1 /* $OpenBSD: cipher.c,v 1.97 2014/02/07 06:55:54 djm 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 "xmalloc.h"
47 #include "log.h"
48 #include "misc.h"
49 #include "cipher.h"
50 #include "buffer.h"
51 #include "digest.h"
52
53 /* compatibility with old or broken OpenSSL versions */
54 #include "openbsd-compat/openssl-compat.h"
55
56 extern const EVP_CIPHER *evp_ssh1_bf(void);
57 extern const EVP_CIPHER *evp_ssh1_3des(void);
58 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, 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 iv_len; /* defaults to block_size */
66 u_int auth_len;
67 u_int discard_len;
68 u_int flags;
69 #define CFLAG_CBC (1<<0)
70 #define CFLAG_CHACHAPOLY (1<<1)
71 const EVP_CIPHER *(*evptype)(void);
72 };
73
74 static const struct Cipher ciphers[] = {
75 { "none", SSH_CIPHER_NONE, 8, 0, 0, 0, 0, 0, EVP_enc_null },
76 { "des", SSH_CIPHER_DES, 8, 8, 0, 0, 0, 1, EVP_des_cbc },
77 { "3des", SSH_CIPHER_3DES, 8, 16, 0, 0, 0, 1, evp_ssh1_3des },
78 { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, 0, 0, 1, evp_ssh1_bf },
79
80 { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, 0, 0, 1, EVP_des_ede3_cbc },
81 { "blowfish-cbc",
82 SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_bf_cbc },
83 { "cast128-cbc",
84 SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_cast5_cbc },
85 { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 0, EVP_rc4 },
86 { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 0, 0, 1536, 0, EVP_rc4 },
87 { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 0, 0, 1536, 0, EVP_rc4 },
88 { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 1, EVP_aes_128_cbc },
89 { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 1, EVP_aes_192_cbc },
90 { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc },
91 { "rijndael-cbc@lysator.liu.se",
92 SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc },
93 { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 0, EVP_aes_128_ctr },
94 { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 0, EVP_aes_192_ctr },
95 { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 0, EVP_aes_256_ctr },
96 #ifdef OPENSSL_HAVE_EVPGCM
97 { "aes128-gcm@openssh.com",
98 SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm },
99 { "aes256-gcm@openssh.com",
100 SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm },
101 #endif
102 { "chacha20-poly1305@openssh.com",
103 SSH_CIPHER_SSH2, 8, 64, 0, 16, 0, CFLAG_CHACHAPOLY, NULL },
104 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL }
105 };
106
107 /*--*/
108
109 /* Returns a list of supported ciphers separated by the specified char. */
110 char *
cipher_alg_list(char sep,int auth_only)111 cipher_alg_list(char sep, int auth_only)
112 {
113 char *ret = NULL;
114 size_t nlen, rlen = 0;
115 const Cipher *c;
116
117 for (c = ciphers; c->name != NULL; c++) {
118 if (c->number != SSH_CIPHER_SSH2)
119 continue;
120 if (auth_only && c->auth_len == 0)
121 continue;
122 if (ret != NULL)
123 ret[rlen++] = sep;
124 nlen = strlen(c->name);
125 ret = xrealloc(ret, 1, rlen + nlen + 2);
126 memcpy(ret + rlen, c->name, nlen + 1);
127 rlen += nlen;
128 }
129 return ret;
130 }
131
132 u_int
cipher_blocksize(const Cipher * c)133 cipher_blocksize(const Cipher *c)
134 {
135 return (c->block_size);
136 }
137
138 u_int
cipher_keylen(const Cipher * c)139 cipher_keylen(const Cipher *c)
140 {
141 return (c->key_len);
142 }
143
144 u_int
cipher_seclen(const Cipher * c)145 cipher_seclen(const Cipher *c)
146 {
147 if (strcmp("3des-cbc", c->name) == 0)
148 return 14;
149 return cipher_keylen(c);
150 }
151
152 u_int
cipher_authlen(const Cipher * c)153 cipher_authlen(const Cipher *c)
154 {
155 return (c->auth_len);
156 }
157
158 u_int
cipher_ivlen(const Cipher * c)159 cipher_ivlen(const Cipher *c)
160 {
161 /*
162 * Default is cipher block size, except for chacha20+poly1305 that
163 * needs no IV. XXX make iv_len == -1 default?
164 */
165 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ?
