1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Connection tracking protocol helper module for GRE.
4 *
5 * GRE is a generic encapsulation protocol, which is generally not very
6 * suited for NAT, as it has no protocol-specific part as port numbers.
7 *
8 * It has an optional key field, which may help us distinguishing two
9 * connections between the same two hosts.
10 *
11 * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
12 *
13 * PPTP is built on top of a modified version of GRE, and has a mandatory
14 * field called "CallID", which serves us for the same purpose as the key
15 * field in plain GRE.
16 *
17 * Documentation about PPTP can be found in RFC 2637
18 *
19 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
20 *
21 * Development of this code funded by Astaro AG (http://www.astaro.com/)
22 *
23 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
24 */
25
26 #include <linux/module.h>
27 #include <linux/types.h>
28 #include <linux/timer.h>
29 #include <linux/list.h>
30 #include <linux/seq_file.h>
31 #include <linux/in.h>
32 #include <linux/netdevice.h>
33 #include <linux/skbuff.h>
34 #include <linux/slab.h>
35 #include <net/dst.h>
36 #include <net/gre.h>
37 #include <net/net_namespace.h>
38 #include <net/netns/generic.h>
39 #include <net/netfilter/nf_conntrack_l4proto.h>
40 #include <net/netfilter/nf_conntrack_helper.h>
41 #include <net/netfilter/nf_conntrack_core.h>
42 #include <net/netfilter/nf_conntrack_timeout.h>
43 #include <net/pptp.h>
44 #include <linux/netfilter/nf_conntrack_proto_gre.h>
45 #include <linux/netfilter/nf_conntrack_pptp.h>
46
47 static const unsigned int gre_timeouts[GRE_CT_MAX] = {
48 [GRE_CT_UNREPLIED] = 30*HZ,
49 [GRE_CT_REPLIED] = 180*HZ,
50 };
51
52 /* used when expectation is added */
53 static DEFINE_SPINLOCK(keymap_lock);
54
gre_pernet(struct net * net)55 static inline struct nf_gre_net *gre_pernet(struct net *net)
56 {
57 return &net->ct.nf_ct_proto.gre;
58 }
59
gre_key_cmpfn(const struct nf_ct_gre_keymap * km,const struct nf_conntrack_tuple * t)60 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
61 const struct nf_conntrack_tuple *t)
62 {
63 return km->tuple.src.l3num == t->src.l3num &&
64 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
65 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
66 km->tuple.dst.protonum == t->dst.protonum &&
67 km->tuple.dst.u.all == t->dst.u.all;
68 }
69
70 /* look up the source key for a given tuple */
gre_keymap_lookup(struct net * net,struct nf_conntrack_tuple * t)71 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
72 {
73 struct nf_gre_net *net_gre = gre_pernet(net);
74 struct nf_ct_gre_keymap *km;
75 __be16 key = 0;
76
77 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
78 if (gre_key_cmpfn(km, t)) {
79 key = km->tuple.src.u.gre.key;
80 break;
81 }
82 }
83
84 pr_debug("lookup src key 0x%x for ", key);
85 nf_ct_dump_tuple(t);
86
87 return key;
88 }
89
90 enum nf_ct_gre_km_act {
91 NF_CT_GRE_KM_NEW,
92 NF_CT_GRE_KM_BAD,
93 NF_CT_GRE_KM_DUP
94 };
95
96 static enum nf_ct_gre_km_act
nf_ct_gre_km_acceptable(const struct nf_ct_pptp_master * ct_pptp_info,const struct nf_conntrack_tuple * orig,const struct nf_conntrack_tuple * repl)97 nf_ct_gre_km_acceptable(const struct nf_ct_pptp_master *ct_pptp_info,
98 const struct nf_conntrack_tuple *orig,
99 const struct nf_conntrack_tuple *repl)
100 {
101 struct nf_ct_gre_keymap *km_orig, *km_repl;
102
103 lockdep_assert_held(&keymap_lock);
104
105 km_orig = ct_pptp_info->keymap[IP_CT_DIR_ORIGINAL];
106 km_repl = ct_pptp_info->keymap[IP_CT_DIR_REPLY];
107
108 if (km_orig && km_repl) {
109 if (!gre_key_cmpfn(km_orig, orig))
110 return NF_CT_GRE_KM_BAD;
111
112 if (!gre_key_cmpfn(km_repl, repl))
113 return NF_CT_GRE_KM_BAD;
114
115 return NF_CT_GRE_KM_DUP;
116 }
117
118 DEBUG_NET_WARN_ON_ONCE(km_orig);
119 DEBUG_NET_WARN_ON_ONCE(km_repl);
120 return NF_CT_GRE_KM_NEW;
121 }
122
123 /* add keymap entries, associate with specified master ct */
nf_ct_gre_keymap_add(struct nf_conn * ct,const struct nf_conntrack_tuple * orig,const struct nf_conntrack_tuple * repl)124 bool nf_ct_gre_keymap_add(struct nf_conn *ct,
125 const struct nf_conntrack_tuple *orig,
126 const struct nf_conntrack_tuple *repl)
127 {
128 struct net *net = nf_ct_net(ct);
