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1 | // SPDX-License-Identifier: GPL-2.0-only | |
2 | /* | |
3 | * Copyright (c) 2014 Pablo Neira Ayuso <pablo@netfilter.org> | |
4 | */ | |
5 | ||
6 | #include <linux/kernel.h> | |
7 | #include <linux/init.h> | |
8 | #include <linux/module.h> | |
9 | #include <linux/netlink.h> | |
10 | #include <linux/netfilter.h> | |
11 | #include <linux/netfilter/nf_tables.h> | |
12 | #include <net/netfilter/nf_tables.h> | |
13 | #include <net/netfilter/nft_reject.h> | |
14 | #include <net/netfilter/ipv4/nf_reject.h> | |
15 | #include <net/netfilter/ipv6/nf_reject.h> | |
16 | #include <linux/ip.h> | |
17 | #include <net/ip.h> | |
18 | #include <net/ip6_checksum.h> | |
19 | #include <linux/netfilter_bridge.h> | |
20 | #include <linux/netfilter_ipv6.h> | |
21 | #include "../br_private.h" | |
22 | ||
23 | static void nft_reject_br_push_etherhdr(struct sk_buff *oldskb, | |
24 | struct sk_buff *nskb) | |
25 | { | |
26 | struct ethhdr *eth; | |
27 | ||
28 | eth = skb_push(nskb, ETH_HLEN); | |
29 | skb_reset_mac_header(nskb); | |
30 | ether_addr_copy(eth->h_source, eth_hdr(oldskb)->h_dest); | |
31 | ether_addr_copy(eth->h_dest, eth_hdr(oldskb)->h_source); | |
32 | eth->h_proto = eth_hdr(oldskb)->h_proto; | |
33 | skb_pull(nskb, ETH_HLEN); | |
34 | } | |
35 | ||
36 | static int nft_bridge_iphdr_validate(struct sk_buff *skb) | |
37 | { | |
38 | struct iphdr *iph; | |
39 | u32 len; | |
40 | ||
41 | if (!pskb_may_pull(skb, sizeof(struct iphdr))) | |
42 | return 0; | |
43 | ||
44 | iph = ip_hdr(skb); | |
45 | if (iph->ihl < 5 || iph->version != 4) | |
46 | return 0; | |
47 | ||
48 | len = ntohs(iph->tot_len); | |
49 | if (skb->len < len) | |
50 | return 0; | |
51 | else if (len < (iph->ihl*4)) | |
52 | return 0; | |
53 | ||
54 | if (!pskb_may_pull(skb, iph->ihl*4)) | |
55 | return 0; | |
56 | ||
57 | return 1; | |
58 | } | |
59 | ||
60 | /* We cannot use oldskb->dev, it can be either bridge device (NF_BRIDGE INPUT) | |
61 | * or the bridge port (NF_BRIDGE PREROUTING). | |
62 | */ | |
63 | static void nft_reject_br_send_v4_tcp_reset(struct net *net, | |
64 | struct sk_buff *oldskb, | |
65 | const struct net_device *dev, | |
66 | int hook) | |
67 | { | |
68 | struct sk_buff *nskb; | |
69 | struct iphdr *niph; | |
70 | const struct tcphdr *oth; | |
71 | struct tcphdr _oth; | |
72 | ||
73 | if (!nft_bridge_iphdr_validate(oldskb)) | |
74 | return; | |
75 | ||
76 | oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook); | |
77 | if (!oth) | |
78 | return; | |
79 | ||
80 | nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) + | |
81 | LL_MAX_HEADER, GFP_ATOMIC); | |
82 | if (!nskb) | |
83 | return; | |
84 | ||
85 | skb_reserve(nskb, LL_MAX_HEADER); | |
86 | niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP, | |
87 | net->ipv4.sysctl_ip_default_ttl); | |
88 | nf_reject_ip_tcphdr_put(nskb, oldskb, oth); | |
89 | niph->tot_len = htons(nskb->len); | |
90 | ip_send_check(niph); | |
91 | ||
