net/netfilter/xt_esp.c

   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);