xref: /freebsd/crypto/openssh/cipher.c (revision 9ccc37e32070303fb293a2a1697ffa71eeb49b25) 
1 /* $OpenBSD: cipher.c,v 1.82 2009/01/26 09:58:15 markus 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 
55 extern const EVP_CIPHER *evp_ssh1_bf(void);
56 extern const EVP_CIPHER *evp_ssh1_3des(void);
57 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
58 extern const EVP_CIPHER *evp_aes_128_ctr(void);
59 extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
60 
61 struct Cipher {
62 	char	*name;
63 	int	number;		/* for ssh1 only */
64 	u_int	block_size;
65 	u_int	key_len;
66 	u_int	discard_len;
67 	u_int	cbc_mode;
68 	const EVP_CIPHER	*(*evptype)(void);
69 } ciphers[] = {
70 	{ "none",		SSH_CIPHER_NONE, 8, 0, 0, 0, EVP_enc_null },
71 	{ "des",		SSH_CIPHER_DES, 8, 8, 0, 1, EVP_des_cbc },
72 	{ "3des",		SSH_CIPHER_3DES, 8, 16, 0, 1, evp_ssh1_3des },
73 	{ "blowfish",		SSH_CIPHER_BLOWFISH, 8, 32, 0, 1, evp_ssh1_bf },
74 
75 	{ "3des-cbc",		SSH_CIPHER_SSH2, 8, 24, 0, 1, EVP_des_ede3_cbc },
76 	{ "blowfish-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_bf_cbc },
77 	{ "cast128-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_cast5_cbc },
78 	{ "arcfour",		SSH_CIPHER_SSH2, 8, 16, 0, 0, EVP_rc4 },
79 	{ "arcfour128",		SSH_CIPHER_SSH2, 8, 16, 1536, 0, EVP_rc4 },
80 	{ "arcfour256",		SSH_CIPHER_SSH2, 8, 32, 1536, 0, EVP_rc4 },
81 	{ "aes128-cbc",		SSH_CIPHER_SSH2, 16, 16, 0, 1, EVP_aes_128_cbc },
82 	{ "aes192-cbc",		SSH_CIPHER_SSH2, 16, 24, 0, 1, EVP_aes_192_cbc },
83 	{ "aes256-cbc",		SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
84 	{ "rijndael-cbc@lysator.liu.se",
85 				SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
86 	{ "aes128-ctr",		SSH_CIPHER_SSH2, 16, 16, 0, 0, evp_aes_128_ctr },
87 	{ "aes192-ctr",		SSH_CIPHER_SSH2, 16, 24, 0, 0, evp_aes_128_ctr },
88 	{ "aes256-ctr",		SSH_CIPHER_SSH2, 16, 32, 0, 0, evp_aes_128_ctr },
89 #ifdef USE_CIPHER_ACSS
90 	{ "acss@openssh.org",	SSH_CIPHER_SSH2, 16, 5, 0, 0, EVP_acss },
91 #endif
92 	{ NULL,			SSH_CIPHER_INVALID, 0, 0, 0, 0, NULL }
93 };
94 
95 /*--*/
96 
97 u_int
98 cipher_blocksize(const Cipher *c)
99 {
100 	return (c->block_size);
101 }
102 
103 u_int
104 cipher_keylen(const Cipher *c)
105 {
106 	return (c->key_len);
107 }
108 
109 u_int
110 cipher_get_number(const Cipher *c)
111 {
112 	return (c->number);
113 }
114 
115 u_int
116 cipher_is_cbc(const Cipher *c)
117 {
118 	return (c->cbc_mode);
119 }
120 
121 u_int
122 cipher_mask_ssh1(int client)
123 {
124 	u_int mask = 0;
125 	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
126 	mask |= 1 << SSH_CIPHER_BLOWFISH;
127 	if (client) {
128 		mask |= 1 << SSH_CIPHER_DES;
129 	}
130 	return mask;
131 }
132 
133 Cipher *
134 cipher_by_name(const char *name)
135 {
136 	Cipher *c;
137 	for (c = ciphers; c->name != NULL; c++)
138 		if (strcmp(c->name, name) == 0)
139 			return c;
140 	return NULL;
141 }
142 
143 Cipher *
144 cipher_by_number(int id)
145 {
146 	Cipher *c;
147 	for (c = ciphers; c->name != NULL; c++)
148 		if (c->number == id)
149 			return c;
150 	return NULL;
151 }
152 
153 #define	CIPHER_SEP	","
154 int
155 ciphers_valid(const char *names)
156 {
157 	Cipher *c;
158 	char *cipher_list, *cp;
159 	char *p;
160 
161 	if (names == NULL || strcmp(names, "") == 0)
162 		return 0;
163 	cipher_list = cp = xstrdup(names);
164 	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
165 	    (p = strsep(&cp, CIPHER_SEP))) {
166 		c = cipher_by_name(p);
167 #ifdef NONE_CIPHER_ENABLED
168 		if (c == NULL || (c->number != SSH_CIPHER_SSH2 &&
169 		    c->number != SSH_CIPHER_NONE)) {
170 #else
171 		if (c == NULL || (c->number != SSH_CIPHER_SSH2)) {
172 #endif
173 			debug("bad cipher %s [%s]", p, names);
174 			xfree(cipher_list);
175 			return 0;
176 		} else {
177 			debug3("cipher ok: %s [%s]", p, names);
178 		}
179 	}
180 	debug3("ciphers ok: [%s]", names);
181 	xfree(cipher_list);
182 	return 1;
183 }
184 
185 /*
186  * Parses the name of the cipher.  Returns the number of the corresponding
187  * cipher, or -1 on error.
