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 void *matchinfo,
  28                  int offset,
  29                  unsigned int protoff,
  30                  int *hotdrop)
  31 {
  32         struct ts_state state;
  33         struct xt_string_info *conf = (struct xt_string_info *) matchinfo;
  34
  35         memset(&state, 0, sizeof(struct ts_state));
  36
  37         return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
  38                              conf->to_offset, conf->config, &state)
  39                              != UINT_MAX) && !conf->invert;
  40 }
  41
  42 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *) m)
  43
  44 static int checkentry(const char *tablename,
  45                       const void *ip,
  46                       void *matchinfo,
  47                       unsigned int matchsize,
  48                       unsigned int hook_mask)
  49 {
  50         struct xt_string_info *conf = matchinfo;
  51         struct ts_config *ts_conf;
  52
  53         if (matchsize != XT_ALIGN(sizeof(struct xt_string_info)))
  54                 return 0;
  55
  56         /* Damn, can't handle this case properly with iptables... */
  57         if (conf->from_offset > conf->to_offset)
  58                 return 0;
  59
  60         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  61                                      GFP_KERNEL, TS_AUTOLOAD);
  62         if (IS_ERR(ts_conf))
  63                 return 0;
  64
  65         conf->config = ts_conf;
  66
  67         return 1;
  68 }
  69
  70 static void destroy(void *matchinfo, unsigned int matchsize)
  71 {
  72         textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config);
  73 }
  74
  75 static struct xt_match string_match = {
  76         .name           = "string",
  77         .match          = match,
  78         .checkentry     = checkentry,
  79         .destroy        = destroy,
  80         .me             = THIS_MODULE
  81 };
  82 static struct xt_match string6_match = {
  83         .name           = "string",
  84         .match          = match,
  85         .checkentry     = checkentry,
  86         .destroy        = destroy,
  87         .me             = THIS_MODULE
  88 };
  89
  90 static int __init init(void)
  91 {
  92         int ret;
  93
  94         ret = xt_register_match(AF_INET, &string_match);
  95         if (ret)
  96                 return ret;
  97         ret = xt_register_match(AF_INET6, &string6_match);
  98         if (ret)
  99                 xt_unregister_match(AF_INET, &string_match);
 100
 101         return ret;
 102 }
 103
 104 static void __exit fini(void)
 105 {
 106         xt_unregister_match(AF_INET, &string_match);
 107         xt_unregister_match(AF_INET6, &string6_match);
 108 }
 109
 110 module_init(init);
 111 module_exit(fini);