sbin/dhclient/options.c

   1 /*      $OpenBSD: src/sbin/dhclient/options.c,v 1.39 2011/05/11 14:38:36 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(struct option_data *options)
 135 {
 136         unsigned char *buf = client->packet.options;
 137         int buflen = 576 - DHCP_FIXED_LEN;
 138         int ix, incr, length, bufix, code, lastopt = -1;
 139
 140         bzero(buf, buflen);
 141
 142         memcpy(buf, DHCP_OPTIONS_COOKIE, 4);
 143         if (options[DHO_DHCP_MESSAGE_TYPE].data) {
 144                 memcpy(&buf[4], DHCP_OPTIONS_MESSAGE_TYPE, 3);
 145                 buf[6] = options[DHO_DHCP_MESSAGE_TYPE].data[0];
 146                 bufix = 7;
 147         } else
 148                 bufix = 4;
 149
 150         for (code = DHO_SUBNET_MASK; code < DHO_END; code++) {
 151                 if (!options[code].data || code == DHO_DHCP_MESSAGE_TYPE)
 152                         continue;
 153
 154                 length = options[code].len;
 155                 if (bufix + length + 2*((length+254)/255) >= buflen)
 156                         return (lastopt);
 157
 158                 lastopt = bufix;
 159                 ix = 0;
 160
 161                 while (length) {
 162                         incr = length > 255 ? 255 : length;
 163
 164                         buf[bufix++] = code;
 165                         buf[bufix++] = incr;
 166                         memcpy(buf + bufix, options[code].data + ix, incr);
 167
 168                         length -= incr;
 169                         ix += incr;
 170                         bufix += incr;
 171                 }
 172         }
 173
 174         if (bufix < buflen) {
 175                 buf[bufix] = DHO_END;
 176                 lastopt = bufix;
 177         }
 178
 179         return (lastopt);
 180 }
 181
 182 /*
 183  * Format the specified option so that a human can easily read it.
 184  */
 185 char *
 186 pretty_print_option(unsigned int code, unsigned char *data, int len,
 187     int emit_commas, int emit_quotes)
 188 {
 189         static char optbuf[32768]; /* XXX */
 190         int hunksize = 0, numhunk = -1, numelem = 0;
 191         char fmtbuf[32], *op = optbuf;
 192         int i, j, k, opleft = sizeof(optbuf);
 193         unsigned char *dp = data;
 194         struct in_addr foo;
 195         char comma;
 196
 197         /* Code should be between 0 and 255. */
 198         if (code > 255)
 199                 error("pretty_print_option: bad code %d", code);
 200
 201         if (emit_commas)
 202                 comma = ',';
 203         else
 204                 comma = ' ';
 205
 206         /* Figure out the size of the data. */
 207         for (i = 0; dhcp_options[code].format[i]; i++) {
 208                 if (!numhunk) {
 209                         warning("%s: Excess information in format string: %s",
 210                             dhcp_options[code].name,
 211                             &(dhcp_options[code].format[i]));
 212                         break;
 213                 }
 214                 numelem++;
 215                 fmtbuf[i] = dhcp_options[code].format[i];
 216                 switch (dhcp_options[code].format[i]) {
 217                 case 'A':
 218                         --numelem;
 219                         fmtbuf[i] = 0;
 220                         numhunk = 0;
 221                         if (hunksize == 0) {
 222                                 warning("%s: no size indicator before A"
 223                                     " in format string: %s",
 224                                     dhcp_options[code].name,
 225                                     dhcp_options[code].format);
 226                                 return ("<fmt error>");
 227                         }
 228                         break;
 229                 case 'X':
 230                         for (k = 0; k < len; k++)
 231                                 if (!isascii(data[k]) ||
 232                                     !isprint(data[k]))
 233                                         break;
 234                         if (k == len) {
 235                                 fmtbuf[i] = 't';
 236                                 numhunk = -2;
 237                         } else {
 238                                 fmtbuf[i] = 'x';
 239                                 hunksize++;
 240                                 comma = ':';
 241                                 numhunk = 0;
 242                         }
 243                         fmtbuf[i + 1] = 0;
 244                         break;
 245                 case 't':
 246                         fmtbuf[i] = 't';
 247                         fmtbuf[i + 1] = 0;
 248                         numhunk = -2;
 249                         break;
 250                 case 'I':
 251                 case 'l':
 252                 case 'L':
 253                         hunksize += 4;
 254                         break;
 255                 case 's':
 256                 case 'S':
 257                         hunksize += 2;
 258                         break;
 259                 case 'b':
 260                 case 'B':
 261                 case 'f':
 262                         hunksize++;
 263                         break;
 264                 case 'e':
 265                         break;
 266                 default:
 267                         warning("%s: garbage in format string: %s",
 268                             dhcp_options[code].name,
 269                             &(dhcp_options[code].format[i]));
 270                         break;
 271                 }
 272         }
 273
 274         /* Check for too few bytes... */
 275         if (hunksize > len) {
 276                 warning("%s: expecting at least %d bytes; got %d",
 277                     dhcp_options[code].name, hunksize, len);
 278                 return ("<error>");
 279         }
 280         /* Check for too many bytes... */
 281         if (numhunk == -1 && hunksize < len)
 282                 warning("%s: %d extra bytes",
