xref: /openbmc/linux/net/bridge/netfilter/ebt_among.c (revision 09c434b8)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  ebt_among
4  *
5  *	Authors:
6  *	Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
7  *
8  *  August, 2003
9  *
10  */
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 #include <linux/ip.h>
13 #include <linux/if_arp.h>
14 #include <linux/module.h>
15 #include <linux/netfilter/x_tables.h>
16 #include <linux/netfilter_bridge/ebtables.h>
17 #include <linux/netfilter_bridge/ebt_among.h>
18 
ebt_mac_wormhash_contains(const struct ebt_mac_wormhash * wh,const char * mac,__be32 ip)19 static bool ebt_mac_wormhash_contains(const struct ebt_mac_wormhash *wh,
20 				      const char *mac, __be32 ip)
21 {
22 	/* You may be puzzled as to how this code works.
23 	 * Some tricks were used, refer to
24 	 * 	include/linux/netfilter_bridge/ebt_among.h
25 	 * as there you can find a solution of this mystery.
26 	 */
27 	const struct ebt_mac_wormhash_tuple *p;
28 	int start, limit, i;
29 	uint32_t cmp[2] = { 0, 0 };
30 	int key = ((const unsigned char *)mac)[5];
31 
32 	ether_addr_copy(((char *) cmp) + 2, mac);
33 	start = wh->table[key];
34 	limit = wh->table[key + 1];
35 	if (ip) {
36 		for (i = start; i < limit; i++) {
37 			p = &wh->pool[i];
38 			if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
39 				if (p->ip == 0 || p->ip == ip)
40 					return true;
41 		}
42 	} else {
43 		for (i = start; i < limit; i++) {
44 			p = &wh->pool[i];
45 			if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
46 				if (p->ip == 0)
47 					return true;
48 		}
49 	}
50 	return false;
51 }
52 
ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash * wh)53 static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
54 					    *wh)
55 {
56 	int i;
57 
58 	for (i = 0; i < 256; i++) {
59 		if (wh->table[i] > wh->table[i + 1])
60 			return -0x100 - i;
61 		if (wh->table[i] < 0)
62 			return -0x200 - i;
63 		if (wh->table[i] > wh->poolsize)
64 			return -0x300 - i;
65 	}
66 	if (wh->table[256] > wh->poolsize)
67 		return -0xc00;
68 	return 0;
69 }
70 
get_ip_dst(const struct sk_buff * skb,__be32 * addr)71 static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
72 {
73 	if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
74 		const struct iphdr *ih;
75 		struct iphdr _iph;
76 
77 		ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
78 		if (ih == NULL)
79 			return -1;
80 		*addr = ih->daddr;
81 	} else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
82 		const struct arphdr *ah;
83 		struct arphdr _arph;
84 		const __be32 *bp;
85 		__be32 buf;
86 
87 		ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
88 		if (ah == NULL ||
89 		    ah->ar_pln != sizeof(__be32) ||
90 		    ah->ar_hln != ETH_ALEN)
91 			return -1;
92 		bp = skb_header_pointer(skb, sizeof(struct arphdr) +
93 					2 * ETH_ALEN + sizeof(__be32),
94 					sizeof(__be32), &buf);
95 		if (bp == NULL)
96 			return -1;
97 		*addr = *bp;
98 	}
99 	return 0;
100 }
101 
get_ip_src(const struct sk_buff * skb,__be32 * addr)102 static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
103 {
104 	if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
105 		const struct iphdr *ih;
106 		struct iphdr _iph;
107 
108 		ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
109 		if (ih == NULL)
110 			return -1;
111 		*addr = ih->saddr;
112 	} else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
113 		const struct arphdr *ah;
114 		struct arphdr _arph;
115 		const __be32 *bp;
116 		__be32 buf;
117 
118 		ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
119 		if (ah == NULL ||
120 		    ah->ar_pln != sizeof(__be32) ||
121 		    ah->ar_hln != ETH_ALEN)
122 			return -1;
123 		bp = skb_header_pointer(skb, sizeof(struct arphdr) +
124 					ETH_ALEN, sizeof(__be32), &buf);
125 		if (bp == NULL)
126 			return -1;
127 		*addr = *bp;
128 	}
129 	return 0;
130 }
131 
132 static bool
ebt_among_mt(const struct sk_buff * skb,struct xt_action_param * par)133 ebt_among_mt(const struct sk_buff *skb, struct xt_action_param *par)
134 {
135 	const struct ebt_among_info *info = par->matchinfo;
136 	const char *dmac, *smac;
137 	const struct ebt_mac_wormhash *wh_dst, *wh_src;
138 	__be32 dip = 0, sip = 0;
139 
140 	wh_dst = ebt_among_wh_dst(info);
141 	wh_src = ebt_among_wh_src(info);
142 
143 	if (wh_src) {
144 		smac = eth_hdr(skb)->h_source;
