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/ipv6.h>
  13 #include <linux/types.h>
  14 #include <net/checksum.h>
  15 #include <net/ipv6.h>
  16
  17 #include <linux/netfilter_ipv6/ip6_tables.h>
  18 #include <linux/netfilter_ipv6/ip6t_ah.h>
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_DESCRIPTION("IPv6 AH match");
  22 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  23
  24 #if 0
  25 #define DEBUGP printk
  26 #else
  27 #define DEBUGP(format, args...)
  28 #endif
  29
  30 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  31 static inline int
  32 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
  33 {
  34         int r=0;
  35         DEBUGP("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
  36                min,spi,max);
  37         r = (spi >= min && spi <= max) ^ invert;
  38         DEBUGP(" result %s\n",r? "PASS\n" : "FAILED\n");
  39         return r;
  40 }
  41
  42 static int
  43 match(const struct sk_buff *skb,
  44       const struct net_device *in,
  45       const struct net_device *out,
  46       const void *matchinfo,
  47       int offset,
  48       unsigned int protoff,
  49       int *hotdrop)
  50 {
  51         struct ip_auth_hdr *ah, _ah;
  52         const struct ip6t_ah *ahinfo = matchinfo;
  53         unsigned int ptr;
  54         unsigned int hdrlen = 0;
  55
  56         if (ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH) < 0)
  57                 return 0;
  58
  59         ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
  60         if (ah == NULL) {
  61                 *hotdrop = 1;
  62                 return 0;
  63         }
  64
  65         hdrlen = (ah->hdrlen + 2) << 2;
  66
  67         DEBUGP("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
  68         DEBUGP("RES %04X ", ah->reserved);
  69         DEBUGP("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
  70
  71         DEBUGP("IPv6 AH spi %02X ",
  72                (spi_match(ahinfo->spis[0], ahinfo->spis[1],
  73                           ntohl(ah->spi),
  74                           !!(ahinfo->invflags & IP6T_AH_INV_SPI))));
  75         DEBUGP("len %02X %04X %02X ",
  76                ahinfo->hdrlen, hdrlen,
  77                (!ahinfo->hdrlen ||
  78                 (ahinfo->hdrlen == hdrlen) ^
  79                 !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
  80         DEBUGP("res %02X %04X %02X\n",
  81                ahinfo->hdrres, ah->reserved,
  82                !(ahinfo->hdrres && ah->reserved));
  83
  84         return (ah != NULL)
  85                &&
  86                (spi_match(ahinfo->spis[0], ahinfo->spis[1],
  87                           ntohl(ah->spi),
  88                           !!(ahinfo->invflags & IP6T_AH_INV_SPI)))
  89                &&
  90                (!ahinfo->hdrlen ||
  91                 (ahinfo->hdrlen == hdrlen) ^
  92                 !!(ahinfo->invflags & IP6T_AH_INV_LEN))
  93                &&
  94                !(ahinfo->hdrres && ah->reserved);
  95 }
  96
  97 /* Called when user tries to insert an entry of this type. */
  98 static int
  99 checkentry(const char *tablename,
 100           const struct ip6t_ip6 *ip,
 101           void *matchinfo,
 102           unsigned int matchinfosize,
 103           unsigned int hook_mask)
 104 {
 105         const struct ip6t_ah *ahinfo = matchinfo;
 106
 107         if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_ah))) {
 108                 DEBUGP("ip6t_ah: matchsize %u != %u\n",
 109                        matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_ah)));
 110                 return 0;
 111         }
 112         if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 113                 DEBUGP("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
 114                 return 0;
 115         }
 116         return 1;
 117 }
 118
 119 static struct ip6t_match ah_match = {
 120         .name           = "ah",
 121         .match          = &match,
 122         .checkentry     = &checkentry,
 123         .me             = THIS_MODULE,
 124 };
 125
 126 static int __init init(void)
 127 {
 128         return ip6t_register_match(&ah_match);
 129 }
 130
 131 static void __exit cleanup(void)
 132 {
 133         ip6t_unregister_match(&ah_match);
 134 }
 135
 136 module_init(init);
 137 module_exit(cleanup);