1/* $OpenBSD: cipher.c,v 1.111 2018/02/23 15:58:37 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 <string.h>
43#include <stdarg.h>
44#include <stdio.h>
45
46#include "cipher.h"
47#include "misc.h"
48#include "sshbuf.h"
49#include "ssherr.h"
50#include "digest.h"
51
52#include "openbsd-compat/openssl-compat.h"
53
54
55struct sshcipher_ctx {
56	int	plaintext;
57	int	encrypt;
58	EVP_CIPHER_CTX *evp;
59	struct chachapoly_ctx cp_ctx; /* XXX union with evp? */
60	struct aesctr_ctx ac_ctx; /* XXX union with evp? */
61	const struct sshcipher *cipher;
62};
63
64struct sshcipher {
65	char	*name;
66	u_int	block_size;
67	u_int	key_len;
68	u_int	iv_len;		/* defaults to block_size */
69	u_int	auth_len;
70	u_int	flags;
71#define CFLAG_CBC		(1<<0)
72#define CFLAG_CHACHAPOLY	(1<<1)
73#define CFLAG_AESCTR		(1<<2)
74#define CFLAG_NONE		(1<<3)
75#define CFLAG_INTERNAL		CFLAG_NONE /* Don't use "none" for packets */
76#ifdef WITH_OPENSSL
77	const EVP_CIPHER	*(*evptype)(void);
78#else
79	void	*ignored;
80#endif
81};
82
83static const struct sshcipher ciphers[] = {
84#ifdef WITH_OPENSSL
85#ifndef OPENSSL_NO_DES
86	{ "3des-cbc",		8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc },
87#endif
88	{ "aes128-cbc",		16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc },
89	{ "aes192-cbc",		16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc },
90	{ "aes256-cbc",		16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
91	{ "rijndael-cbc@lysator.liu.se",
92				16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
93	{ "aes128-ctr",		16, 16, 0, 0, 0, EVP_aes_128_ctr },
94	{ "aes192-ctr",		16, 24, 0, 0, 0, EVP_aes_192_ctr },
95	{ "aes256-ctr",		16, 32, 0, 0, 0, EVP_aes_256_ctr },
96# ifdef OPENSSL_HAVE_EVPGCM
97	{ "aes128-gcm@openssh.com",
98				16, 16, 12, 16, 0, EVP_aes_128_gcm },
99	{ "aes256-gcm@openssh.com",
100				16, 32, 12, 16, 0, EVP_aes_256_gcm },
101# endif /* OPENSSL_HAVE_EVPGCM */
102#else
103	{ "aes128-ctr",		16, 16, 0, 0, CFLAG_AESCTR, NULL },
104	{ "aes192-ctr",		16, 24, 0, 0, CFLAG_AESCTR, NULL },
105	{ "aes256-ctr",		16, 32, 0, 0, CFLAG_AESCTR, NULL },
106#endif
107	{ "chacha20-poly1305@openssh.com",
108				8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL },
109	{ "none",		8, 0, 0, 0, CFLAG_NONE, NULL },
110
111	{ NULL,			0, 0, 0, 0, 0, NULL }
112};
113
114/*--*/
115
116/* Returns a comma-separated list of supported ciphers. */
117char *
118cipher_alg_list(char sep, int auth_only)
119{
120	char *tmp, *ret = NULL;
121	size_t nlen, rlen = 0;
122	const struct sshcipher *c;
123
124	for (c = ciphers; c->name != NULL; c++) {
125		if ((c->flags & CFLAG_INTERNAL) != 0)
126			continue;
127		if (auth_only && c->auth_len == 0)
128			continue;
129		if (ret != NULL)
130			ret[rlen++] = sep;
131		nlen = strlen(c->name);
132		if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
133			free(ret);
134			return NULL;
135		}
136		ret = tmp;
137		memcpy(ret + rlen, c->name, nlen + 1);
138		rlen += nlen;
139	}
140	return ret;
141}
142
143u_int
144cipher_blocksize(const struct sshcipher *c)
145{
146	return (c->block_size);
147}
148
149u_int
150cipher_keylen(const struct sshcipher *c)
151{
152	return (c->key_len);
153}
154
155u_int
156cipher_seclen(const struct sshcipher *c)
157{
158	if (strcmp("3des-cbc", c->name) == 0)
159		return 14;
160	return cipher_keylen(c);
161}
162
163u_int
164cipher_authlen(const struct sshcipher *c)
165{
166	return (c->auth_len);
167}
168
169u_int
170cipher_ivlen(const struct sshcipher *c)
171{
172	/*
173	 * Default is cipher block size, except for chacha20+poly1305 that
174	 * needs no IV. XXX make iv_len == -1 default?
