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/evp.h>
25
26 #include "log.h"
27 #include "xmalloc.h"
28 #include <openssl/aes.h>
29
30 const EVP_CIPHER *evp_aes_128_ctr(void);
31 void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
32
33 struct 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 */
44 static void
45 ssh_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
54 static int
55 ssh_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
78 static int
79 ssh_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
96 static int
97 ssh_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
109 void
110 ssh_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 */
126 static const EVP_CIPHER *
127 evp_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
150 const EVP_CIPHER *
151 evp_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
158 const EVP_CIPHER *
159 evp_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
166 const EVP_CIPHER *
167 evp_aes_256_ctr(void)
168 {
169 static EVP_CIPHER aes_ctr;
170
171 return (evp_aes_ctr("aes-256-ctr", 32, &aes_ctr));
172 }