1 /*- 2 * SPDX-License-Identifier: ISC 3 * 4 * Copyright (c) 2003 Mike Frantzen <frantzen@w4g.org> 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 * 18 * $OpenBSD: pf_osfp.c,v 1.14 2008/06/12 18:17:01 henning Exp $ 19 */ 20 21 #include <sys/cdefs.h> 22 #include "opt_inet6.h" 23 24 #include <sys/param.h> 25 #include <sys/kernel.h> 26 #include <sys/lock.h> 27 #include <sys/mbuf.h> 28 #include <sys/socket.h> 29 30 #include <netinet/in.h> 31 #include <netinet/ip.h> 32 #include <netinet/tcp.h> 33 34 #include <net/if.h> 35 #include <net/vnet.h> 36 #include <net/pfvar.h> 37 38 #ifdef INET6 39 #include <netinet/ip6.h> 40 #endif 41 42 static MALLOC_DEFINE(M_PFOSFP, "pf_osfp", "pf(4) operating system fingerprints"); 43 #define DPFPRINTF(format, x...) \ 44 if (V_pf_status.debug >= PF_DEBUG_NOISY) \ 45 printf(format , ##x) 46 47 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint); 48 VNET_DEFINE_STATIC(struct pf_osfp_list, pf_osfp_list) = 49 SLIST_HEAD_INITIALIZER(); 50 #define V_pf_osfp_list VNET(pf_osfp_list) 51 52 static struct pf_osfp_enlist *pf_osfp_fingerprint_hdr(const struct ip *, 53 const struct ip6_hdr *, 54 const struct tcphdr *); 55 static struct pf_os_fingerprint *pf_osfp_find(struct pf_osfp_list *, 56 struct pf_os_fingerprint *, u_int8_t); 57 static struct pf_os_fingerprint *pf_osfp_find_exact(struct pf_osfp_list *, 58 struct pf_os_fingerprint *); 59 static void pf_osfp_insert(struct pf_osfp_list *, 60 struct pf_os_fingerprint *); 61 #ifdef PFDEBUG 62 static struct pf_os_fingerprint *pf_osfp_validate(void); 63 #endif 64 65 /* 66 * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only) 67 * Returns the list of possible OSes. 68 */ 69 struct pf_osfp_enlist * 70 pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off, 71 const struct tcphdr *tcp) 72 { 73 struct ip *ip; 74 struct ip6_hdr *ip6; 75 char hdr[60]; 76 77 if ((pd->af != PF_INET && pd->af != PF_INET6) || 78 pd->proto != IPPROTO_TCP || (tcp->th_off << 2) < sizeof(*tcp)) 79 return (NULL); 80 81 if (pd->af == PF_INET) { 82 ip = mtod(m, struct ip *); 83 ip6 = (struct ip6_hdr *)NULL; 84 } else { 85 ip = (struct ip *)NULL; 86 ip6 = mtod(m, struct ip6_hdr *); 87 } 88 if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL, 89 pd->af)) return (NULL); 90 91 return (pf_osfp_fingerprint_hdr(ip, ip6, (struct tcphdr *)hdr)); 92 } 93 94 static struct pf_osfp_enlist * 95 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct ip6_hdr *ip6, const struct tcphdr *tcp) 96 { 97 struct pf_os_fingerprint fp, *fpresult; 98 int cnt, optlen = 0; 99 const u_int8_t *optp; 100 #ifdef INET6 101 char srcname[INET6_ADDRSTRLEN]; 102 #else 103 char srcname[INET_ADDRSTRLEN]; 104 #endif 105 106 if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN) 107 return (NULL); 108 if (ip) { 109 if ((ip->ip_off & htons(IP_OFFMASK)) != 0) 110 return (NULL); 111 } 112 113 memset(&fp, 0, sizeof(fp)); 114 115 if (ip) { 116 fp.fp_psize = ntohs(ip->ip_len); 117 fp.fp_ttl = ip->ip_ttl; 118 if (ip->ip_off & htons(IP_DF)) 119 fp.fp_flags |= PF_OSFP_DF; 120 inet_ntoa_r(ip->ip_src, srcname); 121 } 122 #ifdef INET6 123 else if (ip6) { 124 /* jumbo payload? */ 125 fp.fp_psize = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen); 126 fp.fp_ttl = ip6->ip6_hlim; 127 fp.fp_flags |= PF_OSFP_DF; 128 fp.fp_flags |= PF_OSFP_INET6; 129 ip6_sprintf(srcname, (const struct in6_addr *)&ip6->ip6_src); 130 } 131 #endif 132 else 133 return (NULL); 134 fp.fp_wsize = ntohs(tcp->th_win); 135 136 cnt = (tcp->th_off << 2) - sizeof(*tcp); 137 optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp)); 138 for (; cnt > 0; cnt -= optlen, optp += optlen) { 139 if (*optp == TCPOPT_EOL) 140 break; 141 142 fp.fp_optcnt++; 143 if (*optp == TCPOPT_NOP) { 144 fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) | 145 PF_OSFP_TCPOPT_NOP; 146 optlen = 1; 147 } else { 148 if (cnt < 2) 149 return (NULL); 150 optlen = optp[1]; 151 if (optlen > cnt || optlen < 2) 152 return (NULL); 153 switch (*optp) { 154 case TCPOPT_MAXSEG: 155 if (optlen >= TCPOLEN_MAXSEG) 156 memcpy(&fp.fp_mss, &optp[2], 157 sizeof(fp.fp_mss)); 158 fp.fp_tcpopts = (fp.fp_tcpopts << 159 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS; 160 NTOHS(fp.fp_mss); 161 break; 162 case TCPOPT_WINDOW: 163 if (optlen >= TCPOLEN_WINDOW) 164 memcpy(&fp.fp_wscale, &optp[2], 165 sizeof(fp.fp_wscale)); 166 NTOHS(fp.fp_wscale); 167 fp.fp_tcpopts = (fp.fp_tcpopts << 168 PF_OSFP_TCPOPT_BITS) | 169 PF_OSFP_TCPOPT_WSCALE; 170 break; 171 case TCPOPT_SACK_PERMITTED: 172 fp.fp_tcpopts = (fp.fp_tcpopts << 173 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK; 174 break; 175 case TCPOPT_TIMESTAMP: 176 if (optlen >= TCPOLEN_TIMESTAMP) { 177 u_int32_t ts; 178 memcpy(&ts, &optp[2], sizeof(ts)); 179 if (ts == 0) 180 fp.fp_flags |= PF_OSFP_TS0; 181 } 182 fp.fp_tcpopts = (fp.fp_tcpopts << 183 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS; 184 break; 185 default: 186 return (NULL); 187 } 188 } 189 optlen = MAX(optlen, 1); /* paranoia */ 190 } 191 192 DPFPRINTF("fingerprinted %s:%d %d:%d:%d:%d:%llx (%d) " 193 "(TS=%s,M=%s%d,W=%s%d)\n", 194 srcname, ntohs(tcp->th_sport), 195 fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0, 196 fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt, 197 (fp.fp_flags & PF_OSFP_TS0) ? "0" : "", 198 (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" : 199 (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "", 200 fp.fp_mss, 201 (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" : 202 (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "", 203 fp.fp_wscale); 204 205 if ((fpresult = pf_osfp_find(&V_pf_osfp_list, &fp, 206 PF_OSFP_MAXTTL_OFFSET))) 207 return (&fpresult->fp_oses); 208 return (NULL); 209 } 210 211 /* Match a fingerprint ID against a list of OSes */ 212 int 213 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os) 214 { 215 struct pf_osfp_entry *entry; 216 int os_class, os_version, os_subtype; 217 int en_class, en_version, en_subtype; 218 219 if (os == PF_OSFP_ANY) 220 return (1); 221 if (list == NULL) { 222 DPFPRINTF("osfp no match against %x\n", os); 223 return (os == PF_OSFP_UNKNOWN); 224 } 225 PF_OSFP_UNPACK(os, os_class, os_version, os_subtype); 226 SLIST_FOREACH(entry, list, fp_entry) { 227 PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype); 228 if ((os_class == PF_OSFP_ANY || en_class == os_class) && 229 (os_version == PF_OSFP_ANY || en_version == os_version) && 230 (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) { 231 DPFPRINTF("osfp matched %s %s %s %x==%x\n", 232 entry->fp_class_nm, entry->fp_version_nm, 233 entry->fp_subtype_nm, os, entry->fp_os); 234 return (1); 235 } 236 } 237 DPFPRINTF("fingerprint 0x%x didn't match\n", os); 238 return (0); 239 } 240 241 /* Flush the fingerprint list */ 242 void 243 pf_osfp_flush(void) 244 { 245 struct pf_os_fingerprint *fp; 246 struct pf_osfp_entry *entry; 247 248 while ((fp = SLIST_FIRST(&V_pf_osfp_list))) { 249 SLIST_REMOVE_HEAD(&V_pf_osfp_list, fp_next); 250 while ((entry = SLIST_FIRST(&fp->fp_oses))) { 251 SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry); 252 free(entry, M_PFOSFP); 253 } 254 free(fp, M_PFOSFP); 255 } 256 } 257 258 /* Add a