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 xt_match_param *par)
  26 {
  27         const struct xt_string_info *conf = par->matchinfo;
  28         struct ts_state state;
  29         int invert;
  30
  31         memset(&state, 0, sizeof(struct ts_state));
  32
  33         invert = (par->match->revision == 0 ? conf->u.v0.invert :
  34                                     conf->u.v1.flags & XT_STRING_FLAG_INVERT);
  35
  36         return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
  37                              conf->to_offset, conf->config, &state)
  38                              != UINT_MAX) ^ invert;
  39 }
  40
  41 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
  42
  43 static bool
  44 string_mt_check(const char *tablename, const void *ip,
  45                 const struct xt_match *match, void *matchinfo,
  46                 unsigned int hook_mask)
  47 {
  48         struct xt_string_info *conf = matchinfo;
  49         struct ts_config *ts_conf;
  50         int flags = TS_AUTOLOAD;
  51
  52         /* Damn, can't handle this case properly with iptables... */
  53         if (conf->from_offset > conf->to_offset)
  54                 return false;
  55         if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
  56                 return false;
  57         if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
  58                 return false;
  59         if (match->revision == 1) {
  60                 if (conf->u.v1.flags &
  61                     ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
  62                         return false;
  63                 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
  64                         flags |= TS_IGNORECASE;
  65         }
  66         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  67                                      GFP_KERNEL, flags);
  68         if (IS_ERR(ts_conf))
  69                 return false;
  70
  71         conf->config = ts_conf;
  72
  73         return true;
  74 }
  75
  76 static void string_mt_destroy(const struct xt_match *match, void *matchinfo)
  77 {
  78         textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config);
  79 }
  80
  81 static struct xt_match xt_string_mt_reg[] __read_mostly = {
  82         {
  83                 .name           = "string",
  84                 .revision       = 0,
  85                 .family         = NFPROTO_UNSPEC,
  86                 .checkentry     = string_mt_check,
  87                 .match          = string_mt,
  88                 .destroy        = string_mt_destroy,
  89                 .matchsize      = sizeof(struct xt_string_info),
  90                 .me             = THIS_MODULE
  91         },
  92         {
  93                 .name           = "string",
  94                 .revision       = 1,
  95                 .family         = NFPROTO_UNSPEC,
  96                 .checkentry     = string_mt_check,
  97                 .match          = string_mt,
  98                 .destroy        = string_mt_destroy,
  99                 .matchsize      = sizeof(struct xt_string_info),
 100                 .me             = THIS_MODULE
 101         },
 102 };
 103
 104 static int __init string_mt_init(void)
 105 {
 106         return xt_register_matches(xt_string_mt_reg,
 107                                    ARRAY_SIZE(xt_string_mt_reg));
 108 }
 109
 110 static void __exit string_mt_exit(void)
 111 {
 112         xt_unregister_matches(xt_string_mt_reg, ARRAY_SIZE(xt_string_mt_reg));
 113 }
 114
 115 module_init(string_mt_init);
 116 module_exit(string_mt_exit);