1 /* $OpenBSD: options.c,v 1.15 2004/12/26 03:17:07 deraadt Exp $ */ 2 3 /* DHCP options parsing and reassembly. */ 4 5 /* 6 * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium. 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of The Internet Software Consortium nor the names 19 * of its contributors may be used to endorse or promote products derived 20 * from this software without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND 23 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, 24 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 25 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 26 * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR 27 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 29 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 30 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 31 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 32 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 33 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * This software has been written for the Internet Software Consortium 37 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie 38 * Enterprises. To learn more about the Internet Software Consortium, 39 * see ``http://www.vix.com/isc''. To learn more about Vixie 40 * Enterprises, see ``http://www.vix.com''. 41 */ 42 43 #include <sys/cdefs.h> 44 __FBSDID("$FreeBSD$"); 45 46 #include <ctype.h> 47 48 #define DHCP_OPTION_DATA 49 #include "dhcpd.h" 50 51 int bad_options = 0; 52 int bad_options_max = 5; 53 54 void parse_options(struct packet *); 55 void parse_option_buffer(struct packet *, unsigned char *, int); 56 int store_options(unsigned char *, int, struct tree_cache **, 57 unsigned char *, int, int, int, int); 58 59 60 /* 61 * Parse all available options out of the specified packet. 62 */ 63 void 64 parse_options(struct packet *packet) 65 { 66 /* Initially, zero all option pointers. */ 67 memset(packet->options, 0, sizeof(packet->options)); 68 69 /* If we don't see the magic cookie, there's nothing to parse. */ 70 if (memcmp(packet->raw->options, DHCP_OPTIONS_COOKIE, 4)) { 71 packet->options_valid = 0; 72 return; 73 } 74 75 /* 76 * Go through the options field, up to the end of the packet or 77 * the End field. 78 */ 79 parse_option_buffer(packet, &packet->raw->options[4], 80 packet->packet_length - DHCP_FIXED_NON_UDP - 4); 81 82 /* 83 * If we parsed a DHCP Option Overload option, parse more 84 * options out of the buffer(s) containing them. 85 */ 86 if (packet->options_valid && 87 packet->options[DHO_DHCP_OPTION_OVERLOAD].data) { 88 if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 1) 89 parse_option_buffer(packet, 90 (unsigned char *)packet->raw->file, 91 sizeof(packet->raw->file)); 92 if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 2) 93 parse_option_buffer(packet, 94 (unsigned char *)packet->raw->sname, 95 sizeof(packet->raw->sname)); 96 } 97 } 98 99 /* 100 * Parse options out of the specified buffer, storing addresses of 101 * option values in packet->options and setting packet->options_valid if 102 * no errors are encountered. 103 */ 104 void 105 parse_option_buffer(struct packet *packet, 106 unsigned char *buffer, int length) 107 { 108 unsigned char *s, *t, *end = buffer + length; 109 int len, code; 110 111 for (s = buffer; *s != DHO_END && s < end; ) { 112 code = s[0]; 113 114 /* Pad options don't have a length - just skip them. */ 115 if (code == DHO_PAD) { 116 s++; 117 continue; 118 } 119 if (s + 2 > end) { 120 len = 65536; 121 goto bogus; 122 } 123 124 /* 125 * All other fields (except end, see above) have a 126 * one-byte length. 