fingerprint */ 259 int 260 pf_osfp_add(struct pf_osfp_ioctl *fpioc) 261 { 262 struct pf_os_fingerprint *fp, fpadd; 263 struct pf_osfp_entry *entry; 264 265 PF_RULES_WASSERT(); 266 267 memset(&fpadd, 0, sizeof(fpadd)); 268 fpadd.fp_tcpopts = fpioc->fp_tcpopts; 269 fpadd.fp_wsize = fpioc->fp_wsize; 270 fpadd.fp_psize = fpioc->fp_psize; 271 fpadd.fp_mss = fpioc->fp_mss; 272 fpadd.fp_flags = fpioc->fp_flags; 273 fpadd.fp_optcnt = fpioc->fp_optcnt; 274 fpadd.fp_wscale = fpioc->fp_wscale; 275 fpadd.fp_ttl = fpioc->fp_ttl; 276 277 #if 0 /* XXX RYAN wants to fix logging */ 278 DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d " 279 "(TS=%s,M=%s%d,W=%s%d) %x\n", 280 fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm, 281 fpioc->fp_os.fp_subtype_nm, 282 (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" : 283 (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" : 284 (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" : 285 (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "", 286 fpadd.fp_wsize, 287 fpadd.fp_ttl, 288 (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0, 289 (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" : 290 (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "", 291 fpadd.fp_psize, 292 (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt, 293 (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "", 294 (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" : 295 (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "", 296 fpadd.fp_mss, 297 (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" : 298 (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "", 299 fpadd.fp_wscale, 300 fpioc->fp_os.fp_os); 301 #endif 302 303 if ((fp = pf_osfp_find_exact(&V_pf_osfp_list, &fpadd))) { 304 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) { 305 if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os)) 306 return (EEXIST); 307 } 308 if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT)) 309 == NULL) 310 return (ENOMEM); 311 } else { 312 if ((fp = malloc(sizeof(*fp), M_PFOSFP, M_ZERO | M_NOWAIT)) 313 == NULL) 314 return (ENOMEM); 315 fp->fp_tcpopts = fpioc->fp_tcpopts; 316 fp->fp_wsize = fpioc->fp_wsize; 317 fp->fp_psize = fpioc->fp_psize; 318 fp->fp_mss = fpioc->fp_mss; 319 fp->fp_flags = fpioc->fp_flags; 320 fp->fp_optcnt = fpioc->fp_optcnt; 321 fp->fp_wscale = fpioc->fp_wscale; 322 fp->fp_ttl = fpioc->fp_ttl; 323 SLIST_INIT(&fp->fp_oses); 324 if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT)) 325 == NULL) { 326 free(fp, M_PFOSFP); 327 return (ENOMEM); 328 } 329 pf_osfp_insert(&V_pf_osfp_list, fp); 330 } 331 memcpy(entry, &fpioc->fp_os, sizeof(*entry)); 332 333 /* Make sure the strings are NUL terminated */ 334 entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0'; 335 entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0'; 336 entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0'; 337 338 SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry); 339 340 #ifdef PFDEBUG 341 if ((fp = pf_osfp_validate())) 342 printf("Invalid fingerprint list\n"); 343 #endif /* PFDEBUG */ 344 return (0); 345 } 346 347 /* Find a fingerprint in the list */ 348 static struct pf_os_fingerprint * 349 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find, 350 u_int8_t ttldiff) 351 { 352 struct pf_os_fingerprint *f; 353 354 #define MATCH_INT(_MOD, _DC, _field) \ 355 if ((f->fp_flags & _DC) == 0) { \ 356 if ((f->fp_flags & _MOD) == 0) { \ 357 if (f->_field != find->_field) \ 358 continue; \ 359 } else { \ 360 if (f->_field == 0 || find->_field % f->_field) \ 361 