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8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10#include <linux/module.h>
11#include <linux/moduleparam.h>
12#include <linux/skbuff.h>
13#include <linux/in.h>
14#include <linux/ip.h>
15#include <linux/tcp.h>
16#include <linux/netfilter.h>
17#include <linux/slab.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
25static unsigned short ports[MAX_PORTS];
26static unsigned int ports_c;
27static unsigned int max_dcc_channels = 8;
28static unsigned int dcc_timeout __read_mostly = 300;
29
30static char *irc_buffer;
31static DEFINE_SPINLOCK(irc_buffer_lock);
32
33unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb,
34 enum ip_conntrack_info ctinfo,
35 unsigned int protoff,
36 unsigned int matchoff,
37 unsigned int matchlen,
38 struct nf_conntrack_expect *exp) __read_mostly;
39EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
40
41#define HELPER_NAME "irc"
42
43MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
44MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
45MODULE_LICENSE("GPL");
46MODULE_ALIAS("ip_conntrack_irc");
47MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
48
49module_param_array(ports, ushort, &ports_c, 0400);
50MODULE_PARM_DESC(ports, "port numbers of IRC servers");
51module_param(max_dcc_channels, uint, 0400);
52MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
53 "IRC session");
54module_param(dcc_timeout, uint, 0400);
55MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
56
57static const char *const dccprotos[] = {
58 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
59};
60
61#define MINMATCHLEN 5
62
63
64
65
66
67
68
69
70
71
72static int parse_dcc(char *data, const char *data_end, __be32 *ip,
73 u_int16_t *port, char **ad_beg_p, char **ad_end_p)
74{
75 char *tmp;
76
77
78 while (*data++ != ' ')
79 if (data > data_end - 12)
80 return -1;
81
82
83
84 for (tmp = data; tmp <= data_end; tmp++)
85 if (*tmp == '\n')
86 break;
87 if (tmp > data_end || *tmp != '\n')
88 return -1;
89
90 *ad_beg_p = data;
91 *ip = cpu_to_be32(simple_strtoul(data, &data, 10));
92
93
94 while (*data == ' ') {
95 if (data >= data_end)
96 return -1;
97 data++;
98 }
99
100 *port = simple_strtoul(data, &data, 10);
101 *ad_end_p = data;
102
103 return 0;
104}
105
106static int help(struct sk_buff *skb, unsigned int protoff,
107 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
108{
109 unsigned int dataoff;
110 const struct iphdr *iph;
111 const struct tcphdr *th;
112 struct tcphdr _tcph;
113 const char *data_limit;
114 char *data, *ib_ptr;
115 int dir = CTINFO2DIR(ctinfo);
116 struct nf_conntrack_expect *exp;
117 struct nf_conntrack_tuple *tuple;
118 __be32 dcc_ip;
119 u_int16_t dcc_port;
120 __be16 port;
121 int i, ret = NF_ACCEPT;
122 char *addr_beg_p, *addr_end_p;
123 typeof(nf_nat_irc_hook) nf_nat_irc;
124
125
126 if (dir == IP_CT_DIR_REPLY)
127 return NF_ACCEPT;
128
129
130 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
131 return NF_ACCEPT;
132
133
134 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
135 if (th == NULL)
136 return NF_ACCEPT;
137
138
139 dataoff = protoff + th->doff*4;
140 if (dataoff >= skb->len)
141 return NF_ACCEPT;
142
143 spin_lock_bh(&irc_buffer_lock);
144 ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff,
145 irc_buffer);
146 if (!ib_ptr) {
