1 /* Kernel module to match ROUTING 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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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_rt.h>
22 
23 MODULE_LICENSE("GPL");
24 MODULE_DESCRIPTION("Xtables: IPv6 Routing Header match");
25 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
26 
27 /* Returns 1 if the id is matched by the range, 0 otherwise */
28 static inline bool
segsleft_match(u_int32_t min,u_int32_t max,u_int32_t id,bool invert)29 segsleft_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
30 {
31 	bool r;
32 	pr_debug("segsleft_match:%c 0x%x <= 0x%x <= 0x%x\n",
33 		 invert ? '!' : ' ', min, id, max);
34 	r = (id >= min && id <= max) ^ invert;
35 	pr_debug(" result %s\n", r ? "PASS" : "FAILED");
36 	return r;
37 }
38 
rt_mt6(const struct sk_buff * skb,struct xt_action_param * par)39 static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
40 {
41 	struct ipv6_rt_hdr _route;
42 	const struct ipv6_rt_hdr *rh;
43 	const struct ip6t_rt *rtinfo = par->matchinfo;
44 	unsigned int temp;
45 	unsigned int ptr = 0;
46 	unsigned int hdrlen = 0;
47 	bool ret = false;
48 	struct in6_addr _addr;
49 	const struct in6_addr *ap;
50 	int err;
51 
52 	err = ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING, NULL, NULL);
53 	if (err < 0) {
54 		if (err != -ENOENT)
55 			par->hotdrop = true;
56 		return false;
57 	}
58 
59 	rh = skb_header_pointer(skb, ptr, sizeof(_route), &_route);
60 	if (rh == NULL) {
61 		par->hotdrop = true;
62 		return false;
63 	}
64 
65 	hdrlen = ipv6_optlen(rh);
66 	if (skb->len - ptr < hdrlen) {
67 		/* Pcket smaller than its length field */
68 		return false;
69 	}
70 
71 	pr_debug("IPv6 RT LEN %u %u ", hdrlen, rh->hdrlen);
72 	pr_debug("TYPE %04X ", rh->type);
73 	pr_debug("SGS_LEFT %u %02X\n", rh->segments_left, rh->segments_left);
74 
75 	pr_debug("IPv6 RT segsleft %02X ",
76 		 segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
77 				rh->segments_left,
78 				!!(rtinfo->invflags & IP6T_RT_INV_SGS)));
79 	pr_debug("type %02X %02X %02X ",
80 		 rtinfo->rt_type, rh->type,
81 		 (!(rtinfo->flags & IP6T_RT_TYP) ||
82 		  ((rtinfo->rt_type == rh->type) ^
83 		   !!(rtinfo->invflags & IP6T_RT_INV_TYP))));
84 	pr_debug("len %02X %04X %02X ",
85 		 rtinfo->hdrlen, hdrlen,
86 		 !(rtinfo->flags & IP6T_RT_LEN) ||
87 		  ((rtinfo->hdrlen == hdrlen) ^
88 		   !!(rtinfo->invflags & IP6T_RT_INV_LEN)));
89 	pr_debug("res %02X %02X %02X ",
90 		 rtinfo->flags & IP6T_RT_RES,
91 		 ((const struct rt0_hdr *)rh)->reserved,
92 		 !((rtinfo->flags & IP6T_RT_RES) &&
93 		   (((const struct rt0_hdr *)rh)->reserved)));
94 
95 	ret = (rh != NULL) &&
96 	      (segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
97 			      rh->segments_left,
98 			      !!(rtinfo->invflags & IP6T_RT_INV_SGS))) &&
99 	      (!(rtinfo->flags & IP6T_RT_LEN) ||
100 	       ((rtinfo->hdrlen == hdrlen) ^
101 		!!(rtinfo->invflags & IP6T_RT_INV_LEN))) &&
102 	      (!(rtinfo->flags & IP6T_RT_TYP) ||
103 	       ((rtinfo->rt_type == rh->type) ^
104 		!!(rtinfo->invflags & IP6T_RT_INV_TYP)));
105 
106 	if (ret && (rtinfo->flags & IP6T_RT_RES)) {
107 		const u_int32_t *rp;
108 		u_int32_t _reserved;
