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
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
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
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
82 static int __init string_mt_init(void)
83 {
84 return xt_register_match(&xt_string_mt_reg);
85 }
86
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
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