1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Kernel module to match ROUTING 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_rt.h>
19 
20 MODULE_LICENSE("GPL");
21 MODULE_DESCRIPTION("Xtables: IPv6 Routing Header match");
22 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
23 
24 /* Returns 1 if the id is matched by the range, 0 otherwise */
25 static inline bool
segsleft_match(u_int32_t min,u_int32_t max,u_int32_t id,bool invert)26 segsleft_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
27 {
28 	bool r;
29 	pr_debug("segsleft_match:%c 0x%x <= 0x%x <= 0x%x\n",
30 		 invert ? '!' : ' ', min, id, max);
31 	r = (id >= min && id <= max) ^ invert;
32 	pr_debug(" result %s\n", r ? "PASS" : "FAILED");
33 	return r;
34 }
35 
rt_mt6(const struct sk_buff * skb,struct xt_action_param * par)36 static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
37 {
38 	struct ipv6_rt_hdr _route;
39 	const struct ipv6_rt_hdr *rh;
40 	const struct ip6t_rt *rtinfo = par->matchinfo;
41 	unsigned int temp;
42 	unsigned int ptr = 0;
43 	unsigned int hdrlen = 0;
44 	bool ret = false;
45 	struct in6_addr _addr;
46 	const struct in6_addr *ap;
47 	int err;
48 
49 	err = ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING, NULL, NULL);
50 	if (err < 0) {
51 		if (err != -ENOENT)
52 			par->hotdrop = true;
53 		return false;
54 	}
55 
56 	rh = skb_header_pointer(skb, ptr, sizeof(_route), &_route);
57 	if (rh == NULL) {
58 		par->hotdrop = true;
59 		return false;
60 	}
61 
62 	hdrlen = ipv6_optlen(rh);
63 	if (skb->len - ptr < hdrlen) {
64 		/* Pcket smaller than its length field */
65 		return false;
66 	}
67 
68 	pr_debug("IPv6 RT LEN %u %u ", hdrlen, rh->hdrlen);
69 	pr_debug("TYPE %04X ", rh->type);
70 	pr_debug("SGS_LEFT %u %02X\n", rh->segments_left, rh->segments_left);
71 
72 	pr_debug("IPv6 RT segsleft %02X ",
73 		 segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
74 				rh->segments_left,
75 				!!(rtinfo->invflags & IP6T_RT_INV_SGS)));
76 	pr_debug("type %02X %02X %02X ",
77 		 rtinfo->rt_type, rh->type,
78 		 (!(rtinfo->flags & IP6T_RT_TYP) ||
79 		  ((rtinfo->rt_type == rh->type) ^
80 		   !!(rtinfo->invflags & IP6T_RT_INV_TYP))));
81 	pr_debug("len %02X %04X %02X ",
82 		 rtinfo->hdrlen, hdrlen,
83 		 !(rtinfo->flags & IP6T_RT_LEN) ||
84 		  ((rtinfo->hdrlen == hdrlen) ^
85 		   !!(rtinfo->invflags & IP6T_RT_INV_LEN)));
86 	pr_debug("res %02X %02X %02X ",
87 		 rtinfo->flags & IP6T_RT_RES,
88 		 ((const struct rt0_hdr *)rh)->reserved,
89 		 !((rtinfo->flags & IP6T_RT_RES) &&
90 		   (((const struct rt0_hdr *)rh)->reserved)));
91 
92 	ret = (segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
93 			      rh->segments_left,
94 			      !!(rtinfo->invflags & IP6T_RT_INV_SGS))) &&
95 	      (!(rtinfo->flags & IP6T_RT_LEN) ||
96 	       ((rtinfo->hdrlen == hdrlen) ^
97 		!!(rtinfo->invflags & IP6T_RT_INV_LEN))) &&
98 	      (!(rtinfo->flags & IP6T_RT_TYP) ||
99 	       ((rtinfo->rt_type == rh->type) ^
100 		!!(rtinfo->invflags & IP6T_RT_INV_TYP)));
101 
102 	if (ret && (rtinfo->flags & IP6T_RT_RES)) {
103 		const u_int32_t *rp;
104 		u_int32_t _reserved;
105 		rp = skb_header_pointer(skb,
106 					ptr + offsetof(struct rt0_hdr,
107 						       reserved),
