xref: /freebsd/crypto/openssh/cipher.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
1 /* $OpenBSD: cipher.c,v 1.81 2006/08/03 03:34:42 deraadt 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 	const EVP_CIPHER	*(*evptype)(void);
67 } ciphers[] = {
68 	{ "none",		SSH_CIPHER_NONE, 8, 0, 0, EVP_enc_null },
69 	{ "des",		SSH_CIPHER_DES, 8, 8, 0, EVP_des_cbc },
70 	{ "3des",		SSH_CIPHER_3DES, 8, 16, 0, evp_ssh1_3des },
71 	{ "blowfish",		SSH_CIPHER_BLOWFISH, 8, 32, 0, evp_ssh1_bf },
72 
73 	{ "3des-cbc",		SSH_CIPHER_SSH2, 8, 24, 0, EVP_des_ede3_cbc },
74 	{ "blowfish-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, EVP_bf_cbc },
75 	{ "cast128-cbc",	SSH_CIPHER_SSH2, 8, 16, 0, EVP_cast5_cbc },
76 	{ "arcfour",		SSH_CIPHER_SSH2, 8, 16, 0, EVP_rc4 },
77 	{ "arcfour128",		SSH_CIPHER_SSH2, 8, 16, 1536, EVP_rc4 },
78 	{ "arcfour256",		SSH_CIPHER_SSH2, 8, 32, 1536, EVP_rc4 },
79 	{ "aes128-cbc",		SSH_CIPHER_SSH2, 16, 16, 0, EVP_aes_128_cbc },
80 	{ "aes192-cbc",		SSH_CIPHER_SSH2, 16, 24, 0, EVP_aes_192_cbc },
81 	{ "aes256-cbc",		SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc },
82 	{ "rijndael-cbc@lysator.liu.se",
83 				SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc },
84 	{ "aes128-ctr",		SSH_CIPHER_SSH2, 16, 16, 0, evp_aes_128_ctr },
85 	{ "aes192-ctr",		SSH_CIPHER_SSH2, 16, 24, 0, evp_aes_128_ctr },
86 	{ "aes256-ctr",		SSH_CIPHER_SSH2, 16, 32, 0, evp_aes_128_ctr },
87 #ifdef USE_CIPHER_ACSS
88 	{ "acss@openssh.org",	SSH_CIPHER_SSH2, 16, 5, 0, EVP_acss },
89 #endif
90 	{ NULL,			SSH_CIPHER_INVALID, 0, 0, 0, NULL }
91 };
92 
93 /*--*/
94 
95 u_int
96 cipher_blocksize(const Cipher *c)
97 {
98 	return (c->block_size);
99 }
100 
101 u_int
102 cipher_keylen(const Cipher *c)
103 {
104 	return (c->key_len);
105 }
106 
107 u_int
108 cipher_get_number(const Cipher *c)
109 {
110 	return (c->number);
111 }
112 
113 u_int
114 cipher_mask_ssh1(int client)
115 {
116 	u_int mask = 0;
117 	mask |= 1 << SSH_CIPHER_3DES;		/* Mandatory */
118 	mask |= 1 << SSH_CIPHER_BLOWFISH;
119 	if (client) {
120 		mask |= 1 << SSH_CIPHER_DES;
121 	}
122 	return mask;
123 }
124 
125 Cipher *
126 cipher_by_name(const char *name)
127 {
128 	Cipher *c;
129 	for (c = ciphers; c->name != NULL; c++)
130 		if (strcmp(c->name, name) == 0)
131 			return c;
132 	return NULL;
133 }
134 
135 Cipher *
136 cipher_by_number(int id)
137 {
138 	Cipher *c;
139 	for (c = ciphers; c->name != NULL; c++)
140 		if (c->number == id)
141 			return c;
142 	return NULL;
143 }
144 
145 #define	CIPHER_SEP	","
146 int
147 ciphers_valid(const char *names)
148 {
149 	Cipher *c;
150 	char *cipher_list, *cp;
151 	char *p;
152 
153 	if (names == NULL || strcmp(names, "") == 0)
154 		return 0;
155 	cipher_list = cp = xstrdup(names);
156 	for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
157 	    (p = strsep(&cp, CIPHER_SEP))) {
158 		c = cipher_by_name(p);
159 		if (c == NULL || c->number != SSH_CIPHER_SSH2) {
160 			debug("bad cipher %s [%s]", p, names);
161 			xfree(cipher_list);
162 			return 0;
163 		} else {
164 			debug3("cipher ok: %s [%s]", p, names);
165 		}
166 	}
167 	debug3("ciphers ok: [%s]", names);
168 	xfree(cipher_list);
169 	return 1;
170 }
171 
172 /*
173  * Parses the name of the cipher.  Returns the number of the corresponding
174  * cipher, or -1 on error.
