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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]; | |
2f0d2f10 | 26 | static unsigned int ports_c; |
869f37d8 PM |
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 | ||
58c0fb0d | 53 | static const char *const dccprotos[] = { |
869f37d8 PM |
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 | */ | |
58c0fb0d | 68 | static int parse_dcc(char *data, const char *data_end, u_int32_t *ip, |
869f37d8 PM |
69 | u_int16_t *port, char **ad_beg_p, char **ad_end_p) |
70 | { | |
e3b802ba PM |
71 | char *tmp; |
72 | ||
869f37d8 PM |
73 | /* at least 12: "AAAAAAAA P\1\n" */ |
74 | while (*data++ != ' ') | |
75 | if (data > data_end - 12) | |
76 | return -1; | |
77 | ||
e3b802ba PM |
78 | /* Make sure we have a newline character within the packet boundaries |
79 | * because simple_strtoul parses until the first invalid character. */ | |
80 | for (tmp = data; tmp <= data_end; tmp++) | |
81 | if (*tmp == '\n') | |
82 | break; | |
83 | if (tmp > data_end || *tmp != '\n') | |
84 | return -1; | |
85 | ||
869f37d8 PM |
86 | *ad_beg_p = data; |
87 | *ip = simple_strtoul(data, &data, 10); | |
88 | ||
89 | /* skip blanks between ip and port */ | |
90 | while (*data == ' ') { | |
91 | if (data >= data_end) | |
92 | return -1; | |
93 | data++; | |
94 | } | |
95 | ||
96 | *port = simple_strtoul(data, &data, 10); | |
97 | *ad_end_p = data; | |
98 | ||
99 | return 0; | |
100 | } | |
101 | ||
3db05fea | 102 | static int help(struct sk_buff *skb, unsigned int protoff, |
869f37d8 PM |
103 | struct nf_conn *ct, enum ip_conntrack_info ctinfo) |
104 | { | |
105 | unsigned int dataoff; | |
58c0fb0d JE |
106 | const struct iphdr *iph; |
107 | const struct tcphdr *th; | |
108 | struct tcphdr _tcph; | |
109 | const char *data_limit; | |
110 | char *data, *ib_ptr; | |
869f37d8 PM |
111 | int dir = CTINFO2DIR(ctinfo); |
112 | struct nf_conntrack_expect *exp; | |
113 | struct nf_conntrack_tuple *tuple; | |
114 | u_int32_t dcc_ip; | |
115 | u_int16_t dcc_port; | |
116 | __be16 port; | |
117 | int i, ret = NF_ACCEPT; | |
118 | char *addr_beg_p, *addr_end_p; | |
119 | typeof(nf_nat_irc_hook) nf_nat_irc; | |
120 | ||
121 | /* If packet is coming from IRC server */ | |
122 | if (dir == IP_CT_DIR_REPLY) | |
123 | return NF_ACCEPT; | |
124 | ||
125 | /* Until there's been traffic both ways, don't look in packets. */ | |
126 | if (ctinfo != IP_CT_ESTABLISHED && | |
127 | ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) | |
128 | return NF_ACCEPT; | |
129 | ||
130 | /* Not a full tcp header? */ | |
3db05fea | 131 | th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); |
869f37d8 PM |
132 | if (th == NULL) |
133 | return NF_ACCEPT; | |
134 | ||
135 | /* No data? */ | |
136 | dataoff = protoff + th->doff*4; | |
3db05fea | 137 | if (dataoff >= skb->len) |
869f37d8 PM |
138 | return NF_ACCEPT; |
139 | ||
140 | spin_lock_bh(&irc_buffer_lock); | |
3db05fea | 141 | ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff, |
869f37d8 PM |
142 | irc_buffer); |
143 | BUG_ON(ib_ptr == NULL); | |
144 | ||
145 | data = ib_ptr; | |
3db05fea | 146 | data_limit = ib_ptr + skb->len - dataoff; |
869f37d8 PM |
147 | |
148 | /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24 | |
149 | * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */ | |
150 | while (data < data_limit - (19 + MINMATCHLEN)) { | |
151 | if (memcmp(data, "\1DCC ", 5)) { | |
152 | data++; | |
153 | continue; | |
154 | } | |
155 | data += 5; | |
156 | /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */ | |
157 | ||
3db05fea | 158 | iph = ip_hdr(skb); |
0d53778e PM |
159 | pr_debug("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u\n", |
160 | NIPQUAD(iph->saddr), ntohs(th->source), | |
161 | NIPQUAD(iph->daddr), ntohs(th->dest)); | |
869f37d8 PM |
162 | |
163 | for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { | |
164 | if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { | |
165 | /* no match */ | |
166 | continue; | |
167 | } | |
168 | data += strlen(dccprotos[i]); | |
0d53778e | 169 | pr_debug("DCC %s detected\n", dccprotos[i]); |
869f37d8 PM |
170 | |
171 | /* we have at least | |
