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         bool r;
  29         pr_debug("segsleft_match:%c 0x%x <= 0x%x <= 0x%x\n",
  30                  invert ? '!' : ' ', min, id, max);
  31         r = (id >= min && id <= max) ^ invert;
  32         pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  33         return r;
  34 }
  35
  36 static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  37 {
  38         struct ipv6_rt_hdr _route;
  39         const struct ipv6_rt_hdr *rh;
  40         const struct ip6t_rt *rtinfo = par->matchinfo;
  41         unsigned int temp;
  42         unsigned int ptr = 0;
  43         unsigned int hdrlen = 0;
  44         bool ret = false;
  45         struct in6_addr _addr;
  46         const struct in6_addr *ap;
  47         int err;
  48
  49         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING, NULL, NULL);
  50         if (err < 0) {
  51                 if (err != -ENOENT)
  52                         par->hotdrop = true;
  53                 return false;
  54         }
  55
  56         rh = skb_header_pointer(skb, ptr, sizeof(_route), &_route);
  57         if (rh == NULL) {
  58                 par->hotdrop = true;
  59                 return false;
  60         }
  61
  62         hdrlen = ipv6_optlen(rh);
  63         if (skb->len - ptr < hdrlen) {
  64                 /* Pcket smaller than its length field */
  65                 return false;
  66         }
  67
  68         pr_debug("IPv6 RT LEN %u %u ", hdrlen, rh->hdrlen);
  69         pr_debug("TYPE %04X ", rh->type);
  70         pr_debug("SGS_LEFT %u %02X\n", rh->segments_left, rh->segments_left);
  71
  72         pr_debug("IPv6 RT segsleft %02X ",
  73                  segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
  74                                 rh->segments_left,
  75                                 !!(rtinfo->invflags & IP6T_RT_INV_SGS)));
  76         pr_debug("type %02X %02X %02X ",
  77                  rtinfo->rt_type, rh->type,
  78                  (!(rtinfo->flags & IP6T_RT_TYP) ||
  79                   ((rtinfo->rt_type == rh->type) ^
  80                    !!(rtinfo->invflags & IP6T_RT_INV_TYP))));
  81         pr_debug("len %02X %04X %02X ",
  82                  rtinfo->hdrlen, hdrlen,
  83                  !(rtinfo->flags & IP6T_RT_LEN) ||
  84                   ((rtinfo->hdrlen == hdrlen) ^
  85                    !!(rtinfo->invflags & IP6T_RT_INV_LEN)));
  86         pr_debug("res %02X %02X %02X ",
  87                  rtinfo->flags & IP6T_RT_RES,
  88                  ((const struct rt0_hdr *)rh)->reserved,
  89                  !((rtinfo->flags & IP6T_RT_RES) &&
  90                    (((const struct rt0_hdr *)rh)->reserved)));
  91
  92         ret = (rh != NULL) &&
  93               (segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
  94                               rh->segments_left,
  95                               !!(rtinfo->invflags & IP6T_RT_INV_SGS))) &&
  96               (!(rtinfo->flags & IP6T_RT_LEN) ||
  97                ((rtinfo->hdrlen == hdrlen) ^
  98                 !!(rtinfo->invflags & IP6T_RT_INV_LEN))) &&
  99               (!(rtinfo->flags & IP6T_RT_TYP) ||
 100                ((rtinfo->rt_type == rh->type) ^
 101                 !!(rtinfo->invflags & IP6T_RT_INV_TYP)));
 102
 103         if (ret && (rtinfo->flags & IP6T_RT_RES)) {
 104                 const u_int32_t *rp;
 105                 u_int32_t _reserved;
 106                 rp = skb_header_pointer(skb,
 107                                         ptr + offsetof(struct rt0_hdr,
 108                                                        reserved),
 109                                         sizeof(_reserved),
 110                                         &_reserved);
 111
 112                 ret = (*rp == 0);
 113         }
 114
 115         pr_debug("#%d ", rtinfo->addrnr);
 116         if (!(rtinfo->flags & IP6T_RT_FST)) {
 117                 return ret;
 118         } else if (rtinfo->flags & IP6T_RT_FST_NSTRICT) {
 119                 pr_debug("Not strict ");
 120                 if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
 121                         pr_debug("There isn't enough space\n");
 122                         return false;
 123                 } else {
 124                         unsigned int i = 0;
 125
 126                         pr_debug("#%d ", rtinfo->addrnr);
 127                         for (temp = 0;
