ce9edbcc01e387dc8ca320f28adc40520718dbae
[linux-2.6.git] / net / ipv4 / netfilter / nf_nat_sip.c
1 /* SIP extension for UDP NAT alteration.
2  *
3  * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
4  * based on RR's ip_nat_ftp.c and other modules.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  */
10
11 #include <linux/module.h>
12 #include <linux/skbuff.h>
13 #include <linux/ip.h>
14 #include <net/ip.h>
15 #include <linux/udp.h>
16
17 #include <net/netfilter/nf_nat.h>
18 #include <net/netfilter/nf_nat_helper.h>
19 #include <net/netfilter/nf_nat_rule.h>
20 #include <net/netfilter/nf_conntrack_helper.h>
21 #include <net/netfilter/nf_conntrack_expect.h>
22 #include <linux/netfilter/nf_conntrack_sip.h>
23
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
26 MODULE_DESCRIPTION("SIP NAT helper");
27 MODULE_ALIAS("ip_nat_sip");
28
29 struct addr_map {
30         struct {
31                 char            src[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
32                 char            dst[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
33                 unsigned int    srclen, srciplen;
34                 unsigned int    dstlen, dstiplen;
35         } addr[IP_CT_DIR_MAX];
36 };
37
38 static void addr_map_init(struct nf_conn *ct, struct addr_map *map)
39 {
40         struct nf_conntrack_tuple *t;
41         enum ip_conntrack_dir dir;
42         unsigned int n;
43
44         for (dir = 0; dir < IP_CT_DIR_MAX; dir++) {
45                 t = &ct->tuplehash[dir].tuple;
46
47                 n = sprintf(map->addr[dir].src, "%u.%u.%u.%u",
48                             NIPQUAD(t->src.u3.ip));
49                 map->addr[dir].srciplen = n;
50                 n += sprintf(map->addr[dir].src + n, ":%u",
51                              ntohs(t->src.u.udp.port));
52                 map->addr[dir].srclen = n;
53
54                 n = sprintf(map->addr[dir].dst, "%u.%u.%u.%u",
55                             NIPQUAD(t->dst.u3.ip));
56                 map->addr[dir].dstiplen = n;
57                 n += sprintf(map->addr[dir].dst + n, ":%u",
58                              ntohs(t->dst.u.udp.port));
59                 map->addr[dir].dstlen = n;
60         }
61 }
62
63 static int map_sip_addr(struct sk_buff *skb, enum ip_conntrack_info ctinfo,
64                         struct nf_conn *ct, const char **dptr, size_t dlen,
65                         enum sip_header_pos pos, struct addr_map *map)
66 {
67         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
68         unsigned int matchlen, matchoff, addrlen;
69         char *addr;
70
71         if (ct_sip_get_info(ct, *dptr, dlen, &matchoff, &matchlen, pos) <= 0)
72                 return 1;
73
74         if ((matchlen == map->addr[dir].srciplen ||
75              matchlen == map->addr[dir].srclen) &&
76             memcmp(*dptr + matchoff, map->addr[dir].src, matchlen) == 0) {
77                 addr    = map->addr[!dir].dst;
78                 addrlen = map->addr[!dir].dstlen;
79         } else if ((matchlen == map->addr[dir].dstiplen ||
80                     matchlen == map->addr[dir].dstlen) &&
81                    memcmp(*dptr + matchoff, map->addr[dir].dst, matchlen) == 0) {
82                 addr    = map->addr[!dir].src;
83                 addrlen = map->addr[!dir].srclen;
84         } else
85                 return 1;
86
87         if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
88                                       matchoff, matchlen, addr, addrlen))
89                 return 0;
90         *dptr = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr);
91         return 1;
92
93 }
94
95 static unsigned int ip_nat_sip(struct sk_buff *skb,
96                                enum ip_conntrack_info ctinfo,
97                                struct nf_conn *ct,
98                                const char **dptr)
99 {
100         enum sip_header_pos pos;
101         struct addr_map map;
102         int dataoff, datalen;
103
104         dataoff = ip_hdrlen(skb) + sizeof(struct udphdr);
105         datalen = skb->len - dataoff;
106         if (datalen < sizeof("SIP/2.0") - 1)
107                 return NF_ACCEPT;
108
109         addr_map_init(ct, &map);
110
111         /* Basic rules: requests and responses. */
112         if (strncmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) != 0) {
113                 /* 10.2: Constructing the REGISTER Request:
114                  *
115                  * The "userinfo" and "@" components of the SIP URI MUST NOT
116                  * be present.
