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 
udp_get_timeouts(struct net * net)32 static unsigned int *udp_get_timeouts(struct net *net)
33 {
34 	return nf_udp_pernet(net)->timeouts;
35 }
36 
udp_error_log(const struct sk_buff * skb,const struct nf_hook_state * state,const char * msg)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 
udp_error(struct sk_buff * skb,unsigned int dataoff,const struct nf_hook_state * state)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 */
nf_conntrack_udp_packet(struct nf_conn * ct,struct sk_buff * skb,unsigned int dataoff,enum ip_conntrack_info ctinfo,const struct nf_hook_state * state)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 	unsigned long status;
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 	status = READ_ONCE(ct->status);
101 	if ((status & IPS_CONFIRMED) == 0)
102 		ct->proto.udp.stream_ts = 2 * HZ + jiffies;
103 
104 	/* If we've seen traffic both ways, this is some kind of UDP
105 	 * stream. Set Assured.
106 	 */
107 	if (status & IPS_SEEN_REPLY) {
108 		unsigned long extra = timeouts[UDP_CT_UNREPLIED];
109 		bool stream = false;
110 
111 		/* Still active after two seconds? Extend timeout. */
112 		if (time_after(jiffies, ct->proto.udp.stream_ts)) {
113 			extra = timeouts[UDP_CT_REPLIED];
114 			stream = (status & IPS_ASSURED) == 0;
115 		}
116 
117 		nf_ct_refresh_acct(ct, ctinfo, skb, extra);
118 
119 		/* never set ASSURED for IPS_NAT_CLASH, they time out soon */
120 		if (unlikely((status & IPS_NAT_CLASH)))
121 			return NF_ACCEPT;
122 
123 		/* Also, more likely to be important, and not a probe */
124 		if (stream && !test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
125 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
126 	} else {
127 		nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
128 	}
129 	return NF_ACCEPT;
130 }
131 
132 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
udplite_error_log(const struct sk_buff * skb,const struct nf_hook_state * state,const char * msg)133 static void udplite_error_log(const struct sk_buff *skb,
134 			      const struct nf_hook_state *state,
135 			      const char *msg)
136 {
137 	nf_l4proto_log_invalid(skb, state, IPPROTO_UDPLITE, "%s", msg);
138 }
139 
udplite_error(struct sk_buff * skb,unsigned int dataoff,const struct nf_hook_state * state)140 static bool udplite_error(struct sk_buff *skb,
141 			  unsigned int dataoff,
142 			  const struct nf_hook_state *state)
143 {
144 	unsigned int udplen = skb->len - dataoff;
145 	const struct udphdr *hdr;
146 	struct udphdr _hdr;
147 	unsigned int cscov;
148 
149 	/* Header is too small? */
150 	hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
151 	if (!hdr) {
152 		udplite_error_log(skb, state, "short packet");
153 		return true;
154 	}
155 
156 	cscov = ntohs(hdr->len);
157 	if (cscov == 0) {
158 		cscov = udplen;
159 	} else if (cscov < sizeof(*hdr) || cscov > udplen) {
160 		udplite_error_log(skb, state, "invalid checksum coverage");
161 		return true;
162 	}
163 
164 	/* UDPLITE mandates checksums */
165 	if (!hdr->check) {
166 		udplite_error_log(skb, state, "checksum missing");
167 		return true;
168 	}
169 
170 	/* Checksum invalid? Ignore. */
171 	if (state->hook == NF_INET_PRE_ROUTING &&
172 	    state->net->ct.sysctl_checksum &&
173 	    nf_checksum_partial(skb, state->hook, dataoff, cscov, IPPROTO_UDP,
174 				state->pf)) {
175 		udplite_error_log(skb, state, "bad checksum");
176 		return true;
177 	}
178 
179 	return false;
180 }
181 
182 /* Returns verdict for packet, and may modify conntracktype */
nf_conntrack_udplite_packet(struct nf_conn * ct,struct sk_buff * skb,unsigned int dataoff,enum ip_conntrack_info ctinfo,const struct nf_hook_state * state)183 int nf_conntrack_udplite_packet(struct nf_conn *ct,
184 				struct sk_buff *skb,
185 				unsigned int dataoff,
186 				enum ip_conntrack_info ctinfo,
187 				const struct nf_hook_state *state)
188 {
189 	unsigned int *timeouts;
190 
191 	if (udplite_error(skb, dataoff, state))
192 		return -NF_ACCEPT;
193 
194 	timeouts = nf_ct_timeout_lookup(ct);
195 	if (!timeouts)
196 		timeouts = udp_get_timeouts(nf_ct_net(ct));
197 
198 	/* If we've seen traffic both ways, this is some kind of UDP
199 	   stream.  Extend timeout. */
200 	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