175	 */
176	return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ?
177	    c->iv_len : c->block_size;
178}
179
180u_int
181cipher_is_cbc(const struct sshcipher *c)
182{
183	return (c->flags & CFLAG_CBC) != 0;
184}
185
186u_int
187cipher_ctx_is_plaintext(struct sshcipher_ctx *cc)
188{
189	return cc->plaintext;
190}
191
192const struct sshcipher *
193cipher_by_name(const char *name)
194{
195	const struct sshcipher *c;
196	for (c = ciphers; c->name != NULL; c++)
197		if (strcmp(c->name, name) == 0)
198			return c;
199	return NULL;
200}
201
202#define	CIPHER_SEP	","
203int
204ciphers_valid(const char *names)
205{
206	const struct sshcipher *c;
207	char *cipher_list, *cp;
208	char *p;
209
210	if (names == NULL || strcmp(names, "") == 0)
211		return 0;
212	if ((cipher_list = cp = strdup(names)) == NULL)
213		return 0;
214	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
215	    (p = strsep(&cp, CIPHER_SEP))) {
216		c = cipher_by_name(p);
217		if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) {
218			free(cipher_list);
219			return 0;
220		}
221	}
222	free(cipher_list);
223	return 1;
224}
225
226const char *
227cipher_warning_message(const struct sshcipher_ctx *cc)
228{
229	if (cc == NULL || cc->cipher == NULL)
230		return NULL;
231	/* XXX repurpose for CBC warning */
232	return NULL;
233}
234
235int
236cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher,
237    const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
238    int do_encrypt)
239{
240	struct sshcipher_ctx *cc = NULL;
241	int ret = SSH_ERR_INTERNAL_ERROR;
242#ifdef WITH_OPENSSL
243	const EVP_CIPHER *type;
244	int klen;
245#endif
246
247	*ccp = NULL;
248	if ((cc = calloc(sizeof(*cc), 1)) == NULL)
249		return SSH_ERR_ALLOC_FAIL;
250
251	cc->plaintext = (cipher->flags & CFLAG_NONE) != 0;
252	cc->encrypt = do_encrypt;
253
254	if (keylen < cipher->key_len ||
255	    (iv != NULL && ivlen < cipher_ivlen(cipher))) {
256		ret = SSH_ERR_INVALID_ARGUMENT;
257		goto out;
258	}
259
260	cc->cipher = cipher;
261	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
262		ret = chachapoly_init(&cc->cp_ctx, key, keylen);
263		goto out;
264	}
265	if ((cc->cipher->flags & CFLAG_NONE) != 0) {
266		ret = 0;
267		goto out;
268	}
269#ifndef WITH_OPENSSL
270	if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
271		aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen);
272		aesctr_ivsetup(&cc->ac_ctx, iv);
273		ret = 0;
274		goto out;
275	}
276	ret = SSH_ERR_INVALID_ARGUMENT;
277	goto out;
278#else /* WITH_OPENSSL */
279	type = (*cipher->evptype)();
280	if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) {
281		ret = SSH_ERR_ALLOC_FAIL;
282		goto out;
283	}
284	if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv,
285	    (do_encrypt == CIPHER_ENCRYPT)) == 0) {
286		ret = SSH_ERR_LIBCRYPTO_ERROR;
287		goto out;
288	}
289	if (cipher_authlen(cipher) &&
290	    !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
291	    -1, (u_char *)iv)) {
292		ret = SSH_ERR_LIBCRYPTO_ERROR;
293		goto out;
294	}
295	klen = EVP_CIPHER_CTX_key_length(cc->evp);
296	if (klen > 0 && keylen != (u_int)klen) {
297		if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) {
298			ret = SSH_ERR_LIBCRYPTO_ERROR;
299			goto out;
300		}
301	}
302	if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) {
303		ret = SSH_ERR_LIBCRYPTO_ERROR;
304		goto out;
305	}
306	ret = 0;
307#endif /* WITH_OPENSSL */
308 out:
309	if (ret == 0) {
310		/* success */
311		*ccp = cc;
312	} else {
313		if (cc != NULL) {
314#ifdef WITH_OPENSSL
315			EVP_CIPHER_CTX_free(cc->evp);
316#endif /* WITH_OPENSSL */
317			explicit_bzero(cc, sizeof(*cc));
