alias_ftp.c@ 68421

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1	/*-
2	* Copyright (c) 2001 Charles Mott <[email protected]>
3	* All rights reserved.
4	*
5	* Redistribution and use in source and binary forms, with or without
6	* modification, are permitted provided that the following conditions
7	* are met:
8	* 1. Redistributions of source code must retain the above copyright
9	* notice, this list of conditions and the following disclaimer.
10	* 2. Redistributions in binary form must reproduce the above copyright
11	* notice, this list of conditions and the following disclaimer in the
12	* documentation and/or other materials provided with the distribution.
13	*
14	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17	* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24	* SUCH DAMAGE.
25	*/
26
27	#ifndef VBOX
28	#include <sys/cdefs.h>
29	__FBSDID("$FreeBSD: src/sys/netinet/libalias/alias_ftp.c,v 1.29.2.1.4.1 2009/04/15 03:14:26 kensmith Exp $");
30
31	/*
32	Alias_ftp.c performs special processing for FTP sessions under
33	TCP. Specifically, when a PORT/EPRT command from the client
34	side or 227/229 reply from the server is sent, it is intercepted
35	and modified. The address is changed to the gateway machine
36	and an aliasing port is used.
37
38	For this routine to work, the message must fit entirely into a
39	single TCP packet. This is typically the case, but exceptions
40	can easily be envisioned under the actual specifications.
41
42	Probably the most troubling aspect of the approach taken here is
43	that the new message will typically be a different length, and
44	this causes a certain amount of bookkeeping to keep track of the
45	changes of sequence and acknowledgment numbers, since the client
46	machine is totally unaware of the modification to the TCP stream.
47
48
49	References: RFC 959, RFC 2428.
50
51	Initial version: August, 1996 (cjm)
52
53	Version 1.6
54	Brian Somers and Martin Renters identified an IP checksum
55	error for modified IP packets.
56
57	Version 1.7: January 9, 1996 (cjm)
58	Differential checksum computation for change
59	in IP packet length.
60
61	Version 2.1: May, 1997 (cjm)
62	Very minor changes to conform with
63	local/global/function naming conventions
64	within the packet aliasing module.
65
66	Version 3.1: May, 2000 (eds)
67	Add support for passive mode, alias the 227 replies.
68
69	See HISTORY file for record of revisions.
70	*/
71
72	/* Includes */
73	#ifdef _KERNEL
74	#include <sys/param.h>
75	#include <sys/ctype.h>
76	#include <sys/systm.h>
77	#include <sys/kernel.h>
78	#include <sys/module.h>
79	#else
80	#include <errno.h>
81	#include <sys/types.h>
82	#include <stdio.h>
83	#include <string.h>
84	#endif
85
86	#include <netinet/in_systm.h>
87	#include <netinet/in.h>
88	#include <netinet/ip.h>
89	#include <netinet/tcp.h>
90
91	#ifdef _KERNEL
92	#include <netinet/libalias/alias.h>
93	#include <netinet/libalias/alias_local.h>
94	#include <netinet/libalias/alias_mod.h>
95	#else
96	#include "alias_local.h"
97	#include "alias_mod.h"
98	#endif
99	#else /* VBOX */
100	# include <iprt/ctype.h>
101	# include <slirp.h>
102	# include "alias_local.h"
103	# include "alias_mod.h"
104	# define isspace(ch) RT_C_IS_SPACE(ch)
105	# define isdigit(ch) RT_C_IS_DIGIT(ch)
106	#endif /* VBOX */
107
108	#define FTP_CONTROL_PORT_NUMBER 21
109
110	static void
111	AliasHandleFtpOut(struct libalias , struct ip , struct alias_link *,
112	int maxpacketsize);
113
114	static int
115	fingerprint(struct libalias la, struct ip pip, struct alias_data *ah)
116	{
117
118	#ifdef VBOX
119	NOREF(la);
120	NOREF(pip);
121	#endif
122	if (ah->dport == NULL \|\| ah->sport == NULL \|\| ah->lnk == NULL \|\|
123	ah->maxpktsize == 0)
