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       const void *protohdr,
  49       u_int16_t datalen,
  50       int *hotdrop)
  51 {
  52        struct ip_auth_hdr *ah = NULL;
  53        const struct ip6t_ah *ahinfo = matchinfo;
  54        unsigned int temp;
  55        int len;
  56        u8 nexthdr;
  57        unsigned int ptr;
  58        unsigned int hdrlen = 0;
  59
  60        /*DEBUGP("IPv6 AH entered\n");*/
  61        /* if (opt->auth == 0) return 0;
  62        * It does not filled on output */
  63
  64        /* type of the 1st exthdr */
  65        nexthdr = skb->nh.ipv6h->nexthdr;
  66        /* pointer to the 1st exthdr */
  67        ptr = sizeof(struct ipv6hdr);
  68        /* available length */
  69        len = skb->len - ptr;
  70        temp = 0;
  71
  72         while (ip6t_ext_hdr(nexthdr)) {
  73                struct ipv6_opt_hdr *hdr;
  74
  75               DEBUGP("ipv6_ah header iteration \n");
  76
  77               /* Is there enough space for the next ext header? */
  78                 if (len < (int)sizeof(struct ipv6_opt_hdr))
  79                         return 0;
  80               /* No more exthdr -> evaluate */
  81                 if (nexthdr == NEXTHDR_NONE) {
  82                      break;
  83               }
  84               /* ESP -> evaluate */
  85                 if (nexthdr == NEXTHDR_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               /* AH -> evaluate */
 100                 if (nexthdr == NEXTHDR_AUTH) {
 101                      temp |= MASK_AH;
 102                      break;
 103               }
 104
 105
 106               /* set the flag */
 107               switch (nexthdr){
 108                      case NEXTHDR_HOP:
 109                      case NEXTHDR_ROUTING:
 110                      case NEXTHDR_FRAGMENT:
 111                      case NEXTHDR_AUTH:
 112                      case NEXTHDR_DEST:
 113                             break;
 114                      default:
 115                             DEBUGP("ipv6_ah match: unknown nextheader %u\n",nexthdr);
 116                             return 0;
 117                             break;
 118               }
 119
 120                 nexthdr = hdr->nexthdr;
 121                 len -= hdrlen;
 122                 ptr += hdrlen;
 123                 if ( ptr > skb->len ) {
 124                         DEBUGP("ipv6_ah: new pointer too large! \n");
 125                         break;
 126                 }
 127         }
 128
 129        /* AH header not found */
 130        if ( temp != MASK_AH ) return 0;
 131
 132        if (len < (int)sizeof(struct ip_auth_hdr)){
 133                *hotdrop = 1;
 134                 return 0;
 135        }
 136
 137        ah = (struct ip_auth_hdr *) (skb->data + ptr);
 138
 139        DEBUGP("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
 140        DEBUGP("RES %04X ", ah->reserved);
 141        DEBUGP("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
 142
 143        DEBUGP("IPv6 AH spi %02X ",
 144                 (spi_match(ahinfo->spis[0], ahinfo->spis[1],
 145                            ntohl(ah->spi),
 146                            !!(ahinfo->invflags & IP6T_AH_INV_SPI))));
 147        DEBUGP("len %02X %04X %02X ",
 148                 ahinfo->hdrlen, hdrlen,
 149                 (!ahinfo->hdrlen ||
 150                            (ahinfo->hdrlen == hdrlen) ^
 151                            !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
 152        DEBUGP("res %02X %04X %02X\n",
 153                 ahinfo->hdrres, ah->reserved,
 154                 !(ahinfo->hdrres && ah->reserved));
 155
 156        return (ah != NULL)
 157               &&
 158               (spi_match(ahinfo->spis[0], ahinfo->spis[1],
 159                            ntohl(ah->spi),
 160                            !!(ahinfo->invflags & IP6T_AH_INV_SPI)))
 161               &&
 162               (!ahinfo->hdrlen ||
 163                            (ahinfo->hdrlen == hdrlen) ^
 164                            !!(ahinfo->invflags & IP6T_AH_INV_LEN))
 165               &&
 166               !(ahinfo->hdrres && ah->reserved);
 167 }
 168
 169 /* Called when user tries to insert an entry of this type. */
 170 static int
 171 checkentry(const char *tablename,
 172           const struct ip6t_ip6 *ip,
 173           void *matchinfo,
 174           unsigned int matchinfosize,
 175           unsigned int hook_mask)
 176 {
 177        const struct ip6t_ah *ahinfo = matchinfo;
 178
 179        if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_ah))) {
 180               DEBUGP("ip6t_ah: matchsize %u != %u\n",
 181                       matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_ah)));
 182               return 0;
 183        }
 184        if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 185               DEBUGP("ip6t_ah: unknown flags %X\n",
 186                       ahinfo->invflags);
 187               return 0;
 188        }
 189
 190        return 1;
 191 }
 192
 193 static struct ip6t_match ah_match = {
 194         .name           = "ah",
 195         .match          = &match,
 196         .checkentry     = &checkentry,
 197         .me             = THIS_MODULE,
 198 };
 199
 200 static int __init init(void)
 201 {
 202        return ip6t_register_match(&ah_match);
 203 }
 204
 205 static void __exit cleanup(void)
 206 {
 207        ip6t_unregister_match(&ah_match);
 208 }
 209
 210 module_init(init);
 211 module_exit(cleanup);