alias_ftp.c@ 28023

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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	if (ah->dport == NULL \|\| ah->sport == NULL \|\| ah->lnk == NULL \|\|
119	ah->maxpktsize == 0)
120	return (-1);
121	if (ntohs(*ah->dport) == FTP_CONTROL_PORT_NUMBER
122	\|\| ntohs(*ah->sport) == FTP_CONTROL_PORT_NUMBER)
123	return (0);
124	return (-1);
125	}
126
127	static int
128	protohandler(struct libalias la, struct ip pip, struct alias_data *ah)
129	{
130
131	AliasHandleFtpOut(la, pip, ah->lnk, ah->maxpktsize);
132	return (0);
133	}
134
135	#ifndef VBOX
136	struct proto_handler handlers[] = {
137	{
138	.pri = 80,
139	.dir = OUT,
140	.proto = TCP,
141	.fingerprint = &fingerprint,
142	.protohandler = &protohandler
143	},
144	{ EOH }
145	};
146	#else /* !VBOX */
147	#define handlers pData->ftp_module
148	#endif /* VBOX */
149
150	#ifndef VBOX
151	static int
152	mod_handler(module_t mod, int type, void *data)
153	#else
154	static int ftp_alias_handler(PNATState pData, int type);
155
156	int
157	ftp_alias_load(PNATState pData)
158	{
159	return ftp_alias_handler(pData, MOD_LOAD);
160	}
161
162	int
163	ftp_alias_unload(PNATState pData)
164	{
165	return ftp_alias_handler(pData, MOD_UNLOAD);
166	}
167	static int
168	ftp_alias_handler(PNATState pData, int type)
169	#endif
170	{
171	int error;
172	#ifdef VBOX
173	if (handlers == NULL)
174	handlers = RTMemAllocZ(2 * sizeof(struct proto_handler));
175	handlers[0].pri = 80;
176	handlers[0].dir = OUT;
177	handlers[0].proto = TCP;
178	handlers[0].fingerprint = &fingerprint;
179	handlers[0].protohandler = &protohandler;
180	handlers[1].pri = EOH;
181	#endif /* VBOX */
182
183	switch (type) {
184	case MOD_LOAD:
185	error = 0;
186	#ifdef VBOX
187	LibAliasAttachHandlers(pData, handlers);
188	#else
189	LibAliasAttachHandlers(handlers);
190	#endif
191	break;
192	case MOD_UNLOAD:
193	error = 0;
194	#ifdef VBOX
195	LibAliasDetachHandlers(pData, handlers);
196	RTMemFree(handlers);
197	handlers = NULL;
198	#else
199	LibAliasDetachHandlers(handlers);
200	#endif
201	break;
202	default:
203	error = EINVAL;
204	}
205	return (error);
206	}
207
208	#ifndef VBOX
209	#ifdef _KERNEL
210	static
211	#endif
212	moduledata_t alias_mod = {
213	"alias_ftp", mod_handler, NULL
214	};
215	#endif /!VBOX/
216
217	#ifdef _KERNEL
218	DECLARE_MODULE(alias_ftp, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
219	MODULE_VERSION(alias_ftp, 1);
220	MODULE_DEPEND(alias_ftp, libalias, 1, 1, 1);
221	#endif
222
223	#define FTP_CONTROL_PORT_NUMBER 21
224	#define MAX_MESSAGE_SIZE 128
225
226	/* FTP protocol flags. */
227	#define WAIT_CRLF 0x01
228
229	enum ftp_message_type {
230	FTP_PORT_COMMAND,
231	FTP_EPRT_COMMAND,
232	FTP_227_REPLY,
233	FTP_229_REPLY,
234	FTP_UNKNOWN_MESSAGE
235	};
236
237	static int ParseFtpPortCommand(struct libalias la, char , int);
238	static int ParseFtpEprtCommand(struct libalias la, char , int);
239	static int ParseFtp227Reply(struct libalias la, char , int);
240	static int ParseFtp229Reply(struct libalias la, char , int);
241	static void NewFtpMessage(struct libalias la, struct ip , struct alias_link *, int, int);
242
243	static void
244	AliasHandleFtpOut(
245	struct libalias *la,
246	struct ip pip, / IP packet to examine/patch */
247	struct alias_link lnk, / The link to go through (aliased port) */
248	int maxpacketsize /* The maximum size this packet can grow to
249	(including headers) */ )
250	{
251	int hlen, tlen, dlen, pflags;
252	char *sptr;
253	struct tcphdr *tc;
254	int ftp_message_type;
255
256	/* Calculate data length of TCP packet */
257	tc = (struct tcphdr *)ip_next(pip);
258	hlen = (pip->ip_hl + tc->th_off) << 2;
259	tlen = ntohs(pip->ip_len);
260	dlen = tlen - hlen;
261
262	/* Place string pointer and beginning of data */
263	sptr = (char *)pip;
264	sptr += hlen;
265
266	/*
267	* Check that data length is not too long and previous message was
268	* properly terminated with CRLF.
