1 /* $OpenBSD: cipher.c,v 1.97 2014/02/07 06:55:54 djm 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 <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
57 extern const EVP_CIPHER *evp_ssh1_bf(void);
58 extern const EVP_CIPHER *evp_ssh1_3des(void);
59 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, 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 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
75 static 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. */
111 char *
cipher_alg_list(char sep,int auth_only)112 cipher_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
133 u_int
cipher_blocksize(const Cipher * c)134 cipher_blocksize(const Cipher *c)
135 {
136 return (c->block_size);
137 }
138
139 u_int
cipher_keylen(const Cipher * c)140 cipher_keylen(const Cipher *c)
141 {
142 return (c->key_len);
143 }
144
145 u_int
cipher_seclen(const Cipher * c)146 cipher_seclen(const Cipher *c)
147 {
148 if (strcmp("3des-cbc", c->name) == 0)
149 return 14;
150 return cipher_keylen(c);
151 }
152
153 u_int
cipher_authlen(const Cipher * c)154 cipher_authlen(const Cipher *c)
155 {
156 return (c->auth_len);
157 }
158
159 u_int
cipher_ivlen(const Cipher * c)160 cipher_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
170 u_int
cipher_get_number(const Cipher * c)171 cipher_get_number(const Cipher *c)
172 {
173 return (c->number);
174 }
175
176 u_int
cipher_is_cbc(const Cipher * c)177 cipher_is_cbc(const Cipher *c)
178 {
179 return (c->flags & CFLAG_CBC) != 0;
180 }
181
182 u_int
cipher_mask_ssh1(int client)183 cipher_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
194 const Cipher *
cipher_by_name(const char * name)195 cipher_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
204 const Cipher *
cipher_by_number(int id)205 cipher_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 ","
215 int
ciphers_valid(const char * names)216 ciphers_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
249 int
250 cipher_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
261 char *
262 cipher_name(int id)
263 {
264 const Cipher *c = cipher_by_number(id);
265 return (c==NULL) ? "<unknown>" : c->name;
266 }
267
268 void
269 cipher_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 */
362 int
363 cipher_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 */
412 int
413 cipher_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
425 void
426 cipher_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
439 void
440 cipher_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
460 int
461 cipher_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
475 void
476 cipher_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
520 void
521 cipher_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
559 int
560 cipher_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
574 void
575 cipher_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