124	return (-1);
125	if (ntohs(*ah->dport) == FTP_CONTROL_PORT_NUMBER
126	\|\| ntohs(*ah->sport) == FTP_CONTROL_PORT_NUMBER)
127	return (0);
128	return (-1);
129	}
130
131	static int
132	protohandler(struct libalias la, struct ip pip, struct alias_data *ah)
133	{
134
135	AliasHandleFtpOut(la, pip, ah->lnk, ah->maxpktsize);
136	return (0);
137	}
138
139	#ifndef VBOX
140	struct proto_handler handlers[] = {
141	{
142	.pri = 80,
143	.dir = OUT,
144	.proto = TCP,
145	.fingerprint = &fingerprint,
146	.protohandler = &protohandler
147	},
148	{ EOH }
149	};
150	#else /* VBOX */
151	#define handlers pData->ftp_module
152	#endif /* VBOX */
153
154	#ifndef VBOX
155	static int
156	mod_handler(module_t mod, int type, void *data)
157	#else
158	static int ftp_alias_handler(PNATState pData, int type);
159
160	int
161	ftp_alias_load(PNATState pData)
162	{
163	return ftp_alias_handler(pData, MOD_LOAD);
164	}
165
166	int
167	ftp_alias_unload(PNATState pData)
168	{
169	return ftp_alias_handler(pData, MOD_UNLOAD);
170	}
171	static int
172	ftp_alias_handler(PNATState pData, int type)
173	#endif
174	{
175	int error;
176	#ifdef VBOX
177	if (handlers == NULL)
178	handlers = RTMemAllocZ(2 * sizeof(struct proto_handler));
179	handlers[0].pri = 80;
180	handlers[0].dir = OUT;
181	handlers[0].proto = TCP;
182	handlers[0].fingerprint = &fingerprint;
183	handlers[0].protohandler = &protohandler;
184	handlers[1].pri = (u_int)EOH;
185	#endif /* VBOX */
186
187	switch (type) {
188	case MOD_LOAD:
189	error = 0;
190	#ifdef VBOX
191	LibAliasAttachHandlers(pData, handlers);
192	#else
193	LibAliasAttachHandlers(handlers);
194	#endif
195	break;
196	case MOD_UNLOAD:
197	error = 0;
198	#ifdef VBOX
199	LibAliasDetachHandlers(pData, handlers);
200	RTMemFree(handlers);
201	handlers = NULL;
202	#else
203	LibAliasDetachHandlers(handlers);
204	#endif
205	break;
206	default:
207	error = EINVAL;
208	}
209	return (error);
210	}
211
212	#ifndef VBOX
213	#ifdef _KERNEL
214	static
215	#endif
216	moduledata_t alias_mod = {
217	"alias_ftp", mod_handler, NULL
218	};
219	#endif /* !VBOX */
220
221	#ifdef _KERNEL
222	DECLARE_MODULE(alias_ftp, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
223	MODULE_VERSION(alias_ftp, 1);
224	MODULE_DEPEND(alias_ftp, libalias, 1, 1, 1);
225	#endif
226
227	#define FTP_CONTROL_PORT_NUMBER 21
228	#define MAX_MESSAGE_SIZE 128
229
230	/* FTP protocol flags. */
231	#define WAIT_CRLF 0x01
232
233	enum ftp_message_type {
234	FTP_PORT_COMMAND,
235	FTP_EPRT_COMMAND,
236	FTP_227_REPLY,
237	FTP_229_REPLY,
238	FTP_UNKNOWN_MESSAGE
239	};
240
241	static int ParseFtpPortCommand(struct libalias la, char , int);
242	static int ParseFtpEprtCommand(struct libalias la, char , int);
243	static int ParseFtp227Reply(struct libalias la, char , int);
244	static int ParseFtp229Reply(struct libalias la, char , int);
245	static void NewFtpMessage(struct libalias la, struct ip , struct alias_link *, int, int);
246
247	static void
248	AliasHandleFtpOut(
249	struct libalias *la,
250	struct ip pip, / IP packet to examine/patch */
251	struct alias_link lnk, / The link to go through (aliased port) */
252	int maxpacketsize /* The maximum size this packet can grow to
253	(including headers) */ )
254	{
255	int hlen, tlen, dlen, pflags;
256	char *sptr;
257	struct tcphdr *tc;
258	int ftp_message_type;
259
260	/* Calculate data length of TCP packet */
261	tc = (struct tcphdr *)ip_next(pip);
262	hlen = (pip->ip_hl + tc->th_off) << 2;
263	tlen = ntohs(pip->ip_len);
264	dlen = tlen - hlen;
265
266	/* Place string pointer and beginning of data */
267	sptr = (char *)pip;
268	sptr += hlen;
269
270	/*
271	* Check that data length is not too long and previous message was
272	* properly terminated with CRLF.