188  */
189 
190 int
191 cipher_number(const char *name)
192 {
193 	Cipher *c;
194 	if (name == NULL)
195 		return -1;
196 	for (c = ciphers; c->name != NULL; c++)
197 		if (strcasecmp(c->name, name) == 0)
198 			return c->number;
199 	return -1;
200 }
201 
202 char *
203 cipher_name(int id)
204 {
205 	Cipher *c = cipher_by_number(id);
206 	return (c==NULL) ? "<unknown>" : c->name;
207 }
208 
209 void
210 cipher_init(CipherContext *cc, Cipher *cipher,
211     const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
212     int do_encrypt)
213 {
214 	static int dowarn = 1;
215 #ifdef SSH_OLD_EVP
216 	EVP_CIPHER *type;
217 #else
218 	const EVP_CIPHER *type;
219 	int klen;
220 #endif
221 	u_char *junk, *discard;
222 
223 	if (cipher->number == SSH_CIPHER_DES) {
224 		if (dowarn) {
225 			error("Warning: use of DES is strongly discouraged "
226 			    "due to cryptographic weaknesses");
227 			dowarn = 0;
228 		}
229 		if (keylen > 8)
230 			keylen = 8;
231 	}
232 	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
233 
234 	if (keylen < cipher->key_len)
235 		fatal("cipher_init: key length %d is insufficient for %s.",
236 		    keylen, cipher->name);
237 	if (iv != NULL && ivlen < cipher->block_size)
238 		fatal("cipher_init: iv length %d is insufficient for %s.",
239 		    ivlen, cipher->name);
240 	cc->cipher = cipher;
241 
242 	type = (*cipher->evptype)();
243 
244 	EVP_CIPHER_CTX_init(&cc->evp);
245 #ifdef SSH_OLD_EVP
246 	if (type->key_len > 0 && type->key_len != keylen) {
247 		debug("cipher_init: set keylen (%d -> %d)",
248 		    type->key_len, keylen);
249 		type->key_len = keylen;
250 	}
251 	EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
252 	    (do_encrypt == CIPHER_ENCRYPT));
253 #else
254 	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
255 	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
256 		fatal("cipher_init: EVP_CipherInit failed for %s",
257 		    cipher->name);
258 	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
259 	if (klen > 0 && keylen != (u_int)klen) {
260 		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
261 		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
262 			fatal("cipher_init: set keylen failed (%d -> %d)",
263 			    klen, keylen);
264 	}
265 	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
266 		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
267 		    cipher->name);
268 #endif
269 
270 	if (cipher->discard_len > 0) {
271 		junk = xmalloc(cipher->discard_len);
272 		discard = xmalloc(cipher->discard_len);
273 		if (EVP_Cipher(&cc->evp, discard, junk,
274 		    cipher->discard_len) == 0)
275 			fatal("evp_crypt: EVP_Cipher failed during discard");
276 		memset(discard, 0, cipher->discard_len);
277 		xfree(junk);
278 		xfree(discard);
279 	}
280 }
281 
282 void
283 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
284 {
285 	if (len % cc->cipher->block_size)
286 		fatal("cipher_encrypt: bad plaintext length %d", len);
287 	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
288 		fatal("evp_crypt: EVP_Cipher failed");
289 }
290 
291 void
292 cipher_cleanup(CipherContext *cc)
293 {
294 	if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
295 		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
296 }
297 
298 /*
299  * Selects the cipher, and keys if by computing the MD5 checksum of the
300  * passphrase and using the resulting 16 bytes as the key.
