1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* IRC extension for TCP NAT alteration.
3 *
4 * (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
5 * (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
6 * based on a copy of RR's ip_nat_ftp.c
7 */
8
9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11 #include <linux/module.h>
12 #include <linux/moduleparam.h>
13 #include <linux/tcp.h>
14 #include <linux/kernel.h>
15
16 #include <net/netfilter/nf_nat.h>
17 #include <net/netfilter/nf_nat_helper.h>
18 #include <net/netfilter/nf_conntrack_helper.h>
19 #include <net/netfilter/nf_conntrack_expect.h>
20 #include <linux/netfilter/nf_conntrack_irc.h>
21
22 #define NAT_HELPER_NAME "irc"
23
24 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
25 MODULE_DESCRIPTION("IRC (DCC) NAT helper");
26 MODULE_LICENSE("GPL");
27 MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME);
28
29 static struct nf_conntrack_nat_helper nat_helper_irc =
30 NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME);
31
help(struct sk_buff * skb,enum ip_conntrack_info ctinfo,unsigned int protoff,unsigned int matchoff,unsigned int matchlen,struct nf_conntrack_expect * exp)32 static unsigned int help(struct sk_buff *skb,
33 enum ip_conntrack_info ctinfo,
34 unsigned int protoff,
35 unsigned int matchoff,
36 unsigned int matchlen,
37 struct nf_conntrack_expect *exp)
38 {
39 char buffer[sizeof("4294967296 65635")];
40 struct nf_conn *ct = exp->master;
41 union nf_inet_addr newaddr;
42 u_int16_t port;
43
44 /* Reply comes from server. */
45 newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3;
46
47 exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
48 exp->dir = IP_CT_DIR_REPLY;
49 exp->expectfn = nf_nat_follow_master;
50
51 /* Try to get same port: if not, try to change it. */
52 for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
53 int ret;
54
55 exp->tuple.dst.u.tcp.port = htons(port);
56 ret = nf_ct_expect_related(exp, 0);
57 if (ret == 0)
58 break;
59 else if (ret != -EBUSY) {
60 port = 0;
61 break;
62 }
63 }
64
65 if (port == 0) {
66 nf_ct_helper_log(skb, ct, "all ports in use");
67 return NF_DROP;
68 }
69
70 /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27
71 * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28
72 * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26
73 * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26
74 * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27
75 *
76 * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits,
77 * 255.255.255.255==4294967296, 10 digits)
78 * P: bound port (min 1 d, max 5d (65635))
79 * F: filename (min 1 d )
80 * S: size (min 1 d )
81 * 0x01, \n: terminators
82 */
83 /* AAA = "us", ie. where server normally talks to. */
84 snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port);
85 pr_debug("inserting '%s' == %pI4, port %u\n",
86 buffer, &newaddr.ip, port);
87
88 if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
89 matchlen, buffer, strlen(buffer))) {
90 nf_ct_helper_log(skb, ct, "cannot mangle packet");
91 nf_ct_unexpect_related(exp);
92 return NF_DROP;
93 }
94
95 return NF_ACCEPT;
96 }
97
nf_nat_irc_fini(void)98 static void __exit nf_nat_irc_fini(void)
99 {
100 nf_nat_helper_unregister(&nat_helper_irc);
101 RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
102 synchronize_rcu();
103 }
104
nf_nat_irc_init(void)105 static int __init nf_nat_irc_init(void)
106 {
107 BUG_ON(nf_nat_irc_hook != NULL);
108 nf_nat_helper_register(&nat_helper_irc);
109 RCU_INIT_POINTER(nf_nat_irc_hook, help);
110 return 0;
111 }
112
113 /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
warn_set(const char * val,const struct kernel_param * kp)114 static int warn_set(const char *val, const struct kernel_param *kp)
115 {
116 pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
117 return 0;
118 }
119 module_param_call(ports, warn_set, NULL, NULL, 0);
120
121 module_init(nf_nat_irc_init);
122 module_exit(nf_nat_irc_fini);
123