| 1 | /* String matching match for iptables |
| 2 | * |
| 3 | * (C) 2005 Pablo Neira Ayuso <pablo@eurodev.net> |
| 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 <pablo@eurodev.net>"); |
| 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, struct xt_action_param *par) |
| 27 | { |
| 28 | const struct xt_string_info *conf = par->matchinfo; |
| 29 | bool invert; |
| 30 | |
| 31 | invert = conf->u.v1.flags & XT_STRING_FLAG_INVERT; |
| 32 | |
| 33 | return (skb_find_text((struct sk_buff *)skb, conf->from_offset, |
| 34 | conf->to_offset, conf->config) |
| 35 | != UINT_MAX) ^ invert; |
| 36 | } |
| 37 | |
| 38 | #define STRING_TEXT_PRIV(m) ((struct xt_string_info *)(m)) |
| 39 | |
| 40 | static int string_mt_check(const struct xt_mtchk_param *par) |
| 41 | { |
| 42 | struct xt_string_info *conf = par->matchinfo; |
| 43 | struct ts_config *ts_conf; |
| 44 | int flags = TS_AUTOLOAD; |
| 45 | |
| 46 | /* Damn, can't handle this case properly with iptables... */ |
| 47 | if (conf->from_offset > conf->to_offset) |
| 48 | return -EINVAL; |
| 49 | if (conf->algo[XT_STRING_MAX_ALGO_NAME_SIZE - 1] != '\0') |
| 50 | return -EINVAL; |
| 51 | if (conf->patlen > XT_STRING_MAX_PATTERN_SIZE) |
| 52 | return -EINVAL; |
| 53 | if (conf->u.v1.flags & |
| 54 | ~(XT_STRING_FLAG_IGNORECASE | XT_STRING_FLAG_INVERT)) |
| 55 | return -EINVAL; |
| 56 | if (conf->u.v1.flags & XT_STRING_FLAG_IGNORECASE) |
| 57 | flags |= TS_IGNORECASE; |
| 58 | ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen, |
| 59 | GFP_KERNEL, flags); |
| 60 | if (IS_ERR(ts_conf)) |
| 61 | return PTR_ERR(ts_conf); |
| 62 | |
| 63 | conf->config = ts_conf; |
| 64 | return 0; |
| 65 | } |
| 66 | |
| 67 | static void string_mt_destroy(const struct xt_mtdtor_param *par) |
| 68 | { |
| 69 | textsearch_destroy(STRING_TEXT_PRIV(par->matchinfo)->config); |
| 70 | } |
| 71 | |
| 72 | static struct xt_match xt_string_mt_reg __read_mostly = { |
| 73 | .name = "string", |
| 74 | .revision = 1, |
| 75 | .family = NFPROTO_UNSPEC, |
| 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 | static int __init string_mt_init(void) |
| 84 | { |
| 85 | return xt_register_match(&xt_string_mt_reg); |
| 86 | } |
| 87 | |
| 88 | static void __exit string_mt_exit(void) |
| 89 | { |
| 90 | xt_unregister_match(&xt_string_mt_reg); |
| 91 | } |
| 92 | |
| 93 | module_init(string_mt_init); |
| 94 | module_exit(string_mt_exit); |