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