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("Xtables: string-based matching");
  20 MODULE_LICENSE("GPL");
  21 MODULE_ALIAS("ipt_string");
  22 MODULE_ALIAS("ip6t_string");
  23
  24 static bool
  25 string_mt(const struct sk_buff *skb, const struct net_device *in,
  26           const struct net_device *out, const struct xt_match *match,
  27           const void *matchinfo, int offset, unsigned int protoff,
  28           bool *hotdrop)
  29 {
  30         const struct xt_string_info *conf = matchinfo;
  31         struct ts_state state;
  32
  33         memset(&state, 0, sizeof(struct ts_state));
  34
  35         return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
  36                              conf->to_offset, conf->config, &state)
  37                              != UINT_MAX) ^ conf->invert;
  38 }
  39
  40 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
  41
  42 static bool
  43 string_mt_check(const char *tablename, const void *ip,
  44                 const struct xt_match *match, void *matchinfo,
  45                 unsigned int hook_mask)
  46 {
  47         struct xt_string_info *conf = matchinfo;
  48         struct ts_config *ts_conf;
  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         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  58                                      GFP_KERNEL, TS_AUTOLOAD);
  59         if (IS_ERR(ts_conf))
  60                 return false;
  61
  62         conf->config = ts_conf;
  63
  64         return true;
  65 }
  66
  67 static void string_mt_destroy(const struct xt_match *match, void *matchinfo)
  68 {
  69         textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config);
  70 }
  71
  72 static struct xt_match string_mt_reg[] __read_mostly = {
  73         {
  74                 .name           = "string",
  75                 .family         = AF_INET,
  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                 .name           = "string",
  84                 .family         = AF_INET6,
  85                 .checkentry     = string_mt_check,
  86                 .match          = string_mt,
  87                 .destroy        = string_mt_destroy,
  88                 .matchsize      = sizeof(struct xt_string_info),
  89                 .me             = THIS_MODULE
  90         },
  91 };
  92
  93 static int __init string_mt_init(void)
  94 {
  95         return xt_register_matches(string_mt_reg, ARRAY_SIZE(string_mt_reg));
  96 }
  97
  98 static void __exit string_mt_exit(void)
  99 {
 100         xt_unregister_matches(string_mt_reg, ARRAY_SIZE(string_mt_reg));
 101 }
 102
 103 module_init(string_mt_init);
 104 module_exit(string_mt_exit);