1 /* Kernel module to match ESP parameters. */ 2 3 /* (C) 1999-2000 Yon Uriarte <yon@astaro.de> 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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 10 #include <linux/module.h> 11 #include <linux/skbuff.h> 12 #include <linux/in.h> 13 #include <linux/ip.h> 14 15 #include <linux/netfilter/xt_esp.h> 16 #include <linux/netfilter/x_tables.h> 17 18 #include <linux/netfilter_ipv4/ip_tables.h> 19 #include <linux/netfilter_ipv6/ip6_tables.h> 20 21 MODULE_LICENSE("GPL"); 22 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>"); 23 MODULE_DESCRIPTION("Xtables: IPsec-ESP packet match"); 24 MODULE_ALIAS("ipt_esp"); 25 MODULE_ALIAS("ip6t_esp"); 26 27 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 28 static inline bool 29 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 30 { 31 bool r; 32 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", 33 invert ? '!' : ' ', min, spi, max); 34 r = (spi >= min && spi <= max) ^ invert; 35 pr_debug(" result %s\n", r ? "PASS" : "FAILED"); 36 return r; 37 } 38 39 static bool esp_mt(const struct sk_buff *skb, const struct xt_match_param *par) 40 { 41 const struct ip_esp_hdr *eh; 42 struct ip_esp_hdr _esp; 43 const struct xt_esp *espinfo = par->matchinfo; 44 45 /* Must not be a fragment. */ 46 if (par->fragoff != 0) 47 return false; 48 49 eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp); 50 if (eh == NULL) { 51 /* We've been asked to examine this packet, and we 52 * can't. Hence, no choice but to drop. 53 */ 54 pr_debug("Dropping evil ESP tinygram.\n"); 55 *par->hotdrop = true; 56 return false; 57 } 58 59 return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi), 60 !!(espinfo->invflags & XT_ESP_INV_SPI)); 61 } 62 63 static int esp_mt_check(const struct xt_mtchk_param *par) 64 { 65 const struct xt_esp *espinfo = par->matchinfo; 66 67 if (espinfo->invflags & ~XT_ESP_INV_MASK) { 68 pr_debug("unknown flags %X\n", espinfo->invflags); 69 return -EINVAL; 70 } 71 72 return 0; 73 } 74 75 static struct xt_match esp_mt_reg[] __read_mostly = { 76 { 77 .name = "esp", 78 .family = NFPROTO_IPV4, 79 .checkentry = esp_mt_check, 80 .match = esp_mt, 81 .matchsize = sizeof(struct xt_esp), 82 .proto = IPPROTO_ESP, 83 .me = THIS_MODULE, 84 }, 85 { 86 .name = "esp", 87 .family = NFPROTO_IPV6, 88 .checkentry = esp_mt_check, 89 .match = esp_mt, 90 .matchsize = sizeof(struct xt_esp), 91 .proto = IPPROTO_ESP, 92 .me = THIS_MODULE, 93 }, 94 }; 95 96 static int __init esp_mt_init(void) 97 { 98 return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 99 } 100 101 static void __exit esp_mt_exit(void) 102 { 103 xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 104 } 105 106 module_init(esp_mt_init); 107 module_exit(esp_mt_exit); 108