xref: /freebsd/crypto/openssh/cipher.c (revision 195ebc7e9e4b129de810833791a19dfb4349d6a9)
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 
54 extern const EVP_CIPHER *evp_ssh1_bf(void);
55 extern const EVP_CIPHER *evp_ssh1_3des(void);
56 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
57 extern const EVP_CIPHER *evp_aes_128_ctr(void);
58 extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
59 
60 struct 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 	{ "cast128-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_cast5_cbc },
77 	{ "arcfour",		SSH_CIPHER_SSH2, 8, 16, 0, 0, EVP_rc4 },
78 	{ "arcfour128",		SSH_CIPHER_SSH2, 8, 16, 1536, 0, EVP_rc4 },
79 	{ "arcfour256",		SSH_CIPHER_SSH2, 8, 32, 1536, 0, EVP_rc4 },
80 	{ "aes128-cbc",		SSH_CIPHER_SSH2, 16, 16, 0, 1, EVP_aes_128_cbc },
81 	{ "aes192-cbc",		SSH_CIPHER_SSH2, 16, 24, 0, 1, EVP_aes_192_cbc },
82 	{ "aes256-cbc",		SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
83 	{ "rijndael-cbc@lysator.liu.se",
84 				SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
85 	{ "aes128-ctr",		SSH_CIPHER_SSH2, 16, 16, 0, 0, evp_aes_128_ctr },
86 	{ "aes192-ctr",		SSH_CIPHER_SSH2, 16, 24, 0, 0, evp_aes_128_ctr },
87 	{ "aes256-ctr",		SSH_CIPHER_SSH2, 16, 32, 0, 0, evp_aes_128_ctr },
88 #ifdef USE_CIPHER_ACSS
89 	{ "acss@openssh.org",	SSH_CIPHER_SSH2, 16, 5, 0, 0, EVP_acss },
90 #endif
91 	{ NULL,			SSH_CIPHER_INVALID, 0, 0, 0, 0, NULL }
92 };
93 
94 /*--*/
95 
96 u_int
97 cipher_blocksize(const Cipher *c)
98 {
99 	return (c->block_size);
100 }
101 
102 u_int
103 cipher_keylen(const Cipher *c)
104 {
105 	return (c->key_len);
106 }
107 
108 u_int
109 cipher_get_number(const Cipher *c)
110 {
111 	return (c->number);
112 }
113 
114 u_int
115 cipher_is_cbc(const Cipher *c)
116 {
117 	return (c->cbc_mode);
118 }
119 
120 u_int
121 cipher_mask_ssh1(int client)
122 {
123 	u_int mask = 0;
124 	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
125 	mask |= 1 << SSH_CIPHER_BLOWFISH;
126 	if (client) {
127 		mask |= 1 << SSH_CIPHER_DES;
128 	}
129 	return mask;
130 }
131 
132 Cipher *
133 cipher_by_name(const char *name)
134 {
135 	Cipher *c;
136 	for (c = ciphers; c->name != NULL; c++)
137 		if (strcmp(c->name, name) == 0)
138 			return c;
139 	return NULL;
140 }
141 
142 Cipher *
143 cipher_by_number(int id)
144 {
145 	Cipher *c;
146 	for (c = ciphers; c->name != NULL; c++)
147 		if (c->number == id)
148 			return c;
149 	return NULL;
150 }
151 
152 #define	CIPHER_SEP	","
153 int
154 ciphers_valid(const char *names)
155 {
156 	Cipher *c;
157 	char *cipher_list, *cp;
158 	char *p;
159 
160 	if (names == NULL || strcmp(names, "") == 0)
161 		return 0;
162 	cipher_list = cp = xstrdup(names);
163 	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
164 	    (p = strsep(&cp, CIPHER_SEP))) {
165 		c = cipher_by_name(p);
166 		if (c == NULL || c->number != SSH_CIPHER_SSH2) {
167 			debug("bad cipher %s [%s]", p, names);
168 			xfree(cipher_list);
169 			return 0;
170 		} else {
171 			debug3("cipher ok: %s [%s]", p, names);
172 		}
173 	}
174 	debug3("ciphers ok: [%s]", names);
175 	xfree(cipher_list);
176 	return 1;
177 }
178 
179 /*
180  * Parses the name of the cipher.  Returns the number of the corresponding
181  * cipher, or -1 on error.
