1 /* String matching match for iptables
2 *
3 * (C) 2005 Pablo Neira Ayuso <pablo@eurodev.net>
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 version 2 as
7 * published by the Free Software Foundation.
8 */
9
10 #include <linux/init.h>
11 #include <linux/module.h>
12 #include <linux/kernel.h>
13 #include <linux/skbuff.h>
14 #include <linux/netfilter/x_tables.h>
15 #include <linux/netfilter/xt_string.h>
16 #include <linux/textsearch.h>
17
18 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
19 MODULE_DESCRIPTION("Xtables: string-based matching");
20 MODULE_LICENSE("GPL");
21 MODULE_ALIAS("ipt_string");
22 MODULE_ALIAS("ip6t_string");
23
24 static bool
string_mt(const struct sk_buff * skb,const struct xt_match_param * par)25 string_mt(const struct sk_buff *skb, const struct xt_match_param *par)
26 {
27 const struct xt_string_info *conf = par->matchinfo;
28 struct ts_state state;
29 int invert;
30
31 memset(&state, 0, sizeof(struct ts_state));
32
33 invert = (par->match->revision == 0 ? conf->u.v0.invert :
34 conf->u.v1.flags & XT_STRING_FLAG_INVERT);
35
36 return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
37 conf->to_offset, conf->config, &state)
38 != UINT_MAX) ^ invert;
39 }
40
41 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
42
string_mt_check(const struct xt_mtchk_param * par)43 static bool string_mt_check(const struct xt_mtchk_param *par)
44 {
45 struct xt_string_info *conf = par->matchinfo;
46 struct ts_config *ts_conf;
47 int flags = TS_AUTOLOAD;
48
49 /* Damn, can't handle this case properly with iptables... */
50 if (conf->from_offset > conf->to_offset)
51 return false;
52 if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
53 return false;
54 if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
55 return false;
56 if (par->match->revision == 1) {
57 if (conf->u.v1.flags &
58 ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
59 return false;
60 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
61 flags |= TS_IGNORECASE;
62 }
63 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
64 GFP_KERNEL, flags);
65 if (IS_ERR(ts_conf))
66 return false;
67
68 conf->config = ts_conf;
69
70 return true;
71 }
72
string_mt_destroy(const struct xt_mtdtor_param * par)73 static void string_mt_destroy(const struct xt_mtdtor_param *par)
74 {
75 textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
76 }
77
78 static struct xt_match xt_string_mt_reg[] __read_mostly = {
79 {
80 .name = "string",
81 .revision = 0,
82 .family = NFPROTO_UNSPEC,
83 .checkentry = string_mt_check,
84 .match = string_mt,
85 .destroy = string_mt_destroy,
86 .matchsize = sizeof(struct xt_string_info),
87 .me = THIS_MODULE
88 },
89 {
90 .name = "string",
91 .revision = 1,
92 .family = NFPROTO_UNSPEC,
93 .checkentry = string_mt_check,
94 .match = string_mt,
95 .destroy = string_mt_destroy,
96 .matchsize = sizeof(struct xt_string_info),
97 .me = THIS_MODULE
98 },
99 };
100
string_mt_init(void)101 static int __init string_mt_init(void)
102 {
103 return xt_register_matches(xt_string_mt_reg,
104 ARRAY_SIZE(xt_string_mt_reg));
105 }
106
string_mt_exit(void)107 static void __exit string_mt_exit(void)
108 {
109 xt_unregister_matches(xt_string_mt_reg, ARRAY_SIZE(xt_string_mt_reg));
110 }
111
112 module_init(string_mt_init);
113 module_exit(string_mt_exit);
114