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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 | ||
19 | MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>"); | |
20 | MODULE_DESCRIPTION("Xtables: string-based matching"); | |
21 | MODULE_LICENSE("GPL"); | |
22 | MODULE_ALIAS("ipt_string"); | |
23 | MODULE_ALIAS("ip6t_string"); | |
24 | ||
25 | static bool | |
26 | string_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 | ||
40 | static 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 | ||
67 | static void string_mt_destroy(const struct xt_mtdtor_param *par) | |
68 | { | |
69 | textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config); | |
70 | } | |
71 | ||
72 | static 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 | ||
83 | static int __init string_mt_init(void) | |
84 | { | |
85 | return xt_register_match(&xt_string_mt_reg); | |
86 | } | |
87 | ||
88 | static void __exit string_mt_exit(void) | |
89 | { | |
90 | xt_unregister_match(&xt_string_mt_reg); | |
91 | } | |
92 | ||
93 | module_init(string_mt_init); | |
94 | module_exit(string_mt_exit); |