Commit | Line | Data |
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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
55a73324 JK |
2 | /* FTP extension for TCP NAT alteration. */ |
3 | ||
4 | /* (C) 1999-2001 Paul `Rusty' Russell | |
5 | * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org> | |
55a73324 JK |
6 | */ |
7 | ||
5191d70f AS |
8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
9 | ||
55a73324 JK |
10 | #include <linux/module.h> |
11 | #include <linux/moduleparam.h> | |
d33cbeeb | 12 | #include <linux/inet.h> |
55a73324 JK |
13 | #include <linux/tcp.h> |
14 | #include <linux/netfilter_ipv4.h> | |
15 | #include <net/netfilter/nf_nat.h> | |
16 | #include <net/netfilter/nf_nat_helper.h> | |
55a73324 JK |
17 | #include <net/netfilter/nf_conntrack_helper.h> |
18 | #include <net/netfilter/nf_conntrack_expect.h> | |
19 | #include <linux/netfilter/nf_conntrack_ftp.h> | |
20 | ||
53b11308 FL |
21 | #define NAT_HELPER_NAME "ftp" |
22 | ||
55a73324 JK |
23 | MODULE_LICENSE("GPL"); |
24 | MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); | |
25 | MODULE_DESCRIPTION("ftp NAT helper"); | |
53b11308 | 26 | MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME); |
55a73324 | 27 | |
55a73324 JK |
28 | /* FIXME: Time out? --RR */ |
29 | ||
53b11308 FL |
30 | static struct nf_conntrack_nat_helper nat_helper_ftp = |
31 | NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME); | |
32 | ||
d33cbeeb | 33 | static int nf_nat_ftp_fmt_cmd(struct nf_conn *ct, enum nf_ct_ftp_type type, |
c299bd53 | 34 | char *buffer, size_t buflen, |
d33cbeeb | 35 | union nf_inet_addr *addr, u16 port) |
55a73324 | 36 | { |
c299bd53 JP |
37 | switch (type) { |
38 | case NF_CT_FTP_PORT: | |
39 | case NF_CT_FTP_PASV: | |
40 | return snprintf(buffer, buflen, "%u,%u,%u,%u,%u,%u", | |
d33cbeeb PM |
41 | ((unsigned char *)&addr->ip)[0], |
42 | ((unsigned char *)&addr->ip)[1], | |
43 | ((unsigned char *)&addr->ip)[2], | |
44 | ((unsigned char *)&addr->ip)[3], | |
c299bd53 JP |
45 | port >> 8, |
46 | port & 0xFF); | |
47 | case NF_CT_FTP_EPRT: | |
d33cbeeb PM |
48 | if (nf_ct_l3num(ct) == NFPROTO_IPV4) |
49 | return snprintf(buffer, buflen, "|1|%pI4|%u|", | |
50 | &addr->ip, port); | |
51 | else | |
52 | return snprintf(buffer, buflen, "|2|%pI6|%u|", | |
53 | &addr->ip6, port); | |
c299bd53 JP |
54 | case NF_CT_FTP_EPSV: |
55 | return snprintf(buffer, buflen, "|||%u|", port); | |
56 | } | |
55a73324 | 57 | |
c299bd53 | 58 | return 0; |
55a73324 JK |
59 | } |
60 | ||
55a73324 JK |
61 | /* So, this packet has hit the connection tracking matching code. |
62 | Mangle it, and change the expectation to match the new version. */ | |
3db05fea | 63 | static unsigned int nf_nat_ftp(struct sk_buff *skb, |
55a73324 JK |
64 | enum ip_conntrack_info ctinfo, |
65 | enum nf_ct_ftp_type type, | |
051966c0 | 66 | unsigned int protoff, |
55a73324 JK |
67 | unsigned int matchoff, |
68 | unsigned int matchlen, | |
25b86e05 | 69 | struct nf_conntrack_expect *exp) |
55a73324 | 70 | { |
d33cbeeb | 71 | union nf_inet_addr newaddr; |
55a73324 JK |
72 | u_int16_t port; |
73 | int dir = CTINFO2DIR(ctinfo); | |
74 | struct nf_conn *ct = exp->master; | |
d33cbeeb | 75 | char buffer[sizeof("|1||65535|") + INET6_ADDRSTRLEN]; |
c299bd53 | 76 | unsigned int buflen; |
55a73324 | 77 | |
5191d70f | 78 | pr_debug("type %i, off %u len %u\n", type, matchoff, matchlen); |
55a73324 JK |
79 | |
80 | /* Connection will come from wherever this packet goes, hence !dir */ | |
d33cbeeb | 81 | newaddr = ct->tuplehash[!dir].tuple.dst.u3; |
55a73324 JK |
82 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; |
83 | exp->dir = !dir; | |
84 | ||
85 | /* When you see the packet, we need to NAT it the same as the | |
86 | * this one. */ | |
87 | exp->expectfn = nf_nat_follow_master; | |
88 | ||
c92c2717 | 89 | port = nf_nat_exp_find_port(exp, ntohs(exp->saved_proto.tcp.port)); |
b20ab9cc | 90 | if (port == 0) { |
c92c2717 | 91 | nf_ct_helper_log(skb, exp->master, "all ports in use"); |
55a73324 | 92 | return NF_DROP; |
b20ab9cc | 93 | } |
55a73324 | 94 | |
d33cbeeb PM |
95 | buflen = nf_nat_ftp_fmt_cmd(ct, type, buffer, sizeof(buffer), |
96 | &newaddr, port); | |
c299bd53 JP |
97 | if (!buflen) |
98 | goto out; | |
99 | ||
100 | pr_debug("calling nf_nat_mangle_tcp_packet\n"); | |
101 | ||
051966c0 | 102 | if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, |
c299bd53 JP |
103 | matchlen, buffer, buflen)) |
104 | goto out; | |
105 | ||
55a73324 | 106 | return NF_ACCEPT; |
c299bd53 JP |
107 | |
108 | out: | |
b20ab9cc | 109 | nf_ct_helper_log(skb, ct, "cannot mangle packet"); |
c299bd53 JP |
110 | nf_ct_unexpect_related(exp); |
111 | return NF_DROP; | |
55a73324 JK |
112 | } |
113 | ||
114 | static void __exit nf_nat_ftp_fini(void) | |
115 | { | |
53b11308 | 116 | nf_nat_helper_unregister(&nat_helper_ftp); |
a9b3cd7f | 117 | RCU_INIT_POINTER(nf_nat_ftp_hook, NULL); |
55a73324 JK |
118 | synchronize_rcu(); |
119 | } | |
120 | ||
121 | static int __init nf_nat_ftp_init(void) | |
122 | { | |
d1332e0a | 123 | BUG_ON(nf_nat_ftp_hook != NULL); |
53b11308 | 124 | nf_nat_helper_register(&nat_helper_ftp); |
a9b3cd7f | 125 | RCU_INIT_POINTER(nf_nat_ftp_hook, nf_nat_ftp); |
55a73324 JK |
126 | return 0; |
127 | } | |
128 | ||
129 | /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ | |
e4dca7b7 | 130 | static int warn_set(const char *val, const struct kernel_param *kp) |
55a73324 | 131 | { |
5191d70f | 132 | pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); |
55a73324 JK |
133 | return 0; |
134 | } | |
135 | module_param_call(ports, warn_set, NULL, NULL, 0); | |
136 | ||
137 | module_init(nf_nat_ftp_init); | |
138 | module_exit(nf_nat_ftp_fini); |