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