[linux-2.6-block.git] / net / netfilter / nf_nat_ftp.c

/* FTP extension for TCP NAT alteration. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/inet.h>
#include <linux/tcp.h>
#include <linux/netfilter_ipv4.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <linux/netfilter/nf_conntrack_ftp.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
MODULE_DESCRIPTION("ftp NAT helper");
MODULE_ALIAS("ip_nat_ftp");

/* FIXME: Time out? --RR */

static int nf_nat_ftp_fmt_cmd(struct nf_conn *ct, enum nf_ct_ftp_type type,
			      char *buffer, size_t buflen,
			      union nf_inet_addr *addr, u16 port)
{
	switch (type) {
	case NF_CT_FTP_PORT:
	case NF_CT_FTP_PASV:
		return snprintf(buffer, buflen, "%u,%u,%u,%u,%u,%u",
				((unsigned char *)&addr->ip)[0],
				((unsigned char *)&addr->ip)[1],
				((unsigned char *)&addr->ip)[2],
				((unsigned char *)&addr->ip)[3],
				port >> 8,
				port & 0xFF);
	case NF_CT_FTP_EPRT:
		if (nf_ct_l3num(ct) == NFPROTO_IPV4)
			return snprintf(buffer, buflen, "|1|%pI4|%u|",
					&addr->ip, port);
		else
			return snprintf(buffer, buflen, "|2|%pI6|%u|",
					&addr->ip6, port);
	case NF_CT_FTP_EPSV:
		return snprintf(buffer, buflen, "|||%u|", port);
	}

	return 0;
}

/* So, this packet has hit the connection tracking matching code.
   Mangle it, and change the expectation to match the new version. */
static unsigned int nf_nat_ftp(struct sk_buff *skb,
			       enum ip_conntrack_info ctinfo,
			       enum nf_ct_ftp_type type,
			       unsigned int protoff,
			       unsigned int matchoff,
			       unsigned int matchlen,
			       struct nf_conntrack_expect *exp)
{
	union nf_inet_addr newaddr;
	u_int16_t port;
	int dir = CTINFO2DIR(ctinfo);
	struct nf_conn *ct = exp->master;
	char buffer[sizeof("|1||65535|") + INET6_ADDRSTRLEN];
	unsigned int buflen;

	pr_debug("type %i, off %u len %u\n", type, matchoff, matchlen);

	/* Connection will come from wherever this packet goes, hence !dir */
	newaddr = ct->tuplehash[!dir].tuple.dst.u3;
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->dir = !dir;

	/* When you see the packet, we need to NAT it the same as the
	 * this one. */
	exp->expectfn = nf_nat_follow_master;

	/* Try to get same port: if not, try to change it. */
	for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
		int ret;

		exp->tuple.dst.u.tcp.port = htons(port);
		ret = nf_ct_expect_related(exp);
		if (ret == 0)
			break;
		else if (ret != -EBUSY) {
			port = 0;
			break;
		}
	}

	if (port == 0) {
		nf_ct_helper_log(skb, ct, "all ports in use");
		return NF_DROP;
	}

	buflen = nf_nat_ftp_fmt_cmd(ct, type, buffer, sizeof(buffer),
				    &newaddr, port);
	if (!buflen)
		goto out;

	pr_debug("calling nf_nat_mangle_tcp_packet\n");

	if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
				      matchlen, buffer, buflen))
		goto out;

	return NF_ACCEPT;

out:
	nf_ct_helper_log(skb, ct, "cannot mangle packet");
	nf_ct_unexpect_related(exp);
	return NF_DROP;
}

static void __exit nf_nat_ftp_fini(void)
{
	RCU_INIT_POINTER(nf_nat_ftp_hook, NULL);
	synchronize_rcu();
}

static int __init nf_nat_ftp_init(void)
{
	BUG_ON(nf_nat_ftp_hook != NULL);
	RCU_INIT_POINTER(nf_nat_ftp_hook, nf_nat_ftp);
	return 0;
}

/* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
static int warn_set(const char *val, const struct kernel_param *kp)
{
	pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
	return 0;
}
module_param_call(ports, warn_set, NULL, NULL, 0);

