1/* $OpenBSD: cipher.c,v 1.82 2009/01/26 09:58:15 markus Exp $ */
2/*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 *                    All rights reserved
6 *
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose.  Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
12 *
13 *
14 * Copyright (c) 1999 Niels Provos.  All rights reserved.
15 * Copyright (c) 1999, 2000 Markus Friedl.  All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 *    notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 *    notice, this list of conditions and the following disclaimer in the
24 *    documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 */
37
38#include "includes.h"
39
40#include <sys/types.h>
41
42#include <openssl/md5.h>
43
44#include <string.h>
45#include <stdarg.h>
46
47#include "xmalloc.h"
48#include "log.h"
49#include "cipher.h"
50
51/* compatibility with old or broken OpenSSL versions */
52#include "openbsd-compat/openssl-compat.h"
53
54extern const EVP_CIPHER *evp_ssh1_bf(void);
55extern const EVP_CIPHER *evp_ssh1_3des(void);
56extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
57extern const EVP_CIPHER *evp_aes_128_ctr(void);
58extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
59
60struct Cipher {
61	char	*name;
62	int	number;		/* for ssh1 only */
63	u_int	block_size;
64	u_int	key_len;
65	u_int	discard_len;
66	u_int	cbc_mode;
67	const EVP_CIPHER	*(*evptype)(void);
68} ciphers[] = {
69	{ "none",		SSH_CIPHER_NONE, 8, 0, 0, 0, EVP_enc_null },
70	{ "des",		SSH_CIPHER_DES, 8, 8, 0, 1, EVP_des_cbc },
71	{ "3des",		SSH_CIPHER_3DES, 8, 16, 0, 1, evp_ssh1_3des },
72	{ "blowfish",		SSH_CIPHER_BLOWFISH, 8, 32, 0, 1, evp_ssh1_bf },
73
74	{ "3des-cbc",		SSH_CIPHER_SSH2, 8, 24, 0, 1, EVP_des_ede3_cbc },
75	{ "blowfish-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_bf_cbc },
76#ifndef ANDROID
77	{ "cast128-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_cast5_cbc },
78#endif
79	{ "arcfour",		SSH_CIPHER_SSH2, 8, 16, 0, 0, EVP_rc4 },
80	{ "arcfour128",		SSH_CIPHER_SSH2, 8, 16, 1536, 0, EVP_rc4 },
81	{ "arcfour256",		SSH_CIPHER_SSH2, 8, 32, 1536, 0, EVP_rc4 },
82	{ "aes128-cbc",		SSH_CIPHER_SSH2, 16, 16, 0, 1, EVP_aes_128_cbc },
83	{ "aes192-cbc",		SSH_CIPHER_SSH2, 16, 24, 0, 1, EVP_aes_192_cbc },
84	{ "aes256-cbc",		SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
85	{ "rijndael-cbc@lysator.liu.se",
86				SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
87	{ "aes128-ctr",		SSH_CIPHER_SSH2, 16, 16, 0, 0, evp_aes_128_ctr },
88	{ "aes192-ctr",		SSH_CIPHER_SSH2, 16, 24, 0, 0, evp_aes_128_ctr },
89	{ "aes256-ctr",		SSH_CIPHER_SSH2, 16, 32, 0, 0, evp_aes_128_ctr },
90#ifdef USE_CIPHER_ACSS
91	{ "acss@openssh.org",	SSH_CIPHER_SSH2, 16, 5, 0, 0, EVP_acss },
92#endif
93	{ NULL,			SSH_CIPHER_INVALID, 0, 0, 0, 0, NULL }
94};
95
96/*--*/
97
98u_int
99cipher_blocksize(const Cipher *c)
100{
101	return (c->block_size);
102}
103
104u_int
105cipher_keylen(const Cipher *c)
106{
107	return (c->key_len);
108}
109
110u_int
111cipher_get_number(const Cipher *c)
112{
113	return (c->number);
114}
115
116u_int
117cipher_is_cbc(const Cipher *c)
118{
119	return (c->cbc_mode);
120}
121
122u_int
123cipher_mask_ssh1(int client)
124{
125	u_int mask = 0;
126	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
127	mask |= 1 << SSH_CIPHER_BLOWFISH;
128	if (client) {
129		mask |= 1 << SSH_CIPHER_DES;
130	}
131	return mask;
132}
133
134Cipher *
135cipher_by_name(const char *name)
136{
137	Cipher *c;
138	for (c = ciphers; c->name != NULL; c++)
139		if (strcmp(c->name, name) == 0)
140			return c;
141	return NULL;
142}
143
144Cipher *
145cipher_by_number(int id)
146{
147	Cipher *c;
148	for (c = ciphers; c->name != NULL; c++)
149		if (c->number == id)
150			return c;
151	return NULL;
152}
153
154#define	CIPHER_SEP	","
155int
156ciphers_valid(const char *names)
157{
158	Cipher *c;
159	char *cipher_list, *cp;
160	char *p;
161
