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 int 35 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert) 36 { 37 int r = 0; 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 int 46 match(const struct sk_buff *skb, 47 const struct net_device *in, 48 const struct net_device *out, 49 const struct xt_match *match, 50 const void *matchinfo, 51 int offset, 52 unsigned int protoff, 53 int *hotdrop) 54 { 55 struct ip_esp_hdr _esp, *eh; 56 const struct xt_esp *espinfo = matchinfo; 57 58 /* Must not be a fragment. */ 59 if (offset) 60 return 0; 61 62 eh = skb_header_pointer(skb, protoff, sizeof(_esp), &_esp); 63 if (eh == NULL) { 64 /* We've been asked to examine this packet, and we 65 * can't. Hence, no choice but to drop. 66 */ 67 duprintf("Dropping evil ESP tinygram.\n"); 68 *hotdrop = 1; 69 return 0; 70 } 71 72 return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi), 73 !!(espinfo->invflags & XT_ESP_INV_SPI)); 74 } 75 76 /* Called when user tries to insert an entry of this type. */ 77 static int 78 checkentry(const char *tablename, 79 const void *ip_void, 80 const struct xt_match *match, 81 void *matchinfo, 82 unsigned int matchinfosize, 83 unsigned int hook_mask) 84 { 85 const struct xt_esp *espinfo = matchinfo; 86 87 if (espinfo->invflags & ~XT_ESP_INV_MASK) { 88 duprintf("xt_esp: unknown flags %X\n", espinfo->invflags); 89 return 0; 90 } 91 92 return 1; 93 } 94 95 static struct xt_match xt_esp_match[] = { 96 { 97 .name = "esp", 98 .family = AF_INET, 99 .checkentry = checkentry, 100 .match = match, 101 .matchsize = sizeof(struct xt_esp), 102 .proto = IPPROTO_ESP, 103 .me = THIS_MODULE, 104 }, 105 { 106 .name = "esp", 107 .family = AF_INET6, 108 .checkentry = checkentry, 109 .match = match, 110 .matchsize = sizeof(struct xt_esp), 111 .proto = IPPROTO_ESP, 112 .me = THIS_MODULE, 113 }, 114 }; 115 116 static int __init xt_esp_init(void) 117 { 118 return xt_register_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match)); 119 } 120 121 static void __exit xt_esp_cleanup(void) 122 { 123 xt_unregister_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match)); 124 } 125 126 module_init(xt_esp_init); 127 module_exit(xt_esp_cleanup); 128