1 /* $OpenBSD: pf_osfp.c,v 1.10 2004/04/09 19:30:41 frantzen Exp $ */
2
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 */
19
20 #include <sys/param.h>
21 #include <sys/socket.h>
22 #ifdef _KERNEL
23 # include <sys/systm.h>
24 #endif /* _KERNEL */
25 #include <sys/mbuf.h>
26
27 #include <netinet/in.h>
28 #include <netinet/in_systm.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 #endif /* INET6 */
38
39
40 #ifdef _KERNEL
41 # define DPFPRINTF(format, x...) \
42 if (pf_status.debug >= PF_DEBUG_NOISY) \
43 printf(format , ##x)
44 typedef struct pool pool_t;
45
46 #else
47 /* Userland equivalents so we can lend code to tcpdump et al. */
48
49 # include <arpa/inet.h>
50 # include <errno.h>
51 # include <stdio.h>
52 # include <stdlib.h>
53 # include <string.h>
54 # define pool_t int
55 # define pool_get(pool, flags) malloc(*(pool))
56 # define pool_put(pool, item) free(item)
57 # define pool_init(pool, size, a, ao, f, m, p) (*(pool)) = (size)
58
59 # ifdef PFDEBUG
60 # include <sys/stdarg.h>
61 # define DPFPRINTF(format, x...) fprintf(stderr, format , ##x)
62 # else
63 # define DPFPRINTF(format, x...) ((void)0)
64 # endif /* PFDEBUG */
65 #endif /* _KERNEL */
66
67
68 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint) pf_osfp_list;
69 pool_t pf_osfp_entry_pl;
70 pool_t pf_osfp_pl;
71
72 struct pf_os_fingerprint *pf_osfp_find(struct pf_osfp_list *,
73 struct pf_os_fingerprint *, u_int8_t);
74 struct pf_os_fingerprint *pf_osfp_find_exact(struct pf_osfp_list *,
75 struct pf_os_fingerprint *);
76 void pf_osfp_insert(struct pf_osfp_list *,
77 struct pf_os_fingerprint *);
78
79
80 #ifdef _KERNEL
81 /*
82 * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
83 * Returns the list of possible OSes.
84 */
85 struct pf_osfp_enlist *
pf_osfp_fingerprint(struct pf_pdesc * pd,struct mbuf * m,int off,const struct tcphdr * tcp)86 pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off,
87 const struct tcphdr *tcp)
88 {
89 struct ip *ip;
90 char hdr[60];
91
92 /* XXX don't have a fingerprint database for IPv6 :-( */
93 if (pd->af != PF_INET || pd->proto != IPPROTO_TCP || (tcp->th_off << 2)
94 < sizeof(*tcp))
95 return (NULL);
96
97 ip = mtod(m, struct ip *);
98 if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL, pd->af))
99 return (NULL);
100
101 return (pf_osfp_fingerprint_hdr(ip, (struct tcphdr *)hdr));
102 }
103 #endif /* _KERNEL */
104
105 struct pf_osfp_enlist *
pf_osfp_fingerprint_hdr(const struct ip * ip,const struct tcphdr * tcp)106 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct tcphdr *tcp)
107 {
108 struct pf_os_fingerprint fp, *fpresult;
109 int cnt, optlen = 0;
110 const u_int8_t *optp;
111
112 if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN || (ip->ip_off &
113 htons(IP_OFFMASK)))
114 return (NULL);
115
116 memset(&fp, 0, sizeof(fp));
117
118 fp.fp_psize = ntohs(ip->ip_len);
119 fp.fp_ttl = ip->ip_ttl;
120 if (ip->ip_off & htons(IP_DF))
121 fp.fp_flags |= PF_OSFP_DF;
122 fp.fp_wsize = ntohs(tcp->th_win);
123
124
125 cnt = (tcp->th_off << 2) - sizeof(*tcp);
126 optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp));
127 for (; cnt > 0; cnt -= optlen, optp += optlen) {
128 if (*optp == TCPOPT_EOL)
129 break;
130
131 fp.fp_optcnt++;
