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4f8c6159 | 1 | /* |
a96070d4 | 2 | * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. |
4f8c6159 | 3 | * |
4 | * Redistribution and use in source and binary forms, with or without | |
5 | * modification, are permitted provided that the following conditions | |
6 | * are met: | |
7 | * 1. Redistributions of source code must retain the above copyright | |
8 | * notice, this list of conditions and the following disclaimer. | |
9 | * 2. Redistributions in binary form must reproduce the above copyright | |
10 | * notice, this list of conditions and the following disclaimer in the | |
11 | * documentation and/or other materials provided with the distribution. | |
4f8c6159 | 12 | * |
13 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
15 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
16 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
17 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
18 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
19 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
20 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
21 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
22 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
23 | */ | |
24 | ||
25 | #include "includes.h" | |
54a5250f | 26 | RCSID("$OpenBSD: kex.c,v 1.40 2001/12/28 14:50:54 markus Exp $"); |
4f8c6159 | 27 | |
28 | #include <openssl/crypto.h> | |
4f8c6159 | 29 | |
42f11eb2 | 30 | #include "ssh2.h" |
31 | #include "xmalloc.h" | |
32 | #include "buffer.h" | |
33 | #include "bufaux.h" | |
34 | #include "packet.h" | |
35 | #include "compat.h" | |
36 | #include "cipher.h" | |
4f8c6159 | 37 | #include "kex.h" |
fa08c86b | 38 | #include "key.h" |
42f11eb2 | 39 | #include "log.h" |
b2552997 | 40 | #include "mac.h" |
cab80f75 | 41 | #include "match.h" |
a5c9ffdb | 42 | #include "dispatch.h" |
4f8c6159 | 43 | |
71276795 | 44 | #define KEX_COOKIE_LEN 16 |
45 | ||
396c147e | 46 | /* prototype */ |
47 | static void kex_kexinit_finish(Kex *); | |
48 | static void kex_choose_conf(Kex *); | |
a5c9ffdb | 49 | |
50 | /* put algorithm proposal into buffer */ | |
396c147e | 51 | static void |
a5c9ffdb | 52 | kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX]) |
4f8c6159 | 53 | { |
4f8c6159 | 54 | u_int32_t rand = 0; |
55 | int i; | |
a5c9ffdb | 56 | |
57 | buffer_clear(b); | |
71276795 | 58 | for (i = 0; i < KEX_COOKIE_LEN; i++) { |
4f8c6159 | 59 | if (i % 4 == 0) |
60 | rand = arc4random(); | |
a5c9ffdb | 61 | buffer_put_char(b, rand & 0xff); |
4f8c6159 | 62 | rand >>= 8; |
63 | } | |
4f8c6159 | 64 | for (i = 0; i < PROPOSAL_MAX; i++) |
a5c9ffdb | 65 | buffer_put_cstring(b, proposal[i]); |
66 | buffer_put_char(b, 0); /* first_kex_packet_follows */ | |
67 | buffer_put_int(b, 0); /* uint32 reserved */ | |
4f8c6159 | 68 | } |
69 | ||
a5c9ffdb | 70 | /* parse buffer and return algorithm proposal */ |
396c147e | 71 | static char ** |
a5c9ffdb | 72 | kex_buf2prop(Buffer *raw) |
71276795 | 73 | { |
a5c9ffdb | 74 | Buffer b; |
71276795 | 75 | int i; |
a5c9ffdb | 76 | char **proposal; |
71276795 | 77 | |
a5c9ffdb | 78 | proposal = xmalloc(PROPOSAL_MAX * sizeof(char *)); |
79 | ||
80 | buffer_init(&b); | |
81 | buffer_append(&b, buffer_ptr(raw), buffer_len(raw)); | |
71276795 | 82 | /* skip cookie */ |
83 | for (i = 0; i < KEX_COOKIE_LEN; i++) | |
a5c9ffdb | 84 | buffer_get_char(&b); |
