/* Kernel module to match ESP parameters. */ /* (C) 1999-2000 Yon Uriarte <yon@astaro.de> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h> #include <linux/skbuff.h> #include <linux/in.h> #include <linux/ip.h> #include <linux/netfilter/xt_esp.h> #include <linux/netfilter/x_tables.h> #include <linux/netfilter_ipv4/ip_tables.h> #include <linux/netfilter_ipv6/ip6_tables.h> MODULE_LICENSE("GPL"); MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>"); MODULE_DESCRIPTION("Xtables: IPsec-ESP packet match"); MODULE_ALIAS("ipt_esp"); MODULE_ALIAS("ip6t_esp"); /* Returns 1 if the spi is matched by the range, 0 otherwise */ static inline bool spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) { bool r; pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", invert ? '!' : ' ', min, spi, max); r = (spi >= min && spi <= max) ^ invert; pr_debug(" result %s\n", r ? "PASS" : "FAILED"); return r; } static bool esp_mt(const struct sk_buff *skb, struct xt_action_param *par) { const struct ip_esp_hdr *eh; struct ip_esp_hdr _esp; const struct xt_esp *espinfo = par->matchinfo; /* Must not be a fragment. */ if (par->fragoff != 0) return false; eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp); if (eh == NULL) { /* We've been asked to examine this packet, and we * can't. Hence, no choice but to drop. */ pr_debug("Dropping evil ESP tinygram.\n"); par->hotdrop = true; return false; } return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi), !!(espinfo->invflags & XT_ESP_INV_SPI)); } static int esp_mt_check(const struct xt_mtchk_param *par) { const struct xt_esp *espinfo = par->matchinfo; if (espinfo->invflags & ~XT_ESP_INV_MASK) { pr_debug("unknown flags %X\n", espinfo->invflags); return -EINVAL; } return 0; } static struct xt_match esp_mt_reg[] __read_mostly = { { .name = "esp", .family = NFPROTO_IPV4, .checkentry = esp_mt_check, .match = esp_mt, .matchsize = sizeof(struct xt_esp), .proto = IPPROTO_ESP, .me = THIS_MODULE, }, { .name = "esp", .family = NFPROTO_IPV6, .checkentry = esp_mt_check, .match = esp_mt, .matchsize = sizeof(struct xt_esp), .proto = IPPROTO_ESP, .me = THIS_MODULE, }, }; static int __init esp_mt_init(void) { return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); } static void __exit esp_mt_exit(void) { xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); } module_init(esp_mt_init); module_exit(esp_mt_exit);