1/*
2 * ip_vs_ftp.c: IPVS ftp application module
3 *
4 * Authors:	Wensong Zhang <wensong@linuxvirtualserver.org>
5 *
6 * Changes:
7 *
8 *
9 *	This program is free software; you can redistribute it and/or
10 *	modify it under the terms of the GNU General Public License
11 *	as published by the Free Software Foundation; either version
12 *	2 of the License, or (at your option) any later version.
13 *
14 * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
15 * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
16 *
17 *		IP_MASQ_FTP ftp masquerading module
18 *
19 * Version:	@(#)ip_masq_ftp.c 0.04   02/05/96
20 *
21 * Author:	Wouter Gadeyne
22 *
23 */
24
25#define KMSG_COMPONENT "IPVS"
26#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
27
28#include <linux/module.h>
29#include <linux/moduleparam.h>
30#include <linux/kernel.h>
31#include <linux/skbuff.h>
32#include <linux/in.h>
33#include <linux/ip.h>
34#include <linux/netfilter.h>
35#include <net/netfilter/nf_conntrack.h>
36#include <net/netfilter/nf_conntrack_expect.h>
37#include <net/netfilter/nf_nat.h>
38#include <net/netfilter/nf_nat_helper.h>
39#include <linux/gfp.h>
40#include <net/protocol.h>
41#include <net/tcp.h>
42#include <asm/unaligned.h>
43
44#include <net/ip_vs.h>
45
46
47#define SERVER_STRING "227 "
48#define CLIENT_STRING "PORT"
49
50
51/*
52 * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
53 * First port is set to the default port.
54 */
55static unsigned int ports_count = 1;
56static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
57module_param_array(ports, ushort, &ports_count, 0444);
58MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
59
60
61/*	Dummy variable */
62static int ip_vs_ftp_pasv;
63
64
65static int
66ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
67{
68	/* We use connection tracking for the command connection */
69	cp->flags |= IP_VS_CONN_F_NFCT;
70	return 0;
71}
72
73
74static int
75ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
76{
77	return 0;
78}
79
80
81/*
82 * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
83 * with the "pattern", ignoring before "skip" and terminated with
84 * the "term" character.
85 * <addr,port> is in network order.
86 */
87static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
88				  const char *pattern, size_t plen,
89				  char skip, char term,
90				  __be32 *addr, __be16 *port,
91				  char **start, char **end)
92{
93	char *s, c;
94	unsigned char p[6];
95	int i = 0;
96
97	if (data_limit - data < plen) {
98		/* check if there is partial match */
99		if (strncasecmp(data, pattern, data_limit - data) == 0)
100			return -1;
101		else
102			return 0;
103	}
104
105	if (strncasecmp(data, pattern, plen) != 0) {
106		return 0;
107	}
108	s = data + plen;
109	if (skip) {
110		int found = 0;
111
112		for (;; s++) {
113			if (s == data_limit)
114				return -1;
115			if (!found) {
116				if (*s == skip)
117					found = 1;
118			} else if (*s != skip) {
119				break;
120			}
121		}
122	}
123
124	for (data = s; ; data++) {
125		if (data == data_limit)
126			return -1;
127		if (*data == term)
128			break;
129	}
130	*end = data;
131
132	memset(p, 0, sizeof(p));
133	for (data = s; ; data++) {
134		c = *data;
135		if (c == term)
136			break;
137		if (c >= '0' && c <= '9') {
138			p[i] = p[i]*10 + c - '0';
139		} else if (c == ',' && i < 5) {
140			i++;
141		} else {
142			/* unexpected character */
143			return -1;
144		}
145	}
146
147	if (i != 5)
148		return -1;
149
150	*start = s;
151	*addr = get_unaligned((__be32 *) p);
152	*port = get_unaligned((__be16 *) (p + 4));
153	return 1;
154}
155
156/*
157 * Look at outgoing ftp packets to catch the response to a PASV command
158 * from the server (inside-to-outside).
159 * When we see one, we build a connection entry with the client address,
160 * client port 0 (unknown at the moment), the server address and the
161 * server port.  Mark the current connection entry as a control channel
162 * of the new entry. All this work is just to make the data connection
163 * can be scheduled to the right server later.
