xt_conntrack.c revision d6d3f08b0fd998b647a05540cedd11a067b72867 
1/*
2 *	xt_conntrack - Netfilter module to match connection tracking
3 *	information. (Superset of Rusty's minimalistic state match.)
4 *
5 *	(C) 2001  Marc Boucher (marc@mbsi.ca).
6 *	Copyright © CC Computer Consultants GmbH, 2007 - 2008
7 *
8 *	This program is free software; you can redistribute it and/or modify
9 *	it under the terms of the GNU General Public License version 2 as
10 *	published by the Free Software Foundation.
11 */
12
13#include <linux/module.h>
14#include <linux/skbuff.h>
15#include <net/ipv6.h>
16#include <linux/netfilter/x_tables.h>
17#include <linux/netfilter/xt_conntrack.h>
18#include <net/netfilter/nf_conntrack.h>
19
20MODULE_LICENSE("GPL");
21MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
22MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>");
23MODULE_DESCRIPTION("Xtables: connection tracking state match");
24MODULE_ALIAS("ipt_conntrack");
25MODULE_ALIAS("ip6t_conntrack");
26
27static bool
28conntrack_mt_v0(const struct sk_buff *skb, const struct xt_match_param *par)
29{
30	const struct xt_conntrack_info *sinfo = par->matchinfo;
31	const struct nf_conn *ct;
32	enum ip_conntrack_info ctinfo;
33	unsigned int statebit;
34
35	ct = nf_ct_get(skb, &ctinfo);
36
37#define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & (invflg)))
38
39	if (ct == &nf_conntrack_untracked)
40		statebit = XT_CONNTRACK_STATE_UNTRACKED;
41	else if (ct)
42		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
43	else
44		statebit = XT_CONNTRACK_STATE_INVALID;
45
46	if (sinfo->flags & XT_CONNTRACK_STATE) {
47		if (ct) {
48			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
49				statebit |= XT_CONNTRACK_STATE_SNAT;
50			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
51				statebit |= XT_CONNTRACK_STATE_DNAT;
52		}
53		if (FWINV((statebit & sinfo->statemask) == 0,
54			  XT_CONNTRACK_STATE))
55			return false;
56	}
57
58	if (ct == NULL) {
59		if (sinfo->flags & ~XT_CONNTRACK_STATE)
60			return false;
61		return true;
62	}
63
64	if (sinfo->flags & XT_CONNTRACK_PROTO &&
65	    FWINV(nf_ct_protonum(ct) !=
66		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
67		  XT_CONNTRACK_PROTO))
68		return false;
69
70	if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
71	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
72		   sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
73		  sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
74		  XT_CONNTRACK_ORIGSRC))
75		return false;
76
77	if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
78	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
79		   sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
80		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
81		  XT_CONNTRACK_ORIGDST))
82		return false;
83
84	if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
85	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
86		   sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
87		  sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
88		  XT_CONNTRACK_REPLSRC))
89		return false;
90
91	if (sinfo->flags & XT_CONNTRACK_REPLDST &&
92	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
93		   sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
94		  sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
95		  XT_CONNTRACK_REPLDST))
96		return false;
97
98	if (sinfo->flags & XT_CONNTRACK_STATUS &&
99	    FWINV((ct->status & sinfo->statusmask) == 0,
100		  XT_CONNTRACK_STATUS))
101		return false;
102
103	if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
104		unsigned long expires = timer_pending(&ct->timeout) ?
