/* $OpenBSD: options.c,v 1.13 2004/09/21 04:07:04 david Exp $ */ /* DHCP options parsing and reassembly. */ /* * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of The Internet Software Consortium nor the names * of its contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * This software has been written for the Internet Software Consortium * by Ted Lemon in cooperation with Vixie * Enterprises. To learn more about the Internet Software Consortium, * see ``http://www.vix.com/isc''. To learn more about Vixie * Enterprises, see ``http://www.vix.com''. */ #include #define DHCP_OPTION_DATA #include "dhcpd.h" int bad_options = 0; int bad_options_max = 5; void parse_options(struct packet *); void parse_option_buffer(struct packet *, unsigned char *, int); int store_options(unsigned char *, int, struct tree_cache **, unsigned char *, int, int, int, int); /* * Parse all available options out of the specified packet. */ void parse_options(struct packet *packet) { /* Initially, zero all option pointers. */ memset(packet->options, 0, sizeof(packet->options)); /* If we don't see the magic cookie, there's nothing to parse. */ if (memcmp(packet->raw->options, DHCP_OPTIONS_COOKIE, 4)) { packet->options_valid = 0; return; } /* * Go through the options field, up to the end of the packet or * the End field. */ parse_option_buffer(packet, &packet->raw->options[4], packet->packet_length - DHCP_FIXED_NON_UDP - 4); /* * If we parsed a DHCP Option Overload option, parse more * options out of the buffer(s) containing them. */ if (packet->options_valid && packet->options[DHO_DHCP_OPTION_OVERLOAD].data) { if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 1) parse_option_buffer(packet, (unsigned char *)packet->raw->file, sizeof(packet->raw->file)); if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 2) parse_option_buffer(packet, (unsigned char *)packet->raw->sname, sizeof(packet->raw->sname)); } } /* * Parse options out of the specified buffer, storing addresses of * option values in packet->options and setting packet->options_valid if * no errors are encountered. */ void parse_option_buffer(struct packet *packet, unsigned char *buffer, int length) { unsigned char *s, *t, *end = buffer + length; int len, code; for (s = buffer; *s != DHO_END && s < end; ) { code = s[0]; /* Pad options don't have a length - just skip them. */ if (code == DHO_PAD) { s++; continue; } if (s + 2 > end) { len = 65536; goto bogus; } /* * All other fields (except end, see above) have a * one-byte length. */ len = s[1]; /* * If the length is outrageous, silently skip the rest, * and mark the packet bad. Unfortunately some crappy * dhcp servers always seem to give us garbage on the * end of a packet. so rather than keep refusing, give * up and try to take one after seeing a few without * anything good. */ if (s + len + 2 > end) { bogus: bad_options++; warning("option %s (%d) %s.", dhcp_options[code].name, len, "larger than buffer"); if (bad_options == bad_options_max) { packet->options_valid = 1; bad_options = 0; warning("Many bogus options seen in offers. " "Taking this offer in spite of bogus " "options - hope for the best!"); } else { warning("rejecting bogus offer."); packet->options_valid = 0; } return; } /* * If we haven't seen this option before, just make * space for it and copy it there. */ if (!packet->options[code].data) { if (!(t = calloc(1, len + 1))) error("Can't allocate storage for option %s.", dhcp_options[code].name); /* * Copy and NUL-terminate the option (in case * it's an ASCII string. */ memcpy(t, &s[2], len); t[len] = 0; packet->options[code].len = len; packet->options[code].data = t; } else { /* * If it's a repeat, concatenate it to whatever * we last saw. This is really only required * for clients, but what the heck... */ t = calloc(1, len + packet->options[code].len + 1); if (!t) error("Can't expand storage for option %s.", dhcp_options[code].name); memcpy(t, packet->options[code].data, packet->options[code].len); memcpy(t + packet->options[code].len, &s[2], len); packet->options[code].len += len; t[packet->options[code].len] = 0; free(packet->options[code].data); packet->options[code].data = t; } s += len + 2; } packet->options_valid = 1; } /* * cons options into a big buffer, and then split them out into the * three separate buffers if needed. This allows us to cons up a set of * vendor options using the same routine. */ int cons_options(struct packet *inpacket, struct dhcp_packet *outpacket, int mms, struct tree_cache **options, int overload, /* Overload flags that may be set. */ int terminate, int bootpp, u_int8_t *prl, int prl_len) { unsigned char priority_list[300], buffer[4096]; int priority_len, main_buffer_size, mainbufix, bufix; int option_size, length; /* * If the client has provided a maximum DHCP message size, use * that; otherwise, if it's BOOTP, only 64 bytes; otherwise use * up to the minimum IP MTU size (576 bytes). * * XXX if a BOOTP client specifies a max message size, we will * honor it. */ if (!mms && inpacket && inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data && (inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].len >= sizeof(u_int16_t))) mms = getUShort( inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data); if (mms) main_buffer_size = mms - DHCP_FIXED_LEN; else if (bootpp) main_buffer_size = 64; else main_buffer_size = 576 - DHCP_FIXED_LEN; if (main_buffer_size > sizeof(buffer)) main_buffer_size = sizeof(buffer); /* Preload the option priority list with mandatory options. */ priority_len = 0; priority_list[priority_len++] = DHO_DHCP_MESSAGE_TYPE; priority_list[priority_len++] = DHO_DHCP_SERVER_IDENTIFIER; priority_list[priority_len++] = DHO_DHCP_LEASE_TIME; priority_list[priority_len++] = DHO_DHCP_MESSAGE; /* * If the client has provided a list of options that it wishes * returned, use it to prioritize. Otherwise, prioritize based * on the default priority list. */ if (inpacket && inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data) { int prlen = inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].len; if (prlen + priority_len > sizeof(priority_list)) prlen = sizeof(priority_list) - priority_len; memcpy(&priority_list[priority_len], inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data, prlen); priority_len += prlen; prl = priority_list; } else if (prl) { if (prl_len + priority_len > sizeof(priority_list)) prl_len = sizeof(priority_list) - priority_len; memcpy(&priority_list[priority_len], prl, prl_len); priority_len += prl_len; prl = priority_list; } else { memcpy(&priority_list[priority_len], dhcp_option_default_priority_list, sizeof_dhcp_option_default_priority_list); priority_len += sizeof_dhcp_option_default_priority_list; } /* Copy the options into the big buffer... */ option_size = store_options( buffer, (main_buffer_size - 7 + ((overload & 1) ? DHCP_FILE_LEN : 0) + ((overload & 2) ? DHCP_SNAME_LEN : 0)), options, priority_list, priority_len, main_buffer_size, (main_buffer_size + ((overload & 1) ? DHCP_FILE_LEN : 0)), terminate); /* Put the cookie up front... */ memcpy(outpacket->options, DHCP_OPTIONS_COOKIE, 4); mainbufix = 4; /* * If we're going to have to overload, store the overload option * at the beginning. If we can, though, just store the whole * thing in the packet's option buffer and leave it at that. */ if (option_size <= main_buffer_size - mainbufix) { memcpy(&outpacket->options[mainbufix], buffer, option_size); mainbufix += option_size; if (mainbufix < main_buffer_size) outpacket->options[mainbufix++] = DHO_END; length = DHCP_FIXED_NON_UDP + mainbufix; } else { outpacket->options[mainbufix++] = DHO_DHCP_OPTION_OVERLOAD; outpacket->options[mainbufix++] = 1; if (option_size > main_buffer_size - mainbufix + DHCP_FILE_LEN) outpacket->options[mainbufix++] = 3; else outpacket->options[mainbufix++] = 1; memcpy(&outpacket->options[mainbufix], buffer, main_buffer_size - mainbufix); bufix = main_buffer_size - mainbufix; length = DHCP_FIXED_NON_UDP + mainbufix; if (overload & 1) { if (option_size - bufix <= DHCP_FILE_LEN) { memcpy(outpacket->file, &buffer[bufix], option_size - bufix); mainbufix = option_size - bufix; if (mainbufix < DHCP_FILE_LEN) outpacket->file[mainbufix++] = DHO_END; while (mainbufix < DHCP_FILE_LEN) outpacket->file[mainbufix++] = DHO_PAD; } else { memcpy(outpacket->file, &buffer[bufix], DHCP_FILE_LEN); bufix += DHCP_FILE_LEN; } } if ((overload & 2) && option_size < bufix) { memcpy(outpacket->sname, &buffer[bufix], option_size - bufix); mainbufix = option_size - bufix; if (mainbufix < DHCP_SNAME_LEN) outpacket->file[mainbufix++] = DHO_END; while (mainbufix < DHCP_SNAME_LEN) outpacket->file[mainbufix++] = DHO_PAD; } } return (length); } /* * Store all the requested options into the requested buffer. */ int store_options(unsigned char *buffer, int buflen, struct tree_cache **options, unsigned char *priority_list, int priority_len, int first_cutoff, int second_cutoff, int terminate) { int bufix = 0, option_stored[256], i, ix, tto; /* Zero out the stored-lengths array. */ memset(option_stored, 0, sizeof(option_stored)); /* * Copy out the options in the order that they appear in the * priority list... */ for (i = 0; i < priority_len; i++) { /* Code for next option to try to store. */ int code = priority_list[i]; int optstart; /* * Number of bytes left to store (some may already have * been stored by a previous pass). */ int length; /* If no data is available for this option, skip it. */ if (!options[code]) { continue; } /* * The client could ask for things that are mandatory, * in which case we should avoid storing them twice... */ if (option_stored[code]) continue; option_stored[code] = 1; /* We should now have a constant length for the option. */ length = options[code]->len; /* Do we add a NUL? */ if (terminate && dhcp_options[code].format[0] == 't') { length++; tto = 1; } else tto = 0; /* Try to store the option. */ /* * If the option's length is more than 255, we must * store it in multiple hunks. Store 255-byte hunks * first. However, in any case, if the option data will * cross a buffer boundary, split it across that * boundary. */ ix = 0; optstart = bufix; while (length) { unsigned char incr = length > 255 ? 255 : length; /* * If this hunk of the buffer will cross a * boundary, only go up to the boundary in this * pass. */ if (bufix < first_cutoff && bufix + incr > first_cutoff) incr = first_cutoff - bufix; else if (bufix < second_cutoff && bufix + incr > second_cutoff) incr = second_cutoff - bufix; /* * If this option is going to overflow the * buffer, skip it. */ if (bufix + 2 + incr > buflen) { bufix = optstart; break; } /* Everything looks good - copy it in! */ buffer[bufix] = code; buffer[bufix + 1] = incr; if (tto && incr == length) { memcpy(buffer + bufix + 2, options[code]->value + ix, incr - 1); buffer[bufix + 2 + incr - 1] = 0; } else memcpy(buffer + bufix + 2, options[code]->value + ix, incr); length -= incr; ix += incr; bufix += 2 + incr; } } return (bufix); } /* * Format the specified option so that a human can easily read it. */ char * pretty_print_option(unsigned int code, unsigned char *data, int len, int emit_commas, int emit_quotes) { static char optbuf[32768]; /* XXX */ int hunksize = 0, numhunk = -1, numelem = 0; char fmtbuf[32], *op = optbuf; int i, j, k, opleft = sizeof(optbuf); unsigned char *dp = data; struct in_addr foo; char comma; /* Code should be between 0 and 255. */ if (code > 255) error("pretty_print_option: bad code %d", code); if (emit_commas) comma = ','; else comma = ' '; /* Figure out the size of the data. */ for (i = 0; dhcp_options[code].format[i]; i++) { if (!numhunk) { warning("%s: Excess information in format string: %s", dhcp_options[code].name, &(dhcp_options[code].format[i])); break; } numelem++; fmtbuf[i] = dhcp_options[code].format[i]; switch (dhcp_options[code].format[i]) { case 'A': --numelem; fmtbuf[i] = 0; numhunk = 0; break; case 'X': for (k = 0; k < len; k++) if (!isascii(data[k]) || !isprint(data[k])) break; if (k == len) { fmtbuf[i] = 't'; numhunk = -2; } else { fmtbuf[i] = 