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55a73324 JK |
1 | /* FTP extension for TCP NAT alteration. */ |
2 | ||
3 | /* (C) 1999-2001 Paul `Rusty' Russell | |
4 | * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org> | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 as | |
8 | * published by the Free Software Foundation. | |
9 | */ | |
10 | ||
11 | #include <linux/module.h> | |
12 | #include <linux/moduleparam.h> | |
13 | #include <linux/ip.h> | |
14 | #include <linux/tcp.h> | |
15 | #include <linux/netfilter_ipv4.h> | |
16 | #include <net/netfilter/nf_nat.h> | |
17 | #include <net/netfilter/nf_nat_helper.h> | |
18 | #include <net/netfilter/nf_nat_rule.h> | |
19 | #include <net/netfilter/nf_conntrack_helper.h> | |
20 | #include <net/netfilter/nf_conntrack_expect.h> | |
21 | #include <linux/netfilter/nf_conntrack_ftp.h> | |
22 | ||
23 | MODULE_LICENSE("GPL"); | |
24 | MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); | |
25 | MODULE_DESCRIPTION("ftp NAT helper"); | |
26 | MODULE_ALIAS("ip_nat_ftp"); | |
27 | ||
55a73324 JK |
28 | /* FIXME: Time out? --RR */ |
29 | ||
30 | static int | |
3db05fea | 31 | mangle_rfc959_packet(struct sk_buff *skb, |
55a73324 JK |
32 | __be32 newip, |
33 | u_int16_t port, | |
34 | unsigned int matchoff, | |
35 | unsigned int matchlen, | |
36 | struct nf_conn *ct, | |
25b86e05 | 37 | enum ip_conntrack_info ctinfo) |
55a73324 JK |
38 | { |
39 | char buffer[sizeof("nnn,nnn,nnn,nnn,nnn,nnn")]; | |
40 | ||
41 | sprintf(buffer, "%u,%u,%u,%u,%u,%u", | |
42 | NIPQUAD(newip), port>>8, port&0xFF); | |
43 | ||
0d53778e | 44 | pr_debug("calling nf_nat_mangle_tcp_packet\n"); |
55a73324 | 45 | |
3db05fea | 46 | return nf_nat_mangle_tcp_packet(skb, ct, ctinfo, matchoff, |
55a73324 JK |
47 | matchlen, buffer, strlen(buffer)); |
48 | } | |
49 | ||
50 | /* |1|132.235.1.2|6275| */ | |
51 | static int | |
3db05fea | 52 | mangle_eprt_packet(struct sk_buff *skb, |
55a73324 JK |
53 | __be32 newip, |
54 | u_int16_t port, | |
55 | unsigned int matchoff, | |
56 | unsigned int matchlen, | |
57 | struct nf_conn *ct, | |
25b86e05 | 58 | enum ip_conntrack_info ctinfo) |
55a73324 JK |
59 | { |
60 | char buffer[sizeof("|1|255.255.255.255|65535|")]; | |
61 | ||
62 | sprintf(buffer, "|1|%u.%u.%u.%u|%u|", NIPQUAD(newip), port); | |
63 | ||
0d53778e | 64 | pr_debug("calling nf_nat_mangle_tcp_packet\n"); |
55a73324 | 65 | |
3db05fea | 66 | return nf_nat_mangle_tcp_packet(skb, ct, ctinfo, matchoff, |
55a73324 JK |
67 | matchlen, buffer, strlen(buffer)); |
68 | } | |
69 | ||
70 | /* |1|132.235.1.2|6275| */ | |
71 | static int | |
3db05fea | 72 | mangle_epsv_packet(struct sk_buff *skb, |
55a73324 JK |
73 | __be32 newip, |
74 | u_int16_t port, | |
75 | unsigned int matchoff, | |
76 | unsigned int matchlen, | |
77 | struct nf_conn *ct, | |
25b86e05 | 78 | enum ip_conntrack_info ctinfo) |
55a73324 JK |
79 | { |
80 | char buffer[sizeof("|||65535|")]; | |
81 | ||
82 | sprintf(buffer, "|||%u|", port); | |
83 | ||
0d53778e | 84 | pr_debug("calling nf_nat_mangle_tcp_packet\n"); |
55a73324 | 85 | |