162	if (names == NULL || strcmp(names, "") == 0)
163		return 0;
164	cipher_list = cp = xstrdup(names);
165	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
166	    (p = strsep(&cp, CIPHER_SEP))) {
167		c = cipher_by_name(p);
168		if (c == NULL || c->number != SSH_CIPHER_SSH2) {
169			debug("bad cipher %s [%s]", p, names);
170			xfree(cipher_list);
171			return 0;
172		} else {
173			debug3("cipher ok: %s [%s]", p, names);
174		}
175	}
176	debug3("ciphers ok: [%s]", names);
177	xfree(cipher_list);
178	return 1;
179}
180
181/*
182 * Parses the name of the cipher.  Returns the number of the corresponding
183 * cipher, or -1 on error.
184 */
185
186int
187cipher_number(const char *name)
188{
189	Cipher *c;
190	if (name == NULL)
191		return -1;
192	for (c = ciphers; c->name != NULL; c++)
193		if (strcasecmp(c->name, name) == 0)
194			return c->number;
195	return -1;
196}
197
198char *
199cipher_name(int id)
200{
201	Cipher *c = cipher_by_number(id);
202	return (c==NULL) ? "<unknown>" : c->name;
203}
204
205void
206cipher_init(CipherContext *cc, Cipher *cipher,
207    const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
208    int do_encrypt)
209{
210	static int dowarn = 1;
211#ifdef SSH_OLD_EVP
212	EVP_CIPHER *type;
213#else
214	const EVP_CIPHER *type;
215	int klen;
216#endif
217	u_char *junk, *discard;
218
219	if (cipher->number == SSH_CIPHER_DES) {
220		if (dowarn) {
221			error("Warning: use of DES is strongly discouraged "
222			    "due to cryptographic weaknesses");
223			dowarn = 0;
224		}
225		if (keylen > 8)
226			keylen = 8;
227	}
228	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
229
230	if (keylen < cipher->key_len)
231		fatal("cipher_init: key length %d is insufficient for %s.",
232		    keylen, cipher->name);
233	if (iv != NULL && ivlen < cipher->block_size)
234		fatal("cipher_init: iv length %d is insufficient for %s.",
235		    ivlen, cipher->name);
236	cc->cipher = cipher;
237
238	type = (*cipher->evptype)();
239
240	EVP_CIPHER_CTX_init(&cc->evp);
241#ifdef SSH_OLD_EVP
242	if (type->key_len > 0 && type->key_len != keylen) {
243		debug("cipher_init: set keylen (%d -> %d)",
244		    type->key_len, keylen);
245		type->key_len = keylen;
246	}
247	EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
248	    (do_encrypt == CIPHER_ENCRYPT));
249#else
250	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
251	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
252		fatal("cipher_init: EVP_CipherInit failed for %s",
253		    cipher->name);
254	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
255	if (klen > 0 && keylen != (u_int)klen) {
256		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
257		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
258			fatal("cipher_init: set keylen failed (%d -> %d)",
259			    klen, keylen);
260	}
261	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
262		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
263		    cipher->name);
264#endif
265
266	if (cipher->discard_len > 0) {
267		junk = xmalloc(cipher->discard_len);
268		discard = xmalloc(cipher->discard_len);
269		if (EVP_Cipher(&cc->evp, discard, junk,
270		    cipher->discard_len) == 0)
271			fatal("evp_crypt: EVP_Cipher failed during discard");
272		memset(discard, 0, cipher->discard_len);
273		xfree(junk);
274		xfree(discard);
275	}
276}
277
278void
279cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
280{
281	if (len % cc->cipher->block_size)
282		fatal("cipher_encrypt: bad plaintext length %d", len);
283	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
284		fatal("evp_crypt: EVP_Cipher failed");
285}
286
287void
288cipher_cleanup(CipherContext *cc)
289{
290	if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
291		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
292}
293
294/*
295 * Selects the cipher, and keys if by computing the MD5 checksum of the
296 * passphrase and using the resulting 16 bytes as the key.
