net/ipv6/netfilter/ip6t_hbh.c

   1 /* Kernel module to match Hop-by-Hop and Destination 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 <asm/byteorder.h>
  18
  19 #include <linux/netfilter/x_tables.h>
  20 #include <linux/netfilter_ipv6/ip6_tables.h>
  21 #include <linux/netfilter_ipv6/ip6t_opts.h>
  22
  23 MODULE_LICENSE("GPL");
  24 MODULE_DESCRIPTION("Xtables: IPv6 Hop-By-Hop and Destination Header match");
  25 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  26 MODULE_ALIAS("ip6t_dst");
  27
  28 /*
  29  *  (Type & 0xC0) >> 6
  30  *      0       -> ignorable
  31  *      1       -> must drop the packet
  32  *      2       -> send ICMP PARM PROB regardless and drop packet
  33  *      3       -> Send ICMP if not a multicast address and drop packet
  34  *  (Type & 0x20) >> 5
  35  *      0       -> invariant
  36  *      1       -> can change the routing
  37  *  (Type & 0x1F) Type
  38  *      0       -> Pad1 (only 1 byte!)
  39  *      1       -> PadN LENGTH info (total length = length + 2)
  40  *      C0 | 2  -> JUMBO 4 x x x x ( xxxx > 64k )
  41  *      5       -> RTALERT 2 x x
  42  */
  43
  44 static bool
  45 hbh_mt6(const struct sk_buff *skb, const struct xt_match_param *par)
  46 {
  47         struct ipv6_opt_hdr _optsh;
  48         const struct ipv6_opt_hdr *oh;
  49         const struct ip6t_opts *optinfo = par->matchinfo;
  50         unsigned int temp;
  51         unsigned int ptr;
  52         unsigned int hdrlen = 0;
  53         bool ret = false;
  54         u8 _opttype;
  55         u8 _optlen;
  56         const u_int8_t *tp = NULL;
  57         const u_int8_t *lp = NULL;
  58         unsigned int optlen;
  59         int err;
  60
  61         err = ipv6_find_hdr(skb, &ptr, par->match->data, NULL);
  62         if (err < 0) {
  63                 if (err != -ENOENT)
  64                         *par->hotdrop = true;
  65                 return false;
  66         }
  67
  68         oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh);
  69         if (oh == NULL) {
  70                 *par->hotdrop = true;
  71                 return false;
  72         }
  73
  74         hdrlen = ipv6_optlen(oh);
  75         if (skb->len - ptr < hdrlen) {
  76                 /* Packet smaller than it's length field */
  77                 return false;
  78         }
  79
  80         pr_debug("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen);
  81
  82         pr_debug("len %02X %04X %02X ",
  83                  optinfo->hdrlen, hdrlen,
  84                  (!(optinfo->flags & IP6T_OPTS_LEN) ||
  85                   ((optinfo->hdrlen == hdrlen) ^
  86                    !!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
  87
  88         ret = (oh != NULL) &&
  89               (!(optinfo->flags & IP6T_OPTS_LEN) ||
  90                ((optinfo->hdrlen == hdrlen) ^
  91                 !!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
  92
  93         ptr += 2;
  94         hdrlen -= 2;
  95         if (!(optinfo->flags & IP6T_OPTS_OPTS)) {
  96                 return ret;
  97         } else {
  98                 pr_debug("Strict ");
  99                 pr_debug("#%d ", optinfo->optsnr);
 100                 for (temp = 0; temp < optinfo->optsnr; temp++) {
 101                         /* type field exists ? */
 102                         if (hdrlen < 1)
 103                                 break;
 104                         tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
 105                                                 &_opttype);
 106                         if (tp == NULL)
 107                                 break;
 108
 109                         /* Type check */
 110                         if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8) {
 111                                 pr_debug("Tbad %02X %02X\n", *tp,
 112                                          (optinfo->opts[temp] & 0xFF00) >> 8);
 113                                 return false;
 114                         } else {
 115                                 pr_debug("Tok ");
 116                         }
 117                         /* Length check */
 118                         if (*tp) {
 119                                 u16 spec_len;
 120
 121                                 /* length field exists ? */
 122                                 if (hdrlen < 2)
 123                                         break;
 124                                 lp = skb_header_pointer(skb, ptr + 1,
 125                                                         sizeof(_optlen),
 126                                                         &_optlen);
 127                                 if (lp == NULL)
 128                                         break;
 129                                 spec_len = optinfo->opts[temp] & 0x00FF;
 130
 131                                 if (spec_len != 0x00FF && spec_len != *lp) {
 132                                         pr_debug("Lbad %02X %04X\n", *lp,
 133                                                  spec_len);
 134                                         return false;
 135                                 }
 136                                 pr_debug("Lok ");
 137                                 optlen = *lp + 2;
 138                         } else {
 139                                 pr_debug("Pad1\n");
 140                                 optlen = 1;
 141                         }
 142
 143                         /* Step to the next */
 144                         pr_debug("len%04X \n", optlen);
 145
 146                         if ((ptr > skb->len - optlen || hdrlen < optlen) &&
 147                             temp < optinfo->optsnr - 1) {
 148                                 pr_debug("new pointer is too large! \n");
 149                                 break;
 150                         }
 151                         ptr += optlen;
 152                         hdrlen -= optlen;
 153                 }
 154                 if (temp == optinfo->optsnr)
 155                         return ret;
 156                 else
 157                         return false;
 158         }
 159
 160         return false;
 161 }
 162
 163 static bool hbh_mt6_check(const struct xt_mtchk_param *par)
 164 {
 165         const struct ip6t_opts *optsinfo = par->matchinfo;
 166
 167         if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
 168                 pr_debug("ip6t_opts: unknown flags %X\n", optsinfo->invflags);
 169                 return false;
 170         }
 171
 172         if (optsinfo->flags & IP6T_OPTS_NSTRICT) {
 173                 pr_debug("ip6t_opts: Not strict - not implemented");
 174                 return false;
 175         }
 176
 177         return true;
 178 }
 179
 180 static struct xt_match hbh_mt6_reg[] __read_mostly = {
 181         {
 182                 .name           = "hbh",
 183                 .family         = NFPROTO_IPV6,
 184                 .match          = hbh_mt6,
 185                 .matchsize      = sizeof(struct ip6t_opts),
 186                 .checkentry     = hbh_mt6_check,
 187                 .me             = THIS_MODULE,
 188                 .data           = NEXTHDR_HOP,
 189         },
 190         {
 191                 .name           = "dst",
 192                 .family         = NFPROTO_IPV6,
 193                 .match          = hbh_mt6,
 194                 .matchsize      = sizeof(struct ip6t_opts),
 195                 .checkentry     = hbh_mt6_check,
 196                 .me             = THIS_MODULE,
 197                 .data           = NEXTHDR_DEST,
 198         },
 199 };
 200
 201 static int __init hbh_mt6_init(void)
 202 {
 203         return xt_register_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
 204 }
 205
 206 static void __exit hbh_mt6_exit(void)
 207 {
 208         xt_unregister_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
 209 }
 210
 211 module_init(hbh_mt6_init);
 212 module_exit(hbh_mt6_exit);