1 | // SPDX-License-Identifier: GPL-2.0-only |
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> |
6 | */ |
7 | |
8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
9 | |
10 | #include <linux/module.h> |
11 | #include <linux/moduleparam.h> |
12 | #include <linux/inet.h> |
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> |
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 | |
21 | #define NAT_HELPER_NAME "ftp" |
22 | |
23 | MODULE_LICENSE("GPL" ); |
24 | MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>" ); |
25 | MODULE_DESCRIPTION("ftp NAT helper" ); |
26 | MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME); |
27 | |
28 | /* FIXME: Time out? --RR */ |
29 | |
30 | static struct nf_conntrack_nat_helper nat_helper_ftp = |
31 | NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME); |
32 | |
33 | static int nf_nat_ftp_fmt_cmd(struct nf_conn *ct, enum nf_ct_ftp_type type, |
34 | char *buffer, size_t buflen, |
35 | union nf_inet_addr *addr, u16 port) |
36 | { |
37 | switch (type) { |
38 | case NF_CT_FTP_PORT: |
39 | case NF_CT_FTP_PASV: |
40 | return snprintf(buf: buffer, size: buflen, fmt: "%u,%u,%u,%u,%u,%u" , |
41 | ((unsigned char *)&addr->ip)[0], |
42 | ((unsigned char *)&addr->ip)[1], |
43 | ((unsigned char *)&addr->ip)[2], |
44 | ((unsigned char *)&addr->ip)[3], |
45 | port >> 8, |
46 | port & 0xFF); |
47 | case NF_CT_FTP_EPRT: |
48 | if (nf_ct_l3num(ct) == NFPROTO_IPV4) |
49 | return snprintf(buf: buffer, size: buflen, fmt: "|1|%pI4|%u|" , |
50 | &addr->ip, port); |
51 | else |
52 | return snprintf(buf: buffer, size: buflen, fmt: "|2|%pI6|%u|" , |
53 | &addr->ip6, port); |
54 | case NF_CT_FTP_EPSV: |
55 | return snprintf(buf: buffer, size: buflen, fmt: "|||%u|" , port); |
56 | } |
57 | |
58 | return 0; |
59 | } |
60 | |
61 | /* So, this packet has hit the connection tracking matching code. |
62 | Mangle it, and change the expectation to match the new version. */ |
63 | static unsigned int nf_nat_ftp(struct sk_buff *skb, |
64 | enum ip_conntrack_info ctinfo, |
65 | enum nf_ct_ftp_type type, |
66 | unsigned int protoff, |
67 | unsigned int matchoff, |
68 | unsigned int matchlen, |
69 | struct nf_conntrack_expect *exp) |
70 | { |
71 | union nf_inet_addr newaddr; |
72 | u_int16_t port; |
73 | int dir = CTINFO2DIR(ctinfo); |
74 | struct nf_conn *ct = exp->master; |
75 | char buffer[sizeof("|1||65535|" ) + INET6_ADDRSTRLEN]; |
76 | unsigned int buflen; |
77 | |
78 | pr_debug("type %i, off %u len %u\n" , type, matchoff, matchlen); |
79 | |
80 | /* Connection will come from wherever this packet goes, hence !dir */ |
81 | newaddr = ct->tuplehash[!dir].tuple.dst.u3; |
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 | |
89 | port = nf_nat_exp_find_port(exp, ntohs(exp->saved_proto.tcp.port)); |
90 | if (port == 0) { |
91 | nf_ct_helper_log(skb, ct: exp->master, fmt: "all ports in use" ); |
92 | return NF_DROP; |
93 | } |
94 | |
95 | buflen = nf_nat_ftp_fmt_cmd(ct, type, buffer, buflen: sizeof(buffer), |
96 | addr: &newaddr, port); |
97 | if (!buflen) |
98 | goto out; |
99 | |
100 | pr_debug("calling nf_nat_mangle_tcp_packet\n" ); |
101 | |
102 | if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, match_offset: matchoff, |
103 | match_len: matchlen, rep_buffer: buffer, rep_len: buflen)) |
104 | goto out; |
105 | |
106 | return NF_ACCEPT; |
107 | |
108 | out: |
109 | nf_ct_helper_log(skb, ct, fmt: "cannot mangle packet" ); |
110 | nf_ct_unexpect_related(exp); |
111 | return NF_DROP; |
112 | } |
113 | |
114 | static void __exit nf_nat_ftp_fini(void) |
115 | { |
116 | nf_nat_helper_unregister(nat: &nat_helper_ftp); |
117 | RCU_INIT_POINTER(nf_nat_ftp_hook, NULL); |
118 | synchronize_rcu(); |
119 | } |
120 | |
121 | static int __init nf_nat_ftp_init(void) |
122 | { |
123 | BUG_ON(nf_nat_ftp_hook != NULL); |
124 | nf_nat_helper_register(nat: &nat_helper_ftp); |
125 | RCU_INIT_POINTER(nf_nat_ftp_hook, nf_nat_ftp); |
126 | return 0; |
127 | } |
128 | |
129 | /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ |
130 | static int warn_set(const char *val, const struct kernel_param *kp) |
131 | { |
132 | pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n" ); |
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); |
139 | |