'x'; hunksize++; comma = ':'; numhunk = 0; } fmtbuf[i + 1] = 0; break; case 't': fmtbuf[i] = 't'; fmtbuf[i + 1] = 0; numhunk = -2; break; case 'I': case 'l': case 'L': hunksize += 4; break; case 's': case 'S': hunksize += 2; break; case 'b': case 'B': case 'f': hunksize++; break; case 'e': break; default: warning("%s: garbage in format string: %s", dhcp_options[code].name, &(dhcp_options[code].format[i])); break; } } /* Check for too few bytes... */ if (hunksize > len) { warning("%s: expecting at least %d bytes; got %d", dhcp_options[code].name, hunksize, len); return (""); } /* Check for too many bytes... */ if (numhunk == -1 && hunksize < len) warning("%s: %d extra bytes", dhcp_options[code].name, len - hunksize); /* If this is an array, compute its size. */ if (!numhunk) numhunk = len / hunksize; /* See if we got an exact number of hunks. */ if (numhunk > 0 && numhunk * hunksize < len) warning("%s: %d extra bytes at end of array", dhcp_options[code].name, len - numhunk * hunksize); /* A one-hunk array prints the same as a single hunk. */ if (numhunk < 0) numhunk = 1; /* Cycle through the array (or hunk) printing the data. */ for (i = 0; i < numhunk; i++) { for (j = 0; j < numelem; j++) { int opcount; switch (fmtbuf[j]) { case 't': if (emit_quotes) { *op++ = '"'; opleft--; } for (; dp < data + len; dp++) { if (!isascii(*dp) || !isprint(*dp)) { if (dp + 1 != data + len || *dp != 0) { snprintf(op, opleft, "\\%03o", *dp); op += 4; opleft -= 4; } } else if (*dp == '"' || *dp == '\'' || *dp == '$' || *dp == '`' || *dp == '\\') { *op++ = '\\'; *op++ = *dp; opleft -= 2; } else { *op++ = *dp; opleft--; } } if (emit_quotes) { *op++ = '"'; opleft--; } *op = 0; break; case 'I': foo.s_addr = htonl(getULong(dp)); opcount = strlcpy(op, inet_ntoa(foo), opleft); if (opcount >= opleft) goto toobig; opleft -= opcount; dp += 4; break; case 'l': opcount = snprintf(op, opleft, "%ld", (long)getLong(dp)); if (opcount >= opleft) goto toobig; opleft -= opcount; dp += 4; break; case 'L': opcount = snprintf(op, opleft, "%ld", (unsigned long)getULong(dp)); if (opcount >= opleft) goto toobig; opleft -= opcount; dp += 4; break; case 's': opcount = snprintf(op, opleft, "%d", getShort(dp)); if (opcount >= opleft) goto toobig; opleft -= opcount; dp += 2; break; case 'S': opcount = snprintf(op, opleft, "%d", getUShort(dp)); if (opcount >= opleft) goto toobig; opleft -= opcount; dp += 2; break; case 'b': opcount = snprintf(op, opleft, "%d", *(char *)dp++); if (opcount >= opleft) goto toobig; opleft -= opcount; break; case 'B': opcount = snprintf(op, opleft, "%d", *dp++); if (opcount >= opleft) goto toobig; opleft -= opcount; break; case 'x': opcount = snprintf(op, opleft, "%x", *dp++); if (opcount >= opleft) goto toobig; opleft -= opcount; break; case 'f': opcount = strlcpy(op, *dp++ ? "true" : "false", opleft); if (opcount >= opleft) goto toobig; opleft -= opcount; break; default: warning("Unexpected format code %c", fmtbuf[j]); } op += strlen(op); opleft -= strlen(op); if (opleft < 1) goto toobig; if (j + 1 < numelem && comma != ':') { *op++ = ' '; opleft--; } } if (i + 1 < numhunk) { *op++ = comma; opleft--; } if (opleft < 1) goto toobig; } return (optbuf); toobig: warning("dhcp option too large"); return (""); } void do_packet(struct interface_info *interface, struct dhcp_packet *packet, int len, unsigned int from_port, struct iaddr from, struct hardware *hfrom) { struct packet tp; int i; if (packet->hlen > sizeof(packet->chaddr)) { note("Discarding packet with invalid hlen."); return; } memset(&tp, 0, sizeof(tp)); tp.raw = packet; tp.packet_length = len; tp.client_port = from_port; tp.client_addr = from; tp.interface = interface; tp.haddr = hfrom; parse_options(&tp); if (tp.options_valid && tp.options[DHO_DHCP_MESSAGE_TYPE].data) tp.packet_type = tp.options[DHO_DHCP_MESSAGE_TYPE].data[0]; if (tp.packet_type) dhcp(&tp); else bootp(&tp); /* Free the data associated with the options. */ for (i = 0; i < 256; i++) if (tp.options[i].len && tp.options[i].data) free(tp.options[i].data); }