1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * ip_vs_ftp.c: IPVS ftp application module
4 *
5 * Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
6 *
7 * Changes:
8 *
9 * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
10 * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
11 *
12 * IP_MASQ_FTP ftp masquerading module
13 *
14 * Version: @(#)ip_masq_ftp.c 0.04 02/05/96
15 *
16 * Author: Wouter Gadeyne
17 */
18
19 #define KMSG_COMPONENT "IPVS"
20 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
21
22 #include <linux/module.h>
23 #include <linux/moduleparam.h>
24 #include <linux/kernel.h>
25 #include <linux/skbuff.h>
26 #include <linux/ctype.h>
27 #include <linux/inet.h>
28 #include <linux/in.h>
29 #include <linux/ip.h>
30 #include <linux/netfilter.h>
31 #include <net/netfilter/nf_conntrack.h>
32 #include <net/netfilter/nf_conntrack_expect.h>
33 #include <net/netfilter/nf_nat.h>
34 #include <net/netfilter/nf_nat_helper.h>
35 #include <linux/gfp.h>
36 #include <net/protocol.h>
37 #include <net/tcp.h>
38 #include <asm/unaligned.h>
39
40 #include <net/ip_vs.h>
41
42
43 #define SERVER_STRING_PASV "227 "
44 #define CLIENT_STRING_PORT "PORT"
45 #define SERVER_STRING_EPSV "229 "
46 #define CLIENT_STRING_EPRT "EPRT"
47
48 enum {
49 IP_VS_FTP_ACTIVE = 0,
50 IP_VS_FTP_PORT = 0,
51 IP_VS_FTP_PASV,
52 IP_VS_FTP_EPRT,
53 IP_VS_FTP_EPSV,
54 };
55
56 /*
57 * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
58 * First port is set to the default port.
59 */
60 static unsigned int ports_count = 1;
61 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
62 module_param_array(ports, ushort, &ports_count, 0444);
63 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
64
65
66 static char *ip_vs_ftp_data_ptr(struct sk_buff *skb, struct ip_vs_iphdr *ipvsh)
67 {
68 struct tcphdr *th = (struct tcphdr *)((char *)skb->data + ipvsh->len);
69
70 if ((th->doff << 2) < sizeof(struct tcphdr))
71 return NULL;
72
73 return (char *)th + (th->doff << 2);
74 }
75
76 static int
77 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
78 {
79 /* We use connection tracking for the command connection */
80 cp->flags |= IP_VS_CONN_F_NFCT;
81 return 0;
82 }
83
84
85 static int
86 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
87 {
88 return 0;
89 }
90
91
92 /* Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
93 * with the "pattern". <addr,port> is in network order.
94 * Parse extended format depending on ext. In this case addr can be pre-set.
95 */
96 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
97 const char *pattern, size_t plen,
98 char skip, bool ext, int mode,
99 union nf_inet_addr *addr, __be16 *port,
100 __u16 af, char **start, char **end)
101 {
102 char *s, c;
103 unsigned char p[6];
104 char edelim;
105 __u16 hport;
106 int i = 0;
107
108 if (data_limit - data < plen) {
109 /* check if there is partial match */
110 if (strncasecmp(data, pattern, data_limit - data) == 0)
111 return -1;
112 else
113 return 0;
114 }
115
116 if (strncasecmp(data, pattern, plen) != 0) {
117 return 0;
118 }
119 s = data + plen;
120 if (skip) {
121 bool found = false;
122
123 for (;; s++) {
124 if (s == data_limit)
125 return -1;
126 if (!found) {
127 /* "(" is optional for non-extended format,
128 * so catch the start of IPv4 address
129 */
130 if (!ext && isdigit(*s))
131 break;
132 if (*s == skip)
133 found = true;
134 } else if (*s != skip) {
135 break;
136 }
137 }
138 }
139 /* Old IPv4-only format? */
140 if (!ext) {
141 p[0] = 0;
142 for (data = s; ; data++) {
143 if (data == data_limit)
144 return -1;
145 c = *data;
146 if (isdigit(c)) {
147 p[i] = p[i]*10 + c - '0';
148 } else if (c == ',' && i < 5) {
149 i++;
150 p[i] = 0;
151 } else {
152 /* unexpected character or terminator */
153 break;
154 }
155 }
156
157 if (i != 5)
158 return -1;
159
160 *start = s;
