cipher.c revision 264377 
1/* $OpenBSD: cipher.c,v 1.97 2014/02/07 06:55:54 djm Exp $ */
2/* $FreeBSD: stable/10/crypto/openssh/cipher.c 264377 2014-04-12 20:22:59Z des $ */
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 <string.h>
44#include <stdarg.h>
45#include <stdio.h>
46
47#include "xmalloc.h"
48#include "log.h"
49#include "misc.h"
50#include "cipher.h"
51#include "buffer.h"
52#include "digest.h"
53
54/* compatibility with old or broken OpenSSL versions */
55#include "openbsd-compat/openssl-compat.h"
56
57extern const EVP_CIPHER *evp_ssh1_bf(void);
58extern const EVP_CIPHER *evp_ssh1_3des(void);
59extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
60
61struct Cipher {
62	char	*name;
63	int	number;		/* for ssh1 only */
64	u_int	block_size;
65	u_int	key_len;
66	u_int	iv_len;		/* defaults to block_size */
67	u_int	auth_len;
68	u_int	discard_len;
69	u_int	flags;
70#define CFLAG_CBC		(1<<0)
71#define CFLAG_CHACHAPOLY	(1<<1)
72	const EVP_CIPHER	*(*evptype)(void);
73};
74
75static const struct Cipher ciphers[] = {
76	{ "none",	SSH_CIPHER_NONE, 8, 0, 0, 0, 0, 0, EVP_enc_null },
77	{ "des",	SSH_CIPHER_DES, 8, 8, 0, 0, 0, 1, EVP_des_cbc },
78	{ "3des",	SSH_CIPHER_3DES, 8, 16, 0, 0, 0, 1, evp_ssh1_3des },
79	{ "blowfish",	SSH_CIPHER_BLOWFISH, 8, 32, 0, 0, 0, 1, evp_ssh1_bf },
80
81	{ "3des-cbc",	SSH_CIPHER_SSH2, 8, 24, 0, 0, 0, 1, EVP_des_ede3_cbc },
82	{ "blowfish-cbc",
83			SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_bf_cbc },
84	{ "cast128-cbc",
85			SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_cast5_cbc },
86	{ "arcfour",	SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 0, EVP_rc4 },
87	{ "arcfour128",	SSH_CIPHER_SSH2, 8, 16, 0, 0, 1536, 0, EVP_rc4 },
88	{ "arcfour256",	SSH_CIPHER_SSH2, 8, 32, 0, 0, 1536, 0, EVP_rc4 },
89	{ "aes128-cbc",	SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 1, EVP_aes_128_cbc },
90	{ "aes192-cbc",	SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 1, EVP_aes_192_cbc },
91	{ "aes256-cbc",	SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc },
92	{ "rijndael-cbc@lysator.liu.se",
93			SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc },
94	{ "aes128-ctr",	SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 0, EVP_aes_128_ctr },
95	{ "aes192-ctr",	SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 0, EVP_aes_192_ctr },
96	{ "aes256-ctr",	SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 0, EVP_aes_256_ctr },
97#ifdef OPENSSL_HAVE_EVPGCM
98	{ "aes128-gcm@openssh.com",
99			SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm },
100	{ "aes256-gcm@openssh.com",
101			SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm },
102#endif
103	{ "chacha20-poly1305@openssh.com",
104			SSH_CIPHER_SSH2, 8, 64, 0, 16, 0, CFLAG_CHACHAPOLY, NULL },
105	{ NULL,		SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL }
106};
107
108/*--*/
109
110/* Returns a list of supported ciphers separated by the specified char. */
111char *
112cipher_alg_list(char sep, int auth_only)
113{
114	char *ret = NULL;
115	size_t nlen, rlen = 0;
116	const Cipher *c;
117
118	for (c = ciphers; c->name != NULL; c++) {
119		if (c->number != SSH_CIPHER_SSH2)
120			continue;
121		if (auth_only && c->auth_len == 0)
122			continue;
123		if (ret != NULL)
124			ret[rlen++] = sep;
125		nlen = strlen(c->name);
126		ret = xrealloc(ret, 1, rlen + nlen + 2);
127		memcpy(ret + rlen, c->name, nlen + 1);
128		rlen += nlen;
129	}
130	return ret;
131}
132
133u_int
134cipher_blocksize(const Cipher *c)
135{
136	return (c->block_size);
137}
138
139u_int
140cipher_keylen(const Cipher *c)
141{
142	return (c->key_len);
143}
144
145u_int
146cipher_seclen(const Cipher *c)
147{
148	if (strcmp("3des-cbc", c->name) == 0)
149		return 14;
150	return cipher_keylen(c);
151}
152
153u_int
154cipher_authlen(const Cipher *c)
155{
156	return (c->auth_len);
157}
158
159u_int
160cipher_ivlen(const Cipher *c)
161{
162	/*
163	 * Default is cipher block size, except for chacha20+poly1305 that
164	 * needs no IV. XXX make iv_len == -1 default?
