cipher.c revision 1.75 
1/*
2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 *                    All rights reserved
5 *
6 * As far as I am concerned, the code I have written for this software
7 * can be used freely for any purpose.  Any derived versions of this
8 * software must be clearly marked as such, and if the derived work is
9 * incompatible with the protocol description in the RFC file, it must be
10 * called by a name other than "ssh" or "Secure Shell".
11 *
12 *
13 * Copyright (c) 1999 Niels Provos.  All rights reserved.
14 * Copyright (c) 1999, 2000 Markus Friedl.  All rights reserved.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 *    notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 *    notice, this list of conditions and the following disclaimer in the
23 *    documentation and/or other materials provided with the distribution.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35 */
36
37#include "includes.h"
38RCSID("$OpenBSD: cipher.c,v 1.75 2005/06/09 13:43:49 dtucker Exp $");
39
40#include "xmalloc.h"
41#include "log.h"
42#include "cipher.h"
43
44#include <openssl/md5.h>
45
46extern const EVP_CIPHER *evp_ssh1_bf(void);
47extern const EVP_CIPHER *evp_ssh1_3des(void);
48extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
49extern const EVP_CIPHER *evp_aes_128_ctr(void);
50extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
51
52struct Cipher {
53	char	*name;
54	int	number;		/* for ssh1 only */
55	u_int	block_size;
56	u_int	key_len;
57	u_int	discard_len;
58	const EVP_CIPHER	*(*evptype)(void);
59} ciphers[] = {
60	{ "none",		SSH_CIPHER_NONE, 8, 0, 0, EVP_enc_null },
61	{ "des",		SSH_CIPHER_DES, 8, 8, 0, EVP_des_cbc },
62	{ "3des",		SSH_CIPHER_3DES, 8, 16, 0, evp_ssh1_3des },
63	{ "blowfish",		SSH_CIPHER_BLOWFISH, 8, 32, 0, evp_ssh1_bf },
64
65	{ "3des-cbc",		SSH_CIPHER_SSH2, 8, 24, 0, EVP_des_ede3_cbc },
66	{ "blowfish-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, EVP_bf_cbc },
67	{ "cast128-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, EVP_cast5_cbc },
68	{ "arcfour",		SSH_CIPHER_SSH2, 8, 16, 0, EVP_rc4 },
69	{ "arcfour128",		SSH_CIPHER_SSH2, 8, 16, 1536, EVP_rc4 },
70	{ "arcfour256",		SSH_CIPHER_SSH2, 8, 32, 1536, EVP_rc4 },
71	{ "aes128-cbc",		SSH_CIPHER_SSH2, 16, 16, 0, EVP_aes_128_cbc },
72	{ "aes192-cbc",		SSH_CIPHER_SSH2, 16, 24, 0, EVP_aes_192_cbc },
73	{ "aes256-cbc",		SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc },
74	{ "rijndael-cbc@lysator.liu.se",
75				SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc },
76	{ "aes128-ctr",		SSH_CIPHER_SSH2, 16, 16, 0, evp_aes_128_ctr },
77	{ "aes192-ctr",		SSH_CIPHER_SSH2, 16, 24, 0, evp_aes_128_ctr },
78	{ "aes256-ctr",		SSH_CIPHER_SSH2, 16, 32, 0, evp_aes_128_ctr },
79	{ "acss@openssh.org",	SSH_CIPHER_SSH2, 16, 5, 0, EVP_acss },
80
81	{ NULL,			SSH_CIPHER_INVALID, 0, 0, 0, NULL }
82};
83
84/*--*/
85
86u_int
87cipher_blocksize(const Cipher *c)
88{
89	return (c->block_size);
90}
91
92u_int
93cipher_keylen(const Cipher *c)
94{
95	return (c->key_len);
96}
97
98u_int
99cipher_get_number(const Cipher *c)
100{
101	return (c->number);
102}
103
104u_int
105cipher_mask_ssh1(int client)
106{
107	u_int mask = 0;
108	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
109	mask |= 1 << SSH_CIPHER_BLOWFISH;
110	if (client) {
111		mask |= 1 << SSH_CIPHER_DES;
112	}
113	return mask;
114}
115
116Cipher *
117cipher_by_name(const char *name)
118{
119	Cipher *c;
120	for (c = ciphers; c->name != NULL; c++)
121		if (strcmp(c->name, name) == 0)
122			return c;
123	return NULL;
124}
125
126Cipher *
127cipher_by_number(int id)
128{
129	Cipher *c;
130	for (c = ciphers; c->name != NULL; c++)
131		if (c->number == id)
132			return c;
