1 /* $OpenBSD: cipher-ctr.c,v 1.11 2010/10/01 23:05:32 djm Exp $ */
2 /*
3 * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17 #include "includes.h"
18
19 #include <sys/types.h>
20
21 #include <stdarg.h>
22 #include <string.h>
23
24 #include <openssl/evp.h>
25
26 #include "xmalloc.h"
27 #include "log.h"
28
29 /* compatibility with old or broken OpenSSL versions */
30 #include "openbsd-compat/openssl-compat.h"
31
32 #ifndef USE_BUILTIN_RIJNDAEL
33 #include <openssl/aes.h>
34 #endif
35
36 const EVP_CIPHER *evp_aes_128_ctr(void);
37 void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, size_t);
38
39 struct ssh_aes_ctr_ctx
40 {
41 AES_KEY aes_ctx;
42 u_char aes_counter[AES_BLOCK_SIZE];
43 };
44
45 /*
46 * increment counter 'ctr',
47 * the counter is of size 'len' bytes and stored in network-byte-order.
48 * (LSB at ctr[len-1], MSB at ctr[0])
49 */
50 static void
ssh_ctr_inc(u_char * ctr,size_t len)51 ssh_ctr_inc(u_char *ctr, size_t len)
52 {
53 int i;
54
55 for (i = len - 1; i >= 0; i--)
56 if (++ctr[i]) /* continue on overflow */
57 return;
58 }
59
60 static int
ssh_aes_ctr(EVP_CIPHER_CTX * ctx,u_char * dest,const u_char * src,LIBCRYPTO_EVP_INL_TYPE len)61 ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
62 LIBCRYPTO_EVP_INL_TYPE len)
63 {
64 struct ssh_aes_ctr_ctx *c;
65 size_t n = 0;
66 u_char buf[AES_BLOCK_SIZE];
67
68 if (len == 0)
69 return (1);
70 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
71 return (0);
72
73 while ((len--) > 0) {
74 if (n == 0) {
75 AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
76 ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
77 }
78 *(dest++) = *(src++) ^ buf[n];
79 n = (n + 1) % AES_BLOCK_SIZE;
80 }
81 return (1);
82 }
83
84 static int
ssh_aes_ctr_init(EVP_CIPHER_CTX * ctx,const u_char * key,const u_char * iv,int enc)85 ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
86 int enc)
87 {
88 struct ssh_aes_ctr_ctx *c;
89
90 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
91 c = xmalloc(sizeof(*c));
92 EVP_CIPHER_CTX_set_app_data(ctx, c);
93 }
94 if (key != NULL)
95 AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
96 &c->aes_ctx);
97 if (iv != NULL)
98 memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
99 return (1);
100 }
101
102 static int
ssh_aes_ctr_cleanup(EVP_CIPHER_CTX * ctx)103 ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
104 {
105 struct ssh_aes_ctr_ctx *c;
106
107 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
108 memset(c, 0, sizeof(*c));
109 xfree(c);
110 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
111 }
112 return (1);
113 }
114
115 void
ssh_aes_ctr_iv(EVP_CIPHER_CTX * evp,int doset,u_char * iv,size_t len)116 ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, size_t len)
117 {
118 struct ssh_aes_ctr_ctx *c;
119
120 if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
121 fatal("ssh_aes_ctr_iv: no context");
122 if (doset)
123 memcpy(c->aes_counter, iv, len);
124 else
125 memcpy(iv, c->aes_counter, len);
126 }
127
128 const EVP_CIPHER *
evp_aes_128_ctr(void)129 evp_aes_128_ctr(void)
130 {
131 static EVP_CIPHER aes_ctr;
132
133 memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
134 aes_ctr.nid = NID_undef;
135 aes_ctr.block_size = AES_BLOCK_SIZE;
136 aes_ctr.iv_len = AES_BLOCK_SIZE;
137 aes_ctr.key_len = 16;
138 aes_ctr.init = ssh_aes_ctr_init;
139 aes_ctr.cleanup = ssh_aes_ctr_cleanup;
140 aes_ctr.do_cipher = ssh_aes_ctr;
141 #ifndef SSH_OLD_EVP
142 aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
143 EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
144 #endif
145 return (&aes_ctr);
146 }
147