1/* $NetBSD: cipher.c,v 1.15 2019/04/20 17:16:40 christos Exp $ */
2/* $OpenBSD: cipher.c,v 1.112 2018/09/13 02:08:33 djm Exp $ */
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__RCSID("$NetBSD: cipher.c,v 1.15 2019/04/20 17:16:40 christos Exp $");
41#include <sys/types.h>
42
43#include <string.h>
44#include <stdarg.h>
45#include <stdio.h>
46
47#include "cipher.h"
48#include "misc.h"
49#include "sshbuf.h"
50#include "ssherr.h"
51#include "digest.h"
52
53
54struct sshcipher_ctx {
55 int plaintext;
56 int encrypt;
57 EVP_CIPHER_CTX *evp;
58 struct chachapoly_ctx cp_ctx; /* XXX union with evp? */
59 struct aesctr_ctx ac_ctx; /* XXX union with evp? */
60 const struct sshcipher *cipher;
61};
62
63struct sshcipher {
64 const char *name;
65 u_int block_size;
66 u_int key_len;
67 u_int iv_len; /* defaults to block_size */
68 u_int auth_len;
69 u_int flags;
70#define CFLAG_CBC (1<<0)
71#define CFLAG_CHACHAPOLY (1<<1)
72#define CFLAG_AESCTR (1<<2)
73#define CFLAG_NONE (1<<3)
74#define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */
75#ifdef WITH_OPENSSL
76 const EVP_CIPHER *(*evptype)(void);
77#else
78 void *ignored;
79#endif
80};
81
82static const struct sshcipher ciphers[] = {
83#ifdef WITH_OPENSSL
84 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc },
85 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc },
86 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc },
87 { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
88 { "rijndael-cbc@lysator.liu.se",
89 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
90 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr },
91 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr },
92 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr },
93 { "aes128-gcm@openssh.com",
94 16, 16, 12, 16, 0, EVP_aes_128_gcm },
95 { "aes256-gcm@openssh.com",
96 16, 32, 12, 16, 0, EVP_aes_256_gcm },
97#else
98 { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL },
99 { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL },
100 { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL },
101#endif
102 { "chacha20-poly1305@openssh.com",
103 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL },
104 { "none", 8, 0, 0, 0, CFLAG_NONE, NULL },
105
106 { NULL, 0, 0, 0, 0, 0, NULL }
107};
108
109/*--*/
110
111/* Returns a comma-separated list of supported ciphers. */
112char *
113cipher_alg_list(char sep, int auth_only)
114{
115 char *tmp, *ret = NULL;
116 size_t nlen, rlen = 0;
117 const struct sshcipher *c;
118
119 for (c = ciphers; c->name != NULL; c++) {
120 if ((c->flags & CFLAG_INTERNAL) != 0)
121 continue;
122 if (auth_only && c->auth_len == 0)
123 continue;
124 if (ret != NULL)
125 ret[rlen++] = sep;
126 nlen = strlen(c->name);
127 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
128 free(ret);
129 return NULL;
130 }
131 ret = tmp;
132 memcpy(ret + rlen, c->name, nlen + 1);
133 rlen += nlen;
134 }
135 return ret;
136}
137
138u_int
139cipher_blocksize(const struct sshcipher *c)
140{
141 return (c->block_size);
142}
143
144u_int
145cipher_keylen(const struct sshcipher *c)
146{
147 return (c->key_len);
148}
149
150u_int
151cipher_seclen(const struct sshcipher *c)
152{
153 if (strcmp("3des-cbc", c->name) == 0)
154 return 14;
155 return cipher_keylen(c);
156}
157
158u_int
159cipher_authlen(const struct sshcipher *c)
160{
161 return (c->auth_len);
162}
163
164u_int
165cipher_ivlen(const struct sshcipher *c)
166{
167 /*
168 * Default is cipher block size, except for chacha20+poly1305 that
169 * needs no IV. XXX make iv_len == -1 default?
170 */
171 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ?