161 *end = data;
162 addr->ip = get_unaligned((__be32 *) p);
163 *port = get_unaligned((__be16 *) (p + 4));
164 return 1;
165 }
166 if (s == data_limit)
167 return -1;
168 *start = s;
169 edelim = *s++;
170 if (edelim < 33 || edelim > 126)
171 return -1;
172 if (s == data_limit)
173 return -1;
174 if (*s == edelim) {
175 /* Address family is usually missing for EPSV response */
176 if (mode != IP_VS_FTP_EPSV)
177 return -1;
178 s++;
179 if (s == data_limit)
180 return -1;
181 /* Then address should be missing too */
182 if (*s != edelim)
183 return -1;
184 /* Caller can pre-set addr, if needed */
185 s++;
186 } else {
187 const char *ep;
188
189 /* We allow address only from same family */
190 if (af == AF_INET6 && *s != '2')
191 return -1;
192 if (af == AF_INET && *s != '1')
193 return -1;
194 s++;
195 if (s == data_limit)
196 return -1;
197 if (*s != edelim)
198 return -1;
199 s++;
200 if (s == data_limit)
201 return -1;
202 if (af == AF_INET6) {
203 if (in6_pton(s, data_limit - s, (u8 *)addr, edelim,
204 &ep) <= 0)
205 return -1;
206 } else {
207 if (in4_pton(s, data_limit - s, (u8 *)addr, edelim,
208 &ep) <= 0)
209 return -1;
210 }
211 s = (char *) ep;
212 if (s == data_limit)
213 return -1;
214 if (*s != edelim)
215 return -1;
216 s++;
217 }
218 for (hport = 0; ; s++)
219 {
220 if (s == data_limit)
221 return -1;
222 if (!isdigit(*s))
223 break;
224 hport = hport * 10 + *s - '0';
225 }
226 if (s == data_limit || !hport || *s != edelim)
227 return -1;
228 s++;
229 *end = s;
230 *port = htons(hport);
231 return 1;
232 }
233
234 /* Look at outgoing ftp packets to catch the response to a PASV/EPSV command
235 * from the server (inside-to-outside).
236 * When we see one, we build a connection entry with the client address,
237 * client port 0 (unknown at the moment), the server address and the
238 * server port. Mark the current connection entry as a control channel
239 * of the new entry. All this work is just to make the data connection
240 * can be scheduled to the right server later.
241 *
242 * The outgoing packet should be something like
243 * "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
244 * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
245 * The extended format for EPSV response provides usually only port:
246 * "229 Entering Extended Passive Mode (|||ppp|)"
247 */
248 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
249 struct sk_buff *skb, int *diff,
250 struct ip_vs_iphdr *ipvsh)
251 {
252 char *data, *data_limit;
253 char *start, *end;
254 union nf_inet_addr from;
255 __be16 port;
256 struct ip_vs_conn *n_cp;
257 char buf[24]; /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
258 unsigned int buf_len;
259 int ret = 0;
260 enum ip_conntrack_info ctinfo;
261 struct nf_conn *ct;
262
263 *diff = 0;
264
265 /* Only useful for established sessions */
266 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
267 return 1;
268
269 /* Linear packets are much easier to deal with. */
270 if (skb_ensure_writable(skb, skb->len))
271 return 0;
272
273 if (cp->app_data == (void *) IP_VS_FTP_PASV) {
274 data = ip_vs_ftp_data_ptr(skb, ipvsh);
275 data_limit = skb_tail_pointer(skb);
276
277 if (!data || data >= data_limit)
278 return 1;
279
280 if (ip_vs_ftp_get_addrport(data, data_limit,
281 SERVER_STRING_PASV,
282 sizeof(SERVER_STRING_PASV)-1,
283 '(', false, IP_VS_FTP_PASV,
284 &from, &port, cp->af,
285 &start, &end) != 1)
286 return 1;
287
288 IP_VS_DBG(7, "PASV response (%pI4:%u) -> %pI4:%u detected\n",
289 &from.ip, ntohs(port), &cp->caddr.ip, 0);
290 } else if (cp->app_data == (void *) IP_VS_FTP_EPSV) {
291 data = ip_vs_ftp_data_ptr(skb, ipvsh);
292 data_limit = skb_tail_pointer(skb);
293
294 if (!data || data >= data_limit)
295 return 1;
296
297 /* Usually, data address is not specified but
298 * we support different address, so pre-set it.
