LXR linux/net/netfilter/xt

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* String matching match for iptables
   3 *
   4 * (C) 2005 Pablo Neira Ayuso <pablo@eurodev.net>
   5 */
   6
   7#include <linux/gfp.h>
   8#include <linux/init.h>
   9#include <linux/module.h>
  10#include <linux/kernel.h>
  11#include <linux/skbuff.h>
  12#include <linux/netfilter/x_tables.h>
  13#include <linux/netfilter/xt_string.h>
  14#include <linux/textsearch.h>
  15
  16MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
  17MODULE_DESCRIPTION("Xtables: string-based matching");
  18MODULE_LICENSE("GPL");
  19MODULE_ALIAS("ipt_string");
  20MODULE_ALIAS("ip6t_string");
  21MODULE_ALIAS("ebt_string");
  22
  23static bool
  24string_mt(const struct sk_buff *skb, struct xt_action_param *par)
  25{
  26        const struct xt_string_info *conf = par->matchinfo;
  27        bool invert;
  28
  29        invert = conf->u.v1.flags & XT_STRING_FLAG_INVERT;
  30
  31        return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
  32                             conf->to_offset, conf->config)
  33                             != UINT_MAX) ^ invert;
  34}
  35
  36#define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
  37
  38static int string_mt_check(const struct xt_mtchk_param *par)
  39{
  40        struct xt_string_info *conf = par->matchinfo;
  41        struct ts_config *ts_conf;
  42        int flags = TS_AUTOLOAD;
  43
  44        /* Damn, can't handle this case properly with iptables... */
  45        if (conf->from_offset > conf->to_offset)
  46                return -EINVAL;
  47        if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
  48                return -EINVAL;
  49        if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
  50                return -EINVAL;
  51        if (conf->u.v1.flags &
  52            ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
  53                return -EINVAL;
  54        if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
  55                flags |= TS_IGNORECASE;
  56        ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  57                                     GFP_KERNEL, flags);
  58        if (IS_ERR(ts_conf))
  59                return PTR_ERR(ts_conf);
  60
  61        conf->config = ts_conf;
  62        return 0;
  63}
  64
  65static void string_mt_destroy(const struct xt_mtdtor_param *par)
  66{
  67        textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
  68}
  69
  70static struct xt_match xt_string_mt_reg __read_mostly = {
  71        .name       = "string",
  72        .revision   = 1,
  73        .family     = NFPROTO_UNSPEC,
  74        .checkentry = string_mt_check,
  75        .match      = string_mt,
  76        .destroy    = string_mt_destroy,
  77        .matchsize  = sizeof(struct xt_string_info),
  78        .usersize   = offsetof(struct xt_string_info, config),
  79        .me         = THIS_MODULE,
  80};
  81
  82static int __init string_mt_init(void)
  83{
  84        return xt_register_match(&xt_string_mt_reg);
  85}
  86
  87static void __exit string_mt_exit(void)
  88{
  89        xt_unregister_match(&xt_string_mt_reg);
  90}
  91
  92module_init(string_mt_init);
  93module_exit(string_mt_exit);
  94