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) 2006-2012 Patrick McHardy <kaber@trash.net>
5  */
6 
7 #include <linux/types.h>
8 #include <linux/timer.h>
9 #include <linux/module.h>
10 #include <linux/udp.h>
11 #include <linux/seq_file.h>
12 #include <linux/skbuff.h>
13 #include <linux/ipv6.h>
14 #include <net/ip6_checksum.h>
15 #include <net/checksum.h>
16 
17 #include <linux/netfilter.h>
18 #include <linux/netfilter_ipv4.h>
19 #include <linux/netfilter_ipv6.h>
20 #include <net/netfilter/nf_conntrack_l4proto.h>
21 #include <net/netfilter/nf_conntrack_ecache.h>
22 #include <net/netfilter/nf_conntrack_timeout.h>
23 #include <net/netfilter/nf_log.h>
24 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
25 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
26 
27 static const unsigned int udp_timeouts[UDP_CT_MAX] = {
28 	[UDP_CT_UNREPLIED]	= 30*HZ,
29 	[UDP_CT_REPLIED]	= 120*HZ,
30 };
31 
32 static unsigned int *udp_get_timeouts(struct net *net)
33 {
34 	return nf_udp_pernet(net)->timeouts;
35 }
36 
37 static void udp_error_log(const struct sk_buff *skb,
38 			  const struct nf_hook_state *state,
39 			  const char *msg)
40 {
41 	nf_l4proto_log_invalid(skb, state, IPPROTO_UDP, "%s", msg);
42 }
43 
44 static bool udp_error(struct sk_buff *skb,
45 		      unsigned int dataoff,
46 		      const struct nf_hook_state *state)
47 {
48 	unsigned int udplen = skb->len - dataoff;
49 	const struct udphdr *hdr;
50 	struct udphdr _hdr;
51 
52 	/* Header is too small? */
53 	hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
54 	if (!hdr) {
55 		udp_error_log(skb, state, "short packet");
56 		return true;
57 	}
58 
59 	/* Truncated/malformed packets */
60 	if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
61 		udp_error_log(skb, state, "truncated/malformed packet");
62 		return true;
63 	}
64 
65 	/* Packet with no checksum */
66 	if (!hdr->check)
67 		return false;
68 
69 	/* Checksum invalid? Ignore.
70 	 * We skip checking packets on the outgoing path
71 	 * because the checksum is assumed to be correct.
72 	 * FIXME: Source route IP option packets --RR */
73 	if (state->hook == NF_INET_PRE_ROUTING &&
74 	    state->net->ct.sysctl_checksum &&
75 	    nf_checksum(skb, state->hook, dataoff, IPPROTO_UDP, state->pf)) {
76 		udp_error_log(skb, state, "bad checksum");
77 		return true;
78 	}
79 
80 	return false;
81 }
82 
83 /* Returns verdict for packet, and may modify conntracktype */
84 int nf_conntrack_udp_packet(struct nf_conn *ct,
85 			    struct sk_buff *skb,
86 			    unsigned int dataoff,
87 			    enum ip_conntrack_info ctinfo,
88 			    const struct nf_hook_state *state)
89 {
90 	unsigned int *timeouts;
91 
92 	if (udp_error(skb, dataoff, state))
93 		return -NF_ACCEPT;
94 
95 	timeouts = nf_ct_timeout_lookup(ct);
96 	if (!timeouts)
97 		timeouts = udp_get_timeouts(nf_ct_net(ct));
98 
99 	if (!nf_ct_is_confirmed(ct))
100 		ct->proto.udp.stream_ts = 2 * HZ + jiffies;
101 
102 	/* If we've seen traffic both ways, this is some kind of UDP
103 	 * stream. Set Assured.