132 if (*optp == TCPOPT_NOP) {
133 fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
134 PF_OSFP_TCPOPT_NOP;
135 optlen = 1;
136 } else {
137 if (cnt < 2)
138 return (NULL);
139 optlen = optp[1];
140 if (optlen > cnt || optlen < 2)
141 return (NULL);
142 switch (*optp) {
143 case TCPOPT_MAXSEG:
144 if (optlen >= TCPOLEN_MAXSEG)
145 memcpy(&fp.fp_mss, &optp[2],
146 sizeof(fp.fp_mss));
147 fp.fp_tcpopts = (fp.fp_tcpopts <<
148 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
149 NTOHS(fp.fp_mss);
150 break;
151 case TCPOPT_WINDOW:
152 if (optlen >= TCPOLEN_WINDOW)
153 memcpy(&fp.fp_wscale, &optp[2],
154 sizeof(fp.fp_wscale));
155 NTOHS(fp.fp_wscale);
156 fp.fp_tcpopts = (fp.fp_tcpopts <<
157 PF_OSFP_TCPOPT_BITS) |
158 PF_OSFP_TCPOPT_WSCALE;
159 break;
160 case TCPOPT_SACK_PERMITTED:
161 fp.fp_tcpopts = (fp.fp_tcpopts <<
162 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
163 break;
164 case TCPOPT_TIMESTAMP:
165 if (optlen >= TCPOLEN_TIMESTAMP) {
166 u_int32_t ts;
167 memcpy(&ts, &optp[2], sizeof(ts));
168 if (ts == 0)
169 fp.fp_flags |= PF_OSFP_TS0;
170
171 }
172 fp.fp_tcpopts = (fp.fp_tcpopts <<
173 PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
174 break;
175 default:
176 return (NULL);
177 }
178 }
179 optlen = MAX(optlen, 1); /* paranoia */
180 }
181
182 DPFPRINTF("fingerprinted %s:%d %d:%d:%d:%d:%llx (%d) "
183 "(TS=%s,M=%s%d,W=%s%d)\n",
184 inet_ntoa(ip->ip_src), ntohs(tcp->th_sport),
185 fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
186 fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
187 (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
188 (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
189 (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
190 fp.fp_mss,
191 (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
192 (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
193 fp.fp_wscale);
194
195 if ((fpresult = pf_osfp_find(&pf_osfp_list, &fp,
196 PF_OSFP_MAXTTL_OFFSET)))
197 return (&fpresult->fp_oses);
198 return (NULL);
199 }
200
201 /* Match a fingerprint ID against a list of OSes */
202 int
pf_osfp_match(struct pf_osfp_enlist * list,pf_osfp_t os)203 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
204 {
205 struct pf_osfp_entry *entry;
206 int os_class, os_version, os_subtype;
207 int en_class, en_version, en_subtype;
208
209 if (os == PF_OSFP_ANY)
210 return (1);
211 if (list == NULL) {
212 DPFPRINTF("osfp no match against %x\n", os);
213 return (os == PF_OSFP_UNKNOWN);
214 }
215 PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
216 SLIST_FOREACH(entry, list, fp_entry) {
217 PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
218 if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
219 (os_version == PF_OSFP_ANY || en_version == os_version) &&
220 (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
221 DPFPRINTF("osfp matched %s %s %s %x==%x\n",
222 entry->fp_class_nm, entry->fp_version_nm,
223 entry->fp_subtype_nm, os, entry->fp_os);
224 return (1);
225 }
226 }
227 DPFPRINTF("fingerprint 0x%x didn't match\n", os);
228 return (0);
229 }
230
231 /* Initialize the OS fingerprint system */
232 void
pf_osfp_initialize(void)233 pf_osfp_initialize(void)
234 {
235 pool_init(&pf_osfp_entry_pl, sizeof(struct pf_osfp_entry), 0, 0, 0,