172 c->iv_len : c->block_size;
173}
174
175u_int
176cipher_is_cbc(const struct sshcipher *c)
177{
178 return (c->flags & CFLAG_CBC) != 0;
179}
180
181u_int
182cipher_ctx_is_plaintext(struct sshcipher_ctx *cc)
183{
184 return cc->plaintext;
185}
186
187const struct sshcipher *
188cipher_by_name(const char *name)
189{
190 const struct sshcipher *c;
191 for (c = ciphers; c->name != NULL; c++)
192 if (strcmp(c->name, name) == 0)
193 return c;
194 return NULL;
195}
196
197#define CIPHER_SEP ","
198int
199ciphers_valid(const char *names)
200{
201 const struct sshcipher *c;
202 char *cipher_list, *cp;
203 char *p;
204
205 if (names == NULL || strcmp(names, "") == 0)
206 return 0;
207 if ((cipher_list = cp = strdup(names)) == NULL)
208 return 0;
209 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
210 (p = strsep(&cp, CIPHER_SEP))) {
211 c = cipher_by_name(p);
212 if (c == NULL || (c->flags & (CFLAG_INTERNAL|CFLAG_NONE)) != 0) {
213 free(cipher_list);
214 return 0;
215 }
216 }
217 free(cipher_list);
218 return 1;
219}
220
221const char *
222cipher_warning_message(const struct sshcipher_ctx *cc)
223{
224 if (cc == NULL || cc->cipher == NULL)
225 return NULL;
226 /* XXX repurpose for CBC warning */
227 return NULL;
228}
229
230int
231cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher,
232 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
233 int do_encrypt)
234{
235 struct sshcipher_ctx *cc = NULL;
236 int ret = SSH_ERR_INTERNAL_ERROR;
237#ifdef WITH_OPENSSL
238 const EVP_CIPHER *type;
239 int klen;
240#endif
241
242 *ccp = NULL;
243 if ((cc = calloc(sizeof(*cc), 1)) == NULL)
244 return SSH_ERR_ALLOC_FAIL;
245
246 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0;
247 cc->encrypt = do_encrypt;
248
249 if (keylen < cipher->key_len ||
250 (iv != NULL && ivlen < cipher_ivlen(cipher))) {
251 ret = SSH_ERR_INVALID_ARGUMENT;
252 goto out;
253 }
254
255 cc->cipher = cipher;
256 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
257 ret = chachapoly_init(&cc->cp_ctx, key, keylen);
258 goto out;
259 }
260 if ((cc->cipher->flags & CFLAG_NONE) != 0) {
261 ret = 0;
262 goto out;
263 }
264#ifndef WITH_OPENSSL
265 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
266 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen);
267 aesctr_ivsetup(&cc->ac_ctx, iv);
268 ret = 0;
269 goto out;
270 }
271 ret = SSH_ERR_INVALID_ARGUMENT;
272 goto out;
273#else /* WITH_OPENSSL */
274 type = (*cipher->evptype)();
275 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) {
276 ret = SSH_ERR_ALLOC_FAIL;
277 goto out;
278 }
279 if (EVP_CipherInit(cc->evp, type, NULL, (const u_char *)iv,
280 (do_encrypt == CIPHER_ENCRYPT)) == 0) {
281 ret = SSH_ERR_LIBCRYPTO_ERROR;
282 goto out;
283 }
284 if (cipher_authlen(cipher) &&
285 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
286 -1, __UNCONST(iv))) {
287 ret = SSH_ERR_LIBCRYPTO_ERROR;
288 goto out;
289 }
290 klen = EVP_CIPHER_CTX_key_length(cc->evp);
291 if (klen > 0 && keylen != (u_int)klen) {
292 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) {
293 ret = SSH_ERR_LIBCRYPTO_ERROR;
294 goto out;
295 }
296 }
297 /* in OpenSSL 1.1.0, EVP_CipherInit clears all previous setups;
298 use EVP_CipherInit_ex for augmenting */
299 if (EVP_CipherInit_ex(cc->evp, NULL, NULL, __UNCONST(key), NULL, -1) == 0) {
300 ret = SSH_ERR_LIBCRYPTO_ERROR;
301 goto out;
302 }
303 ret = 0;
304#endif /* WITH_OPENSSL */
305 out:
306 if (ret == 0) {
307 /* success */
308 *ccp = cc;
309 } else {
310 if (cc != NULL) {
311#ifdef WITH_OPENSSL
312 EVP_CIPHER_CTX_free(cc->evp);
313#endif /* WITH_OPENSSL */
314 explicit_bzero(cc, sizeof(*cc));
315 free(cc);
316 }
317 }
318 return ret;
319}
320
321/*
322 * cipher_crypt() operates as following:
323 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
324 * Theses bytes are treated as additional authenticated data for
325 * authenticated encryption modes.
326 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
327 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
328 * This tag is written on encryption and verified on decryption.
329 * Both 'aadlen' and 'authlen' can be set to 0.
330 */
331int
332cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest,
333 const u_char *src, u_int len, u_int aadlen, u_int authlen)
334{
335 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
336 return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src,
337 len, aadlen, authlen, cc->encrypt);
338 }
339 if ((cc->cipher->flags & CFLAG_NONE) != 0) {
340 memcpy(dest, src, aadlen + len);
341 return 0;
342 }
343#ifndef WITH_OPENSSL
344 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
345 if (aadlen)
346 memcpy(dest, src, aadlen);
347 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen,
348 dest + aadlen, len);
349 return 0;
350 }
351 return SSH_ERR_INVALID_ARGUMENT;
352#else
353 if (authlen) {
354 u_char lastiv[1];
355
356 if (authlen != cipher_authlen(cc->cipher))
357 return SSH_ERR_INVALID_ARGUMENT;
358 /* increment IV */
359 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
360 1, lastiv))
361 return SSH_ERR_LIBCRYPTO_ERROR;
362 /* set tag on decyption */
363 if (!cc->encrypt &&
364 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG,
365 authlen, __UNCONST(src + aadlen + len)))
366 return SSH_ERR_LIBCRYPTO_ERROR;
367 }
368 if (aadlen) {
369 if (authlen &&
370 EVP_Cipher(cc->evp, NULL, (const u_char *)src, aadlen) < 0)
371 return SSH_ERR_LIBCRYPTO_ERROR;
372 memcpy(dest, src, aadlen);
373 }
374 if (len % cc->cipher->block_size)
375 return SSH_ERR_INVALID_ARGUMENT;
376 if (EVP_Cipher(cc->evp, dest + aadlen, (const u_char *)src + aadlen,
377 len) < 0)
378 return SSH_ERR_LIBCRYPTO_ERROR;
379 if (authlen) {
380 /* compute tag (on encrypt) or verify tag (on decrypt) */
381 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0)
382 return cc->encrypt ?
