1 /* $OpenBSD: options.c,v 1.15 2004/12/26 03:17:07 deraadt Exp $ */
3 /* DHCP options parsing and reassembly. */
6 * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
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.
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
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''.
45 #define DHCP_OPTION_DATA
49 int bad_options_max = 5;
51 void parse_options(struct packet *);
52 void parse_option_buffer(struct packet *, unsigned char *, int);
53 int store_options(unsigned char *, int, struct tree_cache **,
54 unsigned char *, int, int, int, int);
58 * Parse all available options out of the specified packet.
61 parse_options(struct packet *packet)
63 /* Initially, zero all option pointers. */
64 memset(packet->options, 0, sizeof(packet->options));
66 /* If we don't see the magic cookie, there's nothing to parse. */
67 if (memcmp(packet->raw->options, DHCP_OPTIONS_COOKIE, 4)) {
68 packet->options_valid = 0;
73 * Go through the options field, up to the end of the packet or
76 parse_option_buffer(packet, &packet->raw->options[4],
77 packet->packet_length - DHCP_FIXED_NON_UDP - 4);
80 * If we parsed a DHCP Option Overload option, parse more
81 * options out of the buffer(s) containing them.
83 if (packet->options_valid &&
84 packet->options[DHO_DHCP_OPTION_OVERLOAD].data) {
85 if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 1)
86 parse_option_buffer(packet,
87 (unsigned char *)packet->raw->file,
88 sizeof(packet->raw->file));
89 if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 2)
90 parse_option_buffer(packet,
91 (unsigned char *)packet->raw->sname,
92 sizeof(packet->raw->sname));
97 * Parse options out of the specified buffer, storing addresses of
98 * option values in packet->options and setting packet->options_valid if
99 * no errors are encountered.
102 parse_option_buffer(struct packet *packet,
103 unsigned char *buffer, int length)
105 unsigned char *s, *t, *end = buffer + length;
108 for (s = buffer; *s != DHO_END && s < end; ) {
111 /* Pad options don't have a length - just skip them. */
112 if (code == DHO_PAD) {
122 * All other fields (except end, see above) have a
128 * If the length is outrageous, silently skip the rest,
129 * and mark the packet bad. Unfortunately some crappy
130 * dhcp servers always seem to give us garbage on the
131 * end of a packet. so rather than keep refusing, give
132 * up and try to take one after seeing a few without
135 if (s + len + 2 > end) {
138 warning("option %s (%d) %s.",
139 dhcp_options[code].name, len,
140 "larger than buffer");
141 if (bad_options == bad_options_max) {
142 packet->options_valid = 1;
144 warning("Many bogus options seen in offers. "
145 "Taking this offer in spite of bogus "
146 "options - hope for the best!");
148 warning("rejecting bogus offer.");
149 packet->options_valid = 0;
154 * If we haven't seen this option before, just make
155 * space for it and copy it there.
157 if (!packet->options[code].data) {
158 if (!(t = calloc(1, len + 1)))
159 error("Can't allocate storage for option %s.",
160 dhcp_options[code].name);
162 * Copy and NUL-terminate the option (in case
163 * it's an ASCII string.
165 memcpy(t, &s[2], len);
167 packet->options[code].len = len;
168 packet->options[code].data = t;
171 * If it's a repeat, concatenate it to whatever
172 * we last saw. This is really only required
173 * for clients, but what the heck...
175 t = calloc(1, len + packet->options[code].len + 1);
177 error("Can't expand storage for option %s.",
178 dhcp_options[code].name);
179 memcpy(t, packet->options[code].data,
180 packet->options[code].len);
181 memcpy(t + packet->options[code].len,
183 packet->options[code].len += len;
184 t[packet->options[code].len] = 0;
185 free(packet->options[code].data);
186 packet->options[code].data = t;
190 packet->options_valid = 1;
194 * cons options into a big buffer, and then split them out into the
195 * three separate buffers if needed. This allows us to cons up a set of
196 * vendor options using the same routine.
