EVP_CIPHER_CTX_set_app_data(ctx, c);
87	}
88	if (key != NULL)
89		AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
90		     &c->aes_ctx);
91	if (iv != NULL)
92		memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
93	return (1);
94}
95
96static int
97ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
98{
99	struct ssh_aes_ctr_ctx *c;
100
101	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
102		memset(c, 0, sizeof(*c));
103		xfree(c);
104		EVP_CIPHER_CTX_set_app_data(ctx, NULL);
105	}
106	return (1);
107}
108
109void
110ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
111{
112	struct ssh_aes_ctr_ctx *c;
113
114	if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
115		fatal("ssh_aes_ctr_iv: no context");
116	if (doset)
117		memcpy(c->aes_counter, iv, len);
118	else
119		memcpy(iv, c->aes_counter, len);
120}
121
122/*
123 * Function fills an EVP_CIPHER structure for AES CTR functions based on the NID
124 * and the key length.
125 */
126static const EVP_CIPHER *
127evp_aes_ctr(const char *nid, int key_len, EVP_CIPHER *aes_ctr)
128{
129	memset(aes_ctr, 0, sizeof(EVP_CIPHER));
130	/*
131	 * If the PKCS#11 engine is used the AES CTR NIDs were dynamically
132	 * created during the engine initialization. If the engine is not used
133	 * we work with NID_undef's which is OK since in that case OpenSSL
134	 * doesn't use NIDs at all.
135	 */
136	if ((aes_ctr->nid = OBJ_ln2nid(nid)) != NID_undef)
137		debug3("%s NID found", nid);
138
139	aes_ctr->block_size = AES_BLOCK_SIZE;
140	aes_ctr->iv_len = AES_BLOCK_SIZE;
141	aes_ctr->key_len = key_len;
142	aes_ctr->init = ssh_aes_ctr_init;
143	aes_ctr->cleanup = ssh_aes_ctr_cleanup;
144	aes_ctr->do_cipher = ssh_aes_ctr;
145	aes_ctr->flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
146	    EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
147	return (aes_ctr);
148}
149
150const EVP_CIPHER *
151evp_aes_128_ctr(void)
152{
153	static EVP_CIPHER aes_ctr;
154
155	return (evp_aes_ctr("aes-128-ctr", 16, &aes_ctr));
156}
157
158const EVP_CIPHER *
159evp_aes_192_ctr(void)
160{
161	static EVP_CIPHER aes_ctr;
162
163	return (evp_aes_ctr("aes-192-ctr", 24, &aes_ctr));
164}
165
166const EVP_CIPHER *
167evp_aes_256_ctr(void)
168{
169	static EVP_CIPHER aes_ctr;
170
171	return (evp_aes_ctr("aes-256-ctr", 32, &aes_ctr));
172}
173