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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/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 bool 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                   bool *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 bool 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 false;
  57         if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
  58                 return false;
  59         if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
  60                 return false;
  61         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  62                                      GFP_KERNEL, TS_AUTOLOAD);
  63         if (IS_ERR(ts_conf))
  64                 return false;
  65
  66         conf->config = ts_conf;
  67
  68         return true;
  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);