133	return NULL;
134}
135
136#define	CIPHER_SEP	","
137int
138ciphers_valid(const char *names)
139{
140	Cipher *c;
141	char *cipher_list, *cp;
142	char *p;
143
144	if (names == NULL || strcmp(names, "") == 0)
145		return 0;
146	cipher_list = cp = xstrdup(names);
147	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
148	    (p = strsep(&cp, CIPHER_SEP))) {
149		c = cipher_by_name(p);
150		if (c == NULL || c->number != SSH_CIPHER_SSH2) {
151			debug("bad cipher %s [%s]", p, names);
152			xfree(cipher_list);
153			return 0;
154		} else {
155			debug3("cipher ok: %s [%s]", p, names);
156		}
157	}
158	debug3("ciphers ok: [%s]", names);
159	xfree(cipher_list);
160	return 1;
161}
162
163/*
164 * Parses the name of the cipher.  Returns the number of the corresponding
165 * cipher, or -1 on error.
166 */
167
168int
169cipher_number(const char *name)
170{
171	Cipher *c;
172	if (name == NULL)
173		return -1;
174	for (c = ciphers; c->name != NULL; c++)
175		if (strcasecmp(c->name, name) == 0)
176			return c->number;
177	return -1;
178}
179
180char *
181cipher_name(int id)
182{
183	Cipher *c = cipher_by_number(id);
184	return (c==NULL) ? "<unknown>" : c->name;
185}
186
187void
188cipher_init(CipherContext *cc, Cipher *cipher,
189    const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
190    int do_encrypt)
191{
192	static int dowarn = 1;
193	const EVP_CIPHER *type;
194	int klen;
195	u_char *junk, *discard;
196
197	if (cipher->number == SSH_CIPHER_DES) {
198		if (dowarn) {
199			error("Warning: use of DES is strongly discouraged "
200			    "due to cryptographic weaknesses");
201			dowarn = 0;
202		}
203		if (keylen > 8)
204			keylen = 8;
205	}
206	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
207
208	if (keylen < cipher->key_len)
209		fatal("cipher_init: key length %d is insufficient for %s.",
210		    keylen, cipher->name);
211	if (iv != NULL && ivlen < cipher->block_size)
212		fatal("cipher_init: iv length %d is insufficient for %s.",
213		    ivlen, cipher->name);
214	cc->cipher = cipher;
215
216	type = (*cipher->evptype)();
217
218	EVP_CIPHER_CTX_init(&cc->evp);
219	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
220	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
221		fatal("cipher_init: EVP_CipherInit failed for %s",
222		    cipher->name);
223	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
224	if (klen > 0 && keylen != klen) {
225		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
226		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
227			fatal("cipher_init: set keylen failed (%d -> %d)",
228			    klen, keylen);
229	}
230	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
231		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
232		    cipher->name);
233
234	if (cipher->discard_len > 0) {
235		junk = xmalloc(cipher->discard_len);
236		discard = xmalloc(cipher->discard_len);
237		if (EVP_Cipher(&cc->evp, discard, junk,
238		    cipher->discard_len) == 0)
239			fatal("evp_crypt: EVP_Cipher failed during discard");
240		memset(discard, 0, cipher->discard_len);
241		xfree(junk);
242		xfree(discard);
243	}
244}
245
246void
247cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
248{
249	if (len % cc->cipher->block_size)
250		fatal("cipher_encrypt: bad plaintext length %d", len);
251	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
252		fatal("evp_crypt: EVP_Cipher failed");
253}
254
255void
256cipher_cleanup(CipherContext *cc)
257{
258	if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
259		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
260}
261
262/*
263 * Selects the cipher, and keys if by computing the MD5 checksum of the
264 * passphrase and using the resulting 16 bytes as the key.