175  */
176 
177 int
178 cipher_number(const char *name)
179 {
180 	Cipher *c;
181 	if (name == NULL)
182 		return -1;
183 	for (c = ciphers; c->name != NULL; c++)
184 		if (strcasecmp(c->name, name) == 0)
185 			return c->number;
186 	return -1;
187 }
188 
189 char *
190 cipher_name(int id)
191 {
192 	Cipher *c = cipher_by_number(id);
193 	return (c==NULL) ? "<unknown>" : c->name;
194 }
195 
196 void
197 cipher_init(CipherContext *cc, Cipher *cipher,
198     const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
199     int do_encrypt)
200 {
201 	static int dowarn = 1;
202 #ifdef SSH_OLD_EVP
203 	EVP_CIPHER *type;
204 #else
205 	const EVP_CIPHER *type;
206 	int klen;
207 #endif
208 	u_char *junk, *discard;
209 
210 	if (cipher->number == SSH_CIPHER_DES) {
211 		if (dowarn) {
212 			error("Warning: use of DES is strongly discouraged "
213 			    "due to cryptographic weaknesses");
214 			dowarn = 0;
215 		}
216 		if (keylen > 8)
217 			keylen = 8;
218 	}
219 	cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
220 
221 	if (keylen < cipher->key_len)
222 		fatal("cipher_init: key length %d is insufficient for %s.",
223 		    keylen, cipher->name);
224 	if (iv != NULL && ivlen < cipher->block_size)
225 		fatal("cipher_init: iv length %d is insufficient for %s.",
226 		    ivlen, cipher->name);
227 	cc->cipher = cipher;
228 
229 	type = (*cipher->evptype)();
230 
231 	EVP_CIPHER_CTX_init(&cc->evp);
232 #ifdef SSH_OLD_EVP
233 	if (type->key_len > 0 && type->key_len != keylen) {
234 		debug("cipher_init: set keylen (%d -> %d)",
235 		    type->key_len, keylen);
236 		type->key_len = keylen;
237 	}
238 	EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
239 	    (do_encrypt == CIPHER_ENCRYPT));
240 #else
241 	if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
242 	    (do_encrypt == CIPHER_ENCRYPT)) == 0)
243 		fatal("cipher_init: EVP_CipherInit failed for %s",
244 		    cipher->name);
245 	klen = EVP_CIPHER_CTX_key_length(&cc->evp);
246 	if (klen > 0 && keylen != (u_int)klen) {
247 		debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
248 		if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
249 			fatal("cipher_init: set keylen failed (%d -> %d)",
250 			    klen, keylen);
251 	}
252 	if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
253 		fatal("cipher_init: EVP_CipherInit: set key failed for %s",
254 		    cipher->name);
255 #endif
256 
257 	if (cipher->discard_len > 0) {
258 		junk = xmalloc(cipher->discard_len);
259 		discard = xmalloc(cipher->discard_len);
260 		if (EVP_Cipher(&cc->evp, discard, junk,
261 		    cipher->discard_len) == 0)
262 			fatal("evp_crypt: EVP_Cipher failed during discard");
263 		memset(discard, 0, cipher->discard_len);
264 		xfree(junk);
265 		xfree(discard);
266 	}
267 }
268 
269 void
270 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
271 {
272 	if (len % cc->cipher->block_size)
273 		fatal("cipher_encrypt: bad plaintext length %d", len);
274 	if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
275 		fatal("evp_crypt: EVP_Cipher failed");
276 }
277 
278 void
279 cipher_cleanup(CipherContext *cc)
280 {
281 	if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
282 		error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
283 }
284 
285 /*
286  * Selects the cipher, and keys if by computing the MD5 checksum of the
287  * passphrase and using the resulting 16 bytes as the key.