165	 */
166	return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ?
167	    c->iv_len : c->block_size;
168}
169
170u_int
171cipher_get_number(const Cipher *c)
172{
173	return (c->number);
174}
175
176u_int
177cipher_is_cbc(const Cipher *c)
178{
179	return (c->flags & CFLAG_CBC) != 0;
180}
181
182u_int
183cipher_mask_ssh1(int client)
184{
185	u_int mask = 0;
186	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
187	mask |= 1 << SSH_CIPHER_BLOWFISH;
188	if (client) {
189		mask |= 1 << SSH_CIPHER_DES;
190	}
191	return mask;
192}
193
194const Cipher *
195cipher_by_name(const char *name)
196{
197	const Cipher *c;
198	for (c = ciphers; c->name != NULL; c++)
199		if (strcmp(c->name, name) == 0)
200			return c;
201	return NULL;
202}
203
204const Cipher *
205cipher_by_number(int id)
206{
207	const Cipher *c;
208	for (c = ciphers; c->name != NULL; c++)
209		if (c->number == id)
210			return c;
211	return NULL;
212}
213
214#define	CIPHER_SEP	","
215int
216ciphers_valid(const char *names)
217{
218	const Cipher *c;
219	char *cipher_list, *cp;
220	char *p;
221
222	if (names == NULL || strcmp(names, "") == 0)
223		return 0;
224	cipher_list = cp = xstrdup(names);
225	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
226	    (p = strsep(&cp, CIPHER_SEP))) {
227		c = cipher_by_name(p);
228#ifdef NONE_CIPHER_ENABLED
229		if (c == NULL || (c->number != SSH_CIPHER_SSH2 &&
230		    c->number != SSH_CIPHER_NONE)) {
231#else
232		if (c == NULL || (c->number != SSH_CIPHER_SSH2)) {
233#endif
234			debug("bad cipher %s [%s]", p, names);
235			free(cipher_list);
236			return 0;
237		}
238	}
239	debug3("ciphers ok: [%s]", names);
240	free(cipher_list);
241	return 1;
242}
243
244/*
245 * Parses the name of the cipher.  Returns the number of the corresponding
246 * cipher, or -1 on error.
247 */
248
249int
250cipher_number(const char *name)
251{
252	const Cipher *c;
253	if (name == NULL)
254		return -1;
255	for (c = ciphers; c->name != NULL; c++)
256		if (strcasecmp(c->name, name) == 0)
257			return c->number;
258	return -1;
259}
260
261char *
262cipher_name(int id)
263{
264	const Cipher *c = cipher_by_number(id);
265	return (c==NULL) ? "<unknown>" : c->name;
266}
267
268void
269cipher_init(CipherContext *cc, const Cipher *cipher,
270    const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
271    int do_encrypt)
272{
273	static int dowarn = 1;
274#ifdef SSH_OLD_EVP
275	EVP_CIPHER *type;
276#else
277	const EVP_CIPHER *type;
278	int klen;
279#endif
280	u_char *junk, *discard;
281
282	if (cipher->number == SSH_CIPHER_DES) {
283		if (dowarn) {
284			error("Warning: use of DES is strongly discouraged "
285			    "due to cryptographic weaknesses");
286			dowarn = 0;
287		}
288		if (keylen > 8)
289			keylen = 8;
290	}
291	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
292	cc->encrypt = do_encrypt;
293
294	if (keylen < cipher->key_len)
295		fatal("cipher_init: key length %d is insufficient for %s.",
296		    keylen, cipher->name);
297	if (iv != NULL && ivlen < cipher_ivlen(cipher))
298		fatal("cipher_init: iv length %d is insufficient for %s.",
299		    ivlen, cipher->name);
300	cc->cipher = cipher;
301
302	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
303		chachapoly_init(&cc->cp_ctx, key, keylen);
304		return;
305	}
306	type = (*cipher->evptype)();
307	EVP_CIPHER_CTX_init(&cc->evp);
308#ifdef SSH_OLD_EVP
309	if (type->key_len > 0 && type->key_len != keylen) {
310		debug("cipher_init: set keylen (%d -> %d)",
311		    type->key_len, keylen);
312		type->key_len = keylen;
313	}
314	EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
315	    (do_encrypt == CIPHER_ENCRYPT));
316#else
317	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
318	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
319		fatal("cipher_init: EVP_CipherInit failed for %s",
320		    cipher->name);
321	if (cipher_authlen(cipher) &&
322	    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
323	    -1, (u_char *)iv))
324		fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s",
325		    cipher->name);
