| 1 | /* $OpenBSD: src/sbin/dhclient/options.c,v 1.40 2012/06/26 14:36:11 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 | /* |
| 91 | * Strip trailing NULs from ascii ('t') options. They |
| 92 | * will be treated as DHO_PAD options. i.e. ignored. RFC 2132 |
| 93 | * says "Options containing NVT ASCII data SHOULD NOT include |
| 94 | * a trailing NULL; however, the receiver of such options |
| 95 | * MUST be prepared to delete trailing nulls if they exist." |
| 96 | */ |
| 97 | if (dhcp_options[code].format[0] == 't') { |
| 98 | for (len = s[1]; len > 0 && s[len + 1] == '\0'; len--) |
| 99 | ; |
| 100 | } |
| 101 | |
| 102 | /* |
| 103 | * If we haven't seen this option before, just make |
| 104 | * space for it and copy it there. |
| 105 | */ |
| 106 | if (!options[code].data) { |
| 107 | if (!(t = calloc(1, len + 1))) |
| 108 | error("Can't allocate storage for option %s.", |
| 109 | dhcp_options[code].name); |
| 110 | /* |
| 111 | * Copy and NUL-terminate the option (in case |
| 112 | * it's an ASCII string). |
| 113 | */ |
| 114 | memcpy(t, &s[2], len); |
| 115 | t[len] = 0; |
| 116 | options[code].len = len; |
| 117 | options[code].data = t; |
| 118 | } else { |
| 119 | /* |
| 120 | * If it's a repeat, concatenate it to whatever |
| 121 | * we last saw. This is really only required |
| 122 | * for clients, but what the heck... |
| 123 | */ |
| 124 | t = calloc(1, len + options[code].len + 1); |
| 125 | if (!t) |
| 126 | error("Can't expand storage for option %s.", |
| 127 | dhcp_options[code].name); |
| 128 | memcpy(t, options[code].data, options[code].len); |
| 129 | memcpy(t + options[code].len, &s[2], len); |
| 130 | options[code].len += len; |
| 131 | t[options[code].len] = 0; |
| 132 | free(options[code].data); |
| 133 | options[code].data = t; |
| 134 | } |
| 135 | s += len + 2; |
| 136 | } |
| 137 | |
| 138 | return (1); |
| 139 | } |
| 140 | |
| 141 | /* |
| 142 | * Copy as many options as fit in buflen bytes of buf. Return the |
| 143 | * offset of the start of the last option copied. A caller can check |
| 144 | * to see if it's DHO_END to decide if all the options were copied. |
| 145 | */ |
| 146 | int |
| 147 | cons_options(struct option_data *options) |
| 148 | { |
| 149 | unsigned char *buf = client->packet.options; |
| 150 | int buflen = 576 - DHCP_FIXED_LEN; |
| 151 | int ix, incr, length, bufix, code, lastopt = -1; |
| 152 | |
| 153 | bzero(buf, buflen); |
| 154 | |
| 155 | memcpy(buf, DHCP_OPTIONS_COOKIE, 4); |
| 156 | if (options[DHO_DHCP_MESSAGE_TYPE].data) { |
| 157 | memcpy(&buf[4], DHCP_OPTIONS_MESSAGE_TYPE, 3); |
| 158 | buf[6] = options[DHO_DHCP_MESSAGE_TYPE].data[0]; |
| 159 | bufix = 7; |
| 160 | } else |
| 161 | bufix = 4; |
| 162 | |
| 163 | for (code = DHO_SUBNET_MASK; code < DHO_END; code++) { |
| 164 | if (!options[code].data || code == DHO_DHCP_MESSAGE_TYPE) |
| 165 | continue; |
| 166 | |
| 167 | length = options[code].len; |
| 168 | if (bufix + length + 2*((length+254)/255) >= buflen) |
| 169 | return (lastopt); |
| 170 | |
| 171 | lastopt = bufix; |
| 172 | ix = 0; |
| 173 | |
| 174 | while (length) { |
| 175 | incr = length > 255 ? 255 : length; |
| 176 | |
| 177 | buf[bufix++] = code; |
| 178 | buf[bufix++] = incr; |
| 179 | memcpy(buf + bufix, options[code].data + ix, incr); |
| 180 | |
| 181 | length -= incr; |
| 182 | ix += incr; |
| 183 | bufix += incr; |
| 184 | } |
| 185 | } |
| 186 | |
| 187 | if (bufix < buflen) { |
| 188 | buf[bufix] = DHO_END; |
| 189 | lastopt = bufix; |
| 190 | } |
| 191 | |