166 c->iv_len : c->block_size;
167 }
168
169 u_int
cipher_get_number(const Cipher * c)170 cipher_get_number(const Cipher *c)
171 {
172 return (c->number);
173 }
174
175 u_int
cipher_is_cbc(const Cipher * c)176 cipher_is_cbc(const Cipher *c)
177 {
178 return (c->flags & CFLAG_CBC) != 0;
179 }
180
181 u_int
cipher_mask_ssh1(int client)182 cipher_mask_ssh1(int client)
183 {
184 u_int mask = 0;
185 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
186 mask |= 1 << SSH_CIPHER_BLOWFISH;
187 if (client) {
188 mask |= 1 << SSH_CIPHER_DES;
189 }
190 return mask;
191 }
192
193 const Cipher *
cipher_by_name(const char * name)194 cipher_by_name(const char *name)
195 {
196 const Cipher *c;
197 for (c = ciphers; c->name != NULL; c++)
198 if (strcmp(c->name, name) == 0)
199 return c;
200 return NULL;
201 }
202
203 const Cipher *
cipher_by_number(int id)204 cipher_by_number(int id)
205 {
206 const Cipher *c;
207 for (c = ciphers; c->name != NULL; c++)
208 if (c->number == id)
209 return c;
210 return NULL;
211 }
212
213 #define CIPHER_SEP ","
214 int
ciphers_valid(const char * names)215 ciphers_valid(const char *names)
216 {
217 const Cipher *c;
218 char *cipher_list, *cp;
219 char *p;
220
221 if (names == NULL || strcmp(names, "") == 0)
222 return 0;
223 cipher_list = cp = xstrdup(names);
224 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
225 (p = strsep(&cp, CIPHER_SEP))) {
226 c = cipher_by_name(p);
227 if (c == NULL || c->number != SSH_CIPHER_SSH2) {
228 debug("bad cipher %s [%s]", p, names);
229 free(cipher_list);
230 return 0;
231 }
232 }
233 debug3("ciphers ok: [%s]", names);
234 free(cipher_list);
235 return 1;
236 }
237
238 /*
239 * Parses the name of the cipher. Returns the number of the corresponding
240 * cipher, or -1 on error.
241 */
242
243 int
cipher_number(const char * name)244 cipher_number(const char *name)
245 {
246 const Cipher *c;
247 if (name == NULL)
248 return -1;
249 for (c = ciphers; c->name != NULL; c++)
250 if (strcasecmp(c->name, name) == 0)
251 return c->number;
252 return -1;
253 }
254
255 char *
cipher_name(int id)256 cipher_name(int id)
257 {
258 const Cipher *c = cipher_by_number(id);
259 return (c==NULL) ? "<unknown>" : c->name;
260 }
261
262 void
cipher_init(CipherContext * cc,const Cipher * cipher,const u_char * key,u_int keylen,const u_char * iv,u_int ivlen,int do_encrypt)263 cipher_init(CipherContext *cc, const Cipher *cipher,
264 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
265 int do_encrypt)
266 {
267 static int dowarn = 1;
268 #ifdef SSH_OLD_EVP
269 EVP_CIPHER *type;
270 #else
271 const EVP_CIPHER *type;
272 int klen;
273 #endif
274 u_char *junk, *discard;
275
276 if (cipher->number == SSH_CIPHER_DES) {
277 if (dowarn) {
278 error("Warning: use of DES is strongly discouraged "
279 "due to cryptographic weaknesses");
280 dowarn = 0;
281 }
282 if (keylen > 8)
283 keylen = 8;
284 }
285 cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
286 cc->encrypt = do_encrypt;
287
288 if (keylen < cipher->key_len)
289 fatal("cipher_init: key length %d is insufficient for %s.",
290 keylen, cipher->name);
291 if (iv != NULL && ivlen < cipher_ivlen(cipher))
292 fatal("cipher_init: iv length %d is insufficient for %s.",
293 ivlen, cipher->name);
294 cc->cipher = cipher;
295
296 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
297 chachapoly_init(&cc->cp_ctx, key, keylen);
298 return;
299 }
300 type = (*cipher->evptype)();
301 EVP_CIPHER_CTX_init(&cc->evp);
302 #ifdef SSH_OLD_EVP
303 if (type->key_len > 0 && type->key_len != keylen) {
304 debug("cipher_init: set keylen (%d -> %d)",
305 type->key_len, keylen);
306 type->key_len = keylen;
307 }
308 EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
309 (do_encrypt == CIPHER_ENCRYPT));
310 #else
311 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
312 (do_encrypt == CIPHER_ENCRYPT)) == 0)
313 fatal("cipher_init: EVP_CipherInit failed for %s",
314 cipher->name);
315 if (cipher_authlen(cipher) &&
316 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
317 -1, (u_char *)iv))
318 fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s",
319 cipher->name);