326	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
327	if (klen > 0 && keylen != (u_int)klen) {
328		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
329		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
330			fatal("cipher_init: set keylen failed (%d -> %d)",
331			    klen, keylen);
332	}
333	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
334		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
335		    cipher->name);
336#endif
337
338	if (cipher->discard_len > 0) {
339		junk = xmalloc(cipher->discard_len);
340		discard = xmalloc(cipher->discard_len);
341		if (EVP_Cipher(&cc->evp, discard, junk,
342		    cipher->discard_len) == 0)
343			fatal("evp_crypt: EVP_Cipher failed during discard");
344		explicit_bzero(discard, cipher->discard_len);
345		free(junk);
346		free(discard);
347	}
348}
349
350/*
351 * cipher_crypt() operates as following:
352 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
353 * Theses bytes are treated as additional authenticated data for
354 * authenticated encryption modes.
355 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
356 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
357 * This tag is written on encryption and verified on decryption.
358 * Both 'aadlen' and 'authlen' can be set to 0.
359 * cipher_crypt() returns 0 on success and -1 if the decryption integrity
360 * check fails.
361 */
362int
363cipher_crypt(CipherContext *cc, u_int seqnr, u_char *dest, const u_char *src,
364    u_int len, u_int aadlen, u_int authlen)
365{
366	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
367		return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src, len,
368		    aadlen, authlen, cc->encrypt);
369	if (authlen) {
370		u_char lastiv[1];
371
372		if (authlen != cipher_authlen(cc->cipher))
373			fatal("%s: authlen mismatch %d", __func__, authlen);
374		/* increment IV */
375		if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN,
376		    1, lastiv))
377			fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__);
378		/* set tag on decyption */
379		if (!cc->encrypt &&
380		    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG,
381		    authlen, (u_char *)src + aadlen + len))
382			fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__);
383	}
384	if (aadlen) {
385		if (authlen &&
386		    EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0)
387			fatal("%s: EVP_Cipher(aad) failed", __func__);
388		memcpy(dest, src, aadlen);
389	}
390	if (len % cc->cipher->block_size)
391		fatal("%s: bad plaintext length %d", __func__, len);
392	if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen,
393	    len) < 0)
394		fatal("%s: EVP_Cipher failed", __func__);
395	if (authlen) {
396		/* compute tag (on encrypt) or verify tag (on decrypt) */
397		if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) {
398			if (cc->encrypt)
399				fatal("%s: EVP_Cipher(final) failed", __func__);
400			else
401				return -1;
402		}
403		if (cc->encrypt &&
404		    !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG,
405		    authlen, dest + aadlen + len))
406			fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__);
407	}
408	return 0;
409}
410
411/* Extract the packet length, including any decryption necessary beforehand */
412int
413cipher_get_length(CipherContext *cc, u_int *plenp, u_int seqnr,
414    const u_char *cp, u_int len)
415{
416	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
417		return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr,
418		    cp, len);
419	if (len < 4)
420		return -1;
421	*plenp = get_u32(cp);
422	return 0;
423}
424
425void
426cipher_cleanup(CipherContext *cc)
427{
428	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
429		explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx));
430	else if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
431		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
432}
433
434/*
435 * Selects the cipher, and keys if by computing the MD5 checksum of the
436 * passphrase and using the resulting 16 bytes as the key.
