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
185 *diff = 0;
186
187 #ifdef CONFIG_IP_VS_IPV6
188 /* This application helper doesn't work with IPv6 yet,
189 * so turn this into a no-op for IPv6 packets
190 */
191 if (cp->af == AF_INET6)
192 return 1;
193 #endif
194
195 /* Only useful for established sessions */
196 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
197 return 1;
198
199 /* Linear packets are much easier to deal with. */
200 if (!skb_make_writable(skb, skb->len))
201 return 0;
202
203 if (cp->app_data == &ip_vs_ftp_pasv) {
204 iph = ip_hdr(skb);
205 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
206 data = (char *)th + (th->doff << 2);
207 data_limit = skb_tail_pointer(skb);
208
209 if (ip_vs_ftp_get_addrport(data, data_limit,
210 SERVER_STRING,
211 sizeof(SERVER_STRING)-1,
212 '(', ')',
213 &from.ip, &port,
214 &start, &end) != 1)
215 return 1;
216
217 IP_VS_DBG(7, "PASV response (%pI4:%d) -> %pI4:%d detected\n",
218 &from.ip, ntohs(port), &cp->caddr.ip, 0);
219
220 /*
221 * Now update or create an connection entry for it
222 */
223 {
224 struct ip_vs_conn_param p;
225 ip_vs_conn_fill_param(cp->ipvs, AF_INET,
226 iph->protocol, &from, port,
227 &cp->caddr, 0, &p);
228 n_cp = ip_vs_conn_out_get(&p);
229 }
230 if (!n_cp) {
231 struct ip_vs_conn_param p;
232 ip_vs_conn_fill_param(cp->ipvs,
233 AF_INET, IPPROTO_TCP, &cp->caddr,
234 0, &cp->vaddr, port, &p);
235 /* As above, this is ipv4 only */
236 n_cp = ip_vs_conn_new(&p, AF_INET, &from, port,
237 IP_VS_CONN_F_NO_CPORT |
238 IP_VS_CONN_F_NFCT,
239 cp->dest, skb->mark);
240 if (!n_cp)
241 return 0;
242
243 /* add its controller */
244 ip_vs_control_add(n_cp, cp);
245 }
246
247 /*
248 * Replace the old passive address with the new one
249 */
250 from.ip = n_cp->vaddr.ip;
251 port = n_cp->vport;
252 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
253 ((unsigned char *)&from.ip)[0],
254 ((unsigned char *)&from.ip)[1],
255 ((unsigned char *)&from.ip)[2],
256 ((unsigned char *)&from.ip)[3],
257 ntohs(port) >> 8,
258 ntohs(port) & 0xFF);
259
260 buf_len = strlen(buf);
261
262 ct = nf_ct_get(skb, &ctinfo);
263 if (ct) {
264 bool mangled;
265
266 /* If mangling fails this function will return 0
267 * which will cause the packet to be dropped.
268 * Mangling can only fail under memory pressure,
269 * hopefully it will succeed on the retransmitted
270 * packet.
271 */
272 mangled = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
273 iph->ihl * 4,
274 start - data,
275 end - start,
276 buf, buf_len);
277 if (mangled) {
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 cp->app_data = NULL;
293 ip_vs_tcp_conn_listen(n_cp);
294 ip_vs_conn_put(n_cp);
295 return ret;
296 }
297 return 1;
298 }
299
300
301 /*
302 * Look at incoming ftp packets to catch the PASV/PORT command
303 * (outside-to-inside).
304 *
305 * The incoming packet having the PORT command should be something like
306 * "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
307 * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
308 * In this case, we create a connection entry using the client address and
309 * port, so that the active ftp data connection from the server can reach
310 * the client.
311 */
ip_vs_ftp_in(struct ip_vs_app * app,struct ip_vs_conn * cp,struct sk_buff * skb,int * diff)312 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
313 struct sk_buff *skb, int *diff)
314 {
315 struct iphdr *iph;
316 struct tcphdr *th;
317 char *data, *data_start, *data_limit;
318 char *start, *end;
319 union nf_inet_addr to;
320 __be16 port;
321 struct ip_vs_conn *n_cp;
322
323 /* no diff required for incoming packets */
324 *diff = 0;
325
326 #ifdef CONFIG_IP_VS_IPV6
327 /* This application helper doesn't work with IPv6 yet,
328 * so turn this into a no-op for IPv6 packets
329 */
330 if (cp->af == AF_INET6)
331 return 1;
332 #endif
333
334 /* Only useful for established sessions */
335 if (cp->state != IP_VS_TCP_S_ESTABLISHED)
336 return 1;
337
338 /* Linear packets are much easier to deal with. */
339 if (!skb_make_writable(skb, skb->len))
340 return 0;
341
342 /*
343 * Detecting whether it is passive
344 */
345 iph = ip_hdr(skb);
346 th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
347
348 /* Since there may be OPTIONS in the TCP packet and the HLEN is
349 the length of the header in 32-bit multiples, it is accurate
350 to calculate data address by th+HLEN*4 */
351 data = data_start = (char *)th + (th->doff << 2);
352 data_limit = skb_tail_pointer(skb);
353
354 while (data <= data_limit - 6) {
355 if (strncasecmp(data, "PASV\r\n", 6) == 0) {
356 /* Passive mode on */
357 IP_VS_DBG(7, "got PASV at %td of %td\n",
358 data - data_start,
359 data_limit - data_start);
360 cp->app_data = &ip_vs_ftp_pasv;
361 return 1;
362 }
363 data++;
364 }
365
366 /*
367 * To support virtual FTP server, the scenerio is as follows:
368 * FTP client ----> Load Balancer ----> FTP server
369 * First detect the port number in the application data,
370 * then create a new connection entry for the coming data
371 * connection.
