pf_osfp.c revision 315028
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: stable/10/sys/netpfil/pf/pf_osfp.c 315028 2017-03-10 20:38:18Z vangyzen $"); 21 22#include "opt_inet6.h" 23 24#include <sys/param.h> 25#include <sys/kernel.h> 26#include <sys/socket.h> 27 28#include <netinet/in.h> 29#include <netinet/ip.h> 30#include <netinet/tcp.h> 31 32#include <net/if.h> 33#include <net/pfvar.h> 34 35#ifdef INET6 36#include <netinet/ip6.h> 37#include <netinet6/in6_var.h> 38#endif 39 40static MALLOC_DEFINE(M_PFOSFP, "pf_osfp", "pf(4) operating system fingerprints"); 41#define DPFPRINTF(format, x...) \ 42 if (V_pf_status.debug >= PF_DEBUG_NOISY) \ 43 printf(format , ##x) 44 45SLIST_HEAD(pf_osfp_list, pf_os_fingerprint); 46static VNET_DEFINE(struct pf_osfp_list, pf_osfp_list) = 47 SLIST_HEAD_INITIALIZER(); 48#define V_pf_osfp_list VNET(pf_osfp_list) 49 50static struct pf_osfp_enlist *pf_osfp_fingerprint_hdr(const struct ip *, 51 const struct ip6_hdr *, 52 const struct tcphdr *); 53static struct pf_os_fingerprint *pf_osfp_find(struct pf_osfp_list *, 54 struct pf_os_fingerprint *, u_int8_t); 55static struct pf_os_fingerprint *pf_osfp_find_exact(struct pf_osfp_list *, 56 struct pf_os_fingerprint *); 57static void pf_osfp_insert(struct pf_osfp_list *, 58 struct pf_os_fingerprint *); 59#ifdef PFDEBUG 60static struct pf_os_fingerprint *pf_osfp_validate(void); 61#endif 62 63/* 64 * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only) 65 * Returns the list of possible OSes. 66 */ 67struct pf_osfp_enlist * 68pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off, 69 const struct tcphdr *tcp) 70{ 71 struct ip *ip; 72 struct ip6_hdr *ip6; 73 char hdr[60]; 74 75 if ((pd->af != PF_INET && pd->af != PF_INET6) || 76 pd->proto != IPPROTO_TCP || (tcp->th_off << 2) < sizeof(*tcp)) 77 return (NULL); 78 79 if (pd->af == PF_INET) { 80 ip = mtod(m, struct ip *); 81 ip6 = (struct ip6_hdr *)NULL; 82 } else { 83 ip = (struct ip *)NULL; 84 ip6 = mtod(m, struct ip6_hdr *); 85 } 86 if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL, 87 pd->af)) return (NULL); 88 89 return (pf_osfp_fingerprint_hdr(ip, ip6, (struct tcphdr *)hdr)); 90} 91 92static struct pf_osfp_enlist * 93pf_osfp_fingerprint_hdr(const struct ip *ip, const struct ip6_hdr *ip6, const struct tcphdr *tcp) 94{ 95 struct pf_os_fingerprint fp, *fpresult; 96 int cnt, optlen = 0; 97 const u_int8_t *optp; 98#ifdef INET6 99 char srcname[INET6_ADDRSTRLEN]; 100#else 101 char srcname[INET_ADDRSTRLEN]; 102#endif 103 104 if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN) 105 return (NULL); 106 if (ip) { 107 if ((ip->ip_off & htons(IP_OFFMASK)) != 0) 108 return (NULL); 109 } 110 111 memset(&fp, 0, sizeof(fp)); 112 113 if (ip) { 114 fp.fp_psize = ntohs(ip->ip_len); 115 fp.fp_ttl = ip->ip_ttl; 116 if (ip->ip_off & htons(IP_DF)) 117 fp.fp_flags |= PF_OSFP_DF; 118 inet_ntoa_r(ip->ip_src, srcname); 119 } 120#ifdef INET6 121 else if (ip6) { 122 /* jumbo payload? */ 123 fp.fp_psize = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen); 124 fp.fp_ttl = ip6->ip6_hlim; 125 fp.fp_flags |= PF_OSFP_DF; 126 fp.fp_flags |= PF_OSFP_INET6; 127 ip6_sprintf(srcname, (const struct in6_addr *)&ip6->ip6_src); 128 } 129#endif 130 else 131 return (NULL); 132 fp.fp_wsize = ntohs(tcp->th_win); 133 134 135 cnt = (tcp->th_off << 