1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* (C) 1999-2001 Paul `Rusty' Russell |
3 | * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> |
4 | * (C) 2006-2010 Patrick McHardy <kaber@trash.net> |
5 | */ |
6 | |
7 | #include <linux/types.h> |
8 | #include <linux/timer.h> |
9 | #include <linux/netfilter.h> |
10 | #include <linux/in.h> |
11 | #include <linux/icmp.h> |
12 | #include <linux/seq_file.h> |
13 | #include <net/ip.h> |
14 | #include <net/checksum.h> |
15 | #include <linux/netfilter_ipv4.h> |
16 | #include <net/netfilter/nf_conntrack_tuple.h> |
17 | #include <net/netfilter/nf_conntrack_l4proto.h> |
18 | #include <net/netfilter/nf_conntrack_core.h> |
19 | #include <net/netfilter/nf_conntrack_timeout.h> |
20 | #include <net/netfilter/nf_conntrack_zones.h> |
21 | #include <net/netfilter/nf_log.h> |
22 | |
23 | #include "nf_internals.h" |
24 | |
25 | static const unsigned int nf_ct_icmp_timeout = 30*HZ; |
26 | |
27 | bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff, |
28 | struct net *net, struct nf_conntrack_tuple *tuple) |
29 | { |
30 | const struct icmphdr *hp; |
31 | struct icmphdr _hdr; |
32 | |
33 | hp = skb_header_pointer(skb, offset: dataoff, len: sizeof(_hdr), buffer: &_hdr); |
34 | if (hp == NULL) |
35 | return false; |
36 | |
37 | tuple->dst.u.icmp.type = hp->type; |
38 | tuple->src.u.icmp.id = hp->un.echo.id; |
39 | tuple->dst.u.icmp.code = hp->code; |
40 | |
41 | return true; |
42 | } |
43 | |
44 | /* Add 1; spaces filled with 0. */ |
45 | static const u_int8_t invmap[] = { |
46 | [ICMP_ECHO] = ICMP_ECHOREPLY + 1, |
47 | [ICMP_ECHOREPLY] = ICMP_ECHO + 1, |
48 | [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1, |
49 | [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1, |
50 | [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1, |
51 | [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1, |
52 | [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1, |
53 | [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1 |
54 | }; |
55 | |
56 | bool nf_conntrack_invert_icmp_tuple(struct nf_conntrack_tuple *tuple, |
57 | const struct nf_conntrack_tuple *orig) |
58 | { |
59 | if (orig->dst.u.icmp.type >= sizeof(invmap) || |
60 | !invmap[orig->dst.u.icmp.type]) |
61 | return false; |
62 | |
63 | tuple->src.u.icmp.id = orig->src.u.icmp.id; |
64 | tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1; |
65 | tuple->dst.u.icmp.code = orig->dst.u.icmp.code; |
66 | return true; |
67 | } |
68 | |
69 | /* Returns verdict for packet, or -1 for invalid. */ |
70 | int nf_conntrack_icmp_packet(struct nf_conn *ct, |
71 | struct sk_buff *skb, |
72 | enum ip_conntrack_info ctinfo, |
73 | const struct nf_hook_state *state) |
74 | { |
75 | /* Do not immediately delete the connection after the first |
76 | successful reply to avoid excessive conntrackd traffic |
77 | and also to handle correctly ICMP echo reply duplicates. */ |
78 | unsigned int *timeout = nf_ct_timeout_lookup(ct); |
79 | static const u_int8_t valid_new[] = { |
80 | [ICMP_ECHO] = 1, |
81 | [ICMP_TIMESTAMP] = 1, |
82 | [ICMP_INFO_REQUEST] = 1, |
83 | [ICMP_ADDRESS] = 1 |
84 | }; |
85 | |
86 | if (state->pf != NFPROTO_IPV4) |
87 | return -NF_ACCEPT; |
88 | |
89 | if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) || |
90 | !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) { |
91 | /* Can't create a new ICMP `conn' with this. */ |
92 | pr_debug("icmp: can't create new conn with type %u\n" , |