104 	 */
105 	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
106 		unsigned long extra = timeouts[UDP_CT_UNREPLIED];
107 
108 		/* Still active after two seconds? Extend timeout. */
109 		if (time_after(jiffies, ct->proto.udp.stream_ts))
110 			extra = timeouts[UDP_CT_REPLIED];
111 
112 		nf_ct_refresh_acct(ct, ctinfo, skb, extra);
113 
114 		/* never set ASSURED for IPS_NAT_CLASH, they time out soon */
115 		if (unlikely((ct->status & IPS_NAT_CLASH)))
116 			return NF_ACCEPT;
117 
118 		/* Also, more likely to be important, and not a probe */
119 		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
120 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
121 	} else {
122 		nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
123 	}
124 	return NF_ACCEPT;
125 }
126 
127 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
128 static void udplite_error_log(const struct sk_buff *skb,
129 			      const struct nf_hook_state *state,
130 			      const char *msg)
131 {
132 	nf_l4proto_log_invalid(skb, state, IPPROTO_UDPLITE, "%s", msg);
133 }
134 
135 static bool udplite_error(struct sk_buff *skb,
136 			  unsigned int dataoff,
137 			  const struct nf_hook_state *state)
138 {
139 	unsigned int udplen = skb->len - dataoff;
140 	const struct udphdr *hdr;
141 	struct udphdr _hdr;
142 	unsigned int cscov;
143 
144 	/* Header is too small? */
145 	hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
146 	if (!hdr) {
147 		udplite_error_log(skb, state, "short packet");
148 		return true;
149 	}
150 
151 	cscov = ntohs(hdr->len);
152 	if (cscov == 0) {
153 		cscov = udplen;
154 	} else if (cscov < sizeof(*hdr) || cscov > udplen) {
155 		udplite_error_log(skb, state, "invalid checksum coverage");
156 		return true;
157 	}
158 
159 	/* UDPLITE mandates checksums */
160 	if (!hdr->check) {
161 		udplite_error_log(skb, state, "checksum missing");
162 		return true;
163 	}
164 
165 	/* Checksum invalid? Ignore. */
166 	if (state->hook == NF_INET_PRE_ROUTING &&
167 	    state->net->ct.sysctl_checksum &&
168 	    nf_checksum_partial(skb, state->hook, dataoff, cscov, IPPROTO_UDP,
169 				state->pf)) {
170 		udplite_error_log(skb, state, "bad checksum");
171 		return true;
172 	}
173 
174 	return false;
175 }
176 
177 /* Returns verdict for packet, and may modify conntracktype */
178 int nf_conntrack_udplite_packet(struct nf_conn *ct,
179 				struct sk_buff *skb,
180 				unsigned int dataoff,
181 				enum ip_conntrack_info ctinfo,
182 				const struct nf_hook_state *state)
183 {
184 	unsigned int *timeouts;
185 
186 	if (udplite_error(skb, dataoff, state))
187 		return -NF_ACCEPT;
188 
189 	timeouts = nf_ct_timeout_lookup(ct);
190 	if (!timeouts)
191 		timeouts = udp_get_timeouts(nf_ct_net(ct));
192 
193 	/* If we've seen traffic both ways, this is some kind of UDP
194 	   stream.  Extend timeout. */
195 	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
196 		nf_ct_refresh_acct(ct, ctinfo, skb,
197 				   timeouts[UDP_CT_REPLIED]);
198 
199 		if (unlikely((ct->status & IPS_NAT_CLASH)))
200 			return NF_ACCEPT;
201 
202 		/* Also, more likely to be important, and not a probe */
203 		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
204 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
205 	} else {
206 		nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
207 	}
208 	return NF_ACCEPT;
209 }
210 #endif
211 
212 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
213 
214 #include <linux/netfilter/nfnetlink.h>
215 #include <linux/netfilter/nfnetlink_cttimeout.h>
216 
