1 /* $OpenBSD: kex.c,v 1.86 2010/09/22 05:01:29 djm Exp $ */ 2 /* 3 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 28 #include <sys/param.h> 29 30 #include <signal.h> 31 #include <stdarg.h> 32 #include <stdio.h> 33 #include <stdlib.h> 34 #include <string.h> 35 36 #include <openssl/crypto.h> 37 38 #include "xmalloc.h" 39 #include "ssh2.h" 40 #include "buffer.h" 41 #include "packet.h" 42 #include "compat.h" 43 #include "cipher.h" 44 #include "key.h" 45 #include "kex.h" 46 #include "log.h" 47 #include "mac.h" 48 #include "match.h" 49 #include "dispatch.h" 50 #include "monitor.h" 51 #include "roaming.h" 52 #include "canohost.h" 53 54 #if OPENSSL_VERSION_NUMBER >= 0x00907000L 55 # if defined(HAVE_EVP_SHA256) 56 # define evp_ssh_sha256 EVP_sha256 57 # else 58 extern const EVP_MD *evp_ssh_sha256(void); 59 # endif 60 #endif 61 62 /* prototype */ 63 static void kex_kexinit_finish(Kex *); 64 static void kex_choose_conf(Kex *); 65 66 /* Validate KEX method name list */ 67 int 68 kex_names_valid(const char *names) 69 { 70 char *s, *cp, *p; 71 72 if (names == NULL || strcmp(names, "") == 0) 73 return 0; 74 s = cp = xstrdup(names); 75 for ((p = strsep(&cp, ",")); p && *p != '\0'; 76 (p = strsep(&cp, ","))) { 77 if (strcmp(p, KEX_DHGEX_SHA256) != 0 && 78 strcmp(p, KEX_DHGEX_SHA1) != 0 && 79 strcmp(p, KEX_DH14) != 0 && 80 strcmp(p, KEX_DH1) != 0 && 81 (strncmp(p, KEX_ECDH_SHA2_STEM, 82 sizeof(KEX_ECDH_SHA2_STEM) - 1) != 0 || 83 kex_ecdh_name_to_nid(p) == -1)) { 84 error("Unsupported KEX algorithm \"%.100s\"", p); 85 xfree(s); 86 return 0; 87 } 88 } 89 debug3("kex names ok: [%s]", names); 90 xfree(s); 91 return 1; 92 } 93 94 /* put algorithm proposal into buffer */ 95 /* used in sshconnect.c as well as kex.c */ 96 void 97 kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX]) 98 { 99 u_int i; 100 101 buffer_clear(b); 102 /* 103 * add a dummy cookie, the cookie will be overwritten by 104 * kex_send_kexinit(), each time a kexinit is set 105 */ 106 for (i = 0; i < KEX_COOKIE_LEN; i++) 107 buffer_put_char(b, 0); 108 for (i = 0; i < PROPOSAL_MAX; i++) 109 buffer_put_cstring(b, proposal[i]); 110 buffer_put_char(b, 0); /* first_kex_packet_follows */ 111 buffer_put_int(b, 0); /* uint32 reserved */ 112 } 113 114 /* parse buffer and return algorithm proposal */ 115 static char ** 116 kex_buf2prop(Buffer *raw, int *first_kex_follows) 117 { 118 Buffer b; 119 u_int i; 120 char **proposal; 121 122 proposal = xcalloc(PROPOSAL_MAX, sizeof(char *)); 123 124 buffer_init(&b); 125 buffer_append(&b, buffer_ptr(raw), buffer_len(raw)); 126 /* skip cookie */ 127 for (i = 0; i < KEX_COOKIE_LEN; i++) 128 buffer_get_char(&b); 129 /* extract kex init proposal strings */ 130 for (i = 0; i < PROPOSAL_MAX; i++) { 131 proposal[i] = buffer_get_cstring(&b,NULL); 132 debug2("kex_parse_kexinit: %s", proposal[i]); 133 } 134 /* first kex follows / reserved */ 135 i = buffer_get_char(&b); 136 if (first_kex_follows != NULL) 137 *first_kex_follows = i; 138 debug2("kex_parse_kexinit: first_kex_follows %d ", i); 139 i = buffer_get_int(&b); 140 debug2("kex_parse_kexinit: reserved %u ", i); 141 buffer_free(&b); 142 return proposal; 143 } 144 145 static void 146 kex_prop_free(char **proposal) 147 { 148 u_int i; 149 150 for (i = 0; i < PROPOSAL_MAX; i++) 151 xfree(proposal[i]); 152 xfree(proposal); 153 } 154 155 /* ARGSUSED */ 156 static void 157 kex_protocol_error(int