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 |
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, offset: &ptr, |
61 | target: (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, offset: ptr, len: sizeof(_optsh), buffer: &_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 = (!(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, offset: ptr, len: sizeof(_opttype), |
105 | buffer: &_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, offset: ptr + 1, |
125 | len: sizeof(_optlen), |
126 | buffer: &_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 int 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("unknown flags %X\n" , optsinfo->invflags); |
169 | return -EINVAL; |
170 | } |
171 | |
172 | if (optsinfo->flags & IP6T_OPTS_NSTRICT) { |
173 | pr_debug("Not strict - not implemented" ); |
174 | return -EINVAL; |
175 | } |
176 | |
177 | return 0; |
178 | } |
179 | |
180 | static struct xt_match hbh_mt6_reg[] __read_mostly = { |
181 | { |
182 | /* Note, hbh_mt6 relies on the order of hbh_mt6_reg */ |
183 | .name = "hbh" , |
184 | .family = NFPROTO_IPV6, |
185 | .match = hbh_mt6, |
186 | .matchsize = sizeof(struct ip6t_opts), |
187 | .checkentry = hbh_mt6_check, |
188 | .me = THIS_MODULE, |
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 | }, |
198 | }; |
199 | |
200 | static int __init hbh_mt6_init(void) |
201 | { |
202 | return xt_register_matches(match: hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg)); |
203 | } |
204 | |
205 | static void __exit hbh_mt6_exit(void) |
206 | { |
207 | xt_unregister_matches(match: hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg)); |
208 | } |
209 | |
210 | module_init(hbh_mt6_init); |
211 | module_exit(hbh_mt6_exit); |
212 | |