text: /*	$NetBSD: pf_osfp.c,v 1.4 2004/11/14 11:12:16 yamt Exp $	*/
  /*	$OpenBSD: pf_osfp.c,v 1.10 2004/04/09 19:30:41 frantzen Exp $ */
  
  /*
   * Copyright (c) 2003 Mike Frantzen <frantzen@w4g.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   *
   */
  
  #ifdef _KERNEL_OPT
  #include "opt_inet.h"
  #endif
  
  #include <sys/param.h>
  #include <sys/socket.h>
  #ifdef _KERNEL
  # include <sys/systm.h>
  #endif /* _KERNEL */
  #include <sys/mbuf.h>
  
  #include <netinet/in.h>
  #include <netinet/in_systm.h>
  #include <netinet/ip.h>
  #include <netinet/tcp.h>
  
  #include <net/if.h>
  #include <net/pfvar.h>
  
  #ifdef INET6
  #include <netinet/ip6.h>
  #endif /* INET6 */
  
  
  #ifdef _KERNEL
  # define DPFPRINTF(format, x...)		\
  	if (pf_status.debug >= PF_DEBUG_NOISY)	\
  		printf(format , ##x)
  typedef struct pool pool_t;
  
  #else
  /* Userland equivalents so we can lend code to tcpdump et al. */
  
  # include <arpa/inet.h>
  # include <errno.h>
  # include <stdio.h>
  # include <stdlib.h>
  # include <string.h>
  # define pool_t			int
  # define pool_get(pool, flags)	malloc(*(pool))
  # define pool_put(pool, item)	free(item)
  # define pool_init(pool, size, a, ao, f, m, p)	(*(pool)) = (size)
  
  # ifdef PFDEBUG
  #  include <sys/stdarg.h>
  #  define DPFPRINTF(format, x...)	fprintf(stderr, format , ##x)
  # else
  #  define DPFPRINTF(format, x...)	((void)0)
  # endif /* PFDEBUG */
  #endif /* _KERNEL */
  
  
  SLIST_HEAD(pf_osfp_list, pf_os_fingerprint) pf_osfp_list;
  pool_t pf_osfp_entry_pl;
  pool_t pf_osfp_pl;
  
  struct pf_os_fingerprint	*pf_osfp_find(struct pf_osfp_list *,
  				    struct pf_os_fingerprint *, u_int8_t);
  struct pf_os_fingerprint	*pf_osfp_find_exact(struct pf_osfp_list *,
  				    struct pf_os_fingerprint *);
  void				 pf_osfp_insert(struct pf_osfp_list *,
  				    struct pf_os_fingerprint *);
  
  
  #ifdef _KERNEL
  /*
   * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
   * Returns the list of possible OSes.
   */
  struct pf_osfp_enlist *
  pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off,
      const struct tcphdr *tcp)
  {
  	struct ip *ip;
  	char hdr[60];
  
  	/* XXX don't have a fingerprint database for IPv6 :-( */
  	if (pd->af != PF_INET || pd->proto != IPPROTO_TCP || (tcp->th_off << 2)
  	    < sizeof(*tcp))
  		return (NULL);
  
  	ip = mtod(m, struct ip *);
  	if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL, pd->af))
  		return (NULL);
  
  	return (pf_osfp_fingerprint_hdr(ip, (struct tcphdr *)hdr));
  }
  #endif /* _KERNEL */
  
  struct pf_osfp_enlist *
  pf_osfp_fingerprint_hdr(const struct ip *ip, const struct tcphdr *tcp)
  {
  	struct pf_os_fingerprint fp, *fpresult;
  	int cnt, optlen = 0;
  	const u_int8_t *optp;
  
  	if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN || (ip->ip_off &
  	    htons(IP_OFFMASK)))
  		return (NULL);
  
  	memset(&fp, 0, sizeof(fp));
  
  	fp.fp_psize = ntohs(ip->ip_len);
  	fp.fp_ttl = ip->ip_ttl;
  	if (ip->ip_off & htons(IP_DF))
  		fp.fp_flags |= PF_OSFP_DF;
  	fp.fp_wsize = ntohs(tcp->th_win);
  
  
  	cnt = (tcp->th_off << 2) - sizeof(*tcp);
  	optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp));
  	for (; cnt > 0; cnt -= optlen, optp += optlen) {
  		if (*optp == TCPOPT_EOL)
  			break;
  