type, u_int32_t seq, void *ctxt) 158 { 159 error("Hm, kex protocol error: type %d seq %u", type, seq); 160 } 161 162 static void 163 kex_reset_dispatch(void) 164 { 165 dispatch_range(SSH2_MSG_TRANSPORT_MIN, 166 SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error); 167 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 168 } 169 170 void 171 kex_finish(Kex *kex) 172 { 173 kex_reset_dispatch(); 174 175 packet_start(SSH2_MSG_NEWKEYS); 176 packet_send(); 177 /* packet_write_wait(); */ 178 debug("SSH2_MSG_NEWKEYS sent"); 179 180 debug("expecting SSH2_MSG_NEWKEYS"); 181 packet_read_expect(SSH2_MSG_NEWKEYS); 182 packet_check_eom(); 183 debug("SSH2_MSG_NEWKEYS received"); 184 185 kex->done = 1; 186 buffer_clear(&kex->peer); 187 /* buffer_clear(&kex->my); */ 188 kex->flags &= ~KEX_INIT_SENT; 189 xfree(kex->name); 190 kex->name = NULL; 191 } 192 193 void 194 kex_send_kexinit(Kex *kex) 195 { 196 u_int32_t rnd = 0; 197 u_char *cookie; 198 u_int i; 199 200 if (kex == NULL) { 201 error("kex_send_kexinit: no kex, cannot rekey"); 202 return; 203 } 204 if (kex->flags & KEX_INIT_SENT) { 205 debug("KEX_INIT_SENT"); 206 return; 207 } 208 kex->done = 0; 209 210 /* generate a random cookie */ 211 if (buffer_len(&kex->my) < KEX_COOKIE_LEN) 212 fatal("kex_send_kexinit: kex proposal too short"); 213 cookie = buffer_ptr(&kex->my); 214 for (i = 0; i < KEX_COOKIE_LEN; i++) { 215 if (i % 4 == 0) 216 rnd = arc4random(); 217 cookie[i] = rnd; 218 rnd >>= 8; 219 } 220 packet_start(SSH2_MSG_KEXINIT); 221 packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my)); 222 packet_send(); 223 debug("SSH2_MSG_KEXINIT sent"); 224 kex->flags |= KEX_INIT_SENT; 225 } 226 227 /* ARGSUSED */ 228 void 229 kex_input_kexinit(int type, u_int32_t seq, void *ctxt) 230 { 231 char *ptr; 232 u_int i, dlen; 233 Kex *kex = (Kex *)ctxt; 234 235 debug("SSH2_MSG_KEXINIT received"); 236 if (kex == NULL) 237 fatal("kex_input_kexinit: no kex, cannot rekey"); 238 239 ptr = packet_get_raw(&dlen); 240 buffer_append(&kex->peer, ptr, dlen); 241 242 /* discard packet */ 243 for (i = 0; i < KEX_COOKIE_LEN; i++) 244 packet_get_char(); 245 for (i = 0; i < PROPOSAL_MAX; i++) 246 xfree(packet_get_string(NULL)); 247 (void) packet_get_char(); 248 (void) packet_get_int(); 249 packet_check_eom(); 250 251 kex_kexinit_finish(kex); 252 } 253 254 Kex * 255 kex_setup(char *proposal[PROPOSAL_MAX]) 256 { 257 Kex *kex; 258 259 kex = xcalloc(1, sizeof(*kex)); 260 buffer_init(&kex->peer); 261 buffer_init(&kex->my); 262 kex_prop2buf(&kex->my, proposal); 263 kex->done = 0; 264 265 kex_send_kexinit(kex); /* we start */ 266 kex_reset_dispatch(); 267 268 return kex; 269 } 270 271 static void 272 kex_kexinit_finish(Kex *kex) 273 { 274 if (!(kex->flags & KEX_INIT_SENT)) 275 kex_send_kexinit(kex); 276 277 kex_choose_conf(kex); 278 279 if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX && 280 kex->kex[kex->kex_type] != NULL) { 281 (kex->kex[kex->kex_type])(kex); 282 } else { 283 fatal("Unsupported key exchange %d", kex->kex_type); 284 } 285 } 286 287 static void 288 choose_enc(Enc *enc, char *client, char *server) 289 { 290 char *name = match_list(client, server, NULL); 291 if (name == NULL) 292 fatal("no matching cipher found: client %s server %s", 293 client, server); 294 if ((enc->cipher = cipher_by_name(name)) == NULL) 295 fatal("matching cipher is not supported: %s", name); 296 enc->name = name; 297 enc->enabled = 0; 298 enc->iv = NULL; 299 enc->key = NULL; 300 enc->key_len = cipher_keylen(enc->cipher); 301 enc->block_size = cipher_blocksize(enc->cipher); 302 } 303 304 static void 305 choose_mac(Mac *mac, char *client, char *server) 306 { 307 char *name = match_list(client, server, NULL); 308 if (name == NULL) 309 fatal("no matching mac found: client %s server %s", 310 client, server); 311 if (mac_setup(mac, name) < 0) 312 fatal("unsupported mac %s", name); 313 /* truncate the key */ 314 if (datafellows & SSH_BUG_HMAC) 315 mac->key_len = 16; 316 mac->name = name; 317 mac->key = NULL; 318 mac->enabled = 0; 319 } 320 321 static void 322 choose_comp(Comp *comp, char *client, char *server) 323 { 324 char *name = match_list(client, server, NULL); 325 if (name == NULL) 326 fatal("no matching comp found: client %s server %s", client, server); 327 if (strcmp(name, "zlib@openssh.com") == 0) { 328 comp->type = COMP_DELAYED; 329 } else if (strcmp(name, "zlib") == 0) { 330 comp->type = COMP_ZLIB; 331 } else if (strcmp(name, "none") == 0) { 332 comp->type = COMP_NONE; 333 } else { 334 fatal("unsupported comp %s", name); 335 } 336 comp->name = name; 337 } 338 339 static void 340 choose_kex(Kex *k, char *client, char *server) 341 { 342 k->name = match_list(client, server, NULL); 343 if (k->name == NULL) 344 fatal("Unable to negotiate a key exchange method"); 345 if (strcmp(k->name, KEX_DH1) == 0) { 346 k->kex_type = KEX_DH_GRP1_SHA1; 347 k->evp_md = EVP_sha1(); 348 } else if (strcmp(k->name, KEX_DH14) == 0) { 349 k->kex_type = KEX_DH_GRP14_SHA1; 350 k->evp_md = EVP_sha1(); 351 } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) { 352 k->kex_type = KEX_DH_GEX_SHA1; 353 k->evp_md = EVP_sha1(); 354 #if OPENSSL_VERSION_NUMBER >= 0x00907000L 355 } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) { 356 k->kex_type = KEX_DH_GEX_SHA256; 357 k->evp_md = evp_ssh_sha256(); 358 } else if (strncmp(k->name, KEX_ECDH_SHA2_STEM, 359 sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) { 360 k->kex_type = KEX_ECDH_SHA2; 361 k->evp_md = kex_ecdh_name_to_evpmd(k->name); 362 #endif 363 } else 364 fatal("bad kex alg %s", k->name); 365 } 366 367 static void 368 choose_hostkeyalg(Kex *k, char *client, char *server) 369 { 370 char *hostkeyalg = match_list(client, server, NULL); 371 if (hostkeyalg == NULL) 372 fatal("no hostkey alg"); 373 k->hostkey_type = key_type_from_name(hostkeyalg); 374 if (k->hostkey_type == KEY_UNSPEC) 375 fatal("bad hostkey alg '%s'", hostkeyalg); 376 xfree(hostkeyalg); 377 } 378 379 static int 380 proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX]) 381 { 382 static int check[] = { 383 PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1 384 }; 385 int *idx; 386 char *p; 387 388 for (idx = &check[0]; *idx != -1; idx++) { 389 if ((p = strchr(my[*idx], ',')) != NULL) 390 *p = '\0'; 391 if ((p = strchr(peer[*idx], ',')) != NULL) 392 *p = '\0'; 393 if (strcmp(my[*idx], peer[*idx]) != 0) { 394 debug2("proposal mismatch: my %s peer %s", 395 my[*idx], peer[*idx]); 396 return (0); 397 } 398 } 399 debug2("proposals match"); 400 return (1); 401 } 402 403 static void 404 kex_choose_conf(Kex *kex) 405 { 406 Newkeys *newkeys; 407 char **my, **peer; 408 char **cprop, **sprop; 409 int nenc, nmac, ncomp; 410 u_int mode, ctos, need; 411 int first_kex_follows, type; 412 int log_flag = 0; 413 414 int auth_flag; 415 416 auth_flag = packet_authentication_state(); 417 418 debug ("AUTH STATE IS %d", auth_flag); 419 420 my = kex_buf2prop(&kex->my, NULL); 421 peer = kex_buf2prop(&kex->peer, &first_kex_follows); 422 423 if (kex->server) { 424 cprop=peer; 425 sprop=my; 426 } else { 427 cprop=my; 428 sprop=peer; 429 } 430 431 /* Check whether server offers roaming */ 432 if (!kex->server) { 433 char *roaming; 434 roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL); 435 if (roaming) { 436 kex->roaming = 1; 437 xfree(roaming); 438 } 439 } 440 441 /* Algorithm Negotiation */ 442 for (mode = 0; mode < MODE_MAX; mode++) { 443 newkeys = xcalloc(1, sizeof(*newkeys)); 444 kex->newkeys[mode] = newkeys; 445 ctos = (!kex->server && mode == MODE_OUT) || 446 (kex->server && mode == MODE_IN); 447 nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC; 448 nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC; 449 ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC; 450 choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]); 451 choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]); 452 choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]); 453 debug("REQUESTED ENC.NAME is '%s'", newkeys->enc.name); 454 if (strcmp(newkeys->enc.name, "none") == 0) { 455 debug("Requesting NONE. Authflag is %d", auth_flag); 456 if (auth_flag == 1) { 457 debug("None requested post authentication."); 458 } else { 459 fatal("Pre-authentication none cipher requests are not allowed."); 460 } 461 } 462 debug("kex: %s %s %s %s", 463 ctos ? "client->server" : "server->client", 464 newkeys->enc.name, 465 newkeys->mac.name, 466 newkeys->comp.name); 467 /* client starts withctos = 0 && log flag = 0 and no log*/ 468 /* 2nd client pass ctos=1 and flag = 1 so no log*/ 469 /* server starts with ctos =1 && log_flag = 0 so log */ 470 /* 2nd sever pass ctos = 1 && log flag = 1 so no log*/ 471 /* -cjr*/ 472 if (ctos && !log_flag) { 473 logit("SSH: Server;Ltype: Kex;Remote: %s-%d;Enc: %s;MAC: %s;Comp: %s", 474 get_remote_ipaddr(), 475 get_remote_port(), 476 newkeys->enc.name, 477 newkeys->mac.name, 478 newkeys->comp.name); 479 } 480 log_flag = 1; 481 } 482 choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]); 483 choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], 484 sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]); 485 need = 0; 486 for (mode = 0; mode < MODE_MAX; mode++) { 487 newkeys = kex->newkeys[mode]; 488 if (need < newkeys->enc.key_len) 489 need = newkeys->enc.key_len; 490 if (need < newkeys->enc.block_size) 491 need = newkeys->enc.block_size; 492 if (need < newkeys->mac.key_len) 493 need = newkeys->mac.key_len; 494 } 495 /* XXX need runden? */ 496 kex->we_need = need; 497 498 /* ignore the next message if the proposals do not match */ 499 if (first_kex_follows && !proposals_match(my, peer) && 500 !(datafellows & SSH_BUG_FIRSTKEX)) { 501 type = packet_read(); 502 debug2("skipping next packet (type %u)", type); 503 } 504 505 kex_prop_free(my); 506 kex_prop_free(peer); 507 } 508 509 static u_char * 510 derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen, 511 BIGNUM *shared_secret) 512 { 513 Buffer b; 514 EVP_MD_CTX md; 515 char c = id; 516 u_int have; 517 int mdsz; 518 u_char *digest; 519 520 if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0) 521 fatal("bad kex md size %d", mdsz); 522 digest = xmalloc(roundup(need, mdsz)); 523 524 buffer_init(&b); 525 buffer_put_bignum2(&b, shared_secret); 526 527 /* K1 = HASH(K || H || "A" || session_id) */ 528 EVP_DigestInit(&md, kex->evp_md); 529 if (!