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[linux-2.6] / net / netfilter / xt_string.c
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/init.h>
11 #include <linux/module.h>
12 #include <linux/kernel.h>
13 #include <linux/skbuff.h>
14 #include <linux/netfilter/x_tables.h>
15 #include <linux/netfilter/xt_string.h>
16 #include <linux/textsearch.h>
17
18 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
19 MODULE_DESCRIPTION("IP tables string match module");
20 MODULE_LICENSE("GPL");
21 MODULE_ALIAS("ipt_string");
22 MODULE_ALIAS("ip6t_string");
23
24 static int match(const struct sk_buff *skb,
25                  const struct net_device *in,
26                  const struct net_device *out,
27                  const struct xt_match *match,
28                  const void *matchinfo,
29                  int offset,
30                  unsigned int protoff,
31                  int *hotdrop)
32 {
33         const struct xt_string_info *conf = matchinfo;
34         struct ts_state state;
35
36         memset(&state, 0, sizeof(struct ts_state));
37
38         return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
39                              conf->to_offset, conf->config, &state)
40                              != UINT_MAX) ^ conf->invert;
41 }
42
43 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *) m)
44
45 static int checkentry(const char *tablename,
46                       const void *ip,
47                       const struct xt_match *match,
48                       void *matchinfo,
49                       unsigned int hook_mask)
50 {
51         struct xt_string_info *conf = matchinfo;
52         struct ts_config *ts_conf;
53
54         /* Damn, can't handle this case properly with iptables... */
55         if (conf->from_offset > conf->to_offset)
56                 return 0;
57         if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
58                 return 0;
59         if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
60                 return 0;
61         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
62                                      GFP_KERNEL, TS_AUTOLOAD);
63         if (IS_ERR(ts_conf))
64                 return 0;
65
66         conf->config = ts_conf;
67
68         return 1;
69 }
70
71 static void destroy(const struct xt_match *match, void *matchinfo)
72 {
73         textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config);
74 }
75
76 static struct xt_match xt_string_match[] = {
77         {
78                 .name           = "string",
79                 .family         = AF_INET,
80                 .checkentry     = checkentry,
81                 .match          = match,
82                 .destroy        = destroy,
83                 .matchsize      = sizeof(struct xt_string_info),
84                 .me             = THIS_MODULE
85         },
86         {
87                 .name           = "string",
88                 .family         = AF_INET6,
89                 .checkentry     = checkentry,
90                 .match          = match,
91                 .destroy        = destroy,
92                 .matchsize      = sizeof(struct xt_string_info),
93                 .me             = THIS_MODULE
94         },
95 };
96
97 static int __init xt_string_init(void)
98 {
99         return xt_register_matches(xt_string_match, ARRAY_SIZE(xt_string_match));
100 }
101
102 static void __exit xt_string_fini(void)
103 {
104         xt_unregister_matches(xt_string_match, ARRAY_SIZE(xt_string_match));
105 }
106
107 module_init(xt_string_init);
108 module_exit(xt_string_fini);