92 | nft_reject_br_push_etherhdr(oldskb, nskb); | |
93 | ||
94 | br_forward(br_port_get_rcu(dev), nskb, false, true); | |
95 | } | |
96 | ||
97 | static void nft_reject_br_send_v4_unreach(struct net *net, | |
98 | struct sk_buff *oldskb, | |
99 | const struct net_device *dev, | |
100 | int hook, u8 code) | |
101 | { | |
102 | struct sk_buff *nskb; | |
103 | struct iphdr *niph; | |
104 | struct icmphdr *icmph; | |
105 | unsigned int len; | |
106 | __wsum csum; | |
107 | u8 proto; | |
108 | ||
109 | if (!nft_bridge_iphdr_validate(oldskb)) | |
110 | return; | |
111 | ||
112 | /* IP header checks: fragment. */ | |
113 | if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET)) | |
114 | return; | |
115 | ||
116 | /* RFC says return as much as we can without exceeding 576 bytes. */ | |
117 | len = min_t(unsigned int, 536, oldskb->len); | |
118 | ||
119 | if (!pskb_may_pull(oldskb, len)) | |
120 | return; | |
121 | ||
122 | if (pskb_trim_rcsum(oldskb, ntohs(ip_hdr(oldskb)->tot_len))) | |
123 | return; | |
124 | ||
125 | proto = ip_hdr(oldskb)->protocol; | |
126 | ||
127 | if (!skb_csum_unnecessary(oldskb) && | |
128 | nf_reject_verify_csum(proto) && | |
129 | nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), proto)) | |
130 | return; | |
131 | ||
132 | nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmphdr) + | |
133 | LL_MAX_HEADER + len, GFP_ATOMIC); | |
134 | if (!nskb) | |
135 | return; | |
136 | ||
137 | skb_reserve(nskb, LL_MAX_HEADER); | |
138 | niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_ICMP, | |
139 | net->ipv4.sysctl_ip_default_ttl); | |
140 | ||
141 | skb_reset_transport_header(nskb); | |
142 | icmph = skb_put_zero(nskb, sizeof(struct icmphdr)); | |
143 | icmph->type = ICMP_DEST_UNREACH; | |
144 | icmph->code = code; | |
145 | ||
146 | skb_put_data(nskb, skb_network_header(oldskb), len); | |
147 | ||
148 | csum = csum_partial((void *)icmph, len + sizeof(struct icmphdr), 0); | |
149 | icmph->checksum = csum_fold(csum); | |
150 | ||
151 | niph->tot_len = htons(nskb->len); | |
152 | ip_send_check(niph); | |
153 | ||
154 | nft_reject_br_push_etherhdr(oldskb, nskb); | |
155 | ||
156 | br_forward(br_port_get_rcu(dev), nskb, false, true); | |
157 | } | |
158 | ||
159 | static int nft_bridge_ip6hdr_validate(struct sk_buff *skb) | |
160 | { | |
161 | struct ipv6hdr *hdr; | |
162 | u32 pkt_len; | |
163 | ||
164 | if (!pskb_may_pull(skb, sizeof(struct ipv6hdr))) | |
165 | return 0; | |
166 | ||
167 | hdr = ipv6_hdr(skb); | |
168 | if (hdr->version != 6) | |
169 | return 0; | |
170 | ||
171 | pkt_len = ntohs(hdr->payload_len); | |
172 | if (pkt_len + sizeof(struct ipv6hdr) > skb->len) | |
173 | return 0; | |
174 | ||
175 | return 1; | |
176 | } | |
177 | ||
178 | static void nft_reject_br_send_v6_tcp_reset(struct net *net, | |
179 | struct sk_buff *oldskb, | |
180 | const struct net_device *dev, | |
181 | int hook) | |
182 | { | |
183 | struct sk_buff *nskb; | |
184 | const struct tcphdr *oth; | |