  		fp.fp_optcnt++;
  		if (*optp == TCPOPT_NOP) {
  			fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
  			    PF_OSFP_TCPOPT_NOP;
  			optlen = 1;
  		} else {
  			if (cnt < 2)
  				return (NULL);
  			optlen = optp[1];
  			if (optlen > cnt || optlen < 2)
  				return (NULL);
  			switch (*optp) {
  			case TCPOPT_MAXSEG:
  				if (optlen >= TCPOLEN_MAXSEG)
  					memcpy(&fp.fp_mss, &optp[2],
  					    sizeof(fp.fp_mss));
  				fp.fp_tcpopts = (fp.fp_tcpopts <<
  				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
  				NTOHS(fp.fp_mss);
  				break;
  			case TCPOPT_WINDOW:
  				if (optlen >= TCPOLEN_WINDOW)
  					memcpy(&fp.fp_wscale, &optp[2],
  					    sizeof(fp.fp_wscale));
  				NTOHS(fp.fp_wscale);
  				fp.fp_tcpopts = (fp.fp_tcpopts <<
  				    PF_OSFP_TCPOPT_BITS) |
  				    PF_OSFP_TCPOPT_WSCALE;
  				break;
  			case TCPOPT_SACK_PERMITTED:
  				fp.fp_tcpopts = (fp.fp_tcpopts <<
  				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
  				break;
  			case TCPOPT_TIMESTAMP:
  				if (optlen >= TCPOLEN_TIMESTAMP) {
  					u_int32_t ts;
  					memcpy(&ts, &optp[2], sizeof(ts));
  					if (ts == 0)
  						fp.fp_flags |= PF_OSFP_TS0;
  
  				}
  				fp.fp_tcpopts = (fp.fp_tcpopts <<
  				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
  				break;
  			default:
  				return (NULL);
  			}
  		}
  		optlen = MAX(optlen, 1);	/* paranoia */
  	}
  
  	DPFPRINTF("fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
  	    "(TS=%s,M=%s%d,W=%s%d)\n",
  	    inet_ntoa(ip->ip_src), ntohs(tcp->th_sport),
  	    fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
  	    fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
  	    (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
  	    (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
  	    (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
  	    fp.fp_mss,
  	    (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
  	    (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
  	    fp.fp_wscale);
  
  	if ((fpresult = pf_osfp_find(&pf_osfp_list, &fp,
  	    PF_OSFP_MAXTTL_OFFSET)))
  		return (&fpresult->fp_oses);
  	return (NULL);
  }
  
  /* Match a fingerprint ID against a list of OSes */
  int
  pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
  {
  	struct pf_osfp_entry *entry;
  	int os_class, os_version, os_subtype;
  	int en_class, en_version, en_subtype;
  
  	if (os == PF_OSFP_ANY)
  		return (1);
  	if (list == NULL) {
  		DPFPRINTF("osfp no match against %x\n", os);
  		return (os == PF_OSFP_UNKNOWN);
  	}
  	PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
  	SLIST_FOREACH(entry, list, fp_entry) {
  		PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
  		if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
  		    (os_version == PF_OSFP_ANY || en_version == os_version) &&
  		    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
  			DPFPRINTF("osfp matched %s %s %s  %x==%x\n",
  			    entry->fp_class_nm, entry->fp_version_nm,
  			    entry->fp_subtype_nm, os, entry->fp_os);
  			return (1);
  		}
  	}
  	DPFPRINTF("fingerprint 0x%x didn't match\n", os);
  	return (0);
  }
  
  /* Initialize the OS fingerprint system */
  void
  pf_osfp_initialize(void)
  {
  	pool_init(&pf_osfp_entry_pl, sizeof(struct pf_osfp_entry), 0, 0, 0,
  	    "pfosfpen", &pool_allocator_nointr);
  	pool_init(&pf_osfp_pl, sizeof(struct pf_os_fingerprint), 0, 0, 0,
  	    "pfosfp", &pool_allocator_nointr);
  	SLIST_INIT(&pf_osfp_list);
  }
  
  #ifdef _LKM
  void
  pf_osfp_destroy(void)
  {
  	pf_osfp_flush();
  
  	pool_destroy(&pf_osfp_pl);
  	pool_destroy(&pf_osfp_entry_pl);
  }
  #endif
  
  /* Flush the fingerprint list */
  void
  pf_osfp_flush(void)
  {
  	struct pf_os_fingerprint *fp;
  	struct pf_osfp_entry *entry;
  
  	while ((fp = SLIST_FIRST(&pf_osfp_list))) {
  		SLIST_REMOVE_HEAD(&pf_osfp_list, fp_next);
  		while ((entry = SLIST_FIRST(&fp->fp_oses))) {
  			SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
  			pool_put(&pf_osfp_entry_pl, entry);
  		}
  		pool_put(&pf_osfp_pl, fp);
  	}
  }
  
