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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, const struct xt_match_param *par)
  27 {
  28         const struct xt_string_info *conf = par->matchinfo;
  29         struct ts_state state;
  30         int invert;
  31
  32         memset(&state, 0, sizeof(struct ts_state));
  33
  34         invert = (par->match->revision == 0 ? conf->u.v0.invert :
  35                                     conf->u.v1.flags & XT_STRING_FLAG_INVERT);
  36
  37         return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
  38                              conf->to_offset, conf->config, &state)
  39                              != UINT_MAX) ^ invert;
  40 }
  41
  42 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
  43
  44 static bool string_mt_check(const struct xt_mtchk_param *par)
  45 {
  46         struct xt_string_info *conf = par->matchinfo;
  47         struct ts_config *ts_conf;
  48         int flags = TS_AUTOLOAD;
  49
  50         /* Damn, can't handle this case properly with iptables... */
  51         if (conf->from_offset > conf->to_offset)
  52                 return false;
  53         if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
  54                 return false;
  55         if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
  56                 return false;
  57         if (par->match->revision == 1) {
  58                 if (conf->u.v1.flags &
  59                     ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
  60                         return false;
  61                 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
  62                         flags |= TS_IGNORECASE;
  63         }
  64         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  65                                      GFP_KERNEL, flags);
  66         if (IS_ERR(ts_conf))
  67                 return false;
  68
  69         conf->config = ts_conf;
  70
  71         return true;
  72 }
  73
  74 static void string_mt_destroy(const struct xt_mtdtor_param *par)
  75 {
  76         textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
  77 }
  78
  79 static struct xt_match xt_string_mt_reg[] __read_mostly = {
  80         {
  81                 .name           = "string",
  82                 .revision       = 0,
  83                 .family         = NFPROTO_UNSPEC,
  84                 .checkentry     = string_mt_check,
  85                 .match          = string_mt,
  86                 .destroy        = string_mt_destroy,
  87                 .matchsize      = sizeof(struct xt_string_info),
  88                 .me             = THIS_MODULE
  89         },
  90         {
  91                 .name           = "string",
  92                 .revision       = 1,
  93                 .family         = NFPROTO_UNSPEC,
  94                 .checkentry     = string_mt_check,
  95                 .match          = string_mt,
  96                 .destroy        = string_mt_destroy,
  97                 .matchsize      = sizeof(struct xt_string_info),
  98                 .me             = THIS_MODULE
  99         },
 100 };
 101
 102 static int __init string_mt_init(void)
 103 {
 104         return xt_register_matches(xt_string_mt_reg,
 105                                    ARRAY_SIZE(xt_string_mt_reg));
 106 }
 107
 108 static void __exit string_mt_exit(void)
 109 {
 110         xt_unregister_matches(xt_string_mt_reg, ARRAY_SIZE(xt_string_mt_reg));
 111 }
 112
 113 module_init(string_mt_init);
 114 module_exit(string_mt_exit);