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 "../br_private.h"
24
25static void nft_reject_br_push_etherhdr(struct sk_buff *oldskb,
26					struct sk_buff *nskb)
27{
28	struct ethhdr *eth;
29
30	eth = (struct ethhdr *)skb_push(nskb, ETH_HLEN);
31	skb_reset_mac_header(nskb);
32	ether_addr_copy(eth->h_source, eth_hdr(oldskb)->h_dest);
33	ether_addr_copy(eth->h_dest, eth_hdr(oldskb)->h_source);
34	eth->h_proto = eth_hdr(oldskb)->h_proto;
35	skb_pull(nskb, ETH_HLEN);
36}
37
38static int nft_reject_iphdr_validate(struct sk_buff *oldskb)
39{
40	struct iphdr *iph;
41	u32 len;
42
43	if (!pskb_may_pull(oldskb, sizeof(struct iphdr)))
44		return 0;
45
46	iph = ip_hdr(oldskb);
47	if (iph->ihl < 5 || iph->version != 4)
48		return 0;
49
50	len = ntohs(iph->tot_len);
51	if (oldskb->len < len)
52		return 0;
53	else if (len < (iph->ihl*4))
54		return 0;
55
56	if (!pskb_may_pull(oldskb, iph->ihl*4))
57		return 0;
58
59	return 1;
60}
61
62static void nft_reject_br_send_v4_tcp_reset(struct sk_buff *oldskb, int hook)
63{
64	struct sk_buff *nskb;
65	struct iphdr *niph;
66	const struct tcphdr *oth;
67	struct tcphdr _oth;
68
69	if (!nft_reject_iphdr_validate(oldskb))
70		return;
71
72	oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
73	if (!oth)
74		return;
75
76	nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
77			 LL_MAX_HEADER, GFP_ATOMIC);
78	if (!nskb)
79		return;
80
81	skb_reserve(nskb, LL_MAX_HEADER);
82	niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
83				   sysctl_ip_default_ttl);
84	nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
85	niph->ttl	= sysctl_ip_default_ttl;
86	niph->tot_len	= htons(nskb->len);
87	ip_send_check(niph);
88
89	nft_reject_br_push_etherhdr(oldskb, nskb);
90
91	br_deliver(br_port_get_rcu(oldskb->dev), nskb);
92}
93
94static void nft_reject_br_send_v4_unreach(struct sk_buff *oldskb, int hook,
95					  u8 code)
96{
97	struct sk_buff *nskb;
98	struct iphdr *niph;
99	struct icmphdr *icmph;
100	unsigned int len;
101	void *payload;
102	__wsum csum;
103
104	if (!nft_reject_iphdr_validate(oldskb))
105		return;
106
107	/* IP header checks: fragment. */
108	if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
109		return;
110
111	/* RFC says return as much as we can without exceeding 576 bytes. */
112	len = min_t(unsigned int, 536, oldskb->len);
113
114	if (!pskb_may_pull(oldskb, len))
115		return;
116
117	if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), 0))
118		return;
119
120	nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmphdr) +
121			 LL_MAX_HEADER + len, GFP_ATOMIC);
122	if (!nskb)
123		return;
124
125	skb_reserve(nskb, LL_MAX_HEADER);
126	niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_ICMP,
127				   sysctl_ip_default_ttl);
128
129	skb_reset_transport_header(nskb);
130	icmph = (struct icmphdr *)skb_put(nskb, sizeof(struct icmphdr));
131	memset(icmph, 0, sizeof(*icmph));
132	icmph->type     = ICMP_DEST_UNREACH;
133	icmph->code	= code;
134
135	payload = skb_put(nskb, len);
136	memcpy(payload, skb_network_header(oldskb), len);
137
138	csum = csum_partial((void *)icmph, len + sizeof(struct icmphdr), 0);
139	icmph->checksum = csum_fold(csum);
140
141	niph->tot_len	= htons(nskb->len);
142	ip_send_check(niph);
143
144	nft_reject_br_push_etherhdr(oldskb, nskb);
145
146	br_deliver(br_port_get_rcu(oldskb->dev), nskb);
147}
148
149static int nft_reject_ip6hdr_validate(struct sk_buff *oldskb)
150{
151	struct ipv6hdr *hdr;
152	u32 pkt_len;
153
154	if (!pskb_may_pull(oldskb, sizeof(struct ipv6hdr)))
155		return 0;
156
157	hdr = ipv6_hdr(oldskb);
158	if (hdr->version != 6)
159		return 0;
160
161	pkt_len = ntohs(hdr->payload_len);
162	if (pkt_len + sizeof(struct ipv6hdr) > oldskb->len)
163		return 0;
164
165	return 1;
166}
