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 bool r; 29 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", 30 invert ? '!' : ' ', min, spi, max); 31 r = (spi >= min && spi <= max) ^ invert; 32 pr_debug(" result %s\n", r ? "PASS" : "FAILED"); 33 return r; 34 } 35 36 static bool esp_mt(const struct sk_buff *skb, struct xt_action_param *par) 37 { 38 const struct ip_esp_hdr *eh; 39 struct ip_esp_hdr _esp; 40 const struct xt_esp *espinfo = par->matchinfo; 41 42 /* Must not be a fragment. */ 43 if (par->fragoff != 0) 44 return false; 45 46 eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp); 47 if (eh == NULL) { 48 /* We've been asked to examine this packet, and we 49 * can't. Hence, no choice but to drop. 50 */ 51 pr_debug("Dropping evil ESP tinygram.\n"); 52 par->hotdrop = true; 53 return false; 54 } 55 56 return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi), 57 !!(espinfo->invflags & XT_ESP_INV_SPI)); 58 } 59 60 static int esp_mt_check(const struct xt_mtchk_param *par) 61 { 62 const struct xt_esp *espinfo = par->matchinfo; 63 64 if (espinfo->invflags & ~XT_ESP_INV_MASK) { 65 pr_debug("unknown flags %X\n", espinfo->invflags); 66 return -EINVAL; 67 } 68 69 return 0; 70 } 71 72 static struct xt_match esp_mt_reg[] __read_mostly = { 73 { 74 .name = "esp", 75 .family = NFPROTO_IPV4, 76 .checkentry = esp_mt_check, 77 .match = esp_mt, 78 .matchsize = sizeof(struct xt_esp), 79 .proto = IPPROTO_ESP, 80 .me = THIS_MODULE, 81 }, 82 { 83 .name = "esp", 84 .family = NFPROTO_IPV6, 85 .checkentry = esp_mt_check, 86 .match = esp_mt, 87 .matchsize = sizeof(struct xt_esp), 88 .proto = IPPROTO_ESP, 89 .me = THIS_MODULE, 90 }, 91 }; 92 93 static int __init esp_mt_init(void) 94 { 95 return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 96 } 97 98 static void __exit esp_mt_exit(void) 99 { 100 xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg)); 101 } 102 103 module_init(esp_mt_init); 104 module_exit(esp_mt_exit); 105