297 */
298
299void
300cipher_set_key_string(CipherContext *cc, Cipher *cipher,
301    const char *passphrase, int do_encrypt)
302{
303	MD5_CTX md;
304	u_char digest[16];
305
306	MD5_Init(&md);
307	MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
308	MD5_Final(digest, &md);
309
310	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
311
312	memset(digest, 0, sizeof(digest));
313	memset(&md, 0, sizeof(md));
314}
315
316/*
317 * Exports an IV from the CipherContext required to export the key
318 * state back from the unprivileged child to the privileged parent
319 * process.
320 */
321
322int
323cipher_get_keyiv_len(const CipherContext *cc)
324{
325	Cipher *c = cc->cipher;
326	int ivlen;
327
328	if (c->number == SSH_CIPHER_3DES)
329		ivlen = 24;
330	else
331		ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
332	return (ivlen);
333}
334
335void
336cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
337{
338	Cipher *c = cc->cipher;
339	int evplen;
340
341	switch (c->number) {
342	case SSH_CIPHER_SSH2:
343	case SSH_CIPHER_DES:
344	case SSH_CIPHER_BLOWFISH:
345		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
346		if (evplen <= 0)
347			return;
348		if ((u_int)evplen != len)
349			fatal("%s: wrong iv length %d != %d", __func__,
350			    evplen, len);
351#ifdef USE_BUILTIN_RIJNDAEL
352		if (c->evptype == evp_rijndael)
353			ssh_rijndael_iv(&cc->evp, 0, iv, len);
354		else
355#endif
356		if (c->evptype == evp_aes_128_ctr)
357			ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
358		else
359			memcpy(iv, cc->evp.iv, len);
360		break;
361	case SSH_CIPHER_3DES:
362		ssh1_3des_iv(&cc->evp, 0, iv, 24);
363		break;
364	default:
365		fatal("%s: bad cipher %d", __func__, c->number);
366	}
367}
368
369void
370cipher_set_keyiv(CipherContext *cc, u_char *iv)
371{
372	Cipher *c = cc->cipher;
373	int evplen = 0;
374
375	switch (c->number) {
376	case SSH_CIPHER_SSH2:
377	case SSH_CIPHER_DES:
378	case SSH_CIPHER_BLOWFISH:
379		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
380		if (evplen == 0)
381			return;
382#ifdef USE_BUILTIN_RIJNDAEL
383		if (c->evptype == evp_rijndael)
384			ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
385		else
386#endif
387		if (c->evptype == evp_aes_128_ctr)
388			ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
389		else
390			memcpy(cc->evp.iv, iv, evplen);
391		break;
392	case SSH_CIPHER_3DES:
393		ssh1_3des_iv(&cc->evp, 1, iv, 24);
394		break;
395	default:
396		fatal("%s: bad cipher %d", __func__, c->number);
397	}
398}
399
400#if OPENSSL_VERSION_NUMBER < 0x00907000L
401#define EVP_X_STATE(evp)	&(evp).c
402#define EVP_X_STATE_LEN(evp)	sizeof((evp).c)
403#else
404#define EVP_X_STATE(evp)	(evp).cipher_data
405#define EVP_X_STATE_LEN(evp)	(evp).cipher->ctx_size
406#endif
407
408int
409cipher_get_keycontext(const CipherContext *cc, u_char *dat)
410{
411	Cipher *c = cc->cipher;
412	int plen = 0;
413
414	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
415		plen = EVP_X_STATE_LEN(cc->evp);
416		if (dat == NULL)
417			return (plen);
418		memcpy(dat, EVP_X_STATE(cc->evp), plen);
419	}
420	return (plen);
421}
422
423void
424cipher_set_keycontext(CipherContext *cc, u_char *dat)
425{
426	Cipher *c = cc->cipher;
427	int plen;
428
429	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
430		plen = EVP_X_STATE_LEN(cc->evp);
431		memcpy(EVP_X_STATE(cc->evp), dat, plen);
432	}
433}
434