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);
133