1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Kernel module to match Hop-by-Hop and Destination 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 <asm/byteorder.h>
15
16 #include <linux/netfilter/x_tables.h>
17 #include <linux/netfilter_ipv6/ip6_tables.h>
18 #include <linux/netfilter_ipv6/ip6t_opts.h>
19
20 MODULE_LICENSE("GPL");
21 MODULE_DESCRIPTION("Xtables: IPv6 Hop-By-Hop and Destination Header match");
22 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
23 MODULE_ALIAS("ip6t_dst");
24
25 /*
26 * (Type & 0xC0) >> 6
27 * 0 -> ignorable
28 * 1 -> must drop the packet
29 * 2 -> send ICMP PARM PROB regardless and drop packet
30 * 3 -> Send ICMP if not a multicast address and drop packet
31 * (Type & 0x20) >> 5
32 * 0 -> invariant
33 * 1 -> can change the routing
34 * (Type & 0x1F) Type
35 * 0 -> Pad1 (only 1 byte!)
36 * 1 -> PadN LENGTH info (total length = length + 2)
37 * C0 | 2 -> JUMBO 4 x x x x ( xxxx > 64k )
38 * 5 -> RTALERT 2 x x
39 */
40
41 static struct xt_match hbh_mt6_reg[] __read_mostly;
42
43 static bool
hbh_mt6(const struct sk_buff * skb,struct xt_action_param * par)44 hbh_mt6(const struct sk_buff *skb, struct xt_action_param *par)
45 {
46 struct ipv6_opt_hdr _optsh;
47 const struct ipv6_opt_hdr *oh;
48 const struct ip6t_opts *optinfo = par->matchinfo;
49 unsigned int temp;
50 unsigned int ptr = 0;
51 unsigned int hdrlen = 0;
52 bool ret = false;
53 u8 _opttype;
54 u8 _optlen;
55 const u_int8_t *tp = NULL;
56 const u_int8_t *lp = NULL;
57 unsigned int optlen;
58 int err;
59
60 err = ipv6_find_hdr(skb, &ptr,
61 (par->match == &hbh_mt6_reg[0]) ?
62 NEXTHDR_HOP : NEXTHDR_DEST, NULL, NULL);
63 if (err < 0) {
64 if (err != -ENOENT)
65 par->hotdrop = true;
66 return false;
67 }
68
69 oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh);
70 if (oh == NULL) {
71 par->hotdrop = true;
72 return false;
73 }
74
75 hdrlen = ipv6_optlen(oh);
76 if (skb->len - ptr < hdrlen) {
77 /* Packet smaller than it's length field */
78 par->hotdrop = true;
79 return false;
80 }
81
82 ret = (!(optinfo->flags & IP6T_OPTS_LEN) ||
83 ((optinfo->hdrlen == hdrlen) ^
84 !!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
85
86 ptr += 2;
87 hdrlen -= 2;
88 if (!(optinfo->flags & IP6T_OPTS_OPTS)) {
89 return ret;
90 } else {
91 for (temp = 0; temp < optinfo->optsnr; temp++) {
92 /* type field exists ? */
93 if (hdrlen < 1)
94 break;
95 tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
96 &_opttype);
97 if (tp == NULL)
98 break;
99
100 /* Type check */
101 if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8)
102 return false;
103
104 /* Length check */
105 if (*tp) {
106 u16 spec_len;
107
108 /* length field exists ? */
109 if (hdrlen < 2)
110 break;
111 lp = skb_header_pointer(skb, ptr + 1,
112 sizeof(_optlen),
113 &_optlen);
114 if (lp == NULL)
115 break;
116 spec_len = optinfo->opts[temp] & 0x00FF;
117
118 if (spec_len != 0x00FF && spec_len != *lp)
119 return false;
120
121 optlen = *lp + 2;
122 } else {
123 optlen = 1;
124 }
125
126 if ((ptr > skb->len - optlen || hdrlen < optlen) &&
127 temp < optinfo->optsnr - 1)
128 break;
129
130 ptr += optlen;
131 hdrlen -= optlen;
132 }
133 if (temp == optinfo->optsnr)
134 return ret;
135 else
136 return false;
137 }
138
139 return false;
140 }
141
hbh_mt6_check(const struct xt_mtchk_param * par)142 static int hbh_mt6_check(const struct xt_mtchk_param *par)
143 {
144 const struct ip6t_opts *optsinfo = par->matchinfo;
145
146 if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
147 pr_info_ratelimited("unknown flags %X\n", optsinfo->invflags);
148 return -EINVAL;
149 }
150 if (optsinfo->optsnr > IP6T_OPTS_OPTSNR) {
151 pr_info_ratelimited("too many supported opts specified\n");
152 return -EINVAL;
153 }
154
155 if (optsinfo->flags & IP6T_OPTS_NSTRICT) {
156 pr_info_ratelimited("Not strict - not implemented\n");
157 return -EINVAL;
158 }
159
160 return 0;
161 }
162
163 static struct xt_match hbh_mt6_reg[] __read_mostly = {
164 {
165 /* Note, hbh_mt6 relies on the order of hbh_mt6_reg */
166 .name = "hbh",
167 .family = NFPROTO_IPV6,
168 .match = hbh_mt6,
169 .matchsize = sizeof(struct ip6t_opts),
170 .checkentry = hbh_mt6_check,
171 .me = THIS_MODULE,
172 },
173 {
174 .name = "dst",
175 .family = NFPROTO_IPV6,
176 .match = hbh_mt6,
177 .matchsize = sizeof(struct ip6t_opts),
178 .checkentry = hbh_mt6_check,
179 .me = THIS_MODULE,
180 },
181 };
182
hbh_mt6_init(void)183 static int __init hbh_mt6_init(void)
184 {
185 return xt_register_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
186 }
187
hbh_mt6_exit(void)188 static void __exit hbh_mt6_exit(void)
189 {
190 xt_unregister_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
191 }
192
193 module_init(hbh_mt6_init);
194 module_exit(hbh_mt6_exit);
195