71276795 | 85 | /* extract kex init proposal strings */ |
86 | for (i = 0; i < PROPOSAL_MAX; i++) { | |
a5c9ffdb | 87 | proposal[i] = buffer_get_string(&b,NULL); |
88 | debug2("kex_parse_kexinit: %s", proposal[i]); | |
71276795 | 89 | } |
a5c9ffdb | 90 | /* first kex follows / reserved */ |
91 | i = buffer_get_char(&b); | |
92 | debug2("kex_parse_kexinit: first_kex_follows %d ", i); | |
93 | i = buffer_get_int(&b); | |
94 | debug2("kex_parse_kexinit: reserved %d ", i); | |
95 | buffer_free(&b); | |
96 | return proposal; | |
71276795 | 97 | } |
98 | ||
396c147e | 99 | static void |
a5c9ffdb | 100 | kex_prop_free(char **proposal) |
4f8c6159 | 101 | { |
102 | int i; | |
a5c9ffdb | 103 | |
104 | for (i = 0; i < PROPOSAL_MAX; i++) | |
105 | xfree(proposal[i]); | |
106 | xfree(proposal); | |
4f8c6159 | 107 | } |
108 | ||
396c147e | 109 | static void |
24ca6821 | 110 | kex_protocol_error(int type, int plen, u_int32_t seq, void *ctxt) |
4f8c6159 | 111 | { |
cd332296 | 112 | error("Hm, kex protocol error: type %d plen %d", type, plen); |
a5c9ffdb | 113 | } |
4f8c6159 | 114 | |
396c147e | 115 | static void |
7a37c112 | 116 | kex_clear_dispatch(void) |
117 | { | |
118 | int i; | |
119 | ||
120 | /* Numbers 30-49 are used for kex packets */ | |
121 | for (i = 30; i <= 49; i++) | |
122 | dispatch_set(i, &kex_protocol_error); | |
123 | } | |
124 | ||
a5c9ffdb | 125 | void |
d8ee838b | 126 | kex_finish(Kex *kex) |
a5c9ffdb | 127 | { |
7a37c112 | 128 | kex_clear_dispatch(); |
d8ee838b | 129 | |
a5c9ffdb | 130 | packet_start(SSH2_MSG_NEWKEYS); |
131 | packet_send(); | |
132 | /* packet_write_wait(); */ | |
133 | debug("SSH2_MSG_NEWKEYS sent"); | |
4f8c6159 | 134 | |
cd332296 | 135 | debug("waiting for SSH2_MSG_NEWKEYS"); |
54a5250f | 136 | packet_read_expect(SSH2_MSG_NEWKEYS); |
a5c9ffdb | 137 | debug("SSH2_MSG_NEWKEYS received"); |
a7ca6275 | 138 | |
c422989b | 139 | kex->done = 1; |
a5c9ffdb | 140 | buffer_clear(&kex->peer); |
d1ac6175 | 141 | /* buffer_clear(&kex->my); */ |
a5c9ffdb | 142 | kex->flags &= ~KEX_INIT_SENT; |
a7ca6275 | 143 | xfree(kex->name); |
144 | kex->name = NULL; | |
4f8c6159 | 145 | } |
146 | ||
a5c9ffdb | 147 | void |
148 | kex_send_kexinit(Kex *kex) | |
94ec8c6b | 149 | { |
7a37c112 | 150 | if (kex == NULL) { |
151 | error("kex_send_kexinit: no kex, cannot rekey"); | |
152 | return; | |
153 | } | |
d8ee838b | 154 | if (kex->flags & KEX_INIT_SENT) { |
155 | debug("KEX_INIT_SENT"); | |
156 | return; | |
157 | } | |
c422989b | 158 | kex->done = 0; |
a5c9ffdb | 159 | packet_start(SSH2_MSG_KEXINIT); |
160 | packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my)); | |
161 | packet_send(); | |
162 | debug("SSH2_MSG_KEXINIT sent"); | |
163 | kex->flags |= KEX_INIT_SENT; | |
164 | } | |
2b87da3b | 165 | |
a5c9ffdb | 166 | void |
24ca6821 | 167 | kex_input_kexinit(int type, int plen, u_int32_t seq, void *ctxt) |
a5c9ffdb | 168 | { |
169 | char *ptr; | |
170 | int dlen; | |
bbb4cc1b | 171 | int i; |
a5c9ffdb | 172 | Kex *kex = (Kex *)ctxt; |
94ec8c6b | 173 | |
a5c9ffdb | 174 | debug("SSH2_MSG_KEXINIT received"); |
7a37c112 | 175 | if (kex == NULL) |
176 | fatal("kex_input_kexinit: no kex, cannot rekey"); | |
94ec8c6b | 177 | |
a5c9ffdb | 178 | ptr = packet_get_raw(&dlen); |
179 | buffer_append(&kex->peer, ptr, dlen); | |
94ec8c6b | 180 | |
bbb4cc1b | 181 | /* discard packet */ |
182 | for (i = 0; i < KEX_COOKIE_LEN; i++) | |
183 | packet_get_char(); | |
