sbin/dhclient/options.c

   1 /* $OpenBSD: src/sbin/dhclient/options.c,v 1.37 2009/03/10 23:19:36 krw 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 <ctype.h>
  44
  45 #include "dhcpd.h"
  46
  47 int parse_option_buffer(struct option_data *, unsigned char *, int);
  48
  49 /*
  50  * Parse options out of the specified buffer, storing addresses of
  51  * option values in options and setting client->options_valid if
  52  * no errors are encountered.
  53  */
  54 int
  55 parse_option_buffer(struct option_data *options, unsigned char *buffer,
  56     int length)
  57 {
  58         unsigned char *s, *t, *end = buffer + length;
  59         int len, code;
  60
  61         for (s = buffer; *s != DHO_END && s < end; ) {
  62                 code = s[0];
  63
  64                 /* Pad options don't have a length - just skip them. */
  65                 if (code == DHO_PAD) {
  66                         s++;
  67                         continue;
  68                 }
  69
  70                 /*
  71                  * All options other than DHO_PAD and DHO_END have a
  72                  * one-byte length field.
  73                  */
  74                 if (s + 2 > end)
  75                         len = 0;
  76                 else
  77                         len = s[1];
  78
  79                 /*
  80                  * If the option claims to extend beyond the end of the buffer
  81                  * then mark the options buffer bad.
  82                  */
  83                 if (s + len + 2 > end) {
  84                         warning("option %s (%d) larger than buffer.",
  85                             dhcp_options[code].name, len);
  86                         warning("rejecting bogus offer.");
  87                         return (0);
  88                 }
  89                 /*
  90                  * If we haven't seen this option before, just make
  91                  * space for it and copy it there.
  92                  */
  93                 if (!options[code].data) {
  94                         if (!(t = calloc(1, len + 1)))
  95                                 error("Can't allocate storage for option %s.",
  96                                     dhcp_options[code].name);
  97                         /*
  98                          * Copy and NUL-terminate the option (in case
  99                          * it's an ASCII string).
 100                          */
 101                         memcpy(t, &s[2], len);
 102                         t[len] = 0;
 103                         options[code].len = len;
 104                         options[code].data = t;
 105                 } else {
 106                         /*
 107                          * If it's a repeat, concatenate it to whatever
 108                          * we last saw.   This is really only required
 109                          * for clients, but what the heck...
 110                          */
 111                         t = calloc(1, len + options[code].len + 1);
 112                         if (!t)
 113                                 error("Can't expand storage for option %s.",
 114                                     dhcp_options[code].name);
 115                         memcpy(t, options[code].data, options[code].len);
 116                         memcpy(t + options[code].len, &s[2], len);
 117                         options[code].len += len;
 118                         t[options[code].len] = 0;
 119                         free(options[code].data);
 120                         options[code].data = t;
 121                 }
 122                 s += len + 2;
 123         }
 124
 125         return (1);
 126 }
 127
 128 /*
 129  * Copy as many options as fit in buflen bytes of buf. Return the
 130  * offset of the start of the last option copied. A caller can check
 131  * to see if it's DHO_END to decide if all the options were copied.
 132  */
 133 int
 134 cons_options(unsigned char *buf, const int buflen, struct option_data *options)
 135 {
 136         int ix, incr, length, bufix, code, lastopt = -1;
 137
 138         bzero(buf, buflen);
 139
 140         if (buflen > 3)
 141                 memcpy(buf, DHCP_OPTIONS_COOKIE, 4);
 142         bufix = 4;
 143
 144         for (code = DHO_SUBNET_MASK; code < DHO_END; code++) {
 145                 if (!options[code].data)
 146                         continue;
 147
 148                 length = options[code].len;
 149                 if (bufix + length + 2*((length+254)/255) >= buflen)
 150                         return (lastopt);
 151
 152                 lastopt = bufix;
 153                 ix = 0;
 154
 155                 while (length) {
 156                         incr = length > 255 ? 255 : length;
 157
 158                         buf[bufix++] = code;
 159                         buf[bufix++] = incr;
 160                         memcpy(buf + bufix, options[code].data + ix, incr);
 161
 162                         length -= incr;
 163                         ix += incr;
 164                         bufix += incr;
 165                 }
 166         }
 167
 168         if (bufix < buflen) {
 169                 buf[bufix] = DHO_END;
 170                 lastopt = bufix;
 171         }
 172
 173         return (lastopt);
 174 }
 175
 176 /*
 177  * Format the specified option so that a human can easily read it.
