1 /* String matching match for iptables 2 * 3 * (C) 2005 Pablo Neira Ayuso <[email protected]> 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 <[email protected]>"); 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 33 memset(&state, 0, sizeof(struct ts_state)); 34 35 return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 36 conf->to_offset, conf->config, &state) 37 != UINT_MAX) ^ conf->invert; 38 } 39 40 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m)) 41 42 static bool 43 string_mt_check(const char *tablename, const void *ip, 44 const struct xt_match *match, void *matchinfo, 45 unsigned int hook_mask) 46 { 47 struct xt_string_info *conf = matchinfo; 48 struct ts_config *ts_conf; 49 50 /* Damn, can't handle this case properly with iptables... */ 51 if (conf->from_offset > conf->to_offset) 52 return false; 53 if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0') 54 return false; 55 if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE) 56 return false; 57 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen, 58 GFP_KERNEL, TS_AUTOLOAD); 59 if (IS_ERR(ts_conf)) 60 return false; 61 62 conf->config = ts_conf; 63 64 return true; 65 } 66 67 static void string_mt_destroy(const struct xt_match *match, void *matchinfo) 68 { 69 textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config); 70 } 71 72 static struct xt_match string_mt_reg[] __read_mostly = { 73 { 74 .name = "string", 75 .family = AF_INET, 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 .name = "string", 84 .family = AF_INET6, 85 .checkentry = string_mt_check, 86 .match = string_mt, 87 .destroy = string_mt_destroy, 88 .matchsize = sizeof(struct xt_string_info), 89 .me = THIS_MODULE 90 }, 91 }; 92 93 static int __init string_mt_init(void) 94 { 95 return xt_register_matches(string_mt_reg, ARRAY_SIZE(string_mt_reg)); 96 } 97 98 static void __exit string_mt_exit(void) 99 { 100 xt_unregister_matches(string_mt_reg, ARRAY_SIZE(string_mt_reg)); 101 } 102 103 module_init(string_mt_init); 104 module_exit(string_mt_exit); 105