184 | for (i = 0; i < PROPOSAL_MAX; i++) | |
185 | xfree(packet_get_string(NULL)); | |
186 | packet_get_char(); | |
187 | packet_get_int(); | |
95500969 | 188 | packet_check_eom(); |
bbb4cc1b | 189 | |
a5c9ffdb | 190 | kex_kexinit_finish(kex); |
94ec8c6b | 191 | } |
192 | ||
a5c9ffdb | 193 | Kex * |
d8ee838b | 194 | kex_setup(char *proposal[PROPOSAL_MAX]) |
4f8c6159 | 195 | { |
a5c9ffdb | 196 | Kex *kex; |
4f8c6159 | 197 | |
a5c9ffdb | 198 | kex = xmalloc(sizeof(*kex)); |
199 | memset(kex, 0, sizeof(*kex)); | |
200 | buffer_init(&kex->peer); | |
201 | buffer_init(&kex->my); | |
202 | kex_prop2buf(&kex->my, proposal); | |
c422989b | 203 | kex->done = 0; |
a5c9ffdb | 204 | |
205 | kex_send_kexinit(kex); /* we start */ | |
7a37c112 | 206 | kex_clear_dispatch(); |
a5c9ffdb | 207 | dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); |
7a37c112 | 208 | |
a5c9ffdb | 209 | return kex; |
210 | } | |
4f8c6159 | 211 | |
396c147e | 212 | static void |
a5c9ffdb | 213 | kex_kexinit_finish(Kex *kex) |
214 | { | |
215 | if (!(kex->flags & KEX_INIT_SENT)) | |
216 | kex_send_kexinit(kex); | |
217 | ||
218 | kex_choose_conf(kex); | |
219 | ||
6aacefa7 | 220 | switch (kex->kex_type) { |
a5c9ffdb | 221 | case DH_GRP1_SHA1: |
222 | kexdh(kex); | |
223 | break; | |
224 | case DH_GEX_SHA1: | |
225 | kexgex(kex); | |
226 | break; | |
227 | default: | |
228 | fatal("Unsupported key exchange %d", kex->kex_type); | |
4f8c6159 | 229 | } |
4f8c6159 | 230 | } |
231 | ||
396c147e | 232 | static void |
4f8c6159 | 233 | choose_enc(Enc *enc, char *client, char *server) |
234 | { | |
cab80f75 | 235 | char *name = match_list(client, server, NULL); |
4f8c6159 | 236 | if (name == NULL) |
237 | fatal("no matching cipher found: client %s server %s", client, server); | |
94ec8c6b | 238 | enc->cipher = cipher_by_name(name); |
239 | if (enc->cipher == NULL) | |
240 | fatal("matching cipher is not supported: %s", name); | |
4f8c6159 | 241 | enc->name = name; |
242 | enc->enabled = 0; | |
243 | enc->iv = NULL; | |
244 | enc->key = NULL; | |
245 | } | |
396c147e | 246 | static void |
4f8c6159 | 247 | choose_mac(Mac *mac, char *client, char *server) |
248 | { | |
cab80f75 | 249 | char *name = match_list(client, server, NULL); |
4f8c6159 | 250 | if (name == NULL) |
251 | fatal("no matching mac found: client %s server %s", client, server); | |
b2552997 | 252 | if (mac_init(mac, name) < 0) |
4f8c6159 | 253 | fatal("unsupported mac %s", name); |
b2552997 | 254 | /* truncate the key */ |
255 | if (datafellows & SSH_BUG_HMAC) | |
256 | mac->key_len = 16; | |
4f8c6159 | 257 | mac->name = name; |
4f8c6159 | 258 | mac->key = NULL; |
259 | mac->enabled = 0; | |
260 | } | |
396c147e | 261 | static void |
4f8c6159 | 262 | choose_comp(Comp *comp, char *client, char *server) |
263 | { | |
cab80f75 | 264 | char *name = match_list(client, server, NULL); |
4f8c6159 | 265 | if (name == NULL) |
266 | fatal("no matching comp found: client %s server %s", client, server); | |
267 | if (strcmp(name, "zlib") == 0) { | |
268 | comp->type = 1; | |
269 | } else if (strcmp(name, "none") == 0) { | |
270 | comp->type = 0; | |
271 | } else { | |
272 | fatal("unsupported comp %s", name); | |
273 | } | |
274 | comp->name = name; | |
275 | } | |
396c147e | 276 | static void |
4f8c6159 | 277 | choose_kex(Kex *k, char *client, char *server) |
278 | { | |
cab80f75 | 279 | k->name = match_list(client, server, NULL); |
