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 int invert; 33 34 memset(&state, 0, sizeof(struct ts_state)); 35 36 invert = (match->revision == 0 ? conf->u.v0.invert : 37 conf->u.v1.flags & XT_STRING_FLAG_INVERT); 38 39 return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 40 conf->to_offset, conf->config, &state) 41 != UINT_MAX) ^ invert; 42 } 43 44 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m)) 45 46 static bool 47 string_mt_check(const char *tablename, const void *ip, 48 const struct xt_match *match, void *matchinfo, 49 unsigned int hook_mask) 50 { 51 struct xt_string_info *conf = matchinfo; 52 struct ts_config *ts_conf; 53 int flags = TS_AUTOLOAD; 54 55 /* Damn, can't handle this case properly with iptables... */ 56 if (conf->from_offset > conf->to_offset) 57 return false; 58 if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0') 59 return false; 60 if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE) 61 return false; 62 if (match->revision == 1) { 63 if (conf->u.v1.flags & 64 ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT)) 65 return false; 66 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE) 67 flags |= TS_IGNORECASE; 68 } 69 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen, 70 GFP_KERNEL, flags); 71 if (IS_ERR(ts_conf)) 72 return false; 73 74 conf->config = ts_conf; 75 76 return true; 77 } 78 79 static void string_mt_destroy(const struct xt_match *match, void *matchinfo) 80 { 81 textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config); 82 } 83 84 static struct xt_match string_mt_reg[] __read_mostly = { 85 { 86 .name = "string", 87 .revision = 0, 88 .family = AF_INET, 89 .checkentry = string_mt_check, 90 .match = string_mt, 91 .destroy = string_mt_destroy, 92 .matchsize = sizeof(struct xt_string_info), 93 .me = THIS_MODULE 94 }, 95 { 96 .name = "string", 97 .revision = 1, 98 .family = AF_INET, 99 .checkentry = string_mt_check, 100 .match = string_mt, 101 .destroy = string_mt_destroy, 102 .matchsize = sizeof(struct xt_string_info), 103 .me = THIS_MODULE 104 }, 105 { 106 .name = "string", 107 .revision = 0, 108 .family = AF_INET6, 109 .checkentry = string_mt_check, 110 .match = string_mt, 111 .destroy = string_mt_destroy, 112 .matchsize = sizeof(struct xt_string_info), 113 .me = THIS_MODULE 114 }, 115 { 116 .name = "string", 117 .revision = 1, 118 .family = AF_INET6, 119 .checkentry = string_mt_check, 120 .match = string_mt, 121 .destroy = string_mt_destroy, 122 .matchsize = sizeof(struct xt_string_info), 123 .me = THIS_MODULE 124 }, 125 }; 126 127 static int __init string_mt_init(void) 128 { 129 return xt_register_matches(string_mt_reg, ARRAY_SIZE(string_mt_reg)); 130 } 131 132 static void __exit string_mt_exit(void) 133 { 134 xt_unregister_matches(string_mt_reg, ARRAY_SIZE(string_mt_reg)); 135 } 136 137 module_init(string_mt_init); 138 module_exit(string_mt_exit); 139