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Linux/net/netfilter/xt_conntrack.c

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  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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 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 
 20 MODULE_LICENSE("GPL");
 21 MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
 22 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
 23 MODULE_DESCRIPTION("Xtables: connection tracking state match");
 24 MODULE_ALIAS("ipt_conntrack");
 25 MODULE_ALIAS("ip6t_conntrack");
 26 
 27 static bool
 28 conntrack_addrcmp(const union nf_inet_addr *kaddr,
 29                   const union nf_inet_addr *uaddr,
 30                   const union nf_inet_addr *umask, unsigned int l3proto)
 31 {
 32         if (l3proto == NFPROTO_IPV4)
 33                 return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
 34         else if (l3proto == NFPROTO_IPV6)
 35                 return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
 36                        &uaddr->in6) == 0;
 37         else
 38                 return false;
 39 }
 40 
 41 static inline bool
 42 conntrack_mt_origsrc(const struct nf_conn *ct,
 43                      const struct xt_conntrack_mtinfo2 *info,
 44                      u_int8_t family)
 45 {
 46         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
 47                &info->origsrc_addr, &info->origsrc_mask, family);
 48 }
 49 
 50 static inline bool
 51 conntrack_mt_origdst(const struct nf_conn *ct,
 52                      const struct xt_conntrack_mtinfo2 *info,
 53                      u_int8_t family)
 54 {
 55         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
 56                &info->origdst_addr, &info->origdst_mask, family);
 57 }
 58 
 59 static inline bool
 60 conntrack_mt_replsrc(const struct nf_conn *ct,
 61                      const struct xt_conntrack_mtinfo2 *info,
 62                      u_int8_t family)
 63 {
 64         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
 65                &info->replsrc_addr, &info->replsrc_mask, family);
 66 }
 67 
 68 static inline bool
 69 conntrack_mt_repldst(const struct nf_conn *ct,
 70                      const struct xt_conntrack_mtinfo2 *info,
 71                      u_int8_t family)
 72 {
 73         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
 74                &info->repldst_addr, &info->repldst_mask, family);
 75 }
 76 
 77 static inline bool
 78 ct_proto_port_check(const struct xt_conntrack_mtinfo2 *info,
 79                     const struct nf_conn *ct)
 80 {
 81         const struct nf_conntrack_tuple *tuple;
 82 
 83         tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 84         if ((info->match_flags & XT_CONNTRACK_PROTO) &&
 85             (nf_ct_protonum(ct) == info->l4proto) ^
 86             !(info->invert_flags & XT_CONNTRACK_PROTO))
 87                 return false;
 88 
 89         /* Shortcut to match all recognized protocols by using ->src.all. */
 90         if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
 91             (tuple->src.u.all == info->origsrc_port) ^
 92             !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
 93                 return false;
 94 
 95         if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
 96             (tuple->dst.u.all == info->origdst_port) ^
 97             !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
 98                 return false;
 99 
100         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
101 
102         if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
103             (tuple->src.u.all == info->replsrc_port) ^
104             !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
105                 return false;
106 
107         if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
108             (tuple->dst.u.all == info->repldst_port) ^
109             !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
110                 return false;
111 
112         return true;
113 }
114 
115 static inline bool
116 port_match(u16 min, u16 max, u16 port, bool invert)
117 {
118         return (port >= min && port <= max) ^ invert;
119 }
120 
121 static inline bool
122 ct_proto_port_check_v3(const struct xt_conntrack_mtinfo3 *info,
123                        const struct nf_conn *ct)
124 {
125         const struct nf_conntrack_tuple *tuple;
126 
127         tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
128         if ((info->match_flags & XT_CONNTRACK_PROTO) &&
129             (nf_ct_protonum(ct) == info->l4proto) ^
130             !(info->invert_flags & XT_CONNTRACK_PROTO))
131                 return false;
132 
133         /* Shortcut to match all recognized protocols by using ->src.all. */
134         if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
135             !port_match(info->origsrc_port, info->origsrc_port_high,
136                         ntohs(tuple->src.u.all),
137                         info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
138                 return false;
139 
140         if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
141             !port_match(info->origdst_port, info->origdst_port_high,
142                         ntohs(tuple->dst.u.all),
143                         info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
144                 return false;
145 
146         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
147 
148         if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
149             !port_match(info->replsrc_port, info->replsrc_port_high,
150                         ntohs(tuple->src.u.all),
151                         info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
152                 return false;
153 
154         if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
155             !port_match(info->repldst_port, info->repldst_port_high,
156                         ntohs(tuple->dst.u.all),
157                         info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
158                 return false;
159 
160         return true;
161 }
162 
163 static bool
164 conntrack_mt(const struct sk_buff *skb, struct xt_action_param *par,
165              u16 state_mask, u16 status_mask)
166 {
167         const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
168         enum ip_conntrack_info ctinfo;