236 "pfosfpen", &pool_allocator_nointr);
237 pool_init(&pf_osfp_pl, sizeof(struct pf_os_fingerprint), 0, 0, 0,
238 "pfosfp", &pool_allocator_nointr);
239 SLIST_INIT(&pf_osfp_list);
240 }
241
242 /* Flush the fingerprint list */
243 void
pf_osfp_flush(void)244 pf_osfp_flush(void)
245 {
246 struct pf_os_fingerprint *fp;
247 struct pf_osfp_entry *entry;
248
249 while ((fp = SLIST_FIRST(&pf_osfp_list))) {
250 SLIST_REMOVE_HEAD(&pf_osfp_list, fp_next);
251 while ((entry = SLIST_FIRST(&fp->fp_oses))) {
252 SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
253 pool_put(&pf_osfp_entry_pl, entry);
254 }
255 pool_put(&pf_osfp_pl, fp);
256 }
257 }
258
259
260 /* Add a fingerprint */
261 int
pf_osfp_add(struct pf_osfp_ioctl * fpioc)262 pf_osfp_add(struct pf_osfp_ioctl *fpioc)
263 {
264 struct pf_os_fingerprint *fp, fpadd;
265 struct pf_osfp_entry *entry;
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 DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
278 "(TS=%s,M=%s%d,W=%s%d) %x\n",
279 fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
280 fpioc->fp_os.fp_subtype_nm,
281 (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
282 (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
283 (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
284 (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
285 fpadd.fp_wsize,
286 fpadd.fp_ttl,
287 (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
288 (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
289 (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
290 fpadd.fp_psize,
291 (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
292 (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
293 (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
294 (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
295 fpadd.fp_mss,
296 (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
297 (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
298 fpadd.fp_wscale,
299 fpioc->fp_os.fp_os);
300
301
302 if ((fp = pf_osfp_find_exact(&pf_osfp_list, &fpadd))) {
303 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
304 if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
305 return (EEXIST);
306 }
307 if ((entry = pool_get(&pf_osfp_entry_pl, PR_NOWAIT)) == NULL)
308 return (ENOMEM);
309 } else {
310 if ((fp = pool_get(&pf_osfp_pl, PR_NOWAIT)) == NULL)
311 return (ENOMEM);
312 memset(fp, 0, sizeof(*fp));
313 fp->fp_tcpopts = fpioc->fp_tcpopts;
314 fp->fp_wsize = fpioc->fp_wsize;
315 fp->fp_psize = fpioc->fp_psize;
316 fp->fp_mss = fpioc->fp_mss;
317 fp->fp_flags = fpioc->fp_flags;
318 fp->fp_optcnt = fpioc->fp_optcnt;
319 fp->fp_wscale = fpioc->fp_wscale;
320 fp->fp_ttl = fpioc->fp_ttl;
321 SLIST_INIT(&fp->fp_oses);
322 if ((entry = pool_get(&pf_osfp_entry_pl, PR_NOWAIT)) == NULL) {
323 pool_put(&pf_osfp_pl, fp);
324 return (ENOMEM);
325 }
326 pf_osfp_insert(&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 struct pf_os_fingerprint *
pf_osfp_find(struct pf_osfp_list * list,struct pf_os_fingerprint * find,u_int8_t ttldiff)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 /* Some "smart" NAT devices and DSL routers will tweak the MSS size and
381 * will set it to whatever is suitable for the link type.