 178  */
 179 char *
 180 pretty_print_option(unsigned int code, unsigned char *data, int len,
 181     int emit_commas, int emit_quotes)
 182 {
 183         static char optbuf[32768]; /* XXX */
 184         int hunksize = 0, numhunk = -1, numelem = 0;
 185         char fmtbuf[32], *op = optbuf;
 186         int i, j, k, opleft = sizeof(optbuf);
 187         unsigned char *dp = data;
 188         struct in_addr foo;
 189         char comma;
 190
 191         /* Code should be between 0 and 255. */
 192         if (code > 255)
 193                 error("pretty_print_option: bad code %d", code);
 194
 195         if (emit_commas)
 196                 comma = ',';
 197         else
 198                 comma = ' ';
 199
 200         /* Figure out the size of the data. */
 201         for (i = 0; dhcp_options[code].format[i]; i++) {
 202                 if (!numhunk) {
 203                         warning("%s: Excess information in format string: %s",
 204                             dhcp_options[code].name,
 205                             &(dhcp_options[code].format[i]));
 206                         break;
 207                 }
 208                 numelem++;
 209                 fmtbuf[i] = dhcp_options[code].format[i];
 210                 switch (dhcp_options[code].format[i]) {
 211                 case 'A':
 212                         --numelem;
 213                         fmtbuf[i] = 0;
 214                         numhunk = 0;
 215                         break;
 216                 case 'X':
 217                         for (k = 0; k < len; k++)
 218                                 if (!isascii(data[k]) ||
 219                                     !isprint(data[k]))
 220                                         break;
 221                         if (k == len) {
 222                                 fmtbuf[i] = 't';
 223                                 numhunk = -2;
 224                         } else {
 225                                 fmtbuf[i] = 'x';
 226                                 hunksize++;
 227                                 comma = ':';
 228                                 numhunk = 0;
 229                         }
 230                         fmtbuf[i + 1] = 0;
 231                         break;
 232                 case 't':
 233                         fmtbuf[i] = 't';
 234                         fmtbuf[i + 1] = 0;
 235                         numhunk = -2;
 236                         break;
 237                 case 'I':
 238                 case 'l':
 239                 case 'L':
 240                         hunksize += 4;
 241                         break;
 242                 case 's':
 243                 case 'S':
 244                         hunksize += 2;
 245                         break;
 246                 case 'b':
 247                 case 'B':
 248                 case 'f':
 249                         hunksize++;
 250                         break;
 251                 case 'e':
 252                         break;
 253                 default:
 254                         warning("%s: garbage in format string: %s",
 255                             dhcp_options[code].name,
 256                             &(dhcp_options[code].format[i]));
 257                         break;
 258                 }
 259         }
 260
 261         /* Check for too few bytes... */
 262         if (hunksize > len) {
 263                 warning("%s: expecting at least %d bytes; got %d",
 264                     dhcp_options[code].name, hunksize, len);
 265                 return ("<error>");
 266         }
 267         /* Check for too many bytes... */
 268         if (numhunk == -1 && hunksize < len)
 269                 warning("%s: %d extra bytes",
 270                     dhcp_options[code].name, len - hunksize);
 271
 272         /* If this is an array, compute its size. */
 273         if (!numhunk)
 274                 numhunk = len / hunksize;
 275         /* See if we got an exact number of hunks. */
 276         if (numhunk > 0 && numhunk * hunksize < len)
 277                 warning("%s: %d extra bytes at end of array",
 278                     dhcp_options[code].name, len - numhunk * hunksize);
 279
 280         /* A one-hunk array prints the same as a single hunk. */
 281         if (numhunk < 0)
 282                 numhunk = 1;
 283
 284         /* Cycle through the array (or hunk) printing the data. */
 285         for (i = 0; i < numhunk; i++) {
 286                 for (j = 0; j < numelem; j++) {
 287                         int opcount;
 288                         size_t oplen;
 289                         switch (fmtbuf[j]) {
 290                         case 't':
 291                                 if (emit_quotes) {
 292                                         *op++ = '"';
 293                                         opleft--;
 294                                 }
 295                                 for (; dp < data + len; dp++) {
 296                                         if (!isascii(*dp) ||
 297                                             !isprint(*dp)) {
 298                                                 if (dp + 1 != data + len ||
 299                                                     *dp != 0) {
 300                                                         size_t oplen;
 301                                                         snprintf(op, opleft,
 302                                                             "\\%03o", *dp);
 303                                                         oplen = strlen(op);
 304                                                         op += oplen;
 305                                                         opleft -= oplen;
 306                                                 }
 307                                         } else if (*dp == '"' ||
 308                                             *dp == '\'' ||
 309                                             *dp == '$' ||
 310                                             *dp == '`' ||
 311                                             *dp == '\\') {
 312                                                 *op++ = '\\';