273	*/
274	pflags = GetProtocolFlags(lnk);
275	if (dlen <= MAX_MESSAGE_SIZE && !(pflags & WAIT_CRLF)) {
276	ftp_message_type = FTP_UNKNOWN_MESSAGE;
277
278	if (ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER) {
279	/*
280	* When aliasing a client, check for the PORT/EPRT command.
281	*/
282	if (ParseFtpPortCommand(la, sptr, dlen))
283	ftp_message_type = FTP_PORT_COMMAND;
284	else if (ParseFtpEprtCommand(la, sptr, dlen))
285	ftp_message_type = FTP_EPRT_COMMAND;
286	} else {
287	/*
288	* When aliasing a server, check for the 227/229 reply.
289	*/
290	if (ParseFtp227Reply(la, sptr, dlen))
291	ftp_message_type = FTP_227_REPLY;
292	else if (ParseFtp229Reply(la, sptr, dlen)) {
293	ftp_message_type = FTP_229_REPLY;
294	la->true_addr.s_addr = pip->ip_src.s_addr;
295	}
296	}
297
298	if (ftp_message_type != FTP_UNKNOWN_MESSAGE)
299	NewFtpMessage(la, pip, lnk, maxpacketsize, ftp_message_type);
300	}
301	/* Track the msgs which are CRLF term'd for PORT/PASV FW breach */
302
303	if (dlen) { /* only if there's data */
304	sptr = (char )pip; / start over at beginning */
305	tlen = ntohs(pip->ip_len); /* recalc tlen, pkt may
306	* have grown */
307	if (sptr[tlen - 2] == '\r' && sptr[tlen - 1] == '\n')
308	pflags &= ~WAIT_CRLF;
309	else
310	pflags \|= WAIT_CRLF;
311	SetProtocolFlags(lnk, pflags);
312	}
313	}
314
315	static int
316	ParseFtpPortCommand(struct libalias la, char sptr, int dlen)
317	{
318	char ch;
319	int i, state;
320	u_int32_t addr;
321	u_short port;
322	u_int8_t octet;
323
324	/* Format: "PORT A,D,D,R,PO,RT". */
325
326	/* Return if data length is too short. */
327	if (dlen < 18)
328	return (0);
329
330	if (strncasecmp("PORT ", sptr, 5))
331	return (0);
332
333	addr = port = octet = 0;
334	state = 0;
335	for (i = 5; i < dlen; i++) {
336	ch = sptr[i];
337	switch (state) {
338	case 0:
339	if (isspace(ch))
340	break;
341	else
342	state++;
343	/* FALLTHRU */
344	case 1:
345	case 3:
346	case 5:
347	case 7:
348	case 9:
349	case 11:
350	if (isdigit(ch)) {
351	octet = ch - '0';
352	state++;
353	} else
354	return (0);
355	break;
356	case 2:
357	case 4:
358	case 6:
359	case 8:
360	if (isdigit(ch))
361	octet = 10 * octet + ch - '0';
362	else if (ch == ',') {
363	addr = (addr << 8) + octet;
364	state++;
365	} else
366	return (0);
367	break;
368	case 10:
369	case 12:
370	if (isdigit(ch))
371	octet = 10 * octet + ch - '0';
372	else if (ch == ',' \|\| state == 12) {
373	port = (port << 8) + octet;
374	state++;
375	} else
376	return (0);
377	break;
378	}
379	}
380
381	if (state == 13) {
382	la->true_addr.s_addr = htonl(addr);
383	la->true_port = port;
384	return (1);
385	} else
386	return (0);
387	}
388
389	static int
390	ParseFtpEprtCommand(struct libalias la, char sptr, int dlen)