2) - sizeof(*tcp); 136 optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp)); 137 for (; cnt > 0; cnt -= optlen, optp += optlen) { 138 if (*optp == TCPOPT_EOL) 139 break; 140 141 fp.fp_optcnt++; 142 if (*optp == TCPOPT_NOP) { 143 fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) | 144 PF_OSFP_TCPOPT_NOP; 145 optlen = 1; 146 } else { 147 if (cnt < 2) 148 return (NULL); 149 optlen = optp[1]; 150 if (optlen > cnt || optlen < 2) 151 return (NULL); 152 switch (*optp) { 153 case TCPOPT_MAXSEG: 154 if (optlen >= TCPOLEN_MAXSEG) 155 memcpy(&fp.fp_mss, &optp[2], 156 sizeof(fp.fp_mss)); 157 fp.fp_tcpopts = (fp.fp_tcpopts << 158 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS; 159 NTOHS(fp.fp_mss); 160 break; 161 case TCPOPT_WINDOW: 162 if (optlen >= TCPOLEN_WINDOW) 163 memcpy(&fp.fp_wscale, &optp[2], 164 sizeof(fp.fp_wscale)); 165 NTOHS(fp.fp_wscale); 166 fp.fp_tcpopts = (fp.fp_tcpopts << 167 PF_OSFP_TCPOPT_BITS) | 168 PF_OSFP_TCPOPT_WSCALE; 169 break; 170 case TCPOPT_SACK_PERMITTED: 171 fp.fp_tcpopts = (fp.fp_tcpopts << 172 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK; 173 break; 174 case TCPOPT_TIMESTAMP: 175 if (optlen >= TCPOLEN_TIMESTAMP) { 176 u_int32_t ts; 177 memcpy(&ts, &optp[2], sizeof(ts)); 178 if (ts == 0) 179 fp.fp_flags |= PF_OSFP_TS0; 180 181 } 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 */ 212int 213pf_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 */ 242void 243pf_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} 257 258 259/* Add a fingerprint */ 260int 261pf_osfp_add(struct pf_osfp_ioctl *fpioc) 262{ 263 struct pf_os_fingerprint *fp, fpadd; 264 struct pf_osfp_entry *entry; 265 266 PF_RULES_WASSERT(); 267 268 memset(&fpadd, 0, sizeof(fpadd)); 269 fpadd.fp_tcpopts = fpioc->fp_tcpopts; 270 fpadd.fp_wsize = fpioc->fp_wsize; 271 fpadd.fp_psize = fpioc->fp_psize; 272 fpadd.fp_mss = fpioc->fp_mss; 273 fpadd.fp_flags = fpioc->fp_flags; 274 fpadd.fp_optcnt = fpioc->fp_optcnt; 275 fpadd.fp_wscale = fpioc->fp_wscale; 276 fpadd.fp_ttl = fpioc->fp_ttl; 277 278#if 0 /* XXX RYAN wants to fix logging */ 279 DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d " 280 "(TS=%s,M=%s%d,W=%s%d) %x\n", 281 fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm, 282 fpioc->fp_os.fp_subtype_nm, 283 (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" : 284 (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" : 285 (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" : 286 (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "", 287 fpadd.fp_wsize, 288 fpadd.fp_ttl, 289 (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0, 290 (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" : 291 (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "", 292 fpadd.fp_psize, 293 (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt, 294 (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "", 295 (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" : 296 (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "", 297 fpadd.fp_mss, 298 (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" : 299 (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "", 300 fpadd.fp_wscale, 301 fpioc->fp_os.fp_os); 302#endif 303 304 if ((fp = pf_osfp_find_exact(&V_pf_osfp_list, &fpadd))) { 305 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) { 