109 		rp = skb_header_pointer(skb,
110 					ptr + offsetof(struct rt0_hdr,
111 						       reserved),
112 					sizeof(_reserved),
113 					&_reserved);
114 
115 		ret = (*rp == 0);
116 	}
117 
118 	pr_debug("#%d ", rtinfo->addrnr);
119 	if (!(rtinfo->flags & IP6T_RT_FST)) {
120 		return ret;
121 	} else if (rtinfo->flags & IP6T_RT_FST_NSTRICT) {
122 		pr_debug("Not strict ");
123 		if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
124 			pr_debug("There isn't enough space\n");
125 			return false;
126 		} else {
127 			unsigned int i = 0;
128 
129 			pr_debug("#%d ", rtinfo->addrnr);
130 			for (temp = 0;
131 			     temp < (unsigned int)((hdrlen - 8) / 16);
132 			     temp++) {
133 				ap = skb_header_pointer(skb,
134 							ptr
135 							+ sizeof(struct rt0_hdr)
136 							+ temp * sizeof(_addr),
137 							sizeof(_addr),
138 							&_addr);
139 
140 				BUG_ON(ap == NULL);
141 
142 				if (ipv6_addr_equal(ap, &rtinfo->addrs[i])) {
143 					pr_debug("i=%d temp=%d;\n", i, temp);
144 					i++;
145 				}
146 				if (i == rtinfo->addrnr)
147 					break;
148 			}
149 			pr_debug("i=%d #%d\n", i, rtinfo->addrnr);
150 			if (i == rtinfo->addrnr)
151 				return ret;
152 			else
153 				return false;
154 		}
155 	} else {
156 		pr_debug("Strict ");
157 		if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
158 			pr_debug("There isn't enough space\n");
159 			return false;
160 		} else {
161 			pr_debug("#%d ", rtinfo->addrnr);
162 			for (temp = 0; temp < rtinfo->addrnr; temp++) {
163 				ap = skb_header_pointer(skb,
164 							ptr
165 							+ sizeof(struct rt0_hdr)
166 							+ temp * sizeof(_addr),
167 							sizeof(_addr),
168 							&_addr);
169 				BUG_ON(ap == NULL);
170 
171 				if (!ipv6_addr_equal(ap, &rtinfo->addrs[temp]))
172 					break;
173 			}
174 			pr_debug("temp=%d #%d\n", temp, rtinfo->addrnr);
175 			if (temp == rtinfo->addrnr &&
176 			    temp == (unsigned int)((hdrlen - 8) / 16))
177 				return ret;
178 			else
179 				return false;
180 		}
181 	}
182 
183 	return false;
184 }
185 
rt_mt6_check(const struct xt_mtchk_param * par)186 static int rt_mt6_check(const struct xt_mtchk_param *par)
187 {
188 	const struct ip6t_rt *rtinfo = par->matchinfo;
189 
190 	if (rtinfo->invflags & ~IP6T_RT_INV_MASK) {
191 		pr_debug("unknown flags %X\n", rtinfo->invflags);
192 		return -EINVAL;
193 	}
194 	if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) &&
195 	    (!(rtinfo->flags & IP6T_RT_TYP) ||
196 	     (rtinfo->rt_type != 0) ||
197 	     (rtinfo->invflags & IP6T_RT_INV_TYP))) {
198 		pr_debug("`--rt-type 0' required before `--rt-0-*'");
199 		return -EINVAL;
200 	}
201 
202 	return 0;
203 }
204 
205 static struct xt_match rt_mt6_reg __read_mostly = {
206 	.name		= "rt",
207 	.family		= NFPROTO_IPV6,
208 	.match		= rt_mt6,
209 	.matchsize	= sizeof(struct ip6t_rt),
210 	.checkentry	= rt_mt6_check,
211 	.me		= THIS_MODULE,
212 };
213 
rt_mt6_init(void)214 static int __init rt_mt6_init(void)
215 {
216 	return xt_register_match(&rt_mt6_reg);
217 }
218 
rt_mt6_exit(void)219 static void __exit rt_mt6_exit(void)
220 {
221 	xt_unregister_match(&rt_mt6_reg);
222 }
223 
224 module_init(rt_mt6_init);
225 module_exit(rt_mt6_exit);
226