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 |
25 | static unsigned short ports[MAX_PORTS]; |
26 | static unsigned 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 | |
33 | unsigned 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; |
39 | EXPORT_SYMBOL_GPL(nf_nat_irc_hook); |
40 | |
41 | #define HELPER_NAME "irc" |
42 | #define MAX_SEARCH_SIZE 4095 |
43 | |
44 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>" ); |
45 | MODULE_DESCRIPTION("IRC (DCC) connection tracking helper" ); |
46 | MODULE_LICENSE("GPL" ); |
47 | MODULE_ALIAS("ip_conntrack_irc" ); |
48 | MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); |
49 | |
50 | module_param_array(ports, ushort, &ports_c, 0400); |
51 | MODULE_PARM_DESC(ports, "port numbers of IRC servers" ); |
52 | module_param(max_dcc_channels, uint, 0400); |
53 | MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " |
54 | "IRC session" ); |
55 | module_param(dcc_timeout, uint, 0400); |
56 | MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels" ); |
57 | |
58 | static 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 | */ |
73 | static 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 | |
107 | static 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(p: data, q: " :" , size: 2)) { |
181 | data++; |
182 | continue; |
183 | } |
184 | data += 2; |
185 | |
186 | /* then check that place only for the DCC command */ |
187 | if (memcmp(p: data, q: "\1DCC " , size: 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(p: data, q: 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 | |
262 | static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; |
263 | static struct nf_conntrack_expect_policy irc_exp_policy; |
264 | |
265 | static 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 | |
307 | static void __exit nf_conntrack_irc_fini(void) |
308 | { |
309 | nf_conntrack_helpers_unregister(irc, ports_c); |
310 | kfree(objp: irc_buffer); |
311 | } |
312 | |
313 | module_init(nf_conntrack_irc_init); |
314 | module_exit(nf_conntrack_irc_fini); |
315 | |