20633fdf7e6bb48b48e485b9ba0d110ab1f8459b
[linux-2.6.git] / net / netfilter / nf_conntrack_irc.c
1 /* IRC extension for IP connection tracking, Version 1.21
2  * (C) 2000-2002 by Harald Welte <laforge@gnumonks.org>
3  * based on RR's ip_conntrack_ftp.c
4  *
5  * This program is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU General Public License
7  * as published by the Free Software Foundation; either version
8  * 2 of the License, or (at your option) any later version.
9  */
10
11 #include <linux/module.h>
12 #include <linux/moduleparam.h>
13 #include <linux/skbuff.h>
14 #include <linux/in.h>
15 #include <linux/ip.h>
16 #include <linux/tcp.h>
17 #include <linux/netfilter.h>
18
19 #include <net/netfilter/nf_conntrack.h>
20 #include <net/netfilter/nf_conntrack_expect.h>
21 #include <net/netfilter/nf_conntrack_helper.h>
22 #include <linux/netfilter/nf_conntrack_irc.h>
23
24 #define MAX_PORTS 8
25 static unsigned short ports[MAX_PORTS];
26 static unsigned int ports_c;
27 static unsigned int max_dcc_channels = 8;
28 static unsigned int dcc_timeout __read_mostly = 300;
29 /* This is slow, but it's simple. --RR */
30 static char *irc_buffer;
31 static DEFINE_SPINLOCK(irc_buffer_lock);
32
33 unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb,
34                                 enum ip_conntrack_info ctinfo,
35                                 unsigned int matchoff,
36                                 unsigned int matchlen,
37                                 struct nf_conntrack_expect *exp) __read_mostly;
38 EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
39
40 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
41 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
42 MODULE_LICENSE("GPL");
43 MODULE_ALIAS("ip_conntrack_irc");
44
45 module_param_array(ports, ushort, &ports_c, 0400);
46 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
47 module_param(max_dcc_channels, uint, 0400);
48 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
49                                    "IRC session");
50 module_param(dcc_timeout, uint, 0400);
51 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
52
53 static const char *const dccprotos[] = {
54         "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
55 };
56
57 #define MINMATCHLEN     5
58
59 /* tries to get the ip_addr and port out of a dcc command
60  * return value: -1 on failure, 0 on success
61  *      data            pointer to first byte of DCC command data
62  *      data_end        pointer to last byte of dcc command data
63  *      ip              returns parsed ip of dcc command
64  *      port            returns parsed port of dcc command
65  *      ad_beg_p        returns pointer to first byte of addr data
66  *      ad_end_p        returns pointer to last byte of addr data
67  */
68 static int parse_dcc(char *data, const char *data_end, u_int32_t *ip,
69                      u_int16_t *port, char **ad_beg_p, char **ad_end_p)
70 {
71         char *tmp;
72
73         /* at least 12: "AAAAAAAA P\1\n" */
74         while (*data++ != ' ')
75                 if (data > data_end - 12)
76                         return -1;
77
78         /* Make sure we have a newline character within the packet boundaries
79          * because simple_strtoul parses until the first invalid character. */
80         for (tmp = data; tmp <= data_end; tmp++)
81                 if (*tmp == '\n')
82                         break;
83         if (tmp > data_end || *tmp != '\n')
84                 return -1;
85
86         *ad_beg_p = data;
87         *ip = simple_strtoul(data, &data, 10);
88
89         /* skip blanks between ip and port */
90         while (*data == ' ') {
91                 if (data >= data_end)
92                         return -1;
93                 data++;
94         }
95
96         *port = simple_strtoul(data, &data, 10);
97         *ad_end_p = data;
98
99         return 0;
100 }
101
102 static int help(struct sk_buff *skb, unsigned int protoff,
103                 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
104 {
105         unsigned int dataoff;
106         const struct iphdr *iph;
107         const struct tcphdr *th;
108         struct tcphdr _tcph;
109         const char *data_limit;
110         char *data, *ib_ptr;
111         int dir = CTINFO2DIR(ctinfo);
112         struct nf_conntrack_expect *exp;
113         struct nf_conntrack_tuple *tuple;
114         u_int32_t dcc_ip;
115         u_int16_t dcc_port;
116         __be16 port;
117         int i, ret = NF_ACCEPT;
118         char *addr_beg_p, *addr_end_p;
119         typeof(nf_nat_irc_hook) nf_nat_irc;
120
121         /* If packet is coming from IRC server */
122         if (dir == IP_CT_DIR_REPLY)
123                 return NF_ACCEPT;
124
125         /* Until there's been traffic both ways, don't look in packets. */
126         if (ctinfo != IP_CT_ESTABLISHED &&
127             ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY)
128                 return NF_ACCEPT;
129
130         /* Not a full tcp header? */
131         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
132         if (th == NULL)
133                 return NF_ACCEPT;
134
135         /* No data? */
136         dataoff = protoff + th->doff*4;
137         if (dataoff >= skb->len)
138                 return NF_ACCEPT;
139
140         spin_lock_bh(&irc_buffer_lock);
141         ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff,
142                                     irc_buffer);
143         BUG_ON(ib_ptr == NULL);
144
145         data = ib_ptr;
146         data_limit = ib_ptr + skb->len - dataoff;
147
148         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
149          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
150         while (data < data_limit - (19 + MINMATCHLEN)) {
151                 if (memcmp(data, "\1DCC ", 5)) {
152                         data++;
153                         continue;
154                 }
155                 data += 5;
