1 /* $OpenBSD: options.c,v 1.15 2004/12/26 03:17:07 deraadt Exp $ */
3 /* DHCP options parsing and reassembly. */
6 * SPDX-License-Identifier: BSD-3-Clause
8 * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of The Internet Software Consortium nor the names
21 * of its contributors may be used to endorse or promote products derived
22 * from this software without specific prior written permission.
24 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
25 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
26 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
27 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
28 * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
29 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
32 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
33 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
34 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
35 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * This software has been written for the Internet Software Consortium
39 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
40 * Enterprises. To learn more about the Internet Software Consortium,
41 * see ``http://www.vix.com/isc''. To learn more about Vixie
42 * Enterprises, see ``http://www.vix.com''.
45 #include <sys/cdefs.h>
46 __FBSDID("$FreeBSD$");
50 #define DHCP_OPTION_DATA
53 static int bad_options = 0;
54 static int bad_options_max = 5;
56 void parse_options(struct packet *);
57 void parse_option_buffer(struct packet *, unsigned char *, int);
58 unsigned store_options(unsigned char *, int, struct tree_cache **,
59 unsigned char *, int, int, int, int);
60 void expand_domain_search(struct packet *packet);
61 int find_search_domain_name_len(struct option_data *option, size_t *offset);
62 void expand_search_domain_name(struct option_data *option, size_t *offset,
63 unsigned char **domain_search);
67 * Parse all available options out of the specified packet.
70 parse_options(struct packet *packet)
72 /* Initially, zero all option pointers. */
73 memset(packet->options, 0, sizeof(packet->options));
75 /* If we don't see the magic cookie, there's nothing to parse. */
76 if (memcmp(packet->raw->options, DHCP_OPTIONS_COOKIE, 4)) {
77 packet->options_valid = 0;
82 * Go through the options field, up to the end of the packet or
85 parse_option_buffer(packet, &packet->raw->options[4],
86 packet->packet_length - DHCP_FIXED_NON_UDP - 4);
89 * If we parsed a DHCP Option Overload option, parse more
90 * options out of the buffer(s) containing them.
92 if (packet->options_valid &&
93 packet->options[DHO_DHCP_OPTION_OVERLOAD].data) {
94 if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 1)
95 parse_option_buffer(packet,
96 (unsigned char *)packet->raw->file,
97 sizeof(packet->raw->file));
98 if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 2)
99 parse_option_buffer(packet,
100 (unsigned char *)packet->raw->sname,
101 sizeof(packet->raw->sname));
104 /* Expand DHCP Domain Search option. */
105 if (packet->options_valid) {
106 expand_domain_search(packet);
111 * Parse options out of the specified buffer, storing addresses of
112 * option values in packet->options and setting packet->options_valid if
113 * no errors are encountered.
116 parse_option_buffer(struct packet *packet,
117 unsigned char *buffer, int length)
119 unsigned char *s, *t, *end = buffer + length;
122 for (s = buffer; *s != DHO_END && s < end; ) {
125 /* Pad options don't have a length - just skip them. */
126 if (code == DHO_PAD) {
136 * All other fields (except end, see above) have a
142 * If the length is outrageous, silently skip the rest,
143 * and mark the packet bad. Unfortunately some crappy
144 * dhcp servers always seem to give us garbage on the
145 * end of a packet. so rather than keep refusing, give
146 * up and try to take one after seeing a few without
149 if (s + len + 2 > end) {
152 warning("option %s (%d) %s.",
153 dhcp_options[code].name, len,
154 "larger than buffer");
155 if (bad_options == bad_options_max) {
156 packet->options_valid = 1;
158 warning("Many bogus options seen in offers. "
159 "Taking this offer in spite of bogus "
160 "options - hope for the best!");
162 warning("rejecting bogus offer.");
163 packet->options_valid = 0;
168 * If we haven't seen this option before, just make
169 * space for it and copy it there.