199 cons_options(struct packet *inpacket, struct dhcp_packet *outpacket,
200 int mms, struct tree_cache **options,
201 int overload, /* Overload flags that may be set. */
202 int terminate, int bootpp, u_int8_t *prl, int prl_len)
204 unsigned char priority_list[300], buffer[4096];
205 int priority_len, main_buffer_size, mainbufix, bufix;
206 int option_size, length;
209 * If the client has provided a maximum DHCP message size, use
210 * that; otherwise, if it's BOOTP, only 64 bytes; otherwise use
211 * up to the minimum IP MTU size (576 bytes).
213 * XXX if a BOOTP client specifies a max message size, we will
218 inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data &&
219 (inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].len >=
222 inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data);
225 main_buffer_size = mms - DHCP_FIXED_LEN;
227 main_buffer_size = 64;
229 main_buffer_size = 576 - DHCP_FIXED_LEN;
231 if (main_buffer_size > sizeof(buffer))
232 main_buffer_size = sizeof(buffer);
234 /* Preload the option priority list with mandatory options. */
236 priority_list[priority_len++] = DHO_DHCP_MESSAGE_TYPE;
237 priority_list[priority_len++] = DHO_DHCP_SERVER_IDENTIFIER;
238 priority_list[priority_len++] = DHO_DHCP_LEASE_TIME;
239 priority_list[priority_len++] = DHO_DHCP_MESSAGE;
242 * If the client has provided a list of options that it wishes
243 * returned, use it to prioritize. Otherwise, prioritize based
244 * on the default priority list.
247 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data) {
249 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].len;
250 if (prlen + priority_len > sizeof(priority_list))
251 prlen = sizeof(priority_list) - priority_len;
253 memcpy(&priority_list[priority_len],
254 inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data,
256 priority_len += prlen;
259 if (prl_len + priority_len > sizeof(priority_list))
260 prl_len = sizeof(priority_list) - priority_len;
262 memcpy(&priority_list[priority_len], prl, prl_len);
263 priority_len += prl_len;
266 memcpy(&priority_list[priority_len],
267 dhcp_option_default_priority_list,
268 sizeof_dhcp_option_default_priority_list);
269 priority_len += sizeof_dhcp_option_default_priority_list;
272 /* Copy the options into the big buffer... */
273 option_size = store_options(
275 (main_buffer_size - 7 + ((overload & 1) ? DHCP_FILE_LEN : 0) +
276 ((overload & 2) ? DHCP_SNAME_LEN : 0)),
277 options, priority_list, priority_len, main_buffer_size,
278 (main_buffer_size + ((overload & 1) ? DHCP_FILE_LEN : 0)),
281 /* Put the cookie up front... */
282 memcpy(outpacket->options, DHCP_OPTIONS_COOKIE, 4);
286 * If we're going to have to overload, store the overload option
287 * at the beginning. If we can, though, just store the whole
288 * thing in the packet's option buffer and leave it at that.
