1 /*
2 * Copyright (c) 2014 Pablo Neira Ayuso <pablo@netfilter.org>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9 #include <linux/kernel.h>
10 #include <linux/init.h>
11 #include <linux/module.h>
12 #include <linux/netlink.h>
13 #include <linux/netfilter.h>
14 #include <linux/netfilter/nf_tables.h>
15 #include <net/netfilter/nf_tables.h>
16 #include <net/netfilter/nft_reject.h>
17 #include <net/netfilter/ipv4/nf_reject.h>
18 #include <net/netfilter/ipv6/nf_reject.h>
19 #include <linux/ip.h>
20 #include <net/ip.h>
21 #include <net/ip6_checksum.h>
22 #include <linux/netfilter_bridge.h>
23 #include <linux/netfilter_ipv6.h>
24 #include "../br_private.h"
25
nft_reject_br_push_etherhdr(struct sk_buff * oldskb,struct sk_buff * nskb)26 static void nft_reject_br_push_etherhdr(struct sk_buff *oldskb,
27 struct sk_buff *nskb)
28 {
29 struct ethhdr *eth;
30
31 eth = (struct ethhdr *)skb_push(nskb, ETH_HLEN);
32 skb_reset_mac_header(nskb);
33 ether_addr_copy(eth->h_source, eth_hdr(oldskb)->h_dest);
34 ether_addr_copy(eth->h_dest, eth_hdr(oldskb)->h_source);
35 eth->h_proto = eth_hdr(oldskb)->h_proto;
36 skb_pull(nskb, ETH_HLEN);
37 }
38
nft_bridge_iphdr_validate(struct sk_buff * skb)39 static int nft_bridge_iphdr_validate(struct sk_buff *skb)
40 {
41 struct iphdr *iph;
42 u32 len;
43
44 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
45 return 0;
46
47 iph = ip_hdr(skb);
48 if (iph->ihl < 5 || iph->version != 4)
49 return 0;
50
51 len = ntohs(iph->tot_len);
52 if (skb->len < len)
53 return 0;
54 else if (len < (iph->ihl*4))
55 return 0;
56
57 if (!pskb_may_pull(skb, iph->ihl*4))
58 return 0;
59
60 return 1;
61 }
62
63 /* We cannot use oldskb->dev, it can be either bridge device (NF_BRIDGE INPUT)
64 * or the bridge port (NF_BRIDGE PREROUTING).
65 */
nft_reject_br_send_v4_tcp_reset(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook)66 static void nft_reject_br_send_v4_tcp_reset(struct net *net,
67 struct sk_buff *oldskb,
68 const struct net_device *dev,
69 int hook)
70 {
71 struct sk_buff *nskb;
72 struct iphdr *niph;
73 const struct tcphdr *oth;
74 struct tcphdr _oth;
75
76 if (!nft_bridge_iphdr_validate(oldskb))
77 return;
78
79 oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
80 if (!oth)
81 return;
82
83 nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
84 LL_MAX_HEADER, GFP_ATOMIC);
85 if (!nskb)
86 return;
87
88 skb_reserve(nskb, LL_MAX_HEADER);
89 niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
90 net->ipv4.sysctl_ip_default_ttl);
91 nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
92 niph->ttl = net->ipv4.sysctl_ip_default_ttl;
93 niph->tot_len = htons(nskb->len);
94 ip_send_check(niph);
95
96 nft_reject_br_push_etherhdr(oldskb, nskb);
97
98 br_forward(br_port_get_rcu(dev), nskb, false, true);
99 }
100
nft_reject_br_send_v4_unreach(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook,u8 code)101 static void nft_reject_br_send_v4_unreach(struct net *net,
102 struct sk_buff *oldskb,
103 const struct net_device *dev,
104 int hook, u8 code)
105 {
106 struct sk_buff *nskb;
107 struct iphdr *niph;
108 struct icmphdr *icmph;
109 unsigned int len;
110 void *payload;
111 __wsum csum;
112 u8 proto;
113
114 if (oldskb->csum_bad || !nft_bridge_iphdr_validate(oldskb))
115 return;
116
117 /* IP header checks: fragment. */
118 if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
119 return;
120
121 /* RFC says return as much as we can without exceeding 576 bytes. */
122 len = min_t(unsigned int, 536, oldskb->len);
123
124 if (!pskb_may_pull(oldskb, len))
125 return;
126
127 if (pskb_trim_rcsum(oldskb, ntohs(ip_hdr(oldskb)->tot_len)))
128 return;
129
130 if (ip_hdr(oldskb)->protocol == IPPROTO_TCP ||
131 ip_hdr(oldskb)->protocol == IPPROTO_UDP)
132 proto = ip_hdr(oldskb)->protocol;