269	*/
270	pflags = GetProtocolFlags(lnk);
271	if (dlen <= MAX_MESSAGE_SIZE && !(pflags & WAIT_CRLF)) {
272	ftp_message_type = FTP_UNKNOWN_MESSAGE;
273
274	if (ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER) {
275	/*
276	* When aliasing a client, check for the PORT/EPRT command.
277	*/
278	if (ParseFtpPortCommand(la, sptr, dlen))
279	ftp_message_type = FTP_PORT_COMMAND;
280	else if (ParseFtpEprtCommand(la, sptr, dlen))
281	ftp_message_type = FTP_EPRT_COMMAND;
282	} else {
283	/*
284	* When aliasing a server, check for the 227/229 reply.
285	*/
286	if (ParseFtp227Reply(la, sptr, dlen))
287	ftp_message_type = FTP_227_REPLY;
288	else if (ParseFtp229Reply(la, sptr, dlen)) {
289	ftp_message_type = FTP_229_REPLY;
290	la->true_addr.s_addr = pip->ip_src.s_addr;
291	}
292	}
293
294	if (ftp_message_type != FTP_UNKNOWN_MESSAGE)
295	NewFtpMessage(la, pip, lnk, maxpacketsize, ftp_message_type);
296	}
297	/* Track the msgs which are CRLF term'd for PORT/PASV FW breach */
298
299	if (dlen) { /* only if there's data */
300	sptr = (char )pip; / start over at beginning */
301	tlen = ntohs(pip->ip_len); /* recalc tlen, pkt may
302	* have grown */
303	if (sptr[tlen - 2] == '\r' && sptr[tlen - 1] == '\n')
304	pflags &= ~WAIT_CRLF;
305	else
306	pflags \|= WAIT_CRLF;
307	SetProtocolFlags(lnk, pflags);
308	}
309	}
310
311	static int
312	ParseFtpPortCommand(struct libalias la, char sptr, int dlen)
313	{
314	char ch;
315	int i, state;
316	u_int32_t addr;
317	u_short port;
318	u_int8_t octet;
319
320	/* Format: "PORT A,D,D,R,PO,RT". */
321
322	/* Return if data length is too short. */
323	if (dlen < 18)
324	return (0);
325
326	if (strncasecmp("PORT ", sptr, 5))
327	return (0);
328
329	addr = port = octet = 0;
330	state = 0;
331	for (i = 5; i < dlen; i++) {
332	ch = sptr[i];
333	switch (state) {
334	case 0:
335	if (isspace(ch))
336	break;
337	else
338	state++;
339	case 1:
340	case 3:
341	case 5:
342	case 7:
343	case 9:
344	case 11:
345	if (isdigit(ch)) {
346	octet = ch - '0';
347	state++;
348	} else
349	return (0);
350	break;
351	case 2:
352	case 4:
353	case 6:
354	case 8:
355	if (isdigit(ch))
356	octet = 10 * octet + ch - '0';
357	else if (ch == ',') {
358	addr = (addr << 8) + octet;
359	state++;
360	} else
361	return (0);
362	break;
363	case 10:
364	case 12:
365	if (isdigit(ch))
366	octet = 10 * octet + ch - '0';
367	else if (ch == ',' \|\| state == 12) {
368	port = (port << 8) + octet;
369	state++;
370	} else
371	return (0);
372	break;
373	}
374	}
375
376	if (state == 13) {
377	la->true_addr.s_addr = htonl(addr);
378	la->true_port = port;
379	return (1);
380	} else
381	return (0);
382	}
383
384	static int
385	ParseFtpEprtCommand(struct libalias la, char sptr, int dlen)
