1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Kernel module to match ESP parameters. */ 3 4 /* (C) 1999-2000 Yon Uriarte <yon@astaro.de> 5 */ 6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 7 #include <linux/module.h> 8 #include <linux/skbuff.h> 9 #include <linux/in.h> 10 #include <linux/ip.h> 11 12 #include <linux/netfilter/xt_esp.h> 13 #include <linux/netfilter/x_tables.h> 14 15 #include <linux/netfilter_ipv4/ip_tables.h> 16 #include <linux/netfilter_ipv6/ip6_tables.h> 17 18 MODULE_LICENSE("GPL"); 19 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>"); 20 MODULE_DESCRIPTION("Xtables: IPsec-ESP packet match"); 21 MODULE_ALIAS("ipt_esp"); 22 MODULE_ALIAS("ip6t_esp"); 23 24 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 25 static inline bool 26 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 27 { 28 return (spi >= min && spi <= max) ^ invert; 29 } 30 31 static bool esp_mt(const struct sk_buff *skb, struct xt_action_param *par) 32 { 33 const struct ip_esp_hdr *eh; 34 struct ip_esp_hdr _esp; 35 const struct xt_esp *espinfo = par->matchinfo; 36 37 /* Must not be a fragment. */ 38 if (par->fragoff != 0) 39 return false; 40 41 eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp); 42 if (eh == NULL) { 43 /* We've been asked to examine this packet, and we 44 * can't. Hence, no choice but to drop. 45 */ 46 par->hotdrop = true; 47 return false; 48 } 49 50 return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi), 51 !!(espinfo->invflags & XT_ESP_INV_SPI)); 52 } 53 54 static int esp_mt_check(const struct xt_mtchk_param *par) 55 { 56 const struct xt_esp *espinfo = par->matchinfo; 57 58 if (espinfo->invflags & ~XT_ESP_INV_MASK) { 59 pr_info_ratelimited("unknown flags %X\n", espinfo->invflags); 60 return -EINVAL; 61 } 62 63 return 0; 64 } 65 66 static struct xt_match esp_mt_reg[] __read_mostly = { 67 { 68 .name = "esp", 69 .family = NFPROTO_IPV4, 70 .checkentry = esp_mt_check, 71 .match = esp_mt, 72 .matchsize = sizeof(struct xt_esp), 73 .proto = IPPROTO_ESP, 74 .me = THIS_MODULE, 75 }, 76 { 77 .name = "esp", 78 .family = NFPROTO_IPV6, 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 87 static int __init esp_mt_init(void) 88 { 89 return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 90 } 91 92 static void __exit esp_mt_exit(void) 93 { 94 xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 95 } 96 97 module_init(esp_mt_init); 98 module_exit(esp_mt_exit); 99