LXR linux/net/netfilter/xt

   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
  18MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
  19MODULE_DESCRIPTION("Xtables: string-based matching");
  20MODULE_LICENSE("GPL");
  21MODULE_ALIAS("ipt_string");
  22MODULE_ALIAS("ip6t_string");
  23
  24static bool
  25string_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
  43static bool string_mt_check(const struct xt_mtchk_param *par)
  44{
  45        struct xt_string_info *conf = par->matchinfo;
  46        struct ts_config *ts_conf;
  47        int flags = TS_AUTOLOAD;
  48
  49        /* Damn, can't handle this case properly with iptables... */
  50        if (conf->from_offset > conf->to_offset)
  51                return false;
  52        if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
  53                return false;
  54        if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
  55                return false;
  56        if (par->match->revision == 1) {
  57                if (conf->u.v1.flags &
  58                    ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
  59                        return false;
  60                if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
  61                        flags |= TS_IGNORECASE;
  62        }
  63        ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  64                                     GFP_KERNEL, flags);
  65        if (IS_ERR(ts_conf))
  66                return false;
  67
  68        conf->config = ts_conf;
  69
  70        return true;
  71}
  72
  73static void string_mt_destroy(const struct xt_mtdtor_param *par)
  74{
  75        textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
  76}
  77
  78static struct xt_match xt_string_mt_reg[] __read_mostly = {
  79        {
  80                .name           = "string",
  81                .revision       = 0,
  82                .family         = NFPROTO_UNSPEC,
  83                .checkentry     = string_mt_check,
  84                .match          = string_mt,
  85                .destroy        = string_mt_destroy,
  86                .matchsize      = sizeof(struct xt_string_info),
  87                .me             = THIS_MODULE
  88        },
  89        {
  90                .name           = "string",
  91                .revision       = 1,
  92                .family         = NFPROTO_UNSPEC,
  93                .checkentry     = string_mt_check,
  94                .match          = string_mt,
  95                .destroy        = string_mt_destroy,
  96                .matchsize      = sizeof(struct xt_string_info),
  97                .me             = THIS_MODULE
  98        },
  99};
 100
 101static int __init string_mt_init(void)
 102{
 103        return xt_register_matches(xt_string_mt_reg,
 104                                   ARRAY_SIZE(xt_string_mt_reg));
 105}
 106
 107static void __exit string_mt_exit(void)
 108{
 109        xt_unregister_matches(xt_string_mt_reg, ARRAY_SIZE(xt_string_mt_reg));
 110}
 111
 112module_init(string_mt_init);
 113module_exit(string_mt_exit);
 114