299 */
300 from = cp->daddr;
301 if (ip_vs_ftp_get_addrport(data, data_limit,
302 SERVER_STRING_EPSV,
303 sizeof(SERVER_STRING_EPSV)-1,
304 '(', true, IP_VS_FTP_EPSV,
305 &from, &port, cp->af,
306 &start, &end) != 1)
307 return 1;
308
309 IP_VS_DBG_BUF(7, "EPSV response (%s:%u) -> %s:%u detected\n",
310 IP_VS_DBG_ADDR(cp->af, &from), ntohs(port),
311 IP_VS_DBG_ADDR(cp->af, &cp->caddr), 0);
312 } else {
313 return 1;
314 }
315
316 /* Now update or create a connection entry for it */
317 {
318 struct ip_vs_conn_param p;
319
320 ip_vs_conn_fill_param(cp->ipvs, cp->af,
321 ipvsh->protocol, &from, port,
322 &cp->caddr, 0, &p);
323 n_cp = ip_vs_conn_out_get(&p);
324 }
325 if (!n_cp) {
326 struct ip_vs_conn_param p;
327
328 ip_vs_conn_fill_param(cp->ipvs,
329 cp->af, ipvsh->protocol, &cp->caddr,
330 0, &cp->vaddr, port, &p);
331 n_cp = ip_vs_conn_new(&p, cp->af, &from, port,
332 IP_VS_CONN_F_NO_CPORT |
333 IP_VS_CONN_F_NFCT,
334 cp->dest, skb->mark);
335 if (!n_cp)
336 return 0;
337
338 /* add its controller */
339 ip_vs_control_add(n_cp, cp);
340 }
341
342 /* Replace the old passive address with the new one */
343 if (cp->app_data == (void *) IP_VS_FTP_PASV) {
344 from.ip = n_cp->vaddr.ip;
345 port = n_cp->vport;
346 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
347 ((unsigned char *)&from.ip)[0],
348 ((unsigned char *)&from.ip)[1],
349 ((unsigned char *)&from.ip)[2],
350 ((unsigned char *)&from.ip)[3],
351 ntohs(port) >> 8,
352 ntohs(port) & 0xFF);
353 } else if (cp->app_data == (void *) IP_VS_FTP_EPSV) {
354 from = n_cp->vaddr;
355 port = n_cp->vport;
356 /* Only port, client will use VIP for the data connection */
357 snprintf(buf, sizeof(buf), "|||%u|",
358 ntohs(port));
359 } else {
360 *buf = 0;
361 }
362 buf_len = strlen(buf);
363
364 ct = nf_ct_get(skb, &ctinfo);
365 if (ct) {
366 bool mangled;
367
368 /* If mangling fails this function will return 0
369 * which will cause the packet to be dropped.
370 * Mangling can only fail under memory pressure,
371 * hopefully it will succeed on the retransmitted
372 * packet.
373 */
374 mangled = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
375 ipvsh->len,
376 start - data,
377 end - start,
378 buf, buf_len);
379 if (mangled) {
380 ip_vs_nfct_expect_related(skb, ct, n_cp,
381 ipvsh->protocol, 0, 0);
382 if (skb->ip_summed == CHECKSUM_COMPLETE)
383 skb->ip_summed = CHECKSUM_UNNECESSARY;
384 /* csum is updated */
385 ret = 1;
386 }
387 }
388
389 /* Not setting 'diff' is intentional, otherwise the sequence
390 * would be adjusted twice.
391 */
392
393 cp->app_data = (void *) IP_VS_FTP_ACTIVE;
394 ip_vs_tcp_conn_listen(n_cp);
395 ip_vs_conn_put(n_cp);
396 return ret;
397 }
398
399
400 /* Look at incoming ftp packets to catch the PASV/PORT/EPRT/EPSV command
401 * (outside-to-inside).
402 *
403 * The incoming packet having the PORT command should be something like
404 * "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
405 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
406 * In this case, we create a connection entry using the client address and
407 * port, so that the active ftp data connection from the server can reach
408 * the client.
