1/* $OpenBSD: cipher.c,v 1.89 2013/05/17 00:13:13 djm Exp $ */
2/* $FreeBSD$ */
3/*
4 * Author: Tatu Ylonen <ylo@cs.hut.fi>
5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 *                    All rights reserved
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose.  Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 *
14 *
15 * Copyright (c) 1999 Niels Provos.  All rights reserved.
16 * Copyright (c) 1999, 2000 Markus Friedl.  All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
20 * are met:
21 * 1. Redistributions of source code must retain the above copyright
22 *    notice, this list of conditions and the following disclaimer.
23 * 2. Redistributions in binary form must reproduce the above copyright
24 *    notice, this list of conditions and the following disclaimer in the
25 *    documentation and/or other materials provided with the distribution.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 */
38
39#include "includes.h"
40
41#include <sys/types.h>
42
43#include <openssl/md5.h>
44
45#include <string.h>
46#include <stdarg.h>
47
48#include "xmalloc.h"
49#include "log.h"
50#include "cipher.h"
51
52/* compatibility with old or broken OpenSSL versions */
53#include "openbsd-compat/openssl-compat.h"
54
55extern const EVP_CIPHER *evp_ssh1_bf(void);
56extern const EVP_CIPHER *evp_ssh1_3des(void);
57extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
58
59struct Cipher {
60	char	*name;
61	int	number;		/* for ssh1 only */
62	u_int	block_size;
63	u_int	key_len;
64	u_int	iv_len;		/* defaults to block_size */
65	u_int	auth_len;
66	u_int	discard_len;
67	u_int	cbc_mode;
68	const EVP_CIPHER	*(*evptype)(void);
69};
70
71static const struct Cipher ciphers[] = {
72	{ "none",	SSH_CIPHER_NONE, 8, 0, 0, 0, 0, 0, EVP_enc_null },
73	{ "des",	SSH_CIPHER_DES, 8, 8, 0, 0, 0, 1, EVP_des_cbc },
74	{ "3des",	SSH_CIPHER_3DES, 8, 16, 0, 0, 0, 1, evp_ssh1_3des },
75	{ "blowfish",	SSH_CIPHER_BLOWFISH, 8, 32, 0, 0, 0, 1, evp_ssh1_bf },
76
77	{ "3des-cbc",	SSH_CIPHER_SSH2, 8, 24, 0, 0, 0, 1, EVP_des_ede3_cbc },
78	{ "blowfish-cbc",
79			SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_bf_cbc },
80	{ "cast128-cbc",
81			SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_cast5_cbc },
82	{ "arcfour",	SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 0, EVP_rc4 },
83	{ "arcfour128",	SSH_CIPHER_SSH2, 8, 16, 0, 0, 1536, 0, EVP_rc4 },
84	{ "arcfour256",	SSH_CIPHER_SSH2, 8, 32, 0, 0, 1536, 0, EVP_rc4 },
85	{ "aes128-cbc",	SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 1, EVP_aes_128_cbc },
86	{ "aes192-cbc",	SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 1, EVP_aes_192_cbc },
87	{ "aes256-cbc",	SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc },
88	{ "rijndael-cbc@lysator.liu.se",
89			SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc },
90	{ "aes128-ctr",	SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 0, EVP_aes_128_ctr },
91	{ "aes192-ctr",	SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 0, EVP_aes_192_ctr },