386	{
387	char ch, delim;
388	int i, state;
389	u_int32_t addr;
390	u_short port;
391	u_int8_t octet;
392
393	/* Format: "EPRT \|1\|A.D.D.R\|PORT\|". */
394
395	/* Return if data length is too short. */
396	if (dlen < 18)
397	return (0);
398
399	if (strncasecmp("EPRT ", sptr, 5))
400	return (0);
401
402	addr = port = octet = 0;
403	delim = '\|'; /* XXX gcc -Wuninitialized */
404	state = 0;
405	for (i = 5; i < dlen; i++) {
406	ch = sptr[i];
407	switch (state) {
408	case 0:
409	if (!isspace(ch)) {
410	delim = ch;
411	state++;
412	}
413	break;
414	case 1:
415	if (ch == '1') /* IPv4 address */
416	state++;
417	else
418	return (0);
419	break;
420	case 2:
421	if (ch == delim)
422	state++;
423	else
424	return (0);
425	break;
426	case 3:
427	case 5:
428	case 7:
429	case 9:
430	if (isdigit(ch)) {
431	octet = ch - '0';
432	state++;
433	} else
434	return (0);
435	break;
436	case 4:
437	case 6:
438	case 8:
439	case 10:
440	if (isdigit(ch))
441	octet = 10 * octet + ch - '0';
442	else if (ch == '.' \|\| state == 10) {
443	addr = (addr << 8) + octet;
444	state++;
445	} else
446	return (0);
447	break;
448	case 11:
449	if (isdigit(ch)) {
450	port = ch - '0';
451	state++;
452	} else
453	return (0);
454	break;
455	case 12:
456	if (isdigit(ch))
457	port = 10 * port + ch - '0';
458	else if (ch == delim)
459	state++;
460	else
461	return (0);
462	break;
463	}
464	}
465
466	if (state == 13) {
467	la->true_addr.s_addr = htonl(addr);
468	la->true_port = port;
469	return (1);
470	} else
471	return (0);
472	}
473
474	static int
475	ParseFtp227Reply(struct libalias la, char sptr, int dlen)
476	{
477	char ch;
478	int i, state;
479	u_int32_t addr;
480	u_short port;
481	u_int8_t octet;
482
483	/* Format: "227 Entering Passive Mode (A,D,D,R,PO,RT)" */
484
485	/* Return if data length is too short. */
486	if (dlen < 17)
487	return (0);
488
489	if (strncmp("227 ", sptr, 4))
490	return (0);
491
492	addr = port = octet = 0;
493
494	state = 0;
495	for (i = 4; i < dlen; i++) {
496	ch = sptr[i];
497	switch (state) {
498	case 0:
499	if (ch == '(')
500	state++;
501	break;
502	case 1:
503	case 3:
504	case 5:
505	case 7:
506	case 9:
507	case 11:
508	if (isdigit(ch)) {
509	octet = ch - '0';
510	state++;
511	} else
512	return (0);
513	break;
514	case 2:
515	case 4:
516	case 6:
517	case 8:
518	if (isdigit(ch))
519	octet = 10 * octet + ch - '0';
520	else if (ch == ',') {
521	addr = (addr << 8) + octet;
522	state++;
523	} else
524	return (0);
525	break;
526	case 10:
527	case 12:
528	if (isdigit(ch))
529	octet = 10 * octet + ch - '0';
530	else if (ch == ',' \|\| (state == 12 && ch == ')')) {
531	port = (port << 8) + octet;
532	state++;
533	} else
534	return (0);
