root/net/netfilter/xt_string.c

DEFINITIONS

1. string_mt
2. string_mt_check
3. string_mt_destroy
4. string_mt_init
5. string_mt_exit

/* String matching match for iptables
 *
 * (C) 2005 Pablo Neira Ayuso <pablo@eurodev.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_string.h>
#include <linux/textsearch.h>

MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
MODULE_DESCRIPTION("Xtables: string-based matching");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_string");
MODULE_ALIAS("ip6t_string");

static bool
string_mt(const struct sk_buff *skb, const struct xt_match_param *par)
{
        const struct xt_string_info *conf = par->matchinfo;
        struct ts_state state;
        int invert;

        memset(&state, 0, sizeof(struct ts_state));

        invert = (par->match->revision == 0 ? conf->u.v0.invert :
                                    conf->u.v1.flags & XT_STRING_FLAG_INVERT);

        return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
                             conf->to_offset, conf->config, &state)
                             != UINT_MAX) ^ invert;
}

#define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))

static bool string_mt_check(const struct xt_mtchk_param *par)
{
        struct xt_string_info *conf = par->matchinfo;
        struct ts_config *ts_conf;
        int flags = TS_AUTOLOAD;

        /* Damn, can't handle this case properly with iptables... */
        if (conf->from_offset > conf->to_offset)
                return false;
        if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
                return false;
        if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
                return false;
        if (par->match->revision == 1) {
                if (conf->u.v1.flags &
                    ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
                        return false;
                if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
                        flags |= TS_IGNORECASE;
        }
        ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
                                     GFP_KERNEL, flags);
        if (IS_ERR(ts_conf))
                return false;

        conf->config = ts_conf;

        return true;
}

static void string_mt_destroy(const struct xt_mtdtor_param *par)
{
        textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
}

static struct xt_match xt_string_mt_reg[] __read_mostly = {
        {
                .name           = "string",
                .revision       = 0,
                .family         = NFPROTO_UNSPEC,
                .checkentry     = string_mt_check,
                .match          = string_mt,
                .destroy        = string_mt_destroy,
                .matchsize      = sizeof(struct xt_string_info),
                .me             = THIS_MODULE
        },
        {
                .name           = "string",
                .revision       = 1,
                .family         = NFPROTO_UNSPEC,
                .checkentry     = string_mt_check,
                .match          = string_mt,
                .destroy        = string_mt_destroy,
                .matchsize      = sizeof(struct xt_string_info),
                .me             = THIS_MODULE
        },
};

static int __init string_mt_init(void)
{
        return xt_register_matches(xt_string_mt_reg,
                                   ARRAY_SIZE(xt_string_mt_reg));
}

static void __exit string_mt_exit(void)
{
        xt_unregister_matches(xt_string_mt_reg, ARRAY_SIZE(xt_string_mt_reg));
}

module_init(string_mt_init);
module_exit(string_mt_exit);