288  */
289 
290 void
291 cipher_set_key_string(CipherContext *cc, Cipher *cipher,
292     const char *passphrase, int do_encrypt)
293 {
294 	MD5_CTX md;
295 	u_char digest[16];
296 
297 	MD5_Init(&md);
298 	MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
299 	MD5_Final(digest, &md);
300 
301 	cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
302 
303 	memset(digest, 0, sizeof(digest));
304 	memset(&md, 0, sizeof(md));
305 }
306 
307 /*
308  * Exports an IV from the CipherContext required to export the key
309  * state back from the unprivileged child to the privileged parent
310  * process.
311  */
312 
313 int
314 cipher_get_keyiv_len(const CipherContext *cc)
315 {
316 	Cipher *c = cc->cipher;
317 	int ivlen;
318 
319 	if (c->number == SSH_CIPHER_3DES)
320 		ivlen = 24;
321 	else
322 		ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
323 	return (ivlen);
324 }
325 
326 void
327 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
328 {
329 	Cipher *c = cc->cipher;
330 	int evplen;
331 
332 	switch (c->number) {
333 	case SSH_CIPHER_SSH2:
334 	case SSH_CIPHER_DES:
335 	case SSH_CIPHER_BLOWFISH:
336 		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
337 		if (evplen <= 0)
338 			return;
339 		if ((u_int)evplen != len)
340 			fatal("%s: wrong iv length %d != %d", __func__,
341 			    evplen, len);
342 #ifdef USE_BUILTIN_RIJNDAEL
343 		if (c->evptype == evp_rijndael)
344 			ssh_rijndael_iv(&cc->evp, 0, iv, len);
345 		else
346 #endif
347 		if (c->evptype == evp_aes_128_ctr)
348 			ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
349 		else
350 			memcpy(iv, cc->evp.iv, len);
351 		break;
352 	case SSH_CIPHER_3DES:
353 		ssh1_3des_iv(&cc->evp, 0, iv, 24);
354 		break;
355 	default:
356 		fatal("%s: bad cipher %d", __func__, c->number);
357 	}
358 }
359 
360 void
361 cipher_set_keyiv(CipherContext *cc, u_char *iv)
362 {
363 	Cipher *c = cc->cipher;
364 	int evplen = 0;
365 
366 	switch (c->number) {
367 	case SSH_CIPHER_SSH2:
368 	case SSH_CIPHER_DES:
369 	case SSH_CIPHER_BLOWFISH:
370 		evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
371 		if (evplen == 0)
372 			return;
373 #ifdef USE_BUILTIN_RIJNDAEL
374 		if (c->evptype == evp_rijndael)
375 			ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
376 		else
377 #endif
378 		if (c->evptype == evp_aes_128_ctr)
379 			ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
380 		else
381 			memcpy(cc->evp.iv, iv, evplen);
382 		break;
383 	case SSH_CIPHER_3DES:
384 		ssh1_3des_iv(&cc->evp, 1, iv, 24);
385 		break;
386 	default:
387 		fatal("%s: bad cipher %d", __func__, c->number);
388 	}
389 }
390 
391 #if OPENSSL_VERSION_NUMBER < 0x00907000L
392 #define EVP_X_STATE(evp)	&(evp).c
393 #define EVP_X_STATE_LEN(evp)	sizeof((evp).c)
394 #else
395 #define EVP_X_STATE(evp)	(evp).cipher_data
396 #define EVP_X_STATE_LEN(evp)	(evp).cipher->ctx_size
397 #endif
398 
399 int
400 cipher_get_keycontext(const CipherContext *cc, u_char *dat)
401 {
402 	Cipher *c = cc->cipher;
403 	int plen = 0;
404 
405 	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
406 		plen = EVP_X_STATE_LEN(cc->evp);
407 		if (dat == NULL)
408 			return (plen);
409 		memcpy(dat, EVP_X_STATE(cc->evp), plen);
410 	}
411 	return (plen);
412 }
413 
414 void
415 cipher_set_keycontext(CipherContext *cc, u_char *dat)
416 {
417 	Cipher *c = cc->cipher;
418 	int plen;
419 
420 	if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
421 		plen = EVP_X_STATE_LEN(cc->evp);
422 		memcpy(EVP_X_STATE(cc->evp), dat, plen);
423 	}
424 }
425