 283                     dhcp_options[code].name, len - hunksize);
 284
 285         /* If this is an array, compute its size. */
 286         if (!numhunk)
 287                 numhunk = len / hunksize;
 288         /* See if we got an exact number of hunks. */
 289         if (numhunk > 0 && numhunk * hunksize < len)
 290                 warning("%s: %d extra bytes at end of array",
 291                     dhcp_options[code].name, len - numhunk * hunksize);
 292
 293         /* A one-hunk array prints the same as a single hunk. */
 294         if (numhunk < 0)
 295                 numhunk = 1;
 296
 297         /* Cycle through the array (or hunk) printing the data. */
 298         for (i = 0; i < numhunk; i++) {
 299                 for (j = 0; j < numelem; j++) {
 300                         int opcount;
 301                         size_t oplen;
 302                         switch (fmtbuf[j]) {
 303                         case 't':
 304                                 if (emit_quotes) {
 305                                         *op++ = '"';
 306                                         opleft--;
 307                                 }
 308                                 for (; dp < data + len; dp++) {
 309                                         if (!isascii(*dp) ||
 310                                             !isprint(*dp)) {
 311                                                 if (dp + 1 != data + len ||
 312                                                     *dp != 0) {
 313                                                         size_t oplen;
 314                                                         snprintf(op, opleft,
 315                                                             "\\%03o", *dp);
 316                                                         oplen = strlen(op);
 317                                                         op += oplen;
 318                                                         opleft -= oplen;
 319                                                 }
 320                                         } else if (*dp == '"' ||
 321                                             *dp == '\'' ||
 322                                             *dp == '$' ||
 323                                             *dp == '`' ||
 324                                             *dp == '\\') {
 325                                                 *op++ = '\\';
 326                                                 *op++ = *dp;
 327                                                 opleft -= 2;
 328                                         } else {
 329                                                 *op++ = *dp;
 330                                                 opleft--;
 331                                         }
 332                                 }
 333                                 if (emit_quotes) {
 334                                         *op++ = '"';
 335                                         opleft--;
 336                                 }
 337
 338                                 *op = 0;
 339                                 break;
 340                         case 'I':
 341                                 foo.s_addr = htonl(getULong(dp));
 342                                 opcount = strlcpy(op, inet_ntoa(foo), opleft);
 343                                 if (opcount >= opleft)
 344                                         goto toobig;
 345                                 opleft -= opcount;
 346                                 dp += 4;
 347                                 break;
 348                         case 'l':
 349                                 opcount = snprintf(op, opleft, "%ld",
 350                                     (long)getLong(dp));
 351                                 if (opcount >= opleft || opcount == -1)
 352                                         goto toobig;
 353                                 opleft -= opcount;
 354                                 dp += 4;
 355                                 break;
 356                         case 'L':
 357                                 opcount = snprintf(op, opleft, "%ld",
 358                                     (unsigned long)getULong(dp));
 359                                 if (opcount >= opleft || opcount == -1)
 360                                         goto toobig;
 361                                 opleft -= opcount;
 362                                 dp += 4;
 363                                 break;
 364                         case 's':
 365                                 opcount = snprintf(op, opleft, "%d",
 366                                     getShort(dp));
 367                                 if (opcount >= opleft || opcount == -1)
 368                                         goto toobig;
 369                                 opleft -= opcount;
 370                                 dp += 2;
 371                                 break;
 372                         case 'S':
 373                                 opcount = snprintf(op, opleft, "%d",
 374                                     getUShort(dp));
 375                                 if (opcount >= opleft || opcount == -1)
 376                                         goto toobig;
 377                                 opleft -= opcount;
 378                                 dp += 2;
 379                                 break;
 380                         case 'b':
 381                                 opcount = snprintf(op, opleft, "%d",
 382                                     *(char *)dp++);
 383                                 if (opcount >= opleft || opcount == -1)
 384                                         goto toobig;
 385                                 opleft -= opcount;
 386                                 break;
 387                         case 'B':
 388                                 opcount = snprintf(op, opleft, "%d", *dp++);
 389                                 if (opcount >= opleft || opcount == -1)
 390                                         goto toobig;