127 */ 128 len = s[1]; 129 130 /* 131 * If the length is outrageous, silently skip the rest, 132 * and mark the packet bad. Unfortunately some crappy 133 * dhcp servers always seem to give us garbage on the 134 * end of a packet. so rather than keep refusing, give 135 * up and try to take one after seeing a few without 136 * anything good. 137 */ 138 if (s + len + 2 > end) { 139 bogus: 140 bad_options++; 141 warning("option %s (%d) %s.", 142 dhcp_options[code].name, len, 143 "larger than buffer"); 144 if (bad_options == bad_options_max) { 145 packet->options_valid = 1; 146 bad_options = 0; 147 warning("Many bogus options seen in offers. " 148 "Taking this offer in spite of bogus " 149 "options - hope for the best!"); 150 } else { 151 warning("rejecting bogus offer."); 152 packet->options_valid = 0; 153 } 154 return; 155 } 156 /* 157 * If we haven't seen this option before, just make 158 * space for it and copy it there. 159 */ 160 if (!packet->options[code].data) { 161 if (!(t = calloc(1, len + 1))) 162 error("Can't allocate storage for option %s.", 163 dhcp_options[code].name); 164 /* 165 * Copy and NUL-terminate the option (in case 166 * it's an ASCII string. 167 */ 168 memcpy(t, &s[2], len); 169 t[len] = 0; 170 packet->options[code].len = len; 171 packet->options[code].data = t; 172 } else { 173 /* 174 * If it's a repeat, concatenate it to whatever 175 * we last saw. This is really only required 176 * for clients, but what the heck... 177 */ 178 t = calloc(1, len + packet->options[code].len + 1); 179 if (!t) 180 error("Can't expand storage for option %s.", 181 dhcp_options[code].name); 182 memcpy(t, packet->options[code].data, 183 packet->options[code].len); 184 memcpy(t + packet->options[code].len, 185 &s[2], len); 186 packet->options[code].len += len; 187 t[packet->options[code].len] = 0; 188 free(packet->options[code].data); 189 packet->options[code].data = t; 190 } 191 s += len + 2; 192 } 193 packet->options_valid = 1; 194 } 195 196 /* 197 * cons options into a big buffer, and then split them out into the 198 * three separate buffers if needed. This allows us to cons up a set of 199 * vendor options using the same routine. 200 */ 201 int 202 cons_options(struct packet *inpacket, struct dhcp_packet *outpacket, 203 int mms, struct tree_cache **options, 204 int overload, /* Overload flags that may be set. */ 205 int terminate, int bootpp, u_int8_t *prl, int prl_len) 206 { 207 unsigned char priority_list[300], buffer[4096]; 208 int priority_len, main_buffer_size, mainbufix, bufix; 209 int option_size, length; 210 211 /* 212 * If the client has provided a maximum DHCP message size, use 213 * that; otherwise, if it's BOOTP, only 64 bytes; otherwise use 214 * up to the minimum IP MTU size (576 bytes). 215 * 216 * XXX if a BOOTP client specifies a max message size, we will 217 * honor it. 218 */ 219 if (!mms && 220 inpacket && 221 inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data && 222 (inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].len >= 223 sizeof(u_int16_t))) 224 mms = getUShort( 225 inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data); 226 227 if (mms) 228 main_buffer_size = mms - DHCP_FIXED_LEN; 229 else if (bootpp) 230 main_buffer_size = 64; 231 else 232 main_buffer_size = 576 - DHCP_FIXED_LEN; 233 234 if (main_buffer_size > sizeof(buffer)) 235 main_buffer_size = sizeof(buffer); 236 237 /* Preload the option priority list with mandatory options. */ 238 priority_len = 0; 239 priority_list[priority_len++] = DHO_DHCP_MESSAGE_TYPE; 240 priority_list[priority_len++] = DHO_DHCP_SERVER_IDENTIFIER; 241 priority_list[priority_len++] = DHO_DHCP_LEASE_TIME; 242 priority_list[priority_len++] = DHO_DHCP_MESSAGE; 243 244 /* 245 * If the client has provided a list of options that it wishes 246 * returned, use it to prioritize. Otherwise, prioritize based 247 * on the default priority list. 248 */ 249 if (inpacket && 250 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data) { 251 int prlen = 252 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].len; 253 if (prlen + priority_len > sizeof(priority_list)) 254 prlen = sizeof(priority_list) - priority_len; 255 256 memcpy(&priority_list[priority_len], 257 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data, 