172 | * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid | |
173 | * data left (== 14/13 bytes) */ | |
58c0fb0d | 174 | if (parse_dcc(data, data_limit, &dcc_ip, |
869f37d8 | 175 | &dcc_port, &addr_beg_p, &addr_end_p)) { |
0d53778e | 176 | pr_debug("unable to parse dcc command\n"); |
869f37d8 PM |
177 | continue; |
178 | } | |
0d53778e PM |
179 | pr_debug("DCC bound ip/port: %u.%u.%u.%u:%u\n", |
180 | HIPQUAD(dcc_ip), dcc_port); | |
869f37d8 PM |
181 | |
182 | /* dcc_ip can be the internal OR external (NAT'ed) IP */ | |
183 | tuple = &ct->tuplehash[dir].tuple; | |
184 | if (tuple->src.u3.ip != htonl(dcc_ip) && | |
185 | tuple->dst.u3.ip != htonl(dcc_ip)) { | |
186 | if (net_ratelimit()) | |
187 | printk(KERN_WARNING | |
188 | "Forged DCC command from " | |
189 | "%u.%u.%u.%u: %u.%u.%u.%u:%u\n", | |
190 | NIPQUAD(tuple->src.u3.ip), | |
191 | HIPQUAD(dcc_ip), dcc_port); | |
192 | continue; | |
193 | } | |
194 | ||
6823645d | 195 | exp = nf_ct_expect_alloc(ct); |
869f37d8 PM |
196 | if (exp == NULL) { |
197 | ret = NF_DROP; | |
198 | goto out; | |
199 | } | |
200 | tuple = &ct->tuplehash[!dir].tuple; | |
201 | port = htons(dcc_port); | |
6002f266 PM |
202 | nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, |
203 | tuple->src.l3num, | |
6823645d PM |
204 | NULL, &tuple->dst.u3, |
205 | IPPROTO_TCP, NULL, &port); | |
869f37d8 PM |
206 | |
207 | nf_nat_irc = rcu_dereference(nf_nat_irc_hook); | |
208 | if (nf_nat_irc && ct->status & IPS_NAT_MASK) | |
3db05fea | 209 | ret = nf_nat_irc(skb, ctinfo, |
869f37d8 PM |
210 | addr_beg_p - ib_ptr, |
211 | addr_end_p - addr_beg_p, | |
212 | exp); | |
6823645d | 213 | else if (nf_ct_expect_related(exp) != 0) |
869f37d8 | 214 | ret = NF_DROP; |
6823645d | 215 | nf_ct_expect_put(exp); |
869f37d8 PM |
216 | goto out; |
217 | } | |
218 | } | |
219 | out: | |
220 | spin_unlock_bh(&irc_buffer_lock); | |
221 | return ret; | |
222 | } | |
223 | ||
224 | static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; | |
225 | static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly; | |
6002f266 | 226 | static struct nf_conntrack_expect_policy irc_exp_policy; |
869f37d8 PM |
227 | |
228 | static void nf_conntrack_irc_fini(void); | |
229 | ||
230 | static int __init nf_conntrack_irc_init(void) | |
231 | { | |
232 | int i, ret; | |
233 | char *tmpname; | |
234 | ||
235 | if (max_dcc_channels < 1) { | |
236 | printk("nf_ct_irc: max_dcc_channels must not be zero\n"); | |
237 | return -EINVAL; | |
238 | } | |
239 | ||
6002f266 PM |
240 | irc_exp_policy.max_expected = max_dcc_channels; |
241 | irc_exp_policy.timeout = dcc_timeout; | |
242 | ||
869f37d8 PM |
243 | irc_buffer = kmalloc(65536, GFP_KERNEL); |
244 | if (!irc_buffer) | |
245 | return -ENOMEM; | |
246 | ||
247 | /* If no port given, default to standard irc port */ | |
248 | if (ports_c == 0) | |
249 | ports[ports_c++] = IRC_PORT; | |
250 | ||
251 | for (i = 0; i < ports_c; i++) { | |
252 | irc[i].tuple.src.l3num = AF_INET; | |
253 | irc[i].tuple.src.u.tcp.port = htons(ports[i]); | |
254 | irc[i].tuple.dst.protonum = IPPROTO_TCP; | |
6002f266 | 255 | irc[i].expect_policy = &irc_exp_policy; |
869f37d8 PM |
256 | irc[i].me = THIS_MODULE; |
257 | irc[i].help = help; | |
258 | ||
259 | tmpname = &irc_names[i][0]; | |
260 | if (ports[i] == IRC_PORT) | |
261 | sprintf(tmpname, "irc"); | |
262 | else | |
263 | sprintf(tmpname, "irc-%u", i); | |
264 | irc[i].name = tmpname; | |
265 | ||
266 | ret = nf_conntrack_helper_register(&irc[i]); | |
267 | if (ret) { | |
268 | printk("nf_ct_irc: failed to register helper " | |
269 | "for pf: %u port: %u\n", | |
270 | irc[i].tuple.src.l3num, ports[i]); | |
271 | nf_conntrack_irc_fini(); | |
272 | return ret; | |
273 | } | |
274 | } | |
275 | return 0; | |
276 | } | |
277 | ||
278 | /* This function is intentionally _NOT_ defined as __exit, because | |
279 | * it is needed by the init function */ | |
280 | static void nf_conntrack_irc_fini(void) | |
281 | { | |
282 | int i; | |
283 | ||
284 | for (i = 0; i < ports_c; i++) | |
285 | nf_conntrack_helper_unregister(&irc[i]); | |
286 | kfree(irc_buffer); | |
287 | } | |
288 | ||
289 | module_init(nf_conntrack_irc_init); | |
290 | module_exit(nf_conntrack_irc_fini); |