383 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID;
384 if (cc->encrypt &&
385 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG,
386 authlen, dest + aadlen + len))
387 return SSH_ERR_LIBCRYPTO_ERROR;
388 }
389 return 0;
390#endif
391}
392
393/* Extract the packet length, including any decryption necessary beforehand */
394int
395cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr,
396 const u_char *cp, u_int len)
397{
398 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
399 return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr,
400 cp, len);
401 if (len < 4)
402 return SSH_ERR_MESSAGE_INCOMPLETE;
403 *plenp = PEEK_U32(cp);
404 return 0;
405}
406
407void
408cipher_free(struct sshcipher_ctx *cc)
409{
410 if (cc == NULL)
411 return;
412 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
413 explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx));
414 else if ((cc->cipher->flags & CFLAG_AESCTR) != 0)
415 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx));
416#ifdef WITH_OPENSSL
417 EVP_CIPHER_CTX_free(cc->evp);
418 cc->evp = NULL;
419#endif
420 explicit_bzero(cc, sizeof(*cc));
421 free(cc);
422}
423
424/*
425 * Exports an IV from the sshcipher_ctx required to export the key
426 * state back from the unprivileged child to the privileged parent
427 * process.
428 */
429int
430cipher_get_keyiv_len(const struct sshcipher_ctx *cc)
431{
432 const struct sshcipher *c = cc->cipher;
433
434 if ((c->flags & CFLAG_CHACHAPOLY) != 0)
435 return 0;
436 else if ((c->flags & CFLAG_AESCTR) != 0)
437 return sizeof(cc->ac_ctx.ctr);
438#ifdef WITH_OPENSSL
439 return EVP_CIPHER_CTX_iv_length(cc->evp);
440#else
441 return 0;
442#endif
443}
444
445int
446cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len)
447{
448#ifdef WITH_OPENSSL
449 const struct sshcipher *c = cc->cipher;
450 int evplen;
451#endif
452
453 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
454 if (len != 0)
455 return SSH_ERR_INVALID_ARGUMENT;
456 return 0;
457 }
458 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
459 if (len != sizeof(cc->ac_ctx.ctr))
460 return SSH_ERR_INVALID_ARGUMENT;
461 memcpy(iv, cc->ac_ctx.ctr, len);
462 return 0;
463 }
464 if ((cc->cipher->flags & CFLAG_NONE) != 0)
465 return 0;
466
467#ifdef WITH_OPENSSL
468 evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
469 if (evplen == 0)
470 return 0;
471 else if (evplen < 0)
472 return SSH_ERR_LIBCRYPTO_ERROR;
473 if ((size_t)evplen != len)
474 return SSH_ERR_INVALID_ARGUMENT;
475 if (cipher_authlen(c)) {
476 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
477 len, iv))
478 return SSH_ERR_LIBCRYPTO_ERROR;
479 } else
480 memcpy(iv, EVP_CIPHER_CTX_iv(cc->evp), len);
481#endif
482 return 0;
483}
484
485int
486cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len)
487{
488#ifdef WITH_OPENSSL
489 const struct sshcipher *c = cc->cipher;
490 int evplen = 0;
491#endif
492
493 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
494 return 0;
495 if ((cc->cipher->flags & CFLAG_NONE) != 0)
496 return 0;
497
498#ifdef WITH_OPENSSL
499 evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
500 if (evplen <= 0)
501 return SSH_ERR_LIBCRYPTO_ERROR;
502 if ((size_t)evplen != len)
503 return SSH_ERR_INVALID_ARGUMENT;
504 if (cipher_authlen(c)) {
505 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */
506 if (!EVP_CIPHER_CTX_ctrl(cc->evp,
507 EVP_CTRL_GCM_SET_IV_FIXED, -1, __UNCONST(iv)))
508 return SSH_ERR_LIBCRYPTO_ERROR;
509 } else
510 memcpy(EVP_CIPHER_CTX_iv_noconst(cc->evp), iv, evplen);
511#endif
512 return 0;
513}
514
515