301  */
302 
303 void
304 cipher_set_key_string(CipherContext *cc, Cipher *cipher,
305     const char *passphrase, int do_encrypt)
306 {
307 	MD5_CTX md;
308 	u_char digest[16];
309 
310 	MD5_Init(&md);
311 	MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
312 	MD5_Final(digest, &md);
313 
314 	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
315 
316 	memset(digest, 0, sizeof(digest));
317 	memset(&md, 0, sizeof(md));
318 }
319 
320 /*
321  * Exports an IV from the CipherContext required to export the key
322  * state back from the unprivileged child to the privileged parent
323  * process.
324  */
325 
326 int
327 cipher_get_keyiv_len(const CipherContext *cc)
328 {
329 	Cipher *c = cc->cipher;
330 	int ivlen;
331 
332 	if (c->number == SSH_CIPHER_3DES)
333 		ivlen = 24;
334 	else
335 		ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
336 	return (ivlen);
337 }
338 
339 void
340 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
341 {
342 	Cipher *c = cc->cipher;
343 	int evplen;
344 
345 	switch (c->number) {
346 #ifdef	NONE_CIPHER_ENABLED
347 	case SSH_CIPHER_NONE:
348 #endif
349 	case SSH_CIPHER_SSH2:
350 	case SSH_CIPHER_DES:
351 	case SSH_CIPHER_BLOWFISH:
352 		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
353 		if (evplen <= 0)
354 			return;
355 		if ((u_int)evplen != len)
356 			fatal("%s: wrong iv length %d != %d", __func__,
357 			    evplen, len);
358 #ifdef USE_BUILTIN_RIJNDAEL
359 		if (c->evptype == evp_rijndael)
360 			ssh_rijndael_iv(&cc->evp, 0, iv, len);
361 		else
362 #endif
363 		if (c->evptype == evp_aes_128_ctr)
364 			ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
365 		else
366 			memcpy(iv, cc->evp.iv, len);
367 		break;
368 	case SSH_CIPHER_3DES:
369 		ssh1_3des_iv(&cc->evp, 0, iv, 24);
370 		break;
371 	default:
372 		fatal("%s: bad cipher %d", __func__, c->number);
373 	}
374 }
375 
376 void
377 cipher_set_keyiv(CipherContext *cc, u_char *iv)
378 {
379 	Cipher *c = cc->cipher;
380 	int evplen = 0;
381 
382 	switch (c->number) {
383 #ifdef	NONE_CIPHER_ENABLED
384 	case SSH_CIPHER_NONE:
385 #endif
386 	case SSH_CIPHER_SSH2:
387 	case SSH_CIPHER_DES:
388 	case SSH_CIPHER_BLOWFISH:
389 		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
390 		if (evplen == 0)
391 			return;
392 #ifdef USE_BUILTIN_RIJNDAEL
393 		if (c->evptype == evp_rijndael)
394 			ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
395 		else
396 #endif
397 		if (c->evptype == evp_aes_128_ctr)
398 			ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
399 		else
400 			memcpy(cc->evp.iv, iv, evplen);
401 		break;
402 	case SSH_CIPHER_3DES:
403 		ssh1_3des_iv(&cc->evp, 1, iv, 24);
404 		break;
405 	default:
406 		fatal("%s: bad cipher %d", __func__, c->number);
407 	}
408 }
409 
410 #if OPENSSL_VERSION_NUMBER < 0x00907000L
411 #define EVP_X_STATE(evp)	&(evp).c
412 #define EVP_X_STATE_LEN(evp)	sizeof((evp).c)
413 #else
414 #define EVP_X_STATE(evp)	(evp).cipher_data
415 #define EVP_X_STATE_LEN(evp)	(evp).cipher->ctx_size
416 #endif
417 
418 int
419 cipher_get_keycontext(const CipherContext *cc, u_char *dat)
420 {
421 	Cipher *c = cc->cipher;
422 	int plen = 0;
423 
424 	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
425 		plen = EVP_X_STATE_LEN(cc->evp);
426 		if (dat == NULL)
427 			return (plen);
428 		memcpy(dat, EVP_X_STATE(cc->evp), plen);
429 	}
430 	return (plen);
431 }
432 
433 void
434 cipher_set_keycontext(CipherContext *cc, u_char *dat)
435 {
436 	Cipher *c = cc->cipher;
437 	int plen;
438 
439 	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
440 		plen = EVP_X_STATE_LEN(cc->evp);
441 		memcpy(EVP_X_STATE(cc->evp), dat, plen);
442 	}
443 }
444