LXR linux/net/ipv6/netfilter/ip6t

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* Kernel module to match FRAG 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 <linux/netfilter/x_tables.h>
  15#include <linux/netfilter_ipv6/ip6_tables.h>
  16#include <linux/netfilter_ipv6/ip6t_frag.h>
  17
  18MODULE_LICENSE("GPL");
  19MODULE_DESCRIPTION("Xtables: IPv6 fragment match");
  20MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  21
  22/* Returns 1 if the id is matched by the range, 0 otherwise */
  23static inline bool
  24id_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
  25{
  26        bool r;
  27        pr_debug("id_match:%c 0x%x <= 0x%x <= 0x%x\n", invert ? '!' : ' ',
  28                 min, id, max);
  29        r = (id >= min && id <= max) ^ invert;
  30        pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  31        return r;
  32}
  33
  34static bool
  35frag_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  36{
  37        struct frag_hdr _frag;
  38        const struct frag_hdr *fh;
  39        const struct ip6t_frag *fraginfo = par->matchinfo;
  40        unsigned int ptr = 0;
  41        int err;
  42
  43        err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL, NULL);
  44        if (err < 0) {
  45                if (err != -ENOENT)
  46                        par->hotdrop = true;
  47                return false;
  48        }
  49
  50        fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
  51        if (fh == NULL) {
  52                par->hotdrop = true;
  53                return false;
  54        }
  55
  56        pr_debug("INFO %04X ", fh->frag_off);
  57        pr_debug("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
  58        pr_debug("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
  59        pr_debug("MF %04X ", fh->frag_off & htons(IP6_MF));
  60        pr_debug("ID %u %08X\n", ntohl(fh->identification),
  61                 ntohl(fh->identification));
  62
  63        pr_debug("IPv6 FRAG id %02X ",
  64                 id_match(fraginfo->ids[0], fraginfo->ids[1],
  65                          ntohl(fh->identification),
  66                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)));
  67        pr_debug("res %02X %02X%04X %02X ",
  68                 fraginfo->flags & IP6T_FRAG_RES, fh->reserved,
  69                 ntohs(fh->frag_off) & 0x6,
  70                 !((fraginfo->flags & IP6T_FRAG_RES) &&
  71                   (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
  72        pr_debug("first %02X %02X %02X ",
  73                 fraginfo->flags & IP6T_FRAG_FST,
  74                 ntohs(fh->frag_off) & ~0x7,
  75                 !((fraginfo->flags & IP6T_FRAG_FST) &&
  76                   (ntohs(fh->frag_off) & ~0x7)));
  77        pr_debug("mf %02X %02X %02X ",
  78                 fraginfo->flags & IP6T_FRAG_MF,
  79                 ntohs(fh->frag_off) & IP6_MF,
  80                 !((fraginfo->flags & IP6T_FRAG_MF) &&
  81                   !((ntohs(fh->frag_off) & IP6_MF))));
  82        pr_debug("last %02X %02X %02X\n",
  83                 fraginfo->flags & IP6T_FRAG_NMF,
  84                 ntohs(fh->frag_off) & IP6_MF,
  85                 !((fraginfo->flags & IP6T_FRAG_NMF) &&
  86                   (ntohs(fh->frag_off) & IP6_MF)));
  87
  88        return (fh != NULL) &&
  89                id_match(fraginfo->ids[0], fraginfo->ids[1],
  90                         ntohl(fh->identification),
  91                         !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)) &&
  92                !((fraginfo->flags & IP6T_FRAG_RES) &&
  93                  (fh->reserved || (ntohs(fh->frag_off) & 0x6))) &&
  94                !((fraginfo->flags & IP6T_FRAG_FST) &&
  95                  (ntohs(fh->frag_off) & ~0x7)) &&
  96                !((fraginfo->flags & IP6T_FRAG_MF) &&
  97                  !(ntohs(fh->frag_off) & IP6_MF)) &&
  98                !((fraginfo->flags & IP6T_FRAG_NMF) &&
  99                  (ntohs(fh->frag_off) & IP6_MF));
 100}
 101
 102static int frag_mt6_check(const struct xt_mtchk_param *par)
 103{
 104        const struct ip6t_frag *fraginfo = par->matchinfo;
 105
 106        if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
 107                pr_debug("unknown flags %X\n", fraginfo->invflags);
 108                return -EINVAL;
 109        }
 110        return 0;
 111}
 112
 113static struct xt_match frag_mt6_reg __read_mostly = {
 114        .name           = "frag",
 115        .family         = NFPROTO_IPV6,
 116        .match          = frag_mt6,
 117        .matchsize      = sizeof(struct ip6t_frag),
 118        .checkentry     = frag_mt6_check,
 119        .me             = THIS_MODULE,
 120};
 121
 122static int __init frag_mt6_init(void)
 123{
 124        return xt_register_match(&frag_mt6_reg);
 125}
 126
 127static void __exit frag_mt6_exit(void)
 128{
 129        xt_unregister_match(&frag_mt6_reg);
 130}
 131
 132module_init(frag_mt6_init);
 133module_exit(frag_mt6_exit);
 134