129 struct nf_gre_net *net_gre = gre_pernet(net);
130 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
131 struct nf_ct_gre_keymap *km_orig, *km_repl;
132 bool ret = false;
133
134 km_orig = kmalloc_obj(*km_orig, GFP_ATOMIC);
135 if (!km_orig)
136 return false;
137 km_repl = kmalloc_obj(*km_repl, GFP_ATOMIC);
138 if (!km_repl)
139 goto km_free;
140
141 memcpy(&km_orig->tuple, orig, sizeof(*orig));
142 memcpy(&km_repl->tuple, repl, sizeof(*repl));
143
144 spin_lock_bh(&keymap_lock);
145 if (nf_ct_is_dying(ct))
146 goto unlock_free;
147
148 switch (nf_ct_gre_km_acceptable(ct_pptp_info, orig, repl)) {
149 case NF_CT_GRE_KM_NEW:
150 break;
151 case NF_CT_GRE_KM_DUP:
152 ret = true;
153 goto unlock_free;
154 case NF_CT_GRE_KM_BAD:
155 pr_debug("trying to override keymap for ct %p\n", ct);
156 goto unlock_free;
157 }
158
159 if (ct_pptp_info->keymap[IP_CT_DIR_ORIGINAL] ||
160 ct_pptp_info->keymap[IP_CT_DIR_REPLY])
161 goto unlock_free;
162
163 pr_debug("adding new entries %p,%p: ", km_orig, km_repl);
164 nf_ct_dump_tuple(&km_orig->tuple);
165 nf_ct_dump_tuple(&km_repl->tuple);
166
167 list_add_tail_rcu(&km_orig->list, &net_gre->keymap_list);
168 list_add_tail_rcu(&km_repl->list, &net_gre->keymap_list);
169 ct_pptp_info->keymap[IP_CT_DIR_ORIGINAL] = km_orig;
170 ct_pptp_info->keymap[IP_CT_DIR_REPLY] = km_repl;
171 spin_unlock_bh(&keymap_lock);
172
173 return true;
174
175 unlock_free:
176 spin_unlock_bh(&keymap_lock);
177 km_free:
178 kfree(km_orig);
179 kfree(km_repl);
180 return ret;
181 }
182 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
183
184 /* destroy the keymap entries associated with specified master ct */
nf_ct_gre_keymap_destroy(struct nf_conn * ct)185 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
186 {
187 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
188 enum ip_conntrack_dir dir;
189
190 pr_debug("entering for ct %p\n", ct);
191
192 spin_lock_bh(&keymap_lock);
193 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
194 if (ct_pptp_info->keymap[dir]) {
195 pr_debug("removing %p from list\n",
196 ct_pptp_info->keymap[dir]);
197 list_del_rcu(&ct_pptp_info->keymap[dir]->list);
198 kfree_rcu(ct_pptp_info->keymap[dir], rcu);
199 ct_pptp_info->keymap[dir] = NULL;
200 }
201 }
202 spin_unlock_bh(&keymap_lock);
203 }
204 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
205
206 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
207
208 /* gre hdr info to tuple */
gre_pkt_to_tuple(const struct sk_buff * skb,unsigned int dataoff,struct net * net,struct nf_conntrack_tuple * tuple)209 bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
210 struct net *net, struct nf_conntrack_tuple *tuple)
211 {
212 const struct pptp_gre_header *pgrehdr;
213 struct pptp_gre_header _pgrehdr;
214 __be16 srckey;
215 const struct gre_base_hdr *grehdr;
216 struct gre_base_hdr _grehdr;
217
218 /* first only delinearize old RFC1701 GRE header */
219 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
220 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
221 /* try to behave like "nf_conntrack_proto_generic" */
222 tuple->src.u.all = 0;
223 tuple->dst.u.all = 0;
224 return true;
225 }
226
227 /* PPTP header is variable length, only need up to the call_id field */
228 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
229 if (!pgrehdr)
230 return true;
231
232 if (grehdr->protocol != GRE_PROTO_PPP) {
233 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
234 return false;
235 }
236
237 tuple->dst.u.gre.key = pgrehdr->call_id;
238 srckey = gre_keymap_lookup(net, tuple);
239 tuple->src.u.gre.key = srckey;
240
241 return true;
242 }
243
244 #ifdef CONFIG_NF_CONNTRACK_PROCFS
245 /* print private data for conntrack */
gre_print_conntrack(struct seq_file * s,struct nf_conn * ct)246 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
247 {
248 seq_printf(s, "timeout=%u, stream_timeout=%u ",
249 (ct->proto.gre.timeout / HZ),
250 (ct->proto.gre.stream_timeout / HZ));
251 }
252 #endif
253
gre_get_timeouts(struct net * net)254 static unsigned int *gre_get_timeouts(struct net *net)
255 {
256 return gre_pernet(net)->timeouts;
257 }
258
259 /* Returns verdict for packet, and may modify conntrack */
nf_conntrack_gre_packet(struct nf_conn * ct,struct sk_buff * skb,unsigned int dataoff,enum ip_conntrack_info ctinfo,const struct nf_hook_state * state)260 int nf_conntrack_gre_packet(struct nf_conn *ct,
