summaryrefslogtreecommitdiff
path: root/net/ipv6/netfilter/ip6t_ah.c
blob: d5b94f142bbaed3b96d2c939d919ea979e12bc6e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
/* Kernel module to match AH parameters. */

/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ipv6.h>
#include <linux/types.h>
#include <net/checksum.h>
#include <net/ipv6.h>

#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_ipv6/ip6t_ah.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("IPv6 AH match");
MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");

#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif

/* Returns 1 if the spi is matched by the range, 0 otherwise */
static inline int
spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
{
	int r=0;
	DEBUGP("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
	       min,spi,max);
	r = (spi >= min && spi <= max) ^ invert;
	DEBUGP(" result %s\n",r? "PASS\n" : "FAILED\n");
	return r;
}

static int
match(const struct sk_buff *skb,
      const struct net_device *in,
      const struct net_device *out,
      const void *matchinfo,
      int offset,
      unsigned int protoff,
      int *hotdrop)
{
	struct ip_auth_hdr *ah = NULL, _ah;
	const struct ip6t_ah *ahinfo = matchinfo;
	unsigned int temp;
	int len;
	u8 nexthdr;
	unsigned int ptr;
	unsigned int hdrlen = 0;

	/*DEBUGP("IPv6 AH entered\n");*/
	/* if (opt->auth == 0) return 0;
	* It does not filled on output */

	/* type of the 1st exthdr */
	nexthdr = skb->nh.ipv6h->nexthdr;
	/* pointer to the 1st exthdr */
	ptr = sizeof(struct ipv6hdr);
	/* available length */
	len = skb->len - ptr;
	temp = 0;

	while (ip6t_ext_hdr(nexthdr)) {
		struct ipv6_opt_hdr _hdr, *hp;

		DEBUGP("ipv6_ah header iteration \n");

		/* Is there enough space for the next ext header? */
		if (len < sizeof(struct ipv6_opt_hdr))
			return 0;
		/* No more exthdr -> evaluate */
		if (nexthdr == NEXTHDR_NONE)
			break;
		/* ESP -> evaluate */
		if (nexthdr == NEXTHDR_ESP)
			break;

		hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
		BUG_ON(hp == NULL);

		/* Calculate the header length */
		if (nexthdr == NEXTHDR_FRAGMENT)
			hdrlen = 8;
		else if (nexthdr == NEXTHDR_AUTH)
			hdrlen = (hp->hdrlen+2)<<2;
		else
			hdrlen = ipv6_optlen(hp);

		/* AH -> evaluate */
		if (nexthdr == NEXTHDR_AUTH) {
			temp |= MASK_AH;
			break;
		}

		
		/* set the flag */
		switch (nexthdr) {
		case NEXTHDR_HOP:
		case NEXTHDR_ROUTING:
		case NEXTHDR_FRAGMENT:
		case NEXTHDR_AUTH:
		case NEXTHDR_DEST:
			break;
		default:
			DEBUGP("ipv6_ah match: unknown nextheader %u\n",nexthdr);
			return 0;
		}

		nexthdr = hp->nexthdr;
		len -= hdrlen;
		ptr += hdrlen;
		if (ptr > skb->len) {
			DEBUGP("ipv6_ah: new pointer too large! \n");
			break;
		}
	}

	/* AH header not found */
	if (temp != MASK_AH)
		return 0;

	if (len < sizeof(struct ip_auth_hdr)){
		*hotdrop = 1;
		return 0;
	}

	ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
	BUG_ON(ah == NULL);

	DEBUGP("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
	DEBUGP("RES %04X ", ah->reserved);
	DEBUGP("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));

	DEBUGP("IPv6 AH spi %02X ",
	       (spi_match(ahinfo->spis[0], ahinfo->spis[1],
	                  ntohl(ah->spi),
	                  !!(ahinfo->invflags & IP6T_AH_INV_SPI))));
	DEBUGP("len %02X %04X %02X ",
	       ahinfo->hdrlen, hdrlen,
	       (!ahinfo->hdrlen ||
	        (ahinfo->hdrlen == hdrlen) ^
	        !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
	DEBUGP("res %02X %04X %02X\n",
	       ahinfo->hdrres, ah->reserved,
	       !(ahinfo->hdrres && ah->reserved));

	return (ah != NULL)
	       &&
	       (spi_match(ahinfo->spis[0], ahinfo->spis[1],
	                  ntohl(ah->spi),
	                  !!(ahinfo->invflags & IP6T_AH_INV_SPI)))
	       &&
	       (!ahinfo->hdrlen ||
	        (ahinfo->hdrlen == hdrlen) ^
	        !!(ahinfo->invflags & IP6T_AH_INV_LEN))
	       &&
	       !(ahinfo->hdrres && ah->reserved);
}

/* Called when user tries to insert an entry of this type. */
static int
checkentry(const char *tablename,
          const struct ip6t_ip6 *ip,
          void *matchinfo,
          unsigned int matchinfosize,
          unsigned int hook_mask)
{
	const struct ip6t_ah *ahinfo = matchinfo;

	if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_ah))) {
		DEBUGP("ip6t_ah: matchsize %u != %u\n",
		       matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_ah)));
		return 0;
	}
	if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
		DEBUGP("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
		return 0;
	}
	return 1;
}

static struct ip6t_match ah_match = {
	.name		= "ah",
	.match		= &match,
	.checkentry	= &checkentry,
	.me		= THIS_MODULE,
};

static int __init init(void)
{
	return ip6t_register_match(&ah_match);
}

static void __exit cleanup(void)
{
	ip6t_unregister_match(&ah_match);
}

module_init(init);
module_exit(cleanup);