167
168static void nft_reject_br_send_v6_tcp_reset(struct net *net,
169					    struct sk_buff *oldskb, int hook)
170{
171	struct sk_buff *nskb;
172	const struct tcphdr *oth;
173	struct tcphdr _oth;
174	unsigned int otcplen;
175	struct ipv6hdr *nip6h;
176
177	if (!nft_reject_ip6hdr_validate(oldskb))
178		return;
179
180	oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook);
181	if (!oth)
182		return;
183
184	nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) +
185			 LL_MAX_HEADER, GFP_ATOMIC);
186	if (!nskb)
187		return;
188
189	skb_reserve(nskb, LL_MAX_HEADER);
190	nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
191				     net->ipv6.devconf_all->hop_limit);
192	nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen);
193	nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
194
195	nft_reject_br_push_etherhdr(oldskb, nskb);
196
197	br_deliver(br_port_get_rcu(oldskb->dev), nskb);
198}
199
200static void nft_reject_br_send_v6_unreach(struct net *net,
201					  struct sk_buff *oldskb, int hook,
202					  u8 code)
203{
204	struct sk_buff *nskb;
205	struct ipv6hdr *nip6h;
206	struct icmp6hdr *icmp6h;
207	unsigned int len;
208	void *payload;
209
210	if (!nft_reject_ip6hdr_validate(oldskb))
211		return;
212
213	/* Include "As much of invoking packet as possible without the ICMPv6
214	 * packet exceeding the minimum IPv6 MTU" in the ICMP payload.
215	 */
216	len = min_t(unsigned int, 1220, oldskb->len);
217
218	if (!pskb_may_pull(oldskb, len))
219		return;
220
221	nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmp6hdr) +
222			 LL_MAX_HEADER + len, GFP_ATOMIC);
223	if (!nskb)
224		return;
225
226	skb_reserve(nskb, LL_MAX_HEADER);
227	nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6,
228				     net->ipv6.devconf_all->hop_limit);
229
230	skb_reset_transport_header(nskb);
231	icmp6h = (struct icmp6hdr *)skb_put(nskb, sizeof(struct icmp6hdr));
232	memset(icmp6h, 0, sizeof(*icmp6h));
233	icmp6h->icmp6_type = ICMPV6_DEST_UNREACH;
234	icmp6h->icmp6_code = code;
235
236	payload = skb_put(nskb, len);
237	memcpy(payload, skb_network_header(oldskb), len);
238	nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
239
240	icmp6h->icmp6_cksum =
241		csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr,
242				nskb->len - sizeof(struct ipv6hdr),
243				IPPROTO_ICMPV6,
244				csum_partial(icmp6h,
245					     nskb->len - sizeof(struct ipv6hdr),
246					     0));
247
248	nft_reject_br_push_etherhdr(oldskb, nskb);
249
250	br_deliver(br_port_get_rcu(oldskb->dev), nskb);
251}
252
253static void nft_reject_bridge_eval(const struct nft_expr *expr,
254				 struct nft_data data[NFT_REG_MAX + 1],
255				 const struct nft_pktinfo *pkt)
256{
257	struct nft_reject *priv = nft_expr_priv(expr);
258	struct net *net = dev_net((pkt->in != NULL) ? pkt->in : pkt->out);
259	const unsigned char *dest = eth_hdr(pkt->skb)->h_dest;
260
261	if (is_broadcast_ether_addr(dest) ||
262	    is_multicast_ether_addr(dest))
263		goto out;
264
265	switch (eth_hdr(pkt->skb)->h_proto) {
266	case htons(ETH_P_IP):
267		switch (priv->type) {
268		case NFT_REJECT_ICMP_UNREACH:
269			nft_reject_br_send_v4_unreach(pkt->skb,
270						      pkt->ops->hooknum,
271						      priv->icmp_code);
272			break;
273		case NFT_REJECT_TCP_RST:
274			nft_reject_br_send_v4_tcp_reset(pkt->skb,
275							pkt->ops->hooknum);
276			break;
277		case NFT_REJECT_ICMPX_UNREACH:
278			nft_reject_br_send_v4_unreach(pkt->skb,
279						      pkt->ops->hooknum,
280						      nft_reject_icmp_code(priv->icmp_code));
281			break;
282		}
283		break;
284	case htons(ETH_P_IPV6):
285		switch (priv->type) {
286		case NFT_REJECT_ICMP_UNREACH:
287			nft_reject_br_send_v6_unreach(net, pkt->skb,
288						      pkt->ops->hooknum,