93 | ct->tuplehash[0].tuple.dst.u.icmp.type); |
94 | nf_ct_dump_tuple_ip(t: &ct->tuplehash[0].tuple); |
95 | return -NF_ACCEPT; |
96 | } |
97 | |
98 | if (!timeout) |
99 | timeout = &nf_icmp_pernet(net: nf_ct_net(ct))->timeout; |
100 | |
101 | nf_ct_refresh_acct(ct, ctinfo, skb, extra_jiffies: *timeout); |
102 | return NF_ACCEPT; |
103 | } |
104 | |
105 | /* Check inner header is related to any of the existing connections */ |
106 | int nf_conntrack_inet_error(struct nf_conn *tmpl, struct sk_buff *skb, |
107 | unsigned int dataoff, |
108 | const struct nf_hook_state *state, |
109 | u8 l4proto, union nf_inet_addr *outer_daddr) |
110 | { |
111 | struct nf_conntrack_tuple innertuple, origtuple; |
112 | const struct nf_conntrack_tuple_hash *h; |
113 | const struct nf_conntrack_zone *zone; |
114 | enum ip_conntrack_info ctinfo; |
115 | struct nf_conntrack_zone tmp; |
116 | union nf_inet_addr *ct_daddr; |
117 | enum ip_conntrack_dir dir; |
118 | struct nf_conn *ct; |
119 | |
120 | WARN_ON(skb_nfct(skb)); |
121 | zone = nf_ct_zone_tmpl(tmpl, skb, tmp: &tmp); |
122 | |
123 | /* Are they talking about one of our connections? */ |
124 | if (!nf_ct_get_tuplepr(skb, nhoff: dataoff, |
125 | l3num: state->pf, net: state->net, tuple: &origtuple)) |
126 | return -NF_ACCEPT; |
127 | |
128 | /* Ordinarily, we'd expect the inverted tupleproto, but it's |
129 | been preserved inside the ICMP. */ |
130 | if (!nf_ct_invert_tuple(inverse: &innertuple, orig: &origtuple)) |
131 | return -NF_ACCEPT; |
132 | |
133 | h = nf_conntrack_find_get(net: state->net, zone, tuple: &innertuple); |
134 | if (!h) |
135 | return -NF_ACCEPT; |
136 | |
137 | /* Consider: A -> T (=This machine) -> B |
138 | * Conntrack entry will look like this: |
139 | * Original: A->B |
140 | * Reply: B->T (SNAT case) OR A |
141 | * |
142 | * When this function runs, we got packet that looks like this: |
143 | * iphdr|icmphdr|inner_iphdr|l4header (tcp, udp, ..). |
144 | * |
145 | * Above nf_conntrack_find_get() makes lookup based on inner_hdr, |
146 | * so we should expect that destination of the found connection |
147 | * matches outer header destination address. |
148 | * |
149 | * In above example, we can consider these two cases: |
150 | * 1. Error coming in reply direction from B or M (middle box) to |
151 | * T (SNAT case) or A. |
152 | * Inner saddr will be B, dst will be T or A. |
153 | * The found conntrack will be reply tuple (B->T/A). |
154 | * 2. Error coming in original direction from A or M to B. |
155 | * Inner saddr will be A, inner daddr will be B. |
156 | * The found conntrack will be original tuple (A->B). |
157 | * |
158 | * In both cases, conntrack[dir].dst == inner.dst. |
159 | * |
160 | * A bogus packet could look like this: |
161 | * Inner: B->T |
162 | * Outer: B->X (other machine reachable by T). |
163 | * |
164 | * In this case, lookup yields connection A->B and will |
165 | * set packet from B->X as *RELATED*, even though no connection |
166 | * from X was ever seen. |
167 | */ |
168 | ct = nf_ct_tuplehash_to_ctrack(hash: h); |
169 | dir = NF_CT_DIRECTION(h); |
170 | ct_daddr = &ct->tuplehash[dir].tuple.dst.u3; |
171 | if (!nf_inet_addr_cmp(a1: outer_daddr, a2: ct_daddr)) { |
172 | if (state->pf == AF_INET) { |
173 | nf_l4proto_log_invalid(skb, state, |
174 | protonum: l4proto, |
175 | fmt: "outer daddr %pI4 != inner %pI4" , |
176 | &outer_daddr->ip, &ct_daddr->ip); |