  
  /* Add a fingerprint */
  int
  pf_osfp_add(struct pf_osfp_ioctl *fpioc)
  {
  	struct pf_os_fingerprint *fp, fpadd;
  	struct pf_osfp_entry *entry;
  
  	memset(&fpadd, 0, sizeof(fpadd));
  	fpadd.fp_tcpopts = fpioc->fp_tcpopts;
  	fpadd.fp_wsize = fpioc->fp_wsize;
  	fpadd.fp_psize = fpioc->fp_psize;
  	fpadd.fp_mss = fpioc->fp_mss;
  	fpadd.fp_flags = fpioc->fp_flags;
  	fpadd.fp_optcnt = fpioc->fp_optcnt;
  	fpadd.fp_wscale = fpioc->fp_wscale;
  	fpadd.fp_ttl = fpioc->fp_ttl;
  
  	DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
  	    "(TS=%s,M=%s%d,W=%s%d) %x\n",
  	    fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
  	    fpioc->fp_os.fp_subtype_nm,
  	    (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
  	    (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
  	    (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
  	    (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
  	    fpadd.fp_wsize,
  	    fpadd.fp_ttl,
  	    (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
  	    (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
  	    (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
  	    fpadd.fp_psize,
  	    (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
  	    (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
  	    (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
  	    (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
  	    fpadd.fp_mss,
  	    (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
  	    (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
  	    fpadd.fp_wscale,
  	    fpioc->fp_os.fp_os);
  
  
  	if ((fp = pf_osfp_find_exact(&pf_osfp_list, &fpadd))) {
  		 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
  			if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
  				return (EEXIST);
  		}
  		if ((entry = pool_get(&pf_osfp_entry_pl, PR_NOWAIT)) == NULL)
  			return (ENOMEM);
  	} else {
  		if ((fp = pool_get(&pf_osfp_pl, PR_NOWAIT)) == NULL)
  			return (ENOMEM);
  		memset(fp, 0, sizeof(*fp));
  		fp->fp_tcpopts = fpioc->fp_tcpopts;
  		fp->fp_wsize = fpioc->fp_wsize;
  		fp->fp_psize = fpioc->fp_psize;
  		fp->fp_mss = fpioc->fp_mss;
  		fp->fp_flags = fpioc->fp_flags;
  		fp->fp_optcnt = fpioc->fp_optcnt;
  		fp->fp_wscale = fpioc->fp_wscale;
  		fp->fp_ttl = fpioc->fp_ttl;
  		SLIST_INIT(&fp->fp_oses);
  		if ((entry = pool_get(&pf_osfp_entry_pl, PR_NOWAIT)) == NULL) {
  			pool_put(&pf_osfp_pl, fp);
  			return (ENOMEM);
  		}
  		pf_osfp_insert(&pf_osfp_list, fp);
  	}
  	memcpy(entry, &fpioc->fp_os, sizeof(*entry));
  
  	/* Make sure the strings are NUL terminated */
  	entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
  	entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
  	entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';
  
  	SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);
  
  #ifdef PFDEBUG
  	if ((fp = pf_osfp_validate()))
  		printf("Invalid fingerprint list\n");
  #endif /* PFDEBUG */
  	return (0);
  }
  
  
  /* Find a fingerprint in the list */
  struct pf_os_fingerprint *
  pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
      u_int8_t ttldiff)
  {
  	struct pf_os_fingerprint *f;
  
  #define MATCH_INT(_MOD, _DC, _field)					\
  	if ((f->fp_flags & _DC) == 0) {					\
  		if ((f->fp_flags & _MOD) == 0) {			\
  			if (f->_field != find->_field)			\
  				continue;				\
  		} else {						\
  			if (f->_field == 0 || find->_field % f->_field)	\
  				continue;				\
  		}							\
  	}
  
  	SLIST_FOREACH(f, list, fp_next) {
  		if (f->fp_tcpopts != find->fp_tcpopts ||
  		    f->fp_optcnt != find->fp_optcnt ||
  		    f->fp_ttl < find->fp_ttl ||
  		    f->fp_ttl - find->fp_ttl > ttldiff ||
  		    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
  		    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
  			continue;
  
  		MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
  		MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
  		MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
  		if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
  			if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
  				if (find->fp_mss == 0)
  					continue;
  