391	{
392	char ch, delim;
393	int i, state;
394	u_int32_t addr;
395	u_short port;
396	u_int8_t octet;
397
398	/* Format: "EPRT \|1\|A.D.D.R\|PORT\|". */
399
400	/* Return if data length is too short. */
401	if (dlen < 18)
402	return (0);
403
404	if (strncasecmp("EPRT ", sptr, 5))
405	return (0);
406
407	addr = port = octet = 0;
408	delim = '\|'; /* XXX gcc -Wuninitialized */
409	state = 0;
410	for (i = 5; i < dlen; i++) {
411	ch = sptr[i];
412	switch (state) {
413	case 0:
414	if (!isspace(ch)) {
415	delim = ch;
416	state++;
417	}
418	break;
419	case 1:
420	if (ch == '1') /* IPv4 address */
421	state++;
422	else
423	return (0);
424	break;
425	case 2:
426	if (ch == delim)
427	state++;
428	else
429	return (0);
430	break;
431	case 3:
432	case 5:
433	case 7:
434	case 9:
435	if (isdigit(ch)) {
436	octet = ch - '0';
437	state++;
438	} else
439	return (0);
440	break;
441	case 4:
442	case 6:
443	case 8:
444	case 10:
445	if (isdigit(ch))
446	octet = 10 * octet + ch - '0';
447	else if (ch == '.' \|\| state == 10) {
448	addr = (addr << 8) + octet;
449	state++;
450	} else
451	return (0);
452	break;
453	case 11:
454	if (isdigit(ch)) {
455	port = ch - '0';
456	state++;
457	} else
458	return (0);
459	break;
460	case 12:
461	if (isdigit(ch))
462	port = 10 * port + ch - '0';
463	else if (ch == delim)
464	state++;
465	else
466	return (0);
467	break;
468	}
469	}
470
471	if (state == 13) {
472	la->true_addr.s_addr = htonl(addr);
473	la->true_port = port;
474	return (1);
475	} else
476	return (0);
477	}
478
479	static int
480	ParseFtp227Reply(struct libalias la, char sptr, int dlen)
481	{
482	char ch;
483	int i, state;
484	u_int32_t addr;
485	u_short port;
486	u_int8_t octet;
487
488	/* Format: "227 Entering Passive Mode (A,D,D,R,PO,RT)" */
489
490	/* Return if data length is too short. */
491	if (dlen < 17)
492	return (0);
493
494	if (strncmp("227 ", sptr, 4))
495	return (0);
496
497	addr = port = octet = 0;
498
499	state = 0;
500	for (i = 4; i < dlen; i++) {
501	ch = sptr[i];
502	switch (state) {
503	case 0:
504	if (ch == '(')
505	state++;
506	break;
507	case 1:
508	case 3:
509	case 5:
510	case 7:
511	case 9:
512	case 11:
513	if (isdigit(ch)) {
514	octet = ch - '0';
515	state++;
516	} else
517	return (0);
518	break;
519	case 2:
520	case 4:
521	case 6:
522	case 8:
523	if (isdigit(ch))
524	octet = 10 * octet + ch - '0';
525	else if (ch == ',') {
526	addr = (addr << 8) + octet;
527	state++;
528	} else
529	return (0);
530	break;
531	case 10:
532	case 12:
533	if (isdigit(ch))
534	octet = 10 * octet + ch - '0';
535	else if (ch == ',' \|\| (state == 12 && ch == ')')) {
536	port = (port << 8) + octet;
537	state++;
538	} else
539	return (0);
540	break;
541	}
542	}
543
544	if (state == 13) {
