net/ipv6/netfilter/ip6t_rt.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Kernel module to match ROUTING parameters. */
   3
   4 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
   5  */
   6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   7 #include <linux/module.h>
   8 #include <linux/skbuff.h>
   9 #include <linux/ipv6.h>
  10 #include <linux/types.h>
  11 #include <net/checksum.h>
  12 #include <net/ipv6.h>
  13
  14 #include <asm/byteorder.h>
  15
  16 #include <linux/netfilter/x_tables.h>
  17 #include <linux/netfilter_ipv6/ip6_tables.h>
  18 #include <linux/netfilter_ipv6/ip6t_rt.h>
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_DESCRIPTION("Xtables: IPv6 Routing Header match");
  22 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  23
  24 /* Returns 1 if the id is matched by the range, 0 otherwise */
  25 static inline bool
  26 segsleft_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
  27 {
  28         return (id >= min && id <= max) ^ invert;
  29 }
  30
  31 static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  32 {
  33         struct ipv6_rt_hdr _route;
  34         const struct ipv6_rt_hdr *rh;
  35         const struct ip6t_rt *rtinfo = par->matchinfo;
  36         unsigned int temp;
  37         unsigned int ptr = 0;
  38         unsigned int hdrlen = 0;
  39         bool ret = false;
  40         struct in6_addr _addr;
  41         const struct in6_addr *ap;
  42         int err;
  43
  44         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING, NULL, NULL);
  45         if (err < 0) {
  46                 if (err != -ENOENT)
  47                         par->hotdrop = true;
  48                 return false;
  49         }
  50
  51         rh = skb_header_pointer(skb, ptr, sizeof(_route), &_route);
  52         if (rh == NULL) {
  53                 par->hotdrop = true;
  54                 return false;
  55         }
  56
  57         hdrlen = ipv6_optlen(rh);
  58         if (skb->len - ptr < hdrlen) {
  59                 /* Pcket smaller than its length field */
  60                 return false;
  61         }
  62
  63         ret = (segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
  64                               rh->segments_left,
  65                               !!(rtinfo->invflags & IP6T_RT_INV_SGS))) &&
  66               (!(rtinfo->flags & IP6T_RT_LEN) ||
  67                ((rtinfo->hdrlen == hdrlen) ^
  68                 !!(rtinfo->invflags & IP6T_RT_INV_LEN))) &&
  69               (!(rtinfo->flags & IP6T_RT_TYP) ||
  70                ((rtinfo->rt_type == rh->type) ^
  71                 !!(rtinfo->invflags & IP6T_RT_INV_TYP)));
  72
  73         if (ret && (rtinfo->flags & IP6T_RT_RES)) {
  74                 const u_int32_t *rp;
  75                 u_int32_t _reserved;
  76                 rp = skb_header_pointer(skb,
  77                                         ptr + offsetof(struct rt0_hdr,
  78                                                        reserved),
  79                                         sizeof(_reserved),
  80                                         &_reserved);
  81                 if (!rp) {
  82                         par->hotdrop = true;
  83                         return false;
  84                 }
  85
  86                 ret = (*rp == 0);
  87         }
  88
  89         if (!(rtinfo->flags & IP6T_RT_FST)) {
  90                 return ret;
  91         } else if (rtinfo->flags & IP6T_RT_FST_NSTRICT) {
  92                 if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
  93                         return false;
  94                 } else {
  95                         unsigned int i = 0;
  96
  97                         for (temp = 0;
  98                              temp < (unsigned int)((hdrlen - 8) / 16);
  99                              temp++) {
 100                                 ap = skb_header_pointer(skb,
 101                                                         ptr
 102                                                         + sizeof(struct rt0_hdr)
 103                                                         + temp * sizeof(_addr),
 104                                                         sizeof(_addr),
 105                                                         &_addr);
 106
 107                                 if (ap == NULL) {
 108                                         par->hotdrop = true;
 109                                         return false;
 110                                 }
 111
 112                                 if (ipv6_addr_equal(ap, &rtinfo->addrs[i]))
 113                                         i++;
 114                                 if (i == rtinfo->addrnr)
 115                                         break;
 116                         }
 117                         if (i == rtinfo->addrnr)
 118                                 return ret;
 119                         else
 120                                 return false;
 121                 }
 122         } else {
 123                 if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
 124                         return false;
 125                 } else {
 126                         for (temp = 0; temp < rtinfo->addrnr; temp++) {
 127                                 ap = skb_header_pointer(skb,
 128                                                         ptr
 129                                                         + sizeof(struct rt0_hdr)
 130                                                         + temp * sizeof(_addr),
 131                                                         sizeof(_addr),
 132                                                         &_addr);
 133                                 if (ap == NULL) {
 134                                         par->hotdrop = true;
 135                                         return false;
 136                                 }
 137
 138                                 if (!ipv6_addr_equal(ap, &rtinfo->addrs[temp]))
 139                                         break;
 140                         }
 141                         if (temp == rtinfo->addrnr &&
 142                             temp == (unsigned int)((hdrlen - 8) / 16))
 143                                 return ret;
 144                         else
 145                                 return false;
 146                 }
 147         }
 148
 149         return false;
 150 }
 151
 152 static int rt_mt6_check(const struct xt_mtchk_param *par)
 153 {
 154         const struct ip6t_rt *rtinfo = par->matchinfo;
 155
 156         if (rtinfo->invflags & ~IP6T_RT_INV_MASK) {
 157                 pr_debug("unknown flags %X\n", rtinfo->invflags);
 158                 return -EINVAL;
 159         }
 160         if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) &&
 161             (!(rtinfo->flags & IP6T_RT_TYP) ||
 162              (rtinfo->rt_type != 0) ||
 163              (rtinfo->invflags & IP6T_RT_INV_TYP))) {
 164                 pr_debug("`--rt-type 0' required before `--rt-0-*'");
 165                 return -EINVAL;
 166         }
 167
 168         return 0;
 169 }
 170
 171 static struct xt_match rt_mt6_reg __read_mostly = {
 172         .name           = "rt",
 173         .family         = NFPROTO_IPV6,
 174         .match          = rt_mt6,
 175         .matchsize      = sizeof(struct ip6t_rt),
 176         .checkentry     = rt_mt6_check,
 177         .me             = THIS_MODULE,
 178 };
 179
 180 static int __init rt_mt6_init(void)
 181 {
 182         return xt_register_match(&rt_mt6_reg);
 183 }
 184
 185 static void __exit rt_mt6_exit(void)
 186 {
 187         xt_unregister_match(&rt_mt6_reg);
 188 }
 189
 190 module_init(rt_mt6_init);
 191 module_exit(rt_mt6_exit);