92	{ "aes256-ctr",	SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 0, EVP_aes_256_ctr },
93#ifdef OPENSSL_HAVE_EVPGCM
94	{ "aes128-gcm@openssh.com",
95			SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm },
96	{ "aes256-gcm@openssh.com",
97			SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm },
98#endif
99	{ NULL,		SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL }
100};
101
102/*--*/
103
104/* Returns a comma-separated list of supported ciphers. */
105char *
106cipher_alg_list(void)
107{
108	char *ret = NULL;
109	size_t nlen, rlen = 0;
110	const Cipher *c;
111
112	for (c = ciphers; c->name != NULL; c++) {
113		if (c->number != SSH_CIPHER_SSH2)
114			continue;
115		if (ret != NULL)
116			ret[rlen++] = '\n';
117		nlen = strlen(c->name);
118		ret = xrealloc(ret, 1, rlen + nlen + 2);
119		memcpy(ret + rlen, c->name, nlen + 1);
120		rlen += nlen;
121	}
122	return ret;
123}
124
125u_int
126cipher_blocksize(const Cipher *c)
127{
128	return (c->block_size);
129}
130
131u_int
132cipher_keylen(const Cipher *c)
133{
134	return (c->key_len);
135}
136
137u_int
138cipher_authlen(const Cipher *c)
139{
140	return (c->auth_len);
141}
142
143u_int
144cipher_ivlen(const Cipher *c)
145{
146	return (c->iv_len ? c->iv_len : c->block_size);
147}
148
149u_int
150cipher_get_number(const Cipher *c)
151{
152	return (c->number);
153}
154
155u_int
156cipher_is_cbc(const Cipher *c)
157{
158	return (c->cbc_mode);
159}
160
161u_int
162cipher_mask_ssh1(int client)
163{
164	u_int mask = 0;
165	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
166	mask |= 1 << SSH_CIPHER_BLOWFISH;
167	if (client) {
168		mask |= 1 << SSH_CIPHER_DES;
169	}
170	return mask;
171}
172
173const Cipher *
174cipher_by_name(const char *name)
175{
176	const Cipher *c;
177	for (c = ciphers; c->name != NULL; c++)
178		if (strcmp(c->name, name) == 0)
179			return c;
180	return NULL;
181}
182
183const Cipher *
184cipher_by_number(int id)
185{
186	const Cipher *c;
187	for (c = ciphers; c->name != NULL; c++)
188		if (c->number == id)
189			return c;
190	return NULL;
191}
192
193#define	CIPHER_SEP	","
194int
195ciphers_valid(const char *names)
196{
197	const Cipher *c;
198	char *cipher_list, *cp;
199	char *p;
200
201	if (names == NULL || strcmp(names, "") == 0)
202		return 0;
203	cipher_list = cp = xstrdup(names);
204	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
205	    (p = strsep(&cp, CIPHER_SEP))) {
206		c = cipher_by_name(p);
207#ifdef NONE_CIPHER_ENABLED
208		if (c == NULL || (c->number != SSH_CIPHER_SSH2 &&
209		    c->number != SSH_CIPHER_NONE)) {
210#else
211		if (c == NULL || (c->number != SSH_CIPHER_SSH2)) {
212#endif
213			debug("bad cipher %s [%s]", p, names);
214			free(cipher_list);
215			return 0;
216		} else {
217			debug3("cipher ok: %s [%s]", p, names);
218		}
219	}
220	debug3("ciphers ok: [%s]", names);
221	free(cipher_list);
222	return 1;
223}
224
225/*
226 * Parses the name of the cipher.  Returns the number of the corresponding
227 * cipher, or -1 on error.