171 if (!packet->options[code].data) {
172 if (!(t = calloc(1, len + 1)))
173 error("Can't allocate storage for option %s.",
174 dhcp_options[code].name);
176 * Copy and NUL-terminate the option (in case
177 * it's an ASCII string.
179 memcpy(t, &s[2], len);
181 packet->options[code].len = len;
182 packet->options[code].data = t;
185 * If it's a repeat, concatenate it to whatever
186 * we last saw. This is really only required
187 * for clients, but what the heck...
189 t = calloc(1, len + packet->options[code].len + 1);
191 error("Can't expand storage for option %s.",
192 dhcp_options[code].name);
193 memcpy(t, packet->options[code].data,
194 packet->options[code].len);
195 memcpy(t + packet->options[code].len,
197 packet->options[code].len += len;
198 t[packet->options[code].len] = 0;
199 free(packet->options[code].data);
200 packet->options[code].data = t;
204 packet->options_valid = 1;
208 * Expand DHCP Domain Search option. The value of this option is
209 * encoded like DNS' list of labels. See:
214 expand_domain_search(struct packet *packet)
217 int expanded_len, next_domain_len;
218 struct option_data *option;
219 unsigned char *domain_search, *cursor;
221 if (packet->options[DHO_DOMAIN_SEARCH].data == NULL)
224 option = &packet->options[DHO_DOMAIN_SEARCH];
226 /* Compute final expanded length. */
229 while (offset < option->len) {
230 next_domain_len = find_search_domain_name_len(option, &offset);
231 if (next_domain_len < 0)
232 /* The Domain Search option value is invalid. */
235 /* We add 1 for the space between domain names. */
236 expanded_len += next_domain_len + 1;
238 if (expanded_len > 0)
239 /* Remove 1 for the superfluous trailing space. */
242 domain_search = malloc(expanded_len + 1);
243 if (domain_search == NULL)
244 error("Can't allocate storage for expanded domain-search\n");
247 cursor = domain_search;
248 while (offset < option->len) {
249 expand_search_domain_name(option, &offset, &cursor);
253 domain_search[expanded_len] = '\0';
256 option->len = expanded_len;
257 option->data = domain_search;
261 find_search_domain_name_len(struct option_data *option, size_t *offset)
263 int domain_name_len, label_len, pointed_len;
269 while (i < option->len) {
270 label_len = option->data[i];
271 if (label_len == 0) {
273 * A zero-length label marks the end of this
277 return (domain_name_len);
278 } else if (label_len & 0xC0) {
279 /* This is a pointer to another list of labels. */
280 if (i + 1 >= option->len) {
281 /* The pointer is truncated. */
282 warning("Truncated pointer in DHCP Domain "
287 pointer = ((label_len & ~(0xC0)) << 8) +
289 if (pointer >= *offset) {
291 * The pointer must indicate a prior
294 warning("Invalid forward pointer in DHCP "
295 "Domain Search option compression.");
299 pointed_len = find_search_domain_name_len(option,
301 domain_name_len += pointed_len;
304 return (domain_name_len);
307 if (i + label_len >= option->len) {
308 warning("Truncated label in DHCP Domain Search "
314 * Update the domain name length with the length of the
315 * current label, plus a trailing dot ('.').
317 domain_name_len += label_len + 1;
323 warning("Truncated DHCP Domain Search option.");
329 expand_search_domain_name(struct option_data *option, size_t *offset,
330 unsigned char **domain_search)
334 unsigned char *cursor;
337 * This is the same loop than the function above
338 * (find_search_domain_name_len). Therefore, we remove checks,
339 * they're already done. Here, we just make the copy.
