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 #include <linux/slab.h>
19
20 #include <net/netfilter/nf_conntrack.h>
21 #include <net/netfilter/nf_conntrack_expect.h>
22 #include <net/netfilter/nf_conntrack_helper.h>
23 #include <linux/netfilter/nf_conntrack_irc.h>
24
25 #define MAX_PORTS 8
26 static unsigned short ports[MAX_PORTS];
27 static unsigned int ports_c;
28 static unsigned int max_dcc_channels = 8;
29 static unsigned int dcc_timeout __read_mostly = 300;
30 /* This is slow, but it's simple. --RR */
31 static char *irc_buffer;
32 static DEFINE_SPINLOCK(irc_buffer_lock);
33
34 unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb,
35 enum ip_conntrack_info ctinfo,
36 unsigned int matchoff,
37 unsigned int matchlen,
38 struct nf_conntrack_expect *exp) __read_mostly;
39 EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
40
41 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
42 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
43 MODULE_LICENSE("GPL");
44 MODULE_ALIAS("ip_conntrack_irc");
45 MODULE_ALIAS_NFCT_HELPER("irc");
46
47 module_param_array(ports, ushort, &ports_c, 0400);
48 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
49 module_param(max_dcc_channels, uint, 0400);
50 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
51 "IRC session");
52 module_param(dcc_timeout, uint, 0400);
53 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
54
55 static const char *const dccprotos[] = {
56 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
57 };
58
59 #define MINMATCHLEN 5
60
61 /* tries to get the ip_addr and port out of a dcc command
62 * return value: -1 on failure, 0 on success
63 * data pointer to first byte of DCC command data
64 * data_end pointer to last byte of dcc command data
65 * ip returns parsed ip of dcc command
66 * port returns parsed port of dcc command
67 * ad_beg_p returns pointer to first byte of addr data
68 * ad_end_p returns pointer to last byte of addr data
69 */
parse_dcc(char * data,const char * data_end,__be32 * ip,u_int16_t * port,char ** ad_beg_p,char ** ad_end_p)70 static int parse_dcc(char *data, const char *data_end, __be32 *ip,
71 u_int16_t *port, char **ad_beg_p, char **ad_end_p)
72 {
73 char *tmp;
74
75 /* at least 12: "AAAAAAAA P\1\n" */
76 while (*data++ != ' ')
77 if (data > data_end - 12)
78 return -1;
79
80 /* Make sure we have a newline character within the packet boundaries
81 * because simple_strtoul parses until the first invalid character. */
82 for (tmp = data; tmp <= data_end; tmp++)
83 if (*tmp == '\n')
84 break;
85 if (tmp > data_end || *tmp != '\n')
86 return -1;
87
88 *ad_beg_p = data;
89 *ip = cpu_to_be32(simple_strtoul(data, &data, 10));
90
91 /* skip blanks between ip and port */
92 while (*data == ' ') {
93 if (data >= data_end)
94 return -1;
95 data++;
96 }
97
98 *port = simple_strtoul(data, &data, 10);
99 *ad_end_p = data;
100
101 return 0;
102 }
103
help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)104 static int help(struct sk_buff *skb, unsigned int protoff,
105 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
106 {
107 unsigned int dataoff;
108 const struct iphdr *iph;
109 const struct tcphdr *th;
110 struct tcphdr _tcph;
111 const char *data_limit;
112 char *data, *ib_ptr;
113 int dir = CTINFO2DIR(ctinfo);
114 struct nf_conntrack_expect *exp;
115 struct nf_conntrack_tuple *tuple;
116 __be32 dcc_ip;
117 u_int16_t dcc_port;
118 __be16 port;
119 int i, ret = NF_ACCEPT;
120 char *addr_beg_p, *addr_end_p;
121 typeof(nf_nat_irc_hook) nf_nat_irc;
122
123 /* If packet is coming from IRC server */
124 if (dir == IP_CT_DIR_REPLY)
125 return NF_ACCEPT;
126
127 /* Until there's been traffic both ways, don't look in packets. */
128 if (ctinfo != IP_CT_ESTABLISHED &&
129 ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY)
130 return NF_ACCEPT;
131
132 /* Not a full tcp header? */
133 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
134 if (th == NULL)
135 return NF_ACCEPT;
136
137 /* No data? */
138 dataoff = protoff + th->doff*4;
139 if (dataoff >= skb->len)
140 return NF_ACCEPT;
141
142 spin_lock_bh(&irc_buffer_lock);
143 ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff,
