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_ipv6/ip6_tables.h>
  19 #include <linux/netfilter_ipv6/ip6t_ah.h>
  20
  21 MODULE_LICENSE("GPL");
  22 MODULE_DESCRIPTION("IPv6 AH match");
  23 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  24
  25 #if 0
  26 #define DEBUGP printk
  27 #else
  28 #define DEBUGP(format, args...)
  29 #endif
  30
  31 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  32 static inline int
  33 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
  34 {
  35         int r=0;
  36         DEBUGP("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
  37                min,spi,max);
  38         r = (spi >= min && spi <= max) ^ invert;
  39         DEBUGP(" result %s\n",r? "PASS\n" : "FAILED\n");
  40         return r;
  41 }
  42
  43 static int
  44 match(const struct sk_buff *skb,
  45       const struct net_device *in,
  46       const struct net_device *out,
  47       const void *matchinfo,
  48       int offset,
  49       unsigned int protoff,
  50       int *hotdrop)
  51 {
  52         struct ip_auth_hdr *ah, _ah;
  53         const struct ip6t_ah *ahinfo = matchinfo;
  54         unsigned int ptr;
  55         unsigned int hdrlen = 0;
  56
  57         if (ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL) < 0)
  58                 return 0;
  59
  60         ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
  61         if (ah == NULL) {
  62                 *hotdrop = 1;
  63                 return 0;
  64         }
  65
  66         hdrlen = (ah->hdrlen + 2) << 2;
  67
  68         DEBUGP("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
  69         DEBUGP("RES %04X ", ah->reserved);
  70         DEBUGP("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
  71
  72         DEBUGP("IPv6 AH spi %02X ",
  73                (spi_match(ahinfo->spis[0], ahinfo->spis[1],
  74                           ntohl(ah->spi),
  75                           !!(ahinfo->invflags & IP6T_AH_INV_SPI))));
  76         DEBUGP("len %02X %04X %02X ",
  77                ahinfo->hdrlen, hdrlen,
  78                (!ahinfo->hdrlen ||
  79                 (ahinfo->hdrlen == hdrlen) ^
  80                 !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
  81         DEBUGP("res %02X %04X %02X\n",
  82                ahinfo->hdrres, ah->reserved,
  83                !(ahinfo->hdrres && ah->reserved));
  84
  85         return (ah != NULL)
  86                &&
  87                (spi_match(ahinfo->spis[0], ahinfo->spis[1],
  88                           ntohl(ah->spi),
  89                           !!(ahinfo->invflags & IP6T_AH_INV_SPI)))
  90                &&
  91                (!ahinfo->hdrlen ||
  92                 (ahinfo->hdrlen == hdrlen) ^
  93                 !!(ahinfo->invflags & IP6T_AH_INV_LEN))
  94                &&
  95                !(ahinfo->hdrres && ah->reserved);
  96 }
  97
  98 /* Called when user tries to insert an entry of this type. */
  99 static int
 100 checkentry(const char *tablename,
 101           const void *entry,
 102           void *matchinfo,
 103           unsigned int matchinfosize,
 104           unsigned int hook_mask)
 105 {
 106         const struct ip6t_ah *ahinfo = matchinfo;
 107
 108         if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_ah))) {
 109                 DEBUGP("ip6t_ah: matchsize %u != %u\n",
 110                        matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_ah)));
 111                 return 0;
 112         }
 113         if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 114                 DEBUGP("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
 115                 return 0;
 116         }
 117         return 1;
 118 }
 119
 120 static struct ip6t_match ah_match = {
 121         .name           = "ah",
 122         .match          = &match,
 123         .checkentry     = &checkentry,
 124         .me             = THIS_MODULE,
 125 };
 126
 127 static int __init init(void)
 128 {
 129         return ip6t_register_match(&ah_match);
 130 }
 131
 132 static void __exit cleanup(void)
 133 {
 134         ip6t_unregister_match(&ah_match);
 135 }
 136
 137 module_init(init);
 138 module_exit(cleanup);