| 192 | return (lastopt); |
| 193 | } |
| 194 | |
| 195 | /* |
| 196 | * Format the specified option so that a human can easily read it. |
| 197 | */ |
| 198 | char * |
| 199 | pretty_print_option(unsigned int code, unsigned char *data, int len, |
| 200 | int emit_commas, int emit_quotes) |
| 201 | { |
| 202 | static char optbuf[32768]; /* XXX */ |
| 203 | int hunksize = 0, numhunk = -1, numelem = 0; |
| 204 | char fmtbuf[32], *op = optbuf; |
| 205 | int i, j, k, opleft = sizeof(optbuf); |
| 206 | unsigned char *dp = data; |
| 207 | struct in_addr foo; |
| 208 | char comma; |
| 209 | |
| 210 | /* Code should be between 0 and 255. */ |
| 211 | if (code > 255) |
| 212 | error("pretty_print_option: bad code %d", code); |
| 213 | |
| 214 | if (emit_commas) |
| 215 | comma = ','; |
| 216 | else |
| 217 | comma = ' '; |
| 218 | |
| 219 | /* Figure out the size of the data. */ |
| 220 | for (i = 0; dhcp_options[code].format[i]; i++) { |
| 221 | if (!numhunk) { |
| 222 | warning("%s: Excess information in format string: %s", |
| 223 | dhcp_options[code].name, |
| 224 | &(dhcp_options[code].format[i])); |
| 225 | break; |
| 226 | } |
| 227 | numelem++; |
| 228 | fmtbuf[i] = dhcp_options[code].format[i]; |
| 229 | switch (dhcp_options[code].format[i]) { |
| 230 | case 'A': |
| 231 | --numelem; |
| 232 | fmtbuf[i] = 0; |
| 233 | numhunk = 0; |
| 234 | if (hunksize == 0) { |
| 235 | warning("%s: no size indicator before A" |
| 236 | " in format string: %s", |
| 237 | dhcp_options[code].name, |
| 238 | dhcp_options[code].format); |
| 239 | return ("<fmt error>"); |
| 240 | } |
| 241 | break; |
| 242 | case 'X': |
| 243 | for (k = 0; k < len; k++) |
| 244 | if (!isascii(data[k]) || |
| 245 | !isprint(data[k])) |
| 246 | break; |
| 247 | if (k == len) { |
| 248 | fmtbuf[i] = 't'; |
| 249 | numhunk = -2; |
| 250 | } else { |
| 251 | fmtbuf[i] = 'x'; |
| 252 | hunksize++; |
| 253 | comma = ':'; |
| 254 | numhunk = 0; |
| 255 | } |
| 256 | fmtbuf[i + 1] = 0; |
| 257 | break; |
| 258 | case 't': |
| 259 | fmtbuf[i] = 't'; |
| 260 | fmtbuf[i + 1] = 0; |
| 261 | numhunk = -2; |
| 262 | break; |
| 263 | case 'I': |
| 264 | case 'l': |
| 265 | case 'L': |
| 266 | hunksize += 4; |
| 267 | break; |
| 268 | case 's': |
| 269 | case 'S': |
| 270 | hunksize += 2; |
| 271 | break; |
| 272 | case 'b': |
| 273 | case 'B': |
| 274 | case 'f': |
| 275 | hunksize++; |
| 276 | break; |
| 277 | case 'e': |
| 278 | break; |
| 279 | default: |
| 280 | warning("%s: garbage in format string: %s", |
| 281 | dhcp_options[code].name, |
| 282 | &(dhcp_options[code].format[i])); |
| 283 | break; |
| 284 | } |
| 285 | } |
| 286 | |
| 287 | /* Check for too few bytes... */ |
| 288 | if (hunksize > len) { |
| 289 | warning("%s: expecting at least %d bytes; got %d", |
| 290 | dhcp_options[code].name, hunksize, len); |
| 291 | return ("<error>"); |
| 292 | } |
| 293 | /* Check for too many bytes... */ |
| 294 | if (numhunk == -1 && hunksize < len) |
| 295 | warning("%s: %d extra bytes", |
| 296 | dhcp_options[code].name, len - hunksize); |
| 297 | |
| 298 | /* If this is an array, compute its size. */ |
| 299 | if (!numhunk) |
| 300 | numhunk = len / hunksize; |
| 301 | /* See if we got an exact number of hunks. */ |
| 302 | if (numhunk > 0 && numhunk * hunksize < len) |
| 303 | warning("%s: %d extra bytes at end of array", |
| 304 | dhcp_options[code].name, len - numhunk * hunksize); |
| 305 | |
| 306 | /* A one-hunk array prints the same as a single hunk. */ |
| 307 | if (numhunk < 0) |
| 308 | numhunk = 1; |
| 309 | |
