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("IPv6 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
  40 match(const struct sk_buff *skb,
  41       const struct net_device *in,
  42       const struct net_device *out,
  43       const struct xt_match *match,
  44       const void *matchinfo,
  45       int offset,
  46       unsigned int protoff,
  47       bool *hotdrop)
  48 {
  49         struct ip_auth_hdr _ah;
  50         const struct ip_auth_hdr *ah;
  51         const struct ip6t_ah *ahinfo = matchinfo;
  52         unsigned int ptr;
  53         unsigned int hdrlen = 0;
  54         int err;
  55
  56         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL);
  57         if (err < 0) {
  58                 if (err != -ENOENT)
  59                         *hotdrop = true;
  60                 return false;
  61         }
  62
  63         ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
  64         if (ah == NULL) {
  65                 *hotdrop = true;
  66                 return false;
  67         }
  68
  69         hdrlen = (ah->hdrlen + 2) << 2;
  70
  71         pr_debug("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
  72         pr_debug("RES %04X ", ah->reserved);
  73         pr_debug("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
  74
  75         pr_debug("IPv6 AH spi %02X ",
  76                  spi_match(ahinfo->spis[0], ahinfo->spis[1],
  77                            ntohl(ah->spi),
  78                            !!(ahinfo->invflags & IP6T_AH_INV_SPI)));
  79         pr_debug("len %02X %04X %02X ",
  80                  ahinfo->hdrlen, hdrlen,
  81                  (!ahinfo->hdrlen ||
  82                   (ahinfo->hdrlen == hdrlen) ^
  83                   !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
  84         pr_debug("res %02X %04X %02X\n",
  85                  ahinfo->hdrres, ah->reserved,
  86                  !(ahinfo->hdrres && ah->reserved));
  87
  88         return (ah != NULL)
  89                &&
  90                spi_match(ahinfo->spis[0], ahinfo->spis[1],
  91                          ntohl(ah->spi),
  92                          !!(ahinfo->invflags & IP6T_AH_INV_SPI))
  93                &&
  94                (!ahinfo->hdrlen ||
  95                 (ahinfo->hdrlen == hdrlen) ^
  96                 !!(ahinfo->invflags & IP6T_AH_INV_LEN))
  97                &&
  98                !(ahinfo->hdrres && ah->reserved);
  99 }
 100
 101 /* Called when user tries to insert an entry of this type. */
 102 static bool
 103 checkentry(const char *tablename,
 104           const void *entry,
 105           const struct xt_match *match,
 106           void *matchinfo,
 107           unsigned int hook_mask)
 108 {
 109         const struct ip6t_ah *ahinfo = matchinfo;
 110
 111         if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 112                 pr_debug("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
 113                 return false;
 114         }
 115         return true;
 116 }
 117
 118 static struct xt_match ah_match __read_mostly = {
 119         .name           = "ah",
 120         .family         = AF_INET6,
 121         .match          = match,
 122         .matchsize      = sizeof(struct ip6t_ah),
 123         .checkentry     = checkentry,
 124         .me             = THIS_MODULE,
 125 };
 126
 127 static int __init ip6t_ah_init(void)
 128 {
 129         return xt_register_match(&ah_match);
 130 }
 131
 132 static void __exit ip6t_ah_fini(void)
 133 {
 134         xt_unregister_match(&ah_match);
 135 }
 136
 137 module_init(ip6t_ah_init);
 138 module_exit(ip6t_ah_fini);