Commit | Line | Data |
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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> | |
d33cbeeb | 13 | #include <linux/inet.h> |
55a73324 JK |
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> | |
55a73324 JK |
18 | #include <net/netfilter/nf_conntrack_helper.h> |
19 | #include <net/netfilter/nf_conntrack_expect.h> | |
20 | #include <linux/netfilter/nf_conntrack_ftp.h> | |
21 | ||
22 | MODULE_LICENSE("GPL"); | |
23 | MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); | |
24 | MODULE_DESCRIPTION("ftp NAT helper"); | |
25 | MODULE_ALIAS("ip_nat_ftp"); | |
26 | ||
55a73324 JK |
27 | /* FIXME: Time out? --RR */ |
28 | ||
d33cbeeb | 29 | static int nf_nat_ftp_fmt_cmd(struct nf_conn *ct, enum nf_ct_ftp_type type, |
c299bd53 | 30 | char *buffer, size_t buflen, |
d33cbeeb | 31 | union nf_inet_addr *addr, u16 port) |
55a73324 | 32 | { |
c299bd53 JP |
33 | switch (type) { |
34 | case NF_CT_FTP_PORT: | |
35 | case NF_CT_FTP_PASV: | |
36 | return snprintf(buffer, buflen, "%u,%u,%u,%u,%u,%u", | |
d33cbeeb PM |
37 | ((unsigned char *)&addr->ip)[0], |
38 | ((unsigned char *)&addr->ip)[1], | |
39 | ((unsigned char *)&addr->ip)[2], | |
40 | ((unsigned char *)&addr->ip)[3], | |
c299bd53 JP |
41 | port >> 8, |
42 | port & 0xFF); | |
43 | case NF_CT_FTP_EPRT: | |
d33cbeeb PM |
44 | if (nf_ct_l3num(ct) == NFPROTO_IPV4) |
45 | return snprintf(buffer, buflen, "|1|%pI4|%u|", | |
46 | &addr->ip, port); | |
47 | else | |
48 | return snprintf(buffer, buflen, "|2|%pI6|%u|", | |
49 | &addr->ip6, port); | |
c299bd53 JP |
50 | case NF_CT_FTP_EPSV: |
51 | return snprintf(buffer, buflen, "|||%u|", port); | |
52 | } | |
55a73324 | 53 | |
c299bd53 | 54 | return 0; |
55a73324 JK |
55 | } |
56 | ||
55a73324 JK |
57 | /* So, this packet has hit the connection tracking matching code. |
58 | Mangle it, and change the expectation to match the new version. */ | |
3db05fea | 59 | static unsigned int nf_nat_ftp(struct sk_buff *skb, |
55a73324 JK |
60 | enum ip_conntrack_info ctinfo, |
61 | enum nf_ct_ftp_type type, | |
051966c0 | 62 | unsigned int protoff, |
55a73324 JK |
63 | unsigned int matchoff, |
64 | unsigned int matchlen, | |
25b86e05 | 65 | struct nf_conntrack_expect *exp) |
55a73324 | 66 | { |
d33cbeeb | 67 | union nf_inet_addr newaddr; |
55a73324 JK |
68 | u_int16_t port; |
69 | int dir = CTINFO2DIR(ctinfo); | |
70 | struct nf_conn *ct = exp->master; | |
d33cbeeb | 71 | char buffer[sizeof("|1||65535|") + INET6_ADDRSTRLEN]; |
c299bd53 | 72 | unsigned int buflen; |
55a73324 | 73 | |
0d53778e | 74 | pr_debug("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen); |
55a73324 JK |
75 | |
76 | /* Connection will come from wherever this packet goes, hence !dir */ | |
d33cbeeb | 77 | newaddr = ct->tuplehash[!dir].tuple.dst.u3; |
55a73324 JK |
78 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; |
79 | exp->dir = !dir; | |
80 | ||
81 | /* When you see the packet, we need to NAT it the same as the | |
82 | * this one. */ | |
83 | exp->expectfn = nf_nat_follow_master; | |
84 | ||
85 | /* Try to get same port: if not, try to change it. */ | |
86 | for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { | |
5b92b61f PNA |
87 | int ret; |
88 | ||
55a73324 | 89 | exp->tuple.dst.u.tcp.port = htons(port); |
5b92b61f PNA |
90 | ret = nf_ct_expect_related(exp); |
91 | if (ret == 0) | |
92 | break; | |
93 | else if (ret != -EBUSY) { | |
94 | port = 0; | |
55a73324 | 95 | break; |
5b92b61f | 96 | } |
55a73324 JK |
97 | } |
98 | ||
99 | if (port == 0) | |
100 | return NF_DROP; | |
101 | ||
d33cbeeb PM |
102 | buflen = nf_nat_ftp_fmt_cmd(ct, type, buffer, sizeof(buffer), |
103 | &newaddr, port); | |
c299bd53 JP |
104 | if (!buflen) |
105 | goto out; | |
106 | ||
107 | pr_debug("calling nf_nat_mangle_tcp_packet\n"); | |
108 | ||
051966c0 | 109 | if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, |
c299bd53 JP |
110 | matchlen, buffer, buflen)) |
111 | goto out; | |
112 | ||
55a73324 | 113 | return NF_ACCEPT; |
c299bd53 JP |
114 | |
115 | out: | |
116 | nf_ct_unexpect_related(exp); | |
117 | return NF_DROP; | |
55a73324 JK |
118 | } |
119 | ||
120 | static void __exit nf_nat_ftp_fini(void) | |
121 | { | |
a9b3cd7f | 122 | RCU_INIT_POINTER(nf_nat_ftp_hook, NULL); |
55a73324 JK |
123 | synchronize_rcu(); |
124 | } | |
125 | ||
126 | static int __init nf_nat_ftp_init(void) | |
127 | { | |
d1332e0a | 128 | BUG_ON(nf_nat_ftp_hook != NULL); |
a9b3cd7f | 129 | RCU_INIT_POINTER(nf_nat_ftp_hook, nf_nat_ftp); |
55a73324 JK |
130 | return 0; |
131 | } | |
132 | ||
133 | /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ | |
134 | static int warn_set(const char *val, struct kernel_param *kp) | |
135 | { | |
136 | printk(KERN_INFO KBUILD_MODNAME | |
137 | ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); | |
138 | return 0; | |
139 | } | |
140 | module_param_call(ports, warn_set, NULL, NULL, 0); | |
141 | ||
142 | module_init(nf_nat_ftp_init); | |
143 | module_exit(nf_nat_ftp_fini); |