535	break;
536	}
537	}
538
539	if (state == 13) {
540	la->true_port = port;
541	la->true_addr.s_addr = htonl(addr);
542	return (1);
543	} else
544	return (0);
545	}
546
547	static int
548	ParseFtp229Reply(struct libalias la, char sptr, int dlen)
549	{
550	char ch, delim;
551	int i, state;
552	u_short port;
553
554	/* Format: "229 Entering Extended Passive Mode (\|\|\|PORT\|)" */
555
556	/* Return if data length is too short. */
557	if (dlen < 11)
558	return (0);
559
560	if (strncmp("229 ", sptr, 4))
561	return (0);
562
563	port = 0;
564	delim = '\|'; /* XXX gcc -Wuninitialized */
565
566	state = 0;
567	for (i = 4; i < dlen; i++) {
568	ch = sptr[i];
569	switch (state) {
570	case 0:
571	if (ch == '(')
572	state++;
573	break;
574	case 1:
575	delim = ch;
576	state++;
577	break;
578	case 2:
579	case 3:
580	if (ch == delim)
581	state++;
582	else
583	return (0);
584	break;
585	case 4:
586	if (isdigit(ch)) {
587	port = ch - '0';
588	state++;
589	} else
590	return (0);
591	break;
592	case 5:
593	if (isdigit(ch))
594	port = 10 * port + ch - '0';
595	else if (ch == delim)
596	state++;
597	else
598	return (0);
599	break;
600	case 6:
601	if (ch == ')')
602	state++;
603	else
604	return (0);
605	break;
606	}
607	}
608
609	if (state == 7) {
610	la->true_port = port;
611	return (1);
612	} else
613	return (0);
614	}
615
616	static void
617	NewFtpMessage(struct libalias la, struct ip pip,
618	struct alias_link *lnk,
619	int maxpacketsize,
620	int ftp_message_type)
621	{
622	struct alias_link *ftp_lnk;
623
624	/* Security checks. */
625	if (pip->ip_src.s_addr != la->true_addr.s_addr)
626	return;
627
628	if (la->true_port < IPPORT_RESERVED)
629	return;
630
631	/* Establish link to address and port found in FTP control message. */
632	ftp_lnk = FindUdpTcpOut(la, la->true_addr, GetDestAddress(lnk),
633	htons(la->true_port), 0, IPPROTO_TCP, 1);
634
635	if (ftp_lnk != NULL) {
636	int slen, hlen, tlen, dlen;
637	struct tcphdr *tc;
638
639	#ifndef NO_FW_PUNCH
640	/* Punch hole in firewall */
641	PunchFWHole(ftp_lnk);
642	#endif
643
644	/* Calculate data length of TCP packet */
645	tc = (struct tcphdr *)ip_next(pip);
646	hlen = (pip->ip_hl + tc->th_off) << 2;
647	tlen = ntohs(pip->ip_len);
648	dlen = tlen - hlen;
649
650	/* Create new FTP message. */
651	{
652	char stemp[MAX_MESSAGE_SIZE + 1];
653	char *sptr;
654	u_short alias_port;
655	u_char *ptr;
656	int a1, a2, a3, a4, p1, p2;
657	struct in_addr alias_address;
658
659	/* Decompose alias address into quad format */
660	alias_address = GetAliasAddress(lnk);
661	ptr = (u_char *) & alias_address.s_addr;
662	a1 = *ptr++;
663	a2 = *ptr++;
664	a3 = *ptr++;
665	a4 = *ptr;
666
667	alias_port = GetAliasPort(ftp_lnk);
668
