linux/net/netfilter/xt_string.c
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   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        struct ts_state state;
  30        bool invert;
  31
  32        memset(&state, 0, sizeof(struct ts_state));
  33        invert = conf->u.v1.flags & XT_STRING_FLAG_INVERT;
  34
  35        return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
  36                             conf->to_offset, conf->config, &state)
  37                             != UINT_MAX) ^ invert;
  38}
  39
  40#define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
  41
  42static int string_mt_check(const struct xt_mtchk_param *par)
  43{
  44        struct xt_string_info *conf = par->matchinfo;
  45        struct ts_config *ts_conf;
  46        int flags = TS_AUTOLOAD;
  47
  48        /* Damn, can't handle this case properly with iptables... */
  49        if (conf->from_offset > conf->to_offset)
  50                return -EINVAL;
  51        if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
  52                return -EINVAL;
  53        if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
  54                return -EINVAL;
  55        if (conf->u.v1.flags &
  56            ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
  57                return -EINVAL;
  58        if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
  59                flags |= TS_IGNORECASE;
  60        ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  61                                     GFP_KERNEL, flags);
  62        if (IS_ERR(ts_conf))
  63                return PTR_ERR(ts_conf);
  64
  65        conf->config = ts_conf;
  66        return 0;
  67}
  68
  69static void string_mt_destroy(const struct xt_mtdtor_param *par)
  70{
  71        textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
  72}
  73
  74static struct xt_match xt_string_mt_reg __read_mostly = {
  75        .name       = "string",
  76        .revision   = 1,
  77        .family     = NFPROTO_UNSPEC,
  78        .checkentry = string_mt_check,
  79        .match      = string_mt,
  80        .destroy    = string_mt_destroy,
  81        .matchsize  = sizeof(struct xt_string_info),
  82        .me         = THIS_MODULE,
  83};
  84
  85static int __init string_mt_init(void)
  86{
  87        return xt_register_match(&xt_string_mt_reg);
  88}
  89
  90static void __exit string_mt_exit(void)
  91{
  92        xt_unregister_match(&xt_string_mt_reg);
  93}
  94
  95module_init(string_mt_init);
  96module_exit(string_mt_exit);
  97
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