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->net, state->pf,
42 			       IPPROTO_UDP, "%s", msg);
43 }
44 
45 static bool udp_error(struct sk_buff *skb,
46 		      unsigned int dataoff,
47 		      const struct nf_hook_state *state)
48 {
49 	unsigned int udplen = skb->len - dataoff;
50 	const struct udphdr *hdr;
51 	struct udphdr _hdr;
52 
53 	/* Header is too small? */
54 	hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
55 	if (!hdr) {
56 		udp_error_log(skb, state, "short packet");
57 		return true;
58 	}
59 
60 	/* Truncated/malformed packets */
61 	if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
62 		udp_error_log(skb, state, "truncated/malformed packet");
63 		return true;
64 	}
65 
66 	/* Packet with no checksum */
67 	if (!hdr->check)
68 		return false;
69 
70 	/* Checksum invalid? Ignore.
71 	 * We skip checking packets on the outgoing path
72 	 * because the checksum is assumed to be correct.
73 	 * FIXME: Source route IP option packets --RR */
74 	if (state->hook == NF_INET_PRE_ROUTING &&
75 	    state->net->ct.sysctl_checksum &&
76 	    nf_checksum(skb, state->hook, dataoff, IPPROTO_UDP, state->pf)) {
77 		udp_error_log(skb, state, "bad checksum");
78 		return true;
79 	}
80 
81 	return false;
82 }
83 
84 /* Returns verdict for packet, and may modify conntracktype */
85 int nf_conntrack_udp_packet(struct nf_conn *ct,
86 			    struct sk_buff *skb,
87 			    unsigned int dataoff,
88 			    enum ip_conntrack_info ctinfo,
89 			    const struct nf_hook_state *state)
90 {
91 	unsigned int *timeouts;
92 
93 	if (udp_error(skb, dataoff, state))
94 		return -NF_ACCEPT;
95 
96 	timeouts = nf_ct_timeout_lookup(ct);
97 	if (!timeouts)
98 		timeouts = udp_get_timeouts(nf_ct_net(ct));
99 
100 	if (!nf_ct_is_confirmed(ct))
101 		ct->proto.udp.stream_ts = 2 * HZ + jiffies;
102 
103 	/* If we've seen traffic both ways, this is some kind of UDP
104 	 * stream. Set Assured.
105 	 */
106 	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
107 		unsigned long extra = timeouts[UDP_CT_UNREPLIED];
108 
109 		/* Still active after two seconds? Extend timeout. */
110 		if (time_after(jiffies, ct->proto.udp.stream_ts))
111 			extra = timeouts[UDP_CT_REPLIED];
112 
113 		nf_ct_refresh_acct(ct, ctinfo, skb, extra);
114 
115 		/* Also, more likely to be important, and not a probe */
116 		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
117 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
118 	} else {
119 		nf_ct_refresh_acct(ct, ctinfo, skb,
120 				   timeouts[UDP_CT_UNREPLIED]);
121 	}
122 	return NF_ACCEPT;
123 }
124 
125 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
126 static void udplite_error_log(const struct sk_buff *skb,
127 			      const struct nf_hook_state *state,
128 			      const char *msg)
129 {
130 	nf_l4proto_log_invalid(skb, state->net, state->pf,
131 			       IPPROTO_UDPLITE, "%s", msg);
132 }
133 
134 static bool udplite_error(struct sk_buff *skb,
135 			  unsigned int dataoff,
136 			  const struct nf_hook_state *state)
137 {
138 	unsigned int udplen = skb->len - dataoff;
139 	const struct udphdr *hdr;
140 	struct udphdr _hdr;
141 	unsigned int cscov;
142 
143 	/* Header is too small? */
144 	hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
145 	if (!hdr) {
146 		udplite_error_log(skb, state, "short packet");
147 		return true;
148 	}
149 
150 	cscov = ntohs(hdr->len);
151 	if (cscov == 0) {
152 		cscov = udplen;
153 	} else if (cscov < sizeof(*hdr) || cscov > udplen) {
154 		udplite_error_log(skb, state, "invalid checksum coverage");
155 		return true;
156 	}
157 
158 	/* UDPLITE mandates checksums */
159 	if (!hdr->check) {
160 		udplite_error_log(skb, state, "checksum missing");
161 		return true;
162 	}
163 
164 	/* Checksum invalid? Ignore. */
165 	if (state->hook == NF_INET_PRE_ROUTING &&
166 	    state->net->ct.sysctl_checksum &&
167 	    nf_checksum_partial(skb, state->hook, dataoff, cscov, IPPROTO_UDP,
168 				state->pf)) {
169 		udplite_error_log(skb, state, "bad checksum");
170 		return true;
171 	}
172 
173 	return false;
174 }
175 
176 /* Returns verdict for packet, and may modify conntracktype */
177 int nf_conntrack_udplite_packet(struct nf_conn *ct,
178 				struct sk_buff *skb,
179 				unsigned int dataoff,
180 				enum ip_conntrack_info ctinfo,
181 				const struct nf_hook_state *state)
182 {
183 	unsigned int *timeouts;
