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 
16 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
17 MODULE_DESCRIPTION("Xtables: string-based matching");
18 MODULE_LICENSE("GPL");
19 MODULE_ALIAS("ipt_string");
20 MODULE_ALIAS("ip6t_string");
21 MODULE_ALIAS("ebt_string");
22 
23 static bool
string_mt(const struct sk_buff * skb,struct xt_action_param * par)24 string_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((struct sk_buff *)skb, conf->from_offset,
32 			     conf->to_offset, conf->config)
33 			     != UINT_MAX) ^ invert;
34 }
35 
36 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
37 
string_mt_check(const struct xt_mtchk_param * par)38 static 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(ts_conf))
59 		return PTR_ERR(ts_conf);
60 
61 	conf->config = ts_conf;
62 	return 0;
63 }
64 
string_mt_destroy(const struct xt_mtdtor_param * par)65 static void string_mt_destroy(const struct xt_mtdtor_param *par)
66 {
67 	textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
68 }
69 
70 static 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 
string_mt_init(void)82 static int __init string_mt_init(void)
83 {
84 	return xt_register_match(&xt_string_mt_reg);
85 }
86 
string_mt_exit(void)87 static void __exit string_mt_exit(void)
88 {
89 	xt_unregister_match(&xt_string_mt_reg);
90 }
91 
92 module_init(string_mt_init);
93 module_exit(string_mt_exit);
94