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("IP tables string match module"); 20 MODULE_LICENSE("GPL"); 21 MODULE_ALIAS("ipt_string"); 22 MODULE_ALIAS("ip6t_string"); 23 24 static int match(const struct sk_buff *skb, 25 const struct net_device *in, 26 const struct net_device *out, 27 const void *matchinfo, 28 int offset, 29 unsigned int protoff, 30 int *hotdrop) 31 { 32 struct ts_state state; 33 struct xt_string_info *conf = (struct xt_string_info *) matchinfo; 34 35 memset(&state, 0, sizeof(struct ts_state)); 36 37 return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 38 conf->to_offset, conf->config, &state) 39 != UINT_MAX) && !conf->invert; 40 } 41 42 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *) m) 43 44 static int checkentry(const char *tablename, 45 const void *ip, 46 void *matchinfo, 47 unsigned int matchsize, 48 unsigned int hook_mask) 49 { 50 struct xt_string_info *conf = matchinfo; 51 struct ts_config *ts_conf; 52 53 if (matchsize != XT_ALIGN(sizeof(struct xt_string_info))) 54 return 0; 55 56 /* Damn, can't handle this case properly with iptables... */ 57 if (conf->from_offset > conf->to_offset) 58 return 0; 59 60 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen, 61 GFP_KERNEL, TS_AUTOLOAD); 62 if (IS_ERR(ts_conf)) 63 return 0; 64 65 conf->config = ts_conf; 66 67 return 1; 68 } 69 70 static void destroy(void *matchinfo, unsigned int matchsize) 71 { 72 textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config); 73 } 74 75 static struct xt_match string_match = { 76 .name = "string", 77 .match = match, 78 .checkentry = checkentry, 79 .destroy = destroy, 80 .me = THIS_MODULE 81 }; 82 static struct xt_match string6_match = { 83 .name = "string", 84 .match = match, 85 .checkentry = checkentry, 86 .destroy = destroy, 87 .me = THIS_MODULE 88 }; 89 90 static int __init init(void) 91 { 92 int ret; 93 94 ret = xt_register_match(AF_INET, &string_match); 95 if (ret) 96 return ret; 97 ret = xt_register_match(AF_INET6, &string6_match); 98 if (ret) 99 xt_unregister_match(AF_INET, &string_match); 100 101 return ret; 102 } 103 104 static void __exit fini(void) 105 { 106 xt_unregister_match(AF_INET, &string_match); 107 xt_unregister_match(AF_INET6, &string6_match); 108 } 109 110 module_init(init); 111 module_exit(fini); 112