1// SPDX-License-Identifier: GPL-2.0-or-later
2/* IRC extension for IP connection tracking, Version 1.21
3 * (C) 2000-2002 by Harald Welte <laforge@gnumonks.org>
4 * based on RR's ip_conntrack_ftp.c
5 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
6 */
7
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/* This is slow, but it's simple. --RR */
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#define MAX_SEARCH_SIZE 4095
43
44MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
45MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
46MODULE_LICENSE("GPL");
47MODULE_ALIAS("ip_conntrack_irc");
48MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
49
50module_param_array(ports, ushort, &ports_c, 0400);
51MODULE_PARM_DESC(ports, "port numbers of IRC servers");
52module_param(max_dcc_channels, uint, 0400);
53MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
54 "IRC session");
55module_param(dcc_timeout, uint, 0400);
56MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
57
58static const char *const dccprotos[] = {
59 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
60};
61
62#define MINMATCHLEN 5
63
64/* tries to get the ip_addr and port out of a dcc command
65 * return value: -1 on failure, 0 on success
66 * data pointer to first byte of DCC command data
67 * data_end pointer to last byte of dcc command data
68 * ip returns parsed ip of dcc command
69 * port returns parsed port of dcc command
70 * ad_beg_p returns pointer to first byte of addr data
71 * ad_end_p returns pointer to last byte of addr data
72 */
73static int parse_dcc(char *data, const char *data_end, __be32 *ip,
74 u_int16_t *port, char **ad_beg_p, char **ad_end_p)
75{
76 char *tmp;
77
78 /* at least 12: "AAAAAAAA P\1\n" */
79 while (*data++ != ' ')
80 if (data > data_end - 12)
81 return -1;
82
83 /* Make sure we have a newline character within the packet boundaries
84 * because simple_strtoul parses until the first invalid character. */
85 for (tmp = data; tmp <= data_end; tmp++)
86 if (*tmp == '\n')
87 break;
88 if (tmp > data_end || *tmp != '\n')
89 return -1;
90
91 *ad_beg_p = data;
92 *ip = cpu_to_be32(simple_strtoul(data, &data, 10));
93
94 /* skip blanks between ip and port */
95 while (*data == ' ') {
96 if (data >= data_end)
97 return -1;
98 data++;
99 }
100
101 *port = simple_strtoul(data, &data, 10);
102 *ad_end_p = data;
103
104 return 0;
105}
106
107static int help(struct sk_buff *skb, unsigned int protoff,
108 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
109{
110 unsigned int dataoff;
111 const struct iphdr *iph;
112 const struct tcphdr *th;
113 struct tcphdr _tcph;
114 const char *data_limit;
115 char *data, *ib_ptr;
116 int dir = CTINFO2DIR(ctinfo);
117 struct nf_conntrack_expect *exp;
118 struct nf_conntrack_tuple *tuple;
119 __be32 dcc_ip;
120 u_int16_t dcc_port;
121 __be16 port;
122 int i, ret = NF_ACCEPT;
123 char *addr_beg_p, *addr_end_p;
124 typeof(nf_nat_irc_hook) nf_nat_irc;
125 unsigned int datalen;
126
127 /* If packet is coming from IRC server */
128 if (dir == IP_CT_DIR_REPLY)
129 return NF_ACCEPT;
130
131 /* Until there's been traffic both ways, don't look in packets. */
132 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
133 return NF_ACCEPT;
134
135 /* Not a full tcp header? */
136 th = skb_header_pointer(skb, offset: protoff, len: sizeof(_tcph), buffer: &_tcph);
137 if (th == NULL)
138 return NF_ACCEPT;
139
140 /* No data? */
141 dataoff = protoff + th->doff*4;
142 if (dataoff >= skb->len)
143 return NF_ACCEPT;
144
145 datalen = skb->len - dataoff;
146 if (datalen > MAX_SEARCH_SIZE)
147 datalen = MAX_SEARCH_SIZE;
148
149 spin_lock_bh(lock: &irc_buffer_lock);
150 ib_ptr = skb_header_pointer(skb, offset: dataoff, len: datalen,
151 buffer: irc_buffer);
152 if (!ib_ptr) {
153 spin_unlock_bh(lock: &irc_buffer_lock);
154 return NF_ACCEPT;
155 }
156
157 data = ib_ptr;
158 data_limit = ib_ptr + datalen;
159
160 /* Skip any whitespace */
161 while (data < data_limit - 10) {
162 if (*data == ' ' || *data == '\r' || *data == '\n')
163 data++;
164 else
165 break;
166 }
167
168 /* strlen("PRIVMSG x ")=10 */