342 cursor = *domain_search;
343 while (i < option->len) {
344 label_len = option->data[i];
345 if (label_len == 0) {
347 * A zero-length label marks the end of this
351 *domain_search = cursor;
353 } else if (label_len & 0xC0) {
354 /* This is a pointer to another list of labels. */
355 pointer = ((label_len & ~(0xC0)) << 8) +
358 expand_search_domain_name(option, &pointer, &cursor);
361 *domain_search = cursor;
365 /* Copy the label found. */
366 memcpy(cursor, option->data + i + 1, label_len);
367 cursor[label_len] = '.';
371 cursor += label_len + 1;
376 * cons options into a big buffer, and then split them out into the
377 * three separate buffers if needed. This allows us to cons up a set of
378 * vendor options using the same routine.
381 cons_options(struct packet *inpacket, struct dhcp_packet *outpacket,
382 int mms, struct tree_cache **options,
383 int overload, /* Overload flags that may be set. */
384 int terminate, int bootpp, u_int8_t *prl, int prl_len)
386 unsigned char priority_list[300], buffer[4096];
387 unsigned priority_len;
388 size_t main_buffer_size;
389 unsigned option_size, bufix, mainbufix;
393 * If the client has provided a maximum DHCP message size, use
394 * that; otherwise, if it's BOOTP, only 64 bytes; otherwise use
395 * up to the minimum IP MTU size (576 bytes).
397 * XXX if a BOOTP client specifies a max message size, we will
402 inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data &&
403 (inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].len >=
406 inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data);
409 main_buffer_size = mms - DHCP_FIXED_LEN;
411 main_buffer_size = 64;
413 main_buffer_size = 576 - DHCP_FIXED_LEN;
415 if (main_buffer_size > sizeof(buffer))
416 main_buffer_size = sizeof(buffer);
418 /* Preload the option priority list with mandatory options. */
420 priority_list[priority_len++] = DHO_DHCP_MESSAGE_TYPE;
421 priority_list[priority_len++] = DHO_DHCP_SERVER_IDENTIFIER;
422 priority_list[priority_len++] = DHO_DHCP_LEASE_TIME;
423 priority_list[priority_len++] = DHO_DHCP_MESSAGE;
426 * If the client has provided a list of options that it wishes
427 * returned, use it to prioritize. Otherwise, prioritize based
428 * on the default priority list.
431 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data) {
433 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].len;
434 if (prlen + priority_len > sizeof(priority_list))
435 prlen = sizeof(priority_list) - priority_len;
437 memcpy(&priority_list[priority_len],
438 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data,
440 priority_len += prlen;
443 if (prl_len + priority_len > sizeof(priority_list))
444 prl_len = sizeof(priority_list) - priority_len;
446 memcpy(&priority_list[priority_len], prl, prl_len);
447 priority_len += prl_len;
450 memcpy(&priority_list[priority_len],
451 dhcp_option_default_priority_list,
452 sizeof_dhcp_option_default_priority_list);
453 priority_len += sizeof_dhcp_option_default_priority_list;
456 /* Copy the options into the big buffer... */
457 option_size = store_options(
459 (main_buffer_size - 7 + ((overload & 1) ? DHCP_FILE_LEN : 0) +
460 ((overload & 2) ? DHCP_SNAME_LEN : 0)),
461 options, priority_list, priority_len, main_buffer_size,
462 (main_buffer_size + ((overload & 1) ? DHCP_FILE_LEN : 0)),
465 /* Put the cookie up front... */
466 memcpy(outpacket->options, DHCP_OPTIONS_COOKIE, 4);
470 * If we're going to have to overload, store the overload option
471 * at the beginning. If we can, though, just store the whole
472 * thing in the packet's option buffer and leave it at that.
