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 ah_mt6(const struct sk_buff *skb, const struct net_device *in,
  41        const struct net_device *out, const struct xt_match *match,
  42        const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
  43 {
  44         struct ip_auth_hdr _ah;
  45         const struct ip_auth_hdr *ah;
  46         const struct ip6t_ah *ahinfo = matchinfo;
  47         unsigned int ptr;
  48         unsigned int hdrlen = 0;
  49         int err;
  50
  51         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL);
  52         if (err < 0) {
  53                 if (err != -ENOENT)
  54                         *hotdrop = true;
  55                 return false;
  56         }
  57
  58         ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
  59         if (ah == NULL) {
  60                 *hotdrop = true;
  61                 return false;
  62         }
  63
  64         hdrlen = (ah->hdrlen + 2) << 2;
  65
  66         pr_debug("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
  67         pr_debug("RES %04X ", ah->reserved);
  68         pr_debug("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
  69
  70         pr_debug("IPv6 AH spi %02X ",
  71                  spi_match(ahinfo->spis[0], ahinfo->spis[1],
  72                            ntohl(ah->spi),
  73                            !!(ahinfo->invflags & IP6T_AH_INV_SPI)));
  74         pr_debug("len %02X %04X %02X ",
  75                  ahinfo->hdrlen, hdrlen,
  76                  (!ahinfo->hdrlen ||
  77                   (ahinfo->hdrlen == hdrlen) ^
  78                   !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
  79         pr_debug("res %02X %04X %02X\n",
  80                  ahinfo->hdrres, ah->reserved,
  81                  !(ahinfo->hdrres && ah->reserved));
  82
  83         return (ah != NULL)
  84                &&
  85                spi_match(ahinfo->spis[0], ahinfo->spis[1],
  86                          ntohl(ah->spi),
  87                          !!(ahinfo->invflags & IP6T_AH_INV_SPI))
  88                &&
  89                (!ahinfo->hdrlen ||
  90                 (ahinfo->hdrlen == hdrlen) ^
  91                 !!(ahinfo->invflags & IP6T_AH_INV_LEN))
  92                &&
  93                !(ahinfo->hdrres && ah->reserved);
  94 }
  95
  96 /* Called when user tries to insert an entry of this type. */
  97 static bool
  98 ah_mt6_check(const char *tablename, const void *entry,
  99              const struct xt_match *match, void *matchinfo,
 100              unsigned int hook_mask)
 101 {
 102         const struct ip6t_ah *ahinfo = matchinfo;
 103
 104         if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 105                 pr_debug("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
 106                 return false;
 107         }
 108         return true;
 109 }
 110
 111 static struct xt_match ah_mt6_reg __read_mostly = {
 112         .name           = "ah",
 113         .family         = AF_INET6,
 114         .match          = ah_mt6,
 115         .matchsize      = sizeof(struct ip6t_ah),
 116         .checkentry     = ah_mt6_check,
 117         .me             = THIS_MODULE,
 118 };
 119
 120 static int __init ah_mt6_init(void)
 121 {
 122         return xt_register_match(&ah_mt6_reg);
 123 }
 124
 125 static void __exit ah_mt6_exit(void)
 126 {
 127         xt_unregister_match(&ah_mt6_reg);
 128 }
 129
 130 module_init(ah_mt6_init);
 131 module_exit(ah_mt6_exit);