545	if (addr != INADDR_LOOPBACK)
546	la->true_addr.s_addr = htonl(addr);
547	else
548	la->true_addr.s_addr = la->pData->alias_addr.s_addr;
549	la->true_port = port;
550	return (1);
551	} else
552	return (0);
553	}
554
555	static int
556	ParseFtp229Reply(struct libalias la, char sptr, int dlen)
557	{
558	char ch, delim;
559	int i, state;
560	u_short port;
561
562	/* Format: "229 Entering Extended Passive Mode (\|\|\|PORT\|)" */
563
564	/* Return if data length is too short. */
565	if (dlen < 11)
566	return (0);
567
568	if (strncmp("229 ", sptr, 4))
569	return (0);
570
571	port = 0;
572	delim = '\|'; /* XXX gcc -Wuninitialized */
573
574	state = 0;
575	for (i = 4; i < dlen; i++) {
576	ch = sptr[i];
577	switch (state) {
578	case 0:
579	if (ch == '(')
580	state++;
581	break;
582	case 1:
583	delim = ch;
584	state++;
585	break;
586	case 2:
587	case 3:
588	if (ch == delim)
589	state++;
590	else
591	return (0);
592	break;
593	case 4:
594	if (isdigit(ch)) {
595	port = ch - '0';
596	state++;
597	} else
598	return (0);
599	break;
600	case 5:
601	if (isdigit(ch))
602	port = 10 * port + ch - '0';
603	else if (ch == delim)
604	state++;
605	else
606	return (0);
607	break;
608	case 6:
609	if (ch == ')')
610	state++;
611	else
612	return (0);
613	break;
614	}
615	}
616
617	if (state == 7) {
618	la->true_port = port;
619	return (1);
620	} else
621	return (0);
622	}
623
624	static void
625	NewFtpMessage(struct libalias la, struct ip pip,
626	struct alias_link *lnk,
627	int maxpacketsize,
628	int ftp_message_type)
629	{
630	struct alias_link *ftp_lnk;
631
632	/* Security checks. */
633	if (pip->ip_src.s_addr != la->true_addr.s_addr)
634	return;
635
636	if (la->true_port < IPPORT_RESERVED)
637	return;
638
639	/* Establish link to address and port found in FTP control message. */
640	ftp_lnk = FindUdpTcpOut(la, la->true_addr, GetDestAddress(lnk),
641	htons(la->true_port), 0, IPPROTO_TCP, 1);
642
643	if (ftp_lnk != NULL) {
644	int slen, hlen, tlen, dlen;
645	struct tcphdr *tc;
646
647	#ifndef NO_FW_PUNCH
648	/* Punch hole in firewall */
649	PunchFWHole(ftp_lnk);
650	#endif
651
652	/* Calculate data length of TCP packet */
653	tc = (struct tcphdr *)ip_next(pip);
654	hlen = (pip->ip_hl + tc->th_off) << 2;
655	tlen = ntohs(pip->ip_len);
656	dlen = tlen - hlen;
657
658	/* Create new FTP message. */
659	{
660	char stemp[MAX_MESSAGE_SIZE + 1];
661	char *sptr;
662	u_short alias_port;
663	u_char *ptr;
664	int a1, a2, a3, a4, p1, p2;
665	struct in_addr alias_address;
666
667	/* Decompose alias address into quad format */
668	alias_address = GetAliasAddress(lnk);
669	ptr = (u_char *) & alias_address.s_addr;
670	a1 = *ptr++;
671	a2 = *ptr++;
672	a3 = *ptr++;
673	a4 = *ptr;
674
675	alias_port = GetAliasPort(ftp_lnk);
