libxt_osf.c revision d09b6d591ca7d7d7575cb6aa20384c9830f777ab 
1/*
2 * Copyright (c) 2003+ Evgeniy Polyakov <zbr@ioremap.net>
3 *
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 */
19
20/*
21 * xtables interface for OS fingerprint matching module.
22 */
23#include <stdbool.h>
24#include <stdio.h>
25#include <netdb.h>
26#include <string.h>
27#include <stdlib.h>
28#include <getopt.h>
29#include <ctype.h>
30
31#include <linux/types.h>
32
33#include <xtables.h>
34
35#include <netinet/ip.h>
36#include <netinet/tcp.h>
37
38#include <linux/netfilter/xt_osf.h>
39
40static void osf_help(void)
41{
42	printf("OS fingerprint match options:\n"
43		"[!] --genre string     Match a OS genre by passive fingerprinting.\n"
44		"--ttl level            Use some TTL check extensions to determine OS:\n"
45		"       0                       true ip and fingerprint TTL comparison. Works for LAN.\n"
46		"       1                       check if ip TTL is less than fingerprint one. Works for global addresses.\n"
47		"       2                       do not compare TTL at all. Allows to detect NMAP, but can produce false results.\n"
48		"--log level            Log determined genres into dmesg even if they do not match desired one:\n"
49		"       0                       log all matched or unknown signatures.\n"
50		"       1                       log only first one.\n"
51		"       2                       log all known matched signatures.\n"
52		);
53}
54
55
56static const struct option osf_opts[] = {
57	{.name = "genre", .has_arg = true, .val = '1'},
58	{.name = "ttl",   .has_arg = true, .val = '2'},
59	{.name = "log",   .has_arg = true, .val = '3'},
60	XT_GETOPT_TABLEEND,
61};
62
63
64static void osf_parse_string(const char *s, struct xt_osf_info *info)
65{
66	if (strlen(s) < MAXGENRELEN)
67		strcpy(info->genre, s);
68	else
69		xtables_error(PARAMETER_PROBLEM,
70			      "Genre string too long `%s' [%zd], max=%d",
71			      s, strlen(s), MAXGENRELEN);
72}
73
74static int osf_parse(int c, char **argv, int invert, unsigned int *flags,
75      			const void *entry,
76      			struct xt_entry_match **match)
77{
78	struct xt_osf_info *info = (struct xt_osf_info *)(*match)->data;
79
80	switch(c) {
81		case '1': /* --genre */
82			if (*flags & XT_OSF_GENRE)
83				xtables_error(PARAMETER_PROBLEM,
84					      "Can't specify multiple genre parameter");
85			xtables_check_inverse(optarg, &invert, &optind, 0, argv);
86			osf_parse_string(argv[optind-1], info);
87			if (invert)
88				info->flags |= XT_OSF_INVERT;
89			info->len=strlen(info->genre);
90			*flags |= XT_OSF_GENRE;
91			break;
92		case '2': /* --ttl */
93			if (*flags & XT_OSF_TTL)
94				xtables_error(PARAMETER_PROBLEM,
95					      "Can't specify multiple ttl parameter");
96			*flags |= XT_OSF_TTL;
97			info->flags |= XT_OSF_TTL;
98			if (!xtables_strtoui(argv[optind-1], NULL, &info->ttl, 0, 2))
99				xtables_error(PARAMETER_PROBLEM, "TTL parameter is too big");
100			break;
101		case '3': /* --log */
102			if (*flags & XT_OSF_LOG)
103				xtables_error(PARAMETER_PROBLEM,
104					      "Can't specify multiple log parameter");
105			*flags |= XT_OSF_LOG;
106			if (!xtables_strtoui(argv[optind-1], NULL, &info->loglevel, 0, 2))
107				xtables_error(PARAMETER_PROBLEM, "Log level parameter is too big");
108			info->flags |= XT_OSF_LOG;
109			break;
110	}
111
112	return 1;
113}
114
115static void osf_final_check(unsigned int flags)
116{
117	if (!flags)
118		xtables_error(PARAMETER_PROBLEM,
119			      "OS fingerprint match: You must specify `--genre'");
120}
121
122static void osf_print(const void *ip, const struct xt_entry_match *match, int numeric)
123{
124	const struct xt_osf_info *info = (const struct xt_osf_info*) match->data;
125
126	printf("OS fingerprint match %s%s ", (info->flags & XT_OSF_INVERT) ? "! " : "", info->genre);
127}
128
129static void osf_save(const void *ip, const struct xt_entry_match *match)
130{
131	const struct xt_osf_info *info = (const struct xt_osf_info*) match->data;
132
133	printf("--genre %s%s ", (info->flags & XT_OSF_INVERT) ? "! ": "", info->genre);
134}
135
136static struct xtables_match osf_match = {
137	.name		= "osf",
138	.version	= XTABLES_VERSION,
139	.size		= XT_ALIGN(sizeof(struct xt_osf_info)),
140	.userspacesize	= XT_ALIGN(sizeof(struct xt_osf_info)),
141	.help		= osf_help,
142	.parse		= osf_parse,
143	.print		= osf_print,
144	.final_check	= osf_final_check,
145	.save		= osf_save,
146	.extra_opts	= osf_opts,
147	.family		= NFPROTO_IPV4
148};
149
150void _init(void)
151{
152	xtables_register_match(&osf_match);
153}
154