201 		nf_ct_refresh_acct(ct, ctinfo, skb,
202 				   timeouts[UDP_CT_REPLIED]);
203 
204 		if (unlikely((ct->status & IPS_NAT_CLASH)))
205 			return NF_ACCEPT;
206 
207 		/* Also, more likely to be important, and not a probe */
208 		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
209 			nf_conntrack_event_cache(IPCT_ASSURED, ct);
210 	} else {
211 		nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
212 	}
213 	return NF_ACCEPT;
214 }
215 #endif
216 
217 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
218 
219 #include <linux/netfilter/nfnetlink.h>
220 #include <linux/netfilter/nfnetlink_cttimeout.h>
221 
udp_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)222 static int udp_timeout_nlattr_to_obj(struct nlattr *tb[],
223 				     struct net *net, void *data)
224 {
225 	unsigned int *timeouts = data;
226 	struct nf_udp_net *un = nf_udp_pernet(net);
227 
228 	if (!timeouts)
229 		timeouts = un->timeouts;
230 
231 	/* set default timeouts for UDP. */
232 	timeouts[UDP_CT_UNREPLIED] = un->timeouts[UDP_CT_UNREPLIED];
233 	timeouts[UDP_CT_REPLIED] = un->timeouts[UDP_CT_REPLIED];
234 
235 	if (tb[CTA_TIMEOUT_UDP_UNREPLIED]) {
236 		timeouts[UDP_CT_UNREPLIED] =
237 			ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_UNREPLIED])) * HZ;
238 	}
239 	if (tb[CTA_TIMEOUT_UDP_REPLIED]) {
240 		timeouts[UDP_CT_REPLIED] =
241 			ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_REPLIED])) * HZ;
242 	}
243 	return 0;
244 }
245 
246 static int
udp_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)247 udp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
248 {
249 	const unsigned int *timeouts = data;
250 
251 	if (nla_put_be32(skb, CTA_TIMEOUT_UDP_UNREPLIED,
252 			 htonl(timeouts[UDP_CT_UNREPLIED] / HZ)) ||
253 	    nla_put_be32(skb, CTA_TIMEOUT_UDP_REPLIED,
254 			 htonl(timeouts[UDP_CT_REPLIED] / HZ)))
255 		goto nla_put_failure;
256 	return 0;
257 
258 nla_put_failure:
259 	return -ENOSPC;
260 }
261 
262 static const struct nla_policy
263 udp_timeout_nla_policy[CTA_TIMEOUT_UDP_MAX+1] = {
264        [CTA_TIMEOUT_UDP_UNREPLIED]	= { .type = NLA_U32 },
265        [CTA_TIMEOUT_UDP_REPLIED]	= { .type = NLA_U32 },
266 };
267 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
268 
nf_conntrack_udp_init_net(struct net * net)269 void nf_conntrack_udp_init_net(struct net *net)
270 {
271 	struct nf_udp_net *un = nf_udp_pernet(net);
272 	int i;
273 
274 	for (i = 0; i < UDP_CT_MAX; i++)
275 		un->timeouts[i] = udp_timeouts[i];
276 
277 #if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
278 	un->offload_timeout = 30 * HZ;
279 #endif
280 }
281 
282 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udp =
283 {
284 	.l4proto		= IPPROTO_UDP,
285 	.allow_clash		= true,
286 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
287 	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
288 	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,
289 	.nlattr_tuple_size	= nf_ct_port_nlattr_tuple_size,
290 	.nla_policy		= nf_ct_port_nla_policy,
291 #endif
292 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
293 	.ctnl_timeout		= {
294 		.nlattr_to_obj	= udp_timeout_nlattr_to_obj,
295 		.obj_to_nlattr	= udp_timeout_obj_to_nlattr,
296 		.nlattr_max	= CTA_TIMEOUT_UDP_MAX,
297 		.obj_size	= sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
298 		.nla_policy	= udp_timeout_nla_policy,
299 	},
300 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
301 };
302 
303 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
304 const struct nf_conntrack_l4proto nf_conntrack_l4proto_udplite =
305 {
306 	.l4proto		= IPPROTO_UDPLITE,
307 	.allow_clash		= true,
308 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
309 	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
310 	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,
311 	.nlattr_tuple_size	= nf_ct_port_nlattr_tuple_size,
312 	.nla_policy		= nf_ct_port_nla_policy,
313 #endif
314 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
315 	.ctnl_timeout		= {
316 		.nlattr_to_obj	= udp_timeout_nlattr_to_obj,
317 		.obj_to_nlattr	= udp_timeout_obj_to_nlattr,
318 		.nlattr_max	= CTA_TIMEOUT_UDP_MAX,
319 		.obj_size	= sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
320 		.nla_policy	= udp_timeout_nla_policy,
321 	},
322 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
323 };
324 #endif
325