144 irc_buffer);
145 BUG_ON(ib_ptr == NULL);
146
147 data = ib_ptr;
148 data_limit = ib_ptr + skb->len - dataoff;
149
150 /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
151 * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
152 while (data < data_limit - (19 + MINMATCHLEN)) {
153 if (memcmp(data, "\1DCC ", 5)) {
154 data++;
155 continue;
156 }
157 data += 5;
158 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
159
160 iph = ip_hdr(skb);
161 pr_debug("DCC found in master %pI4:%u %pI4:%u\n",
162 &iph->saddr, ntohs(th->source),
163 &iph->daddr, ntohs(th->dest));
164
165 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
166 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
167 /* no match */
168 continue;
169 }
170 data += strlen(dccprotos[i]);
171 pr_debug("DCC %s detected\n", dccprotos[i]);
172
173 /* we have at least
174 * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
175 * data left (== 14/13 bytes) */
176 if (parse_dcc(data, data_limit, &dcc_ip,
177 &dcc_port, &addr_beg_p, &addr_end_p)) {
178 pr_debug("unable to parse dcc command\n");
179 continue;
180 }
181
182 pr_debug("DCC bound ip/port: %pI4:%u\n",
183 &dcc_ip, dcc_port);
184
185 /* dcc_ip can be the internal OR external (NAT'ed) IP */
186 tuple = &ct->tuplehash[dir].tuple;
187 if (tuple->src.u3.ip != dcc_ip &&
188 tuple->dst.u3.ip != dcc_ip) {
189 if (net_ratelimit())
190 printk(KERN_WARNING
191 "Forged DCC command from %pI4: %pI4:%u\n",
192 &tuple->src.u3.ip,
193 &dcc_ip, dcc_port);
194 continue;
195 }
196
197 exp = nf_ct_expect_alloc(ct);
198 if (exp == NULL) {
199 ret = NF_DROP;
200 goto out;
201 }
202 tuple = &ct->tuplehash[!dir].tuple;
203 port = htons(dcc_port);
204 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
205 tuple->src.l3num,
206 NULL, &tuple->dst.u3,
207 IPPROTO_TCP, NULL, &port);
208
209 nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
210 if (nf_nat_irc && ct->status & IPS_NAT_MASK)
211 ret = nf_nat_irc(skb, ctinfo,
212 addr_beg_p - ib_ptr,
213 addr_end_p - addr_beg_p,
214 exp);
215 else if (nf_ct_expect_related(exp) != 0)
216 ret = NF_DROP;
217 nf_ct_expect_put(exp);
218 goto out;
219 }
220 }
221 out:
222 spin_unlock_bh(&irc_buffer_lock);
223 return ret;
224 }
225
226 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
227 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
228 static struct nf_conntrack_expect_policy irc_exp_policy;
229
230 static void nf_conntrack_irc_fini(void);
231
nf_conntrack_irc_init(void)232 static int __init nf_conntrack_irc_init(void)
233 {
234 int i, ret;
235 char *tmpname;
236
237 if (max_dcc_channels < 1) {
238 printk(KERN_ERR "nf_ct_irc: max_dcc_channels must not be zero\n");
239 return -EINVAL;
240 }
241
242 irc_exp_policy.max_expected = max_dcc_channels;
243 irc_exp_policy.timeout = dcc_timeout;
244
245 irc_buffer = kmalloc(65536, GFP_KERNEL);
246 if (!irc_buffer)
247 return -ENOMEM;
248
249 /* If no port given, default to standard irc port */
250 if (ports_c == 0)
251 ports[ports_c++] = IRC_PORT;
252
253 for (i = 0; i < ports_c; i++) {
254 irc[i].tuple.src.l3num = AF_INET;
255 irc[i].tuple.src.u.tcp.port = htons(ports[i]);
256 irc[i].tuple.dst.protonum = IPPROTO_TCP;
257 irc[i].expect_policy = &irc_exp_policy;
258 irc[i].me = THIS_MODULE;
259 irc[i].help = help;
260
261 tmpname = &irc_names[i][0];
262 if (ports[i] == IRC_PORT)
263 sprintf(tmpname, "irc");
264 else
265 sprintf(tmpname, "irc-%u", i);
266 irc[i].name = tmpname;
267
268 ret = nf_conntrack_helper_register(&irc[i]);
269 if (ret) {
270 printk(KERN_ERR "nf_ct_irc: failed to register helper "
271 "for pf: %u port: %u\n",
272 irc[i].tuple.src.l3num, ports[i]);
273 nf_conntrack_irc_fini();
274 return ret;
275 }
276 }
277 return 0;
278 }
279
280 /* This function is intentionally _NOT_ defined as __exit, because
281 * it is needed by the init function */
nf_conntrack_irc_fini(void)282 static void nf_conntrack_irc_fini(void)
283 {
284 int i;
285
286 for (i = 0; i < ports_c; i++)
287 nf_conntrack_helper_unregister(&irc[i]);
288 kfree(irc_buffer);
289 }
290
291 module_init(nf_conntrack_irc_init);
292 module_exit(nf_conntrack_irc_fini);
293