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 *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, char *data_end, u_int32_t *ip,
69 u_int16_t *port, char **ad_beg_p, char **ad_end_p)
70 {
71 /* at least 12: "AAAAAAAA P\1\n" */
72 while (*data++ != ' ')
73 if (data > data_end - 12)
74 return -1;
75
76 *ad_beg_p = data;
77 *ip = simple_strtoul(data, &data, 10);
78
79 /* skip blanks between ip and port */
80 while (*data == ' ') {
81 if (data >= data_end)
82 return -1;
83 data++;
84 }
85
86 *port = simple_strtoul(data, &data, 10);
87 *ad_end_p = data;
88
89 return 0;
90 }
91
92 static int help(struct sk_buff *skb, unsigned int protoff,
93 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
94 {
95 unsigned int dataoff;
96 struct iphdr *iph;
97 struct tcphdr _tcph, *th;
98 char *data, *data_limit, *ib_ptr;
99 int dir = CTINFO2DIR(ctinfo);
100 struct nf_conntrack_expect *exp;
101 struct nf_conntrack_tuple *tuple;
102 u_int32_t dcc_ip;
103 u_int16_t dcc_port;
104 __be16 port;
105 int i, ret = NF_ACCEPT;
106 char *addr_beg_p, *addr_end_p;
107 typeof(nf_nat_irc_hook) nf_nat_irc;
108
109 /* If packet is coming from IRC server */
110 if (dir == IP_CT_DIR_REPLY)
111 return NF_ACCEPT;
112
113 /* Until there's been traffic both ways, don't look in packets. */
114 if (ctinfo != IP_CT_ESTABLISHED &&
115 ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY)
116 return NF_ACCEPT;
117
118 /* Not a full tcp header? */
119 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
120 if (th == NULL)
121 return NF_ACCEPT;
122
123 /* No data? */
124 dataoff = protoff + th->doff*4;
125 if (dataoff >= skb->len)
126 return NF_ACCEPT;
127
128 spin_lock_bh(&irc_buffer_lock);
129 ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff,
130 irc_buffer);
131 BUG_ON(ib_ptr == NULL);
132
133 data = ib_ptr;
134 data_limit = ib_ptr + skb->len - dataoff;
135
136 /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
137 * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
138 while (data < data_limit - (19 + MINMATCHLEN)) {
139 if (memcmp(data, "\1DCC ", 5)) {
140 data++;
141 continue;
142 }
143 data += 5;
144 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
145
146 iph = ip_hdr(skb);
147 pr_debug("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u\n",
148 NIPQUAD(iph->saddr), ntohs(th->source),
149 NIPQUAD(iph->daddr), ntohs(th->dest));
150
151 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
152 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
153 /* no match */
154 continue;
155 }
156 data += strlen(dccprotos[i]);
157 pr_debug("DCC %s detected\n", dccprotos[i]);
158
159 /* we have at least
160 * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
161 * data left (== 14/13 bytes) */
162 if (parse_dcc((char *)data, data_limit, &dcc_ip,
163 &dcc_port, &addr_beg_p, &addr_end_p)) {
164 pr_debug("unable to parse dcc command\n");
165 continue;
166 }
167 pr_debug("DCC bound ip/port: %u.%u.%u.%u:%u\n",
168 HIPQUAD(dcc_ip), dcc_port);
169
170 /* dcc_ip can be the internal OR external (NAT'ed) IP */
171 tuple = &ct->tuplehash[dir].tuple;
172 if (tuple->src.u3.ip != htonl(dcc_ip) &&
173 tuple->dst.u3.ip != htonl(dcc_ip)) {
174 if (net_ratelimit())
175 printk(KERN_WARNING
176 "Forged DCC command from "
177 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
178 NIPQUAD(tuple->src.u3.ip),
179 HIPQUAD(dcc_ip), dcc_port);
180 continue;
181 }
182
183 exp = nf_ct_expect_alloc(ct);
184 if (exp == NULL) {
185 ret = NF_DROP;
186 goto out;
187 }
188 tuple = &ct->tuplehash[!dir].tuple;
189 port = htons(dcc_port);
190 nf_ct_expect_init(exp, tuple->src.l3num,
191 NULL, &tuple->dst.u3,
192 IPPROTO_TCP, NULL, &port);
193
194 nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
195 if (nf_nat_irc && ct->status & IPS_NAT_MASK)
196 ret = nf_nat_irc(skb, ctinfo,
197 addr_beg_p - ib_ptr,
198 addr_end_p - addr_beg_p,
199 exp);
200 else if (nf_ct_expect_related(exp) != 0)
201 ret = NF_DROP;
202 nf_ct_expect_put(exp);
203 goto out;
204 }
205 }
206 out:
207 spin_unlock_bh(&irc_buffer_lock);
208 return ret;
209 }
210
211 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
212 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
213
214 static void nf_conntrack_irc_fini(void);
215
216 static int __init nf_conntrack_irc_init(void)
217 {
218 int i, ret;
219 char *tmpname;
220
221 if (max_dcc_channels < 1) {
222 printk("nf_ct_irc: max_dcc_channels must not be zero\n");
223 return -EINVAL;
224 }
225
226 irc_buffer = kmalloc(65536, GFP_KERNEL);
227 if (!irc_buffer)
228 return -ENOMEM;
229
230 /* If no port given, default to standard irc port */
231 if (ports_c == 0)
232 ports[ports_c++] = IRC_PORT;
233
234 for (i = 0; i < ports_c; i++) {
235 irc[i].tuple.src.l3num = AF_INET;
236 irc[i].tuple.src.u.tcp.port = htons(ports[i]);
237 irc[i].tuple.dst.protonum = IPPROTO_TCP;
238 irc[i].max_expected = max_dcc_channels;
239 irc[i].timeout = dcc_timeout;
240 irc[i].me = THIS_MODULE;
241 irc[i].help = help;
242
243 tmpname = &irc_names[i][0];
244 if (ports[i] == IRC_PORT)
245 sprintf(tmpname, "irc");
246 else
247 sprintf(tmpname, "irc-%u", i);
248 irc[i].name = tmpname;
249
250 ret = nf_conntrack_helper_register(&irc[i]);
251 if (ret) {
252 printk("nf_ct_irc: failed to register helper "
253 "for pf: %u port: %u\n",
254 irc[i].tuple.src.l3num, ports[i]);
255 nf_conntrack_irc_fini();
256 return ret;
257 }
258 }
259 return 0;
260 }
261
262 /* This function is intentionally _NOT_ defined as __exit, because
263 * it is needed by the init function */
264 static void nf_conntrack_irc_fini(void)
265 {
266 int i;
267
268 for (i = 0; i < ports_c; i++)
269 nf_conntrack_helper_unregister(&irc[i]);
270 kfree(irc_buffer);
271 }
272
273 module_init(nf_conntrack_irc_init);
274 module_exit(nf_conntrack_irc_fini);
275
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