265 */
266
267void
268cipher_set_key_string(CipherContext *cc, Cipher *cipher,
269    const char *passphrase, int do_encrypt)
270{
271	MD5_CTX md;
272	u_char digest[16];
273
274	MD5_Init(&md);
275	MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
276	MD5_Final(digest, &md);
277
278	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
279
280	memset(digest, 0, sizeof(digest));
281	memset(&md, 0, sizeof(md));
282}
283
284/*
285 * Exports an IV from the CipherContext required to export the key
286 * state back from the unprivileged child to the privileged parent
287 * process.
288 */
289
290int
291cipher_get_keyiv_len(const CipherContext *cc)
292{
293	Cipher *c = cc->cipher;
294	int ivlen;
295
296	if (c->number == SSH_CIPHER_3DES)
297		ivlen = 24;
298	else
299		ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
300	return (ivlen);
301}
302
303void
304cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
305{
306	Cipher *c = cc->cipher;
307	int evplen;
308
309	switch (c->number) {
310	case SSH_CIPHER_SSH2:
311	case SSH_CIPHER_DES:
312	case SSH_CIPHER_BLOWFISH:
313		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
314		if (evplen == 0)
315			return;
316		if (evplen != len)
317			fatal("%s: wrong iv length %d != %d", __func__,
318			    evplen, len);
319		if (c->evptype == evp_aes_128_ctr)
320			ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
321		else
322			memcpy(iv, cc->evp.iv, len);
323		break;
324	case SSH_CIPHER_3DES:
325		ssh1_3des_iv(&cc->evp, 0, iv, 24);
326		break;
327	default:
328		fatal("%s: bad cipher %d", __func__, c->number);
329	}
330}
331
332void
333cipher_set_keyiv(CipherContext *cc, u_char *iv)
334{
335	Cipher *c = cc->cipher;
336	int evplen = 0;
337
338	switch (c->number) {
339	case SSH_CIPHER_SSH2:
340	case SSH_CIPHER_DES:
341	case SSH_CIPHER_BLOWFISH:
342		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
343		if (evplen == 0)
344			return;
345		if (c->evptype == evp_aes_128_ctr)
346			ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
347		else
348			memcpy(cc->evp.iv, iv, evplen);
349		break;
350	case SSH_CIPHER_3DES:
351		ssh1_3des_iv(&cc->evp, 1, iv, 24);
352		break;
353	default:
354		fatal("%s: bad cipher %d", __func__, c->number);
355	}
356}
357
358#define EVP_X_STATE(evp)	(evp).cipher_data
359#define EVP_X_STATE_LEN(evp)	(evp).cipher->ctx_size
360
361int
362cipher_get_keycontext(const CipherContext *cc, u_char *dat)
363{
364	Cipher *c = cc->cipher;
365	int plen = 0;
366
367	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
368		plen = EVP_X_STATE_LEN(cc->evp);
369		if (dat == NULL)
370			return (plen);
371		memcpy(dat, EVP_X_STATE(cc->evp), plen);
372	}
373	return (plen);
374}
375
376void
377cipher_set_keycontext(CipherContext *cc, u_char *dat)
378{
379	Cipher *c = cc->cipher;
380	int plen;
381
382	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
383		plen = EVP_X_STATE_LEN(cc->evp);
384		memcpy(EVP_X_STATE(cc->evp), dat, plen);
385	}
386}
387