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Damien Millerf5399c22003-05-18 20:53:59 +10001/*
Damien Miller0275b522003-06-18 20:29:35 +10002 * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
Damien Millerf5399c22003-05-18 20:53:59 +10003 *
Damien Miller0275b522003-06-18 20:29:35 +10004 * 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.
Damien Millerf5399c22003-05-18 20:53:59 +10007 *
Damien Miller0275b522003-06-18 20:29:35 +10008 * 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.
Damien Millerf5399c22003-05-18 20:53:59 +100015 */
16#include "includes.h"
Darren Tuckerfc57f712004-02-07 10:41:48 +110017RCSID("$OpenBSD: cipher-ctr.c,v 1.4 2004/02/06 23:41:13 dtucker Exp $");
Damien Millerf5399c22003-05-18 20:53:59 +100018
19#include <openssl/evp.h>
20
21#include "log.h"
22#include "xmalloc.h"
23
Damien Miller5c3a5582003-09-23 22:12:38 +100024#if OPENSSL_VERSION_NUMBER < 0x00906000L
25#define SSH_OLD_EVP
26#endif
27
Damien Millerf5399c22003-05-18 20:53:59 +100028#if OPENSSL_VERSION_NUMBER < 0x00907000L
29#include "rijndael.h"
30#define AES_KEY rijndael_ctx
31#define AES_BLOCK_SIZE 16
32#define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
33#define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
34#else
35#include <openssl/aes.h>
36#endif
37
38const EVP_CIPHER *evp_aes_128_ctr(void);
39void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
40
41struct ssh_aes_ctr_ctx
42{
43 AES_KEY aes_ctx;
44 u_char aes_counter[AES_BLOCK_SIZE];
45};
46
47/*
48 * increment counter 'ctr',
49 * the counter is of size 'len' bytes and stored in network-byte-order.
50 * (LSB at ctr[len-1], MSB at ctr[0])
51 */
52static void
53ssh_ctr_inc(u_char *ctr, u_int len)
54{
55 int i;
56
57 for (i = len - 1; i >= 0; i--)
58 if (++ctr[i]) /* continue on overflow */
59 return;
60}
61
62static int
63ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
64 u_int len)
65{
66 struct ssh_aes_ctr_ctx *c;
67 u_int n = 0;
68 u_char buf[AES_BLOCK_SIZE];
69
70 if (len == 0)
71 return (1);
72 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
73 return (0);
74
75 while ((len--) > 0) {
76 if (n == 0) {
77 AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
78 ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
79 }
80 *(dest++) = *(src++) ^ buf[n];
81 n = (n + 1) % AES_BLOCK_SIZE;
82 }
83 return (1);
84}
85
86static int
87ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
88 int enc)
89{
90 struct ssh_aes_ctr_ctx *c;
91
92 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
93 c = xmalloc(sizeof(*c));
94 EVP_CIPHER_CTX_set_app_data(ctx, c);
95 }
96 if (key != NULL)
Darren Tuckerfc57f712004-02-07 10:41:48 +110097 AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
98 &c->aes_ctx);
Damien Millerf5399c22003-05-18 20:53:59 +100099 if (iv != NULL)
100 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
101 return (1);
102}
103
104static int
105ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
106{
107 struct ssh_aes_ctr_ctx *c;
108
109 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
110 memset(c, 0, sizeof(*c));
111 xfree(c);
112 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
113 }
114 return (1);
115}
116
117void
118ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
119{
120 struct ssh_aes_ctr_ctx *c;
121
122 if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
123 fatal("ssh_aes_ctr_iv: no context");
124 if (doset)
125 memcpy(c->aes_counter, iv, len);
126 else
127 memcpy(iv, c->aes_counter, len);
128}
129
130const EVP_CIPHER *
131evp_aes_128_ctr(void)
132{
133 static EVP_CIPHER aes_ctr;
134
135 memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
136 aes_ctr.nid = NID_undef;
137 aes_ctr.block_size = AES_BLOCK_SIZE;
138 aes_ctr.iv_len = AES_BLOCK_SIZE;
139 aes_ctr.key_len = 16;
140 aes_ctr.init = ssh_aes_ctr_init;
141 aes_ctr.cleanup = ssh_aes_ctr_cleanup;
142 aes_ctr.do_cipher = ssh_aes_ctr;
Damien Miller5c3a5582003-09-23 22:12:38 +1000143#ifndef SSH_OLD_EVP
Damien Millerf5399c22003-05-18 20:53:59 +1000144 aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
145 EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
Damien Miller5c3a5582003-09-23 22:12:38 +1000146#endif
Damien Millerf5399c22003-05-18 20:53:59 +1000147 return (&aes_ctr);
148}