156                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
157
158                 iph = ip_hdr(skb);
159                 pr_debug("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u\n",
160                          NIPQUAD(iph->saddr), ntohs(th->source),
161                          NIPQUAD(iph->daddr), ntohs(th->dest));
162
163                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
164                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
165                                 /* no match */
166                                 continue;
167                         }
168                         data += strlen(dccprotos[i]);
169                         pr_debug("DCC %s detected\n", dccprotos[i]);
170
171                         /* we have at least
172                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
173                          * data left (== 14/13 bytes) */
174                         if (parse_dcc(data, data_limit, &dcc_ip,
175                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
176                                 pr_debug("unable to parse dcc command\n");
177                                 continue;
178                         }
179                         pr_debug("DCC bound ip/port: %u.%u.%u.%u:%u\n",
180                                  HIPQUAD(dcc_ip), dcc_port);
181
182                         /* dcc_ip can be the internal OR external (NAT'ed) IP */
183                         tuple = &ct->tuplehash[dir].tuple;
184                         if (tuple->src.u3.ip != htonl(dcc_ip) &&
185                             tuple->dst.u3.ip != htonl(dcc_ip)) {
186                                 if (net_ratelimit())
187                                         printk(KERN_WARNING
188                                                 "Forged DCC command from "
189                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
190                                                 NIPQUAD(tuple->src.u3.ip),
191                                                 HIPQUAD(dcc_ip), dcc_port);
192                                 continue;
193                         }
194
195                         exp = nf_ct_expect_alloc(ct);
196                         if (exp == NULL) {
197                                 ret = NF_DROP;
198                                 goto out;
199                         }
200                         tuple = &ct->tuplehash[!dir].tuple;
201                         port = htons(dcc_port);
202                         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
203                                           tuple->src.l3num,
204                                           NULL, &tuple->dst.u3,
205                                           IPPROTO_TCP, NULL, &port);
206
207                         nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
208                         if (nf_nat_irc && ct->status & IPS_NAT_MASK)
209                                 ret = nf_nat_irc(skb, ctinfo,
210                                                  addr_beg_p - ib_ptr,
211                                                  addr_end_p - addr_beg_p,
212                                                  exp);
213                         else if (nf_ct_expect_related(exp) != 0)
214                                 ret = NF_DROP;
215                         nf_ct_expect_put(exp);
216                         goto out;
217                 }
218         }
219  out:
220         spin_unlock_bh(&irc_buffer_lock);
221         return ret;
222 }
223
224 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
225 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
226 static struct nf_conntrack_expect_policy irc_exp_policy;
227
228 static void nf_conntrack_irc_fini(void);
229
230 static int __init nf_conntrack_irc_init(void)
231 {
232         int i, ret;
233         char *tmpname;
234
235         if (max_dcc_channels < 1) {
236                 printk("nf_ct_irc: max_dcc_channels must not be zero\n");
237                 return -EINVAL;
238         }
239
240         irc_exp_policy.max_expected = max_dcc_channels;
241         irc_exp_policy.timeout = dcc_timeout;
242
243         irc_buffer = kmalloc(65536, GFP_KERNEL);
244         if (!irc_buffer)
245                 return -ENOMEM;
246
247         /* If no port given, default to standard irc port */
248         if (ports_c == 0)
249                 ports[ports_c++] = IRC_PORT;
250
251         for (i = 0; i < ports_c; i++) {
252                 irc[i].tuple.src.l3num = AF_INET;
253                 irc[i].tuple.src.u.tcp.port = htons(ports[i]);
254                 irc[i].tuple.dst.protonum = IPPROTO_TCP;
255                 irc[i].expect_policy = &irc_exp_policy;
256                 irc[i].me = THIS_MODULE;
257                 irc[i].help = help;
258
259                 tmpname = &irc_names[i][0];
260                 if (ports[i] == IRC_PORT)
261                         sprintf(tmpname, "irc");
262                 else
263                         sprintf(tmpname, "irc-%u", i);
264                 irc[i].name = tmpname;
265
266                 ret = nf_conntrack_helper_register(&irc[i]);
267                 if (ret) {
268                         printk("nf_ct_irc: failed to register helper "
269                                "for pf: %u port: %u\n",
270                                irc[i].tuple.src.l3num, ports[i]);
271                         nf_conntrack_irc_fini();
272                         return ret;
273                 }
274         }
275         return 0;
276 }
277
278 /* This function is intentionally _NOT_ defined as __exit, because
279  * it is needed by the init function */
280 static void nf_conntrack_irc_fini(void)
281 {
282         int i;
283
284         for (i = 0; i < ports_c; i++)
285                 nf_conntrack_helper_unregister(&irc[i]);
286         kfree(irc_buffer);
287 }
288
289 module_init(nf_conntrack_irc_init);
290 module_exit(nf_conntrack_irc_fini);