409 * Extended format:
410 * "EPSV\r\n" when client requests server address from same family
411 * "EPSV 1\r\n" when client requests IPv4 server address
412 * "EPSV 2\r\n" when client requests IPv6 server address
413 * "EPSV ALL\r\n" - not supported
414 * EPRT with specified delimiter (ASCII 33..126), "|" by default:
415 * "EPRT |1|IPv4ADDR|PORT|\r\n" when client provides IPv4 addrport
416 * "EPRT |2|IPv6ADDR|PORT|\r\n" when client provides IPv6 addrport
417 */
418 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
419 struct sk_buff *skb, int *diff,
420 struct ip_vs_iphdr *ipvsh)
421 {
422 char *data, *data_start, *data_limit;
423 char *start, *end;
424 union nf_inet_addr to;
425 __be16 port;
426 struct ip_vs_conn *n_cp;
427
428 /* no diff required for incoming packets */
429 *diff = 0;
430
431 /* Only useful for established sessions */
432 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
433 return 1;
434
435 /* Linear packets are much easier to deal with. */
436 if (skb_ensure_writable(skb, skb->len))
437 return 0;
438
439 data = data_start = ip_vs_ftp_data_ptr(skb, ipvsh);
440 data_limit = skb_tail_pointer(skb);
441 if (!data || data >= data_limit)
442 return 1;
443
444 while (data <= data_limit - 6) {
445 if (cp->af == AF_INET &&
446 strncasecmp(data, "PASV\r\n", 6) == 0) {
447 /* Passive mode on */
448 IP_VS_DBG(7, "got PASV at %td of %td\n",
449 data - data_start,
450 data_limit - data_start);
451 cp->app_data = (void *) IP_VS_FTP_PASV;
452 return 1;
453 }
454
455 /* EPSV or EPSV<space><net-prt> */
456 if (strncasecmp(data, "EPSV", 4) == 0 &&
457 (data[4] == ' ' || data[4] == '\r')) {
458 if (data[4] == ' ') {
459 char proto = data[5];
460
461 if (data > data_limit - 7 || data[6] != '\r')
462 return 1;
463
464 #ifdef CONFIG_IP_VS_IPV6
465 if (cp->af == AF_INET6 && proto == '2') {
466 } else
467 #endif
468 if (cp->af == AF_INET && proto == '1') {
469 } else {
470 return 1;
471 }
472 }
473 /* Extended Passive mode on */
474 IP_VS_DBG(7, "got EPSV at %td of %td\n",
475 data - data_start,
476 data_limit - data_start);
477 cp->app_data = (void *) IP_VS_FTP_EPSV;
478 return 1;
479 }
480
481 data++;
482 }
483
484 /*
485 * To support virtual FTP server, the scenerio is as follows:
486 * FTP client ----> Load Balancer ----> FTP server
487 * First detect the port number in the application data,
488 * then create a new connection entry for the coming data
489 * connection.
490 */
491 if (cp->af == AF_INET &&
492 ip_vs_ftp_get_addrport(data_start, data_limit,
493 CLIENT_STRING_PORT,
494 sizeof(CLIENT_STRING_PORT)-1,
495 ' ', false, IP_VS_FTP_PORT,
496 &to, &port, cp->af,
497 &start, &end) == 1) {
498
499 IP_VS_DBG(7, "PORT %pI4:%u detected\n", &to.ip, ntohs(port));
500
501 /* Now update or create a connection entry for it */
502 IP_VS_DBG(7, "protocol %s %pI4:%u %pI4:%u\n",
503 ip_vs_proto_name(ipvsh->protocol),
504 &to.ip, ntohs(port), &cp->vaddr.ip,
505 ntohs(cp->vport)-1);
506 } else if (ip_vs_ftp_get_addrport(data_start, data_limit,
507 CLIENT_STRING_EPRT,
508 sizeof(CLIENT_STRING_EPRT)-1,
