1 /*- 2 * Copyright (c) 2003 Mike Frantzen <frantzen@w4g.org> 3 * 4 * Permission to use, copy, modify, and distribute this software for any 5 * purpose with or without fee is hereby granted, provided that the above 6 * copyright notice and this permission notice appear in all copies. 7 * 8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 15 * 16 * $OpenBSD: pf_osfp.c,v 1.14 2008/06/12 18:17:01 henning Exp $ 17 */ 18 19 #include <sys/cdefs.h> 20 __FBSDID("$FreeBSD$"); 21 22 #include <sys/param.h> 23 #include <sys/kernel.h> 24 #include <sys/lock.h> 25 #include <sys/mbuf.h> 26 #include <sys/rwlock.h> 27 #include <sys/socket.h> 28 29 #include <netinet/in.h> 30 #include <netinet/ip.h> 31 #include <netinet/tcp.h> 32 33 #include <net/if.h> 34 #include <net/vnet.h> 35 #include <net/pfvar.h> 36 37 #include <netinet/ip6.h> 38 39 static MALLOC_DEFINE(M_PFOSFP, "pf_osfp", "pf(4) operating system fingerprints"); 40 #define DPFPRINTF(format, x...) \ 41 if (V_pf_status.debug >= PF_DEBUG_NOISY) \ 42 printf(format , ##x) 43 44 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint); 45 static VNET_DEFINE(struct pf_osfp_list, pf_osfp_list) = 46 SLIST_HEAD_INITIALIZER(); 47 #define V_pf_osfp_list VNET(pf_osfp_list) 48 49 static struct pf_osfp_enlist *pf_osfp_fingerprint_hdr(const struct ip *, 50 const struct ip6_hdr *, 51 const struct tcphdr *); 52 static struct pf_os_fingerprint *pf_osfp_find(struct pf_osfp_list *, 53 struct pf_os_fingerprint *, u_int8_t); 54 static struct pf_os_fingerprint *pf_osfp_find_exact(struct pf_osfp_list *, 55 struct pf_os_fingerprint *); 56 static void pf_osfp_insert(struct pf_osfp_list *, 57 struct pf_os_fingerprint *); 58 #ifdef PFDEBUG 59 static struct pf_os_fingerprint *pf_osfp_validate(void); 60 #endif 61 62 /* 63 * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only) 64 * Returns the list of possible OSes. 65 */ 66 struct pf_osfp_enlist * 67 pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off, 68 const struct tcphdr *tcp) 69 { 70 struct ip *ip; 71 struct ip6_hdr *ip6; 72 char hdr[60]; 73 74 if ((pd->af != PF_INET && pd->af != PF_INET6) || 75 pd->proto != IPPROTO_TCP || (tcp->th_off << 2) < sizeof(*tcp)) 76 return (NULL); 77 78 if (pd->af == PF_INET) { 79 ip = mtod(m, struct ip *); 80 ip6 = (struct ip6_hdr *)NULL; 81 } else { 82 ip = (struct ip *)NULL; 83 ip6 = mtod(m, struct ip6_hdr *); 84 } 85 if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL, 86 pd->af)) return (NULL); 87 88 return (pf_osfp_fingerprint_hdr(ip, ip6, (struct tcphdr *)hdr)); 89 } 90 91 static struct pf_osfp_enlist * 92 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct ip6_hdr *ip6, const struct tcphdr *tcp) 93 { 94 struct pf_os_fingerprint fp, *fpresult; 95 int cnt, optlen = 0; 96 const u_int8_t *optp; 97 char srcname[128]; 98 99 if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN) 100 return (NULL); 101 if (ip) { 102 if ((ip->ip_off & htons(IP_OFFMASK)) != 0) 103 return (NULL); 104 } 105 106 memset(&fp, 0, sizeof(fp)); 107 108 if (ip) { 109 fp.fp_psize = ntohs(ip->ip_len); 110 fp.fp_ttl = ip->ip_ttl; 111 if (ip->ip_off & htons(IP_DF)) 112 fp.fp_flags |= PF_OSFP_DF; 113 