258 prlen); 259 priority_len += prlen; 260 prl = priority_list; 261 } else if (prl) { 262 if (prl_len + priority_len > sizeof(priority_list)) 263 prl_len = sizeof(priority_list) - priority_len; 264 265 memcpy(&priority_list[priority_len], prl, prl_len); 266 priority_len += prl_len; 267 prl = priority_list; 268 } else { 269 memcpy(&priority_list[priority_len], 270 dhcp_option_default_priority_list, 271 sizeof_dhcp_option_default_priority_list); 272 priority_len += sizeof_dhcp_option_default_priority_list; 273 } 274 275 /* Copy the options into the big buffer... */ 276 option_size = store_options( 277 buffer, 278 (main_buffer_size - 7 + ((overload & 1) ? DHCP_FILE_LEN : 0) + 279 ((overload & 2) ? DHCP_SNAME_LEN : 0)), 280 options, priority_list, priority_len, main_buffer_size, 281 (main_buffer_size + ((overload & 1) ? DHCP_FILE_LEN : 0)), 282 terminate); 283 284 /* Put the cookie up front... */ 285 memcpy(outpacket->options, DHCP_OPTIONS_COOKIE, 4); 286 mainbufix = 4; 287 288 /* 289 * If we're going to have to overload, store the overload option 290 * at the beginning. If we can, though, just store the whole 291 * thing in the packet's option buffer and leave it at that. 292 */ 293 if (option_size <= main_buffer_size - mainbufix) { 294 memcpy(&outpacket->options[mainbufix], 295 buffer, option_size); 296 mainbufix += option_size; 297 if (mainbufix < main_buffer_size) 298 outpacket->options[mainbufix++] = DHO_END; 299 length = DHCP_FIXED_NON_UDP + mainbufix; 300 } else { 301 outpacket->options[mainbufix++] = DHO_DHCP_OPTION_OVERLOAD; 302 outpacket->options[mainbufix++] = 1; 303 if (option_size > 304 main_buffer_size - mainbufix + DHCP_FILE_LEN) 305 outpacket->options[mainbufix++] = 3; 306 else 307 outpacket->options[mainbufix++] = 1; 308 309 memcpy(&outpacket->options[mainbufix], 310 buffer, main_buffer_size - mainbufix); 311 bufix = main_buffer_size - mainbufix; 312 length = DHCP_FIXED_NON_UDP + mainbufix; 313 if (overload & 1) { 314 if (option_size - bufix <= DHCP_FILE_LEN) { 315 memcpy(outpacket->file, 316 &buffer[bufix], option_size - bufix); 317 mainbufix = option_size - bufix; 318 if (mainbufix < DHCP_FILE_LEN) 319 outpacket->file[mainbufix++] = (char)DHO_END; 320 while (mainbufix < DHCP_FILE_LEN) 321 outpacket->file[mainbufix++] = (char)DHO_PAD; 322 } else { 323 memcpy(outpacket->file, 324 &buffer[bufix], DHCP_FILE_LEN); 325 bufix += DHCP_FILE_LEN; 326 } 327 } 328 if ((overload & 2) && option_size < bufix) { 329 memcpy(outpacket->sname, 330 &buffer[bufix], option_size - bufix); 331 332 mainbufix = option_size - bufix; 333 if (mainbufix < DHCP_SNAME_LEN) 334 outpacket->file[mainbufix++] = (char)DHO_END; 335 while (mainbufix < DHCP_SNAME_LEN) 336 outpacket->file[mainbufix++] = (char)DHO_PAD; 337 } 338 } 339 return (length); 340 } 341 342 /* 343 * Store all the requested options into the requested buffer. 344 */ 345 int 346 store_options(unsigned char *buffer, int buflen, struct tree_cache **options, 347 unsigned char *priority_list, int priority_len, int first_cutoff, 348 int second_cutoff, int terminate) 349 { 350 int bufix = 0, option_stored[256], i, ix, tto; 351 352 /* Zero out the stored-lengths array. */ 353 memset(option_stored, 0, sizeof(option_stored)); 354 355 /* 356 * Copy out the options in the order that they appear in the 357 * priority list... 358 */ 359 for (i = 0; i < priority_len; i++) { 360 /* Code for next option to try to store. */ 361 int code = priority_list[i]; 362 int optstart; 363 364 /* 365 * Number of bytes left to store (some may already have 366 * been stored by a previous pass). 367 */ 368 int length; 369 370 /* If no data is available for this option, skip it. */ 371 if (!options[code]) { 372 continue; 373 } 374 375 /* 376 * The client could ask for things that are mandatory, 377 * in which case we should avoid storing them twice... 