474 if (option_size <= main_buffer_size - mainbufix) {
475 memcpy(&outpacket->options[mainbufix],
476 buffer, option_size);
477 mainbufix += option_size;
478 if (mainbufix < main_buffer_size)
479 outpacket->options[mainbufix++] = DHO_END;
480 length = DHCP_FIXED_NON_UDP + mainbufix;
482 outpacket->options[mainbufix++] = DHO_DHCP_OPTION_OVERLOAD;
483 outpacket->options[mainbufix++] = 1;
485 main_buffer_size - mainbufix + DHCP_FILE_LEN)
486 outpacket->options[mainbufix++] = 3;
488 outpacket->options[mainbufix++] = 1;
490 memcpy(&outpacket->options[mainbufix],
491 buffer, main_buffer_size - mainbufix);
492 bufix = main_buffer_size - mainbufix;
493 length = DHCP_FIXED_NON_UDP + mainbufix;
495 if (option_size - bufix <= DHCP_FILE_LEN) {
496 memcpy(outpacket->file,
497 &buffer[bufix], option_size - bufix);
498 mainbufix = option_size - bufix;
499 if (mainbufix < DHCP_FILE_LEN)
500 outpacket->file[mainbufix++] = (char)DHO_END;
501 while (mainbufix < DHCP_FILE_LEN)
502 outpacket->file[mainbufix++] = (char)DHO_PAD;
504 memcpy(outpacket->file,
505 &buffer[bufix], DHCP_FILE_LEN);
506 bufix += DHCP_FILE_LEN;
509 if ((overload & 2) && option_size < bufix) {
510 memcpy(outpacket->sname,
511 &buffer[bufix], option_size - bufix);
513 mainbufix = option_size - bufix;
514 if (mainbufix < DHCP_SNAME_LEN)
515 outpacket->file[mainbufix++] = (char)DHO_END;
516 while (mainbufix < DHCP_SNAME_LEN)
517 outpacket->file[mainbufix++] = (char)DHO_PAD;
524 * Store all the requested options into the requested buffer.
527 store_options(unsigned char *buffer, int buflen, struct tree_cache **options,
528 unsigned char *priority_list, int priority_len, int first_cutoff,
529 int second_cutoff, int terminate)
531 int bufix = 0, option_stored[256], i, ix, tto;
533 /* Zero out the stored-lengths array. */
534 memset(option_stored, 0, sizeof(option_stored));
537 * Copy out the options in the order that they appear in the
540 for (i = 0; i < priority_len; i++) {
541 /* Code for next option to try to store. */
542 int code = priority_list[i];
546 * Number of bytes left to store (some may already have
547 * been stored by a previous pass).
551 /* If no data is available for this option, skip it. */
552 if (!options[code]) {
557 * The client could ask for things that are mandatory,
558 * in which case we should avoid storing them twice...
560 if (option_stored[code])
562 option_stored[code] = 1;
564 /* We should now have a constant length for the option. */
565 length = options[code]->len;
567 /* Do we add a NUL? */
568 if (terminate && dhcp_options[code].format[0] == 't') {
574 /* Try to store the option. */
577 * If the option's length is more than 255, we must
578 * store it in multiple hunks. Store 255-byte hunks
579 * first. However, in any case, if the option data will
580 * cross a buffer boundary, split it across that
587 unsigned char incr = length > 255 ? 255 : length;
590 * If this hunk of the buffer will cross a
591 * boundary, only go up to the boundary in this
594 if (bufix < first_cutoff &&
595 bufix + incr > first_cutoff)
596 incr = first_cutoff - bufix;
597 else if (bufix < second_cutoff &&
598 bufix + incr > second_cutoff)
599 incr = second_cutoff - bufix;
602 * If this option is going to overflow the
605 if (bufix + 2 + incr > buflen) {
610 /* Everything looks good - copy it in! */
611 buffer[bufix] = code;
612 buffer[bufix + 1] = incr;
613 if (tto && incr == length) {
614 memcpy(buffer + bufix + 2,
615 options[code]->value + ix, incr - 1);
616 buffer[bufix + 2 + incr - 1] = 0;
618 memcpy(buffer + bufix + 2,
619 options[code]->value + ix, incr);
629 * Format the specified option so that a human can easily read it.
