LXR linux/net/ipv6/netfilter/ip6t

   1/* Kernel module to match AH parameters. */
   2
   3/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
   4 *
   5 * This program is free software; you can redistribute it and/or modify
   6 * it under the terms of the GNU General Public License version 2 as
   7 * published by the Free Software Foundation.
   8 */
   9
  10#include <linux/module.h>
  11#include <linux/skbuff.h>
  12#include <linux/ip.h>
  13#include <linux/ipv6.h>
  14#include <linux/types.h>
  15#include <net/checksum.h>
  16#include <net/ipv6.h>
  17
  18#include <linux/netfilter/x_tables.h>
  19#include <linux/netfilter_ipv6/ip6_tables.h>
  20#include <linux/netfilter_ipv6/ip6t_ah.h>
  21
  22MODULE_LICENSE("GPL");
  23MODULE_DESCRIPTION("Xtables: IPv6 IPsec-AH match");
  24MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  25
  26/* Returns 1 if the spi is matched by the range, 0 otherwise */
  27static inline bool
  28spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  29{
  30        bool r;
  31
  32        pr_debug("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",
  33                 invert ? '!' : ' ', min, spi, max);
  34        r = (spi >= min && spi <= max) ^ invert;
  35        pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  36        return r;
  37}
  38
  39static bool ah_mt6(const struct sk_buff *skb, const struct xt_match_param *par)
  40{
  41        struct ip_auth_hdr _ah;
  42        const struct ip_auth_hdr *ah;
  43        const struct ip6t_ah *ahinfo = par->matchinfo;
  44        unsigned int ptr;
  45        unsigned int hdrlen = 0;
  46        int err;
  47
  48        err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL);
  49        if (err < 0) {
  50                if (err != -ENOENT)
  51                        *par->hotdrop = true;
  52                return false;
  53        }
  54
  55        ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
  56        if (ah == NULL) {
  57                *par->hotdrop = true;
  58                return false;
  59        }
  60
  61        hdrlen = (ah->hdrlen + 2) << 2;
  62
  63        pr_debug("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
  64        pr_debug("RES %04X ", ah->reserved);
  65        pr_debug("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
  66
  67        pr_debug("IPv6 AH spi %02X ",
  68                 spi_match(ahinfo->spis[0], ahinfo->spis[1],
  69                           ntohl(ah->spi),
  70                           !!(ahinfo->invflags & IP6T_AH_INV_SPI)));
  71        pr_debug("len %02X %04X %02X ",
  72                 ahinfo->hdrlen, hdrlen,
  73                 (!ahinfo->hdrlen ||
  74                  (ahinfo->hdrlen == hdrlen) ^
  75                  !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
  76        pr_debug("res %02X %04X %02X\n",
  77                 ahinfo->hdrres, ah->reserved,
  78                 !(ahinfo->hdrres && ah->reserved));
  79
  80        return (ah != NULL)
  81               &&
  82               spi_match(ahinfo->spis[0], ahinfo->spis[1],
  83                         ntohl(ah->spi),
  84                         !!(ahinfo->invflags & IP6T_AH_INV_SPI))
  85               &&
  86               (!ahinfo->hdrlen ||
  87                (ahinfo->hdrlen == hdrlen) ^
  88                !!(ahinfo->invflags & IP6T_AH_INV_LEN))
  89               &&
  90               !(ahinfo->hdrres && ah->reserved);
  91}
  92
  93static bool ah_mt6_check(const struct xt_mtchk_param *par)
  94{
  95        const struct ip6t_ah *ahinfo = par->matchinfo;
  96
  97        if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
  98                pr_debug("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
  99                return false;
 100        }
 101        return true;
 102}
 103
 104static struct xt_match ah_mt6_reg __read_mostly = {
 105        .name           = "ah",
 106        .family         = NFPROTO_IPV6,
 107        .match          = ah_mt6,
 108        .matchsize      = sizeof(struct ip6t_ah),
 109        .checkentry     = ah_mt6_check,
 110        .me             = THIS_MODULE,
 111};
 112
 113static int __init ah_mt6_init(void)
 114{
 115        return xt_register_match(&ah_mt6_reg);
 116}
 117
 118static void __exit ah_mt6_exit(void)
 119{
 120        xt_unregister_match(&ah_mt6_reg);
 121}
 122
 123module_init(ah_mt6_init);
 124module_exit(ah_mt6_exit);
 125