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 19 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>"); 20 MODULE_DESCRIPTION("Xtables: string-based matching"); 21 MODULE_LICENSE("GPL"); 22 MODULE_ALIAS("ipt_string"); 23 MODULE_ALIAS("ip6t_string"); 24 25 static bool 26 string_mt(const struct sk_buff *skb, struct xt_action_param *par) 27 { 28 const struct xt_string_info *conf = par->matchinfo; 29 bool invert; 30 31 invert = conf->u.v1.flags & XT_STRING_FLAG_INVERT; 32 33 return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 34 conf->to_offset, conf->config) 35 != UINT_MAX) ^ invert; 36 } 37 38 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m)) 39 40 static int string_mt_check(const struct xt_mtchk_param *par) 41 { 42 struct xt_string_info *conf = par->matchinfo; 43 struct ts_config *ts_conf; 44 int flags = TS_AUTOLOAD; 45 46 /* Damn, can't handle this case properly with iptables... */ 47 if (conf->from_offset > conf->to_offset) 48 return -EINVAL; 49 if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0') 50 return -EINVAL; 51 if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE) 52 return -EINVAL; 53 if (conf->u.v1.flags & 54 ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT)) 55 return -EINVAL; 56 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE) 57 flags |= TS_IGNORECASE; 58 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen, 59 GFP_KERNEL, flags); 60 if (IS_ERR(ts_conf)) 61 return PTR_ERR(ts_conf); 62 63 conf->config = ts_conf; 64 return 0; 65 } 66 67 static void string_mt_destroy(const struct xt_mtdtor_param *par) 68 { 69 textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config); 70 } 71 72 static struct xt_match xt_string_mt_reg __read_mostly = { 73 .name = "string", 74 .revision = 1, 75 .family = NFPROTO_UNSPEC, 76 .checkentry = string_mt_check, 77 .match = string_mt, 78 .destroy = string_mt_destroy, 79 .matchsize = sizeof(struct xt_string_info), 80 .me = THIS_MODULE, 81 }; 82 83 static int __init string_mt_init(void) 84 { 85 return xt_register_match(&xt_string_mt_reg); 86 } 87 88 static void __exit string_mt_exit(void) 89 { 90 xt_unregister_match(&xt_string_mt_reg); 91 } 92 93 module_init(string_mt_init); 94 module_exit(string_mt_exit); 95