372 */
373 if (ip_vs_ftp_get_addrport(data_start, data_limit,
374 CLIENT_STRING, sizeof(CLIENT_STRING)-1,
375 ' ', '\r', &to.ip, &port,
376 &start, &end) != 1)
377 return 1;
378
379 IP_VS_DBG(7, "PORT %pI4:%d detected\n", &to.ip, ntohs(port));
380
381 /* Passive mode off */
382 cp->app_data = NULL;
383
384 /*
385 * Now update or create a connection entry for it
386 */
387 IP_VS_DBG(7, "protocol %s %pI4:%d %pI4:%d\n",
388 ip_vs_proto_name(iph->protocol),
389 &to.ip, ntohs(port), &cp->vaddr.ip, 0);
390
391 {
392 struct ip_vs_conn_param p;
393 ip_vs_conn_fill_param(cp->ipvs, AF_INET,
394 iph->protocol, &to, port, &cp->vaddr,
395 htons(ntohs(cp->vport)-1), &p);
396 n_cp = ip_vs_conn_in_get(&p);
397 if (!n_cp) {
398 /* This is ipv4 only */
399 n_cp = ip_vs_conn_new(&p, AF_INET, &cp->daddr,
400 htons(ntohs(cp->dport)-1),
401 IP_VS_CONN_F_NFCT, cp->dest,
402 skb->mark);
403 if (!n_cp)
404 return 0;
405
406 /* add its controller */
407 ip_vs_control_add(n_cp, cp);
408 }
409 }
410
411 /*
412 * Move tunnel to listen state
413 */
414 ip_vs_tcp_conn_listen(n_cp);
415 ip_vs_conn_put(n_cp);
416
417 return 1;
418 }
419
420
421 static struct ip_vs_app ip_vs_ftp = {
422 .name = "ftp",
423 .type = IP_VS_APP_TYPE_FTP,
424 .protocol = IPPROTO_TCP,
425 .module = THIS_MODULE,
426 .incs_list = LIST_HEAD_INIT(ip_vs_ftp.incs_list),
427 .init_conn = ip_vs_ftp_init_conn,
428 .done_conn = ip_vs_ftp_done_conn,
429 .bind_conn = NULL,
430 .unbind_conn = NULL,
431 .pkt_out = ip_vs_ftp_out,
432 .pkt_in = ip_vs_ftp_in,
433 };
434
435 /*
436 * per netns ip_vs_ftp initialization
437 */
__ip_vs_ftp_init(struct net * net)438 static int __net_init __ip_vs_ftp_init(struct net *net)
439 {
440 int i, ret;
441 struct ip_vs_app *app;
442 struct netns_ipvs *ipvs = net_ipvs(net);
443
444 if (!ipvs)
445 return -ENOENT;
446
447 app = register_ip_vs_app(ipvs, &ip_vs_ftp);
448 if (IS_ERR(app))
449 return PTR_ERR(app);
450
451 for (i = 0; i < ports_count; i++) {
452 if (!ports[i])
453 continue;
454 ret = register_ip_vs_app_inc(ipvs, app, app->protocol, ports[i]);
455 if (ret)
456 goto err_unreg;
457 pr_info("%s: loaded support on port[%d] = %d\n",
458 app->name, i, ports[i]);
459 }
460 return 0;
461
462 err_unreg:
463 unregister_ip_vs_app(ipvs, &ip_vs_ftp);
464 return ret;
465 }
466 /*
467 * netns exit
468 */
__ip_vs_ftp_exit(struct net * net)469 static void __ip_vs_ftp_exit(struct net *net)
470 {
471 struct netns_ipvs *ipvs = net_ipvs(net);
472
473 if (!ipvs)
474 return;
475
476 unregister_ip_vs_app(ipvs, &ip_vs_ftp);
477 }
478
479 static struct pernet_operations ip_vs_ftp_ops = {
480 .init = __ip_vs_ftp_init,
481 .exit = __ip_vs_ftp_exit,
482 };
483
ip_vs_ftp_init(void)484 static int __init ip_vs_ftp_init(void)
485 {
486 /* rcu_barrier() is called by netns on error */
487 return register_pernet_subsys(&ip_vs_ftp_ops);
488 }
489
490 /*
491 * ip_vs_ftp finish.
492 */
ip_vs_ftp_exit(void)493 static void __exit ip_vs_ftp_exit(void)
494 {
495 unregister_pernet_subsys(&ip_vs_ftp_ops);
496 /* rcu_barrier() is called by netns */
497 }
498
499
500 module_init(ip_vs_ftp_init);
501 module_exit(ip_vs_ftp_exit);
502 MODULE_LICENSE("GPL");
503