3db05fea | 86 | return nf_nat_mangle_tcp_packet(skb, ct, ctinfo, matchoff, |
55a73324 JK |
87 | matchlen, buffer, strlen(buffer)); |
88 | } | |
89 | ||
3db05fea | 90 | static int (*mangle[])(struct sk_buff *, __be32, u_int16_t, |
55a73324 | 91 | unsigned int, unsigned int, struct nf_conn *, |
25b86e05 | 92 | enum ip_conntrack_info) |
55a73324 JK |
93 | = { |
94 | [NF_CT_FTP_PORT] = mangle_rfc959_packet, | |
95 | [NF_CT_FTP_PASV] = mangle_rfc959_packet, | |
96 | [NF_CT_FTP_EPRT] = mangle_eprt_packet, | |
97 | [NF_CT_FTP_EPSV] = mangle_epsv_packet | |
98 | }; | |
99 | ||
100 | /* So, this packet has hit the connection tracking matching code. | |
101 | Mangle it, and change the expectation to match the new version. */ | |
3db05fea | 102 | static unsigned int nf_nat_ftp(struct sk_buff *skb, |
55a73324 JK |
103 | enum ip_conntrack_info ctinfo, |
104 | enum nf_ct_ftp_type type, | |
105 | unsigned int matchoff, | |
106 | unsigned int matchlen, | |
25b86e05 | 107 | struct nf_conntrack_expect *exp) |
55a73324 JK |
108 | { |
109 | __be32 newip; | |
110 | u_int16_t port; | |
111 | int dir = CTINFO2DIR(ctinfo); | |
112 | struct nf_conn *ct = exp->master; | |
113 | ||
0d53778e | 114 | pr_debug("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen); |
55a73324 JK |
115 | |
116 | /* Connection will come from wherever this packet goes, hence !dir */ | |
117 | newip = ct->tuplehash[!dir].tuple.dst.u3.ip; | |
118 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; | |
119 | exp->dir = !dir; | |
120 | ||
121 | /* When you see the packet, we need to NAT it the same as the | |
122 | * this one. */ | |
123 | exp->expectfn = nf_nat_follow_master; | |
124 | ||
125 | /* Try to get same port: if not, try to change it. */ | |
126 | for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { | |
127 | exp->tuple.dst.u.tcp.port = htons(port); | |
6823645d | 128 | if (nf_ct_expect_related(exp) == 0) |
55a73324 JK |
129 | break; |
130 | } | |
131 | ||
132 | if (port == 0) | |
133 | return NF_DROP; | |
134 | ||
3db05fea | 135 | if (!mangle[type](skb, newip, port, matchoff, matchlen, ct, ctinfo)) { |
6823645d | 136 | nf_ct_unexpect_related(exp); |
55a73324 JK |
137 | return NF_DROP; |
138 | } | |
139 | return NF_ACCEPT; | |
140 | } | |
141 | ||
142 | static void __exit nf_nat_ftp_fini(void) | |
143 | { | |
144 | rcu_assign_pointer(nf_nat_ftp_hook, NULL); | |
145 | synchronize_rcu(); | |
146 | } | |
147 | ||
148 | static int __init nf_nat_ftp_init(void) | |
149 | { | |
150 | BUG_ON(rcu_dereference(nf_nat_ftp_hook)); | |
151 | rcu_assign_pointer(nf_nat_ftp_hook, nf_nat_ftp); | |
152 | return 0; | |
153 | } | |
154 | ||
155 | /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ | |
156 | static int warn_set(const char *val, struct kernel_param *kp) | |
157 | { | |
158 | printk(KERN_INFO KBUILD_MODNAME | |
159 | ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); | |
160 | return 0; | |
161 | } | |
162 | module_param_call(ports, warn_set, NULL, NULL, 0); | |
163 | ||
164 | module_init(nf_nat_ftp_init); | |
165 | module_exit(nf_nat_ftp_fini); |