net/netfilter/xt_ipcomp.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*  Kernel module to match IPComp parameters for IPv4 and IPv6
   3  *
   4  *  Copyright (C) 2013 WindRiver
   5  *
   6  *  Author:
   7  *  Fan Du <fan.du@windriver.com>
   8  *
   9  *  Based on:
  10  *  net/netfilter/xt_esp.c
  11  */
  12
  13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14 #include <linux/in.h>
  15 #include <linux/module.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/ip.h>
  18
  19 #include <linux/netfilter/xt_ipcomp.h>
  20 #include <linux/netfilter/x_tables.h>
  21
  22 MODULE_LICENSE("GPL");
  23 MODULE_AUTHOR("Fan Du <fan.du@windriver.com>");
  24 MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match");
  25 MODULE_ALIAS("ipt_ipcomp");
  26 MODULE_ALIAS("ip6t_ipcomp");
  27
  28 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  29 static inline bool
  30 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  31 {
  32         bool r;
  33         pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
  34                  invert ? '!' : ' ', min, spi, max);
  35         r = (spi >= min && spi <= max) ^ invert;
  36         pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  37         return r;
  38 }
  39
  40 static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
  41 {
  42         struct ip_comp_hdr _comphdr;
  43         const struct ip_comp_hdr *chdr;
  44         const struct xt_ipcomp *compinfo = par->matchinfo;
  45
  46         /* Must not be a fragment. */
  47         if (par->fragoff != 0)
  48                 return false;
  49
  50         chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
  51         if (chdr == NULL) {
  52                 /* We've been asked to examine this packet, and we
  53                  * can't.  Hence, no choice but to drop.
  54                  */
  55                 pr_debug("Dropping evil IPComp tinygram.\n");
  56                 par->hotdrop = true;
  57                 return false;
  58         }
  59
  60         return spi_match(compinfo->spis[0], compinfo->spis[1],
  61                          ntohs(chdr->cpi),
  62                          !!(compinfo->invflags & XT_IPCOMP_INV_SPI));
  63 }
  64
  65 static int comp_mt_check(const struct xt_mtchk_param *par)
  66 {
  67         const struct xt_ipcomp *compinfo = par->matchinfo;
  68
  69         /* Must specify no unknown invflags */
  70         if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) {
  71                 pr_info_ratelimited("unknown flags %X\n", compinfo->invflags);
  72                 return -EINVAL;
  73         }
  74         return 0;
  75 }
  76
  77 static struct xt_match comp_mt_reg[] __read_mostly = {
  78         {
  79                 .name           = "ipcomp",
  80                 .family         = NFPROTO_IPV4,
  81                 .match          = comp_mt,
  82                 .matchsize      = sizeof(struct xt_ipcomp),
  83                 .proto          = IPPROTO_COMP,
  84                 .checkentry     = comp_mt_check,
  85                 .me             = THIS_MODULE,
  86         },
  87         {
  88                 .name           = "ipcomp",
  89                 .family         = NFPROTO_IPV6,
  90                 .match          = comp_mt,
  91                 .matchsize      = sizeof(struct xt_ipcomp),
  92                 .proto          = IPPROTO_COMP,
  93                 .checkentry     = comp_mt_check,
  94                 .me             = THIS_MODULE,
  95         },
  96 };
  97
  98 static int __init comp_mt_init(void)
  99 {
 100         return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
 101 }
 102
 103 static void __exit comp_mt_exit(void)
 104 {
 105         xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
 106 }
 107
 108 module_init(comp_mt_init);
 109 module_exit(comp_mt_exit);