117                  */
118                 if (datalen >= sizeof("REGISTER") - 1 &&
119                     strncmp(*dptr, "REGISTER", sizeof("REGISTER") - 1) == 0)
120                         pos = POS_REG_REQ_URI;
121                 else
122                         pos = POS_REQ_URI;
123
124                 if (!map_sip_addr(skb, ctinfo, ct, dptr, datalen, pos, &map))
125                         return NF_DROP;
126         }
127
128         if (!map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_FROM, &map) ||
129             !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_TO, &map) ||
130             !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_VIA, &map) ||
131             !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_CONTACT, &map))
132                 return NF_DROP;
133         return NF_ACCEPT;
134 }
135
136 static unsigned int mangle_sip_packet(struct sk_buff *skb,
137                                       enum ip_conntrack_info ctinfo,
138                                       struct nf_conn *ct,
139                                       const char **dptr, size_t dlen,
140                                       char *buffer, int bufflen,
141                                       enum sip_header_pos pos)
142 {
143         unsigned int matchlen, matchoff;
144
145         if (ct_sip_get_info(ct, *dptr, dlen, &matchoff, &matchlen, pos) <= 0)
146                 return 0;
147
148         if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
149                                       matchoff, matchlen, buffer, bufflen))
150                 return 0;
151
152         /* We need to reload this. Thanks Patrick. */
153         *dptr = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr);
154         return 1;
155 }
156
157 static int mangle_content_len(struct sk_buff *skb,
158                               enum ip_conntrack_info ctinfo,
159                               struct nf_conn *ct,
160                               const char *dptr)
161 {
162         unsigned int dataoff, matchoff, matchlen;
163         char buffer[sizeof("65536")];
164         int bufflen;
165
166         dataoff = ip_hdrlen(skb) + sizeof(struct udphdr);
167
168         /* Get actual SDP lenght */
169         if (ct_sip_get_info(ct, dptr, skb->len - dataoff, &matchoff,
170                             &matchlen, POS_SDP_HEADER) > 0) {
171
172                 /* since ct_sip_get_info() give us a pointer passing 'v='
173                    we need to add 2 bytes in this count. */
174                 int c_len = skb->len - dataoff - matchoff + 2;
175
176                 /* Now, update SDP length */
177                 if (ct_sip_get_info(ct, dptr, skb->len - dataoff, &matchoff,
178                                     &matchlen, POS_CONTENT) > 0) {
179
180                         bufflen = sprintf(buffer, "%u", c_len);
181                         return nf_nat_mangle_udp_packet(skb, ct, ctinfo,
182                                                         matchoff, matchlen,
183                                                         buffer, bufflen);
184                 }
185         }
186         return 0;
187 }
188
189 static unsigned int mangle_sdp(struct sk_buff *skb,
190                                enum ip_conntrack_info ctinfo,
191                                struct nf_conn *ct,
192                                __be32 newip, u_int16_t port,
193                                const char *dptr)
194 {
195         char buffer[sizeof("nnn.nnn.nnn.nnn")];
196         unsigned int dataoff, bufflen;
197
198         dataoff = ip_hdrlen(skb) + sizeof(struct udphdr);
199
200         /* Mangle owner and contact info. */
201         bufflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(newip));
202         if (!mangle_sip_packet(skb, ctinfo, ct, &dptr, skb->len - dataoff,
203                                buffer, bufflen, POS_OWNER_IP4))
204                 return 0;