228 */
229
230int
231cipher_number(const char *name)
232{
233	const Cipher *c;
234	if (name == NULL)
235		return -1;
236	for (c = ciphers; c->name != NULL; c++)
237		if (strcasecmp(c->name, name) == 0)
238			return c->number;
239	return -1;
240}
241
242char *
243cipher_name(int id)
244{
245	const Cipher *c = cipher_by_number(id);
246	return (c==NULL) ? "<unknown>" : c->name;
247}
248
249void
250cipher_init(CipherContext *cc, const Cipher *cipher,
251    const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
252    int do_encrypt)
253{
254	static int dowarn = 1;
255#ifdef SSH_OLD_EVP
256	EVP_CIPHER *type;
257#else
258	const EVP_CIPHER *type;
259	int klen;
260#endif
261	u_char *junk, *discard;
262
263	if (cipher->number == SSH_CIPHER_DES) {
264		if (dowarn) {
265			error("Warning: use of DES is strongly discouraged "
266			    "due to cryptographic weaknesses");
267			dowarn = 0;
268		}
269		if (keylen > 8)
270			keylen = 8;
271	}
272	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
273	cc->encrypt = do_encrypt;
274
275	if (keylen < cipher->key_len)
276		fatal("cipher_init: key length %d is insufficient for %s.",
277		    keylen, cipher->name);
278	if (iv != NULL && ivlen < cipher_ivlen(cipher))
279		fatal("cipher_init: iv length %d is insufficient for %s.",
280		    ivlen, cipher->name);
281	cc->cipher = cipher;
282
283	type = (*cipher->evptype)();
284
285	EVP_CIPHER_CTX_init(&cc->evp);
286#ifdef SSH_OLD_EVP
287	if (type->key_len > 0 && type->key_len != keylen) {
288		debug("cipher_init: set keylen (%d -> %d)",
289		    type->key_len, keylen);
290		type->key_len = keylen;
291	}
292	EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
293	    (do_encrypt == CIPHER_ENCRYPT));
294#else
295	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
296	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
297		fatal("cipher_init: EVP_CipherInit failed for %s",
298		    cipher->name);
299	if (cipher_authlen(cipher) &&
300	    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
301	    -1, (u_char *)iv))
302		fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s",
303		    cipher->name);
304	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
305	if (klen > 0 && keylen != (u_int)klen) {
306		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
307		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
308			fatal("cipher_init: set keylen failed (%d -> %d)",
309			    klen, keylen);
310	}
311	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
312		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
313		    cipher->name);
314#endif
315
316	if (cipher->discard_len > 0) {
317		junk = xmalloc(cipher->discard_len);
318		discard = xmalloc(cipher->discard_len);
319		if (EVP_Cipher(&cc->evp, discard, junk,
320		    cipher->discard_len) == 0)
321			fatal("evp_crypt: EVP_Cipher failed during discard");
322		memset(discard, 0, cipher->discard_len);
323		free(junk);
324		free(discard);
325	}
326}
327
328/*
329 * cipher_crypt() operates as following:
330 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
331 * Theses bytes are treated as additional authenticated data for
332 * authenticated encryption modes.
333 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
334 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
335 * This tag is written on encryption and verified on decryption.
336 * Both 'aadlen' and 'authlen' can be set to 0.
337 */
338void
339cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src,
340    u_int len, u_int aadlen, u_int authlen)
341{
342	if (authlen) {
343		u_char lastiv[1];
344
345		if (authlen != cipher_authlen(cc->cipher))
346			fatal("%s: authlen mismatch %d", __func__, authlen);
347		/* increment IV */
348		if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN,
349		    1, lastiv))
350			fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__);
351		/* set tag on decyption */
352		if (!cc->encrypt &&
353		    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG,
354		    authlen, (u_char *)src + aadlen + len))
355			fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__);
356	}
357	if (aadlen) {
358		if (authlen &&
359		    EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0)
360			fatal("%s: EVP_Cipher(aad) failed", __func__);
361		memcpy(dest, src, aadlen);
362	}
363	if (len % cc->cipher->block_size)
364		fatal("%s: bad plaintext length %d", __func__, len);
365	if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen,
366	    len) < 0)
367		fatal("%s: EVP_Cipher failed", __func__);
368	if (authlen) {
369		/* compute tag (on encrypt) or verify tag (on decrypt) */
370		if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) {
371			if (cc->encrypt)
372				fatal("%s: EVP_Cipher(final) failed", __func__);
373			else
374				fatal("Decryption integrity check failed");
375		}
376		if (cc->encrypt &&
377		    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG,
378		    authlen, dest + aadlen + len))
379			fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__);
380	}
381}
382
383void
384cipher_cleanup(CipherContext *cc)
385{
386	if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
387		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
388}
389
390/*
391 * Selects the cipher, and keys if by computing the MD5 checksum of the
392 * passphrase and using the resulting 16 bytes as the key.