4f8c6159 | 280 | if (k->name == NULL) |
281 | fatal("no kex alg"); | |
94ec8c6b | 282 | if (strcmp(k->name, KEX_DH1) == 0) { |
283 | k->kex_type = DH_GRP1_SHA1; | |
284 | } else if (strcmp(k->name, KEX_DHGEX) == 0) { | |
285 | k->kex_type = DH_GEX_SHA1; | |
286 | } else | |
4f8c6159 | 287 | fatal("bad kex alg %s", k->name); |
288 | } | |
396c147e | 289 | static void |
4f8c6159 | 290 | choose_hostkeyalg(Kex *k, char *client, char *server) |
291 | { | |
cab80f75 | 292 | char *hostkeyalg = match_list(client, server, NULL); |
fa08c86b | 293 | if (hostkeyalg == NULL) |
4f8c6159 | 294 | fatal("no hostkey alg"); |
fa08c86b | 295 | k->hostkey_type = key_type_from_name(hostkeyalg); |
296 | if (k->hostkey_type == KEY_UNSPEC) | |
297 | fatal("bad hostkey alg '%s'", hostkeyalg); | |
eea39c02 | 298 | xfree(hostkeyalg); |
4f8c6159 | 299 | } |
300 | ||
396c147e | 301 | static void |
d1ac6175 | 302 | kex_choose_conf(Kex *kex) |
4f8c6159 | 303 | { |
d1ac6175 | 304 | Newkeys *newkeys; |
a5c9ffdb | 305 | char **my, **peer; |
306 | char **cprop, **sprop; | |
d1ac6175 | 307 | int nenc, nmac, ncomp; |
4f8c6159 | 308 | int mode; |
309 | int ctos; /* direction: if true client-to-server */ | |
310 | int need; | |
4f8c6159 | 311 | |
d1ac6175 | 312 | my = kex_buf2prop(&kex->my); |
313 | peer = kex_buf2prop(&kex->peer); | |
a5c9ffdb | 314 | |
d1ac6175 | 315 | if (kex->server) { |
a5c9ffdb | 316 | cprop=peer; |
317 | sprop=my; | |
318 | } else { | |
319 | cprop=my; | |
320 | sprop=peer; | |
321 | } | |
4f8c6159 | 322 | |
c422989b | 323 | /* Algorithm Negotiation */ |
4f8c6159 | 324 | for (mode = 0; mode < MODE_MAX; mode++) { |
d1ac6175 | 325 | newkeys = xmalloc(sizeof(*newkeys)); |
326 | memset(newkeys, 0, sizeof(*newkeys)); | |
c422989b | 327 | kex->newkeys[mode] = newkeys; |
d1ac6175 | 328 | ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN); |
4f8c6159 | 329 | nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC; |
330 | nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC; | |
331 | ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC; | |
d1ac6175 | 332 | choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]); |
333 | choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]); | |
334 | choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]); | |
4f8c6159 | 335 | debug("kex: %s %s %s %s", |
336 | ctos ? "client->server" : "server->client", | |
d1ac6175 | 337 | newkeys->enc.name, |
338 | newkeys->mac.name, | |
339 | newkeys->comp.name); | |
4f8c6159 | 340 | } |
d1ac6175 | 341 | choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]); |
342 | choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], | |
4f8c6159 | 343 | sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]); |
4f8c6159 | 344 | need = 0; |
345 | for (mode = 0; mode < MODE_MAX; mode++) { | |
c422989b | 346 | newkeys = kex->newkeys[mode]; |
d1ac6175 | 347 | if (need < newkeys->enc.cipher->key_len) |
348 | need = newkeys->enc.cipher->key_len; | |
349 | if (need < newkeys->enc.cipher->block_size) | |
350 | need = newkeys->enc.cipher->block_size; | |
351 | if (need < newkeys->mac.key_len) | |
352 | need = newkeys->mac.key_len; | |
4f8c6159 | 353 | } |
71276795 | 354 | /* XXX need runden? */ |
d1ac6175 | 355 | kex->we_need = need; |
a5c9ffdb | 356 | |
357 | kex_prop_free(my); | |
358 | kex_prop_free(peer); | |
a5c9ffdb | 359 | } |
360 | ||
396c147e | 361 | static u_char * |
