Jozsef Kadlecsik | 55a7332 | 2006-12-02 22:07:44 -0800 | [diff] [blame] | 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 | |
| 28 | #if 0 |
| 29 | #define DEBUGP printk |
| 30 | #else |
| 31 | #define DEBUGP(format, args...) |
| 32 | #endif |
| 33 | |
| 34 | /* FIXME: Time out? --RR */ |
| 35 | |
| 36 | static int |
| 37 | mangle_rfc959_packet(struct sk_buff **pskb, |
| 38 | __be32 newip, |
| 39 | u_int16_t port, |
| 40 | unsigned int matchoff, |
| 41 | unsigned int matchlen, |
| 42 | struct nf_conn *ct, |
| 43 | enum ip_conntrack_info ctinfo, |
| 44 | u32 *seq) |
| 45 | { |
| 46 | char buffer[sizeof("nnn,nnn,nnn,nnn,nnn,nnn")]; |
| 47 | |
| 48 | sprintf(buffer, "%u,%u,%u,%u,%u,%u", |
| 49 | NIPQUAD(newip), port>>8, port&0xFF); |
| 50 | |
| 51 | DEBUGP("calling nf_nat_mangle_tcp_packet\n"); |
| 52 | |
| 53 | *seq += strlen(buffer) - matchlen; |
| 54 | return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff, |
| 55 | matchlen, buffer, strlen(buffer)); |
| 56 | } |
| 57 | |
| 58 | /* |1|132.235.1.2|6275| */ |
| 59 | static int |
| 60 | mangle_eprt_packet(struct sk_buff **pskb, |
| 61 | __be32 newip, |
| 62 | u_int16_t port, |
| 63 | unsigned int matchoff, |
| 64 | unsigned int matchlen, |
| 65 | struct nf_conn *ct, |
| 66 | enum ip_conntrack_info ctinfo, |
| 67 | u32 *seq) |
| 68 | { |
| 69 | char buffer[sizeof("|1|255.255.255.255|65535|")]; |
| 70 | |
| 71 | sprintf(buffer, "|1|%u.%u.%u.%u|%u|", NIPQUAD(newip), port); |
| 72 | |
| 73 | DEBUGP("calling nf_nat_mangle_tcp_packet\n"); |
| 74 | |
| 75 | *seq += strlen(buffer) - matchlen; |
| 76 | return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff, |
| 77 | matchlen, buffer, strlen(buffer)); |
| 78 | } |
| 79 | |
| 80 | /* |1|132.235.1.2|6275| */ |
| 81 | static int |
| 82 | mangle_epsv_packet(struct sk_buff **pskb, |
| 83 | __be32 newip, |
| 84 | u_int16_t port, |
| 85 | unsigned int matchoff, |
| 86 | unsigned int matchlen, |
| 87 | struct nf_conn *ct, |
| 88 | enum ip_conntrack_info ctinfo, |
| 89 | u32 *seq) |
| 90 | { |
| 91 | char buffer[sizeof("|||65535|")]; |
| 92 | |
| 93 | sprintf(buffer, "|||%u|", port); |
| 94 | |
| 95 | DEBUGP("calling nf_nat_mangle_tcp_packet\n"); |
| 96 | |
| 97 | *seq += strlen(buffer) - matchlen; |
| 98 | return nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, matchoff, |
| 99 | matchlen, buffer, strlen(buffer)); |
| 100 | } |
| 101 | |
| 102 | static int (*mangle[])(struct sk_buff **, __be32, u_int16_t, |
| 103 | unsigned int, unsigned int, struct nf_conn *, |
| 104 | enum ip_conntrack_info, u32 *seq) |
| 105 | = { |
| 106 | [NF_CT_FTP_PORT] = mangle_rfc959_packet, |
| 107 | [NF_CT_FTP_PASV] = mangle_rfc959_packet, |
| 108 | [NF_CT_FTP_EPRT] = mangle_eprt_packet, |
| 109 | [NF_CT_FTP_EPSV] = mangle_epsv_packet |
| 110 | }; |
| 111 | |
| 112 | /* So, this packet has hit the connection tracking matching code. |
| 113 | Mangle it, and change the expectation to match the new version. */ |
| 114 | static unsigned int nf_nat_ftp(struct sk_buff **pskb, |
| 115 | enum ip_conntrack_info ctinfo, |
| 116 | enum nf_ct_ftp_type type, |
| 117 | unsigned int matchoff, |
| 118 | unsigned int matchlen, |
| 119 | struct nf_conntrack_expect *exp, |
| 120 | u32 *seq) |
| 121 | { |
| 122 | __be32 newip; |
| 123 | u_int16_t port; |
| 124 | int dir = CTINFO2DIR(ctinfo); |
| 125 | struct nf_conn *ct = exp->master; |
| 126 | |
| 127 | DEBUGP("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen); |
| 128 | |
| 129 | /* Connection will come from wherever this packet goes, hence !dir */ |
| 130 | newip = ct->tuplehash[!dir].tuple.dst.u3.ip; |
| 131 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; |
| 132 | exp->dir = !dir; |
| 133 | |
| 134 | /* When you see the packet, we need to NAT it the same as the |
| 135 | * this one. */ |
| 136 | exp->expectfn = nf_nat_follow_master; |
| 137 | |
| 138 | /* Try to get same port: if not, try to change it. */ |
| 139 | for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { |
| 140 | exp->tuple.dst.u.tcp.port = htons(port); |
| 141 | if (nf_conntrack_expect_related(exp) == 0) |
| 142 | break; |
| 143 | } |
| 144 | |
| 145 | if (port == 0) |
| 146 | return NF_DROP; |
| 147 | |
| 148 | if (!mangle[type](pskb, newip, port, matchoff, matchlen, ct, ctinfo, |
| 149 | seq)) { |
| 150 | nf_conntrack_unexpect_related(exp); |
| 151 | return NF_DROP; |
| 152 | } |
| 153 | return NF_ACCEPT; |
| 154 | } |
| 155 | |
| 156 | static void __exit nf_nat_ftp_fini(void) |
| 157 | { |
| 158 | rcu_assign_pointer(nf_nat_ftp_hook, NULL); |
| 159 | synchronize_rcu(); |
| 160 | } |
| 161 | |
| 162 | static int __init nf_nat_ftp_init(void) |
| 163 | { |
| 164 | BUG_ON(rcu_dereference(nf_nat_ftp_hook)); |
| 165 | rcu_assign_pointer(nf_nat_ftp_hook, nf_nat_ftp); |
| 166 | return 0; |
| 167 | } |
| 168 | |
| 169 | /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ |
| 170 | static int warn_set(const char *val, struct kernel_param *kp) |
| 171 | { |
| 172 | printk(KERN_INFO KBUILD_MODNAME |
| 173 | ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); |
| 174 | return 0; |
| 175 | } |
| 176 | module_param_call(ports, warn_set, NULL, NULL, 0); |
| 177 | |
| 178 | module_init(nf_nat_ftp_init); |
| 179 | module_exit(nf_nat_ftp_fini); |