strlcpy(srcname, inet_ntoa(ip->ip_src), sizeof(srcname)); 114 } 115 #ifdef INET6 116 else if (ip6) { 117 /* jumbo payload? */ 118 fp.fp_psize = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen); 119 fp.fp_ttl = ip6->ip6_hlim; 120 fp.fp_flags |= PF_OSFP_DF; 121 fp.fp_flags |= PF_OSFP_INET6; 122 strlcpy(srcname, ip6_sprintf((struct in6_addr *)&ip6->ip6_src), 123 sizeof(srcname)); 124 } 125 #endif 126 else 127 return (NULL); 128 fp.fp_wsize = ntohs(tcp->th_win); 129 130 131 cnt = (tcp->th_off << 2) - sizeof(*tcp); 132 optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp)); 133 for (; cnt > 0; cnt -= optlen, optp += optlen) { 134 if (*optp == TCPOPT_EOL) 135 break; 136 137 fp.fp_optcnt++; 138 if (*optp == TCPOPT_NOP) { 139 fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) | 140 PF_OSFP_TCPOPT_NOP; 141 optlen = 1; 142 } else { 143 if (cnt < 2) 144 return (NULL); 145 optlen = optp[1]; 146 if (optlen > cnt || optlen < 2) 147 return (NULL); 148 switch (*optp) { 149 case TCPOPT_MAXSEG: 150 if (optlen >= TCPOLEN_MAXSEG) 151 memcpy(&fp.fp_mss, &optp[2], 152 sizeof(fp.fp_mss)); 153 fp.fp_tcpopts = (fp.fp_tcpopts << 154 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS; 155 NTOHS(fp.fp_mss); 156 break; 157 case TCPOPT_WINDOW: 158 if (optlen >= TCPOLEN_WINDOW) 159 memcpy(&fp.fp_wscale, &optp[2], 160 sizeof(fp.fp_wscale)); 161 NTOHS(fp.fp_wscale); 162 fp.fp_tcpopts = (fp.fp_tcpopts << 163 PF_OSFP_TCPOPT_BITS) | 164 PF_OSFP_TCPOPT_WSCALE; 165 break; 166 case TCPOPT_SACK_PERMITTED: 167 fp.fp_tcpopts = (fp.fp_tcpopts << 168 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK; 169 break; 170 case TCPOPT_TIMESTAMP: 171 if (optlen >= TCPOLEN_TIMESTAMP) { 172 u_int32_t ts; 173 memcpy(&ts, &optp[2], sizeof(ts)); 174 if (ts == 0) 175 fp.fp_flags |= PF_OSFP_TS0; 176 177 } 178 fp.fp_tcpopts = (fp.fp_tcpopts << 179 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS; 180 break; 181 default: 182 return (NULL); 183 } 184 } 185 optlen = MAX(optlen, 1); /* paranoia */ 186 } 187 188 DPFPRINTF("fingerprinted %s:%d %d:%d:%d:%d:%llx (%d) " 189 "(TS=%s,M=%s%d,W=%s%d)\n", 190 srcname, ntohs(tcp->th_sport), 191 fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0, 192 fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt, 193 (fp.fp_flags & PF_OSFP_TS0) ? "0" : "", 194 (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" : 195 (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "", 196 fp.fp_mss, 197 (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" : 198 (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "", 199 fp.fp_wscale); 200 201 if ((fpresult = pf_osfp_find(&V_pf_osfp_list, &fp, 202 PF_OSFP_MAXTTL_OFFSET))) 203 return (&fpresult->fp_oses); 204 return (NULL); 205 } 206 207 /* Match a fingerprint ID against a list of OSes */ 208 int 209 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os) 210 { 211 struct pf_osfp_entry *entry; 212 int os_class, os_version, os_subtype; 213 int en_class, en_version, en_subtype; 214 215 if (os == PF_OSFP_ANY) 216 return (1); 217 if (list == NULL) { 218 DPFPRINTF("osfp no match against %x\n", os); 219 return (os == PF_OSFP_UNKNOWN); 220 } 221 PF_OSFP_UNPACK(os, os_class, os_version, os_subtype); 