 391                                 opleft -= opcount;
 392                                 break;
 393                         case 'x':
 394                                 opcount = snprintf(op, opleft, "%x", *dp++);
 395                                 if (opcount >= opleft || opcount == -1)
 396                                         goto toobig;
 397                                 opleft -= opcount;
 398                                 break;
 399                         case 'f':
 400                                 opcount = strlcpy(op,
 401                                     *dp++ ? "true" : "false", opleft);
 402                                 if (opcount >= opleft)
 403                                         goto toobig;
 404                                 opleft -= opcount;
 405                                 break;
 406                         default:
 407                                 warning("Unexpected format code %c", fmtbuf[j]);
 408                         }
 409                         oplen = strlen(op);
 410                         op += oplen;
 411                         opleft -= oplen;
 412                         if (opleft < 1)
 413                                 goto toobig;
 414                         if (j + 1 < numelem && comma != ':') {
 415                                 *op++ = ' ';
 416                                 opleft--;
 417                         }
 418                 }
 419                 if (i + 1 < numhunk) {
 420                         *op++ = comma;
 421                         opleft--;
 422                 }
 423                 if (opleft < 1)
 424                         goto toobig;
 425
 426         }
 427         return (optbuf);
 428  toobig:
 429         warning("dhcp option too large");
 430         return ("<error>");
 431 }
 432
 433 void
 434 do_packet(int len, unsigned int from_port, struct iaddr from,
 435     struct hardware *hfrom)
 436 {
 437         struct dhcp_packet *packet = &client->packet;
 438         struct option_data options[256];
 439         struct iaddrlist *ap;
 440         void (*handler)(struct iaddr, struct option_data *);
 441         char *type;
 442         int i, options_valid = 1;
 443
 444         if (packet->hlen > sizeof(packet->chaddr)) {
 445                 note("Discarding packet with invalid hlen.");
 446                 return;
 447         }
 448
 449         /*
 450          * Silently drop the packet if the client hardware address in the
 451          * packet is not the hardware address of the interface being managed.
 452          */
 453         if ((ifi->hw_address.hlen != packet->hlen) ||
 454             (memcmp(ifi->hw_address.haddr, packet->chaddr, packet->hlen)))
 455                 return;
 456
 457         memset(options, 0, sizeof(options));
 458
 459         if (memcmp(&packet->options, DHCP_OPTIONS_COOKIE, 4) == 0) {
 460                 /* Parse the BOOTP/DHCP options field. */
 461                 options_valid = parse_option_buffer(options,
 462                     &packet->options[4], sizeof(packet->options) - 4);
 463
 464                 /* Only DHCP packets have overload areas for options. */
 465                 if (options_valid &&
 466                     options[DHO_DHCP_MESSAGE_TYPE].data &&
 467                     options[DHO_DHCP_OPTION_OVERLOAD].data) {
 468                         if (options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 1)
 469                                 options_valid = parse_option_buffer(options,
 470                                     (unsigned char *)packet->file,
 471                                     sizeof(packet->file));
 472                         if (options_valid &&
 473                             options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 2)
 474                                 options_valid = parse_option_buffer(options,
 475                                     (unsigned char *)packet->sname,
 476                                     sizeof(packet->sname));
 477                 }
 478         }
 479
 480         type = "";
 481         handler = NULL;
 482
 483         if (options[DHO_DHCP_MESSAGE_TYPE].data) {
 484                 /* Always try a DHCP packet, even if a bad option was seen. */
 485                 switch (options[DHO_DHCP_MESSAGE_TYPE].data[0]) {
 486                 case DHCPOFFER:
 487                         handler = dhcpoffer;
 488                         type = "DHCPOFFER";
 489                         break;
 490                 case DHCPNAK:
 491                         handler = dhcpnak;
 492                         type = "DHCPNACK";
 493                         break;
 494                 case DHCPACK:
 495                         handler = dhcpack;
 496                         type = "DHCPACK";
 497                         break;
 498                 default:
 499                         break;
 500                 }
 501         } else if (options_valid && packet->op == BOOTREPLY) {
 502                 handler = dhcpoffer;
 503                 type = "BOOTREPLY";
 504         }
 505
 506         if (handler && client->xid == client->packet.xid) {
 507                 if (hfrom->hlen == 6)
 508                         note("%s from %s (%s)", type, piaddr(from),
 509                             ether_ntoa((struct ether_addr *)hfrom->haddr));
 510                 else
 511                         note("%s from %s", type, piaddr(from));
 512         } else
 513                 handler = NULL;
 514
 515         for (ap = config->reject_list; ap && handler; ap = ap->next)
 516                 if (addr_eq(from, ap->addr)) {
 517                         note("%s from %s rejected.", type, piaddr(from));
 518                         handler = NULL;
 519                 }
 520
 521         if (handler)
 522                 (*handler)(from, options);
 523
 524         for (i = 0; i < 256; i++)
 525                 if (options[i].len && options[i].data)
 526                         free(options[i].data);
 527 }