169         const struct nf_conn *ct;
170         unsigned int statebit;
171 
172         ct = nf_ct_get(skb, &ctinfo);
173 
174         if (ct) {
175                 if (nf_ct_is_untracked(ct))
176                         statebit = XT_CONNTRACK_STATE_UNTRACKED;
177                 else
178                         statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
179         } else
180                 statebit = XT_CONNTRACK_STATE_INVALID;
181 
182         if (info->match_flags & XT_CONNTRACK_STATE) {
183                 if (ct != NULL) {
184                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
185                                 statebit |= XT_CONNTRACK_STATE_SNAT;
186                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
187                                 statebit |= XT_CONNTRACK_STATE_DNAT;
188                 }
189                 if (!!(state_mask & statebit) ^
190                     !(info->invert_flags & XT_CONNTRACK_STATE))
191                         return false;
192         }
193 
194         if (ct == NULL)
195                 return info->match_flags & XT_CONNTRACK_STATE;
196         if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
197             (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
198             !(info->invert_flags & XT_CONNTRACK_DIRECTION))
199                 return false;
200 
201         if (info->match_flags & XT_CONNTRACK_ORIGSRC)
202                 if (conntrack_mt_origsrc(ct, info, par->family) ^
203                     !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
204                         return false;
205 
206         if (info->match_flags & XT_CONNTRACK_ORIGDST)
207                 if (conntrack_mt_origdst(ct, info, par->family) ^
208                     !(info->invert_flags & XT_CONNTRACK_ORIGDST))
209                         return false;
210 
211         if (info->match_flags & XT_CONNTRACK_REPLSRC)
212                 if (conntrack_mt_replsrc(ct, info, par->family) ^
213                     !(info->invert_flags & XT_CONNTRACK_REPLSRC))
214                         return false;
215 
216         if (info->match_flags & XT_CONNTRACK_REPLDST)
217                 if (conntrack_mt_repldst(ct, info, par->family) ^
218                     !(info->invert_flags & XT_CONNTRACK_REPLDST))
219                         return false;
220 
221         if (par->match->revision != 3) {
222                 if (!ct_proto_port_check(info, ct))
223                         return false;
224         } else {
225                 if (!ct_proto_port_check_v3(par->matchinfo, ct))
226                         return false;
227         }
228 
229         if ((info->match_flags & XT_CONNTRACK_STATUS) &&
230             (!!(status_mask & ct->status) ^
231             !(info->invert_flags & XT_CONNTRACK_STATUS)))
232                 return false;
233 
234         if (info->match_flags & XT_CONNTRACK_EXPIRES) {
235                 unsigned long expires = 0;
236 
237                 if (timer_pending(&ct->timeout))
238                         expires = (ct->timeout.expires - jiffies) / HZ;
239                 if ((expires >= info->expires_min &&
240                     expires <= info->expires_max) ^
241                     !(info->invert_flags & XT_CONNTRACK_EXPIRES))
242                         return false;
243         }
244         return true;
245 }
246 
247 static bool
248 conntrack_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
249 {
250         const struct xt_conntrack_mtinfo1 *info = par->matchinfo;
251 
252         return conntrack_mt(skb, par, info->state_mask, info->status_mask);
253 }
254 
255 static bool
256 conntrack_mt_v2(const struct sk_buff *skb, struct xt_action_param *par)
257 {
258         const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
259 
260         return conntrack_mt(skb, par, info->state_mask, info->status_mask);
261 }
262 
263 static bool
264 conntrack_mt_v3(const struct sk_buff *skb, struct xt_action_param *par)
265 {
266         const struct xt_conntrack_mtinfo3 *info = par->matchinfo;
267 
268         return conntrack_mt(skb, par, info->state_mask, info->status_mask);
269 }
270 
271 static int conntrack_mt_check(const struct xt_mtchk_param *par)
272 {
273         int ret;
274 
275         ret = nf_ct_l3proto_try_module_get(par->family);
276         if (ret < 0)
277                 pr_info("cannot load conntrack support for proto=%u\n",
278                         par->family);
279         return ret;
280 }
281 
282 static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)
283 {
284         nf_ct_l3proto_module_put(par->family);
285 }
286 
287 static struct xt_match conntrack_mt_reg[] __read_mostly = {
288         {
289                 .name       = "conntrack",
290                 .revision   = 1,
291                 .family     = NFPROTO_UNSPEC,
292                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
293                 .match      = conntrack_mt_v1,
294                 .checkentry = conntrack_mt_check,
295                 .destroy    = conntrack_mt_destroy,
296                 .me         = THIS_MODULE,
297         },
298         {
299                 .name       = "conntrack",
300                 .revision   = 2,
301                 .family     = NFPROTO_UNSPEC,
302                 .matchsize  = sizeof(struct xt_conntrack_mtinfo2),
303                 .match      = conntrack_mt_v2,
304                 .checkentry = conntrack_mt_check,
305                 .destroy    = conntrack_mt_destroy,
306                 .me         = THIS_MODULE,
307         },
308         {
309                 .name       = "conntrack",
310                 .revision   = 3,
311                 .family     = NFPROTO_UNSPEC,
312                 .matchsize  = sizeof(struct xt_conntrack_mtinfo3),
313                 .match      = conntrack_mt_v3,
314                 .checkentry = conntrack_mt_check,
315                 .destroy    = conntrack_mt_destroy,
316                 .me         = THIS_MODULE,
317         },
318 };
319 
320 static int __init conntrack_mt_init(void)
321 {
322         return xt_register_matches(conntrack_mt_reg,
323                ARRAY_SIZE(conntrack_mt_reg));
324 }
325 
326 static void __exit conntrack_mt_exit(void)
327 {
328         xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
329 }
330 
331 module_init(conntrack_mt_init);
332 module_exit(conntrack_mt_exit);
333 

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