105					(ct->timeout.expires - jiffies)/HZ : 0;
106
107		if (FWINV(!(expires >= sinfo->expires_min &&
108			    expires <= sinfo->expires_max),
109			  XT_CONNTRACK_EXPIRES))
110			return false;
111	}
112	return true;
113#undef FWINV
114}
115
116static bool
117conntrack_addrcmp(const union nf_inet_addr *kaddr,
118                  const union nf_inet_addr *uaddr,
119                  const union nf_inet_addr *umask, unsigned int l3proto)
120{
121	if (l3proto == NFPROTO_IPV4)
122		return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
123	else if (l3proto == NFPROTO_IPV6)
124		return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
125		       &uaddr->in6) == 0;
126	else
127		return false;
128}
129
130static inline bool
131conntrack_mt_origsrc(const struct nf_conn *ct,
132                     const struct xt_conntrack_mtinfo2 *info,
133		     u_int8_t family)
134{
135	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
136	       &info->origsrc_addr, &info->origsrc_mask, family);
137}
138
139static inline bool
140conntrack_mt_origdst(const struct nf_conn *ct,
141                     const struct xt_conntrack_mtinfo2 *info,
142		     u_int8_t family)
143{
144	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
145	       &info->origdst_addr, &info->origdst_mask, family);
146}
147
148static inline bool
149conntrack_mt_replsrc(const struct nf_conn *ct,
150                     const struct xt_conntrack_mtinfo2 *info,
151		     u_int8_t family)
152{
153	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
154	       &info->replsrc_addr, &info->replsrc_mask, family);
155}
156
157static inline bool
158conntrack_mt_repldst(const struct nf_conn *ct,
159                     const struct xt_conntrack_mtinfo2 *info,
160		     u_int8_t family)
161{
162	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
163	       &info->repldst_addr, &info->repldst_mask, family);
164}
165
166static inline bool
167ct_proto_port_check(const struct xt_conntrack_mtinfo2 *info,
168                    const struct nf_conn *ct)
169{
170	const struct nf_conntrack_tuple *tuple;
171
172	tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
173	if ((info->match_flags & XT_CONNTRACK_PROTO) &&
174	    (nf_ct_protonum(ct) == info->l4proto) ^
175	    !(info->invert_flags & XT_CONNTRACK_PROTO))
176		return false;
177
178	/* Shortcut to match all recognized protocols by using ->src.all. */
179	if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
180	    (tuple->src.u.all == info->origsrc_port) ^
181	    !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
182		return false;
183
184	if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
185	    (tuple->dst.u.all == info->origdst_port) ^
186	    !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
187		return false;
188
189	tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
190
191	if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
192	    (tuple->src.u.all == info->replsrc_port) ^
193	    !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
194		return false;
195
196	if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
197	    (tuple->dst.u.all == info->repldst_port) ^
198	    !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
199		return false;
200
201	return true;
202}
203
204static bool
205conntrack_mt(const struct sk_buff *skb, const struct xt_match_param *par)
206{
207	const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
208	enum ip_conntrack_info ctinfo;
209	const struct nf_conn *ct;
210	unsigned int statebit;
211
212	ct = nf_ct_get(skb, &ctinfo);
213
214	if (ct == &nf_conntrack_untracked)
215		statebit = XT_CONNTRACK_STATE_UNTRACKED;
216	else if (ct != NULL)
217		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
218	else
219		statebit = XT_CONNTRACK_STATE_INVALID;
220
221	if (info->match_flags & XT_CONNTRACK_STATE) {
222		if (ct != NULL) {
223			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
224				statebit |= XT_CONNTRACK_STATE_SNAT;
225			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
226				statebit |= XT_CONNTRACK_STATE_DNAT;
227		}
228		if (!!(info->state_mask & statebit) ^
229		    !(info->invert_flags & XT_CONNTRACK_STATE))
230			return false;
231	}
232
233	if (ct == NULL)
234		return info->match_flags & XT_CONNTRACK_STATE;
235	if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
236	    (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
237	    !!(info->invert_flags & XT_CONNTRACK_DIRECTION))
238		return false;
239
240	if (info->match_flags & XT_CONNTRACK_ORIGSRC)
241		if (conntrack_mt_origsrc(ct, info, par->family) ^
242		    !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
243			return false;
244
245	if (info->match_flags & XT_CONNTRACK_ORIGDST)
246		if (conntrack_mt_origdst(ct, info, par->family) ^
247		    !(info->invert_flags & XT_CONNTRACK_ORIGDST))
248			return false;
249
250	if (info->match_flags & XT_CONNTRACK_REPLSRC)
251		if (conntrack_mt_replsrc(ct, info, par->family) ^
252		    !(info->invert_flags & XT_CONNTRACK_REPLSRC))
253			return false;
254
255	if (info->match_flags & XT_CONNTRACK_REPLDST)
256		if (conntrack_mt_repldst(ct, info, par->family) ^
257		    !(info->invert_flags & XT_CONNTRACK_REPLDST))
258			return false;
259
260	if (!ct_proto_port_check(info, ct))
261		return false;
262
263	if ((info->match_flags & XT_CONNTRACK_STATUS) &&
264	    (!!(info->status_mask & ct->status) ^
265	    !(info->invert_flags & XT_CONNTRACK_STATUS)))
266		return false;
267
268	if (info->match_flags & XT_CONNTRACK_EXPIRES) {
269		unsigned long expires = 0;
270
271		if (timer_pending(&ct->timeout))
272			expires = (ct->timeout.expires - jiffies) / HZ;
273		if ((expires >= info->expires_min &&
274		    expires <= info->expires_max) ^
275		    !(info->invert_flags & XT_CONNTRACK_EXPIRES))
276			return false;
277	}
278	return true;
279}
280
281static bool
282conntrack_mt_v1(const struct sk_buff *skb, const struct xt_match_param *par)
283{
284	const struct xt_conntrack_mtinfo2 *const *info = par->matchinfo;
285	struct xt_match_param newpar = *par;
286
287	newpar.matchinfo = *info;
288	return conntrack_mt(skb, &newpar);
289}
290
291static bool conntrack_mt_check(const struct xt_mtchk_param *par)
292{
293	if (nf_ct_l3proto_try_module_get(par->family) < 0) {
294		printk(KERN_WARNING "can't load conntrack support for "
295				    "proto=%u\n", par->family);
296		return false;
297	}
298	return true;
299}
300
301static bool conntrack_mt_check_v1(const struct xt_mtchk_param *par)
302{
303	struct xt_conntrack_mtinfo1 *info = par->matchinfo;
304	struct xt_conntrack_mtinfo2 *up;
305	int ret = conntrack_mt_check(par);
306
307	if (ret < 0)
308		return ret;
309
310	up = kmalloc(sizeof(*up), GFP_KERNEL);
311	if (up == NULL) {
312		nf_ct_l3proto_module_put(par->family);
313		return -ENOMEM;
314	}
315
316	/*
317	 * The strategy here is to minimize the overhead of v1 matching,
318	 * by prebuilding a v2 struct and putting the pointer into the
319	 * v1 dataspace.
