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 struct xt_match *match,
  48       const void *matchinfo,
  49       int offset,
  50       unsigned int protoff,
  51       int *hotdrop)
  52 {
  53         struct ip_auth_hdr *ah, _ah;
  54         const struct ip6t_ah *ahinfo = matchinfo;
  55         unsigned int ptr;
  56         unsigned int hdrlen = 0;
  57         int err;
  58
  59         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL);
  60         if (err < 0) {
  61                 if (err != -ENOENT)
  62                         *hotdrop = 1;
  63                 return 0;
  64         }
  65
  66         ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
  67         if (ah == NULL) {
  68                 *hotdrop = 1;
  69                 return 0;
  70         }
  71
  72         hdrlen = (ah->hdrlen + 2) << 2;
  73
  74         DEBUGP("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
  75         DEBUGP("RES %04X ", ah->reserved);
  76         DEBUGP("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
  77
  78         DEBUGP("IPv6 AH spi %02X ",
  79                (spi_match(ahinfo->spis[0], ahinfo->spis[1],
  80                           ntohl(ah->spi),
  81                           !!(ahinfo->invflags & IP6T_AH_INV_SPI))));
  82         DEBUGP("len %02X %04X %02X ",
  83                ahinfo->hdrlen, hdrlen,
  84                (!ahinfo->hdrlen ||
  85                 (ahinfo->hdrlen == hdrlen) ^
  86                 !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
  87         DEBUGP("res %02X %04X %02X\n",
  88                ahinfo->hdrres, ah->reserved,
  89                !(ahinfo->hdrres && ah->reserved));
  90
  91         return (ah != NULL)
  92                &&
  93                (spi_match(ahinfo->spis[0], ahinfo->spis[1],
  94                           ntohl(ah->spi),
  95                           !!(ahinfo->invflags & IP6T_AH_INV_SPI)))
  96                &&
  97                (!ahinfo->hdrlen ||
  98                 (ahinfo->hdrlen == hdrlen) ^
  99                 !!(ahinfo->invflags & IP6T_AH_INV_LEN))
 100                &&
 101                !(ahinfo->hdrres && ah->reserved);
 102 }
 103
 104 /* Called when user tries to insert an entry of this type. */
 105 static int
 106 checkentry(const char *tablename,
 107           const void *entry,
 108           const struct xt_match *match,
 109           void *matchinfo,
 110           unsigned int hook_mask)
 111 {
 112         const struct ip6t_ah *ahinfo = matchinfo;
 113
 114         if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 115                 DEBUGP("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
 116                 return 0;
 117         }
 118         return 1;
 119 }
 120
 121 static struct ip6t_match ah_match = {
 122         .name           = "ah",
 123         .match          = match,
 124         .matchsize      = sizeof(struct ip6t_ah),
 125         .checkentry     = checkentry,
 126         .me             = THIS_MODULE,
 127 };
 128
 129 static int __init ip6t_ah_init(void)
 130 {
 131         return ip6t_register_match(&ah_match);
 132 }
 133
 134 static void __exit ip6t_ah_fini(void)
 135 {
 136         ip6t_unregister_match(&ah_match);
 137 }
 138
 139 module_init(ip6t_ah_init);
 140 module_exit(ip6t_ah_fini);