module_init(nf_nat_ftp_init);
module_exit(nf_nat_ftp_fini);
Commit	Line	Data
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
5191d70f AS	11	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
5191d70f AS	12
55a73324 JK	13	#include <linux/module.h>
55a73324 JK	14	#include <linux/moduleparam.h>
d33cbeeb	15	#include <linux/inet.h>
55a73324 JK	16	#include <linux/tcp.h>
	17	#include <linux/netfilter_ipv4.h>
	18	#include <net/netfilter/nf_nat.h>
	19	#include <net/netfilter/nf_nat_helper.h>
55a73324 JK	20	#include <net/netfilter/nf_conntrack_helper.h>
	21	#include <net/netfilter/nf_conntrack_expect.h>
	22	#include <linux/netfilter/nf_conntrack_ftp.h>
	23
	24	MODULE_LICENSE("GPL");
	25	MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
	26	MODULE_DESCRIPTION("ftp NAT helper");
	27	MODULE_ALIAS("ip_nat_ftp");
	28
55a73324 JK	29	/* FIXME: Time out? --RR */
55a73324 JK	30
d33cbeeb	31	static int nf_nat_ftp_fmt_cmd(struct nf_conn *ct, enum nf_ct_ftp_type type,
c299bd53	32	char *buffer, size_t buflen,
d33cbeeb	33	union nf_inet_addr *addr, u16 port)
55a73324	34	{
c299bd53 JP	35	switch (type) {
	36	case NF_CT_FTP_PORT:
	37	case NF_CT_FTP_PASV:
	38	return snprintf(buffer, buflen, "%u,%u,%u,%u,%u,%u",
d33cbeeb PM	39	((unsigned char *)&addr->ip)[0],
	40	((unsigned char *)&addr->ip)[1],
	41	((unsigned char *)&addr->ip)[2],
	42	((unsigned char *)&addr->ip)[3],
c299bd53 JP	43	port >> 8,
	44	port & 0xFF);
	45	case NF_CT_FTP_EPRT:
d33cbeeb PM	46	if (nf_ct_l3num(ct) == NFPROTO_IPV4)
	47	return snprintf(buffer, buflen, "\|1\|%pI4\|%u\|",
	48	&addr->ip, port);
	49	else
	50	return snprintf(buffer, buflen, "\|2\|%pI6\|%u\|",
	51	&addr->ip6, port);
c299bd53 JP	52	case NF_CT_FTP_EPSV:
	53	return snprintf(buffer, buflen, "\|\|\|%u\|", port);
	54	}
55a73324	55
c299bd53	56	return 0;
55a73324 JK	57	}
55a73324 JK	58
55a73324 JK	59	/* So, this packet has hit the connection tracking matching code.
55a73324 JK	60	Mangle it, and change the expectation to match the new version. */
3db05fea	61	static unsigned int nf_nat_ftp(struct sk_buff *skb,
55a73324 JK	62	enum ip_conntrack_info ctinfo,
55a73324 JK	63	enum nf_ct_ftp_type type,
051966c0	64	unsigned int protoff,
55a73324 JK	65	unsigned int matchoff,
55a73324 JK	66	unsigned int matchlen,
25b86e05	67	struct nf_conntrack_expect *exp)
55a73324	68	{
d33cbeeb	69	union nf_inet_addr newaddr;
55a73324 JK	70	u_int16_t port;
	71	int dir = CTINFO2DIR(ctinfo);
	72	struct nf_conn *ct = exp->master;
d33cbeeb	73	char buffer[sizeof("\|1\|\|65535\|") + INET6_ADDRSTRLEN];
c299bd53	74	unsigned int buflen;
55a73324	75
5191d70f	76	pr_debug("type %i, off %u len %u\n", type, matchoff, matchlen);
55a73324 JK	77
55a73324 JK	78	/* Connection will come from wherever this packet goes, hence !dir */
d33cbeeb	79	newaddr = ct->tuplehash[!dir].tuple.dst.u3;
55a73324 JK	80	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	81	exp->dir = !dir;
	82
	83	/* When you see the packet, we need to NAT it the same as the
	84	* this one. */
	85	exp->expectfn = nf_nat_follow_master;
	86
	87	/* Try to get same port: if not, try to change it. */
	88	for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
5b92b61f PNA	89	int ret;
5b92b61f PNA	90
55a73324	91	exp->tuple.dst.u.tcp.port = htons(port);
5b92b61f PNA	92	ret = nf_ct_expect_related(exp);
	93	if (ret == 0)
	94	break;
	95	else if (ret != -EBUSY) {
	96	port = 0;
55a73324	97	break;
5b92b61f	98	}
55a73324 JK	99	}
55a73324 JK	100
b20ab9cc PNA	101	if (port == 0) {
b20ab9cc PNA	102	nf_ct_helper_log(skb, ct, "all ports in use");
55a73324	103	return NF_DROP;
b20ab9cc	104	}
55a73324	105
d33cbeeb PM	106	buflen = nf_nat_ftp_fmt_cmd(ct, type, buffer, sizeof(buffer),
d33cbeeb PM	107	&newaddr, port);
c299bd53 JP	108	if (!buflen)
	109	goto out;
	110
	111	pr_debug("calling nf_nat_mangle_tcp_packet\n");
	112
051966c0	113	if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
c299bd53 JP	114	matchlen, buffer, buflen))
	115	goto out;
	116
55a73324	117	return NF_ACCEPT;
c299bd53 JP	118
c299bd53 JP	119	out:
b20ab9cc	120	nf_ct_helper_log(skb, ct, "cannot mangle packet");
c299bd53 JP	121	nf_ct_unexpect_related(exp);
c299bd53 JP	122	return NF_DROP;
55a73324 JK	123	}
	124
	125	static void __exit nf_nat_ftp_fini(void)
	126	{
a9b3cd7f	127	RCU_INIT_POINTER(nf_nat_ftp_hook, NULL);
55a73324 JK	128	synchronize_rcu();
	129	}
	130
	131	static int __init nf_nat_ftp_init(void)
	132	{
d1332e0a	133	BUG_ON(nf_nat_ftp_hook != NULL);
a9b3cd7f	134	RCU_INIT_POINTER(nf_nat_ftp_hook, nf_nat_ftp);
55a73324 JK	135	return 0;
	136	}
	137
	138	/* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
e4dca7b7	139	static int warn_set(const char val, const struct kernel_param kp)
55a73324	140	{
5191d70f	141	pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
55a73324 JK	142	return 0;
	143	}
	144	module_param_call(ports, warn_set, NULL, NULL, 0);
	145
	146	module_init(nf_nat_ftp_init);
	147	module_exit(nf_nat_ftp_fini);