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 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("x_tables ESP SPI match module"); 24 MODULE_ALIAS("ipt_esp"); 25 MODULE_ALIAS("ip6t_esp"); 26 27 #if 0 28 #define duprintf(format, args...) printk(format , ## args) 29 #else 30 #define duprintf(format, args...) 31 #endif 32 33 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 34 static inline bool 35 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 36 { 37 bool r; 38 duprintf("esp spi_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ', 39 min, spi, max); 40 r = (spi >= min && spi <= max) ^ invert; 41 duprintf(" result %s\n", r ? "PASS" : "FAILED"); 42 return r; 43 } 44 45 static bool 46 esp_mt(const struct sk_buff *skb, const struct net_device *in, 47 const struct net_device *out, const struct xt_match *match, 48 const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop) 49 { 50 struct ip_esp_hdr _esp, *eh; 51 const struct xt_esp *espinfo = matchinfo; 52 53 /* Must not be a fragment. */ 54 if (offset) 55 return false; 56 57 eh = skb_header_pointer(skb, protoff, sizeof(_esp), &_esp); 58 if (eh == NULL) { 59 /* We've been asked to examine this packet, and we 60 * can't. Hence, no choice but to drop. 61 */ 62 duprintf("Dropping evil ESP tinygram.\n"); 63 *hotdrop = true; 64 return false; 65 } 66 67 return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi), 68 !!(espinfo->invflags & XT_ESP_INV_SPI)); 69 } 70 71 /* Called when user tries to insert an entry of this type. */ 72 static bool 73 esp_mt_check(const char *tablename, const void *ip_void, 74 const struct xt_match *match, void *matchinfo, 75 unsigned int hook_mask) 76 { 77 const struct xt_esp *espinfo = matchinfo; 78 79 if (espinfo->invflags & ~XT_ESP_INV_MASK) { 80 duprintf("xt_esp: unknown flags %X\n", espinfo->invflags); 81 return false; 82 } 83 84 return true; 85 } 86 87 static struct xt_match esp_mt_reg[] __read_mostly = { 88 { 89 .name = "esp", 90 .family = AF_INET, 91 .checkentry = esp_mt_check, 92 .match = esp_mt, 93 .matchsize = sizeof(struct xt_esp), 94 .proto = IPPROTO_ESP, 95 .me = THIS_MODULE, 96 }, 97 { 98 .name = "esp", 99 .family = AF_INET6, 100 .checkentry = esp_mt_check, 101 .match = esp_mt, 102 .matchsize = sizeof(struct xt_esp), 103 .proto = IPPROTO_ESP, 104 .me = THIS_MODULE, 105 }, 106 }; 107 108 static int __init esp_mt_init(void) 109 { 110 return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 111 } 112 113 static void __exit esp_mt_exit(void) 114 { 115 xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 116 } 117 118 module_init(esp_mt_init); 119 module_exit(esp_mt_exit); 120