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/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 19 MODULE_AUTHOR("Pablo Neira Ayuso <[email protected]>"); 20 MODULE_DESCRIPTION("Xtables: string-based matching"); 21 MODULE_LICENSE("GPL"); 22 MODULE_ALIAS("ipt_string"); 23 MODULE_ALIAS("ip6t_string"); 24 25 static bool 26 string_mt(const struct sk_buff *skb, const struct xt_match_param *par) 27 { 28 const struct xt_string_info *conf = par->matchinfo; 29 struct ts_state state; 30 int invert; 31 32 memset(&state, 0, sizeof(struct ts_state)); 33 34 invert = (par->match->revision == 0 ? conf->u.v0.invert : 35 conf->u.v1.flags & XT_STRING_FLAG_INVERT); 36 37 return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 38 conf->to_offset, conf->config, &state) 39 != UINT_MAX) ^ invert; 40 } 41 42 #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m)) 43 44 static bool string_mt_check(const struct xt_mtchk_param *par) 45 { 46 struct xt_string_info *conf = par->matchinfo; 47 struct ts_config *ts_conf; 48 int flags = TS_AUTOLOAD; 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 if (par->match->revision == 1) { 58 if (conf->u.v1.flags & 59 ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT)) 60 return false; 61 if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE) 62 flags |= TS_IGNORECASE; 63 } 64 ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen, 65 GFP_KERNEL, flags); 66 if (IS_ERR(ts_conf)) 67 return false; 68 69 conf->config = ts_conf; 70 71 return true; 72 } 73 74 static void string_mt_destroy(const struct xt_mtdtor_param *par) 75 { 76 textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config); 77 } 78 79 static struct xt_match xt_string_mt_reg[] __read_mostly = { 80 { 81 .name = "string", 82 .revision = 0, 83 .family = NFPROTO_UNSPEC, 84 .checkentry = string_mt_check, 85 .match = string_mt, 86 .destroy = string_mt_destroy, 87 .matchsize = sizeof(struct xt_string_info), 88 .me = THIS_MODULE 89 }, 90 { 91 .name = "string", 92 .revision = 1, 93 .family = NFPROTO_UNSPEC, 94 .checkentry = string_mt_check, 95 .match = string_mt, 96 .destroy = string_mt_destroy, 97 .matchsize = sizeof(struct xt_string_info), 98 .me = THIS_MODULE 99 }, 100 }; 101 102 static int __init string_mt_init(void) 103 { 104 return xt_register_matches(xt_string_mt_reg, 105 ARRAY_SIZE(xt_string_mt_reg)); 106 } 107 108 static void __exit string_mt_exit(void) 109 { 110 xt_unregister_matches(xt_string_mt_reg, ARRAY_SIZE(xt_string_mt_reg)); 111 } 112 113 module_init(string_mt_init); 114 module_exit(string_mt_exit); 115