632 pretty_print_option(unsigned int code, unsigned char *data, int len,
633 int emit_commas, int emit_quotes)
635 static char optbuf[32768]; /* XXX */
636 int hunksize = 0, numhunk = -1, numelem = 0;
637 char fmtbuf[32], *op = optbuf;
638 int i, j, k, opleft = sizeof(optbuf);
639 unsigned char *dp = data;
643 /* Code should be between 0 and 255. */
645 error("pretty_print_option: bad code %d", code);
652 /* Figure out the size of the data. */
653 for (i = 0; dhcp_options[code].format[i]; i++) {
655 warning("%s: Excess information in format string: %s",
656 dhcp_options[code].name,
657 &(dhcp_options[code].format[i]));
661 fmtbuf[i] = dhcp_options[code].format[i];
662 switch (dhcp_options[code].format[i]) {
669 for (k = 0; k < len; k++)
670 if (!isascii(data[k]) ||
706 warning("%s: garbage in format string: %s",
707 dhcp_options[code].name,
708 &(dhcp_options[code].format[i]));
713 /* Check for too few bytes... */
714 if (hunksize > len) {
715 warning("%s: expecting at least %d bytes; got %d",
716 dhcp_options[code].name, hunksize, len);
719 /* Check for too many bytes... */
720 if (numhunk == -1 && hunksize < len)
721 warning("%s: %d extra bytes",
722 dhcp_options[code].name, len - hunksize);
724 /* If this is an array, compute its size. */
726 numhunk = len / hunksize;
727 /* See if we got an exact number of hunks. */
728 if (numhunk > 0 && numhunk * hunksize < len)
729 warning("%s: %d extra bytes at end of array",
730 dhcp_options[code].name, len - numhunk * hunksize);
732 /* A one-hunk array prints the same as a single hunk. */
736 /* Cycle through the array (or hunk) printing the data. */
737 for (i = 0; i < numhunk; i++) {
738 for (j = 0; j < numelem; j++) {
746 for (; dp < data + len; dp++) {
749 if (dp + 1 != data + len ||
756 } else if (*dp == '"' ||
777 foo.s_addr = htonl(getULong(dp));
778 opcount = strlcpy(op, inet_ntoa(foo), opleft);
779 if (opcount >= opleft)
785 opcount = snprintf(op, opleft, "%ld",
787 if (opcount >= opleft || opcount == -1)
793 opcount = snprintf(op, opleft, "%lu",
794 (unsigned long)getULong(dp));
795 if (opcount >= opleft || opcount == -1)
801 opcount = snprintf(op, opleft, "%d",
803 if (opcount >= opleft || opcount == -1)
809 opcount = snprintf(op, opleft, "%u",
811 if (opcount >= opleft || opcount == -1)
817 opcount = snprintf(op, opleft, "%d",
819 if (opcount >= opleft || opcount == -1)
824 opcount = snprintf(op, opleft, "%d", *dp++);
825 if (opcount >= opleft || opcount == -1)
830 opcount = snprintf(op, opleft, "%x", *dp++);
831 if (opcount >= opleft || opcount == -1)
836 opcount = strlcpy(op,
837 *dp++ ? "true" : "false", opleft);
838 if (opcount >= opleft)
843 warning("Unexpected format code %c", fmtbuf[j]);
846 opleft -= strlen(op);
849 if (j + 1 < numelem && comma != ':') {
854 if (i + 1 < numhunk) {
864 warning("dhcp option too large");
869 do_packet(struct interface_info *interface, struct dhcp_packet *packet,
870 int len, unsigned int from_port, struct iaddr from, struct hardware *hfrom)
875 if (packet->hlen > sizeof(packet->chaddr)) {
876 note("Discarding packet with invalid hlen.");
880 memset(&tp, 0, sizeof(tp));
882 tp.packet_length = len;
883 tp.client_port = from_port;
884 tp.client_addr = from;
885 tp.interface = interface;
889 if (tp.options_valid &&
890 tp.options[DHO_DHCP_MESSAGE_TYPE].data)
891 tp.packet_type = tp.options[DHO_DHCP_MESSAGE_TYPE].data[0];
897 /* Free the data associated with the options. */
898 for (i = 0; i < 256; i++)
899 free(tp.options[i].data);