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