| 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/inet.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_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 | |
| 27 | /* FIXME: Time out? --RR */ |
| 28 | |
| 29 | static int nf_nat_ftp_fmt_cmd(struct nf_conn *ct, enum nf_ct_ftp_type type, |
| 30 | char *buffer, size_t buflen, |
| 31 | union nf_inet_addr *addr, u16 port) |
| 32 | { |
| 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", |
| 37 | ((unsigned char *)&addr->ip)[0], |
| 38 | ((unsigned char *)&addr->ip)[1], |
| 39 | ((unsigned char *)&addr->ip)[2], |
| 40 | ((unsigned char *)&addr->ip)[3], |
| 41 | port >> 8, |
| 42 | port & 0xFF); |
| 43 | case NF_CT_FTP_EPRT: |
| 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); |
| 50 | case NF_CT_FTP_EPSV: |
| 51 | return snprintf(buffer, buflen, "|||%u|", port); |
| 52 | } |
| 53 | |
| 54 | return 0; |
| 55 | } |
| 56 | |
| 57 | /* So, this packet has hit the connection tracking matching code. |
| 58 | Mangle it, and change the expectation to match the new version. */ |
| 59 | static unsigned int nf_nat_ftp(struct sk_buff *skb, |
| 60 | enum ip_conntrack_info ctinfo, |
| 61 | enum nf_ct_ftp_type type, |
| 62 | unsigned int protoff, |
| 63 | unsigned int matchoff, |
| 64 | unsigned int matchlen, |
| 65 | struct nf_conntrack_expect *exp) |
| 66 | { |
| 67 | union nf_inet_addr newaddr; |
| 68 | u_int16_t port; |
| 69 | int dir = CTINFO2DIR(ctinfo); |
| 70 | struct nf_conn *ct = exp->master; |
| 71 | char buffer[sizeof("|1||65535|") + INET6_ADDRSTRLEN]; |
| 72 | unsigned int buflen; |
| 73 | |
| 74 | pr_debug("FTP_NAT: type %i, off %u len %u\n", type, matchoff, matchlen); |
| 75 | |
| 76 | /* Connection will come from wherever this packet goes, hence !dir */ |
| 77 | newaddr = ct->tuplehash[!dir].tuple.dst.u3; |
| 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++) { |
| 87 | int ret; |
| 88 | |
| 89 | exp->tuple.dst.u.tcp.port = htons(port); |
| 90 | ret = nf_ct_expect_related(exp); |
| 91 | if (ret == 0) |
| 92 | break; |
| 93 | else if (ret != -EBUSY) { |
| 94 | port = 0; |
| 95 | break; |
| 96 | } |
| 97 | } |
| 98 | |
| 99 | if (port == 0) { |
| 100 | nf_ct_helper_log(skb, ct, "all ports in use"); |
| 101 | return NF_DROP; |
| 102 | } |
| 103 | |
| 104 | buflen = nf_nat_ftp_fmt_cmd(ct, type, buffer, sizeof(buffer), |
| 105 | &newaddr, port); |
| 106 | if (!buflen) |
| 107 | goto out; |
| 108 | |
| 109 | pr_debug("calling nf_nat_mangle_tcp_packet\n"); |
| 110 | |
| 111 | if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, |
| 112 | matchlen, buffer, buflen)) |
| 113 | goto out; |
| 114 | |
| 115 | return NF_ACCEPT; |
| 116 | |
| 117 | out: |
| 118 | nf_ct_helper_log(skb, ct, "cannot mangle packet"); |
| 119 | nf_ct_unexpect_related(exp); |
| 120 | return NF_DROP; |
| 121 | } |
| 122 | |
| 123 | static void __exit nf_nat_ftp_fini(void) |
| 124 | { |
| 125 | RCU_INIT_POINTER(nf_nat_ftp_hook, NULL); |
| 126 | synchronize_rcu(); |
| 127 | } |
| 128 | |
| 129 | static int __init nf_nat_ftp_init(void) |
| 130 | { |
| 131 | BUG_ON(nf_nat_ftp_hook != NULL); |
| 132 | RCU_INIT_POINTER(nf_nat_ftp_hook, nf_nat_ftp); |
| 133 | return 0; |
| 134 | } |
| 135 | |
| 136 | /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ |
| 137 | static int warn_set(const char *val, struct kernel_param *kp) |
| 138 | { |
| 139 | printk(KERN_INFO KBUILD_MODNAME |
| 140 | ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); |
| 141 | return 0; |
| 142 | } |
| 143 | module_param_call(ports, warn_set, NULL, NULL, 0); |
| 144 | |
| 145 | module_init(nf_nat_ftp_init); |
| 146 | module_exit(nf_nat_ftp_fini); |