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Linux/net/netfilter/nf_conntrack_irc.c

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

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