| 310 | /* Cycle through the array (or hunk) printing the data. */ |
| 311 | for (i = 0; i < numhunk; i++) { |
| 312 | for (j = 0; j < numelem; j++) { |
| 313 | int opcount; |
| 314 | size_t oplen; |
| 315 | switch (fmtbuf[j]) { |
| 316 | case 't': |
| 317 | if (emit_quotes) { |
| 318 | *op++ = '"'; |
| 319 | opleft--; |
| 320 | } |
| 321 | for (; dp < data + len; dp++) { |
| 322 | if (!isascii(*dp) || |
| 323 | !isprint(*dp)) { |
| 324 | if (dp + 1 != data + len || |
| 325 | *dp != 0) { |
| 326 | size_t oplen; |
| 327 | snprintf(op, opleft, |
| 328 | "\\%03o", *dp); |
| 329 | oplen = strlen(op); |
| 330 | op += oplen; |
| 331 | opleft -= oplen; |
| 332 | } |
| 333 | } else if (*dp == '"' || |
| 334 | *dp == '\'' || |
| 335 | *dp == '$' || |
| 336 | *dp == '`' || |
| 337 | *dp == '\\') { |
| 338 | *op++ = '\\'; |
| 339 | *op++ = *dp; |
| 340 | opleft -= 2; |
| 341 | } else { |
| 342 | *op++ = *dp; |
| 343 | opleft--; |
| 344 | } |
| 345 | } |
| 346 | if (emit_quotes) { |
| 347 | *op++ = '"'; |
| 348 | opleft--; |
| 349 | } |
| 350 | |
| 351 | *op = 0; |
| 352 | break; |
| 353 | case 'I': |
| 354 | foo.s_addr = htonl(getULong(dp)); |
| 355 | opcount = strlcpy(op, inet_ntoa(foo), opleft); |
| 356 | if (opcount >= opleft) |
| 357 | goto toobig; |
| 358 | opleft -= opcount; |
| 359 | dp += 4; |
| 360 | break; |
| 361 | case 'l': |
| 362 | opcount = snprintf(op, opleft, "%ld", |
| 363 | (long)getLong(dp)); |
| 364 | if (opcount >= opleft || opcount == -1) |
| 365 | goto toobig; |
| 366 | opleft -= opcount; |
| 367 | dp += 4; |
| 368 | break; |
| 369 | case 'L': |
| 370 | opcount = snprintf(op, opleft, "%ld", |
| 371 | (unsigned long)getULong(dp)); |
| 372 | if (opcount >= opleft || opcount == -1) |
| 373 | goto toobig; |
| 374 | opleft -= opcount; |
| 375 | dp += 4; |
| 376 | break; |
| 377 | case 's': |
| 378 | opcount = snprintf(op, opleft, "%d", |
| 379 | getShort(dp)); |
| 380 | if (opcount >= opleft || opcount == -1) |
| 381 | goto toobig; |
| 382 | opleft -= opcount; |
| 383 | dp += 2; |
| 384 | break; |
| 385 | case 'S': |
| 386 | opcount = snprintf(op, opleft, "%d", |
| 387 | getUShort(dp)); |
| 388 | if (opcount >= opleft || opcount == -1) |
| 389 | goto toobig; |
| 390 | opleft -= opcount; |
| 391 | dp += 2; |
| 392 | break; |
| 393 | case 'b': |
| 394 | opcount = snprintf(op, opleft, "%d", |
| 395 | *(char *)dp++); |
| 396 | if (opcount >= opleft || opcount == -1) |
| 397 | goto toobig; |
| 398 | opleft -= opcount; |
| 399 | break; |
| 400 | case 'B': |
| 401 | opcount = snprintf(op, opleft, "%d", *dp++); |
| 402 | if (opcount >= opleft || opcount == -1) |
| 403 | goto toobig; |
| 404 | opleft -= opcount; |
| 405 | break; |
| 406 | case 'x': |
| 407 | opcount = snprintf(op, opleft, "%x", *dp++); |
| 408 | if (opcount >= opleft || opcount == -1) |
| 409 | goto toobig; |
| 410 | opleft -= opcount; |
| 411 | break; |
| 412 | case 'f': |
| 413 | opcount = strlcpy(op, |
| 414 | *dp++ ? "true" : "false", opleft); |
| 415 | if (opcount >= opleft) |
| 416 | goto toobig; |
| 417 | opleft -= opcount; |
| 418 | break; |
| 419 | default: |
| 420 | warning("Unexpected format code %c", fmtbuf[j]); |
| 421 | } |
| 422 | oplen = strlen(op); |
| 423 | op += oplen; |
| 424 | opleft -= oplen; |
| 425 | if (opleft < 1) |
| 426 | goto toobig; |
| 427 | if (j + 1 < numelem && comma != ':') { |
| 428 | *op++ = ' '; |
| 429 | opleft--; |
| 430 | } |
| 431 | } |
| 432 | if (i + 1 < numhunk) { |
| 433 | *op++ = comma; |
| 434 | opleft--; |
| 435 | } |
| 436 | if (opleft < 1) |