382 */
383 #define SMART_MSS 1460
384 if ((find->fp_wsize % find->fp_mss ||
385 find->fp_wsize / find->fp_mss !=
386 f->fp_wsize) &&
387 (find->fp_wsize % SMART_MSS ||
388 find->fp_wsize / SMART_MSS !=
389 f->fp_wsize))
390 continue;
391 } else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
392 if (find->fp_mss == 0)
393 continue;
394
395 #define MTUOFF (sizeof(struct ip) + sizeof(struct tcphdr))
396 #define SMART_MTU (SMART_MSS + MTUOFF)
397 if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
398 find->fp_wsize / (find->fp_mss + MTUOFF) !=
399 f->fp_wsize) &&
400 (find->fp_wsize % SMART_MTU ||
401 find->fp_wsize / SMART_MTU !=
402 f->fp_wsize))
403 continue;
404 } else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
405 if (f->fp_wsize == 0 || find->fp_wsize %
406 f->fp_wsize)
407 continue;
408 } else {
409 if (f->fp_wsize != find->fp_wsize)
410 continue;
411 }
412 }
413 return (f);
414 }
415
416 return (NULL);
417 }
418
419 /* Find an exact fingerprint in the list */
420 struct pf_os_fingerprint *
pf_osfp_find_exact(struct pf_osfp_list * list,struct pf_os_fingerprint * find)421 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
422 {
423 struct pf_os_fingerprint *f;
424
425 SLIST_FOREACH(f, list, fp_next) {
426 if (f->fp_tcpopts == find->fp_tcpopts &&
427 f->fp_wsize == find->fp_wsize &&
428 f->fp_psize == find->fp_psize &&
429 f->fp_mss == find->fp_mss &&
430 f->fp_flags == find->fp_flags &&
431 f->fp_optcnt == find->fp_optcnt &&
432 f->fp_wscale == find->fp_wscale &&
433 f->fp_ttl == find->fp_ttl)
434 return (f);
435 }
436
437 return (NULL);
438 }
439
440 /* Insert a fingerprint into the list */
441 void
pf_osfp_insert(struct pf_osfp_list * list,struct pf_os_fingerprint * ins)442 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
443 {
444 struct pf_os_fingerprint *f, *prev = NULL;
445
446 /* XXX need to go semi tree based. can key on tcp options */
447
448 SLIST_FOREACH(f, list, fp_next)
449 prev = f;
450 if (prev)
451 SLIST_INSERT_AFTER(prev, ins, fp_next);
452 else
453 SLIST_INSERT_HEAD(list, ins, fp_next);
454 }
455
456 /* Fill a fingerprint by its number (from an ioctl) */
457 int
pf_osfp_get(struct pf_osfp_ioctl * fpioc)458 pf_osfp_get(struct pf_osfp_ioctl *fpioc)
459 {
460 struct pf_os_fingerprint *fp;
461 struct pf_osfp_entry *entry;
462 int num = fpioc->fp_getnum;
463 int i = 0;
464
465
466 memset(fpioc, 0, sizeof(*fpioc));
467 SLIST_FOREACH(fp, &pf_osfp_list, fp_next) {
468 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
469 if (i++ == num) {
470 fpioc->fp_mss = fp->fp_mss;
471 fpioc->fp_wsize = fp->fp_wsize;
472 fpioc->fp_flags = fp->fp_flags;
473 fpioc->fp_psize = fp->fp_psize;
474 fpioc->fp_ttl = fp->fp_ttl;
475 fpioc->fp_wscale = fp->fp_wscale;
476 fpioc->fp_getnum = num;
477 memcpy(&fpioc->fp_os, entry,
478 sizeof(fpioc->fp_os));
479 return (0);
480 }
481 }
482 }
483
484 return (EBUSY);
485 }
486
487
488 /* Validate that each signature is reachable */
489 struct pf_os_fingerprint *
pf_osfp_validate(void)490 pf_osfp_validate(void)
491 {
492 struct pf_os_fingerprint *f, *f2, find;
493
494 SLIST_FOREACH(f, &pf_osfp_list, fp_next) {
495 memcpy(&find, f, sizeof(find));
496
497 /* We do a few MSS/th_win percolations to make things unique */
498 if (find.fp_mss == 0)
499 find.fp_mss = 128;
500 if (f->fp_flags & PF_OSFP_WSIZE_MSS)
501 find.fp_wsize *= find.fp_mss, 1;
502 else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
503 find.fp_wsize *= (find.fp_mss + 40);
504 else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
505 find.fp_wsize *= 2;
506 if (f != (f2 = pf_osfp_find(&pf_osfp_list, &find, 0))) {
507 if (f2)
508 printf("Found \"%s %s %s\" instead of "
509 "\"%s %s %s\"\n",
510 SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
511 SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
512 SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
513 SLIST_FIRST(&f->fp_oses)->fp_class_nm,
514 SLIST_FIRST(&f->fp_oses)->fp_version_nm,
515 SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
516 else
517 printf("Couldn't find \"%s %s %s\"\n",
518 SLIST_FIRST(&f->fp_oses)->fp_class_nm,
519 SLIST_FIRST(&f->fp_oses)->fp_version_nm,
520 SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
521 return (f);
522 }
523 }
524 return (NULL);
525 }
526