437 */
438
439void
440cipher_set_key_string(CipherContext *cc, const Cipher *cipher,
441    const char *passphrase, int do_encrypt)
442{
443	u_char digest[16];
444
445	if (ssh_digest_memory(SSH_DIGEST_MD5, passphrase, strlen(passphrase),
446	    digest, sizeof(digest)) < 0)
447		fatal("%s: md5 failed", __func__);
448
449	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
450
451	explicit_bzero(digest, sizeof(digest));
452}
453
454/*
455 * Exports an IV from the CipherContext required to export the key
456 * state back from the unprivileged child to the privileged parent
457 * process.
458 */
459
460int
461cipher_get_keyiv_len(const CipherContext *cc)
462{
463	const Cipher *c = cc->cipher;
464	int ivlen;
465
466	if (c->number == SSH_CIPHER_3DES)
467		ivlen = 24;
468	else if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
469		ivlen = 0;
470	else
471		ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
472	return (ivlen);
473}
474
475void
476cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
477{
478	const Cipher *c = cc->cipher;
479	int evplen;
480
481	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
482		if (len != 0)
483			fatal("%s: wrong iv length %d != %d", __func__, len, 0);
484		return;
485	}
486
487	switch (c->number) {
488#ifdef	NONE_CIPHER_ENABLED
489	case SSH_CIPHER_NONE:
490#endif
491	case SSH_CIPHER_SSH2:
492	case SSH_CIPHER_DES:
493	case SSH_CIPHER_BLOWFISH:
494		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
495		if (evplen <= 0)
496			return;
497		if ((u_int)evplen != len)
498			fatal("%s: wrong iv length %d != %d", __func__,
499			    evplen, len);
500#ifdef USE_BUILTIN_RIJNDAEL
501		if (c->evptype == evp_rijndael)
502			ssh_rijndael_iv(&cc->evp, 0, iv, len);
503		else
504#endif
505#ifndef OPENSSL_HAVE_EVPCTR
506		if (c->evptype == evp_aes_128_ctr)
507			ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
508		else
509#endif
510		memcpy(iv, cc->evp.iv, len);
511		break;
512	case SSH_CIPHER_3DES:
513		ssh1_3des_iv(&cc->evp, 0, iv, 24);
514		break;
515	default:
516		fatal("%s: bad cipher %d", __func__, c->number);
517	}
518}
519
520void
521cipher_set_keyiv(CipherContext *cc, u_char *iv)
522{
523	const Cipher *c = cc->cipher;
524	int evplen = 0;
525
526	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
527		return;
528
529	switch (c->number) {
530#ifdef	NONE_CIPHER_ENABLED
531	case SSH_CIPHER_NONE:
532#endif
533	case SSH_CIPHER_SSH2:
534	case SSH_CIPHER_DES:
535	case SSH_CIPHER_BLOWFISH:
536		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
537		if (evplen == 0)
538			return;
539#ifdef USE_BUILTIN_RIJNDAEL
540		if (c->evptype == evp_rijndael)
541			ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
542		else
543#endif
544#ifndef OPENSSL_HAVE_EVPCTR
545		if (c->evptype == evp_aes_128_ctr)
546			ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
547		else
548#endif
549		memcpy(cc->evp.iv, iv, evplen);
550		break;
551	case SSH_CIPHER_3DES:
552		ssh1_3des_iv(&cc->evp, 1, iv, 24);
553		break;
554	default:
555		fatal("%s: bad cipher %d", __func__, c->number);
556	}
557}
558
559int
560cipher_get_keycontext(const CipherContext *cc, u_char *dat)
561{
562	const Cipher *c = cc->cipher;
563	int plen = 0;
564
565	if (c->evptype == EVP_rc4) {
566		plen = EVP_X_STATE_LEN(cc->evp);
567		if (dat == NULL)
568			return (plen);
569		memcpy(dat, EVP_X_STATE(cc->evp), plen);
570	}
571	return (plen);
572}
573
574void
575cipher_set_keycontext(CipherContext *cc, u_char *dat)
576{
577	const Cipher *c = cc->cipher;
578	int plen;
579
580	if (c->evptype == EVP_rc4) {
581		plen = EVP_X_STATE_LEN(cc->evp);
582		memcpy(EVP_X_STATE(cc->evp), dat, plen);
583	}
584}
585