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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 */
19
20 /*
21 * xtables interface for OS fingerprint matching module.
22 */
23 #include <stdio.h>
24 #include <string.h>
25 #include <xtables.h>
26 #include <netinet/ip.h>
27 #include <netinet/tcp.h>
28 #include <linux/netfilter/xt_osf.h>
29
30 enum {
31 O_GENRE = 0,
32 O_TTL,
33 O_LOGLEVEL,
34 };
35
osf_help(void)36 static void osf_help(void)
37 {
38 printf("OS fingerprint match options:\n"
39 "[!] --genre string Match a OS genre by passive fingerprinting.\n"
40 "--ttl level Use some TTL check extensions to determine OS:\n"
41 " 0 true ip and fingerprint TTL comparison. Works for LAN.\n"
42 " 1 check if ip TTL is less than fingerprint one. Works for global addresses.\n"
43 " 2 do not compare TTL at all. This allows NMAP detection, but can produce false results.\n"
44 "--log level Log determined genres into dmesg even if they do not match desired one:\n"
45 " 0 log all matched or unknown signatures.\n"
46 " 1 log only first one.\n"
47 " 2 log all known matched signatures.\n"
48 );
49 }
50
51 #define s struct xt_osf_info
52 static const struct xt_option_entry osf_opts[] = {
53 {.name = "genre", .id = O_GENRE, .type = XTTYPE_STRING,
54 .flags = XTOPT_MAND | XTOPT_INVERT | XTOPT_PUT,
55 XTOPT_POINTER(s, genre)},
56 {.name = "ttl", .id = O_TTL, .type = XTTYPE_UINT32,
57 .flags = XTOPT_PUT, XTOPT_POINTER(s, ttl), .min = 0, .max = 2},
58 {.name = "log", .id = O_LOGLEVEL, .type = XTTYPE_UINT32,
59 .flags = XTOPT_PUT, XTOPT_POINTER(s, loglevel), .min = 0, .max = 2},
60 XTOPT_TABLEEND,
61 };
62 #undef s
63
osf_parse(struct xt_option_call * cb)64 static void osf_parse(struct xt_option_call *cb)
65 {
66 struct xt_osf_info *info = cb->data;
67
68 xtables_option_parse(cb);
69 switch (cb->entry->id) {
70 case O_GENRE:
71 if (cb->invert)
72 info->flags |= XT_OSF_INVERT;
73 info->len = strlen(info->genre);
74 break;
75 case O_TTL:
76 info->flags |= XT_OSF_TTL;
77 break;
78 case O_LOGLEVEL:
79 info->flags |= XT_OSF_LOG;
80 break;
81 }
82 }
83
osf_print(const void * ip,const struct xt_entry_match * match,int numeric)84 static void osf_print(const void *ip, const struct xt_entry_match *match, int numeric)
85 {
86 const struct xt_osf_info *info = (const struct xt_osf_info*) match->data;
87
88 printf(" OS fingerprint match %s%s", (info->flags & XT_OSF_INVERT) ? "! " : "", info->genre);
89 }
90
osf_save(const void * ip,const struct xt_entry_match * match)91 static void osf_save(const void *ip, const struct xt_entry_match *match)
92 {
93 const struct xt_osf_info *info = (const struct xt_osf_info*) match->data;
94
95 if (info->flags & XT_OSF_INVERT)
96 printf(" !");
97
98 printf(" --genre %s", info->genre);
99 if (info->flags & XT_OSF_TTL)
100 printf(" --ttl %u", info->ttl);
101 if (info->flags & XT_OSF_LOG)
102 printf(" --log %u", info->loglevel);
103 }
104
105 static struct xtables_match osf_match = {
106 .name = "osf",
107 .version = XTABLES_VERSION,
108 .size = XT_ALIGN(sizeof(struct xt_osf_info)),
109 .userspacesize = XT_ALIGN(sizeof(struct xt_osf_info)),
110 .help = osf_help,
111 .x6_parse = osf_parse,
112 .print = osf_print,
113 .save = osf_save,
114 .x6_options = osf_opts,
115 .family = NFPROTO_IPV4,
116 };
117
_init(void)118 void _init(void)
119 {
120 xtables_register_match(&osf_match);
121 }
122