164 *
165 * The outgoing packet should be something like
166 *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
167 * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
168 */
169static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
170			 struct sk_buff *skb, int *diff)
171{
172	struct iphdr *iph;
173	struct tcphdr *th;
174	char *data, *data_limit;
175	char *start, *end;
176	union nf_inet_addr from;
177	__be16 port;
178	struct ip_vs_conn *n_cp;
179	char buf[24];		/* xxx.xxx.xxx.xxx,ppp,ppp\000 */
180	unsigned int buf_len;
181	int ret = 0;
182	enum ip_conntrack_info ctinfo;
183	struct nf_conn *ct;
184	struct net *net;
185
186#ifdef CONFIG_IP_VS_IPV6
187	/* This application helper doesn't work with IPv6 yet,
188	 * so turn this into a no-op for IPv6 packets
189	 */
190	if (cp->af == AF_INET6)
191		return 1;
192#endif
193
194	*diff = 0;
195
196	/* Only useful for established sessions */
197	if (cp->state != IP_VS_TCP_S_ESTABLISHED)
198		return 1;
199
200	/* Linear packets are much easier to deal with. */
201	if (!skb_make_writable(skb, skb->len))
202		return 0;
203
204	if (cp->app_data == &ip_vs_ftp_pasv) {
205		iph = ip_hdr(skb);
206		th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
207		data = (char *)th + (th->doff << 2);
208		data_limit = skb_tail_pointer(skb);
209
210		if (ip_vs_ftp_get_addrport(data, data_limit,
211					   SERVER_STRING,
212					   sizeof(SERVER_STRING)-1,
213					   '(', ')',
214					   &from.ip, &port,
215					   &start, &end) != 1)
216			return 1;
217
218		IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
219			  &from.ip, ntohs(port), &cp->caddr.ip, 0);
220
221		/*
222		 * Now update or create an connection entry for it
223		 */
224		{
225			struct ip_vs_conn_param p;
226			ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
227					      iph->protocol, &from, port,
228					      &cp->caddr, 0, &p);
229			n_cp = ip_vs_conn_out_get(&p);
230		}
231		if (!n_cp) {
232			struct ip_vs_conn_param p;
233			ip_vs_conn_fill_param(ip_vs_conn_net(cp),
234					      AF_INET, IPPROTO_TCP, &cp->caddr,
235					      0, &cp->vaddr, port, &p);
236			/* As above, this is ipv4 only */
237			n_cp = ip_vs_conn_new(&p, AF_INET, &from, port,
238					      IP_VS_CONN_F_NO_CPORT |
239					      IP_VS_CONN_F_NFCT,
240					      cp->dest, skb->mark);
241			if (!n_cp)
242				return 0;
243
244			/* add its controller */
245			ip_vs_control_add(n_cp, cp);
246		}
247
248		/*
249		 * Replace the old passive address with the new one
250		 */
251		from.ip = n_cp->vaddr.ip;
252		port = n_cp->vport;
253		snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
254			 ((unsigned char *)&from.ip)[0],
255			 ((unsigned char *)&from.ip)[1],
256			 ((unsigned char *)&from.ip)[2],
257			 ((unsigned char *)&from.ip)[3],
258			 ntohs(port) >> 8,
259			 ntohs(port) & 0xFF);
260
261		buf_len = strlen(buf);
262
263		ct = nf_ct_get(skb, &ctinfo);
264		if (ct && !nf_ct_is_untracked(ct) && nfct_nat(ct)) {
265			/* If mangling fails this function will return 0
266			 * which will cause the packet to be dropped.
267			 * Mangling can only fail under memory pressure,
268			 * hopefully it will succeed on the retransmitted
269			 * packet.
270			 */
271			rcu_read_lock();
272			ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
273						       iph->ihl * 4,
274						       start-data, end-start,
275						       buf, buf_len);
276			rcu_read_unlock();
277			if (ret) {
278				ip_vs_nfct_expect_related(skb, ct, n_cp,
279							  IPPROTO_TCP, 0, 0);
280				if (skb->ip_summed == CHECKSUM_COMPLETE)
281					skb->ip_summed = CHECKSUM_UNNECESSARY;
282				/* csum is updated */
283				ret = 1;
284			}
285		}
286
287		/*
288		 * Not setting 'diff' is intentional, otherwise the sequence
289		 * would be adjusted twice.
290		 */
291
292		net = skb_net(skb);
293		cp->app_data = NULL;
294		ip_vs_tcp_conn_listen(net, n_cp);
295		ip_vs_conn_put(n_cp);
296		return ret;
297	}
298	return 1;
299}
300
301
302/*
303 * Look at incoming ftp packets to catch the PASV/PORT command
304 * (outside-to-inside).
305 *
306 * The incoming packet having the PORT command should be something like
307 *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
308 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
309 * In this case, we create a connection entry using the client address and
310 * port, so that the active ftp data connection from the server can reach
311 * the client.
312 */
313static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
314			struct sk_buff *skb, int *diff)
315{
316	struct iphdr *iph;
317	struct tcphdr *th;
318	char *data, *data_start, *data_limit;
319	char *start, *end;
320	union nf_inet_addr to;
321	__be16 port;
322	struct ip_vs_conn *n_cp;
323	struct net *net;
324
325#ifdef CONFIG_IP_VS_IPV6
326	/* This application helper doesn't work with IPv6 yet,
327	 * so turn this into a no-op for IPv6 packets
328	 */
329	if (cp->af == AF_INET6)
330		return 1;
331#endif
332
333	/* no diff required for incoming packets */
334	*diff = 0;
335
336	/* Only useful for established sessions */
337	if (cp->state != IP_VS_TCP_S_ESTABLISHED)
338		return 1;
339
340	/* Linear packets are much easier to deal with. */
341	if (!skb_make_writable(skb, skb->len))
342		return 0;
343
344	/*
345	 * Detecting whether it is passive
346	 */
347	iph = ip_hdr(skb);
348	th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
349
350	/* Since there may be OPTIONS in the TCP packet and the HLEN is
351	   the length of the header in 32-bit multiples, it is accurate
352	   to calculate data address by th+HLEN*4 */
353	data = data_start = (char *)th + (th->doff << 2);
354	data_limit = skb_tail_pointer(skb);
355
356	while (data <= data_limit - 6) {
357		if (strncasecmp(data, "PASV\r\n", 6) == 0) {
358			/* Passive mode on */
359			IP_VS_DBG(7, "got PASV at %td of %td\n",
360				  data - data_start,
361				  data_limit - data_start);
362			cp->app_data = &ip_vs_ftp_pasv;
363			return 1;
364		}
365		data++;
366	}
367
368	/*
369	 * To support virtual FTP server, the scenerio is as follows:
370	 *       FTP client ----> Load Balancer ----> FTP server
371	 * First detect the port number in the application data,
372	 * then create a new connection entry for the coming data
373	 * connection.
