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/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
  19MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
  20MODULE_DESCRIPTION("Xtables: string-based matching");
  21MODULE_LICENSE("GPL");
  22MODULE_ALIAS("ipt_string");
  23MODULE_ALIAS("ip6t_string");
  24
  25static bool
  26string_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
  40static 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
  67static void string_mt_destroy(const struct xt_mtdtor_param *par)
  68{
  69        textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
  70}
  71
  72static 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
  84static int __init string_mt_init(void)
  85{
  86        return xt_register_match(&xt_string_mt_reg);
  87}
  88
  89static void __exit string_mt_exit(void)
  90{
  91        xt_unregister_match(&xt_string_mt_reg);
  92}
  93
  94module_init(string_mt_init);
  95module_exit(string_mt_exit);
  96