261 struct sk_buff *skb,
262 unsigned int dataoff,
263 enum ip_conntrack_info ctinfo,
264 const struct nf_hook_state *state)
265 {
266 unsigned long status;
267
268 if (!nf_ct_is_confirmed(ct)) {
269 unsigned int *timeouts = nf_ct_timeout_lookup(ct);
270
271 if (!timeouts)
272 timeouts = gre_get_timeouts(nf_ct_net(ct));
273
274 /* initialize to sane value. Ideally a conntrack helper
275 * (e.g. in case of pptp) is increasing them */
276 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
277 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
278 }
279
280 status = READ_ONCE(ct->status);
281 /* If we've seen traffic both ways, this is a GRE connection.
282 * Extend timeout. */
283 if (status & IPS_SEEN_REPLY) {
284 nf_ct_refresh_acct(ct, ctinfo, skb,
285 ct->proto.gre.stream_timeout);
286
287 /* never set ASSURED for IPS_NAT_CLASH, they time out soon */
288 if (unlikely((status & IPS_NAT_CLASH)))
289 return NF_ACCEPT;
290
291 /* Also, more likely to be important, and not a probe. */
292 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
293 nf_conntrack_event_cache(IPCT_ASSURED, ct);
294 } else
295 nf_ct_refresh_acct(ct, ctinfo, skb,
296 ct->proto.gre.timeout);
297
298 return NF_ACCEPT;
299 }
300
301 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
302
303 #include <linux/netfilter/nfnetlink.h>
304 #include <linux/netfilter/nfnetlink_cttimeout.h>
305
gre_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)306 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
307 struct net *net, void *data)
308 {
309 unsigned int *timeouts = data;
310 struct nf_gre_net *net_gre = gre_pernet(net);
311
312 if (!timeouts)
313 timeouts = gre_get_timeouts(net);
314 /* set default timeouts for GRE. */
315 timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED];
316 timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED];
317
318 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
319 timeouts[GRE_CT_UNREPLIED] =
320 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
321 }
322 if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
323 timeouts[GRE_CT_REPLIED] =
324 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
325 }
326 return 0;
327 }
328
329 static int
gre_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)330 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
331 {
332 const unsigned int *timeouts = data;
333
334 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
335 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
336 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
337 htonl(timeouts[GRE_CT_REPLIED] / HZ)))
338 goto nla_put_failure;
339 return 0;
340
341 nla_put_failure:
342 return -ENOSPC;
343 }
344
345 static const struct nla_policy
346 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
347 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
348 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
349 };
350 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
351
nf_conntrack_gre_init_net(struct net * net)352 void nf_conntrack_gre_init_net(struct net *net)
353 {
354 struct nf_gre_net *net_gre = gre_pernet(net);
355 int i;
356
357 INIT_LIST_HEAD(&net_gre->keymap_list);
358 for (i = 0; i < GRE_CT_MAX; i++)
359 net_gre->timeouts[i] = gre_timeouts[i];
360 }
361
362 /* protocol helper struct */
363 const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = {
364 .l4proto = IPPROTO_GRE,
365 .allow_clash = true,
366 #ifdef CONFIG_NF_CONNTRACK_PROCFS
367 .print_conntrack = gre_print_conntrack,
368 #endif
369 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
370 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
371 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
372 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
373 .nla_policy = nf_ct_port_nla_policy,
374 #endif
375 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
376 .ctnl_timeout = {
377 .nlattr_to_obj = gre_timeout_nlattr_to_obj,
378 .obj_to_nlattr = gre_timeout_obj_to_nlattr,
379 .nlattr_max = CTA_TIMEOUT_GRE_MAX,
380 .obj_size = sizeof(unsigned int) * GRE_CT_MAX,
381 .nla_policy = gre_timeout_nla_policy,
382 },
383 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
384 };
385