290 if (option_size <= main_buffer_size - mainbufix) {
291 memcpy(&outpacket->options[mainbufix],
292 buffer, option_size);
293 mainbufix += option_size;
294 if (mainbufix < main_buffer_size)
295 outpacket->options[mainbufix++] = DHO_END;
296 length = DHCP_FIXED_NON_UDP + mainbufix;
298 outpacket->options[mainbufix++] = DHO_DHCP_OPTION_OVERLOAD;
299 outpacket->options[mainbufix++] = 1;
301 main_buffer_size - mainbufix + DHCP_FILE_LEN)
302 outpacket->options[mainbufix++] = 3;
304 outpacket->options[mainbufix++] = 1;
306 memcpy(&outpacket->options[mainbufix],
307 buffer, main_buffer_size - mainbufix);
308 bufix = main_buffer_size - mainbufix;
309 length = DHCP_FIXED_NON_UDP + mainbufix;
311 if (option_size - bufix <= DHCP_FILE_LEN) {
312 memcpy(outpacket->file,
313 &buffer[bufix], option_size - bufix);
314 mainbufix = option_size - bufix;
315 if (mainbufix < DHCP_FILE_LEN)
316 outpacket->file[mainbufix++] = (char)DHO_END;
317 while (mainbufix < DHCP_FILE_LEN)
318 outpacket->file[mainbufix++] = (char)DHO_PAD;
320 memcpy(outpacket->file,
321 &buffer[bufix], DHCP_FILE_LEN);
322 bufix += DHCP_FILE_LEN;
325 if ((overload & 2) && option_size < bufix) {
326 memcpy(outpacket->sname,
327 &buffer[bufix], option_size - bufix);
329 mainbufix = option_size - bufix;
330 if (mainbufix < DHCP_SNAME_LEN)
331 outpacket->file[mainbufix++] = (char)DHO_END;
332 while (mainbufix < DHCP_SNAME_LEN)
333 outpacket->file[mainbufix++] = (char)DHO_PAD;
340 * Store all the requested options into the requested buffer.
343 store_options(unsigned char *buffer, int buflen, struct tree_cache **options,
344 unsigned char *priority_list, int priority_len, int first_cutoff,
345 int second_cutoff, int terminate)
347 int bufix = 0, option_stored[256], i, ix, tto;
349 /* Zero out the stored-lengths array. */
350 memset(option_stored, 0, sizeof(option_stored));
353 * Copy out the options in the order that they appear in the
356 for (i = 0; i < priority_len; i++) {
357 /* Code for next option to try to store. */
358 int code = priority_list[i];
362 * Number of bytes left to store (some may already have
363 * been stored by a previous pass).
367 /* If no data is available for this option, skip it. */
368 if (!options[code]) {
373 * The client could ask for things that are mandatory,
374 * in which case we should avoid storing them twice...
376 if (option_stored[code])
378 option_stored[code] = 1;
380 /* We should now have a constant length for the option. */
381 length = options[code]->len;
383 /* Do we add a NUL? */
384 if (terminate && dhcp_options[code].format[0] == 't') {
390 /* Try to store the option. */
393 * If the option's length is more than 255, we must
394 * store it in multiple hunks. Store 255-byte hunks
395 * first. However, in any case, if the option data will
396 * cross a buffer boundary, split it across that
403 unsigned char incr = length > 255 ? 255 : length;
406 * If this hunk of the buffer will cross a
407 * boundary, only go up to the boundary in this
410 if (bufix < first_cutoff &&
411 bufix + incr > first_cutoff)
412 incr = first_cutoff - bufix;
413 else if (bufix < second_cutoff &&
414 bufix + incr > second_cutoff)
415 incr = second_cutoff - bufix;
418 * If this option is going to overflow the
421 if (bufix + 2 + incr > buflen) {
426 /* Everything looks good - copy it in! */
427 buffer[bufix] = code;
428 buffer[bufix + 1] = incr;
429 if (tto && incr == length) {
430 memcpy(buffer + bufix + 2,
431 options[code]->value + ix, incr - 1);
432 buffer[bufix + 2 + incr - 1] = 0;
434 memcpy(buffer + bufix + 2,
435 options[code]->value + ix, incr);
445 * Format the specified option so that a human can easily read it.