676
677	/* Prepare new command */
678	switch (ftp_message_type) {
679	case FTP_PORT_COMMAND:
680	case FTP_227_REPLY:
681	/* Decompose alias port into pair format. */
682	ptr = (u_char *)&alias_port;
683	p1 = *ptr++;
684	p2 = *ptr;
685
686	if (ftp_message_type == FTP_PORT_COMMAND) {
687	/* Generate PORT command string. */
688	#ifndef VBOX
689	sprintf(stemp, "PORT %d,%d,%d,%d,%d,%d\r\n",
690	a1, a2, a3, a4, p1, p2);
691	#else
692	RTStrPrintf(stemp, sizeof(stemp), "PORT %d,%d,%d,%d,%d,%d\r\n",
693	a1, a2, a3, a4, p1, p2);
694	#endif
695	} else {
696	/* Generate 227 reply string. */
697	#ifndef VBOX
698	sprintf(stemp,
699	"227 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n",
700	a1, a2, a3, a4, p1, p2);
701	#else
702	RTStrPrintf(stemp, sizeof(stemp),
703	"227 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n",
704	a1, a2, a3, a4, p1, p2);
705	#endif
706	}
707	break;
708	case FTP_EPRT_COMMAND:
709	/* Generate EPRT command string. */
710	#ifndef VBOX
711	sprintf(stemp, "EPRT \|1\|%d.%d.%d.%d\|%d\|\r\n",
712	a1, a2, a3, a4, ntohs(alias_port));
713	#else
714	RTStrPrintf(stemp, sizeof(stemp), "EPRT \|1\|%d.%d.%d.%d\|%d\|\r\n",
715	a1, a2, a3, a4, ntohs(alias_port));
716	#endif
717	break;
718	case FTP_229_REPLY:
719	/* Generate 229 reply string. */
720	#ifndef VBOX
721	sprintf(stemp, "229 Entering Extended Passive Mode (\|\|\|%d\|)\r\n",
722	ntohs(alias_port));
723	#else
724	RTStrPrintf(stemp, sizeof(stemp), "229 Entering Extended Passive Mode (\|\|\|%d\|)\r\n",
725	ntohs(alias_port));
726	#endif
727	break;
728	}
729
730	/* Save string length for IP header modification */
731	slen = (int)strlen(stemp);
732
733	/* Copy modified buffer into IP packet. */
734	sptr = (char *)pip;
735	sptr += hlen;
736	strncpy(sptr, stemp, maxpacketsize - hlen);
737	}
738
739	/* Save information regarding modified seq and ack numbers */
740	{
741	int delta;
742
743	SetAckModified(lnk);
744	delta = GetDeltaSeqOut(pip, lnk);
745	AddSeq(pip, lnk, delta + slen - dlen);
746	}
747
748	/* Revise IP header */
749	{
750	u_short new_len;
751
752	new_len = htons(hlen + slen);
753	DifferentialChecksum(&pip->ip_sum,
754	&new_len,
755	&pip->ip_len,
756	1);
757	pip->ip_len = new_len;
758	}
759
760	/* Compute TCP checksum for revised packet */
761	tc->th_sum = 0;
762	#ifdef _KERNEL
763	tc->th_x2 = 1;
764	#else
765	tc->th_sum = TcpChecksum(pip);
766	#endif
767	} else {
768	#ifdef LIBALIAS_DEBUG
769	fprintf(stderr,
770	"PacketAlias/HandleFtpOut: Cannot allocate FTP data port\n");
771	#endif
772	}
773	}

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source: vbox/trunk/src/VBox/Devices/Network/slirp/libalias/alias_ftp.c@ 68421

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