393 */
394
395void
396cipher_set_key_string(CipherContext *cc, const Cipher *cipher,
397    const char *passphrase, int do_encrypt)
398{
399	MD5_CTX md;
400	u_char digest[16];
401
402	MD5_Init(&md);
403	MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
404	MD5_Final(digest, &md);
405
406	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
407
408	memset(digest, 0, sizeof(digest));
409	memset(&md, 0, sizeof(md));
410}
411
412/*
413 * Exports an IV from the CipherContext required to export the key
414 * state back from the unprivileged child to the privileged parent
415 * process.
416 */
417
418int
419cipher_get_keyiv_len(const CipherContext *cc)
420{
421	const Cipher *c = cc->cipher;
422	int ivlen;
423
424	if (c->number == SSH_CIPHER_3DES)
425		ivlen = 24;
426	else
427		ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
428	return (ivlen);
429}
430
431void
432cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
433{
434	const Cipher *c = cc->cipher;
435	int evplen;
436
437	switch (c->number) {
438#ifdef	NONE_CIPHER_ENABLED
439	case SSH_CIPHER_NONE:
440#endif
441	case SSH_CIPHER_SSH2:
442	case SSH_CIPHER_DES:
443	case SSH_CIPHER_BLOWFISH:
444		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
445		if (evplen <= 0)
446			return;
447		if ((u_int)evplen != len)
448			fatal("%s: wrong iv length %d != %d", __func__,
449			    evplen, len);
450#ifdef USE_BUILTIN_RIJNDAEL
451		if (c->evptype == evp_rijndael)
452			ssh_rijndael_iv(&cc->evp, 0, iv, len);
453		else
454#endif
455#ifndef OPENSSL_HAVE_EVPCTR
456		if (c->evptype == evp_aes_128_ctr)
457			ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
458		else
459#endif
460		memcpy(iv, cc->evp.iv, len);
461		break;
462	case SSH_CIPHER_3DES:
463		ssh1_3des_iv(&cc->evp, 0, iv, 24);
464		break;
465	default:
466		fatal("%s: bad cipher %d", __func__, c->number);
467	}
468}
469
470void
471cipher_set_keyiv(CipherContext *cc, u_char *iv)
472{
473	const Cipher *c = cc->cipher;
474	int evplen = 0;
475
476	switch (c->number) {
477#ifdef	NONE_CIPHER_ENABLED
478	case SSH_CIPHER_NONE:
479#endif
480	case SSH_CIPHER_SSH2:
481	case SSH_CIPHER_DES:
482	case SSH_CIPHER_BLOWFISH:
483		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
484		if (evplen == 0)
485			return;
486#ifdef USE_BUILTIN_RIJNDAEL
487		if (c->evptype == evp_rijndael)
488			ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
489		else
490#endif
491#ifndef OPENSSL_HAVE_EVPCTR
492		if (c->evptype == evp_aes_128_ctr)
493			ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
494		else
495#endif
496		memcpy(cc->evp.iv, iv, evplen);
497		break;
498	case SSH_CIPHER_3DES:
499		ssh1_3des_iv(&cc->evp, 1, iv, 24);
500		break;
501	default:
502		fatal("%s: bad cipher %d", __func__, c->number);
503	}
504}
505
506int
507cipher_get_keycontext(const CipherContext *cc, u_char *dat)
508{
509	const Cipher *c = cc->cipher;
510	int plen = 0;
511
512	if (c->evptype == EVP_rc4) {
513		plen = EVP_X_STATE_LEN(cc->evp);
514		if (dat == NULL)
515			return (plen);
516		memcpy(dat, EVP_X_STATE(cc->evp), plen);
517	}
518	return (plen);
519}
520
521void
522cipher_set_keycontext(CipherContext *cc, u_char *dat)
523{
524	const Cipher *c = cc->cipher;
525	int plen;
526
527	if (c->evptype == EVP_rc4) {
528		plen = EVP_X_STATE_LEN(cc->evp);
529		memcpy(EVP_X_STATE(cc->evp), dat, plen);
530	}
531}
532