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 struct xt_match *match, 28 const void *matchinfo, 29 int offset, 30 unsigned int protoff, 31 int *hotdrop) 32 { 33 const struct xt_string_info *conf = matchinfo; 34 struct ts_state state; 35 36 memset(&state, 0, sizeof(struct ts_state)); 37 38 return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 39 conf->to_offset, conf->config, &state) 40 != UINT_MAX) ^ conf->invert; 41 } 42 43 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *) m) 44 45 static int checkentry(const char *tablename, 46 const void *ip, 47 const struct xt_match *match, 48 void *matchinfo, 49 unsigned int hook_mask) 50 { 51 struct xt_string_info *conf = matchinfo; 52 struct ts_config *ts_conf; 53 54 /* Damn, can't handle this case properly with iptables... */ 55 if (conf->from_offset > conf->to_offset) 56 return 0; 57 if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0') 58 return 0; 59 if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE) 60 return 0; 61 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen, 62 GFP_KERNEL, TS_AUTOLOAD); 63 if (IS_ERR(ts_conf)) 64 return 0; 65 66 conf->config = ts_conf; 67 68 return 1; 69 } 70 71 static void destroy(const struct xt_match *match, void *matchinfo) 72 { 73 textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config); 74 } 75 76 static struct xt_match xt_string_match[] = { 77 { 78 .name = "string", 79 .family = AF_INET, 80 .checkentry = checkentry, 81 .match = match, 82 .destroy = destroy, 83 .matchsize = sizeof(struct xt_string_info), 84 .me = THIS_MODULE 85 }, 86 { 87 .name = "string", 88 .family = AF_INET6, 89 .checkentry = checkentry, 90 .match = match, 91 .destroy = destroy, 92 .matchsize = sizeof(struct xt_string_info), 93 .me = THIS_MODULE 94 }, 95 }; 96 97 static int __init xt_string_init(void) 98 { 99 return xt_register_matches(xt_string_match, ARRAY_SIZE(xt_string_match)); 100 } 101 102 static void __exit xt_string_fini(void) 103 { 104 xt_unregister_matches(xt_string_match, ARRAY_SIZE(xt_string_match)); 105 } 106 107 module_init(xt_string_init); 108 module_exit(xt_string_fini); 109