xref: /openssh-portable/cipher-ctr.c (revision 72ef7c14)
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 #if defined(WITH_OPENSSL) && !defined(OPENSSL_HAVE_EVPCTR)
20 #include <sys/types.h>
21 
22 #include <stdarg.h>
23 #include <string.h>
24 
25 #include <openssl/evp.h>
26 
27 #include "xmalloc.h"
28 #include "log.h"
29 
30 /* compatibility with old or broken OpenSSL versions */
31 #include "openbsd-compat/openssl-compat.h"
32 
33 #ifndef USE_BUILTIN_RIJNDAEL
34 #include <openssl/aes.h>
35 #endif
36 
37 struct 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  */
48 static void
ssh_ctr_inc(u_char * ctr,size_t len)49 ssh_ctr_inc(u_char *ctr, size_t 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 
58 static int
ssh_aes_ctr(EVP_CIPHER_CTX * ctx,u_char * dest,const u_char * src,LIBCRYPTO_EVP_INL_TYPE len)59 ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
60     LIBCRYPTO_EVP_INL_TYPE len)
61 {
62 	struct ssh_aes_ctr_ctx *c;
63 	size_t 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 
82 static int
ssh_aes_ctr_init(EVP_CIPHER_CTX * ctx,const u_char * key,const u_char * iv,int enc)83 ssh_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, EVP_CIPHER_CTX_key_length(ctx) * 8,
94 		    &c->aes_ctx);
95 	if (iv != NULL)
96 		memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
97 	return (1);
98 }
99 
100 static int
ssh_aes_ctr_cleanup(EVP_CIPHER_CTX * ctx)101 ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
102 {
103 	struct ssh_aes_ctr_ctx *c;
104 
105 	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
106 		memset(c, 0, sizeof(*c));
107 		free(c);
108 		EVP_CIPHER_CTX_set_app_data(ctx, NULL);
109 	}
110 	return (1);
111 }
112 
113 void
ssh_aes_ctr_iv(EVP_CIPHER_CTX * evp,int doset,u_char * iv,size_t len)114 ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, size_t len)
115 {
116 	struct ssh_aes_ctr_ctx *c;
117 
118 	if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
119 		fatal("ssh_aes_ctr_iv: no context");
120 	if (doset)
121 		memcpy(c->aes_counter, iv, len);
122 	else
123 		memcpy(iv, c->aes_counter, len);
124 }
125 
126 const EVP_CIPHER *
evp_aes_128_ctr(void)127 evp_aes_128_ctr(void)
128 {
129 	static EVP_CIPHER aes_ctr;
130 
131 	memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
132 	aes_ctr.nid = NID_undef;
133 	aes_ctr.block_size = AES_BLOCK_SIZE;
134 	aes_ctr.iv_len = AES_BLOCK_SIZE;
135 	aes_ctr.key_len = 16;
136 	aes_ctr.init = ssh_aes_ctr_init;
137 	aes_ctr.cleanup = ssh_aes_ctr_cleanup;
138 	aes_ctr.do_cipher = ssh_aes_ctr;
139 #ifndef SSH_OLD_EVP
140 	aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
141 	    EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
142 #endif
143 	return (&aes_ctr);
144 }
145 
146 #endif /* defined(WITH_OPENSSL) && !defined(OPENSSL_HAVE_EVPCTR) */
147