 128                              temp < (unsigned int)((hdrlen - 8) / 16);
 129                              temp++) {
 130                                 ap = skb_header_pointer(skb,
 131                                                         ptr
 132                                                         + sizeof(struct rt0_hdr)
 133                                                         + temp * sizeof(_addr),
 134                                                         sizeof(_addr),
 135                                                         &_addr);
 136
 137                                 if (ap == NULL) {
 138                                         par->hotdrop = true;
 139                                         return false;
 140                                 }
 141
 142                                 if (ipv6_addr_equal(ap, &rtinfo->addrs[i])) {
 143                                         pr_debug("i=%d temp=%d;\n", i, temp);
 144                                         i++;
 145                                 }
 146                                 if (i == rtinfo->addrnr)
 147                                         break;
 148                         }
 149                         pr_debug("i=%d #%d\n", i, rtinfo->addrnr);
 150                         if (i == rtinfo->addrnr)
 151                                 return ret;
 152                         else
 153                                 return false;
 154                 }
 155         } else {
 156                 pr_debug("Strict ");
 157                 if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
 158                         pr_debug("There isn't enough space\n");
 159                         return false;
 160                 } else {
 161                         pr_debug("#%d ", rtinfo->addrnr);
 162                         for (temp = 0; temp < rtinfo->addrnr; temp++) {
 163                                 ap = skb_header_pointer(skb,
 164                                                         ptr
 165                                                         + sizeof(struct rt0_hdr)
 166                                                         + temp * sizeof(_addr),
 167                                                         sizeof(_addr),
 168                                                         &_addr);
 169                                 if (ap == NULL) {
 170                                         par->hotdrop = true;
 171                                         return false;
 172                                 }
 173
 174                                 if (!ipv6_addr_equal(ap, &rtinfo->addrs[temp]))
 175                                         break;
 176                         }
 177                         pr_debug("temp=%d #%d\n", temp, rtinfo->addrnr);
 178                         if (temp == rtinfo->addrnr &&
 179                             temp == (unsigned int)((hdrlen - 8) / 16))
 180                                 return ret;
 181                         else
 182                                 return false;
 183                 }
 184         }
 185
 186         return false;
 187 }
 188
 189 static int rt_mt6_check(const struct xt_mtchk_param *par)
 190 {
 191         const struct ip6t_rt *rtinfo = par->matchinfo;
 192
 193         if (rtinfo->invflags & ~IP6T_RT_INV_MASK) {
 194                 pr_debug("unknown flags %X\n", rtinfo->invflags);
 195                 return -EINVAL;
 196         }
 197         if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) &&
 198             (!(rtinfo->flags & IP6T_RT_TYP) ||
 199              (rtinfo->rt_type != 0) ||
 200              (rtinfo->invflags & IP6T_RT_INV_TYP))) {
 201                 pr_debug("`--rt-type 0' required before `--rt-0-*'");
 202                 return -EINVAL;
 203         }
 204
 205         return 0;
 206 }
 207
 208 static struct xt_match rt_mt6_reg __read_mostly = {
 209         .name           = "rt",
 210         .family         = NFPROTO_IPV6,
 211         .match          = rt_mt6,
 212         .matchsize      = sizeof(struct ip6t_rt),
 213         .checkentry     = rt_mt6_check,
 214         .me             = THIS_MODULE,
 215 };
 216
 217 static int __init rt_mt6_init(void)
 218 {
 219         return xt_register_match(&rt_mt6_reg);
 220 }
 221
 222 static void __exit rt_mt6_exit(void)
 223 {
 224         xt_unregister_match(&rt_mt6_reg);
 225 }
 226
 227 module_init(rt_mt6_init);
 228 module_exit(rt_mt6_exit);