378 */ 379 if (option_stored[code]) 380 continue; 381 option_stored[code] = 1; 382 383 /* We should now have a constant length for the option. */ 384 length = options[code]->len; 385 386 /* Do we add a NUL? */ 387 if (terminate && dhcp_options[code].format[0] == 't') { 388 length++; 389 tto = 1; 390 } else 391 tto = 0; 392 393 /* Try to store the option. */ 394 395 /* 396 * If the option's length is more than 255, we must 397 * store it in multiple hunks. Store 255-byte hunks 398 * first. However, in any case, if the option data will 399 * cross a buffer boundary, split it across that 400 * boundary. 401 */ 402 ix = 0; 403 404 optstart = bufix; 405 while (length) { 406 unsigned char incr = length > 255 ? 255 : length; 407 408 /* 409 * If this hunk of the buffer will cross a 410 * boundary, only go up to the boundary in this 411 * pass. 412 */ 413 if (bufix < first_cutoff && 414 bufix + incr > first_cutoff) 415 incr = first_cutoff - bufix; 416 else if (bufix < second_cutoff && 417 bufix + incr > second_cutoff) 418 incr = second_cutoff - bufix; 419 420 /* 421 * If this option is going to overflow the 422 * buffer, skip it. 423 */ 424 if (bufix + 2 + incr > buflen) { 425 bufix = optstart; 426 break; 427 } 428 429 /* Everything looks good - copy it in! */ 430 buffer[bufix] = code; 431 buffer[bufix + 1] = incr; 432 if (tto && incr == length) { 433 memcpy(buffer + bufix + 2, 434 options[code]->value + ix, incr - 1); 435 buffer[bufix + 2 + incr - 1] = 0; 436 } else 437 memcpy(buffer + bufix + 2, 438 options[code]->value + ix, incr); 439 length -= incr; 440 ix += incr; 441 bufix += 2 + incr; 442 } 443 } 444 return (bufix); 445 } 446 447 /* 448 * Format the specified option so that a human can easily read it. 449 */ 450 char * 451 pretty_print_option(unsigned int code, unsigned char *data, int len, 452 int emit_commas, int emit_quotes) 453 { 454 static char optbuf[32768]; /* XXX */ 455 int hunksize = 0, numhunk = -1, numelem = 0; 456 char fmtbuf[32], *op = optbuf; 457 int i, j, k, opleft = sizeof(optbuf); 458 unsigned char *dp = data; 459 struct in_addr foo; 460 char comma; 461 462 /* Code should be between 0 and 255. */ 463 if (code > 255) 464 error("pretty_print_option: bad code %d", code); 465 466 if (emit_commas) 467 comma = ','; 468 else 469 comma = ' '; 470 471 /* Figure out the size of the data. */ 472 for (i = 0; dhcp_options[code].format[i]; i++) { 473 if (!numhunk) { 474 warning("%s: Excess information in format string: %s", 475 dhcp_options[code].name, 476 &(dhcp_options[code].format[i])); 477 break; 478 } 479 numelem++; 480 fmtbuf[i] = dhcp_options[code].format[i]; 481 switch (dhcp_options[code].format[i]) { 482 case 'A': 483 --numelem; 484 fmtbuf[i] = 0; 485 numhunk = 0; 486 break; 487 case 'X': 488 for (k = 0; k < len; k++) 489 if (!isascii(data[k]) || 490 !isprint(data[k])) 491 break; 492 if (k == len) { 493 fmtbuf[i] = 't'; 494 numhunk = -2; 495 } else { 496 fmtbuf[i] = 'x'; 497 hunksize++; 498 comma = ':'; 499 numhunk = 0; 500 } 501 fmtbuf[i + 1] = 0; 502 break; 503 case 't': 504 fmtbuf[i] = 't'; 505 fmtbuf[i + 1] = 0; 506 numhunk = -2; 507 break; 508 case 'I': 509 case 'l': 510 case 'L': 511 hunksize += 4; 512 break; 513 case 's': 514 case 'S': 515 hunksize += 2; 516 break; 517 case 'b': 518 case 'B': 519 case 'f': 520 hunksize++; 521 break; 522 case 'e': 523 break; 524 default: 525 warning("%s: garbage in format string: %s", 526 dhcp_options[code].name, 527 &(dhcp_options[code].format[i])); 528 break; 529 } 530 } 531 532 /* Check for too few bytes... */ 533 if (hunksize > len) { 534 warning("%s: expecting at least %d bytes; got %d", 535 dhcp_options[code].name, hunksize, len); 536 return ("<error>"); 537 } 538 /* Check for too many bytes... */ 539 if (numhunk == -1 && hunksize < len) 540 warning("%s: %d extra bytes", 541 dhcp_options[code].name, len - hunksize); 542 543 /* If this is an array, compute its size. */ 544 if (!numhunk) 545 numhunk = len / hunksize; 546 /* See if we got an exact number of hunks. */ 547 if (numhunk > 0 && numhunk * hunksize < len) 548 