320	 */
321	memcpy(up, info, offsetof(typeof(*info), state_mask));
322	up->state_mask  = info->state_mask;
323	up->status_mask = info->status_mask;
324	*(void **)info  = up;
325	return true;
326}
327
328static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)
329{
330	nf_ct_l3proto_module_put(par->family);
331}
332
333static void conntrack_mt_destroy_v1(const struct xt_mtdtor_param *par)
334{
335	struct xt_conntrack_mtinfo2 **info = par->matchinfo;
336	kfree(*info);
337	conntrack_mt_destroy(par);
338}
339
340#ifdef CONFIG_COMPAT
341struct compat_xt_conntrack_info
342{
343	compat_uint_t			statemask;
344	compat_uint_t			statusmask;
345	struct ip_conntrack_old_tuple	tuple[IP_CT_DIR_MAX];
346	struct in_addr			sipmsk[IP_CT_DIR_MAX];
347	struct in_addr			dipmsk[IP_CT_DIR_MAX];
348	compat_ulong_t			expires_min;
349	compat_ulong_t			expires_max;
350	u_int8_t			flags;
351	u_int8_t			invflags;
352};
353
354static void conntrack_mt_compat_from_user_v0(void *dst, void *src)
355{
356	const struct compat_xt_conntrack_info *cm = src;
357	struct xt_conntrack_info m = {
358		.statemask	= cm->statemask,
359		.statusmask	= cm->statusmask,
360		.expires_min	= cm->expires_min,
361		.expires_max	= cm->expires_max,
362		.flags		= cm->flags,
363		.invflags	= cm->invflags,
364	};
365	memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
366	memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
367	memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
368	memcpy(dst, &m, sizeof(m));
369}
370
371static int conntrack_mt_compat_to_user_v0(void __user *dst, void *src)
372{
373	const struct xt_conntrack_info *m = src;
374	struct compat_xt_conntrack_info cm = {
375		.statemask	= m->statemask,
376		.statusmask	= m->statusmask,
377		.expires_min	= m->expires_min,
378		.expires_max	= m->expires_max,
379		.flags		= m->flags,
380		.invflags	= m->invflags,
381	};
382	memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
383	memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
384	memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
385	return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
386}
387#endif
388
389static struct xt_match conntrack_mt_reg[] __read_mostly = {
390	{
391		.name       = "conntrack",
392		.revision   = 0,
393		.family     = NFPROTO_IPV4,
394		.match      = conntrack_mt_v0,
395		.checkentry = conntrack_mt_check,
396		.destroy    = conntrack_mt_destroy,
397		.matchsize  = sizeof(struct xt_conntrack_info),
398		.me         = THIS_MODULE,
399#ifdef CONFIG_COMPAT
400		.compatsize       = sizeof(struct compat_xt_conntrack_info),
401		.compat_from_user = conntrack_mt_compat_from_user_v0,
402		.compat_to_user   = conntrack_mt_compat_to_user_v0,
403#endif
404	},
405	{
406		.name       = "conntrack",
407		.revision   = 1,
408		.family     = NFPROTO_UNSPEC,
409		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),
410		.match      = conntrack_mt_v1,
411		.checkentry = conntrack_mt_check_v1,
412		.destroy    = conntrack_mt_destroy_v1,
413		.me         = THIS_MODULE,
414	},
415	{
416		.name       = "conntrack",
417		.revision   = 2,
418		.family     = NFPROTO_UNSPEC,
419		.matchsize  = sizeof(struct xt_conntrack_mtinfo2),
420		.match      = conntrack_mt,
421		.checkentry = conntrack_mt_check,
422		.destroy    = conntrack_mt_destroy,
423		.me         = THIS_MODULE,
424	},
425};
426
427static int __init conntrack_mt_init(void)
428{
429	return xt_register_matches(conntrack_mt_reg,
430	       ARRAY_SIZE(conntrack_mt_reg));
431}
432
433static void __exit conntrack_mt_exit(void)
434{
435	xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
436}
437
438module_init(conntrack_mt_init);
439module_exit(conntrack_mt_exit);
440