318			free(cc);
319		}
320	}
321	return ret;
322}
323
324/*
325 * cipher_crypt() operates as following:
326 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
327 * Theses bytes are treated as additional authenticated data for
328 * authenticated encryption modes.
329 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
330 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
331 * This tag is written on encryption and verified on decryption.
332 * Both 'aadlen' and 'authlen' can be set to 0.
333 */
334int
335cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest,
336   const u_char *src, u_int len, u_int aadlen, u_int authlen)
337{
338	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
339		return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src,
340		    len, aadlen, authlen, cc->encrypt);
341	}
342	if ((cc->cipher->flags & CFLAG_NONE) != 0) {
343		memcpy(dest, src, aadlen + len);
344		return 0;
345	}
346#ifndef WITH_OPENSSL
347	if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
348		if (aadlen)
349			memcpy(dest, src, aadlen);
350		aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen,
351		    dest + aadlen, len);
352		return 0;
353	}
354	return SSH_ERR_INVALID_ARGUMENT;
355#else
356	if (authlen) {
357		u_char lastiv[1];
358
359		if (authlen != cipher_authlen(cc->cipher))
360			return SSH_ERR_INVALID_ARGUMENT;
361		/* increment IV */
362		if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
363		    1, lastiv))
364			return SSH_ERR_LIBCRYPTO_ERROR;
365		/* set tag on decyption */
366		if (!cc->encrypt &&
367		    !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG,
368		    authlen, (u_char *)src + aadlen + len))
369			return SSH_ERR_LIBCRYPTO_ERROR;
370	}
371	if (aadlen) {
372		if (authlen &&
373		    EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0)
374			return SSH_ERR_LIBCRYPTO_ERROR;
375		memcpy(dest, src, aadlen);
376	}
377	if (len % cc->cipher->block_size)
378		return SSH_ERR_INVALID_ARGUMENT;
379	if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen,
380	    len) < 0)
381		return SSH_ERR_LIBCRYPTO_ERROR;
382	if (authlen) {
383		/* compute tag (on encrypt) or verify tag (on decrypt) */
384		if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0)
385			return cc->encrypt ?
386			    SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID;
387		if (cc->encrypt &&
388		    !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG,
389		    authlen, dest + aadlen + len))
390			return SSH_ERR_LIBCRYPTO_ERROR;
391	}
392	return 0;
393#endif
394}
395
396/* Extract the packet length, including any decryption necessary beforehand */
397int
398cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr,
399    const u_char *cp, u_int len)
400{
401	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
402		return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr,
403		    cp, len);
404	if (len < 4)
405		return SSH_ERR_MESSAGE_INCOMPLETE;
406	*plenp = PEEK_U32(cp);
407	return 0;
408}
409
410void
411cipher_free(struct sshcipher_ctx *cc)
412{
413	if (cc == NULL)
414		return;
415	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
416		explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx));
417	else if ((cc->cipher->flags & CFLAG_AESCTR) != 0)
418		explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx));
419#ifdef WITH_OPENSSL
420	EVP_CIPHER_CTX_free(cc->evp);
421	cc->evp = NULL;
422#endif
423	explicit_bzero(cc, sizeof(*cc));
424	free(cc);
425}
426
427/*
428 * Exports an IV from the sshcipher_ctx required to export the key
429 * state back from the unprivileged child to the privileged parent
430 * process.