184 
185 	if (udplite_error(skb, dataoff, state))
186 		return -NF_ACCEPT;
187 
188 	timeouts = nf_ct_timeout_lookup(ct);
189 	if (!timeouts)
190 		timeouts = udp_get_timeouts(nf_ct_net(ct));
191 
192 	/* If we've seen traffic both ways, this is some kind of UDP
193 	   stream.  Extend timeout. */
194 	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
195 		nf_ct_refresh_acct(ct, ctinfo, skb,
196 				   timeouts[UDP_CT_REPLIED]);
197 		/* Also, more likely to be important, and not a probe */
198 		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
199 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
200 	} else {
201 		nf_ct_refresh_acct(ct, ctinfo, skb,
202 				   timeouts[UDP_CT_UNREPLIED]);
203 	}
204 	return NF_ACCEPT;
205 }
206 #endif
207 
208 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
209 
210 #include <linux/netfilter/nfnetlink.h>
211 #include <linux/netfilter/nfnetlink_cttimeout.h>
212 
213 static int udp_timeout_nlattr_to_obj(struct nlattr *tb[],
214 				     struct net *net, void *data)
215 {
216 	unsigned int *timeouts = data;
217 	struct nf_udp_net *un = nf_udp_pernet(net);
218 
219 	if (!timeouts)
220 		timeouts = un->timeouts;
221 
222 	/* set default timeouts for UDP. */
223 	timeouts[UDP_CT_UNREPLIED] = un->timeouts[UDP_CT_UNREPLIED];
224 	timeouts[UDP_CT_REPLIED] = un->timeouts[UDP_CT_REPLIED];
225 
226 	if (tb[CTA_TIMEOUT_UDP_UNREPLIED]) {
227 		timeouts[UDP_CT_UNREPLIED] =
228 			ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_UNREPLIED])) * HZ;
229 	}
230 	if (tb[CTA_TIMEOUT_UDP_REPLIED]) {
231 		timeouts[UDP_CT_REPLIED] =
232 			ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_REPLIED])) * HZ;
233 	}
234 	return 0;
235 }
236 
237 static int
238 udp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
239 {
240 	const unsigned int *timeouts = data;
241 
242 	if (nla_put_be32(skb, CTA_TIMEOUT_UDP_UNREPLIED,
243 			 htonl(timeouts[UDP_CT_UNREPLIED] / HZ)) ||
244 	    nla_put_be32(skb, CTA_TIMEOUT_UDP_REPLIED,
245 			 htonl(timeouts[UDP_CT_REPLIED] / HZ)))
246 		goto nla_put_failure;
247 	return 0;
248 
249 nla_put_failure:
250 	return -ENOSPC;
251 }
252 
253 static const struct nla_policy
254 udp_timeout_nla_policy[CTA_TIMEOUT_UDP_MAX+1] = {
255        [CTA_TIMEOUT_UDP_UNREPLIED]	= { .type = NLA_U32 },
256        [CTA_TIMEOUT_UDP_REPLIED]	= { .type = NLA_U32 },
257 };
258 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
259 
260 void nf_conntrack_udp_init_net(struct net *net)
261 {
262 	struct nf_udp_net *un = nf_udp_pernet(net);
263 	int i;
264 
265 	for (i = 0; i < UDP_CT_MAX; i++)
266 		un->timeouts[i] = udp_timeouts[i];
267 }
268 
269 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udp =
270 {
271 	.l4proto		= IPPROTO_UDP,
272 	.allow_clash		= true,
273 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
274 	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
275 	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,
276 	.nlattr_tuple_size	= nf_ct_port_nlattr_tuple_size,
277 	.nla_policy		= nf_ct_port_nla_policy,
278 #endif
279 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
280 	.ctnl_timeout		= {
281 		.nlattr_to_obj	= udp_timeout_nlattr_to_obj,
282 		.obj_to_nlattr	= udp_timeout_obj_to_nlattr,
283 		.nlattr_max	= CTA_TIMEOUT_UDP_MAX,
284 		.obj_size	= sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
285 		.nla_policy	= udp_timeout_nla_policy,
286 	},
287 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
288 };
289 
290 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
291 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udplite =
292 {
293 	.l4proto		= IPPROTO_UDPLITE,
294 	.allow_clash		= true,
295 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
296 	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
297 	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,
298 	.nlattr_tuple_size	= nf_ct_port_nlattr_tuple_size,
299 	.nla_policy		= nf_ct_port_nla_policy,
300 #endif
301 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
302 	.ctnl_timeout		= {
303 		.nlattr_to_obj	= udp_timeout_nlattr_to_obj,
304 		.obj_to_nlattr	= udp_timeout_obj_to_nlattr,
305 		.nlattr_max	= CTA_TIMEOUT_UDP_MAX,
306 		.obj_size	= sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
307 		.nla_policy	= udp_timeout_nla_policy,
308 	},
309 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
310 };
311 #endif
312