| 437 | goto toobig; |
| 438 | |
| 439 | } |
| 440 | return (optbuf); |
| 441 | toobig: |
| 442 | warning("dhcp option too large"); |
| 443 | return ("<error>"); |
| 444 | } |
| 445 | |
| 446 | void |
| 447 | do_packet(int len, unsigned int from_port, struct iaddr from, |
| 448 | struct hardware *hfrom) |
| 449 | { |
| 450 | struct dhcp_packet *packet = &client->packet; |
| 451 | struct option_data options[256]; |
| 452 | struct iaddrlist *ap; |
| 453 | void (*handler)(struct iaddr, struct option_data *); |
| 454 | char *type; |
| 455 | int i, options_valid = 1; |
| 456 | |
| 457 | if (packet->hlen > sizeof(packet->chaddr)) { |
| 458 | note("Discarding packet with invalid hlen."); |
| 459 | return; |
| 460 | } |
| 461 | |
| 462 | /* |
| 463 | * Silently drop the packet if the client hardware address in the |
| 464 | * packet is not the hardware address of the interface being managed. |
| 465 | */ |
| 466 | if ((ifi->hw_address.hlen != packet->hlen) || |
| 467 | (memcmp(ifi->hw_address.haddr, packet->chaddr, packet->hlen))) |
| 468 | return; |
| 469 | |
| 470 | memset(options, 0, sizeof(options)); |
| 471 | |
| 472 | if (memcmp(&packet->options, DHCP_OPTIONS_COOKIE, 4) == 0) { |
| 473 | /* Parse the BOOTP/DHCP options field. */ |
| 474 | options_valid = parse_option_buffer(options, |
| 475 | &packet->options[4], sizeof(packet->options) - 4); |
| 476 | |
| 477 | /* Only DHCP packets have overload areas for options. */ |
| 478 | if (options_valid && |
| 479 | options[DHO_DHCP_MESSAGE_TYPE].data && |
| 480 | options[DHO_DHCP_OPTION_OVERLOAD].data) { |
| 481 | if (options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 1) |
| 482 | options_valid = parse_option_buffer(options, |
| 483 | (unsigned char *)packet->file, |
| 484 | sizeof(packet->file)); |
| 485 | if (options_valid && |
| 486 | options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 2) |
| 487 | options_valid = parse_option_buffer(options, |
| 488 | (unsigned char *)packet->sname, |
| 489 | sizeof(packet->sname)); |
| 490 | } |
| 491 | } |
| 492 | |
| 493 | type = ""; |
| 494 | handler = NULL; |
| 495 | |
| 496 | if (options[DHO_DHCP_MESSAGE_TYPE].data) { |
| 497 | /* Always try a DHCP packet, even if a bad option was seen. */ |
| 498 | switch (options[DHO_DHCP_MESSAGE_TYPE].data[0]) { |
| 499 | case DHCPOFFER: |
| 500 | handler = dhcpoffer; |
| 501 | type = "DHCPOFFER"; |
| 502 | break; |
| 503 | case DHCPNAK: |
| 504 | handler = dhcpnak; |
| 505 | type = "DHCPNACK"; |
| 506 | break; |
| 507 | case DHCPACK: |
| 508 | handler = dhcpack; |
| 509 | type = "DHCPACK"; |
| 510 | break; |
| 511 | default: |
| 512 | break; |
| 513 | } |
| 514 | } else if (options_valid && packet->op == BOOTREPLY) { |
| 515 | handler = dhcpoffer; |
| 516 | type = "BOOTREPLY"; |
| 517 | } |
| 518 | |
| 519 | if (handler && client->xid == client->packet.xid) { |
| 520 | if (hfrom->hlen == 6) |
| 521 | note("%s from %s (%s)", type, piaddr(from), |
| 522 | ether_ntoa((struct ether_addr *)hfrom->haddr)); |
| 523 | else |
| 524 | note("%s from %s", type, piaddr(from)); |
| 525 | } else |
| 526 | handler = NULL; |
| 527 | |
| 528 | for (ap = config->reject_list; ap && handler; ap = ap->next) |
| 529 | if (addr_eq(from, ap->addr)) { |
| 530 | note("%s from %s rejected.", type, piaddr(from)); |
| 531 | handler = NULL; |
| 532 | } |
| 533 | |
| 534 | if (handler) |
| 535 | (*handler)(from, options); |
| 536 | |
| 537 | for (i = 0; i < 256; i++) |
| 538 | if (options[i].len && options[i].data) |
| 539 | free(options[i].data); |
| 540 | } |