1 /* Kernel module to match Hop-by-Hop and Destination parameters. */
2
3 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 */
9
10 #include <linux/module.h>
11 #include <linux/skbuff.h>
12 #include <linux/ipv6.h>
13 #include <linux/types.h>
14 #include <net/checksum.h>
15 #include <net/ipv6.h>
16
17 #include <asm/byteorder.h>
18
19 #include <linux/netfilter/x_tables.h>
20 #include <linux/netfilter_ipv6/ip6_tables.h>
21 #include <linux/netfilter_ipv6/ip6t_opts.h>
22
23 MODULE_LICENSE("GPL");
24 MODULE_DESCRIPTION("Xtables: IPv6 Hop-By-Hop and Destination Header match");
25 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
26 MODULE_ALIAS("ip6t_dst");
27
28 /*
29 * (Type & 0xC0) >> 6
30 * 0 -> ignorable
31 * 1 -> must drop the packet
32 * 2 -> send ICMP PARM PROB regardless and drop packet
33 * 3 -> Send ICMP if not a multicast address and drop packet
34 * (Type & 0x20) >> 5
35 * 0 -> invariant
36 * 1 -> can change the routing
37 * (Type & 0x1F) Type
38 * 0 -> Pad1 (only 1 byte!)
39 * 1 -> PadN LENGTH info (total length = length + 2)
40 * C0 | 2 -> JUMBO 4 x x x x ( xxxx > 64k )
41 * 5 -> RTALERT 2 x x
42 */
43
44 static bool
45 hbh_mt6(const struct sk_buff *skb, const struct xt_match_param *par)
46 {
47 struct ipv6_opt_hdr _optsh;
48 const struct ipv6_opt_hdr *oh;
49 const struct ip6t_opts *optinfo = par->matchinfo;
50 unsigned int temp;
51 unsigned int ptr;
52 unsigned int hdrlen = 0;
53 bool ret = false;
54 u8 _opttype;
55 u8 _optlen;
56 const u_int8_t *tp = NULL;
57 const u_int8_t *lp = NULL;
58 unsigned int optlen;
59 int err;
60
61 err = ipv6_find_hdr(skb, &ptr, par->match->data, NULL);
62 if (err < 0) {
63 if (err != -ENOENT)
64 *par->hotdrop = true;
65 return false;
66 }
67
68 oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh);
69 if (oh == NULL) {
70 *par->hotdrop = true;
71 return false;
72 }
73
74 hdrlen = ipv6_optlen(oh);
75 if (skb->len - ptr < hdrlen) {
76 /* Packet smaller than it's length field */
77 return false;
78 }
79
80 pr_debug("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen);
81
82 pr_debug("len %02X %04X %02X ",
83 optinfo->hdrlen, hdrlen,
84 (!(optinfo->flags & IP6T_OPTS_LEN) ||
85 ((optinfo->hdrlen == hdrlen) ^
86 !!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
87
88 ret = (oh != NULL) &&
89 (!(optinfo->flags & IP6T_OPTS_LEN) ||
90 ((optinfo->hdrlen == hdrlen) ^
91 !!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
92
93 ptr += 2;
94 hdrlen -= 2;
95 if (!(optinfo->flags & IP6T_OPTS_OPTS)) {
96 return ret;
97 } else {
98 pr_debug("Strict ");
99 pr_debug("#%d ", optinfo->optsnr);
100 for (temp = 0; temp < optinfo->optsnr; temp++) {
101 /* type field exists ? */
102 if (hdrlen < 1)
103 break;
104 tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
105 &_opttype);
106 if (tp == NULL)
107 break;
108
109 /* Type check */
110 if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8) {
111 pr_debug("Tbad %02X %02X\n", *tp,
112 (optinfo->opts[temp] & 0xFF00) >> 8);
113 return false;
114 } else {
115 pr_debug("Tok ");
116 }
117 /* Length check */
118 if (*tp) {
119 u16 spec_len;
120
121 /* length field exists ? */
122 if (hdrlen < 2)
123 break;
124 lp = skb_header_pointer(skb, ptr + 1,
125 sizeof(_optlen),
126 &_optlen);
127 if (lp == NULL)
128 break;
129 spec_len = optinfo->opts[temp] & 0x00FF;
130
131 if (spec_len != 0x00FF && spec_len != *lp) {
132 pr_debug("Lbad %02X %04X\n", *lp,
133 spec_len);
134 return false;
135 }
136 pr_debug("Lok ");
137 optlen = *lp + 2;
138 } else {
139 pr_debug("Pad1\n");
140 optlen = 1;
141 }
142
143 /* Step to the next */
144 pr_debug("len%04X \n", optlen);
145
146 if ((ptr > skb->len - optlen || hdrlen < optlen) &&
147 temp < optinfo->optsnr - 1) {
148 pr_debug("new pointer is too large! \n");
149 break;
150 }
151 ptr += optlen;
152 hdrlen -= optlen;
153 }
154 if (temp == optinfo->optsnr)
155 return ret;
156 else
157 return false;
158 }
159
160 return false;
161 }
162
163 static bool hbh_mt6_check(const struct xt_mtchk_param *par)
164 {
165 const struct ip6t_opts *optsinfo = par->matchinfo;
166
167 if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
168 pr_debug("ip6t_opts: unknown flags %X\n", optsinfo->invflags);
169 return false;
170 }
171
172 if (optsinfo->flags & IP6T_OPTS_NSTRICT) {
173 pr_debug("ip6t_opts: Not strict - not implemented");
174 return false;
175 }
176
177 return true;
178 }
179
180 static struct xt_match hbh_mt6_reg[] __read_mostly = {
181 {
182 .name = "hbh",
183 .family = NFPROTO_IPV6,
184 .match = hbh_mt6,
185 .matchsize = sizeof(struct ip6t_opts),
186 .checkentry = hbh_mt6_check,
187 .me = THIS_MODULE,
188 .data = NEXTHDR_HOP,
189 },
190 {
191 .name = "dst",
192 .family = NFPROTO_IPV6,
193 .match = hbh_mt6,
194 .matchsize = sizeof(struct ip6t_opts),
195 .checkentry = hbh_mt6_check,
196 .me = THIS_MODULE,
197 .data = NEXTHDR_DEST,
198 },
199 };
200
201 static int __init hbh_mt6_init(void)
202 {
203 return xt_register_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
204 }
205
206 static void __exit hbh_mt6_exit(void)
207 {
208 xt_unregister_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
209 }
210
211 module_init(hbh_mt6_init);
212 module_exit(hbh_mt6_exit);
213
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