net/ipv6/netfilter/ip6t_esp.c

   1 /* Kernel module to match ESP parameters. */
   2 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   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_esp.h>
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_DESCRIPTION("IPv6 ESP 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("esp 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       const void *protohdr,
  49       u_int16_t datalen,
  50       int *hotdrop)
  51 {
  52         struct ip_esp_hdr *esp = NULL;
  53         const struct ip6t_esp *espinfo = matchinfo;
  54         unsigned int temp;
  55         int len;
  56         u8 nexthdr;
  57         unsigned int ptr;
  58
  59         /* Make sure this isn't an evil packet */
  60         /*DEBUGP("ipv6_esp entered \n");*/
  61
  62         /* type of the 1st exthdr */
  63         nexthdr = skb->nh.ipv6h->nexthdr;
  64         /* pointer to the 1st exthdr */
  65         ptr = sizeof(struct ipv6hdr);
  66         /* available length */
  67         len = skb->len - ptr;
  68         temp = 0;
  69
  70         while (ip6t_ext_hdr(nexthdr)) {
  71                 struct ipv6_opt_hdr *hdr;
  72                 int hdrlen;
  73
  74                 DEBUGP("ipv6_esp header iteration \n");
  75
  76                 /* Is there enough space for the next ext header? */
  77                 if (len < (int)sizeof(struct ipv6_opt_hdr))
  78                         return 0;
  79                 /* No more exthdr -> evaluate */
  80                 if (nexthdr == NEXTHDR_NONE) {
  81                         break;
  82                 }
  83                 /* ESP -> evaluate */
  84                 if (nexthdr == NEXTHDR_ESP) {
  85                         temp |= MASK_ESP;
  86                         break;
  87                 }
  88
  89                 hdr=(struct ipv6_opt_hdr *)skb->data+ptr;
  90
  91                 /* Calculate the header length */
  92                 if (nexthdr == NEXTHDR_FRAGMENT) {
  93                         hdrlen = 8;
  94                 } else if (nexthdr == NEXTHDR_AUTH)
  95                         hdrlen = (hdr->hdrlen+2)<<2;
  96                 else
  97                         hdrlen = ipv6_optlen(hdr);
  98
  99                 /* set the flag */
 100                 switch (nexthdr){
 101                         case NEXTHDR_HOP:
 102                         case NEXTHDR_ROUTING:
 103                         case NEXTHDR_FRAGMENT:
 104                         case NEXTHDR_AUTH:
 105                         case NEXTHDR_DEST:
 106                                 break;
 107                         default:
 108                                 DEBUGP("ipv6_esp match: unknown nextheader %u\n",nexthdr);
 109                                 return 0;
 110                                 break;
 111                 }
 112
 113                 nexthdr = hdr->nexthdr;
 114                 len -= hdrlen;
 115                 ptr += hdrlen;
 116                 if ( ptr > skb->len ) {
 117                         DEBUGP("ipv6_esp: new pointer too large! \n");
 118                         break;
 119                 }
 120         }
 121
 122         /* ESP header not found */
 123         if ( temp != MASK_ESP ) return 0;
 124
 125        if (len < (int)sizeof(struct ip_esp_hdr)){
 126                *hotdrop = 1;
 127                 return 0;
 128        }
 129
 130         esp = (struct ip_esp_hdr *) (skb->data + ptr);
 131
 132         DEBUGP("IPv6 ESP SPI %u %08X\n", ntohl(esp->spi), ntohl(esp->spi));
 133
 134         return (esp != NULL)
 135                 && spi_match(espinfo->spis[0], espinfo->spis[1],
 136                               ntohl(esp->spi),
 137                               !!(espinfo->invflags & IP6T_ESP_INV_SPI));
 138 }
 139
 140 /* Called when user tries to insert an entry of this type. */
 141 static int
 142 checkentry(const char *tablename,
 143            const struct ip6t_ip6 *ip,
 144            void *matchinfo,
 145            unsigned int matchinfosize,
 146            unsigned int hook_mask)
 147 {
 148         const struct ip6t_esp *espinfo = matchinfo;
 149
 150         if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_esp))) {
 151                 DEBUGP("ip6t_esp: matchsize %u != %u\n",
 152                          matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_esp)));
 153                 return 0;
 154         }
 155         if (espinfo->invflags & ~IP6T_ESP_INV_MASK) {
 156                 DEBUGP("ip6t_esp: unknown flags %X\n",
 157                          espinfo->invflags);
 158                 return 0;
 159         }
 160
 161         return 1;
 162 }
 163
 164 static struct ip6t_match esp_match = {
 165         .name           = "esp",
 166         .match          = &match,
 167         .checkentry     = &checkentry,
 168         .me             = THIS_MODULE,
 169 };
 170
 171 static int __init init(void)
 172 {
 173         return ip6t_register_match(&esp_match);
 174 }
 175
 176 static void __exit cleanup(void)
 177 {
 178         ip6t_unregister_match(&esp_match);
 179 }
 180
 181 module_init(init);
 182 module_exit(cleanup);