net/netfilter/xt_string.c

   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
  16 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
  17 MODULE_DESCRIPTION("Xtables: string-based matching");
  18 MODULE_LICENSE("GPL");
  19 MODULE_ALIAS("ipt_string");
  20 MODULE_ALIAS("ip6t_string");
  21 MODULE_ALIAS("ebt_string");
  22
  23 static bool
  24 string_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
  38 static 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
  65 static void string_mt_destroy(const struct xt_mtdtor_param *par)
  66 {
  67         textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config);
  68 }
  69
  70 static 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
  82 static int __init string_mt_init(void)
  83 {
  84         return xt_register_match(&xt_string_mt_reg);
  85 }
  86
  87 static void __exit string_mt_exit(void)
  88 {
  89         xt_unregister_match(&xt_string_mt_reg);
  90 }
  91
  92 module_init(string_mt_init);
  93 module_exit(string_mt_exit);