warning("%s: %d extra bytes at end of array", 549 dhcp_options[code].name, len - numhunk * hunksize); 550 551 /* A one-hunk array prints the same as a single hunk. */ 552 if (numhunk < 0) 553 numhunk = 1; 554 555 /* Cycle through the array (or hunk) printing the data. */ 556 for (i = 0; i < numhunk; i++) { 557 for (j = 0; j < numelem; j++) { 558 int opcount; 559 switch (fmtbuf[j]) { 560 case 't': 561 if (emit_quotes) { 562 *op++ = '"'; 563 opleft--; 564 } 565 for (; dp < data + len; dp++) { 566 if (!isascii(*dp) || 567 !isprint(*dp)) { 568 if (dp + 1 != data + len || 569 *dp != 0) { 570 snprintf(op, opleft, 571 "\\%03o", *dp); 572 op += 4; 573 opleft -= 4; 574 } 575 } else if (*dp == '"' || 576 *dp == '\'' || 577 *dp == '$' || 578 *dp == '`' || 579 *dp == '\\') { 580 *op++ = '\\'; 581 *op++ = *dp; 582 opleft -= 2; 583 } else { 584 *op++ = *dp; 585 opleft--; 586 } 587 } 588 if (emit_quotes) { 589 *op++ = '"'; 590 opleft--; 591 } 592 593 *op = 0; 594 break; 595 case 'I': 596 foo.s_addr = htonl(getULong(dp)); 597 opcount = strlcpy(op, inet_ntoa(foo), opleft); 598 if (opcount >= opleft) 599 goto toobig; 600 opleft -= opcount; 601 dp += 4; 602 break; 603 case 'l': 604 opcount = snprintf(op, opleft, "%ld", 605 (long)getLong(dp)); 606 if (opcount >= opleft || opcount == -1) 607 goto toobig; 608 opleft -= opcount; 609 dp += 4; 610 break; 611 case 'L': 612 opcount = snprintf(op, opleft, "%ld", 613 (unsigned long)getULong(dp)); 614 if (opcount >= opleft || opcount == -1) 615 goto toobig; 616 opleft -= opcount; 617 dp += 4; 618 break; 619 case 's': 620 opcount = snprintf(op, opleft, "%d", 621 getShort(dp)); 622 if (opcount >= opleft || opcount == -1) 623 goto toobig; 624 opleft -= opcount; 625 dp += 2; 626 break; 627 case 'S': 628 opcount = snprintf(op, opleft, "%d", 629 getUShort(dp)); 630 if (opcount >= opleft || opcount == -1) 631 goto toobig; 632 opleft -= opcount; 633 dp += 2; 634 break; 635 case 'b': 636 opcount = snprintf(op, opleft, "%d", 637 *(char *)dp++); 638 if (opcount >= opleft || opcount == -1) 639 goto toobig; 640 opleft -= opcount; 641 break; 642 case 'B': 643 opcount = snprintf(op, opleft, "%d", *dp++); 644 if (opcount >= opleft || opcount == -1) 645 goto toobig; 646 opleft -= opcount; 647 break; 648 case 'x': 649 opcount = snprintf(op, opleft, "%x", *dp++); 650 if (opcount >= opleft || opcount == -1) 651 goto toobig; 652 opleft -= opcount; 653 break; 654 case 'f': 655 opcount = strlcpy(op, 656 *dp++ ? "true" : "false", opleft); 657 if (opcount >= opleft) 658 goto toobig; 659 opleft -= opcount; 660 break; 661 default: 662 warning("Unexpected format code %c", fmtbuf[j]); 663 } 664 op += strlen(op); 665 opleft -= strlen(op); 666 if (opleft < 1) 667 goto toobig; 668 if (j + 1 < numelem && comma != ':') { 669 *op++ = ' '; 670 opleft--; 671 } 672 } 673 if (i + 1 < numhunk) { 674 *op++ = comma; 675 opleft--; 676 } 677 if (opleft < 1) 678 goto toobig; 679 680 } 681 return (optbuf); 682 toobig: 683 warning("dhcp option too large"); 684 return ("<error>"); 685 } 686 687 void 688 do_packet(struct interface_info *interface, struct dhcp_packet *packet, 689 int len, unsigned int from_port, struct iaddr from, struct hardware *hfrom) 690 { 691 struct packet tp; 692 int i; 693 694 if (packet->hlen > sizeof(packet->chaddr)) { 695 note("Discarding packet with invalid hlen."); 696 return; 697 } 698 699 memset(&tp, 0, sizeof(tp)); 700 tp.raw = packet; 701 tp.packet_length = len; 702 tp.client_port = from_port; 703 tp.client_addr = from; 704 tp.interface = interface; 705 tp.haddr = hfrom; 706 707 parse_options(&tp); 708 if (tp.options_valid && 709 tp.options[DHO_DHCP_MESSAGE_TYPE].data) 710 tp.packet_type = tp.options[DHO_DHCP_MESSAGE_TYPE].data[0]; 711 if (tp.packet_type) 712 dhcp(&tp); 713 else 714 bootp(&tp); 715 716 /* Free the data associated with the options. */ 717 for (i = 0; i < 256; i++) 718 if (tp.options[i].len && tp.options[i].data) 719 free(tp.options[i].data); 720 } 721