PageRenderTime 33ms CodeModel.GetById 15ms app.highlight 14ms RepoModel.GetById 1ms app.codeStats 0ms

/net/bridge/netfilter/ebt_among.c

http://github.com/mirrors/linux
C | 281 lines | 227 code | 35 blank | 19 comment | 83 complexity | 535ae2fed1478b2d24c9cb1d1e1f54d3 MD5 | raw file
  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
 19static 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
 53static 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
 71static 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
102static 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
132static bool
133ebt_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
176static 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
181static 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
195static 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
203static 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
258static 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
268static int __init ebt_among_init(void)
269{
270	return xt_register_match(&ebt_among_mt_reg);
271}
272
273static void __exit ebt_among_fini(void)
274{
275	xt_unregister_match(&ebt_among_mt_reg);
276}
277
278module_init(ebt_among_init);
279module_exit(ebt_among_fini);
280MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
281MODULE_LICENSE("GPL");