374	 */
375	if (ip_vs_ftp_get_addrport(data_start, data_limit,
376				   CLIENT_STRING, sizeof(CLIENT_STRING)-1,
377				   ' ', '\r', &to.ip, &port,
378				   &start, &end) != 1)
379		return 1;
380
381	IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
382
383	/* Passive mode off */
384	cp->app_data = NULL;
385
386	/*
387	 * Now update or create a connection entry for it
388	 */
389	IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
390		  ip_vs_proto_name(iph->protocol),
391		  &to.ip, ntohs(port), &cp->vaddr.ip, 0);
392
393	{
394		struct ip_vs_conn_param p;
395		ip_vs_conn_fill_param(ip_vs_conn_net(cp), AF_INET,
396				      iph->protocol, &to, port, &cp->vaddr,
397				      htons(ntohs(cp->vport)-1), &p);
398		n_cp = ip_vs_conn_in_get(&p);
399		if (!n_cp) {
400			/* This is ipv4 only */
401			n_cp = ip_vs_conn_new(&p, AF_INET, &cp->daddr,
402					      htons(ntohs(cp->dport)-1),
403					      IP_VS_CONN_F_NFCT, cp->dest,
404					      skb->mark);
405			if (!n_cp)
406				return 0;
407
408			/* add its controller */
409			ip_vs_control_add(n_cp, cp);
410		}
411	}
412
413	/*
414	 *	Move tunnel to listen state
415	 */
416	net = skb_net(skb);
417	ip_vs_tcp_conn_listen(net, n_cp);
418	ip_vs_conn_put(n_cp);
419
420	return 1;
421}
422
423
424static struct ip_vs_app ip_vs_ftp = {
425	.name =		"ftp",
426	.type =		IP_VS_APP_TYPE_FTP,
427	.protocol =	IPPROTO_TCP,
428	.module =	THIS_MODULE,
429	.incs_list =	LIST_HEAD_INIT(ip_vs_ftp.incs_list),
430	.init_conn =	ip_vs_ftp_init_conn,
431	.done_conn =	ip_vs_ftp_done_conn,
432	.bind_conn =	NULL,
433	.unbind_conn =	NULL,
434	.pkt_out =	ip_vs_ftp_out,
435	.pkt_in =	ip_vs_ftp_in,
436};
437
438/*
439 *	per netns ip_vs_ftp initialization
440 */
441static int __net_init __ip_vs_ftp_init(struct net *net)
442{
443	int i, ret;
444	struct ip_vs_app *app;
445	struct netns_ipvs *ipvs = net_ipvs(net);
446
447	if (!ipvs)
448		return -ENOENT;
449
450	app = register_ip_vs_app(net, &ip_vs_ftp);
451	if (IS_ERR(app))
452		return PTR_ERR(app);
453
454	for (i = 0; i < ports_count; i++) {
455		if (!ports[i])
456			continue;
457		ret = register_ip_vs_app_inc(net, app, app->protocol, ports[i]);
458		if (ret)
459			goto err_unreg;
460		pr_info("%s: loaded support on port[%d] = %d\n",
461			app->name, i, ports[i]);
462	}
463	return 0;
464
465err_unreg:
466	unregister_ip_vs_app(net, &ip_vs_ftp);
467	return ret;
468}
469/*
470 *	netns exit
471 */
472static void __ip_vs_ftp_exit(struct net *net)
473{
474	unregister_ip_vs_app(net, &ip_vs_ftp);
475}
476
477static struct pernet_operations ip_vs_ftp_ops = {
478	.init = __ip_vs_ftp_init,
479	.exit = __ip_vs_ftp_exit,
480};
481
482static int __init ip_vs_ftp_init(void)
483{
484	int rv;
485
486	rv = register_pernet_subsys(&ip_vs_ftp_ops);
487	/* rcu_barrier() is called by netns on error */
488	return rv;
489}
490
491/*
492 *	ip_vs_ftp finish.
493 */
494static void __exit ip_vs_ftp_exit(void)
495{
496	unregister_pernet_subsys(&ip_vs_ftp_ops);
497	/* rcu_barrier() is called by netns */
498}
499
500
501module_init(ip_vs_ftp_init);
502module_exit(ip_vs_ftp_exit);
503MODULE_LICENSE("GPL");
504