(datafellows & SSH_BUG_DERIVEKEY)) 530 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); 531 EVP_DigestUpdate(&md, hash, hashlen); 532 EVP_DigestUpdate(&md, &c, 1); 533 EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len); 534 EVP_DigestFinal(&md, digest, NULL); 535 536 /* 537 * expand key: 538 * Kn = HASH(K || H || K1 || K2 || ... || Kn-1) 539 * Key = K1 || K2 || ... || Kn 540 */ 541 for (have = mdsz; need > have; have += mdsz) { 542 EVP_DigestInit(&md, kex->evp_md); 543 if (!(datafellows & SSH_BUG_DERIVEKEY)) 544 EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); 545 EVP_DigestUpdate(&md, hash, hashlen); 546 EVP_DigestUpdate(&md, digest, have); 547 EVP_DigestFinal(&md, digest + have, NULL); 548 } 549 buffer_free(&b); 550 #ifdef DEBUG_KEX 551 fprintf(stderr, "key '%c'== ", c); 552 dump_digest("key", digest, need); 553 #endif 554 return digest; 555 } 556 557 Newkeys *current_keys[MODE_MAX]; 558 559 #define NKEYS 6 560 void 561 kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret) 562 { 563 u_char *keys[NKEYS]; 564 u_int i, mode, ctos; 565 566 for (i = 0; i < NKEYS; i++) { 567 keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen, 568 shared_secret); 569 } 570 571 debug2("kex_derive_keys"); 572 for (mode = 0; mode < MODE_MAX; mode++) { 573 current_keys[mode] = kex->newkeys[mode]; 574 kex->newkeys[mode] = NULL; 575 ctos = (!kex->server && mode == MODE_OUT) || 576 (kex->server && mode == MODE_IN); 577 current_keys[mode]->enc.iv = keys[ctos ? 0 : 1]; 578 current_keys[mode]->enc.key = keys[ctos ? 2 : 3]; 579 current_keys[mode]->mac.key = keys[ctos ? 4 : 5]; 580 } 581 } 582 583 Newkeys * 584 kex_get_newkeys(int mode) 585 { 586 Newkeys *ret; 587 588 ret = current_keys[mode]; 589 current_keys[mode] = NULL; 590 return ret; 591 } 592 593 void 594 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus, 595 u_int8_t cookie[8], u_int8_t id[16]) 596 { 597 const EVP_MD *evp_md = EVP_md5(); 598 EVP_MD_CTX md; 599 u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE]; 600 int len; 601 602 EVP_DigestInit(&md, evp_md); 603 604 len = BN_num_bytes(host_modulus); 605 if (len < (512 / 8) || (u_int)len > sizeof(nbuf)) 606 fatal("%s: bad host modulus (len %d)", __func__, len); 607 BN_bn2bin(host_modulus, nbuf); 608 EVP_DigestUpdate(&md, nbuf, len); 609 610 len = BN_num_bytes(server_modulus); 611 if (len < (512 / 8) || (u_int)len > sizeof(nbuf)) 612 fatal("%s: bad server modulus (len %d)", __func__, len); 613 BN_bn2bin(server_modulus, nbuf); 614 EVP_DigestUpdate(&md, nbuf, len); 615 616 EVP_DigestUpdate(&md, cookie, 8); 617 618 EVP_DigestFinal(&md, obuf, NULL); 619 memcpy(id, obuf, 16); 620 621 memset(nbuf, 0, sizeof(nbuf)); 622 memset(obuf, 0, sizeof(obuf)); 623 memset(&md, 0, sizeof(md)); 624 } 625 626 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH) 627 void 628 dump_digest(char *msg, u_char *digest, int len) 629 { 630 int i; 631 632 fprintf(stderr, "%s\n", msg); 633 for (i = 0; i < len; i++) { 634 fprintf(stderr, "%02x", digest[i]); 635 if (i%32 == 31) 636 fprintf(stderr, "\n"); 637 else if (i%8 == 7) 638 fprintf(stderr, " "); 639 } 640 fprintf(stderr, "\n"); 641 } 642 #endif 643