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
icmp_pkt_to_tuple(const struct sk_buff * skb,unsigned int dataoff,struct net * net,struct nf_conntrack_tuple * tuple)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, dataoff, sizeof(_hdr), &_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
nf_conntrack_invert_icmp_tuple(struct nf_conntrack_tuple * tuple,const struct nf_conntrack_tuple * orig)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. */
nf_conntrack_icmp_packet(struct nf_conn * ct,struct sk_buff * skb,enum ip_conntrack_info ctinfo,const struct nf_hook_state * state)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(&ct->tuplehash[0].tuple);
95 return -NF_ACCEPT;
96 }
97
98 if (!timeout)
99 timeout = &nf_icmp_pernet(nf_ct_net(ct))->timeout;
100
101 nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
102 return NF_ACCEPT;
103 }
104
105 /* Check inner header is related to any of the existing connections */
nf_conntrack_inet_error(struct nf_conn * tmpl,struct sk_buff * skb,unsigned int dataoff,const struct nf_hook_state * state,u8 l4proto,union nf_inet_addr * outer_daddr)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);
122
123 /* Are they talking about one of our connections? */
124 if (!nf_ct_get_tuplepr(skb, dataoff,
125 state->pf, state->net, &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(&innertuple, &origtuple))
131 return -NF_ACCEPT;
132
133 h = nf_conntrack_find_get(state->net, zone, &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(h);
169 dir = NF_CT_DIRECTION(h);
170 ct_daddr = &ct->tuplehash[dir].tuple.dst.u3;
171 if (!nf_inet_addr_cmp(outer_daddr, ct_daddr)) {
172 if (state->pf == AF_INET) {
173 nf_l4proto_log_invalid(skb, state->net, state->pf,
174 l4proto,
175 "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->net, state->pf,
179 l4proto,
180 "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, ctinfo);
193 return NF_ACCEPT;
194 }
195
icmp_error_log(const struct sk_buff * skb,const struct nf_hook_state * state,const char * msg)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->net, state->pf,
201 IPPROTO_ICMP, "%s", msg);
202 }
203
204 /* Small and modified version of icmp_rcv */
nf_conntrack_icmpv4_error(struct nf_conn * tmpl,struct sk_buff * skb,unsigned int dataoff,const struct nf_hook_state * state)205 int nf_conntrack_icmpv4_error(struct nf_conn *tmpl,
206 struct sk_buff *skb, unsigned int dataoff,
207 const struct nf_hook_state *state)
208 {
209 union nf_inet_addr outer_daddr;
210 const struct icmphdr *icmph;
211 struct icmphdr _ih;
212
213 /* Not enough header? */
214 icmph = skb_header_pointer(skb, dataoff, sizeof(_ih), &_ih);
215 if (icmph == NULL) {
216 icmp_error_log(skb, state, "short packet");
217 return -NF_ACCEPT;
218 }
219
220 /* See nf_conntrack_proto_tcp.c */
221 if (state->net->ct.sysctl_checksum &&
222 state->hook == NF_INET_PRE_ROUTING &&
223 nf_ip_checksum(skb, state->hook, dataoff, IPPROTO_ICMP)) {
224 icmp_error_log(skb, state, "bad hw icmp checksum");
225 return -NF_ACCEPT;
226 }
227
228 /*
229 * 18 is the highest 'known' ICMP type. Anything else is a mystery
230 *
231 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
232 * discarded.
