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 return false;
79 }
80
81 pr_debug("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen);
82
83 pr_debug("len %02X %04X %02X ",
84 optinfo->hdrlen, hdrlen,
85 (!(optinfo->flags & IP6T_OPTS_LEN) ||
86 ((optinfo->hdrlen == hdrlen) ^
87 !!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
88
89 ret = (oh != NULL) &&
90 (!(optinfo->flags & IP6T_OPTS_LEN) ||
91 ((optinfo->hdrlen == hdrlen) ^
92 !!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
93
94 ptr += 2;
95 hdrlen -= 2;
96 if (!(optinfo->flags & IP6T_OPTS_OPTS)) {
97 return ret;
98 } else {
99 pr_debug("Strict ");
100 pr_debug("#%d ", optinfo->optsnr);
101 for (temp = 0; temp < optinfo->optsnr; temp++) {
102 /* type field exists ? */
103 if (hdrlen < 1)
104 break;
105 tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
106 &_opttype);
107 if (tp == NULL)
108 break;
109
110 /* Type check */
111 if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8) {
112 pr_debug("Tbad %02X %02X\n", *tp,
113 (optinfo->opts[temp] & 0xFF00) >> 8);
114 return false;
115 } else {
116 pr_debug("Tok ");
117 }
118 /* Length check */
119 if (*tp) {
120 u16 spec_len;
121
122 /* length field exists ? */
123 if (hdrlen < 2)
124 break;
125 lp = skb_header_pointer(skb, ptr + 1,
126 sizeof(_optlen),
127 &_optlen);
128 if (lp == NULL)
129 break;
130 spec_len = optinfo->opts[temp] & 0x00FF;
131
132 if (spec_len != 0x00FF && spec_len != *lp) {
133 pr_debug("Lbad %02X %04X\n", *lp,
134 spec_len);
135 return false;
136 }
137 pr_debug("Lok ");
138 optlen = *lp + 2;
139 } else {
140 pr_debug("Pad1\n");
141 optlen = 1;
142 }
143
144 /* Step to the next */
145 pr_debug("len%04X\n", optlen);
146
147 if ((ptr > skb->len - optlen || hdrlen < optlen) &&
148 temp < optinfo->optsnr - 1) {
149 pr_debug("new pointer is too large!\n");
150 break;
151 }
152 ptr += optlen;
153 hdrlen -= optlen;
154 }
155 if (temp == optinfo->optsnr)
156 return ret;
157 else
158 return false;
159 }
160
161 return false;
162 }
163
hbh_mt6_check(const struct xt_mtchk_param * par)164 static int hbh_mt6_check(const struct xt_mtchk_param *par)
165 {
166 const struct ip6t_opts *optsinfo = par->matchinfo;
167
168 if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
169 pr_debug("unknown flags %X\n", optsinfo->invflags);
170 return -EINVAL;
171 }
172
173 if (optsinfo->flags & IP6T_OPTS_NSTRICT) {
174 pr_debug("Not strict - not implemented");
175 return -EINVAL;
176 }
177
178 return 0;
179 }
180
181 static struct xt_match hbh_mt6_reg[] __read_mostly = {
182 {
183 /* Note, hbh_mt6 relies on the order of hbh_mt6_reg */
184 .name = "hbh",
185 .family = NFPROTO_IPV6,
186 .match = hbh_mt6,
187 .matchsize = sizeof(struct ip6t_opts),
188 .checkentry = hbh_mt6_check,
189 .me = THIS_MODULE,
190 },
191 {
192 .name = "dst",
193 .family = NFPROTO_IPV6,
194 .match = hbh_mt6,
195 .matchsize = sizeof(struct ip6t_opts),
196 .checkentry = hbh_mt6_check,
197 .me = THIS_MODULE,
198 },
199 };
200
hbh_mt6_init(void)201 static int __init hbh_mt6_init(void)
202 {
203 return xt_register_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
204 }
205
hbh_mt6_exit(void)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