Add Michal Zalewski's p0f v2 style passive OS fingerprinting to PF.

Exposes the source IP's operating system to the filter language.
Interesting policy decisions are now enforceable:
.	block proto tcp from any os SCO
.	block proto tcp from any os Windows to any port smtp
.	rdr ... from any os "Windows 98" to port WWW -> 127.0.0.1 port 8001

1 files changed, 507 insertions, 0 deletions

diff --git a/sys/net/pf_osfp.c b/sys/net/pf_osfp.c
new file mode 100644
index 00000000000..c72914aaba1
--- /dev/null
+++ b/sys/net/pf_osfp.c
@@ -0,0 +1,507 @@
+/*	$OpenBSD: pf_osfp.c,v 1.1 2003/08/21 19:12:08 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.
+ *
+ */
+
+#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>
+# 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 <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;
+	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 = (caddr_t)tcp + sizeof(*tcp);
+	for (; cnt > 0; cnt -= optlen, optp += optlen) {
+		fp.fp_optcnt++;
+		if (*optp == TCPOPT_EOL)
+			break;
+		else 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", NULL);
+	pool_init(&pf_osfp_pl, sizeof(struct pf_os_fingerprint), 0, 0, 0,
+	    "pfosfp", NULL);
+	SLIST_INIT(&pf_osfp_list);
+}
+
+/* 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 ||
+				    find->fp_wsize % find->fp_mss ||
+				    find->fp_wsize / find->fp_mss !=
+				    f->fp_wsize)
+					continue;
+			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
+				if (find->fp_mss == 0 ||
+				    find->fp_wsize % (find->fp_mss + 40) ||
+				    find->fp_wsize / (find->fp_mss + 40) !=
+				    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);
+}