  /* Some "smart" NAT devices and DSL routers will tweak the MSS size and
   * will set it to whatever is suitable for the link type.
   */
  #define SMART_MSS	1460
  				if ((find->fp_wsize % find->fp_mss ||
  				    find->fp_wsize / find->fp_mss !=
  				    f->fp_wsize) &&
  				    (find->fp_wsize % SMART_MSS ||
  				    find->fp_wsize / SMART_MSS !=
  				    f->fp_wsize))
  					continue;
  			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
  				if (find->fp_mss == 0)
  					continue;
  
  #define MTUOFF	(sizeof(struct ip) + sizeof(struct tcphdr))
  #define SMART_MTU	(SMART_MSS + MTUOFF)
  				if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
  				    find->fp_wsize / (find->fp_mss + MTUOFF) !=
  				    f->fp_wsize) &&
  				    (find->fp_wsize % SMART_MTU ||
  				    find->fp_wsize / SMART_MTU !=
  				    f->fp_wsize))
  					continue;
  			} else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
  				if (f->fp_wsize == 0 || find->fp_wsize %
  				    f->fp_wsize)
  					continue;
  			} else {
  				if (f->fp_wsize != find->fp_wsize)
  					continue;
  			}
  		}
  		return (f);
  	}
  
  	return (NULL);
  }
  
  /* Find an exact fingerprint in the list */
  struct pf_os_fingerprint *
  pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
  {
  	struct pf_os_fingerprint *f;
  
  	SLIST_FOREACH(f, list, fp_next) {
  		if (f->fp_tcpopts == find->fp_tcpopts &&
  		    f->fp_wsize == find->fp_wsize &&
  		    f->fp_psize == find->fp_psize &&
  		    f->fp_mss == find->fp_mss &&
  		    f->fp_flags == find->fp_flags &&
  		    f->fp_optcnt == find->fp_optcnt &&
  		    f->fp_wscale == find->fp_wscale &&
  		    f->fp_ttl == find->fp_ttl)
  			return (f);
  	}
  
  	return (NULL);
  }
  
  /* Insert a fingerprint into the list */
  void
  pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
  {
  	struct pf_os_fingerprint *f, *prev = NULL;
  
  	/* XXX need to go semi tree based.  can key on tcp options */
  
  	SLIST_FOREACH(f, list, fp_next)
  		prev = f;
  	if (prev)
  		SLIST_INSERT_AFTER(prev, ins, fp_next);
  	else
  		SLIST_INSERT_HEAD(list, ins, fp_next);
  }
  
  /* Fill a fingerprint by its number (from an ioctl) */
  int
  pf_osfp_get(struct pf_osfp_ioctl *fpioc)
  {
  	struct pf_os_fingerprint *fp;
  	struct pf_osfp_entry *entry;
  	int num = fpioc->fp_getnum;
  	int i = 0;
  
  
  	memset(fpioc, 0, sizeof(*fpioc));
  	SLIST_FOREACH(fp, &pf_osfp_list, fp_next) {
  		SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
  			if (i++ == num) {
  				fpioc->fp_mss = fp->fp_mss;
  				fpioc->fp_wsize = fp->fp_wsize;
  				fpioc->fp_flags = fp->fp_flags;
  				fpioc->fp_psize = fp->fp_psize;
  				fpioc->fp_ttl = fp->fp_ttl;
  				fpioc->fp_wscale = fp->fp_wscale;
  				fpioc->fp_getnum = num;
  				memcpy(&fpioc->fp_os, entry,
  				    sizeof(fpioc->fp_os));
  				return (0);
  			}
  		}
  	}
  
  	return (EBUSY);
  }
  
  
  /* Validate that each signature is reachable */
  struct pf_os_fingerprint *
  pf_osfp_validate(void)
  {
  	struct pf_os_fingerprint *f, *f2, find;
  
  	SLIST_FOREACH(f, &pf_osfp_list, fp_next) {
  		memcpy(&find, f, sizeof(find));
  
  		/* We do a few MSS/th_win percolations to make things unique */
  		if (find.fp_mss == 0)
  			find.fp_mss = 128;
  		if (f->fp_flags & PF_OSFP_WSIZE_MSS)
  			find.fp_wsize *= find.fp_mss, 1;
  		else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
  			find.fp_wsize *= (find.fp_mss + 40);
  		else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
  			find.fp_wsize *= 2;
  		if (f != (f2 = pf_osfp_find(&pf_osfp_list, &find, 0))) {
  			if (f2)
  				printf("Found \"%s %s %s\" instead of "
  				    "\"%s %s %s\"\n",
  				    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
  				    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
  				    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
  				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
  				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
  				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
  			else
  				printf("Couldn't find \"%s %s %s\"\n",
  				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
  				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
  				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
  			return (f);
  		}
  	}
  	return (NULL);
  }
  