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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 | * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
5 | * |
6 | * This program is free software; you can redistribute it and/or |
7 | * modify it under the terms of the GNU General Public License |
8 | * as published by the Free Software Foundation; either version |
9 | * 2 of the License, or (at your option) any later version. |
10 | */ |
11 | |
12 | #include <linux/module.h> |
13 | #include <linux/moduleparam.h> |
14 | #include <linux/skbuff.h> |
15 | #include <linux/in.h> |
16 | #include <linux/ip.h> |
17 | #include <linux/tcp.h> |
18 | #include <linux/netfilter.h> |
19 | #include <linux/slab.h> |
20 | |
21 | #include <net/netfilter/nf_conntrack.h> |
22 | #include <net/netfilter/nf_conntrack_expect.h> |
23 | #include <net/netfilter/nf_conntrack_helper.h> |
24 | #include <linux/netfilter/nf_conntrack_irc.h> |
25 | |
26 | #define MAX_PORTS 8 |
27 | static unsigned short ports[MAX_PORTS]; |
28 | static unsigned int ports_c; |
29 | static unsigned int max_dcc_channels = 8; |
30 | static unsigned int dcc_timeout __read_mostly = 300; |
31 | /* This is slow, but it's simple. --RR */ |
32 | static char *irc_buffer; |
33 | static DEFINE_SPINLOCK(irc_buffer_lock); |
34 | |
35 | unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb, |
36 | enum ip_conntrack_info ctinfo, |
37 | unsigned int protoff, |
38 | unsigned int matchoff, |
39 | unsigned int matchlen, |
40 | struct nf_conntrack_expect *exp) __read_mostly; |
41 | EXPORT_SYMBOL_GPL(nf_nat_irc_hook); |
42 | |
43 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
44 | MODULE_DESCRIPTION("IRC (DCC) connection tracking helper"); |
45 | MODULE_LICENSE("GPL"); |
46 | MODULE_ALIAS("ip_conntrack_irc"); |
47 | MODULE_ALIAS_NFCT_HELPER("irc"); |
48 | |
49 | module_param_array(ports, ushort, &ports_c, 0400); |
50 | MODULE_PARM_DESC(ports, "port numbers of IRC servers"); |
51 | module_param(max_dcc_channels, uint, 0400); |
52 | MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " |
53 | "IRC session"); |
54 | module_param(dcc_timeout, uint, 0400); |
55 | MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels"); |
56 | |
57 | static const char *const dccprotos[] = { |
58 | "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " |
59 | }; |
60 | |
61 | #define MINMATCHLEN 5 |
62 | |
63 | /* tries to get the ip_addr and port out of a dcc command |
64 | * return value: -1 on failure, 0 on success |
65 | * data pointer to first byte of DCC command data |
66 | * data_end pointer to last byte of dcc command data |
67 | * ip returns parsed ip of dcc command |
68 | * port returns parsed port of dcc command |
69 | * ad_beg_p returns pointer to first byte of addr data |
70 | * ad_end_p returns pointer to last byte of addr data |
71 | */ |
72 | static 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 | /* at least 12: "AAAAAAAA P\1\n" */ |
78 | while (*data++ != ' ') |
79 | if (data > data_end - 12) |
80 | return -1; |
81 | |
82 | /* Make sure we have a newline character within the packet boundaries |
83 | * because simple_strtoul parses until the first invalid character. */ |
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 | /* skip blanks between ip and port */ |
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 | |
106 | static 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 | /* If packet is coming from IRC server */ |
126 | if (dir == IP_CT_DIR_REPLY) |
127 | return NF_ACCEPT; |
128 | |
129 | /* Until there's been traffic both ways, don't look in packets. */ |
130 | if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) |
131 | return NF_ACCEPT; |
132 | |
133 | /* Not a full tcp header? */ |
134 | th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); |
135 | if (th == NULL) |
136 | return NF_ACCEPT; |
137 | |
138 | /* No data? */ |
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 | BUG_ON(ib_ptr == NULL); |
147 | |
148 | data = ib_ptr; |
149 | data_limit = ib_ptr + skb->len - dataoff; |
150 | |
151 | /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24 |
152 | * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */ |
153 | while (data < data_limit - (19 + MINMATCHLEN)) { |
