ip6t_ipv6header.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/* ipv6header match - matches IPv6 packets based
  3   on whether they contain certain headers */
  4
  5/* Original idea: Brad Chapman
  6 * Rewritten by: Andras Kis-Szabo <kisza@sch.bme.hu> */
  7
  8/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
  9 */
 10
 11#include <linux/module.h>
 12#include <linux/skbuff.h>
 13#include <linux/ipv6.h>
 14#include <linux/types.h>
 15#include <net/checksum.h>
 16#include <net/ipv6.h>
 17
 18#include <linux/netfilter/x_tables.h>
 19#include <linux/netfilter_ipv6.h>
 20#include <linux/netfilter_ipv6/ip6t_ipv6header.h>
 21
 22MODULE_LICENSE("GPL");
 23MODULE_DESCRIPTION("Xtables: IPv6 header types match");
 24MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
 25
 26static bool
 27ipv6header_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 28{
 29	const struct ip6t_ipv6header_info *info = par->matchinfo;
 30	unsigned int temp;
 31	int len;
 32	u8 nexthdr;
 33	unsigned int ptr;
 34
 35	/* Make sure this isn't an evil packet */
 36
 37	/* type of the 1st exthdr */
 38	nexthdr = ipv6_hdr(skb)->nexthdr;
 39	/* pointer to the 1st exthdr */
 40	ptr = sizeof(struct ipv6hdr);
 41	/* available length */
 42	len = skb->len - ptr;
 43	temp = 0;
 44
 45	while (nf_ip6_ext_hdr(nexthdr)) {
 46		const struct ipv6_opt_hdr *hp;
 47		struct ipv6_opt_hdr _hdr;
 48		int hdrlen;
 49
 50		/* No more exthdr -> evaluate */
 51		if (nexthdr == NEXTHDR_NONE) {
 52			temp |= MASK_NONE;
 53			break;
 54		}
 55		/* Is there enough space for the next ext header? */
 56		if (len < (int)sizeof(struct ipv6_opt_hdr))
 57			return false;
 58		/* ESP -> evaluate */
 59		if (nexthdr == NEXTHDR_ESP) {
 60			temp |= MASK_ESP;
 61			break;
 62		}
 63
 64		hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
 65		if (!hp) {
 66			par->hotdrop = true;
 67			return false;
 68		}
 69
 70		/* Calculate the header length */
 71		if (nexthdr == NEXTHDR_FRAGMENT)
 72			hdrlen = 8;
 73		else if (nexthdr == NEXTHDR_AUTH)
 74			hdrlen = ipv6_authlen(hp);
 75		else
 76			hdrlen = ipv6_optlen(hp);
 77
 78		/* set the flag */
 79		switch (nexthdr) {
 80		case NEXTHDR_HOP:
 81			temp |= MASK_HOPOPTS;
 82			break;
 83		case NEXTHDR_ROUTING:
 84			temp |= MASK_ROUTING;
 85			break;
 86		case NEXTHDR_FRAGMENT:
 87			temp |= MASK_FRAGMENT;
 88			break;
 89		case NEXTHDR_AUTH:
 90			temp |= MASK_AH;
 91			break;
 92		case NEXTHDR_DEST:
 93			temp |= MASK_DSTOPTS;
 94			break;
 95		default:
 96			return false;
 97		}
 98
 99		nexthdr = hp->nexthdr;
100		len -= hdrlen;
101		ptr += hdrlen;
102		if (ptr > skb->len)
103			break;
104	}
105
106	if (nexthdr != NEXTHDR_NONE && nexthdr != NEXTHDR_ESP)
107		temp |= MASK_PROTO;
108
109	if (info->modeflag)
110		return !((temp ^ info->matchflags ^ info->invflags)
111			 & info->matchflags);
112	else {
113		if (info->invflags)
114			return temp != info->matchflags;
115		else
116			return temp == info->matchflags;
117	}
118}
119
120static int ipv6header_mt6_check(const struct xt_mtchk_param *par)
121{
122	const struct ip6t_ipv6header_info *info = par->matchinfo;
123
124	/* invflags is 0 or 0xff in hard mode */
125	if ((!info->modeflag) && info->invflags != 0x00 &&
126	    info->invflags != 0xFF)
127		return -EINVAL;
128
129	return 0;
130}
131
132static struct xt_match ipv6header_mt6_reg __read_mostly = {
133	.name		= "ipv6header",
134	.family		= NFPROTO_IPV6,
135	.match		= ipv6header_mt6,
136	.matchsize	= sizeof(struct ip6t_ipv6header_info),
137	.checkentry	= ipv6header_mt6_check,
138	.destroy	= NULL,
139	.me		= THIS_MODULE,
140};
141
142static int __init ipv6header_mt6_init(void)
143{
144	return xt_register_match(&ipv6header_mt6_reg);
145}
146
147static void __exit ipv6header_mt6_exit(void)
148{
149	xt_unregister_match(&ipv6header_mt6_reg);
150}
151
152module_init(ipv6header_mt6_init);
153module_exit(ipv6header_mt6_exit);