185 | struct tcphdr _oth; | |
186 | unsigned int otcplen; | |
187 | struct ipv6hdr *nip6h; | |
188 | ||
189 | if (!nft_bridge_ip6hdr_validate(oldskb)) | |
190 | return; | |
191 | ||
192 | oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook); | |
193 | if (!oth) | |
194 | return; | |
195 | ||
196 | nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) + | |
197 | LL_MAX_HEADER, GFP_ATOMIC); | |
198 | if (!nskb) | |
199 | return; | |
200 | ||
201 | skb_reserve(nskb, LL_MAX_HEADER); | |
202 | nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP, | |
203 | net->ipv6.devconf_all->hop_limit); | |
204 | nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen); | |
205 | nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr)); | |
206 | ||
207 | nft_reject_br_push_etherhdr(oldskb, nskb); | |
208 | ||
209 | br_forward(br_port_get_rcu(dev), nskb, false, true); | |
210 | } | |
211 | ||
212 | static bool reject6_br_csum_ok(struct sk_buff *skb, int hook) | |
213 | { | |
214 | const struct ipv6hdr *ip6h = ipv6_hdr(skb); | |
215 | int thoff; | |
216 | __be16 fo; | |
217 | u8 proto = ip6h->nexthdr; | |
218 | ||
219 | if (skb_csum_unnecessary(skb)) | |
220 | return true; | |
221 | ||
222 | if (ip6h->payload_len && | |
223 | pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h))) | |
224 | return false; | |
225 | ||
226 | ip6h = ipv6_hdr(skb); | |
227 | thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo); | |
228 | if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0) | |
229 | return false; | |
230 | ||
231 | if (!nf_reject_verify_csum(proto)) | |
232 | return true; | |
233 | ||
234 | return nf_ip6_checksum(skb, hook, thoff, proto) == 0; | |
235 | } | |
236 | ||
237 | static void nft_reject_br_send_v6_unreach(struct net *net, | |
238 | struct sk_buff *oldskb, | |
239 | const struct net_device *dev, | |
240 | int hook, u8 code) | |
241 | { | |
242 | struct sk_buff *nskb; | |
243 | struct ipv6hdr *nip6h; | |
244 | struct icmp6hdr *icmp6h; | |
245 | unsigned int len; | |
246 | ||
247 | if (!nft_bridge_ip6hdr_validate(oldskb)) | |
248 | return; | |
249 | ||
250 | /* Include "As much of invoking packet as possible without the ICMPv6 | |
251 | * packet exceeding the minimum IPv6 MTU" in the ICMP payload. | |
252 | */ | |
253 | len = min_t(unsigned int, 1220, oldskb->len); | |
254 | ||
255 | if (!pskb_may_pull(oldskb, len)) | |
256 | return; | |
257 | ||
258 | if (!reject6_br_csum_ok(oldskb, hook)) | |
259 | return; | |
260 | ||
261 | nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct icmp6hdr) + | |
262 | LL_MAX_HEADER + len, GFP_ATOMIC); | |
263 | if (!nskb) | |
264 | return; | |
265 | ||
266 | skb_reserve(nskb, LL_MAX_HEADER); | |
267 | nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6, | |
268 | net->ipv6.devconf_all->hop_limit); | |
269 | ||
270 | skb_reset_transport_header(nskb); | |
271 | icmp6h = skb_put_zero(nskb, sizeof(struct icmp6hdr)); | |
272 | icmp6h->icmp6_type = ICMPV6_DEST_UNREACH; | |
