1// SPDX-License-Identifier: GPL-2.0-only
2/* String matching match for iptables
3 *
4 * (C) 2005 Pablo Neira Ayuso <pablo@eurodev.net>
5 */
6
7#include <linux/gfp.h>
8#include <linux/init.h>
9#include <linux/module.h>
10#include <linux/kernel.h>
11#include <linux/skbuff.h>
12#include <linux/netfilter/x_tables.h>
13#include <linux/netfilter/xt_string.h>
14#include <linux/textsearch.h>
15
16MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
17MODULE_DESCRIPTION("Xtables: string-based matching");
18MODULE_LICENSE("GPL");
19MODULE_ALIAS("ipt_string");
20MODULE_ALIAS("ip6t_string");
21MODULE_ALIAS("ebt_string");
22
23static bool
24string_mt(const struct sk_buff *skb, struct xt_action_param *par)
25{
26 const struct xt_string_info *conf = par->matchinfo;
27 bool invert;
28
29 invert = conf->u.v1.flags & XT_STRING_FLAG_INVERT;
30
31 return (skb_find_text(skb: (struct sk_buff *)skb, from: conf->from_offset,
32 to: conf->to_offset, config: conf->config)
33 != UINT_MAX) ^ invert;
34}
35
36#define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
37
38static int string_mt_check(const struct xt_mtchk_param *par)
39{
40 struct xt_string_info *conf = par->matchinfo;
41 struct ts_config *ts_conf;
42 int flags = TS_AUTOLOAD;
43
44 /* Damn, can't handle this case properly with iptables... */
45 if (conf->from_offset > conf->to_offset)
46 return -EINVAL;
47 if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
48 return -EINVAL;
49 if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
50 return -EINVAL;
51 if (conf->u.v1.flags &
52 ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
53 return -EINVAL;
54 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
55 flags |= TS_IGNORECASE;
56 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
57 GFP_KERNEL, flags);
58 if (IS_ERR(ptr: ts_conf))
59 return PTR_ERR(ptr: ts_conf);
60
61 conf->config = ts_conf;
62 return 0;
63}
64
65static void string_mt_destroy(const struct xt_mtdtor_param *par)
66{
67 textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
68}
69
70static struct xt_match xt_string_mt_reg __read_mostly = {
71 .name = "string",
72 .revision = 1,
73 .family = NFPROTO_UNSPEC,
74 .checkentry = string_mt_check,
75 .match = string_mt,
76 .destroy = string_mt_destroy,
77 .matchsize = sizeof(struct xt_string_info),
78 .usersize = offsetof(struct xt_string_info, config),
79 .me = THIS_MODULE,
80};
81
82static int __init string_mt_init(void)
83{
84 return xt_register_match(target: &xt_string_mt_reg);
85}
86
87static void __exit string_mt_exit(void)
88{
89 xt_unregister_match(target: &xt_string_mt_reg);
90}
91
92module_init(string_mt_init);
93module_exit(string_mt_exit);
94

source code of linux/net/netfilter/xt_string.c