448 pretty_print_option(unsigned int code, unsigned char *data, int len,
449 int emit_commas, int emit_quotes)
451 static char optbuf[32768]; /* XXX */
452 int hunksize = 0, numhunk = -1, numelem = 0;
453 char fmtbuf[32], *op = optbuf;
454 int i, j, k, opleft = sizeof(optbuf);
455 unsigned char *dp = data;
459 /* Code should be between 0 and 255. */
461 error("pretty_print_option: bad code %d", code);
468 /* Figure out the size of the data. */
469 for (i = 0; dhcp_options[code].format[i]; i++) {
471 warning("%s: Excess information in format string: %s",
472 dhcp_options[code].name,
473 &(dhcp_options[code].format[i]));
477 fmtbuf[i] = dhcp_options[code].format[i];
478 switch (dhcp_options[code].format[i]) {
485 for (k = 0; k < len; k++)
486 if (!isascii(data[k]) ||
522 warning("%s: garbage in format string: %s",
523 dhcp_options[code].name,
524 &(dhcp_options[code].format[i]));
529 /* Check for too few bytes... */
530 if (hunksize > len) {
531 warning("%s: expecting at least %d bytes; got %d",
532 dhcp_options[code].name, hunksize, len);
535 /* Check for too many bytes... */
536 if (numhunk == -1 && hunksize < len)
537 warning("%s: %d extra bytes",
538 dhcp_options[code].name, len - hunksize);
540 /* If this is an array, compute its size. */
542 numhunk = len / hunksize;
543 /* See if we got an exact number of hunks. */
544 if (numhunk > 0 && numhunk * hunksize < len)
545 warning("%s: %d extra bytes at end of array",
546 dhcp_options[code].name, len - numhunk * hunksize);
548 /* A one-hunk array prints the same as a single hunk. */
552 /* Cycle through the array (or hunk) printing the data. */
553 for (i = 0; i < numhunk; i++) {
554 for (j = 0; j < numelem; j++) {
562 for (; dp < data + len; dp++) {
565 if (dp + 1 != data + len ||
572 } else if (*dp == '"' ||
593 foo.s_addr = htonl(getULong(dp));
594 opcount = strlcpy(op, inet_ntoa(foo), opleft);
595 if (opcount >= opleft)
601 opcount = snprintf(op, opleft, "%ld",
603 if (opcount >= opleft || opcount == -1)
609 opcount = snprintf(op, opleft, "%ld",
610 (unsigned long)getULong(dp));
611 if (opcount >= opleft || opcount == -1)
617 opcount = snprintf(op, opleft, "%d",
619 if (opcount >= opleft || opcount == -1)
625 opcount = snprintf(op, opleft, "%d",
627 if (opcount >= opleft || opcount == -1)
633 opcount = snprintf(op, opleft, "%d",
635 if (opcount >= opleft || opcount == -1)
640 opcount = snprintf(op, opleft, "%d", *dp++);
641 if (opcount >= opleft || opcount == -1)
646 opcount = snprintf(op, opleft, "%x", *dp++);
647 if (opcount >= opleft || opcount == -1)
652 opcount = strlcpy(op,
653 *dp++ ? "true" : "false", opleft);
654 if (opcount >= opleft)
659 warning("Unexpected format code %c", fmtbuf[j]);
662 opleft -= strlen(op);
665 if (j + 1 < numelem && comma != ':') {
670 if (i + 1 < numhunk) {
680 warning("dhcp option too large");
685 do_packet(struct interface_info *interface, struct dhcp_packet *packet,
686 int len, unsigned int from_port, struct iaddr from, struct hardware *hfrom)
691 if (packet->hlen > sizeof(packet->chaddr)) {
692 note("Discarding packet with invalid hlen.");
696 memset(&tp, 0, sizeof(tp));
698 tp.packet_length = len;
699 tp.client_port = from_port;
700 tp.client_addr = from;
701 tp.interface = interface;
705 if (tp.options_valid &&
706 tp.options[DHO_DHCP_MESSAGE_TYPE].data)
707 tp.packet_type = tp.options[DHO_DHCP_MESSAGE_TYPE].data[0];
713 /* Free the data associated with the options. */
714 for (i = 0; i < 256; i++)
715 if (tp.options[i].len && tp.options[i].data)
716 free(tp.options[i].data);