182  */
183 
184 int
185 cipher_number(const char *name)
186 {
187 	Cipher *c;
188 	if (name == NULL)
189 		return -1;
190 	for (c = ciphers; c->name != NULL; c++)
191 		if (strcasecmp(c->name, name) == 0)
192 			return c->number;
193 	return -1;
194 }
195 
196 char *
197 cipher_name(int id)
198 {
199 	Cipher *c = cipher_by_number(id);
200 	return (c==NULL) ? "<unknown>" : c->name;
201 }
202 
203 void
204 cipher_init(CipherContext *cc, Cipher *cipher,
205     const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
206     int do_encrypt)
207 {
208 	static int dowarn = 1;
209 #ifdef SSH_OLD_EVP
210 	EVP_CIPHER *type;
211 #else
212 	const EVP_CIPHER *type;
213 	int klen;
214 #endif
215 	u_char *junk, *discard;
216 
217 	if (cipher->number == SSH_CIPHER_DES) {
218 		if (dowarn) {
219 			error("Warning: use of DES is strongly discouraged "
220 			    "due to cryptographic weaknesses");
221 			dowarn = 0;
222 		}
223 		if (keylen > 8)
224 			keylen = 8;
225 	}
226 	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
227 
228 	if (keylen < cipher->key_len)
229 		fatal("cipher_init: key length %d is insufficient for %s.",
230 		    keylen, cipher->name);
231 	if (iv != NULL && ivlen < cipher->block_size)
232 		fatal("cipher_init: iv length %d is insufficient for %s.",
233 		    ivlen, cipher->name);
234 	cc->cipher = cipher;
235 
236 	type = (*cipher->evptype)();
237 
238 	EVP_CIPHER_CTX_init(&cc->evp);
239 #ifdef SSH_OLD_EVP
240 	if (type->key_len > 0 && type->key_len != keylen) {
241 		debug("cipher_init: set keylen (%d -> %d)",
242 		    type->key_len, keylen);
243 		type->key_len = keylen;
244 	}
245 	EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
246 	    (do_encrypt == CIPHER_ENCRYPT));
247 #else
248 	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
249 	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
250 		fatal("cipher_init: EVP_CipherInit failed for %s",
251 		    cipher->name);
252 	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
253 	if (klen > 0 && keylen != (u_int)klen) {
254 		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
255 		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
256 			fatal("cipher_init: set keylen failed (%d -> %d)",
257 			    klen, keylen);
258 	}
259 	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
260 		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
261 		    cipher->name);
262 #endif
263 
264 	if (cipher->discard_len > 0) {
265 		junk = xmalloc(cipher->discard_len);
266 		discard = xmalloc(cipher->discard_len);
267 		if (EVP_Cipher(&cc->evp, discard, junk,
268 		    cipher->discard_len) == 0)
269 			fatal("evp_crypt: EVP_Cipher failed during discard");
270 		memset(discard, 0, cipher->discard_len);
271 		xfree(junk);
272 		xfree(discard);
273 	}
274 }
275 
276 void
277 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
278 {
279 	if (len % cc->cipher->block_size)
280 		fatal("cipher_encrypt: bad plaintext length %d", len);
281 	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
282 		fatal("evp_crypt: EVP_Cipher failed");
283 }
284 
285 void
286 cipher_cleanup(CipherContext *cc)
287 {
288 	if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
289 		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
290 }
291 
292 /*
293  * Selects the cipher, and keys if by computing the MD5 checksum of the
294  * passphrase and using the resulting 16 bytes as the key.