233 */
234 if (icmph->type > NR_ICMP_TYPES) {
235 icmp_error_log(skb, state, "invalid icmp type");
236 return -NF_ACCEPT;
237 }
238
239 /* Need to track icmp error message? */
240 if (!icmp_is_err(icmph->type))
241 return NF_ACCEPT;
242
243 memset(&outer_daddr, 0, sizeof(outer_daddr));
244 outer_daddr.ip = ip_hdr(skb)->daddr;
245
246 dataoff += sizeof(*icmph);
247 return nf_conntrack_inet_error(tmpl, skb, dataoff, state,
248 IPPROTO_ICMP, &outer_daddr);
249 }
250
251 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
252
253 #include <linux/netfilter/nfnetlink.h>
254 #include <linux/netfilter/nfnetlink_conntrack.h>
255
icmp_tuple_to_nlattr(struct sk_buff * skb,const struct nf_conntrack_tuple * t)256 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
257 const struct nf_conntrack_tuple *t)
258 {
259 if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
260 nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
261 nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code))
262 goto nla_put_failure;
263 return 0;
264
265 nla_put_failure:
266 return -1;
267 }
268
269 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
270 [CTA_PROTO_ICMP_TYPE] = { .type = NLA_U8 },
271 [CTA_PROTO_ICMP_CODE] = { .type = NLA_U8 },
272 [CTA_PROTO_ICMP_ID] = { .type = NLA_U16 },
273 };
274
icmp_nlattr_to_tuple(struct nlattr * tb[],struct nf_conntrack_tuple * tuple,u_int32_t flags)275 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
276 struct nf_conntrack_tuple *tuple,
277 u_int32_t flags)
278 {
279 if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_TYPE)) {
280 if (!tb[CTA_PROTO_ICMP_TYPE])
281 return -EINVAL;
282
283 tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
284 if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
285 !invmap[tuple->dst.u.icmp.type])
286 return -EINVAL;
287 }
288
289 if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_CODE)) {
290 if (!tb[CTA_PROTO_ICMP_CODE])
291 return -EINVAL;
292
293 tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
294 }
295
296 if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_ID)) {
297 if (!tb[CTA_PROTO_ICMP_ID])
298 return -EINVAL;
299
300 tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
301 }
302
303 return 0;
304 }
305
icmp_nlattr_tuple_size(void)306 static unsigned int icmp_nlattr_tuple_size(void)
307 {
308 static unsigned int size __read_mostly;
309
310 if (!size)
311 size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
312
313 return size;
314 }
315 #endif
316
317 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
318
319 #include <linux/netfilter/nfnetlink.h>
320 #include <linux/netfilter/nfnetlink_cttimeout.h>
321
icmp_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)322 static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
323 struct net *net, void *data)
324 {
325 unsigned int *timeout = data;
326 struct nf_icmp_net *in = nf_icmp_pernet(net);
327
328 if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
329 if (!timeout)
330 timeout = &in->timeout;
331 *timeout =
332 ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
333 } else if (timeout) {
334 /* Set default ICMP timeout. */
335 *timeout = in->timeout;
336 }
337 return 0;
338 }
339
340 static int
icmp_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)341 icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
342 {
343 const unsigned int *timeout = data;
344
345 if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
346 goto nla_put_failure;
347 return 0;
348
349 nla_put_failure:
350 return -ENOSPC;
351 }
352
353 static const struct nla_policy
354 icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
355 [CTA_TIMEOUT_ICMP_TIMEOUT] = { .type = NLA_U32 },
356 };
357 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
358
nf_conntrack_icmp_init_net(struct net * net)359 void nf_conntrack_icmp_init_net(struct net *net)
360 {
361 struct nf_icmp_net *in = nf_icmp_pernet(net);
362
363 in->timeout = nf_ct_icmp_timeout;
364 }
365
366 const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
367 {
368 .l4proto = IPPROTO_ICMP,
369 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
370 .tuple_to_nlattr = icmp_tuple_to_nlattr,
371 .nlattr_tuple_size = icmp_nlattr_tuple_size,
372 .nlattr_to_tuple = icmp_nlattr_to_tuple,
373 .nla_policy = icmp_nla_policy,
374 #endif
375 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
376 .ctnl_timeout = {
377 .nlattr_to_obj = icmp_timeout_nlattr_to_obj,
378 .obj_to_nlattr = icmp_timeout_obj_to_nlattr,
379 .nlattr_max = CTA_TIMEOUT_ICMP_MAX,
380 .obj_size = sizeof(unsigned int),
381 .nla_policy = icmp_timeout_nla_policy,
382 },
383 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
384 };
385