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 #if 0
  27 #define DEBUGP printk
  28 #else
  29 #define DEBUGP(format, args...)
  30 #endif
  31
  32 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  33 static inline bool
  34 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  35 {
  36         bool r;
  37         DEBUGP("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
  38                min,spi,max);
  39         r = (spi >= min && spi <= max) ^ invert;
  40         DEBUGP(" result %s\n",r? "PASS\n" : "FAILED\n");
  41         return r;
  42 }
  43
  44 static bool
  45 match(const struct sk_buff *skb,
  46       const struct net_device *in,
  47       const struct net_device *out,
  48       const struct xt_match *match,
  49       const void *matchinfo,
  50       int offset,
  51       unsigned int protoff,
  52       bool *hotdrop)
  53 {
  54         struct ip_auth_hdr _ah;
  55         const struct ip_auth_hdr *ah;
  56         const struct ip6t_ah *ahinfo = matchinfo;
  57         unsigned int ptr;
  58         unsigned int hdrlen = 0;
  59         int err;
  60
  61         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL);
  62         if (err < 0) {
  63                 if (err != -ENOENT)
  64                         *hotdrop = true;
  65                 return false;
  66         }
  67
  68         ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
  69         if (ah == NULL) {
  70                 *hotdrop = true;
  71                 return false;
  72         }
  73
  74         hdrlen = (ah->hdrlen + 2) << 2;
  75
  76         DEBUGP("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
  77         DEBUGP("RES %04X ", ah->reserved);
  78         DEBUGP("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
  79
  80         DEBUGP("IPv6 AH spi %02X ",
  81                spi_match(ahinfo->spis[0], ahinfo->spis[1],
  82                          ntohl(ah->spi),
  83                          !!(ahinfo->invflags & IP6T_AH_INV_SPI)));
  84         DEBUGP("len %02X %04X %02X ",
  85                ahinfo->hdrlen, hdrlen,
  86                (!ahinfo->hdrlen ||
  87                 (ahinfo->hdrlen == hdrlen) ^
  88                 !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
  89         DEBUGP("res %02X %04X %02X\n",
  90                ahinfo->hdrres, ah->reserved,
  91                !(ahinfo->hdrres && ah->reserved));
  92
  93         return (ah != NULL)
  94                &&
  95                spi_match(ahinfo->spis[0], ahinfo->spis[1],
  96                          ntohl(ah->spi),
  97                          !!(ahinfo->invflags & IP6T_AH_INV_SPI))
  98                &&
  99                (!ahinfo->hdrlen ||
 100                 (ahinfo->hdrlen == hdrlen) ^
 101                 !!(ahinfo->invflags & IP6T_AH_INV_LEN))
 102                &&
 103                !(ahinfo->hdrres && ah->reserved);
 104 }
 105
 106 /* Called when user tries to insert an entry of this type. */
 107 static bool
 108 checkentry(const char *tablename,
 109           const void *entry,
 110           const struct xt_match *match,
 111           void *matchinfo,
 112           unsigned int hook_mask)
 113 {
 114         const struct ip6t_ah *ahinfo = matchinfo;
 115
 116         if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 117                 DEBUGP("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
 118                 return false;
 119         }
 120         return true;
 121 }
 122
 123 static struct xt_match ah_match __read_mostly = {
 124         .name           = "ah",
 125         .family         = AF_INET6,
 126         .match          = match,
 127         .matchsize      = sizeof(struct ip6t_ah),
 128         .checkentry     = checkentry,
 129         .me             = THIS_MODULE,
 130 };
 131
 132 static int __init ip6t_ah_init(void)
 133 {
 134         return xt_register_match(&ah_match);
 135 }
 136
 137 static void __exit ip6t_ah_fini(void)
 138 {
 139         xt_unregister_match(&ah_match);
 140 }
 141
 142 module_init(ip6t_ah_init);
 143 module_exit(ip6t_ah_fini);