320 klen = EVP_CIPHER_CTX_key_length(&cc->evp);
321 if (klen > 0 && keylen != (u_int)klen) {
322 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
323 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
324 fatal("cipher_init: set keylen failed (%d -> %d)",
325 klen, keylen);
326 }
327 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
328 fatal("cipher_init: EVP_CipherInit: set key failed for %s",
329 cipher->name);
330 #endif
331
332 if (cipher->discard_len > 0) {
333 junk = xmalloc(cipher->discard_len);
334 discard = xmalloc(cipher->discard_len);
335 if (EVP_Cipher(&cc->evp, discard, junk,
336 cipher->discard_len) == 0)
337 fatal("evp_crypt: EVP_Cipher failed during discard");
338 explicit_bzero(discard, cipher->discard_len);
339 free(junk);
340 free(discard);
341 }
342 }
343
344 /*
345 * cipher_crypt() operates as following:
346 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
347 * Theses bytes are treated as additional authenticated data for
348 * authenticated encryption modes.
349 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
350 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
351 * This tag is written on encryption and verified on decryption.
352 * Both 'aadlen' and 'authlen' can be set to 0.
353 * cipher_crypt() returns 0 on success and -1 if the decryption integrity
354 * check fails.
355 */
356 int
cipher_crypt(CipherContext * cc,u_int seqnr,u_char * dest,const u_char * src,u_int len,u_int aadlen,u_int authlen)357 cipher_crypt(CipherContext *cc, u_int seqnr, u_char *dest, const u_char *src,
358 u_int len, u_int aadlen, u_int authlen)
359 {
360 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
361 return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src, len,
362 aadlen, authlen, cc->encrypt);
363 if (authlen) {
364 u_char lastiv[1];
365
366 if (authlen != cipher_authlen(cc->cipher))
367 fatal("%s: authlen mismatch %d", __func__, authlen);
368 /* increment IV */
369 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN,
370 1, lastiv))
371 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__);
372 /* set tag on decyption */
373 if (!cc->encrypt &&
374 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG,
375 authlen, (u_char *)src + aadlen + len))
376 fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__);
377 }
378 if (aadlen) {
379 if (authlen &&
380 EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0)
381 fatal("%s: EVP_Cipher(aad) failed", __func__);
382 memcpy(dest, src, aadlen);
383 }
384 if (len % cc->cipher->block_size)
385 fatal("%s: bad plaintext length %d", __func__, len);
386 if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen,
387 len) < 0)
388 fatal("%s: EVP_Cipher failed", __func__);
389 if (authlen) {
390 /* compute tag (on encrypt) or verify tag (on decrypt) */
391 if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) {
392 if (cc->encrypt)
393 fatal("%s: EVP_Cipher(final) failed", __func__);
394 else
395 return -1;
396 }
397 if (cc->encrypt &&
398 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG,
399 authlen, dest + aadlen + len))
400 fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__);
401 }
402 return 0;
403 }
404
405 /* Extract the packet length, including any decryption necessary beforehand */
406 int
cipher_get_length(CipherContext * cc,u_int * plenp,u_int seqnr,const u_char * cp,u_int len)407 cipher_get_length(CipherContext *cc, u_int *plenp, u_int seqnr,
408 const u_char *cp, u_int len)
409 {
410 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
411 return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr,
412 cp, len);
413 if (len < 4)
414 return -1;
415 *plenp = get_u32(cp);
416 return 0;
417 }
418
419 void
cipher_cleanup(CipherContext * cc)420 cipher_cleanup(CipherContext *cc)
421 {
422 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
423 explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx));
424 else if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
425 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
426 }
427
428 /*
429 * Selects the cipher, and keys if by computing the MD5 checksum of the
430 * passphrase and using the resulting 16 bytes as the key.