205
206         if (!mangle_sip_packet(skb, ctinfo, ct, &dptr, skb->len - dataoff,
207                                buffer, bufflen, POS_CONNECTION_IP4))
208                 return 0;
209
210         /* Mangle media port. */
211         bufflen = sprintf(buffer, "%u", port);
212         if (!mangle_sip_packet(skb, ctinfo, ct, &dptr, skb->len - dataoff,
213                                buffer, bufflen, POS_MEDIA))
214                 return 0;
215
216         return mangle_content_len(skb, ctinfo, ct, dptr);
217 }
218
219 static void ip_nat_sdp_expect(struct nf_conn *ct,
220                               struct nf_conntrack_expect *exp)
221 {
222         struct nf_nat_range range;
223
224         /* This must be a fresh one. */
225         BUG_ON(ct->status & IPS_NAT_DONE_MASK);
226
227         /* Change src to where master sends to */
228         range.flags = IP_NAT_RANGE_MAP_IPS;
229         range.min_ip = range.max_ip
230                 = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
231         /* hook doesn't matter, but it has to do source manip */
232         nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
233
234         /* For DST manip, map port here to where it's expected. */
235         range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
236         range.min = range.max = exp->saved_proto;
237         range.min_ip = range.max_ip = exp->saved_ip;
238         /* hook doesn't matter, but it has to do destination manip */
239         nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
240 }
241
242 /* So, this packet has hit the connection tracking matching code.
243    Mangle it, and change the expectation to match the new version. */
244 static unsigned int ip_nat_sdp(struct sk_buff *skb,
245                                enum ip_conntrack_info ctinfo,
246                                struct nf_conntrack_expect *exp,
247                                const char *dptr)
248 {
249         struct nf_conn *ct = exp->master;
250         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
251         __be32 newip;
252         u_int16_t port;
253
254         /* Connection will come from reply */
255         if (ct->tuplehash[dir].tuple.src.u3.ip ==
256             ct->tuplehash[!dir].tuple.dst.u3.ip)
257                 newip = exp->tuple.dst.u3.ip;
258         else
259                 newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
260
261         exp->saved_ip = exp->tuple.dst.u3.ip;
262         exp->tuple.dst.u3.ip = newip;
263         exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
264         exp->dir = !dir;
265
266         /* When you see the packet, we need to NAT it the same as the
267            this one. */
268         exp->expectfn = ip_nat_sdp_expect;
269
270         /* Try to get same port: if not, try to change it. */
271         for (port = ntohs(exp->saved_proto.udp.port); port != 0; port++) {
272                 exp->tuple.dst.u.udp.port = htons(port);
273                 if (nf_ct_expect_related(exp) == 0)
274                         break;
275         }
276
277         if (port == 0)
278                 return NF_DROP;
279
280         if (!mangle_sdp(skb, ctinfo, ct, newip, port, dptr)) {
281                 nf_ct_unexpect_related(exp);
282                 return NF_DROP;
283         }
284         return NF_ACCEPT;
285 }
286
287 static void __exit nf_nat_sip_fini(void)
288 {
289         rcu_assign_pointer(nf_nat_sip_hook, NULL);
290         rcu_assign_pointer(nf_nat_sdp_hook, NULL);
291         synchronize_rcu();
292 }
293
294 static int __init nf_nat_sip_init(void)
295 {
296         BUG_ON(rcu_dereference(nf_nat_sip_hook));
297         BUG_ON(rcu_dereference(nf_nat_sdp_hook));
298         rcu_assign_pointer(nf_nat_sip_hook, ip_nat_sip);
299         rcu_assign_pointer(nf_nat_sdp_hook, ip_nat_sdp);
300         return 0;
301 }
302
303 module_init(nf_nat_sip_init);
304 module_exit(nf_nat_sip_fini);