306 if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os)) 307 return (EEXIST); 308 } 309 if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT)) 310 == NULL) 311 return (ENOMEM); 312 } else { 313 if ((fp = malloc(sizeof(*fp), M_PFOSFP, M_ZERO | M_NOWAIT)) 314 == NULL) 315 return (ENOMEM); 316 fp->fp_tcpopts = fpioc->fp_tcpopts; 317 fp->fp_wsize = fpioc->fp_wsize; 318 fp->fp_psize = fpioc->fp_psize; 319 fp->fp_mss = fpioc->fp_mss; 320 fp->fp_flags = fpioc->fp_flags; 321 fp->fp_optcnt = fpioc->fp_optcnt; 322 fp->fp_wscale = fpioc->fp_wscale; 323 fp->fp_ttl = fpioc->fp_ttl; 324 SLIST_INIT(&fp->fp_oses); 325 if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT)) 326 == NULL) { 327 free(fp, M_PFOSFP); 328 return (ENOMEM); 329 } 330 pf_osfp_insert(&V_pf_osfp_list, fp); 331 } 332 memcpy(entry, &fpioc->fp_os, sizeof(*entry)); 333 334 /* Make sure the strings are NUL terminated */ 335 entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0'; 336 entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0'; 337 entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0'; 338 339 SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry); 340 341#ifdef PFDEBUG 342 if ((fp = pf_osfp_validate())) 343 printf("Invalid fingerprint list\n"); 344#endif /* PFDEBUG */ 345 return (0); 346} 347 348 349/* Find a fingerprint in the list */ 350static struct pf_os_fingerprint * 351pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find, 352 u_int8_t ttldiff) 353{ 354 struct pf_os_fingerprint *f; 355 356#define MATCH_INT(_MOD, _DC, _field) \ 357 if ((f->fp_flags & _DC) == 0) { \ 358 if ((f->fp_flags & _MOD) == 0) { \ 359 if (f->_field != find->_field) \ 360 continue; \ 361 } else { \ 362 if (f->_field == 0 || find->_field % f->_field) \ 363 continue; \ 364 } \ 365 } 366 367 SLIST_FOREACH(f, list, fp_next) { 368 if (f->fp_tcpopts != find->fp_tcpopts || 369 f->fp_optcnt != find->fp_optcnt || 370 f->fp_ttl < find->fp_ttl || 371 f->fp_ttl - find->fp_ttl > ttldiff || 372 (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) != 373 (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0))) 374 continue; 375 376 MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize) 377 MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss) 378 MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale) 379 if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) { 380 if (f->fp_flags & PF_OSFP_WSIZE_MSS) { 381 if (find->fp_mss == 0) 382 continue; 383 384/* 385 * Some "smart" NAT devices and DSL routers will tweak the MSS size and 386 * will set it to whatever is suitable for the link type. 387 */ 388#define SMART_MSS 1460 389 if ((find->fp_wsize % find->fp_mss || 390 find->fp_wsize / find->fp_mss != 391 f->fp_wsize) && 392 (find->fp_wsize % SMART_MSS || 393 find->fp_wsize / SMART_MSS != 394 f->fp_wsize)) 395 continue; 396 } else if (f->fp_flags & PF_OSFP_WSIZE_MTU) { 397 if (find->fp_mss == 0) 398 continue; 399 400#define MTUOFF (sizeof(struct ip) + sizeof(struct tcphdr)) 401#define SMART_MTU (SMART_MSS + MTUOFF) 402 if ((find->fp_wsize % (find->fp_mss + MTUOFF) || 403 find->fp_wsize / (find->fp_mss + MTUOFF) != 404 f->fp_wsize) && 405 (find->fp_wsize % SMART_MTU || 406 find->fp_wsize / SMART_MTU != 407 f->fp_wsize)) 408 continue; 409 } else if (f->fp_flags & PF_OSFP_WSIZE_MOD) { 410 if (f->fp_wsize == 0 || find->fp_wsize % 411 f->fp_wsize) 412 continue; 413 } else { 414 if (f->fp_wsize != find->fp_wsize) 415 continue; 416 } 417 } 418 return (f); 419 } 420 421 return (NULL); 422} 423 424/* Find an exact fingerprint in the list */ 425static struct pf_os_fingerprint * 426pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find) 427{ 428 struct pf_os_fingerprint *f; 429 430 SLIST_FOREACH(f, list, fp_next) { 431 if (f->fp_tcpopts == find->fp_tcpopts && 432 f->fp_wsize == find->fp_wsize && 433 f->fp_psize == find->fp_psize && 434 f->fp_mss == find->fp_mss && 435 f->fp_flags == find->fp_flags && 436 f->fp_optcnt == find->fp_optcnt && 437 f->fp_wscale == find->fp_wscale && 438 f->fp_ttl == find->fp_ttl) 439 return (f); 440 } 441 442 return (NULL); 443} 444 445/* Insert a fingerprint into the list */ 446static void 447pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins) 448{ 449 struct pf_os_fingerprint *f, *prev = NULL; 450 451 /* XXX need to go semi tree based. can key on tcp options */ 452 453 SLIST_FOREACH(f, list, fp_next) 454 prev = f; 455 if (prev) 456 SLIST_INSERT_AFTER(prev, ins, fp_next); 457 else 458 SLIST_INSERT_HEAD(list, ins, fp_next); 459} 460 461/* Fill a fingerprint by its number (from an ioctl) */ 462int 463pf_osfp_get(struct pf_osfp_ioctl *fpioc) 464{ 465 struct pf_os_fingerprint *fp; 466 struct pf_osfp_entry *entry; 467 int num = fpioc->fp_getnum; 468 int i = 0; 469 470 471 memset(fpioc, 0, sizeof(*fpioc)); 472 SLIST_FOREACH(fp, &V_pf_osfp_list, fp_next) { 473 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) { 474 if (i++ == num) { 475 fpioc->fp_mss = fp->fp_mss; 476 fpioc->fp_wsize = fp->fp_wsize; 477 fpioc->fp_flags = fp->fp_flags; 478 fpioc->fp_psize = fp->fp_psize; 479 fpioc->fp_ttl = fp->fp_ttl; 480 fpioc->fp_wscale = fp->fp_wscale; 481 fpioc->fp_getnum = num; 482 memcpy(&fpioc->fp_os, entry, 483 sizeof(fpioc->fp_os)); 484 return (0); 485 } 486 } 487 } 488 489 return (EBUSY); 490} 491 492 493#ifdef PFDEBUG 494/* Validate that each signature is reachable */ 495static struct pf_os_fingerprint * 496pf_osfp_validate(void) 497{ 498 struct pf_os_fingerprint *f, *f2, find; 499 500 SLIST_FOREACH(f, &V_pf_osfp_list, fp_next) { 501 memcpy(&find, f, sizeof(find)); 502 503 /* We do a few MSS/th_win percolations to make things unique */ 504 if (find.fp_mss == 0) 505 find.fp_mss = 128; 506 if (f->fp_flags & PF_OSFP_WSIZE_MSS) 507 find.fp_wsize *= find.fp_mss; 508 else if (f->fp_flags & PF_OSFP_WSIZE_MTU) 509 find.fp_wsize *= (find.fp_mss + 40); 510 else if (f->fp_flags & PF_OSFP_WSIZE_MOD) 511 find.fp_wsize *= 2; 512 if (f != (f2 = pf_osfp_find(&V_pf_osfp_list, &find, 0))) { 513 if (f2) 514 printf("Found \"%s %s %s\" instead of " 515 "\"%s %s %s\"\n", 516 SLIST_FIRST(&f2->fp_oses)->fp_class_nm, 517 SLIST_FIRST(&f2->fp_oses)->fp_version_nm, 518 SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm, 519 SLIST_FIRST(&f->fp_oses)->fp_class_nm, 520 SLIST_FIRST(&f->fp_oses)->fp_version_nm, 521 SLIST_FIRST(&f->fp_oses)->fp_subtype_nm); 522 else 523 printf("Couldn't find \"%s %s %s\"\n", 524 SLIST_FIRST(&f->fp_oses)->fp_class_nm, 525 SLIST_FIRST(&f->fp_oses)->fp_version_nm, 526 SLIST_FIRST(&f->fp_oses)->fp_subtype_nm); 527 return (f); 528 } 529 } 530 return (NULL); 531} 532#endif /* PFDEBUG */ 533