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
  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("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
  39 static 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
  93 /* Called when user tries to insert an entry of this type. */
  94 static bool
  95 ah_mt6_check(const char *tablename, const void *entry,
  96              const struct xt_match *match, void *matchinfo,
  97              unsigned int hook_mask)
  98 {
  99         const struct ip6t_ah *ahinfo = matchinfo;
 100
 101         if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 102                 pr_debug("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
 103                 return false;
 104         }
 105         return true;
 106 }
 107
 108 static struct xt_match ah_mt6_reg __read_mostly = {
 109         .name           = "ah",
 110         .family         = NFPROTO_IPV6,
 111         .match          = ah_mt6,
 112         .matchsize      = sizeof(struct ip6t_ah),
 113         .checkentry     = ah_mt6_check,
 114         .me             = THIS_MODULE,
 115 };
 116
 117 static int __init ah_mt6_init(void)
 118 {
 119         return xt_register_match(&ah_mt6_reg);
 120 }
 121
 122 static void __exit ah_mt6_exit(void)
 123 {
 124         xt_unregister_match(&ah_mt6_reg);
 125 }
 126
 127 module_init(ah_mt6_init);
 128 module_exit(ah_mt6_exit);