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,
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,
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, IPPROTO_ICMP, "%s", msg);
201 }
202
203 /* 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)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, dataoff, sizeof(_ih), &_ih);
214 if (icmph == NULL) {
215 icmp_error_log(skb, state, "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, state->hook, dataoff, IPPROTO_ICMP)) {
223 icmp_error_log(skb, state, "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, "invalid icmp type");
235 return -NF_ACCEPT;
236 }
237
238 /* Need to track icmp error message? */
239 if (!icmp_is_err(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);
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
icmp_tuple_to_nlattr(struct sk_buff * skb,const struct nf_conntrack_tuple * t)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, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
259 nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
260 nla_put_u8(skb, CTA_PROTO_ICMP_CODE, 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
icmp_nlattr_to_tuple(struct nlattr * tb[],struct nf_conntrack_tuple * tuple,u_int32_t flags)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(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(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(tb[CTA_PROTO_ICMP_ID]);
300 }
301
302 return 0;
303 }
304
icmp_nlattr_tuple_size(void)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
icmp_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)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
icmp_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)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, 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
nf_conntrack_icmp_init_net(struct net * net)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