 313                                                 *op++ = *dp;
 314                                                 opleft -= 2;
 315                                         } else {
 316                                                 *op++ = *dp;
 317                                                 opleft--;
 318                                         }
 319                                 }
 320                                 if (emit_quotes) {
 321                                         *op++ = '"';
 322                                         opleft--;
 323                                 }
 324
 325                                 *op = 0;
 326                                 break;
 327                         case 'I':
 328                                 foo.s_addr = htonl(getULong(dp));
 329                                 opcount = strlcpy(op, inet_ntoa(foo), opleft);
 330                                 if (opcount >= opleft)
 331                                         goto toobig;
 332                                 opleft -= opcount;
 333                                 dp += 4;
 334                                 break;
 335                         case 'l':
 336                                 opcount = snprintf(op, opleft, "%ld",
 337                                     (long)getLong(dp));
 338                                 if (opcount >= opleft || opcount == -1)
 339                                         goto toobig;
 340                                 opleft -= opcount;
 341                                 dp += 4;
 342                                 break;
 343                         case 'L':
 344                                 opcount = snprintf(op, opleft, "%ld",
 345                                     (unsigned long)getULong(dp));
 346                                 if (opcount >= opleft || opcount == -1)
 347                                         goto toobig;
 348                                 opleft -= opcount;
 349                                 dp += 4;
 350                                 break;
 351                         case 's':
 352                                 opcount = snprintf(op, opleft, "%d",
 353                                     getShort(dp));
 354                                 if (opcount >= opleft || opcount == -1)
 355                                         goto toobig;
 356                                 opleft -= opcount;
 357                                 dp += 2;
 358                                 break;
 359                         case 'S':
 360                                 opcount = snprintf(op, opleft, "%d",
 361                                     getUShort(dp));
 362                                 if (opcount >= opleft || opcount == -1)
 363                                         goto toobig;
 364                                 opleft -= opcount;
 365                                 dp += 2;
 366                                 break;
 367                         case 'b':
 368                                 opcount = snprintf(op, opleft, "%d",
 369                                     *(char *)dp++);
 370                                 if (opcount >= opleft || opcount == -1)
 371                                         goto toobig;
 372                                 opleft -= opcount;
 373                                 break;
 374                         case 'B':
 375                                 opcount = snprintf(op, opleft, "%d", *dp++);
 376                                 if (opcount >= opleft || opcount == -1)
 377                                         goto toobig;
 378                                 opleft -= opcount;
 379                                 break;
 380                         case 'x':
 381                                 opcount = snprintf(op, opleft, "%x", *dp++);
 382                                 if (opcount >= opleft || opcount == -1)
 383                                         goto toobig;
 384                                 opleft -= opcount;
 385                                 break;
 386                         case 'f':
 387                                 opcount = strlcpy(op,
 388                                     *dp++ ? "true" : "false", opleft);
 389                                 if (opcount >= opleft)
 390                                         goto toobig;
 391                                 opleft -= opcount;
 392                                 break;
 393                         default:
 394                                 warning("Unexpected format code %c", fmtbuf[j]);
 395                         }
 396                         oplen = strlen(op);
 397                         op += oplen;
 398                         opleft -= oplen;
 399                         if (opleft < 1)
 400                                 goto toobig;
 401                         if (j + 1 < numelem && comma != ':') {
 402                                 *op++ = ' ';
 403                                 opleft--;
 404                         }
 405                 }
 406                 if (i + 1 < numhunk) {
 407                         *op++ = comma;
 408                         opleft--;
 409                 }
 410                 if (opleft < 1)
 411                         goto toobig;
 412
 413         }
 414         return (optbuf);
 415  toobig:
 416         warning("dhcp option too large");
 417         return ("<error>");
 418 }
 419
 420 void
 421 do_packet(int len, unsigned int from_port, struct iaddr from,
 422     struct hardware *hfrom)
 423 {
 424         struct dhcp_packet *packet = &client->packet;
 425         struct option_data options[256];
 426         struct iaddrlist *ap;
 427         void (*handler)(struct iaddr, struct option_data *);
 428         char *type;
 429         int i, options_valid = 1;
 430
 431         if (packet->hlen > sizeof(packet->chaddr)) {
 432                 note("Discarding packet with invalid hlen.");
 433                 return;
 434         }
 435
 436         /*
 437          * Silently drop the packet if the client hardware address in the
 438          * packet is not the hardware address of the interface being managed.
