xref: /openbmc/linux/net/ipv6/netfilter/ip6t_hbh.c (revision 42f36eba)
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 = (!(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 
hbh_mt6_check(const struct xt_mtchk_param * par)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 
hbh_mt6_init(void)200 static int __init hbh_mt6_init(void)
201 {
202 	return xt_register_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
203 }
204 
hbh_mt6_exit(void)205 static void __exit hbh_mt6_exit(void)
206 {
207 	xt_unregister_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg));
208 }
209 
210 module_init(hbh_mt6_init);
211 module_exit(hbh_mt6_exit);
212