431 */
432
433 void
cipher_set_key_string(CipherContext * cc,const Cipher * cipher,const char * passphrase,int do_encrypt)434 cipher_set_key_string(CipherContext *cc, const Cipher *cipher,
435 const char *passphrase, int do_encrypt)
436 {
437 u_char digest[16];
438
439 if (ssh_digest_memory(SSH_DIGEST_MD5, passphrase, strlen(passphrase),
440 digest, sizeof(digest)) < 0)
441 fatal("%s: md5 failed", __func__);
442
443 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
444
445 explicit_bzero(digest, sizeof(digest));
446 }
447
448 /*
449 * Exports an IV from the CipherContext required to export the key
450 * state back from the unprivileged child to the privileged parent
451 * process.
452 */
453
454 int
cipher_get_keyiv_len(const CipherContext * cc)455 cipher_get_keyiv_len(const CipherContext *cc)
456 {
457 const Cipher *c = cc->cipher;
458 int ivlen;
459
460 if (c->number == SSH_CIPHER_3DES)
461 ivlen = 24;
462 else if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
463 ivlen = 0;
464 else
465 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
466 return (ivlen);
467 }
468
469 void
cipher_get_keyiv(CipherContext * cc,u_char * iv,u_int len)470 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
471 {
472 const Cipher *c = cc->cipher;
473 int evplen;
474
475 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
476 if (len != 0)
477 fatal("%s: wrong iv length %d != %d", __func__, len, 0);
478 return;
479 }
480
481 switch (c->number) {
482 case SSH_CIPHER_SSH2:
483 case SSH_CIPHER_DES:
484 case SSH_CIPHER_BLOWFISH:
485 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
486 if (evplen <= 0)
487 return;
488 if ((u_int)evplen != len)
489 fatal("%s: wrong iv length %d != %d", __func__,
490 evplen, len);
491 #ifdef USE_BUILTIN_RIJNDAEL
492 if (c->evptype == evp_rijndael)
493 ssh_rijndael_iv(&cc->evp, 0, iv, len);
494 else
495 #endif
496 #ifndef OPENSSL_HAVE_EVPCTR
497 if (c->evptype == evp_aes_128_ctr)
498 ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
499 else
500 #endif
501 memcpy(iv, cc->evp.iv, len);
502 break;
503 case SSH_CIPHER_3DES:
504 ssh1_3des_iv(&cc->evp, 0, iv, 24);
505 break;
506 default:
507 fatal("%s: bad cipher %d", __func__, c->number);
508 }
509 }
510
511 void
cipher_set_keyiv(CipherContext * cc,u_char * iv)512 cipher_set_keyiv(CipherContext *cc, u_char *iv)
513 {
514 const Cipher *c = cc->cipher;
515 int evplen = 0;
516
517 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
518 return;
519
520 switch (c->number) {
521 case SSH_CIPHER_SSH2:
522 case SSH_CIPHER_DES:
523 case SSH_CIPHER_BLOWFISH:
524 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
525 if (evplen == 0)
526 return;
527 #ifdef USE_BUILTIN_RIJNDAEL
528 if (c->evptype == evp_rijndael)
529 ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
530 else
531 #endif
532 #ifndef OPENSSL_HAVE_EVPCTR
533 if (c->evptype == evp_aes_128_ctr)
534 ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
535 else
536 #endif
537 memcpy(cc->evp.iv, iv, evplen);
538 break;
539 case SSH_CIPHER_3DES:
540 ssh1_3des_iv(&cc->evp, 1, iv, 24);
541 break;
542 default:
543 fatal("%s: bad cipher %d", __func__, c->number);
544 }
545 }
546
547 int
cipher_get_keycontext(const CipherContext * cc,u_char * dat)548 cipher_get_keycontext(const CipherContext *cc, u_char *dat)
549 {
550 const Cipher *c = cc->cipher;
551 int plen = 0;
552
553 if (c->evptype == EVP_rc4) {
554 plen = EVP_X_STATE_LEN(cc->evp);
555 if (dat == NULL)
556 return (plen);
557 memcpy(dat, EVP_X_STATE(cc->evp), plen);
558 }
559 return (plen);
560 }
561
562 void
cipher_set_keycontext(CipherContext * cc,u_char * dat)563 cipher_set_keycontext(CipherContext *cc, u_char *dat)
564 {
565 const Cipher *c = cc->cipher;
566 int plen;
567
568 if (c->evptype == EVP_rc4) {
569 plen = EVP_X_STATE_LEN(cc->evp);
570 memcpy(EVP_X_STATE(cc->evp), dat, plen);
571 }
572 }
573