273 | icmp6h->icmp6_code = code; | |
274 | ||
275 | skb_put_data(nskb, skb_network_header(oldskb), len); | |
276 | nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr)); | |
277 | ||
278 | icmp6h->icmp6_cksum = | |
279 | csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr, | |
280 | nskb->len - sizeof(struct ipv6hdr), | |
281 | IPPROTO_ICMPV6, | |
282 | csum_partial(icmp6h, | |
283 | nskb->len - sizeof(struct ipv6hdr), | |
284 | 0)); | |
285 | ||
286 | nft_reject_br_push_etherhdr(oldskb, nskb); | |
287 | ||
288 | br_forward(br_port_get_rcu(dev), nskb, false, true); | |
289 | } | |
290 | ||
291 | static void nft_reject_bridge_eval(const struct nft_expr *expr, | |
292 | struct nft_regs *regs, | |
293 | const struct nft_pktinfo *pkt) | |
294 | { | |
295 | struct nft_reject *priv = nft_expr_priv(expr); | |
296 | const unsigned char *dest = eth_hdr(pkt->skb)->h_dest; | |
297 | ||
298 | if (is_broadcast_ether_addr(dest) || | |
299 | is_multicast_ether_addr(dest)) | |
300 | goto out; | |
301 | ||
302 | switch (eth_hdr(pkt->skb)->h_proto) { | |
303 | case htons(ETH_P_IP): | |
304 | switch (priv->type) { | |
305 | case NFT_REJECT_ICMP_UNREACH: | |
306 | nft_reject_br_send_v4_unreach(nft_net(pkt), pkt->skb, | |
307 | nft_in(pkt), | |
308 | nft_hook(pkt), | |
309 | priv->icmp_code); | |
310 | break; | |
311 | case NFT_REJECT_TCP_RST: | |
312 | nft_reject_br_send_v4_tcp_reset(nft_net(pkt), pkt->skb, | |
313 | nft_in(pkt), | |
314 | nft_hook(pkt)); | |
315 | break; | |
316 | case NFT_REJECT_ICMPX_UNREACH: | |
317 | nft_reject_br_send_v4_unreach(nft_net(pkt), pkt->skb, | |
318 | nft_in(pkt), | |
319 | nft_hook(pkt), | |
320 | nft_reject_icmp_code(priv->icmp_code)); | |
321 | break; | |
322 | } | |
323 | break; | |
324 | case htons(ETH_P_IPV6): | |
325 | switch (priv->type) { | |
326 | case NFT_REJECT_ICMP_UNREACH: | |
327 | nft_reject_br_send_v6_unreach(nft_net(pkt), pkt->skb, | |
328 | nft_in(pkt), | |
329 | nft_hook(pkt), | |
330 | priv->icmp_code); | |
331 | break; | |
332 | case NFT_REJECT_TCP_RST: | |
333 | nft_reject_br_send_v6_tcp_reset(nft_net(pkt), pkt->skb, | |
334 | nft_in(pkt), | |
335 | nft_hook(pkt)); | |
336 | break; | |
337 | case NFT_REJECT_ICMPX_UNREACH: | |
338 | nft_reject_br_send_v6_unreach(nft_net(pkt), pkt->skb, | |
339 | nft_in(pkt), | |
340 | nft_hook(pkt), | |
341 | nft_reject_icmpv6_code(priv->icmp_code)); | |
342 | break; | |
343 | } | |
344 | break; | |
345 | default: | |
346 | /* No explicit way to reject this protocol, drop it. */ | |
347 | break; | |
348 | } | |
349 | out: | |
350 | regs->verdict.code = NF_DROP; | |
351 | } | |
352 | ||
353 | static int nft_reject_bridge_validate(const struct nft_ctx *ctx, | |
354 | const struct nft_expr *expr, | |
355 | const struct nft_data **data) | |
356 | { | |
357 | return nft_chain_validate_hooks(ctx->chain, (1 << NF_BR_PRE_ROUTING) | | |
358 | (1 << NF_BR_LOCAL_IN)); | |
359 | } | |
360 | ||
361 | static int nft_reject_bridge_init(const struct nft_ctx *ctx, | |