133 else
134 proto = 0;
135
136 if (!skb_csum_unnecessary(oldskb) &&
137 nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), proto))
138 return;
139
140 nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmphdr) +
141 LL_MAX_HEADER + len, GFP_ATOMIC);
142 if (!nskb)
143 return;
144
145 skb_reserve(nskb, LL_MAX_HEADER);
146 niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_ICMP,
147 net->ipv4.sysctl_ip_default_ttl);
148
149 skb_reset_transport_header(nskb);
150 icmph = (struct icmphdr *)skb_put(nskb, sizeof(struct icmphdr));
151 memset(icmph, 0, sizeof(*icmph));
152 icmph->type = ICMP_DEST_UNREACH;
153 icmph->code = code;
154
155 payload = skb_put(nskb, len);
156 memcpy(payload, skb_network_header(oldskb), len);
157
158 csum = csum_partial((void *)icmph, len + sizeof(struct icmphdr), 0);
159 icmph->checksum = csum_fold(csum);
160
161 niph->tot_len = htons(nskb->len);
162 ip_send_check(niph);
163
164 nft_reject_br_push_etherhdr(oldskb, nskb);
165
166 br_forward(br_port_get_rcu(dev), nskb, false, true);
167 }
168
nft_bridge_ip6hdr_validate(struct sk_buff * skb)169 static int nft_bridge_ip6hdr_validate(struct sk_buff *skb)
170 {
171 struct ipv6hdr *hdr;
172 u32 pkt_len;
173
174 if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
175 return 0;
176
177 hdr = ipv6_hdr(skb);
178 if (hdr->version != 6)
179 return 0;
180
181 pkt_len = ntohs(hdr->payload_len);
182 if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
183 return 0;
184
185 return 1;
186 }
187
nft_reject_br_send_v6_tcp_reset(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook)188 static void nft_reject_br_send_v6_tcp_reset(struct net *net,
189 struct sk_buff *oldskb,
190 const struct net_device *dev,
191 int hook)
192 {
193 struct sk_buff *nskb;
194 const struct tcphdr *oth;
195 struct tcphdr _oth;
196 unsigned int otcplen;
197 struct ipv6hdr *nip6h;
198
199 if (!nft_bridge_ip6hdr_validate(oldskb))
200 return;
201
202 oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook);
203 if (!oth)
204 return;
205
206 nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) +
207 LL_MAX_HEADER, GFP_ATOMIC);
208 if (!nskb)
209 return;
210
211 skb_reserve(nskb, LL_MAX_HEADER);
212 nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
213 net->ipv6.devconf_all->hop_limit);
214 nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen);
215 nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
216
217 nft_reject_br_push_etherhdr(oldskb, nskb);
218
219 br_forward(br_port_get_rcu(dev), nskb, false, true);
220 }
221
reject6_br_csum_ok(struct sk_buff * skb,int hook)222 static bool reject6_br_csum_ok(struct sk_buff *skb, int hook)
223 {
224 const struct ipv6hdr *ip6h = ipv6_hdr(skb);
225 int thoff;
226 __be16 fo;
227 u8 proto = ip6h->nexthdr;
228
229 if (skb->csum_bad)
230 return false;
231
232 if (skb_csum_unnecessary(skb))
233 return true;
234
235 if (ip6h->payload_len &&
236 pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
237 return false;
238
239 thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
240 if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
241 return false;
242
243 return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
244 }
245
nft_reject_br_send_v6_unreach(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook,u8 code)246 static void nft_reject_br_send_v6_unreach(struct net *net,
247 struct sk_buff *oldskb,
248 const struct net_device *dev,
249 int hook, u8 code)
250 {
251 struct sk_buff *nskb;
252 struct ipv6hdr *nip6h;
253 struct icmp6hdr *icmp6h;
254 unsigned int len;
255 void *payload;
256
257 if (!nft_bridge_ip6hdr_validate(oldskb))
258 return;
259
260 /* Include "As much of invoking packet as possible without the ICMPv6
261 * packet exceeding the minimum IPv6 MTU" in the ICMP payload.
