ip6t_frag.c

  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 id_match(fraginfo->ids[0], fraginfo->ids[1],
 89			 ntohl(fh->identification),
 90			 !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)) &&
 91		!((fraginfo->flags & IP6T_FRAG_RES) &&
 92		  (fh->reserved || (ntohs(fh->frag_off) & 0x6))) &&
 93		!((fraginfo->flags & IP6T_FRAG_FST) &&
 94		  (ntohs(fh->frag_off) & ~0x7)) &&
 95		!((fraginfo->flags & IP6T_FRAG_MF) &&
 96		  !(ntohs(fh->frag_off) & IP6_MF)) &&
 97		!((fraginfo->flags & IP6T_FRAG_NMF) &&
 98		  (ntohs(fh->frag_off) & IP6_MF));
 99}
100
101static int frag_mt6_check(const struct xt_mtchk_param *par)
102{
103	const struct ip6t_frag *fraginfo = par->matchinfo;
104
105	if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
106		pr_debug("unknown flags %X\n", fraginfo->invflags);
107		return -EINVAL;
108	}
109	return 0;
110}
111
112static struct xt_match frag_mt6_reg __read_mostly = {
113	.name		= "frag",
114	.family		= NFPROTO_IPV6,
115	.match		= frag_mt6,
116	.matchsize	= sizeof(struct ip6t_frag),
117	.checkentry	= frag_mt6_check,
118	.me		= THIS_MODULE,
119};
120
121static int __init frag_mt6_init(void)
122{
123	return xt_register_match(&frag_mt6_reg);
124}
125
126static void __exit frag_mt6_exit(void)
127{
128	xt_unregister_match(&frag_mt6_reg);
129}
130
131module_init(frag_mt6_init);
132module_exit(frag_mt6_exit);