d1ac6175 | 362 | derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret) |
a5c9ffdb | 363 | { |
364 | Buffer b; | |
365 | EVP_MD *evp_md = EVP_sha1(); | |
366 | EVP_MD_CTX md; | |
367 | char c = id; | |
368 | int have; | |
369 | int mdsz = evp_md->md_size; | |
c422989b | 370 | u_char *digest = xmalloc(roundup(need, mdsz)); |
a5c9ffdb | 371 | |
372 | buffer_init(&b); | |
373 | buffer_put_bignum2(&b, shared_secret); | |
374 | ||
c422989b | 375 | /* K1 = HASH(K || H || "A" || session_id) */ |
a5c9ffdb | 376 | EVP_DigestInit(&md, evp_md); |
eef7adcb | 377 | if (!(datafellows & SSH_BUG_DERIVEKEY)) |
378 | EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); | |
c422989b | 379 | EVP_DigestUpdate(&md, hash, mdsz); |
380 | EVP_DigestUpdate(&md, &c, 1); | |
d1ac6175 | 381 | EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len); |
a5c9ffdb | 382 | EVP_DigestFinal(&md, digest, NULL); |
383 | ||
c422989b | 384 | /* |
385 | * expand key: | |
386 | * Kn = HASH(K || H || K1 || K2 || ... || Kn-1) | |
387 | * Key = K1 || K2 || ... || Kn | |
388 | */ | |
a5c9ffdb | 389 | for (have = mdsz; need > have; have += mdsz) { |
390 | EVP_DigestInit(&md, evp_md); | |
eef7adcb | 391 | if (!(datafellows & SSH_BUG_DERIVEKEY)) |
392 | EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); | |
a5c9ffdb | 393 | EVP_DigestUpdate(&md, hash, mdsz); |
394 | EVP_DigestUpdate(&md, digest, have); | |
395 | EVP_DigestFinal(&md, digest + have, NULL); | |
396 | } | |
397 | buffer_free(&b); | |
398 | #ifdef DEBUG_KEX | |
399 | fprintf(stderr, "key '%c'== ", c); | |
400 | dump_digest("key", digest, need); | |
401 | #endif | |
402 | return digest; | |
4f8c6159 | 403 | } |
404 | ||
c422989b | 405 | Newkeys *current_keys[MODE_MAX]; |
d1ac6175 | 406 | |
cab80f75 | 407 | #define NKEYS 6 |
a5c9ffdb | 408 | void |
d1ac6175 | 409 | kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret) |
4f8c6159 | 410 | { |
1e3b8b07 | 411 | u_char *keys[NKEYS]; |
d1ac6175 | 412 | int i, mode, ctos; |
4f8c6159 | 413 | |
414 | for (i = 0; i < NKEYS; i++) | |
d1ac6175 | 415 | keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret); |
4f8c6159 | 416 | |
d1ac6175 | 417 | debug("kex_derive_keys"); |
4f8c6159 | 418 | for (mode = 0; mode < MODE_MAX; mode++) { |
c422989b | 419 | current_keys[mode] = kex->newkeys[mode]; |
420 | kex->newkeys[mode] = NULL; | |
d1ac6175 | 421 | ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN); |
c422989b | 422 | current_keys[mode]->enc.iv = keys[ctos ? 0 : 1]; |
423 | current_keys[mode]->enc.key = keys[ctos ? 2 : 3]; | |
424 | current_keys[mode]->mac.key = keys[ctos ? 4 : 5]; | |
4f8c6159 | 425 | } |
4f8c6159 | 426 | } |
a5c9ffdb | 427 | |
d1ac6175 | 428 | Newkeys * |
429 | kex_get_newkeys(int mode) | |
430 | { | |
c422989b | 431 | Newkeys *ret; |
432 | ||
433 | ret = current_keys[mode]; | |
434 | current_keys[mode] = NULL; | |
435 | return ret; | |
d1ac6175 | 436 | } |
437 | ||
a5c9ffdb | 438 | #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) |
439 | void | |
440 | dump_digest(char *msg, u_char *digest, int len) | |
441 | { | |
442 | int i; | |
443 | ||
444 | fprintf(stderr, "%s\n", msg); | |
6aacefa7 | 445 | for (i = 0; i< len; i++) { |
a5c9ffdb | 446 | fprintf(stderr, "%02x", digest[i]); |
447 | if (i%32 == 31) | |
448 | fprintf(stderr, "\n"); | |
449 | else if (i%8 == 7) | |
450 | fprintf(stderr, " "); | |
451 | } | |
452 | fprintf(stderr, "\n"); | |
453 | } | |
454 | #endif |