295  */
296 
297 void
298 cipher_set_key_string(CipherContext *cc, Cipher *cipher,
299     const char *passphrase, int do_encrypt)
300 {
301 	MD5_CTX md;
302 	u_char digest[16];
303 
304 	MD5_Init(&md);
305 	MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
306 	MD5_Final(digest, &md);
307 
308 	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
309 
310 	memset(digest, 0, sizeof(digest));
311 	memset(&md, 0, sizeof(md));
312 }
313 
314 /*
315  * Exports an IV from the CipherContext required to export the key
316  * state back from the unprivileged child to the privileged parent
317  * process.
318  */
319 
320 int
321 cipher_get_keyiv_len(const CipherContext *cc)
322 {
323 	Cipher *c = cc->cipher;
324 	int ivlen;
325 
326 	if (c->number == SSH_CIPHER_3DES)
327 		ivlen = 24;
328 	else
329 		ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
330 	return (ivlen);
331 }
332 
333 void
334 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
335 {
336 	Cipher *c = cc->cipher;
337 	int evplen;
338 
339 	switch (c->number) {
340 	case SSH_CIPHER_SSH2:
341 	case SSH_CIPHER_DES:
342 	case SSH_CIPHER_BLOWFISH:
343 		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
344 		if (evplen <= 0)
345 			return;
346 		if ((u_int)evplen != len)
347 			fatal("%s: wrong iv length %d != %d", __func__,
348 			    evplen, len);
349 #ifdef USE_BUILTIN_RIJNDAEL
350 		if (c->evptype == evp_rijndael)
351 			ssh_rijndael_iv(&cc->evp, 0, iv, len);
352 		else
353 #endif
354 		if (c->evptype == evp_aes_128_ctr)
355 			ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
356 		else
357 			memcpy(iv, cc->evp.iv, len);
358 		break;
359 	case SSH_CIPHER_3DES:
360 		ssh1_3des_iv(&cc->evp, 0, iv, 24);
361 		break;
362 	default:
363 		fatal("%s: bad cipher %d", __func__, c->number);
364 	}
365 }
366 
367 void
368 cipher_set_keyiv(CipherContext *cc, u_char *iv)
369 {
370 	Cipher *c = cc->cipher;
371 	int evplen = 0;
372 
373 	switch (c->number) {
374 	case SSH_CIPHER_SSH2:
375 	case SSH_CIPHER_DES:
376 	case SSH_CIPHER_BLOWFISH:
377 		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
378 		if (evplen == 0)
379 			return;
380 #ifdef USE_BUILTIN_RIJNDAEL
381 		if (c->evptype == evp_rijndael)
382 			ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
383 		else
384 #endif
385 		if (c->evptype == evp_aes_128_ctr)
386 			ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
387 		else
388 			memcpy(cc->evp.iv, iv, evplen);
389 		break;
390 	case SSH_CIPHER_3DES:
391 		ssh1_3des_iv(&cc->evp, 1, iv, 24);
392 		break;
393 	default:
394 		fatal("%s: bad cipher %d", __func__, c->number);
395 	}
396 }
397 
398 #if OPENSSL_VERSION_NUMBER < 0x00907000L
399 #define EVP_X_STATE(evp)	&(evp).c
400 #define EVP_X_STATE_LEN(evp)	sizeof((evp).c)
401 #else
402 #define EVP_X_STATE(evp)	(evp).cipher_data
403 #define EVP_X_STATE_LEN(evp)	(evp).cipher->ctx_size
404 #endif
405 
406 int
407 cipher_get_keycontext(const CipherContext *cc, u_char *dat)
408 {
409 	Cipher *c = cc->cipher;
410 	int plen = 0;
411 
412 	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
413 		plen = EVP_X_STATE_LEN(cc->evp);
414 		if (dat == NULL)
415 			return (plen);
416 		memcpy(dat, EVP_X_STATE(cc->evp), plen);
417 	}
418 	return (plen);
419 }
420 
421 void
422 cipher_set_keycontext(CipherContext *cc, u_char *dat)
423 {
424 	Cipher *c = cc->cipher;
425 	int plen;
426 
427 	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
428 		plen = EVP_X_STATE_LEN(cc->evp);
429 		memcpy(EVP_X_STATE(cc->evp), dat, plen);
430 	}
431 }
432