169 if (data < data_limit - 10) {
170 if (strncasecmp(s1: "PRIVMSG ", s2: data, n: 8))
171 goto out;
172 data += 8;
173 }
174
175 /* strlen(" :\1DCC SENT t AAAAAAAA P\1\n")=26
176 * 7+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=26
177 */
178 while (data < data_limit - (21 + MINMATCHLEN)) {
179 /* Find first " :", the start of message */
180 if (memcmp(data, " :", 2)) {
181 data++;
182 continue;
183 }
184 data += 2;
185
186 /* then check that place only for the DCC command */
187 if (memcmp(data, "\1DCC ", 5))
188 goto out;
189 data += 5;
190 /* we have at least (21+MINMATCHLEN)-(2+5) bytes valid data left */
191
192 iph = ip_hdr(skb);
193 pr_debug("DCC found in master %pI4:%u %pI4:%u\n",
194 &iph->saddr, ntohs(th->source),
195 &iph->daddr, ntohs(th->dest));
196
197 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
198 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
199 /* no match */
200 continue;
201 }
202 data += strlen(dccprotos[i]);
203 pr_debug("DCC %s detected\n", dccprotos[i]);
204
205 /* we have at least
206 * (21+MINMATCHLEN)-7-dccprotos[i].matchlen bytes valid
207 * data left (== 14/13 bytes) */
208 if (parse_dcc(data, data_end: data_limit, ip: &dcc_ip,
209 port: &dcc_port, ad_beg_p: &addr_beg_p, ad_end_p: &addr_end_p)) {
210 pr_debug("unable to parse dcc command\n");
211 continue;
212 }
213
214 pr_debug("DCC bound ip/port: %pI4:%u\n",
215 &dcc_ip, dcc_port);
216
217 /* dcc_ip can be the internal OR external (NAT'ed) IP */
218 tuple = &ct->tuplehash[dir].tuple;
219 if ((tuple->src.u3.ip != dcc_ip &&
220 ct->tuplehash[!dir].tuple.dst.u3.ip != dcc_ip) ||
221 dcc_port == 0) {
222 net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n",
223 &tuple->src.u3.ip,
224 &dcc_ip, dcc_port);
225 continue;
226 }
227
228 exp = nf_ct_expect_alloc(me: ct);
229 if (exp == NULL) {
230 nf_ct_helper_log(skb, ct,
231 fmt: "cannot alloc expectation");
232 ret = NF_DROP;
233 goto out;
234 }
235 tuple = &ct->tuplehash[!dir].tuple;
236 port = htons(dcc_port);
237 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
238 tuple->src.l3num,
239 NULL, &tuple->dst.u3,
240 IPPROTO_TCP, NULL, &port);
241
242 nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
243 if (nf_nat_irc && ct->status & IPS_NAT_MASK)
244 ret = nf_nat_irc(skb, ctinfo, protoff,
245 addr_beg_p - ib_ptr,
246 addr_end_p - addr_beg_p,
247 exp);
248 else if (nf_ct_expect_related(expect: exp, flags: 0) != 0) {
249 nf_ct_helper_log(skb, ct,
250 fmt: "cannot add expectation");
251 ret = NF_DROP;
252 }
253 nf_ct_expect_put(exp);
254 goto out;
255 }
256 }
257 out:
258 spin_unlock_bh(lock: &irc_buffer_lock);
259 return ret;
260}
261
262static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
263static struct nf_conntrack_expect_policy irc_exp_policy;
264
265static int __init nf_conntrack_irc_init(void)
266{
267 int i, ret;
268
269 if (max_dcc_channels < 1) {
270 pr_err("max_dcc_channels must not be zero\n");
271 return -EINVAL;
272 }
273
274 if (max_dcc_channels > NF_CT_EXPECT_MAX_CNT) {
275 pr_err("max_dcc_channels must not be more than %u\n",
276 NF_CT_EXPECT_MAX_CNT);
277 return -EINVAL;
278 }
279
280 irc_exp_policy.max_expected = max_dcc_channels;
281 irc_exp_policy.timeout = dcc_timeout;
282
283 irc_buffer = kmalloc(MAX_SEARCH_SIZE + 1, GFP_KERNEL);
284 if (!irc_buffer)
285 return -ENOMEM;
286
287 /* If no port given, default to standard irc port */
288 if (ports_c == 0)
289 ports[ports_c++] = IRC_PORT;
290
291 for (i = 0; i < ports_c; i++) {
292 nf_ct_helper_init(helper: &irc[i], AF_INET, IPPROTO_TCP, HELPER_NAME,
293 IRC_PORT, spec_port: ports[i], id: i, exp_pol: &irc_exp_policy,
294 expect_class_max: 0, help, NULL, THIS_MODULE);
295 }
296
297 ret = nf_conntrack_helpers_register(&irc[0], ports_c);
298 if (ret) {
299 pr_err("failed to register helpers\n");
300 kfree(objp: irc_buffer);
301 return ret;
302 }
303
304 return 0;
305}
306
307static void __exit nf_conntrack_irc_fini(void)
308{
309 nf_conntrack_helpers_unregister(irc, ports_c);
310 kfree(objp: irc_buffer);
311}
312
313module_init(nf_conntrack_irc_init);
314module_exit(nf_conntrack_irc_fini);
315