262 */
263 len = min_t(unsigned int, 1220, oldskb->len);
264
265 if (!pskb_may_pull(oldskb, len))
266 return;
267
268 if (!reject6_br_csum_ok(oldskb, hook))
269 return;
270
271 nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmp6hdr) +
272 LL_MAX_HEADER + len, GFP_ATOMIC);
273 if (!nskb)
274 return;
275
276 skb_reserve(nskb, LL_MAX_HEADER);
277 nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6,
278 net->ipv6.devconf_all->hop_limit);
279
280 skb_reset_transport_header(nskb);
281 icmp6h = (struct icmp6hdr *)skb_put(nskb, sizeof(struct icmp6hdr));
282 memset(icmp6h, 0, sizeof(*icmp6h));
283 icmp6h->icmp6_type = ICMPV6_DEST_UNREACH;
284 icmp6h->icmp6_code = code;
285
286 payload = skb_put(nskb, len);
287 memcpy(payload, skb_network_header(oldskb), len);
288 nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
289
290 icmp6h->icmp6_cksum =
291 csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr,
292 nskb->len - sizeof(struct ipv6hdr),
293 IPPROTO_ICMPV6,
294 csum_partial(icmp6h,
295 nskb->len - sizeof(struct ipv6hdr),
296 0));
297
298 nft_reject_br_push_etherhdr(oldskb, nskb);
299
300 br_forward(br_port_get_rcu(dev), nskb, false, true);
301 }
302
nft_reject_bridge_eval(const struct nft_expr * expr,struct nft_regs * regs,const struct nft_pktinfo * pkt)303 static void nft_reject_bridge_eval(const struct nft_expr *expr,
304 struct nft_regs *regs,
305 const struct nft_pktinfo *pkt)
306 {
307 struct nft_reject *priv = nft_expr_priv(expr);
308 const unsigned char *dest = eth_hdr(pkt->skb)->h_dest;
309
310 if (is_broadcast_ether_addr(dest) ||
311 is_multicast_ether_addr(dest))
312 goto out;
313
314 switch (eth_hdr(pkt->skb)->h_proto) {
315 case htons(ETH_P_IP):
316 switch (priv->type) {
317 case NFT_REJECT_ICMP_UNREACH:
318 nft_reject_br_send_v4_unreach(pkt->net, pkt->skb,
319 pkt->in, pkt->hook,
320 priv->icmp_code);
321 break;
322 case NFT_REJECT_TCP_RST:
323 nft_reject_br_send_v4_tcp_reset(pkt->net, pkt->skb,
324 pkt->in, pkt->hook);
325 break;
326 case NFT_REJECT_ICMPX_UNREACH:
327 nft_reject_br_send_v4_unreach(pkt->net, pkt->skb,
328 pkt->in, pkt->hook,
329 nft_reject_icmp_code(priv->icmp_code));
330 break;
331 }
332 break;
333 case htons(ETH_P_IPV6):
334 switch (priv->type) {
335 case NFT_REJECT_ICMP_UNREACH:
336 nft_reject_br_send_v6_unreach(pkt->net, pkt->skb,
337 pkt->in, pkt->hook,
338 priv->icmp_code);
339 break;
340 case NFT_REJECT_TCP_RST:
341 nft_reject_br_send_v6_tcp_reset(pkt->net, pkt->skb,
342 pkt->in, pkt->hook);
343 break;
344 case NFT_REJECT_ICMPX_UNREACH:
345 nft_reject_br_send_v6_unreach(pkt->net, pkt->skb,
346 pkt->in, pkt->hook,
347 nft_reject_icmpv6_code(priv->icmp_code));
348 break;
349 }
350 break;
351 default:
352 /* No explicit way to reject this protocol, drop it. */
353 break;
354 }
355 out:
356 regs->verdict.code = NF_DROP;
357 }
358
nft_reject_bridge_validate(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nft_data ** data)359 static int nft_reject_bridge_validate(const struct nft_ctx *ctx,