431 */
432int
433cipher_get_keyiv_len(const struct sshcipher_ctx *cc)
434{
435	const struct sshcipher *c = cc->cipher;
436
437	if ((c->flags & CFLAG_CHACHAPOLY) != 0)
438		return 0;
439	else if ((c->flags & CFLAG_AESCTR) != 0)
440		return sizeof(cc->ac_ctx.ctr);
441#ifdef WITH_OPENSSL
442	return EVP_CIPHER_CTX_iv_length(cc->evp);
443#else
444	return 0;
445#endif
446}
447
448int
449cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len)
450{
451#ifdef WITH_OPENSSL
452	const struct sshcipher *c = cc->cipher;
453	int evplen;
454#endif
455
456	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
457		if (len != 0)
458			return SSH_ERR_INVALID_ARGUMENT;
459		return 0;
460	}
461	if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
462		if (len != sizeof(cc->ac_ctx.ctr))
463			return SSH_ERR_INVALID_ARGUMENT;
464		memcpy(iv, cc->ac_ctx.ctr, len);
465		return 0;
466	}
467	if ((cc->cipher->flags & CFLAG_NONE) != 0)
468		return 0;
469
470#ifdef WITH_OPENSSL
471	evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
472	if (evplen == 0)
473		return 0;
474	else if (evplen < 0)
475		return SSH_ERR_LIBCRYPTO_ERROR;
476	if ((size_t)evplen != len)
477		return SSH_ERR_INVALID_ARGUMENT;
478#ifndef OPENSSL_HAVE_EVPCTR
479	if (c->evptype == evp_aes_128_ctr)
480		ssh_aes_ctr_iv(cc->evp, 0, iv, len);
481	else
482#endif
483	if (cipher_authlen(c)) {
484		if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
485		   len, iv))
486		       return SSH_ERR_LIBCRYPTO_ERROR;
487	} else if (!EVP_CIPHER_CTX_get_iv(cc->evp, iv, len))
488	       return SSH_ERR_LIBCRYPTO_ERROR;
489#endif
490	return 0;
491}
492
493int
494cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len)
495{
496#ifdef WITH_OPENSSL
497	const struct sshcipher *c = cc->cipher;
498	int evplen = 0;
499#endif
500
501	if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
502		return 0;
503	if ((cc->cipher->flags & CFLAG_NONE) != 0)
504		return 0;
505
506#ifdef WITH_OPENSSL
507	evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
508	if (evplen <= 0)
509		return SSH_ERR_LIBCRYPTO_ERROR;
510	if ((size_t)evplen != len)
511		return SSH_ERR_INVALID_ARGUMENT;
512#ifndef OPENSSL_HAVE_EVPCTR
513	/* XXX iv arg is const, but ssh_aes_ctr_iv isn't */
514	if (c->evptype == evp_aes_128_ctr)
515		ssh_aes_ctr_iv(cc->evp, 1, (u_char *)iv, evplen);
516	else
517#endif
518	if (cipher_authlen(c)) {
519		/* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */
520		if (!EVP_CIPHER_CTX_ctrl(cc->evp,
521		    EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv))
522			return SSH_ERR_LIBCRYPTO_ERROR;
523	} else if (!EVP_CIPHER_CTX_set_iv(cc->evp, iv, evplen))
524		return SSH_ERR_LIBCRYPTO_ERROR;
525#endif
526	return 0;
527}
528