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869f37d8 PM |
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> | |
0d53778e | 15 | #include <linux/ip.h> |
869f37d8 PM |
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 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 | ||
3db05fea | 33 | unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb, |
869f37d8 PM |
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 | ||
869f37d8 PM |
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 | ||
3db05fea | 92 | static int help(struct sk_buff *skb, unsigned int protoff, |
869f37d8 PM |
93 | struct nf_conn *ct, enum ip_conntrack_info ctinfo) |
94 | { | |
95 | unsigned int dataoff; | |
0d53778e | 96 | struct iphdr *iph; |
869f37d8 PM |
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? */ | |
3db05fea | 119 | th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); |
869f37d8 PM |
120 | if (th == NULL) |
121 | return NF_ACCEPT; | |
122 | ||
123 | /* No data? */ | |
124 | dataoff = protoff + th->doff*4; | |
3db05fea | 125 | if (dataoff >= skb->len) |
869f37d8 PM |
126 | return NF_ACCEPT; |
127 | ||
128 | spin_lock_bh(&irc_buffer_lock); | |
3db05fea | 129 | ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff, |
869f37d8 PM |
130 | irc_buffer); |
131 | BUG_ON(ib_ptr == NULL); | |
132 | ||
133 | data = ib_ptr; | |
3db05fea | 134 | data_limit = ib_ptr + skb->len - dataoff; |
869f37d8 PM |
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 | ||
3db05fea | 146 | iph = ip_hdr(skb); |
0d53778e PM |
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)); | |
869f37d8 PM |
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]); | |
0d53778e | 157 | pr_debug("DCC %s detected\n", dccprotos[i]); |
869f37d8 PM |
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)) { | |
0d53778e | 164 | pr_debug("unable to parse dcc command\n"); |
869f37d8 PM |
165 | continue; |
166 | } | |
0d53778e PM |
167 | pr_debug("DCC bound ip/port: %u.%u.%u.%u:%u\n", |
168 | HIPQUAD(dcc_ip), dcc_port); | |
869f37d8 PM |
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 | ||
6823645d | 183 | exp = nf_ct_expect_alloc(ct); |
869f37d8 PM |
184 | if (exp == NULL) { |
185 | ret = NF_DROP; | |
186 | goto out; | |
187 | } | |
188 | tuple = &ct->tuplehash[!dir].tuple; | |
189 | port = htons(dcc_port); | |
6823645d PM |
190 | nf_ct_expect_init(exp, tuple->src.l3num, |
191 | NULL, &tuple->dst.u3, | |
192 | IPPROTO_TCP, NULL, &port); | |
869f37d8 PM |
193 | |
194 | nf_nat_irc = rcu_dereference(nf_nat_irc_hook); | |
195 | if (nf_nat_irc && ct->status & IPS_NAT_MASK) | |
3db05fea | 196 | ret = nf_nat_irc(skb, ctinfo, |
869f37d8 PM |
197 | addr_beg_p - ib_ptr, |
198 | addr_end_p - addr_beg_p, | |
199 | exp); | |
6823645d | 200 | else if (nf_ct_expect_related(exp) != 0) |
869f37d8 | 201 | ret = NF_DROP; |
6823645d | 202 | nf_ct_expect_put(exp); |
869f37d8 PM |
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; | |
869f37d8 PM |
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); |