net/ipv6/netfilter/ip6t_ah.c

   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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  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
  22 MODULE_LICENSE("GPL");
  23 MODULE_DESCRIPTION("Xtables: IPv6 IPsec-AH match");
  24 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  25
  26 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  27 static inline bool
  28 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  29 {
  30         bool r;
  31
  32         pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
  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
  39 static bool ah_mt6(const struct sk_buff *skb, struct xt_action_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 = 0;
  45         unsigned int hdrlen = 0;
  46         int err;
  47
  48         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL, 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                 spi_match(ahinfo->spis[0], ahinfo->spis[1],
  82                           ntohl(ah->spi),
  83                           !!(ahinfo->invflags & IP6T_AH_INV_SPI)) &&
  84                 (!ahinfo->hdrlen ||
  85                  (ahinfo->hdrlen == hdrlen) ^
  86                  !!(ahinfo->invflags & IP6T_AH_INV_LEN)) &&
  87                 !(ahinfo->hdrres && ah->reserved);
  88 }
  89
  90 static int ah_mt6_check(const struct xt_mtchk_param *par)
  91 {
  92         const struct ip6t_ah *ahinfo = par->matchinfo;
  93
  94         if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
  95                 pr_debug("unknown flags %X\n", ahinfo->invflags);
  96                 return -EINVAL;
  97         }
  98         return 0;
  99 }
 100
 101 static struct xt_match ah_mt6_reg __read_mostly = {
 102         .name           = "ah",
 103         .family         = NFPROTO_IPV6,
 104         .match          = ah_mt6,
 105         .matchsize      = sizeof(struct ip6t_ah),
 106         .checkentry     = ah_mt6_check,
 107         .me             = THIS_MODULE,
 108 };
 109
 110 static int __init ah_mt6_init(void)
 111 {
 112         return xt_register_match(&ah_mt6_reg);
 113 }
 114
 115 static void __exit ah_mt6_exit(void)
 116 {
 117         xt_unregister_match(&ah_mt6_reg);
 118 }
 119
 120 module_init(ah_mt6_init);
 121 module_exit(ah_mt6_exit);