108 					sizeof(_reserved),
109 					&_reserved);
110 
111 		ret = (*rp == 0);
112 	}
113 
114 	pr_debug("#%d ", rtinfo->addrnr);
115 	if (!(rtinfo->flags & IP6T_RT_FST)) {
116 		return ret;
117 	} else if (rtinfo->flags & IP6T_RT_FST_NSTRICT) {
118 		pr_debug("Not strict ");
119 		if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
120 			pr_debug("There isn't enough space\n");
121 			return false;
122 		} else {
123 			unsigned int i = 0;
124 
125 			pr_debug("#%d ", rtinfo->addrnr);
126 			for (temp = 0;
127 			     temp < (unsigned int)((hdrlen - 8) / 16);
128 			     temp++) {
129 				ap = skb_header_pointer(skb,
130 							ptr
131 							+ sizeof(struct rt0_hdr)
132 							+ temp * sizeof(_addr),
133 							sizeof(_addr),
134 							&_addr);
135 
136 				if (ap == NULL) {
137 					par->hotdrop = true;
138 					return false;
139 				}
140 
141 				if (ipv6_addr_equal(ap, &rtinfo->addrs[i])) {
142 					pr_debug("i=%d temp=%d;\n", i, temp);
143 					i++;
144 				}
145 				if (i == rtinfo->addrnr)
146 					break;
147 			}
148 			pr_debug("i=%d #%d\n", i, rtinfo->addrnr);
149 			if (i == rtinfo->addrnr)
150 				return ret;
151 			else
152 				return false;
153 		}
154 	} else {
155 		pr_debug("Strict ");
156 		if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
157 			pr_debug("There isn't enough space\n");
158 			return false;
159 		} else {
160 			pr_debug("#%d ", rtinfo->addrnr);
161 			for (temp = 0; temp < rtinfo->addrnr; temp++) {
162 				ap = skb_header_pointer(skb,
163 							ptr
164 							+ sizeof(struct rt0_hdr)
165 							+ temp * sizeof(_addr),
166 							sizeof(_addr),
167 							&_addr);
168 				if (ap == NULL) {
169 					par->hotdrop = true;
170 					return false;
171 				}
172 
173 				if (!ipv6_addr_equal(ap, &rtinfo->addrs[temp]))
174 					break;
175 			}
176 			pr_debug("temp=%d #%d\n", temp, rtinfo->addrnr);
177 			if (temp == rtinfo->addrnr &&
178 			    temp == (unsigned int)((hdrlen - 8) / 16))
179 				return ret;
180 			else
181 				return false;
182 		}
183 	}
184 
185 	return false;
186 }
187 
rt_mt6_check(const struct xt_mtchk_param * par)188 static int rt_mt6_check(const struct xt_mtchk_param *par)
189 {
190 	const struct ip6t_rt *rtinfo = par->matchinfo;
191 
192 	if (rtinfo->invflags & ~IP6T_RT_INV_MASK) {
193 		pr_debug("unknown flags %X\n", rtinfo->invflags);
194 		return -EINVAL;
195 	}
196 	if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) &&
197 	    (!(rtinfo->flags & IP6T_RT_TYP) ||
198 	     (rtinfo->rt_type != 0) ||
199 	     (rtinfo->invflags & IP6T_RT_INV_TYP))) {
200 		pr_debug("`--rt-type 0' required before `--rt-0-*'");
201 		return -EINVAL;
202 	}
203 
204 	return 0;
205 }
206 
207 static struct xt_match rt_mt6_reg __read_mostly = {
208 	.name		= "rt",
209 	.family		= NFPROTO_IPV6,
210 	.match		= rt_mt6,
211 	.matchsize	= sizeof(struct ip6t_rt),
212 	.checkentry	= rt_mt6_check,
213 	.me		= THIS_MODULE,
214 };
215 
rt_mt6_init(void)216 static int __init rt_mt6_init(void)
217 {
218 	return xt_register_match(&rt_mt6_reg);
219 }
220 
rt_mt6_exit(void)221 static void __exit rt_mt6_exit(void)
222 {
223 	xt_unregister_match(&rt_mt6_reg);
224 }
225 
226 module_init(rt_mt6_init);
227 module_exit(rt_mt6_exit);
228