147 spin_unlock_bh(&irc_buffer_lock);
148 return NF_ACCEPT;
149 }
150
151 data = ib_ptr;
152 data_limit = ib_ptr + skb->len - dataoff;
153
154
155
156 while (data < data_limit - (19 + MINMATCHLEN)) {
157 if (memcmp(data, "\1DCC ", 5)) {
158 data++;
159 continue;
160 }
161 data += 5;
162
163
164 iph = ip_hdr(skb);
165 pr_debug("DCC found in master %pI4:%u %pI4:%u\n",
166 &iph->saddr, ntohs(th->source),
167 &iph->daddr, ntohs(th->dest));
168
169 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
170 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
171
172 continue;
173 }
174 data += strlen(dccprotos[i]);
175 pr_debug("DCC %s detected\n", dccprotos[i]);
176
177
178
179
180 if (parse_dcc(data, data_limit, &dcc_ip,
181 &dcc_port, &addr_beg_p, &addr_end_p)) {
182 pr_debug("unable to parse dcc command\n");
183 continue;
184 }
185
186 pr_debug("DCC bound ip/port: %pI4:%u\n",
187 &dcc_ip, dcc_port);
188
189
190 tuple = &ct->tuplehash[dir].tuple;
191 if (tuple->src.u3.ip != dcc_ip &&
192 tuple->dst.u3.ip != dcc_ip) {
193 net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n",
194 &tuple->src.u3.ip,
195 &dcc_ip, dcc_port);
196 continue;
197 }
198
199 exp = nf_ct_expect_alloc(ct);
200 if (exp == NULL) {
201 nf_ct_helper_log(skb, ct,
202 "cannot alloc expectation");
203 ret = NF_DROP;
204 goto out;
205 }
206 tuple = &ct->tuplehash[!dir].tuple;
207 port = htons(dcc_port);
208 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
209 tuple->src.l3num,
210 NULL, &tuple->dst.u3,
211 IPPROTO_TCP, NULL, &port);
212
213 nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
214 if (nf_nat_irc && ct->status & IPS_NAT_MASK)
215 ret = nf_nat_irc(skb, ctinfo, protoff,
216 addr_beg_p - ib_ptr,
217 addr_end_p - addr_beg_p,
218 exp);
219 else if (nf_ct_expect_related(exp, 0) != 0) {
220 nf_ct_helper_log(skb, ct,
221 "cannot add expectation");
222 ret = NF_DROP;
223 }
224 nf_ct_expect_put(exp);
225 goto out;
226 }
227 }
228 out:
229 spin_unlock_bh(&irc_buffer_lock);
230 return ret;
231}
232
233static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
234static struct nf_conntrack_expect_policy irc_exp_policy;
235
236static int __init nf_conntrack_irc_init(void)
237{
238 int i, ret;
239
240 if (max_dcc_channels < 1) {
241 pr_err("max_dcc_channels must not be zero\n");
242 return -EINVAL;
243 }
244
245 if (max_dcc_channels > NF_CT_EXPECT_MAX_CNT) {
246 pr_err("max_dcc_channels must not be more than %u\n",
247 NF_CT_EXPECT_MAX_CNT);
248 return -EINVAL;
249 }
250
251 irc_exp_policy.max_expected = max_dcc_channels;
252 irc_exp_policy.timeout = dcc_timeout;
253
254 irc_buffer = kmalloc(65536, GFP_KERNEL);
255 if (!irc_buffer)
256 return -ENOMEM;
257
258
259 if (ports_c == 0)
260 ports[ports_c++] = IRC_PORT;
261
262 for (i = 0; i < ports_c; i++) {
263 nf_ct_helper_init(&irc[i], AF_INET, IPPROTO_TCP, HELPER_NAME,
264 IRC_PORT, ports[i], i, &irc_exp_policy,
265 0, help, NULL, THIS_MODULE);
266 }
267
268 ret = nf_conntrack_helpers_register(&irc[0], ports_c);
269 if (ret) {
270 pr_err("failed to register helpers\n");
271 kfree(irc_buffer);
272 return ret;
273 }
274
275 return 0;
276}
277
278static void __exit nf_conntrack_irc_fini(void)
279{
280 nf_conntrack_helpers_unregister(irc, ports_c);
281 kfree(irc_buffer);
282}
283
284module_init(nf_conntrack_irc_init);
285module_exit(nf_conntrack_irc_fini);
286
