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 */
55 static unsigned int ports_count = 1;
56 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
57 module_param_array(ports, ushort, &ports_count, 0444);
58 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
59
60
61 /* Dummy variable */
62 static int ip_vs_ftp_pasv;
63
64
65 static int
ip_vs_ftp_init_conn(struct ip_vs_app * app,struct ip_vs_conn * cp)66 ip_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
74 static int
ip_vs_ftp_done_conn(struct ip_vs_app * app,struct ip_vs_conn * cp)75 ip_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 */
ip_vs_ftp_get_addrport(char * data,char * data_limit,const char * pattern,size_t plen,char skip,char term,__be32 * addr,__be16 * port,char ** start,char ** end)87 static 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 */
ip_vs_ftp_out(struct ip_vs_app * app,struct ip_vs_conn * cp,struct sk_buff * skb,int * diff)169 static 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 *diff = 0;
187
188 #ifdef CONFIG_IP_VS_IPV6
189 /* This application helper doesn't work with IPv6 yet,
190 * so turn this into a no-op for IPv6 packets
191 */
192 if (cp->af == AF_INET6)
193 return 1;
194 #endif
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 */
ip_vs_ftp_in(struct ip_vs_app * app,struct ip_vs_conn * cp,struct sk_buff * skb,int * diff)313 static 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 /* no diff required for incoming packets */
326 *diff = 0;
327
328 #ifdef CONFIG_IP_VS_IPV6
329 /* This application helper doesn't work with IPv6 yet,
330 * so turn this into a no-op for IPv6 packets
331 */
332 if (cp->af == AF_INET6)
333 return 1;
334 #endif
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
424 static 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 */
__ip_vs_ftp_init(struct net * net)441 static 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
465 err_unreg:
466 unregister_ip_vs_app(net, &ip_vs_ftp);
467 return ret;
468 }
469 /*
470 * netns exit
471 */
__ip_vs_ftp_exit(struct net * net)472 static void __ip_vs_ftp_exit(struct net *net)
473 {
474 unregister_ip_vs_app(net, &ip_vs_ftp);
475 }
476
477 static struct pernet_operations ip_vs_ftp_ops = {
478 .init = __ip_vs_ftp_init,
479 .exit = __ip_vs_ftp_exit,
480 };
481
ip_vs_ftp_init(void)482 static 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 */
ip_vs_ftp_exit(void)494 static 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
501 module_init(ip_vs_ftp_init);
502 module_exit(ip_vs_ftp_exit);
503 MODULE_LICENSE("GPL");
504