509 ' ', true, IP_VS_FTP_EPRT,
510 &to, &port, cp->af,
511 &start, &end) == 1) {
512
513 IP_VS_DBG_BUF(7, "EPRT %s:%u detected\n",
514 IP_VS_DBG_ADDR(cp->af, &to), ntohs(port));
515
516 /* Now update or create a connection entry for it */
517 IP_VS_DBG_BUF(7, "protocol %s %s:%u %s:%u\n",
518 ip_vs_proto_name(ipvsh->protocol),
519 IP_VS_DBG_ADDR(cp->af, &to), ntohs(port),
520 IP_VS_DBG_ADDR(cp->af, &cp->vaddr),
521 ntohs(cp->vport)-1);
522 } else {
523 return 1;
524 }
525
526 /* Passive mode off */
527 cp->app_data = (void *) IP_VS_FTP_ACTIVE;
528
529 {
530 struct ip_vs_conn_param p;
531 ip_vs_conn_fill_param(cp->ipvs, cp->af,
532 ipvsh->protocol, &to, port, &cp->vaddr,
533 htons(ntohs(cp->vport)-1), &p);
534 n_cp = ip_vs_conn_in_get(&p);
535 if (!n_cp) {
536 n_cp = ip_vs_conn_new(&p, cp->af, &cp->daddr,
537 htons(ntohs(cp->dport)-1),
538 IP_VS_CONN_F_NFCT, cp->dest,
539 skb->mark);
540 if (!n_cp)
541 return 0;
542
543 /* add its controller */
544 ip_vs_control_add(n_cp, cp);
545 }
546 }
547
548 /*
549 * Move tunnel to listen state
550 */
551 ip_vs_tcp_conn_listen(n_cp);
552 ip_vs_conn_put(n_cp);
553
554 return 1;
555 }
556
557
558 static struct ip_vs_app ip_vs_ftp = {
559 .name = "ftp",
560 .type = IP_VS_APP_TYPE_FTP,
561 .protocol = IPPROTO_TCP,
562 .module = THIS_MODULE,
563 .incs_list = LIST_HEAD_INIT(ip_vs_ftp.incs_list),
564 .init_conn = ip_vs_ftp_init_conn,
565 .done_conn = ip_vs_ftp_done_conn,
566 .bind_conn = NULL,
567 .unbind_conn = NULL,
568 .pkt_out = ip_vs_ftp_out,
569 .pkt_in = ip_vs_ftp_in,
570 };
571
572 /*
573 * per netns ip_vs_ftp initialization
574 */
575 static int __net_init __ip_vs_ftp_init(struct net *net)
576 {
577 int i, ret;
578 struct ip_vs_app *app;
579 struct netns_ipvs *ipvs = net_ipvs(net);
580
581 if (!ipvs)
582 return -ENOENT;
583
584 app = register_ip_vs_app(ipvs, &ip_vs_ftp);
585 if (IS_ERR(app))
586 return PTR_ERR(app);
587
588 for (i = 0; i < ports_count; i++) {
589 if (!ports[i])
590 continue;
591 ret = register_ip_vs_app_inc(ipvs, app, app->protocol, ports[i]);
592 if (ret)
593 goto err_unreg;
594 pr_info("%s: loaded support on port[%d] = %u\n",
595 app->name, i, ports[i]);
596 }
597 return 0;
598
599 err_unreg:
600 unregister_ip_vs_app(ipvs, &ip_vs_ftp);
601 return ret;
602 }
603 /*
604 * netns exit
605 */
606 static void __ip_vs_ftp_exit(struct net *net)
607 {
608 struct netns_ipvs *ipvs = net_ipvs(net);
609
610 if (!ipvs)
611 return;
612
613 unregister_ip_vs_app(ipvs, &ip_vs_ftp);
614 }
615
616 static struct pernet_operations ip_vs_ftp_ops = {
617 .init = __ip_vs_ftp_init,
618 .exit = __ip_vs_ftp_exit,
619 };
620
621 static int __init ip_vs_ftp_init(void)
622 {
623 /* rcu_barrier() is called by netns on error */
624 return register_pernet_subsys(&ip_vs_ftp_ops);
625 }
626
627 /*
628 * ip_vs_ftp finish.
629 */
630 static void __exit ip_vs_ftp_exit(void)
631 {
632 unregister_pernet_subsys(&ip_vs_ftp_ops);
633 /* rcu_barrier() is called by netns */
634 }
635
636
637 module_init(ip_vs_ftp_init);
638 module_exit(ip_vs_ftp_exit);
639 MODULE_LICENSE("GPL");