360 const struct nft_expr *expr,
361 const struct nft_data **data)
362 {
363 return nft_chain_validate_hooks(ctx->chain, (1 << NF_BR_PRE_ROUTING) |
364 (1 << NF_BR_LOCAL_IN));
365 }
366
nft_reject_bridge_init(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nlattr * const tb[])367 static int nft_reject_bridge_init(const struct nft_ctx *ctx,
368 const struct nft_expr *expr,
369 const struct nlattr * const tb[])
370 {
371 struct nft_reject *priv = nft_expr_priv(expr);
372 int icmp_code, err;
373
374 err = nft_reject_bridge_validate(ctx, expr, NULL);
375 if (err < 0)
376 return err;
377
378 if (tb[NFTA_REJECT_TYPE] == NULL)
379 return -EINVAL;
380
381 priv->type = ntohl(nla_get_be32(tb[NFTA_REJECT_TYPE]));
382 switch (priv->type) {
383 case NFT_REJECT_ICMP_UNREACH:
384 case NFT_REJECT_ICMPX_UNREACH:
385 if (tb[NFTA_REJECT_ICMP_CODE] == NULL)
386 return -EINVAL;
387
388 icmp_code = nla_get_u8(tb[NFTA_REJECT_ICMP_CODE]);
389 if (priv->type == NFT_REJECT_ICMPX_UNREACH &&
390 icmp_code > NFT_REJECT_ICMPX_MAX)
391 return -EINVAL;
392
393 priv->icmp_code = icmp_code;
394 break;
395 case NFT_REJECT_TCP_RST:
396 break;
397 default:
398 return -EINVAL;
399 }
400 return 0;
401 }
402
nft_reject_bridge_dump(struct sk_buff * skb,const struct nft_expr * expr)403 static int nft_reject_bridge_dump(struct sk_buff *skb,
404 const struct nft_expr *expr)
405 {
406 const struct nft_reject *priv = nft_expr_priv(expr);
407
408 if (nla_put_be32(skb, NFTA_REJECT_TYPE, htonl(priv->type)))
409 goto nla_put_failure;
410
411 switch (priv->type) {
412 case NFT_REJECT_ICMP_UNREACH:
413 case NFT_REJECT_ICMPX_UNREACH:
414 if (nla_put_u8(skb, NFTA_REJECT_ICMP_CODE, priv->icmp_code))
415 goto nla_put_failure;
416 break;
417 default:
418 break;
419 }
420
421 return 0;
422
423 nla_put_failure:
424 return -1;
425 }
426
427 static struct nft_expr_type nft_reject_bridge_type;
428 static const struct nft_expr_ops nft_reject_bridge_ops = {
429 .type = &nft_reject_bridge_type,
430 .size = NFT_EXPR_SIZE(sizeof(struct nft_reject)),
431 .eval = nft_reject_bridge_eval,
432 .init = nft_reject_bridge_init,
433 .dump = nft_reject_bridge_dump,
434 .validate = nft_reject_bridge_validate,
435 };
436
437 static struct nft_expr_type nft_reject_bridge_type __read_mostly = {
438 .family = NFPROTO_BRIDGE,
439 .name = "reject",
440 .ops = &nft_reject_bridge_ops,
441 .policy = nft_reject_policy,
442 .maxattr = NFTA_REJECT_MAX,
443 .owner = THIS_MODULE,
444 };
445
nft_reject_bridge_module_init(void)446 static int __init nft_reject_bridge_module_init(void)
447 {
448 return nft_register_expr(&nft_reject_bridge_type);
449 }
450
nft_reject_bridge_module_exit(void)451 static void __exit nft_reject_bridge_module_exit(void)
452 {
453 nft_unregister_expr(&nft_reject_bridge_type);
454 }
455
456 module_init(nft_reject_bridge_module_init);
457 module_exit(nft_reject_bridge_module_exit);
458
459 MODULE_LICENSE("GPL");
460 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
461 MODULE_ALIAS_NFT_AF_EXPR(AF_BRIDGE, "reject");
462