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, 40 const struct xt_action_param *par) 41 { 42 const struct ip_esp_hdr *eh; 43 struct ip_esp_hdr _esp; 44 const struct xt_esp *espinfo = par->matchinfo; 45 46 /* Must not be a fragment. */ 47 if (par->fragoff != 0) 48 return false; 49 50 eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp); 51 if (eh == NULL) { 52 /* We've been asked to examine this packet, and we 53 * can't. Hence, no choice but to drop. 54 */ 55 pr_debug("Dropping evil ESP tinygram.\n"); 56 *par->hotdrop = true; 57 return false; 58 } 59 60 return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi), 61 !!(espinfo->invflags & XT_ESP_INV_SPI)); 62 } 63 64 static int esp_mt_check(const struct xt_mtchk_param *par) 65 { 66 const struct xt_esp *espinfo = par->matchinfo; 67 68 if (espinfo->invflags & ~XT_ESP_INV_MASK) { 69 pr_debug("unknown flags %X\n", espinfo->invflags); 70 return -EINVAL; 71 } 72 73 return 0; 74 } 75 76 static struct xt_match esp_mt_reg[] __read_mostly = { 77 { 78 .name = "esp", 79 .family = NFPROTO_IPV4, 80 .checkentry = esp_mt_check, 81 .match = esp_mt, 82 .matchsize = sizeof(struct xt_esp), 83 .proto = IPPROTO_ESP, 84 .me = THIS_MODULE, 85 }, 86 { 87 .name = "esp", 88 .family = NFPROTO_IPV6, 89 .checkentry = esp_mt_check, 90 .match = esp_mt, 91 .matchsize = sizeof(struct xt_esp), 92 .proto = IPPROTO_ESP, 93 .me = THIS_MODULE, 94 }, 95 }; 96 97 static int __init esp_mt_init(void) 98 { 99 return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 100 } 101 102 static void __exit esp_mt_exit(void) 103 { 104 xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 105 } 106 107 module_init(esp_mt_init); 108 module_exit(esp_mt_exit); 109