362 | const struct nft_expr *expr, | |
363 | const struct nlattr * const tb[]) | |
364 | { | |
365 | struct nft_reject *priv = nft_expr_priv(expr); | |
366 | int icmp_code; | |
367 | ||
368 | if (tb[NFTA_REJECT_TYPE] == NULL) | |
369 | return -EINVAL; | |
370 | ||
371 | priv->type = ntohl(nla_get_be32(tb[NFTA_REJECT_TYPE])); | |
372 | switch (priv->type) { | |
373 | case NFT_REJECT_ICMP_UNREACH: | |
374 | case NFT_REJECT_ICMPX_UNREACH: | |
375 | if (tb[NFTA_REJECT_ICMP_CODE] == NULL) | |
376 | return -EINVAL; | |
377 | ||
378 | icmp_code = nla_get_u8(tb[NFTA_REJECT_ICMP_CODE]); | |
379 | if (priv->type == NFT_REJECT_ICMPX_UNREACH && | |
380 | icmp_code > NFT_REJECT_ICMPX_MAX) | |
381 | return -EINVAL; | |
382 | ||
383 | priv->icmp_code = icmp_code; | |
384 | break; | |
385 | case NFT_REJECT_TCP_RST: | |
386 | break; | |
387 | default: | |
388 | return -EINVAL; | |
389 | } | |
390 | return 0; | |
391 | } | |
392 | ||
393 | static int nft_reject_bridge_dump(struct sk_buff *skb, | |
394 | const struct nft_expr *expr) | |
395 | { | |
396 | const struct nft_reject *priv = nft_expr_priv(expr); | |
397 | ||
398 | if (nla_put_be32(skb, NFTA_REJECT_TYPE, htonl(priv->type))) | |
399 | goto nla_put_failure; | |
400 | ||
401 | switch (priv->type) { | |
402 | case NFT_REJECT_ICMP_UNREACH: | |
403 | case NFT_REJECT_ICMPX_UNREACH: | |
404 | if (nla_put_u8(skb, NFTA_REJECT_ICMP_CODE, priv->icmp_code)) | |
405 | goto nla_put_failure; | |
406 | break; | |
407 | default: | |
408 | break; | |
409 | } | |
410 | ||
411 | return 0; | |
412 | ||
413 | nla_put_failure: | |
414 | return -1; | |
415 | } | |
416 | ||
417 | static struct nft_expr_type nft_reject_bridge_type; | |
418 | static const struct nft_expr_ops nft_reject_bridge_ops = { | |
419 | .type = &nft_reject_bridge_type, | |
420 | .size = NFT_EXPR_SIZE(sizeof(struct nft_reject)), | |
421 | .eval = nft_reject_bridge_eval, | |
422 | .init = nft_reject_bridge_init, | |
423 | .dump = nft_reject_bridge_dump, | |
424 | .validate = nft_reject_bridge_validate, | |
425 | }; | |
426 | ||
427 | static struct nft_expr_type nft_reject_bridge_type __read_mostly = { | |
428 | .family = NFPROTO_BRIDGE, | |
429 | .name = "reject", | |
430 | .ops = &nft_reject_bridge_ops, | |
431 | .policy = nft_reject_policy, | |
432 | .maxattr = NFTA_REJECT_MAX, | |
433 | .owner = THIS_MODULE, | |
434 | }; | |
435 | ||
436 | static int __init nft_reject_bridge_module_init(void) | |
437 | { | |
438 | return nft_register_expr(&nft_reject_bridge_type); | |
439 | } | |
440 | ||
441 | static void __exit nft_reject_bridge_module_exit(void) | |
442 | { | |
443 | nft_unregister_expr(&nft_reject_bridge_type); | |
444 | } | |
445 | ||
446 | module_init(nft_reject_bridge_module_init); | |
447 | module_exit(nft_reject_bridge_module_exit); | |
448 | ||
449 | MODULE_LICENSE("GPL"); | |
450 | MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>"); | |
451 | MODULE_ALIAS_NFT_AF_EXPR(AF_BRIDGE, "reject"); |