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 matchsize,
  50                       unsigned int hook_mask)
  51 {
  52         struct xt_string_info *conf = matchinfo;
  53         struct ts_config *ts_conf;
  54
  55         /* Damn, can't handle this case properly with iptables... */
  56         if (conf->from_offset > conf->to_offset)
  57                 return 0;
  58         if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
  59                 return 0;
  60         if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
  61                 return 0;
  62         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  63                                      GFP_KERNEL, TS_AUTOLOAD);
  64         if (IS_ERR(ts_conf))
  65                 return 0;
  66
  67         conf->config = ts_conf;
  68
  69         return 1;
  70 }
  71
  72 static void destroy(const struct xt_match *match, void *matchinfo,
  73                     unsigned int matchsize)
  74 {
  75         textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config);
  76 }
  77
  78 static struct xt_match string_match = {
  79         .name           = "string",
  80         .match          = match,
  81         .matchsize      = sizeof(struct xt_string_info),
  82         .checkentry     = checkentry,
  83         .destroy        = destroy,
  84         .family         = AF_INET,
  85         .me             = THIS_MODULE
  86 };
  87 static struct xt_match string6_match = {
  88         .name           = "string",
  89         .match          = match,
  90         .matchsize      = sizeof(struct xt_string_info),
  91         .checkentry     = checkentry,
  92         .destroy        = destroy,
  93         .family         = AF_INET6,
  94         .me             = THIS_MODULE
  95 };
  96
  97 static int __init xt_string_init(void)
  98 {
  99         int ret;
 100
 101         ret = xt_register_match(&string_match);
 102         if (ret)
 103                 return ret;
 104         ret = xt_register_match(&string6_match);
 105         if (ret)
 106                 xt_unregister_match(&string_match);
 107
 108         return ret;
 109 }
 110
 111 static void __exit xt_string_fini(void)
 112 {
 113         xt_unregister_match(&string_match);
 114         xt_unregister_match(&string6_match);
 115 }
 116
 117 module_init(xt_string_init);
 118 module_exit(xt_string_fini);