xt_conntrack.c revision 6556874dc3770aefae89907b3cf9be8e23d66137 
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 net_device *in,
29                const struct net_device *out, const struct xt_match *match,
30                const void *matchinfo, int offset, unsigned int protoff,
31                bool *hotdrop)
32{
33	const struct xt_conntrack_info *sinfo = matchinfo;
34	const struct nf_conn *ct;
35	enum ip_conntrack_info ctinfo;
36	unsigned int statebit;
37
38	ct = nf_ct_get(skb, &ctinfo);
39
40#define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & (invflg)))
41
42	if (ct == &nf_conntrack_untracked)
43		statebit = XT_CONNTRACK_STATE_UNTRACKED;
44	else if (ct)
45		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
46	else
47		statebit = XT_CONNTRACK_STATE_INVALID;
48
49	if (sinfo->flags & XT_CONNTRACK_STATE) {
50		if (ct) {
51			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
52				statebit |= XT_CONNTRACK_STATE_SNAT;
53			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
54				statebit |= XT_CONNTRACK_STATE_DNAT;
55		}
56		if (FWINV((statebit & sinfo->statemask) == 0,
57			  XT_CONNTRACK_STATE))
58			return false;
59	}
60
61	if (ct == NULL) {
62		if (sinfo->flags & ~XT_CONNTRACK_STATE)
63			return false;
64		return true;
65	}
66
67	if (sinfo->flags & XT_CONNTRACK_PROTO &&
68	    FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
69		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
70		  XT_CONNTRACK_PROTO))
71		return false;
72
73	if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
74	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
75		   sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
76		  sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
77		  XT_CONNTRACK_ORIGSRC))
78		return false;
79
80	if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
81	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
82		   sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
83		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
84		  XT_CONNTRACK_ORIGDST))
85		return false;
86
87	if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
88	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
89		   sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
90		  sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
91		  XT_CONNTRACK_REPLSRC))
92		return false;
93
94	if (sinfo->flags & XT_CONNTRACK_REPLDST &&
95	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
96		   sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
97		  sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
98		  XT_CONNTRACK_REPLDST))
99		return false;
100
101	if (sinfo->flags & XT_CONNTRACK_STATUS &&
102	    FWINV((ct->status & sinfo->statusmask) == 0,
103		  XT_CONNTRACK_STATUS))
104		return false;
105
106	if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
107		unsigned long expires = timer_pending(&ct->timeout) ?
108					(ct->timeout.expires - jiffies)/HZ : 0;
109
110		if (FWINV(!(expires >= sinfo->expires_min &&
111			    expires <= sinfo->expires_max),
112			  XT_CONNTRACK_EXPIRES))
113			return false;
114	}
115	return true;
116#undef FWINV
117}
118
119static bool
120conntrack_addrcmp(const union nf_inet_addr *kaddr,
121                  const union nf_inet_addr *uaddr,
122                  const union nf_inet_addr *umask, unsigned int l3proto)
123{
124	if (l3proto == AF_INET)
125		return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
126	else if (l3proto == AF_INET6)
127		return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
128		       &uaddr->in6) == 0;
129	else
130		return false;
131}
132
133static inline bool
134conntrack_mt_origsrc(const struct nf_conn *ct,
135                     const struct xt_conntrack_mtinfo1 *info,
136                     unsigned int family)
137{
138	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
139	       &info->origsrc_addr, &info->origsrc_mask, family);
140}
141
142static inline bool
143conntrack_mt_origdst(const struct nf_conn *ct,
144                     const struct xt_conntrack_mtinfo1 *info,
145                     unsigned int family)
146{
147	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
148	       &info->origdst_addr, &info->origdst_mask, family);
