LXR linux/net/ipv4/netfilter/ipt

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* Kernel module to match AH parameters. */
   3/* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
   4 */
   5#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   6#include <linux/in.h>
   7#include <linux/module.h>
   8#include <linux/skbuff.h>
   9#include <linux/ip.h>
  10
  11#include <linux/netfilter_ipv4/ipt_ah.h>
  12#include <linux/netfilter/x_tables.h>
  13
  14MODULE_LICENSE("GPL");
  15MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
  16MODULE_DESCRIPTION("Xtables: IPv4 IPsec-AH SPI match");
  17
  18/* Returns 1 if the spi is matched by the range, 0 otherwise */
  19static inline bool
  20spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  21{
  22        bool r;
  23        pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
  24                 invert ? '!' : ' ', min, spi, max);
  25        r = (spi >= min && spi <= max) ^ invert;
  26        pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  27        return r;
  28}
  29
  30static bool ah_mt(const struct sk_buff *skb, struct xt_action_param *par)
  31{
  32        struct ip_auth_hdr _ahdr;
  33        const struct ip_auth_hdr *ah;
  34        const struct ipt_ah *ahinfo = par->matchinfo;
  35
  36        /* Must not be a fragment. */
  37        if (par->fragoff != 0)
  38                return false;
  39
  40        ah = skb_header_pointer(skb, par->thoff, sizeof(_ahdr), &_ahdr);
  41        if (ah == NULL) {
  42                /* We've been asked to examine this packet, and we
  43                 * can't.  Hence, no choice but to drop.
  44                 */
  45                pr_debug("Dropping evil AH tinygram.\n");
  46                par->hotdrop = true;
  47                return false;
  48        }
  49
  50        return spi_match(ahinfo->spis[0], ahinfo->spis[1],
  51                         ntohl(ah->spi),
  52                         !!(ahinfo->invflags & IPT_AH_INV_SPI));
  53}
  54
  55static int ah_mt_check(const struct xt_mtchk_param *par)
  56{
  57        const struct ipt_ah *ahinfo = par->matchinfo;
  58
  59        /* Must specify no unknown invflags */
  60        if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
  61                pr_debug("unknown flags %X\n", ahinfo->invflags);
  62                return -EINVAL;
  63        }
  64        return 0;
  65}
  66
  67static struct xt_match ah_mt_reg __read_mostly = {
  68        .name           = "ah",
  69        .family         = NFPROTO_IPV4,
  70        .match          = ah_mt,
  71        .matchsize      = sizeof(struct ipt_ah),
  72        .proto          = IPPROTO_AH,
  73        .checkentry     = ah_mt_check,
  74        .me             = THIS_MODULE,
  75};
  76
  77static int __init ah_mt_init(void)
  78{
  79        return xt_register_match(&ah_mt_reg);
  80}
  81
  82static void __exit ah_mt_exit(void)
  83{
  84        xt_unregister_match(&ah_mt_reg);
  85}
  86
  87module_init(ah_mt_init);
  88module_exit(ah_mt_exit);
  89