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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
26static unsigned short ports[MAX_PORTS];
27static unsigned int ports_c;
28static unsigned int max_dcc_channels = 8;
29static unsigned int dcc_timeout __read_mostly = 300;
30
31static char *irc_buffer;
32static DEFINE_SPINLOCK(irc_buffer_lock);
33
34unsigned 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;
39EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
40
41MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
42MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
43MODULE_LICENSE("GPL");
44MODULE_ALIAS("ip_conntrack_irc");
45MODULE_ALIAS_NFCT_HELPER("irc");
46
47module_param_array(ports, ushort, &ports_c, 0400);
48MODULE_PARM_DESC(ports, "port numbers of IRC servers");
49module_param(max_dcc_channels, uint, 0400);
50MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
51 "IRC session");
52module_param(dcc_timeout, uint, 0400);
53MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
54
55static const char *const dccprotos[] = {
56 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
57};
58
59#define MINMATCHLEN 5
60
61
62
63
64
65
66
67
68
69
70static 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
76 while (*data++ != ' ')
77 if (data > data_end - 12)
78 return -1;
79
80
81
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
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
104static 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
124 if (dir == IP_CT_DIR_REPLY)
125 return NF_ACCEPT;
126
127
128 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
129 return NF_ACCEPT;
130
131
132 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
133 if (th == NULL)
134 return NF_ACCEPT;
135
136
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
150
151 while (data < data_limit - (19 + MINMATCHLEN)) {
152 if (memcmp(data, "\1DCC ", 5)) {
153 data++;
154 continue;
155 }
156 data += 5;
157
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
167 continue;
168 }
169 data += strlen(dccprotos[i]);
170 pr_debug("DCC %s detected\n", dccprotos[i]);
171
172
173
174
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
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
225static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
226static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
227static struct nf_conntrack_expect_policy irc_exp_policy;
228
229static void nf_conntrack_irc_fini(void);
230
231static int __init nf_conntrack_irc_init(void)
232{
233 int i, ret;
234 char *tmpname;
235
236 if (max_dcc_channels < 1) {
237 printk(KERN_ERR "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
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(KERN_ERR "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
280
281static 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
290module_init(nf_conntrack_irc_init);
291module_exit(nf_conntrack_irc_fini);
292