continue; \ 362 } \ 363 } 364 365 SLIST_FOREACH(f, list, fp_next) { 366 if (f->fp_tcpopts != find->fp_tcpopts || 367 f->fp_optcnt != find->fp_optcnt || 368 f->fp_ttl < find->fp_ttl || 369 f->fp_ttl - find->fp_ttl > ttldiff || 370 (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) != 371 (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0))) 372 continue; 373 374 MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize) 375 MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss) 376 MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale) 377 if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) { 378 if (f->fp_flags & PF_OSFP_WSIZE_MSS) { 379 if (find->fp_mss == 0) 380 continue; 381 382 /* 383 * Some "smart" NAT devices and DSL routers will tweak the MSS size and 384 * will set it to whatever is suitable for the link type. 385 */ 386 #define SMART_MSS 1460 387 if ((find->fp_wsize % find->fp_mss || 388 find->fp_wsize / find->fp_mss != 389 f->fp_wsize) && 390 (find->fp_wsize % SMART_MSS || 391 find->fp_wsize / SMART_MSS != 392 f->fp_wsize)) 393 continue; 394 } else if (f->fp_flags & PF_OSFP_WSIZE_MTU) { 395 if (find->fp_mss == 0) 396 continue; 397 398 #define MTUOFF (sizeof(struct ip) + sizeof(struct tcphdr)) 399 #define SMART_MTU (SMART_MSS + MTUOFF) 400 if ((find->fp_wsize % (find->fp_mss + MTUOFF) || 401 find->fp_wsize / (find->fp_mss + MTUOFF) != 402 f->fp_wsize) && 403 (find->fp_wsize % SMART_MTU || 404 find->fp_wsize / SMART_MTU != 405 f->fp_wsize)) 406 continue; 407 } else if (f->fp_flags & PF_OSFP_WSIZE_MOD) { 408 if (f->fp_wsize == 0 || find->fp_wsize % 409 f->fp_wsize) 410 continue; 411 } else { 412 if (f->fp_wsize != find->fp_wsize) 413 continue; 414 } 415 } 416 return (f); 417 } 418 419 return (NULL); 420 } 421 422 /* Find an exact fingerprint in the list */ 423 static struct pf_os_fingerprint * 424 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find) 425 { 426 struct pf_os_fingerprint *f; 427 428 SLIST_FOREACH(f, list, fp_next) { 429 if (f->fp_tcpopts == find->fp_tcpopts && 430 f->fp_wsize == find->fp_wsize && 431 f->fp_psize == find->fp_psize && 432 f->fp_mss == find->fp_mss && 433 f->fp_flags == find->fp_flags && 434 f->fp_optcnt == find->fp_optcnt && 435 f->fp_wscale == find->fp_wscale && 436 f->fp_ttl == find->fp_ttl) 437 return (f); 438 } 439 440 return (NULL); 441 } 442 443 /* Insert a fingerprint into the list */ 444 static void 445 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins) 446 { 447 struct pf_os_fingerprint *f, *prev = NULL; 448 449 /* XXX need to go semi tree based. can key on tcp options */ 450 451 SLIST_FOREACH(f, list, fp_next) 452 prev = f; 453 if (prev) 454 SLIST_INSERT_AFTER(prev, ins, fp_next); 455 else 456 SLIST_INSERT_HEAD(list, ins, fp_next); 457 } 458 459 /* Fill a fingerprint by its number (from an ioctl) */ 460 int 461 pf_osfp_get(struct pf_osfp_ioctl *fpioc) 462 { 463 struct pf_os_fingerprint *fp; 464 struct pf_osfp_entry *entry; 465 int num = fpioc->fp_getnum; 466 int i = 0; 467 468 memset(fpioc, 0, sizeof(*fpioc)); 469 SLIST_FOREACH(fp, &V_pf_osfp_list, fp_next) { 470 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) { 471 if (i++ == num) { 472 fpioc->fp_mss = fp->fp_mss; 473 fpioc->fp_wsize = fp->fp_wsize; 474 fpioc->fp_flags = fp->fp_flags; 475 fpioc->fp_psize = fp->fp_psize; 476 fpioc->fp_ttl = fp->fp_ttl; 477 fpioc->fp_wscale = fp->fp_wscale; 478 fpioc->fp_getnum = num; 479 memcpy(&fpioc->fp_os, entry, 480 sizeof(fpioc->fp_os)); 481 return (0); 482 } 483 } 484 } 485 486 return (EBUSY); 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