222 SLIST_FOREACH(entry, list, fp_entry) { 223 PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype); 224 if ((os_class == PF_OSFP_ANY || en_class == os_class) && 225 (os_version == PF_OSFP_ANY || en_version == os_version) && 226 (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) { 227 DPFPRINTF("osfp matched %s %s %s %x==%x\n", 228 entry->fp_class_nm, entry->fp_version_nm, 229 entry->fp_subtype_nm, os, entry->fp_os); 230 return (1); 231 } 232 } 233 DPFPRINTF("fingerprint 0x%x didn't match\n", os); 234 return (0); 235 } 236 237 /* Flush the fingerprint list */ 238 void 239 pf_osfp_flush(void) 240 { 241 struct pf_os_fingerprint *fp; 242 struct pf_osfp_entry *entry; 243 244 while ((fp = SLIST_FIRST(&V_pf_osfp_list))) { 245 SLIST_REMOVE_HEAD(&V_pf_osfp_list, fp_next); 246 while ((entry = SLIST_FIRST(&fp->fp_oses))) { 247 SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry); 248 free(entry, M_PFOSFP); 249 } 250 free(fp, M_PFOSFP); 251 } 252 } 253 254 255 /* Add a fingerprint */ 256 int 257 pf_osfp_add(struct pf_osfp_ioctl *fpioc) 258 { 259 struct pf_os_fingerprint *fp, fpadd; 260 struct pf_osfp_entry *entry; 261 262 PF_RULES_WASSERT(); 263 264 memset(&fpadd, 0, sizeof(fpadd)); 265 fpadd.fp_tcpopts = fpioc->fp_tcpopts; 266 fpadd.fp_wsize = fpioc->fp_wsize; 267 fpadd.fp_psize = fpioc->fp_psize; 268 fpadd.fp_mss = fpioc->fp_mss; 269 fpadd.fp_flags = fpioc->fp_flags; 270 fpadd.fp_optcnt = fpioc->fp_optcnt; 271 fpadd.fp_wscale = fpioc->fp_wscale; 272 fpadd.fp_ttl = fpioc->fp_ttl; 273 274 #if 0 /* XXX RYAN wants to fix logging */ 275 DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d " 276 "(TS=%s,M=%s%d,W=%s%d) %x\n", 277 fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm, 278 fpioc->fp_os.fp_subtype_nm, 279 (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" : 280 (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" : 281 (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" : 282 (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "", 283 fpadd.fp_wsize, 284 fpadd.fp_ttl, 285 (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0, 286 (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" : 287 (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "", 288 fpadd.fp_psize, 289 (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt, 290 (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "", 291 (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" : 292 (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "", 293 fpadd.fp_mss, 294 (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" : 295 (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "", 296 fpadd.fp_wscale, 297 fpioc->fp_os.fp_os); 298 #endif 299 300 if ((fp = pf_osfp_find_exact(&V_pf_osfp_list, &fpadd))) { 301 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) { 302 if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os)) 303 return (EEXIST); 304 } 305 if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT)) 306 == NULL) 307 return (ENOMEM); 308 } else { 309 if ((fp = malloc(sizeof(*fp), M_PFOSFP, M_ZERO | M_NOWAIT)) 310 == NULL) 311 return (ENOMEM); 312 fp->fp_tcpopts = fpioc->fp_tcpopts; 313 fp->fp_wsize = fpioc->fp_wsize; 314 fp->fp_psize = fpioc->fp_psize; 315 fp->fp_mss = fpioc->fp_mss; 316 fp->fp_flags = fpioc->fp_flags; 317 fp->fp_optcnt = fpioc->fp_optcnt; 318 fp->fp_wscale = fpioc->fp_wscale; 319 fp->fp_ttl = fpioc->fp_ttl; 320 SLIST_INIT(&fp->fp_oses); 321 if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT)) 322 == NULL) { 323 free(fp, M_PFOSFP); 324 return (ENOMEM); 325 } 326 pf_osfp_insert(&V_pf_osfp_list, fp); 327 } 328 memcpy(entry, &fpioc->fp_os, sizeof(*entry)); 329 330 /* Make sure the strings are NUL terminated */ 331 entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0'; 332 entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0'; 333 entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0'; 334 335 SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry); 336 337 #ifdef PFDEBUG 338 if ((fp = pf_osfp_validate())) 339 printf("Invalid fingerprint list\n"); 340 #endif /* PFDEBUG */ 341 return (0); 342 } 343 344 345 /* Find a fingerprint in the list */ 346 static struct pf_os_fingerprint * 347 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find, 348 u_int8_t ttldiff) 349 { 350 struct pf_os_fingerprint *f; 351 352 #define MATCH_INT(_MOD, _DC, _field) \ 353 if ((f->fp_flags & _DC) == 0) { \ 354 if ((f->fp_flags & _MOD) == 0) { \ 355 if (f->_field != find->_field) \ 356 continue; \ 357 } else { \ 358 if (f->_field == 0 || find->_field % f->_field) \ 359 continue; \ 360 } \ 361 } 362 363 SLIST_FOREACH(f, list, fp_next) { 364 if (f->fp_tcpopts != find->fp_tcpopts || 365 f->fp_optcnt != find->fp_optcnt || 366 f->fp_ttl < find->fp_ttl || 367 f->fp_ttl - find->fp_ttl > ttldiff || 368 (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) != 369 (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0))) 370 continue; 371 372 MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize) 373 MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss) 374 MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale) 375 if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) { 376 if (f->fp_flags & PF_OSFP_WSIZE_MSS) { 377 if (find->fp_mss == 0) 378 continue; 379 380 /* 381 * Some "smart" NAT devices and DSL routers will tweak the MSS size and 382 * will set it to whatever is suitable for the link type. 383 */ 384 #define SMART_MSS 1460 385 if ((find->fp_wsize % find->fp_mss || 386 find->fp_wsize / find->fp_mss != 387 f->fp_wsize) && 388 (find->fp_wsize % SMART_MSS || 389 find->fp_wsize / SMART_MSS != 390 f->fp_wsize)) 391 continue; 392 } else if (f->fp_flags & PF_OSFP_WSIZE_MTU) { 393 if (find->fp_mss == 0) 394 continue; 395 396 #define MTUOFF (sizeof(struct ip) + sizeof(struct tcphdr)) 397 #define SMART_MTU (SMART_MSS + MTUOFF) 398 if ((find->fp_wsize % (find->fp_mss + MTUOFF) || 399 find->fp_wsize / (find->fp_mss + MTUOFF) != 400 f->fp_wsize) && 401 (find->fp_wsize % SMART_MTU || 402 find->fp_wsize / SMART_MTU != 403 f->fp_wsize)) 404 continue; 405 } else if (f->fp_flags & PF_OSFP_WSIZE_MOD) { 406 if (f->fp_wsize == 0 || find->fp_wsize % 407 f->fp_wsize) 408 continue; 409 } else { 410 if (f->fp_wsize != find->fp_wsize) 411 continue; 412 } 413 } 