177 | } else if (state->pf == AF_INET6) { |
178 | nf_l4proto_log_invalid(skb, state, |
179 | protonum: l4proto, |
180 | fmt: "outer daddr %pI6 != inner %pI6" , |
181 | &outer_daddr->ip6, &ct_daddr->ip6); |
182 | } |
183 | nf_ct_put(ct); |
184 | return -NF_ACCEPT; |
185 | } |
186 | |
187 | ctinfo = IP_CT_RELATED; |
188 | if (dir == IP_CT_DIR_REPLY) |
189 | ctinfo += IP_CT_IS_REPLY; |
190 | |
191 | /* Update skb to refer to this connection */ |
192 | nf_ct_set(skb, ct, info: ctinfo); |
193 | return NF_ACCEPT; |
194 | } |
195 | |
196 | static void icmp_error_log(const struct sk_buff *skb, |
197 | const struct nf_hook_state *state, |
198 | const char *msg) |
199 | { |
200 | nf_l4proto_log_invalid(skb, state, IPPROTO_ICMP, fmt: "%s" , msg); |
201 | } |
202 | |
203 | /* Small and modified version of icmp_rcv */ |
204 | int nf_conntrack_icmpv4_error(struct nf_conn *tmpl, |
205 | struct sk_buff *skb, unsigned int dataoff, |
206 | const struct nf_hook_state *state) |
207 | { |
208 | union nf_inet_addr outer_daddr; |
209 | const struct icmphdr *icmph; |
210 | struct icmphdr _ih; |
211 | |
212 | /* Not enough header? */ |
213 | icmph = skb_header_pointer(skb, offset: dataoff, len: sizeof(_ih), buffer: &_ih); |
214 | if (icmph == NULL) { |
215 | icmp_error_log(skb, state, msg: "short packet" ); |
216 | return -NF_ACCEPT; |
217 | } |
218 | |
219 | /* See nf_conntrack_proto_tcp.c */ |
220 | if (state->net->ct.sysctl_checksum && |
221 | state->hook == NF_INET_PRE_ROUTING && |
222 | nf_ip_checksum(skb, hook: state->hook, dataoff, IPPROTO_ICMP)) { |
223 | icmp_error_log(skb, state, msg: "bad hw icmp checksum" ); |
224 | return -NF_ACCEPT; |
225 | } |
226 | |
227 | /* |
228 | * 18 is the highest 'known' ICMP type. Anything else is a mystery |
229 | * |
230 | * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently |
231 | * discarded. |
232 | */ |
233 | if (icmph->type > NR_ICMP_TYPES) { |
234 | icmp_error_log(skb, state, msg: "invalid icmp type" ); |
235 | return -NF_ACCEPT; |
236 | } |
237 | |
238 | /* Need to track icmp error message? */ |
239 | if (!icmp_is_err(type: icmph->type)) |
240 | return NF_ACCEPT; |
241 | |
242 | memset(&outer_daddr, 0, sizeof(outer_daddr)); |
243 | outer_daddr.ip = ip_hdr(skb)->daddr; |
244 | |
245 | dataoff += sizeof(*icmph); |
246 | return nf_conntrack_inet_error(tmpl, skb, dataoff, state, |
247 | IPPROTO_ICMP, outer_daddr: &outer_daddr); |
248 | } |
249 | |
250 | #if IS_ENABLED(CONFIG_NF_CT_NETLINK) |
251 | |
252 | #include <linux/netfilter/nfnetlink.h> |
253 | #include <linux/netfilter/nfnetlink_conntrack.h> |
254 | |
255 | static int icmp_tuple_to_nlattr(struct sk_buff *skb, |
256 | const struct nf_conntrack_tuple *t) |
257 | { |
258 | if (nla_put_be16(skb, attrtype: CTA_PROTO_ICMP_ID, value: t->src.u.icmp.id) || |
259 | nla_put_u8(skb, attrtype: CTA_PROTO_ICMP_TYPE, value: t->dst.u.icmp.type) || |
260 | nla_put_u8(skb, attrtype: CTA_PROTO_ICMP_CODE, value: t->dst.u.icmp.code)) |
261 | goto nla_put_failure; |
262 | return 0; |
263 | |
264 | nla_put_failure: |
265 | return -1; |
266 | } |
267 | |
268 | static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = { |
269 | [CTA_PROTO_ICMP_TYPE] = { .type = NLA_U8 }, |
270 | [CTA_PROTO_ICMP_CODE] = { .type = NLA_U8 }, |
271 | [CTA_PROTO_ICMP_ID] = { .type = NLA_U16 }, |
272 | }; |
273 | |
274 | static int icmp_nlattr_to_tuple(struct nlattr *tb[], |
275 | struct nf_conntrack_tuple *tuple, |
276 | u_int32_t flags) |
277 | { |