149}
150
151static inline bool
152conntrack_mt_replsrc(const struct nf_conn *ct,
153                     const struct xt_conntrack_mtinfo1 *info,
154                     unsigned int family)
155{
156	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
157	       &info->replsrc_addr, &info->replsrc_mask, family);
158}
159
160static inline bool
161conntrack_mt_repldst(const struct nf_conn *ct,
162                     const struct xt_conntrack_mtinfo1 *info,
163                     unsigned int family)
164{
165	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
166	       &info->repldst_addr, &info->repldst_mask, family);
167}
168
169static inline bool
170ct_proto_port_check(const struct xt_conntrack_mtinfo1 *info,
171                    const struct nf_conn *ct)
172{
173	const struct nf_conntrack_tuple *tuple;
174
175	tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
176	if ((info->match_flags & XT_CONNTRACK_PROTO) &&
177	    (tuple->dst.protonum == info->l4proto) ^
178	    !(info->invert_flags & XT_CONNTRACK_PROTO))
179		return false;
180
181	/* Shortcut to match all recognized protocols by using ->src.all. */
182	if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
183	    (tuple->src.u.all == info->origsrc_port) ^
184	    !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
185		return false;
186
187	if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
188	    (tuple->dst.u.all == info->origdst_port) ^
189	    !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
190		return false;
191
192	tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
193
194	if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
195	    (tuple->src.u.all == info->replsrc_port) ^
196	    !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
197		return false;
198
199	if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
200	    (tuple->dst.u.all == info->repldst_port) ^
201	    !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
202		return false;
203
204	return true;
205}
206
207static bool
208conntrack_mt(const struct sk_buff *skb, const struct net_device *in,
209             const struct net_device *out, const struct xt_match *match,
210             const void *matchinfo, int offset, unsigned int protoff,
211             bool *hotdrop)
212{
213	const struct xt_conntrack_mtinfo1 *info = matchinfo;
214	enum ip_conntrack_info ctinfo;
215	const struct nf_conn *ct;
216	unsigned int statebit;
217
218	ct = nf_ct_get(skb, &ctinfo);
219
220	if (ct == &nf_conntrack_untracked)
221		statebit = XT_CONNTRACK_STATE_UNTRACKED;
222	else if (ct != NULL)
223		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
224	else
225		statebit = XT_CONNTRACK_STATE_INVALID;
226
227	if (info->match_flags & XT_CONNTRACK_STATE) {
228		if (ct != NULL) {
229			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
230				statebit |= XT_CONNTRACK_STATE_SNAT;
231			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
232				statebit |= XT_CONNTRACK_STATE_DNAT;
233		}
234		if (!!(info->state_mask & statebit) ^
235		    !(info->invert_flags & XT_CONNTRACK_STATE))
236			return false;
237	}
238
239	if (ct == NULL)
240		return info->match_flags & XT_CONNTRACK_STATE;
241	if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
242	    (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
243	    !!(info->invert_flags & XT_CONNTRACK_DIRECTION))
244		return false;
245
246	if (info->match_flags & XT_CONNTRACK_ORIGSRC)
247		if (conntrack_mt_origsrc(ct, info, match->family) ^
248		    !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
249			return false;
250
251	if (info->match_flags & XT_CONNTRACK_ORIGDST)
252		if (conntrack_mt_origdst(ct, info, match->family) ^
253		    !(info->invert_flags & XT_CONNTRACK_ORIGDST))
254			return false;
255
256	if (info->match_flags & XT_CONNTRACK_REPLSRC)
257		if (conntrack_mt_replsrc(ct, info, match->family) ^
258		    !(info->invert_flags & XT_CONNTRACK_REPLSRC))
259			return false;
260
261	if (info->match_flags & XT_CONNTRACK_REPLDST)
262		if (conntrack_mt_repldst(ct, info, match->family) ^
263		    !(info->invert_flags & XT_CONNTRACK_REPLDST))
264			return false;
265
266	if (!ct_proto_port_check(info, ct))
267		return false;
268