414 return (f); 415 } 416 417 return (NULL); 418 } 419 420 /* Find an exact fingerprint in the list */ 421 static struct pf_os_fingerprint * 422 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find) 423 { 424 struct pf_os_fingerprint *f; 425 426 SLIST_FOREACH(f, list, fp_next) { 427 if (f->fp_tcpopts == find->fp_tcpopts && 428 f->fp_wsize == find->fp_wsize && 429 f->fp_psize == find->fp_psize && 430 f->fp_mss == find->fp_mss && 431 f->fp_flags == find->fp_flags && 432 f->fp_optcnt == find->fp_optcnt && 433 f->fp_wscale == find->fp_wscale && 434 f->fp_ttl == find->fp_ttl) 435 return (f); 436 } 437 438 return (NULL); 439 } 440 441 /* Insert a fingerprint into the list */ 442 static void 443 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins) 444 { 445 struct pf_os_fingerprint *f, *prev = NULL; 446 447 /* XXX need to go semi tree based. can key on tcp options */ 448 449 SLIST_FOREACH(f, list, fp_next) 450 prev = f; 451 if (prev) 452 SLIST_INSERT_AFTER(prev, ins, fp_next); 453 else 454 SLIST_INSERT_HEAD(list, ins, fp_next); 455 } 456 457 /* Fill a fingerprint by its number (from an ioctl) */ 458 int 459 pf_osfp_get(struct pf_osfp_ioctl *fpioc) 460 { 461 struct pf_os_fingerprint *fp; 462 struct pf_osfp_entry *entry; 463 int num = fpioc->fp_getnum; 464 int i = 0; 465 466 467 memset(fpioc, 0, sizeof(*fpioc)); 468 SLIST_FOREACH(fp, &V_pf_osfp_list, fp_next) { 469 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) { 470 if (i++ == num) { 471 fpioc->fp_mss = fp->fp_mss; 472 fpioc->fp_wsize = fp->fp_wsize; 473 fpioc->fp_flags = fp->fp_flags; 474 fpioc->fp_psize = fp->fp_psize; 475 fpioc->fp_ttl = fp->fp_ttl; 476 fpioc->fp_wscale = fp->fp_wscale; 477 fpioc->fp_getnum = num; 478 memcpy(&fpioc->fp_os, entry, 479 sizeof(fpioc->fp_os)); 480 return (0); 481 } 482 } 483 } 484 485 return (EBUSY); 486 } 487 488 489 #ifdef PFDEBUG 490 /* Validate that each signature is reachable */ 491 static struct pf_os_fingerprint * 492 pf_osfp_validate(void) 493 { 494 struct pf_os_fingerprint *f, *f2, find; 495 496 SLIST_FOREACH(f, &V_pf_osfp_list, fp_next) { 497 memcpy(&find, f, sizeof(find)); 498 499 /* We do a few MSS/th_win percolations to make things unique */ 500 if (find.fp_mss == 0) 501 find.fp_mss = 128; 502 if (f->fp_flags & PF_OSFP_WSIZE_MSS) 503 find.fp_wsize *= find.fp_mss; 504 else if (f->fp_flags & PF_OSFP_WSIZE_MTU) 505 find.fp_wsize *= (find.fp_mss + 40); 506 else if (f->fp_flags & PF_OSFP_WSIZE_MOD) 507 find.fp_wsize *= 2; 508 if (f != (f2 = pf_osfp_find(&V_pf_osfp_list, &find, 0))) { 509 if (f2) 510 printf("Found \"%s %s %s\" instead of " 511 "\"%s %s %s\"\n", 512 SLIST_FIRST(&f2->fp_oses)->fp_class_nm, 513 SLIST_FIRST(&f2->fp_oses)->fp_version_nm, 514 SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm, 515 SLIST_FIRST(&f->fp_oses)->fp_class_nm, 516 SLIST_FIRST(&f->fp_oses)->fp_version_nm, 517 SLIST_FIRST(&f->fp_oses)->fp_subtype_nm); 518 else 519 printf("Couldn't find \"%s %s %s\"\n", 520 SLIST_FIRST(&f->fp_oses)->fp_class_nm, 521 SLIST_FIRST(&f->fp_oses)->fp_version_nm, 522 SLIST_FIRST(&f->fp_oses)->fp_subtype_nm); 523 return (f); 524 } 525 } 526 return (NULL); 527 } 528 #endif /* PFDEBUG */ 529