217 static int udp_timeout_nlattr_to_obj(struct nlattr *tb[],
218 				     struct net *net, void *data)
219 {
220 	unsigned int *timeouts = data;
221 	struct nf_udp_net *un = nf_udp_pernet(net);
222 
223 	if (!timeouts)
224 		timeouts = un->timeouts;
225 
226 	/* set default timeouts for UDP. */
227 	timeouts[UDP_CT_UNREPLIED] = un->timeouts[UDP_CT_UNREPLIED];
228 	timeouts[UDP_CT_REPLIED] = un->timeouts[UDP_CT_REPLIED];
229 
230 	if (tb[CTA_TIMEOUT_UDP_UNREPLIED]) {
231 		timeouts[UDP_CT_UNREPLIED] =
232 			ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_UNREPLIED])) * HZ;
233 	}
234 	if (tb[CTA_TIMEOUT_UDP_REPLIED]) {
235 		timeouts[UDP_CT_REPLIED] =
236 			ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_REPLIED])) * HZ;
237 	}
238 	return 0;
239 }
240 
241 static int
242 udp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
243 {
244 	const unsigned int *timeouts = data;
245 
246 	if (nla_put_be32(skb, CTA_TIMEOUT_UDP_UNREPLIED,
247 			 htonl(timeouts[UDP_CT_UNREPLIED] / HZ)) ||
248 	    nla_put_be32(skb, CTA_TIMEOUT_UDP_REPLIED,
249 			 htonl(timeouts[UDP_CT_REPLIED] / HZ)))
250 		goto nla_put_failure;
251 	return 0;
252 
253 nla_put_failure:
254 	return -ENOSPC;
255 }
256 
257 static const struct nla_policy
258 udp_timeout_nla_policy[CTA_TIMEOUT_UDP_MAX+1] = {
259        [CTA_TIMEOUT_UDP_UNREPLIED]	= { .type = NLA_U32 },
260        [CTA_TIMEOUT_UDP_REPLIED]	= { .type = NLA_U32 },
261 };
262 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
263 
264 void nf_conntrack_udp_init_net(struct net *net)
265 {
266 	struct nf_udp_net *un = nf_udp_pernet(net);
267 	int i;
268 
269 	for (i = 0; i < UDP_CT_MAX; i++)
270 		un->timeouts[i] = udp_timeouts[i];
271 
272 #if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
273 	un->offload_timeout = 30 * HZ;
274 	un->offload_pickup = 30 * HZ;
275 #endif
276 }
277 
278 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udp =
279 {
280 	.l4proto		= IPPROTO_UDP,
281 	.allow_clash		= true,
282 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
283 	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
284 	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,
285 	.nlattr_tuple_size	= nf_ct_port_nlattr_tuple_size,
286 	.nla_policy		= nf_ct_port_nla_policy,
287 #endif
288 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
289 	.ctnl_timeout		= {
290 		.nlattr_to_obj	= udp_timeout_nlattr_to_obj,
291 		.obj_to_nlattr	= udp_timeout_obj_to_nlattr,
292 		.nlattr_max	= CTA_TIMEOUT_UDP_MAX,
293 		.obj_size	= sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
294 		.nla_policy	= udp_timeout_nla_policy,
295 	},
296 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
297 };
298 
299 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
300 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udplite =
301 {
302 	.l4proto		= IPPROTO_UDPLITE,
303 	.allow_clash		= true,
304 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
305 	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
306 	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,
307 	.nlattr_tuple_size	= nf_ct_port_nlattr_tuple_size,
308 	.nla_policy		= nf_ct_port_nla_policy,
309 #endif
310 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
311 	.ctnl_timeout		= {
312 		.nlattr_to_obj	= udp_timeout_nlattr_to_obj,
313 		.obj_to_nlattr	= udp_timeout_obj_to_nlattr,
314 		.nlattr_max	= CTA_TIMEOUT_UDP_MAX,
315 		.obj_size	= sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
316 		.nla_policy	= udp_timeout_nla_policy,
317 	},
318 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
319 };
320 #endif
321