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 | |
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 | port = nf_nat_exp_find_port(exp, |
52 | ntohs(exp->saved_proto.tcp.port)); |
53 | if (port == 0) { |
54 | nf_ct_helper_log(skb, ct, fmt: "all ports in use" ); |
55 | return NF_DROP; |
56 | } |
57 | |
58 | /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27 |
59 | * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28 |
60 | * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26 |
61 | * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26 |
62 | * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27 |
63 | * |
64 | * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits, |
65 | * 255.255.255.255==4294967296, 10 digits) |
66 | * P: bound port (min 1 d, max 5d (65635)) |
67 | * F: filename (min 1 d ) |
68 | * S: size (min 1 d ) |
69 | * 0x01, \n: terminators |
70 | */ |
71 | /* AAA = "us", ie. where server normally talks to. */ |
72 | snprintf(buf: buffer, size: sizeof(buffer), fmt: "%u %u" , ntohl(newaddr.ip), port); |
73 | pr_debug("inserting '%s' == %pI4, port %u\n" , |
74 | buffer, &newaddr.ip, port); |
75 | |
76 | if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, match_offset: matchoff, |
77 | match_len: matchlen, rep_buffer: buffer, strlen(buffer))) { |
78 | nf_ct_helper_log(skb, ct, fmt: "cannot mangle packet" ); |
79 | nf_ct_unexpect_related(exp); |
80 | return NF_DROP; |
81 | } |
82 | |
83 | return NF_ACCEPT; |
84 | } |
85 | |
86 | static void __exit nf_nat_irc_fini(void) |
87 | { |
88 | nf_nat_helper_unregister(nat: &nat_helper_irc); |
89 | RCU_INIT_POINTER(nf_nat_irc_hook, NULL); |
90 | synchronize_rcu(); |
91 | } |
92 | |
93 | static int __init nf_nat_irc_init(void) |
94 | { |
95 | BUG_ON(nf_nat_irc_hook != NULL); |
96 | nf_nat_helper_register(nat: &nat_helper_irc); |
97 | RCU_INIT_POINTER(nf_nat_irc_hook, help); |
98 | return 0; |
99 | } |
100 | |
101 | /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ |
102 | static int warn_set(const char *val, const struct kernel_param *kp) |
103 | { |
104 | pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n" ); |
105 | return 0; |
106 | } |
107 | module_param_call(ports, warn_set, NULL, NULL, 0); |
108 | |
109 | module_init(nf_nat_irc_init); |
110 | module_exit(nf_nat_irc_fini); |
111 | |