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 19MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>"); 20MODULE_DESCRIPTION("Xtables: string-based matching"); 21MODULE_LICENSE("GPL"); 22MODULE_ALIAS("ipt_string"); 23MODULE_ALIAS("ip6t_string"); 24 25static bool 26string_mt(const struct sk_buff *skb, struct xt_action_param *par) 27{ 28 const struct xt_string_info *conf = par->matchinfo; 29 struct ts_state state; 30 bool invert; 31 32 memset(&state, 0, sizeof(struct ts_state)); 33 invert = conf->u.v1.flags & XT_STRING_FLAG_INVERT; 34 35 return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 36 conf->to_offset, conf->config, &state) 37 != UINT_MAX) ^ invert; 38} 39 40#define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m)) 41 42static int string_mt_check(const struct xt_mtchk_param *par) 43{ 44 struct xt_string_info *conf = par->matchinfo; 45 struct ts_config *ts_conf; 46 int flags = TS_AUTOLOAD; 47 48 /* Damn, can't handle this case properly with iptables... */ 49 if (conf->from_offset > conf->to_offset) 50 return -EINVAL; 51 if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0') 52 return -EINVAL; 53 if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE) 54 return -EINVAL; 55 if (conf->u.v1.flags & 56 ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT)) 57 return -EINVAL; 58 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE) 59 flags |= TS_IGNORECASE; 60 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen, 61 GFP_KERNEL, flags); 62 if (IS_ERR(ts_conf)) 63 return PTR_ERR(ts_conf); 64 65 conf->config = ts_conf; 66 return 0; 67} 68 69static void string_mt_destroy(const struct xt_mtdtor_param *par) 70{ 71 textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config); 72} 73 74static struct xt_match xt_string_mt_reg __read_mostly = { 75 .name = "string", 76 .revision = 1, 77 .family = NFPROTO_UNSPEC, 78 .checkentry = string_mt_check, 79 .match = string_mt, 80 .destroy = string_mt_destroy, 81 .matchsize = sizeof(struct xt_string_info), 82 .me = THIS_MODULE, 83}; 84 85static int __init string_mt_init(void) 86{ 87 return xt_register_match(&xt_string_mt_reg); 88} 89 90static void __exit string_mt_exit(void) 91{ 92 xt_unregister_match(&xt_string_mt_reg); 93} 94 95module_init(string_mt_init); 96module_exit(string_mt_exit); 97