net/netfilter/xt_string.c

   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/init.h>
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/netfilter/x_tables.h>
  15 #include <linux/netfilter/xt_string.h>
  16 #include <linux/textsearch.h>
  17
  18 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
  19 MODULE_DESCRIPTION("Xtables: string-based matching");
  20 MODULE_LICENSE("GPL");
  21 MODULE_ALIAS("ipt_string");
  22 MODULE_ALIAS("ip6t_string");
  23
  24 static bool
  25 string_mt(const struct sk_buff *skb, const struct net_device *in,
  26           const struct net_device *out, const struct xt_match *match,
  27           const void *matchinfo, int offset, unsigned int protoff,
  28           bool *hotdrop)
  29 {
  30         const struct xt_string_info *conf = matchinfo;
  31         struct ts_state state;
  32         int invert;
  33
  34         memset(&state, 0, sizeof(struct ts_state));
  35
  36         invert = (match->revision == 0 ? conf->u.v0.invert :
  37                                     conf->u.v1.flags & XT_STRING_FLAG_INVERT);
  38
  39         return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
  40                              conf->to_offset, conf->config, &state)
  41                              != UINT_MAX) ^ invert;
  42 }
  43
  44 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m))
  45
  46 static bool
  47 string_mt_check(const char *tablename, const void *ip,
  48                 const struct xt_match *match, void *matchinfo,
  49                 unsigned int hook_mask)
  50 {
  51         struct xt_string_info *conf = matchinfo;
  52         struct ts_config *ts_conf;
  53         int flags = TS_AUTOLOAD;
  54
  55         /* Damn, can't handle this case properly with iptables... */
  56         if (conf->from_offset > conf->to_offset)
  57                 return false;
  58         if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0')
  59                 return false;
  60         if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE)
  61                 return false;
  62         if (match->revision == 1) {
  63                 if (conf->u.v1.flags &
  64                     ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT))
  65                         return false;
  66                 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE)
  67                         flags |= TS_IGNORECASE;
  68         }
  69         ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
  70                                      GFP_KERNEL, flags);
  71         if (IS_ERR(ts_conf))
  72                 return false;
  73
  74         conf->config = ts_conf;
  75
  76         return true;
  77 }
  78
  79 static void string_mt_destroy(const struct xt_match *match, void *matchinfo)
  80 {
  81         textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config);
  82 }
  83
  84 static struct xt_match string_mt_reg[] __read_mostly = {
  85         {
  86                 .name           = "string",
  87                 .revision       = 0,
  88                 .family         = AF_INET,
  89                 .checkentry     = string_mt_check,
  90                 .match          = string_mt,
  91                 .destroy        = string_mt_destroy,
  92                 .matchsize      = sizeof(struct xt_string_info),
  93                 .me             = THIS_MODULE
  94         },
  95         {
  96                 .name           = "string",
  97                 .revision       = 1,
  98                 .family         = AF_INET,
  99                 .checkentry     = string_mt_check,
 100                 .match          = string_mt,
 101                 .destroy        = string_mt_destroy,
 102                 .matchsize      = sizeof(struct xt_string_info),
 103                 .me             = THIS_MODULE
 104         },
 105         {
 106                 .name           = "string",
 107                 .revision       = 0,
 108                 .family         = AF_INET6,
 109                 .checkentry     = string_mt_check,
 110                 .match          = string_mt,
 111                 .destroy        = string_mt_destroy,
 112                 .matchsize      = sizeof(struct xt_string_info),
 113                 .me             = THIS_MODULE
 114         },
 115         {
 116                 .name           = "string",
 117                 .revision       = 1,
 118                 .family         = AF_INET6,
 119                 .checkentry     = string_mt_check,
 120                 .match          = string_mt,
 121                 .destroy        = string_mt_destroy,
 122                 .matchsize      = sizeof(struct xt_string_info),
 123                 .me             = THIS_MODULE
 124         },
 125 };
 126
 127 static int __init string_mt_init(void)
 128 {
 129         return xt_register_matches(string_mt_reg, ARRAY_SIZE(string_mt_reg));
 130 }
 131
 132 static void __exit string_mt_exit(void)
 133 {
 134         xt_unregister_matches(string_mt_reg, ARRAY_SIZE(string_mt_reg));
 135 }
 136
 137 module_init(string_mt_init);
 138 module_exit(string_mt_exit);