278 | if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_TYPE)) { |
279 | if (!tb[CTA_PROTO_ICMP_TYPE]) |
280 | return -EINVAL; |
281 | |
282 | tuple->dst.u.icmp.type = nla_get_u8(nla: tb[CTA_PROTO_ICMP_TYPE]); |
283 | if (tuple->dst.u.icmp.type >= sizeof(invmap) || |
284 | !invmap[tuple->dst.u.icmp.type]) |
285 | return -EINVAL; |
286 | } |
287 | |
288 | if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_CODE)) { |
289 | if (!tb[CTA_PROTO_ICMP_CODE]) |
290 | return -EINVAL; |
291 | |
292 | tuple->dst.u.icmp.code = nla_get_u8(nla: tb[CTA_PROTO_ICMP_CODE]); |
293 | } |
294 | |
295 | if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_ID)) { |
296 | if (!tb[CTA_PROTO_ICMP_ID]) |
297 | return -EINVAL; |
298 | |
299 | tuple->src.u.icmp.id = nla_get_be16(nla: tb[CTA_PROTO_ICMP_ID]); |
300 | } |
301 | |
302 | return 0; |
303 | } |
304 | |
305 | static unsigned int icmp_nlattr_tuple_size(void) |
306 | { |
307 | static unsigned int size __read_mostly; |
308 | |
309 | if (!size) |
310 | size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1); |
311 | |
312 | return size; |
313 | } |
314 | #endif |
315 | |
316 | #ifdef CONFIG_NF_CONNTRACK_TIMEOUT |
317 | |
318 | #include <linux/netfilter/nfnetlink.h> |
319 | #include <linux/netfilter/nfnetlink_cttimeout.h> |
320 | |
321 | static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[], |
322 | struct net *net, void *data) |
323 | { |
324 | unsigned int *timeout = data; |
325 | struct nf_icmp_net *in = nf_icmp_pernet(net); |
326 | |
327 | if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) { |
328 | if (!timeout) |
329 | timeout = &in->timeout; |
330 | *timeout = |
331 | ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ; |
332 | } else if (timeout) { |
333 | /* Set default ICMP timeout. */ |
334 | *timeout = in->timeout; |
335 | } |
336 | return 0; |
337 | } |
338 | |
339 | static int |
340 | icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data) |
341 | { |
342 | const unsigned int *timeout = data; |
343 | |
344 | if (nla_put_be32(skb, attrtype: CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ))) |
345 | goto nla_put_failure; |
346 | return 0; |
347 | |
348 | nla_put_failure: |
349 | return -ENOSPC; |
350 | } |
351 | |
352 | static const struct nla_policy |
353 | icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = { |
354 | [CTA_TIMEOUT_ICMP_TIMEOUT] = { .type = NLA_U32 }, |
355 | }; |
356 | #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ |
357 | |
358 | void nf_conntrack_icmp_init_net(struct net *net) |
359 | { |
360 | struct nf_icmp_net *in = nf_icmp_pernet(net); |
361 | |
362 | in->timeout = nf_ct_icmp_timeout; |
363 | } |
364 | |
365 | const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp = |
366 | { |
367 | .l4proto = IPPROTO_ICMP, |
368 | #if IS_ENABLED(CONFIG_NF_CT_NETLINK) |
369 | .tuple_to_nlattr = icmp_tuple_to_nlattr, |
370 | .nlattr_tuple_size = icmp_nlattr_tuple_size, |
371 | .nlattr_to_tuple = icmp_nlattr_to_tuple, |
372 | .nla_policy = icmp_nla_policy, |
373 | #endif |
374 | #ifdef CONFIG_NF_CONNTRACK_TIMEOUT |
375 | .ctnl_timeout = { |
376 | .nlattr_to_obj = icmp_timeout_nlattr_to_obj, |
377 | .obj_to_nlattr = icmp_timeout_obj_to_nlattr, |
378 | .nlattr_max = CTA_TIMEOUT_ICMP_MAX, |
379 | .obj_size = sizeof(unsigned int), |
380 | .nla_policy = icmp_timeout_nla_policy, |
381 | }, |
382 | #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ |
383 | }; |
384 | |