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-rw-r--r--cipher-ctr.c141
1 files changed, 141 insertions, 0 deletions
diff --git a/cipher-ctr.c b/cipher-ctr.c
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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#include "includes.h"
17RCSID("$OpenBSD: cipher-ctr.c,v 1.2 2003/06/17 18:14:23 markus Exp $");
18
19#include <openssl/evp.h>
20
21#include "log.h"
22#include "xmalloc.h"
23
24#if OPENSSL_VERSION_NUMBER < 0x00907000L
25#include "rijndael.h"
26#define AES_KEY rijndael_ctx
27#define AES_BLOCK_SIZE 16
28#define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
29#define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
30#else
31#include <openssl/aes.h>
32#endif
33
34const EVP_CIPHER *evp_aes_128_ctr(void);
35void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
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, u_int 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 u_int len)
61{
62 struct ssh_aes_ctr_ctx *c;
63 u_int 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, ctx->key_len * 8, &c->aes_ctx);
94 if (iv != NULL)
95 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
96 return (1);
97}
98
99static int
100ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
101{
102 struct ssh_aes_ctr_ctx *c;
103
104 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
105 memset(c, 0, sizeof(*c));
106 xfree(c);
107 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
108 }
109 return (1);
110}
111
112void
113ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
114{
115 struct ssh_aes_ctr_ctx *c;
116
117 if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
118 fatal("ssh_aes_ctr_iv: no context");
119 if (doset)
120 memcpy(c->aes_counter, iv, len);
121 else
122 memcpy(iv, c->aes_counter, len);
123}
124
125const EVP_CIPHER *
126evp_aes_128_ctr(void)
127{
128 static EVP_CIPHER aes_ctr;
129
130 memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
131 aes_ctr.nid = NID_undef;
132 aes_ctr.block_size = AES_BLOCK_SIZE;
133 aes_ctr.iv_len = AES_BLOCK_SIZE;
134 aes_ctr.key_len = 16;
135 aes_ctr.init = ssh_aes_ctr_init;
136 aes_ctr.cleanup = ssh_aes_ctr_cleanup;
137 aes_ctr.do_cipher = ssh_aes_ctr;
138 aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
139 EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
140 return (&aes_ctr);
141}