145 		if (get_ip_src(skb, &sip))
146 			return false;
147 		if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
148 			/* we match only if it contains */
149 			if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
150 				return false;
151 		} else {
152 			/* we match only if it DOES NOT contain */
153 			if (ebt_mac_wormhash_contains(wh_src, smac, sip))
154 				return false;
155 		}
156 	}
157 
158 	if (wh_dst) {
159 		dmac = eth_hdr(skb)->h_dest;
160 		if (get_ip_dst(skb, &dip))
161 			return false;
162 		if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
163 			/* we match only if it contains */
164 			if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
165 				return false;
166 		} else {
167 			/* we match only if it DOES NOT contain */
168 			if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
169 				return false;
170 		}
171 	}
172 
173 	return true;
174 }
175 
poolsize_invalid(const struct ebt_mac_wormhash * w)176 static bool poolsize_invalid(const struct ebt_mac_wormhash *w)
177 {
178 	return w && w->poolsize >= (INT_MAX / sizeof(struct ebt_mac_wormhash_tuple));
179 }
180 
wormhash_offset_invalid(int off,unsigned int len)181 static bool wormhash_offset_invalid(int off, unsigned int len)
182 {
183 	if (off == 0) /* not present */
184 		return false;
185 
186 	if (off < (int)sizeof(struct ebt_among_info) ||
187 	    off % __alignof__(struct ebt_mac_wormhash))
188 		return true;
189 
190 	off += sizeof(struct ebt_mac_wormhash);
191 
192 	return off > len;
193 }
194 
wormhash_sizes_valid(const struct ebt_mac_wormhash * wh,int a,int b)195 static bool wormhash_sizes_valid(const struct ebt_mac_wormhash *wh, int a, int b)
196 {
197 	if (a == 0)
198 		a = sizeof(struct ebt_among_info);
199 
200 	return ebt_mac_wormhash_size(wh) + a == b;
201 }
202 
ebt_among_mt_check(const struct xt_mtchk_param * par)203 static int ebt_among_mt_check(const struct xt_mtchk_param *par)
204 {
205 	const struct ebt_among_info *info = par->matchinfo;
206 	const struct ebt_entry_match *em =
207 		container_of(par->matchinfo, const struct ebt_entry_match, data);
208 	unsigned int expected_length = sizeof(struct ebt_among_info);
209 	const struct ebt_mac_wormhash *wh_dst, *wh_src;
210 	int err;
211 
212 	if (expected_length > em->match_size)
213 		return -EINVAL;
214 
215 	if (wormhash_offset_invalid(info->wh_dst_ofs, em->match_size) ||
216 	    wormhash_offset_invalid(info->wh_src_ofs, em->match_size))
217 		return -EINVAL;
218 
219 	wh_dst = ebt_among_wh_dst(info);
220 	if (poolsize_invalid(wh_dst))
221 		return -EINVAL;
222 
223 	expected_length += ebt_mac_wormhash_size(wh_dst);
224 	if (expected_length > em->match_size)
225 		return -EINVAL;
226 
227 	wh_src = ebt_among_wh_src(info);
228 	if (poolsize_invalid(wh_src))
229 		return -EINVAL;
230 
231 	if (info->wh_src_ofs < info->wh_dst_ofs) {
232 		if (!wormhash_sizes_valid(wh_src, info->wh_src_ofs, info->wh_dst_ofs))
233 			return -EINVAL;
234 	} else {
235 		if (!wormhash_sizes_valid(wh_dst, info->wh_dst_ofs, info->wh_src_ofs))
236 			return -EINVAL;
237 	}
238 
239 	expected_length += ebt_mac_wormhash_size(wh_src);
240 
241 	if (em->match_size != EBT_ALIGN(expected_length)) {
242 		pr_err_ratelimited("wrong size: %d against expected %d, rounded to %zd\n",
243 				   em->match_size, expected_length,
244 				   EBT_ALIGN(expected_length));
245 		return -EINVAL;
246 	}
247 	if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
248 		pr_err_ratelimited("dst integrity fail: %x\n", -err);
249 		return -EINVAL;
250 	}
251 	if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
252 		pr_err_ratelimited("src integrity fail: %x\n", -err);
253 		return -EINVAL;
254 	}
255 	return 0;
256 }
257 
258 static struct xt_match ebt_among_mt_reg __read_mostly = {
259 	.name		= "among",
260 	.revision	= 0,
261 	.family		= NFPROTO_BRIDGE,
262 	.match		= ebt_among_mt,
263 	.checkentry	= ebt_among_mt_check,
264 	.matchsize	= -1, /* special case */
265 	.me		= THIS_MODULE,
266 };
267 
ebt_among_init(void)268 static int __init ebt_among_init(void)
269 {
270 	return xt_register_match(&ebt_among_mt_reg);
271 }
272 
ebt_among_fini(void)273 static void __exit ebt_among_fini(void)
274 {
275 	xt_unregister_match(&ebt_among_mt_reg);
276 }
277 
278 module_init(ebt_among_init);
279 module_exit(ebt_among_fini);
280 MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
281 MODULE_LICENSE("GPL");
282