269	if ((info->match_flags & XT_CONNTRACK_STATUS) &&
270	    (!!(info->status_mask & ct->status) ^
271	    !(info->invert_flags & XT_CONNTRACK_STATUS)))
272		return false;
273
274	if (info->match_flags & XT_CONNTRACK_EXPIRES) {
275		unsigned long expires = 0;
276
277		if (timer_pending(&ct->timeout))
278			expires = (ct->timeout.expires - jiffies) / HZ;
279		if ((expires >= info->expires_min &&
280		    expires <= info->expires_max) ^
281		    !(info->invert_flags & XT_CONNTRACK_EXPIRES))
282			return false;
283	}
284	return true;
285}
286
287static bool
288conntrack_mt_check(const char *tablename, const void *ip,
289                   const struct xt_match *match, void *matchinfo,
290                   unsigned int hook_mask)
291{
292	if (nf_ct_l3proto_try_module_get(match->family) < 0) {
293		printk(KERN_WARNING "can't load conntrack support for "
294				    "proto=%u\n", match->family);
295		return false;
296	}
297	return true;
298}
299
300static void
301conntrack_mt_destroy(const struct xt_match *match, void *matchinfo)
302{
303	nf_ct_l3proto_module_put(match->family);
304}
305
306#ifdef CONFIG_COMPAT
307struct compat_xt_conntrack_info
308{
309	compat_uint_t			statemask;
310	compat_uint_t			statusmask;
311	struct ip_conntrack_old_tuple	tuple[IP_CT_DIR_MAX];
312	struct in_addr			sipmsk[IP_CT_DIR_MAX];
313	struct in_addr			dipmsk[IP_CT_DIR_MAX];
314	compat_ulong_t			expires_min;
315	compat_ulong_t			expires_max;
316	u_int8_t			flags;
317	u_int8_t			invflags;
318};
319
320static void conntrack_mt_compat_from_user_v0(void *dst, void *src)
321{
322	const struct compat_xt_conntrack_info *cm = src;
323	struct xt_conntrack_info m = {
324		.statemask	= cm->statemask,
325		.statusmask	= cm->statusmask,
326		.expires_min	= cm->expires_min,
327		.expires_max	= cm->expires_max,
328		.flags		= cm->flags,
329		.invflags	= cm->invflags,
330	};
331	memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
332	memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
333	memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
334	memcpy(dst, &m, sizeof(m));
335}
336
337static int conntrack_mt_compat_to_user_v0(void __user *dst, void *src)
338{
339	const struct xt_conntrack_info *m = src;
340	struct compat_xt_conntrack_info cm = {
341		.statemask	= m->statemask,
342		.statusmask	= m->statusmask,
343		.expires_min	= m->expires_min,
344		.expires_max	= m->expires_max,
345		.flags		= m->flags,
346		.invflags	= m->invflags,
347	};
348	memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
349	memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
350	memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
351	return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
352}
353#endif
354
355static struct xt_match conntrack_mt_reg[] __read_mostly = {
356	{
357		.name       = "conntrack",
358		.revision   = 0,
359		.family     = AF_INET,
360		.match      = conntrack_mt_v0,
361		.checkentry = conntrack_mt_check,
362		.destroy    = conntrack_mt_destroy,
363		.matchsize  = sizeof(struct xt_conntrack_info),
364		.me         = THIS_MODULE,
365#ifdef CONFIG_COMPAT
366		.compatsize       = sizeof(struct compat_xt_conntrack_info),
367		.compat_from_user = conntrack_mt_compat_from_user_v0,
368		.compat_to_user   = conntrack_mt_compat_to_user_v0,
369#endif
370	},
371	{
372		.name       = "conntrack",
373		.revision   = 1,
374		.family     = AF_INET,
375		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),
376		.match      = conntrack_mt,
377		.checkentry = conntrack_mt_check,
378		.destroy    = conntrack_mt_destroy,
379		.me         = THIS_MODULE,
380	},
381	{
382		.name       = "conntrack",
383		.revision   = 1,
384		.family     = AF_INET6,
385		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),
386		.match      = conntrack_mt,
387		.checkentry = conntrack_mt_check,
388		.destroy    = conntrack_mt_destroy,
389		.me         = THIS_MODULE,
390	},
391};
392
393static int __init conntrack_mt_init(void)
394{
395	return xt_register_matches(conntrack_mt_reg,
396	       ARRAY_SIZE(conntrack_mt_reg));
397}
398
399static void __exit conntrack_mt_exit(void)
400{
401	xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
402}
403
404module_init(conntrack_mt_init);
405module_exit(conntrack_mt_exit);
406