669	/* Prepare new command */
670	switch (ftp_message_type) {
671	case FTP_PORT_COMMAND:
672	case FTP_227_REPLY:
673	/* Decompose alias port into pair format. */
674	ptr = (u_char *)&alias_port;
675	p1 = *ptr++;
676	p2 = *ptr;
677
678	if (ftp_message_type == FTP_PORT_COMMAND) {
679	/* Generate PORT command string. */
680	#ifndef VBOX
681	sprintf(stemp, "PORT %d,%d,%d,%d,%d,%d\r\n",
682	a1, a2, a3, a4, p1, p2);
683	#else
684	RTStrPrintf(stemp, sizeof(stemp), "PORT %d,%d,%d,%d,%d,%d\r\n",
685	a1, a2, a3, a4, p1, p2);
686	#endif
687	} else {
688	/* Generate 227 reply string. */
689	#ifndef VBOX
690	sprintf(stemp,
691	"227 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n",
692	a1, a2, a3, a4, p1, p2);
693	#else
694	RTStrPrintf(stemp, sizeof(stemp),
695	"227 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n",
696	a1, a2, a3, a4, p1, p2);
697	#endif
698	}
699	break;
700	case FTP_EPRT_COMMAND:
701	/* Generate EPRT command string. */
702	#ifndef VBOX
703	sprintf(stemp, "EPRT \|1\|%d.%d.%d.%d\|%d\|\r\n",
704	a1, a2, a3, a4, ntohs(alias_port));
705	#else
706	RTStrPrintf(stemp, sizeof(stemp), "EPRT \|1\|%d.%d.%d.%d\|%d\|\r\n",
707	a1, a2, a3, a4, ntohs(alias_port));
708	#endif
709	break;
710	case FTP_229_REPLY:
711	/* Generate 229 reply string. */
712	#ifndef VBOX
713	sprintf(stemp, "229 Entering Extended Passive Mode (\|\|\|%d\|)\r\n",
714	ntohs(alias_port));
715	#else
716	RTStrPrintf(stemp, sizeof(stemp), "229 Entering Extended Passive Mode (\|\|\|%d\|)\r\n",
717	ntohs(alias_port));
718	#endif
719	break;
720	}
721
722	/* Save string length for IP header modification */
723	slen = strlen(stemp);
724
725	/* Copy modified buffer into IP packet. */
726	sptr = (char *)pip;
727	sptr += hlen;
728	strncpy(sptr, stemp, maxpacketsize - hlen);
729	}
730
731	/* Save information regarding modified seq and ack numbers */
732	{
733	int delta;
734
735	SetAckModified(lnk);
736	delta = GetDeltaSeqOut(pip, lnk);
737	AddSeq(pip, lnk, delta + slen - dlen);
738	}
739
740	/* Revise IP header */
741	{
742	u_short new_len;
743
744	new_len = htons(hlen + slen);
745	DifferentialChecksum(&pip->ip_sum,
746	&new_len,
747	&pip->ip_len,
748	1);
749	pip->ip_len = new_len;
750	}
751
752	/* Compute TCP checksum for revised packet */
753	tc->th_sum = 0;
754	#ifdef _KERNEL
755	tc->th_x2 = 1;
756	#else
757	tc->th_sum = TcpChecksum(pip);
758	#endif
759	} else {
760	#ifdef LIBALIAS_DEBUG
761	fprintf(stderr,
762	"PacketAlias/HandleFtpOut: Cannot allocate FTP data port\n");
763	#endif
764	}
765	}

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source: vbox/trunk/src/VBox/Devices/Network/slirp/libalias/alias_ftp.c@ 28023

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