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"
22 RCSID("$OpenBSD: cipher-ctr.c,v 1.4 2004/02/06 23:41:13 dtucker Exp $");
23
24 #include <openssl/opensslconf.h>
25 #include <openssl/evp.h>
26
27 #include "log.h"
28 #include "xmalloc.h"
29 #include <openssl/aes.h>
30
31 const EVP_CIPHER *evp_aes_128_ctr(void);
32 void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
33
34 struct ssh_aes_ctr_ctx
35 {
36 AES_KEY aes_ctx;
37 u_char aes_counter[AES_BLOCK_SIZE];
38 };
39
40 /*
41 * increment counter 'ctr',
42 * the counter is of size 'len' bytes and stored in network-byte-order.
43 * (LSB at ctr[len-1], MSB at ctr[0])
44 */
45 static void
46 ssh_ctr_inc(u_char *ctr, u_int len)
47 {
48 int i;
49
50 for (i = len - 1; i >= 0; i--)
51 if (++ctr[i]) /* continue on overflow */
52 return;
53 }
54
55 static int
56 ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
57 u_int len)
58 {
59 struct ssh_aes_ctr_ctx *c;
60 u_int n = 0;
61 u_char buf[AES_BLOCK_SIZE];
62
63 if (len == 0)
64 return (1);
65 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
66 return (0);
67
68 while ((len--) > 0) {
69 if (n == 0) {
70 AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
71 ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
72 }
73 *(dest++) = *(src++) ^ buf[n];
74 n = (n + 1) % AES_BLOCK_SIZE;
75 }
76 return (1);
77 }
78
79 static int
80 ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
81 int enc)
82 {
83 struct ssh_aes_ctr_ctx *c;
84
85 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
86 c = xmalloc(sizeof(*c));
87 EVP_CIPHER_CTX_set_app_data(ctx, c);
88 }
89 if (key != NULL)
90 AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
91 &c->aes_ctx);
92 if (iv != NULL)
93 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
94 return (1);
95 }
96
97 static int
98 ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
99 {
100 struct ssh_aes_ctr_ctx *c;
101
102 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
103 memset(c, 0, sizeof(*c));
104 xfree(c);
105 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
106 }
107 return (1);
108 }
109
110 void
111 ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
112 {
113 struct ssh_aes_ctr_ctx *c;
114
115 if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
116 fatal("ssh_aes_ctr_iv: no context");
117 if (doset)
118 memcpy(c->aes_counter, iv, len);
119 else
120 memcpy(iv, c->aes_counter, len);
121 }
122
123 /*
124 * Function fills an EVP_CIPHER structure for AES CTR functions based on the NID
125 * and the key length.
126 */
127 static const EVP_CIPHER *
128 evp_aes_ctr(const char *nid, int key_len, EVP_CIPHER *aes_ctr)
129 {
130 memset(aes_ctr, 0, sizeof(EVP_CIPHER));
131 /*
132 * If the PKCS#11 engine is used the AES CTR NIDs were dynamically
133 * created during the engine initialization. If the engine is not used
134 * we work with NID_undef's which is OK since in that case OpenSSL
135 * doesn't use NIDs at all.
136 */
137 if ((aes_ctr->nid = OBJ_ln2nid(nid)) != NID_undef)
138 debug3("%s NID found", nid);
139
140 aes_ctr->block_size = AES_BLOCK_SIZE;
141 aes_ctr->iv_len = AES_BLOCK_SIZE;
142 aes_ctr->key_len = key_len;
143 aes_ctr->init = ssh_aes_ctr_init;
144 aes_ctr->cleanup = ssh_aes_ctr_cleanup;
145 aes_ctr->do_cipher = ssh_aes_ctr;
146 aes_ctr->flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
147 EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
148 return (aes_ctr);
149 }
150
151 const EVP_CIPHER *
152 evp_aes_128_ctr(void)
153 {
154 static EVP_CIPHER aes_ctr;
155
156 return (evp_aes_ctr("aes-128-ctr", 16, &aes_ctr));
157 }
158
159 const EVP_CIPHER *
160 evp_aes_192_ctr(void)
161 {
162 static EVP_CIPHER aes_ctr;
163
164 return (evp_aes_ctr("aes-192-ctr", 24, &aes_ctr));
165 }
166
167 const EVP_CIPHER *
168 evp_aes_256_ctr(void)
169 {
170 static EVP_CIPHER aes_ctr;
171
172 return (evp_aes_ctr("aes-256-ctr", 32, &aes_ctr));
173 }