289						      priv->icmp_code);
290			break;
291		case NFT_REJECT_TCP_RST:
292			nft_reject_br_send_v6_tcp_reset(net, pkt->skb,
293							pkt->ops->hooknum);
294			break;
295		case NFT_REJECT_ICMPX_UNREACH:
296			nft_reject_br_send_v6_unreach(net, pkt->skb,
297						      pkt->ops->hooknum,
298						      nft_reject_icmpv6_code(priv->icmp_code));
299			break;
300		}
301		break;
302	default:
303		/* No explicit way to reject this protocol, drop it. */
304		break;
305	}
306out:
307	data[NFT_REG_VERDICT].verdict = NF_DROP;
308}
309
310static int nft_reject_bridge_validate_hooks(const struct nft_chain *chain)
311{
312	struct nft_base_chain *basechain;
313
314	if (chain->flags & NFT_BASE_CHAIN) {
315		basechain = nft_base_chain(chain);
316
317		switch (basechain->ops[0].hooknum) {
318		case NF_BR_PRE_ROUTING:
319		case NF_BR_LOCAL_IN:
320			break;
321		default:
322			return -EOPNOTSUPP;
323		}
324	}
325	return 0;
326}
327
328static int nft_reject_bridge_init(const struct nft_ctx *ctx,
329				  const struct nft_expr *expr,
330				  const struct nlattr * const tb[])
331{
332	struct nft_reject *priv = nft_expr_priv(expr);
333	int icmp_code, err;
334
335	err = nft_reject_bridge_validate_hooks(ctx->chain);
336	if (err < 0)
337		return err;
338
339	if (tb[NFTA_REJECT_TYPE] == NULL)
340		return -EINVAL;
341
342	priv->type = ntohl(nla_get_be32(tb[NFTA_REJECT_TYPE]));
343	switch (priv->type) {
344	case NFT_REJECT_ICMP_UNREACH:
345	case NFT_REJECT_ICMPX_UNREACH:
346		if (tb[NFTA_REJECT_ICMP_CODE] == NULL)
347			return -EINVAL;
348
349		icmp_code = nla_get_u8(tb[NFTA_REJECT_ICMP_CODE]);
350		if (priv->type == NFT_REJECT_ICMPX_UNREACH &&
351		    icmp_code > NFT_REJECT_ICMPX_MAX)
352			return -EINVAL;
353
354		priv->icmp_code = icmp_code;
355		break;
356	case NFT_REJECT_TCP_RST:
357		break;
358	default:
359		return -EINVAL;
360	}
361	return 0;
362}
363
364static int nft_reject_bridge_dump(struct sk_buff *skb,
365				  const struct nft_expr *expr)
366{
367	const struct nft_reject *priv = nft_expr_priv(expr);
368
369	if (nla_put_be32(skb, NFTA_REJECT_TYPE, htonl(priv->type)))
370		goto nla_put_failure;
371
372	switch (priv->type) {
373	case NFT_REJECT_ICMP_UNREACH:
374	case NFT_REJECT_ICMPX_UNREACH:
375		if (nla_put_u8(skb, NFTA_REJECT_ICMP_CODE, priv->icmp_code))
376			goto nla_put_failure;
377		break;
378	}
379
380	return 0;
381
382nla_put_failure:
383	return -1;
384}
385
386static int nft_reject_bridge_validate(const struct nft_ctx *ctx,
387				      const struct nft_expr *expr,
388				      const struct nft_data **data)
389{
390	return nft_reject_bridge_validate_hooks(ctx->chain);
391}
392
393static struct nft_expr_type nft_reject_bridge_type;
394static const struct nft_expr_ops nft_reject_bridge_ops = {
395	.type		= &nft_reject_bridge_type,
396	.size		= NFT_EXPR_SIZE(sizeof(struct nft_reject)),
397	.eval		= nft_reject_bridge_eval,
398	.init		= nft_reject_bridge_init,
399	.dump		= nft_reject_bridge_dump,
400	.validate	= nft_reject_bridge_validate,
401};
402
403static struct nft_expr_type nft_reject_bridge_type __read_mostly = {
404	.family		= NFPROTO_BRIDGE,
405	.name		= "reject",
406	.ops		= &nft_reject_bridge_ops,
407	.policy		= nft_reject_policy,
408	.maxattr	= NFTA_REJECT_MAX,
409	.owner		= THIS_MODULE,
410};
411
412static int __init nft_reject_bridge_module_init(void)
413{
414	return nft_register_expr(&nft_reject_bridge_type);
415}
416
417static void __exit nft_reject_bridge_module_exit(void)
418{
419	nft_unregister_expr(&nft_reject_bridge_type);
420}
421
422module_init(nft_reject_bridge_module_init);
423module_exit(nft_reject_bridge_module_exit);
424
425MODULE_LICENSE("GPL");
426MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
427MODULE_ALIAS_NFT_AF_EXPR(AF_BRIDGE, "reject");
428