154 | if (memcmp(data, "\1DCC ", 5)) { |
155 | data++; |
156 | continue; |
157 | } |
158 | data += 5; |
159 | /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */ |
160 | |
161 | iph = ip_hdr(skb); |
162 | pr_debug("DCC found in master %pI4:%u %pI4:%u\n", |
163 | &iph->saddr, ntohs(th->source), |
164 | &iph->daddr, ntohs(th->dest)); |
165 | |
166 | for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { |
167 | if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { |
168 | /* no match */ |
169 | continue; |
170 | } |
171 | data += strlen(dccprotos[i]); |
172 | pr_debug("DCC %s detected\n", dccprotos[i]); |
173 | |
174 | /* we have at least |
175 | * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid |
176 | * data left (== 14/13 bytes) */ |
177 | if (parse_dcc(data, data_limit, &dcc_ip, |
178 | &dcc_port, &addr_beg_p, &addr_end_p)) { |
179 | pr_debug("unable to parse dcc command\n"); |
180 | continue; |
181 | } |
182 | |
183 | pr_debug("DCC bound ip/port: %pI4:%u\n", |
184 | &dcc_ip, dcc_port); |
185 | |
186 | /* dcc_ip can be the internal OR external (NAT'ed) IP */ |
187 | tuple = &ct->tuplehash[dir].tuple; |
188 | if (tuple->src.u3.ip != dcc_ip && |
189 | tuple->dst.u3.ip != dcc_ip) { |
190 | net_warn_ratelimited("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 | nf_ct_helper_log(skb, ct, |
199 | "cannot alloc expectation"); |
200 | ret = NF_DROP; |
201 | goto out; |
202 | } |
203 | tuple = &ct->tuplehash[!dir].tuple; |
204 | port = htons(dcc_port); |
205 | nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, |
206 | tuple->src.l3num, |
207 | NULL, &tuple->dst.u3, |
208 | IPPROTO_TCP, NULL, &port); |
209 | |
210 | nf_nat_irc = rcu_dereference(nf_nat_irc_hook); |
211 | if (nf_nat_irc && ct->status & IPS_NAT_MASK) |
212 | ret = nf_nat_irc(skb, ctinfo, protoff, |
213 | addr_beg_p - ib_ptr, |
214 | addr_end_p - addr_beg_p, |
215 | exp); |
216 | else if (nf_ct_expect_related(exp) != 0) { |
217 | nf_ct_helper_log(skb, ct, |
218 | "cannot add expectation"); |
219 | ret = NF_DROP; |
220 | } |
221 | nf_ct_expect_put(exp); |
222 | goto out; |
223 | } |
224 | } |
225 | out: |
226 | spin_unlock_bh(&irc_buffer_lock); |
227 | return ret; |
228 | } |
229 | |
230 | static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; |
231 | static struct nf_conntrack_expect_policy irc_exp_policy; |
232 | |
233 | static void nf_conntrack_irc_fini(void); |
234 | |
235 | static int __init nf_conntrack_irc_init(void) |
236 | { |
237 | int i, ret; |
238 | |
239 | if (max_dcc_channels < 1) { |
240 | printk(KERN_ERR "nf_ct_irc: max_dcc_channels must not be zero\n"); |
241 | return -EINVAL; |
242 | } |
243 | |
244 | irc_exp_policy.max_expected = max_dcc_channels; |
245 | irc_exp_policy.timeout = dcc_timeout; |
246 | |
247 | irc_buffer = kmalloc(65536, GFP_KERNEL); |
248 | if (!irc_buffer) |
249 | return -ENOMEM; |
250 | |
251 | /* If no port given, default to standard irc port */ |
252 | if (ports_c == 0) |
253 | ports[ports_c++] = IRC_PORT; |
254 | |
255 | for (i = 0; i < ports_c; i++) { |
256 | irc[i].tuple.src.l3num = AF_INET; |
257 | irc[i].tuple.src.u.tcp.port = htons(ports[i]); |
258 | irc[i].tuple.dst.protonum = IPPROTO_TCP; |
259 | irc[i].expect_policy = &irc_exp_policy; |
260 | irc[i].me = THIS_MODULE; |
261 | irc[i].help = help; |
262 | |
263 | if (ports[i] == IRC_PORT) |
264 | sprintf(irc[i].name, "irc"); |
265 | else |
266 | sprintf(irc[i].name, "irc-%u", i); |
267 | |
268 | ret = nf_conntrack_helper_register(&irc[i]); |
269 | if (ret) { |
270 | printk(KERN_ERR "nf_ct_irc: failed to register helper " |
271 | "for pf: %u port: %u\n", |
272 | irc[i].tuple.src.l3num, ports[i]); |
273 | nf_conntrack_irc_fini(); |
274 | return ret; |
275 | } |
276 | } |
277 | return 0; |
278 | } |
279 | |
280 | /* This function is intentionally _NOT_ defined as __exit, because |
281 | * it is needed by the init function */ |
282 | static void nf_conntrack_irc_fini(void) |
283 | { |
284 | int i; |
285 | |
286 | for (i = 0; i < ports_c; i++) |
287 | nf_conntrack_helper_unregister(&irc[i]); |
288 | kfree(irc_buffer); |
289 | } |
290 | |
291 | module_init(nf_conntrack_irc_init); |
292 | module_exit(nf_conntrack_irc_fini); |
293 |
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