 439          */
 440         if ((ifi->hw_address.hlen != packet->hlen) ||
 441             (memcmp(ifi->hw_address.haddr, packet->chaddr, packet->hlen)))
 442                 return;
 443
 444         memset(options, 0, sizeof(options));
 445
 446         if (memcmp(&packet->options, DHCP_OPTIONS_COOKIE, 4) == 0) {
 447                 /* Parse the BOOTP/DHCP options field. */
 448                 options_valid = parse_option_buffer(options,
 449                     &packet->options[4], sizeof(packet->options) - 4);
 450
 451                 /* Only DHCP packets have overload areas for options. */
 452                 if (options_valid &&
 453                     options[DHO_DHCP_MESSAGE_TYPE].data &&
 454                     options[DHO_DHCP_OPTION_OVERLOAD].data) {
 455                         if (options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 1)
 456                                 options_valid = parse_option_buffer(options,
 457                                     (unsigned char *)packet->file,
 458                                     sizeof(packet->file));
 459                         if (options_valid &&
 460                             options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 2)
 461                                 options_valid = parse_option_buffer(options,
 462                                     (unsigned char *)packet->sname,
 463                                     sizeof(packet->sname));
 464                 }
 465         }
 466
 467         type = "";
 468         handler = NULL;
 469
 470         if (options[DHO_DHCP_MESSAGE_TYPE].data) {
 471                 /* Always try a DHCP packet, even if a bad option was seen. */
 472                 switch (options[DHO_DHCP_MESSAGE_TYPE].data[0]) {
 473                 case DHCPOFFER:
 474                         handler = dhcpoffer;
 475                         type = "DHCPOFFER";
 476                         break;
 477                 case DHCPNAK:
 478                         handler = dhcpnak;
 479                         type = "DHCPNACK";
 480                         break;
 481                 case DHCPACK:
 482                         handler = dhcpack;
 483                         type = "DHCPACK";
 484                         break;
 485                 default:
 486                         break;
 487                 }
 488         } else if (options_valid && packet->op == BOOTREPLY) {
 489                 handler = dhcpoffer;
 490                 type = "BOOTREPLY";
 491         }
 492
 493         if (handler && client->xid == client->packet.xid) {
 494                 if (hfrom->hlen == 6)
 495                         note("%s from %s (%s)", type, piaddr(from),
 496                             ether_ntoa((struct ether_addr *)hfrom->haddr));
 497                 else
 498                         note("%s from %s", type, piaddr(from));
 499         } else
 500                 handler = NULL;
 501
 502         for (ap = config->reject_list; ap && handler; ap = ap->next)
 503                 if (addr_eq(from, ap->addr)) {
 504                         note("%s from %s rejected.", type, piaddr(from));
 505                         handler = NULL;
 506                 }
 507
 508         if (handler)
 509                 (*handler)(from, options);
 510
 511         for (i = 0; i < 256; i++)
 512                 if (options[i].len && options[i].data)
 513                         free(options[i].data);
 514 }