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-rw-r--r--src/nat/gnunet-helper-nat-server.c714
1 files changed, 0 insertions, 714 deletions
diff --git a/src/nat/gnunet-helper-nat-server.c b/src/nat/gnunet-helper-nat-server.c
deleted file mode 100644
index 38d7d22c8..000000000
--- a/src/nat/gnunet-helper-nat-server.c
+++ /dev/null
@@ -1,714 +0,0 @@
1/*
2 This file is part of GNUnet.
3 Copyright (C) 2010 GNUnet e.V.
4
5 GNUnet is free software: you can redistribute it and/or modify it
6 under the terms of the GNU Affero General Public License as published
7 by the Free Software Foundation, either version 3 of the License,
8 or (at your option) any later version.
9
10 GNUnet is distributed in the hope that it will be useful, but
11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Affero General Public License for more details.
14
15 You should have received a copy of the GNU Affero General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
17
18 SPDX-License-Identifier: AGPL3.0-or-later
19 */
20
21/**
22 * @file src/nat/gnunet-helper-nat-server.c
23 * @brief Tool to help bypass NATs using ICMP method; must run as root (SUID will do)
24 * This code will work under GNU/Linux only (or maybe BSDs, but never W32)
25 * @author Christian Grothoff
26 *
27 * This program will send ONE ICMP message every 500 ms RAW sockets
28 * to a DUMMY IP address and also listens for ICMP replies. Since
29 * it uses RAW sockets, it must be installed SUID or run as 'root'.
30 * In order to keep the security risk of the resulting SUID binary
31 * minimal, the program ONLY opens the two RAW sockets with root
32 * privileges, then drops them and only then starts to process
33 * command line arguments. The code also does not link against
34 * any shared libraries (except libc) and is strictly minimal
35 * (except for checking for errors). The following list of people
36 * have reviewed this code and considered it safe since the last
37 * modification (if you reviewed it, please have your name added
38 * to the list):
39 *
40 * - Christian Grothoff
41 * - Nathan Evans
42 * - Benjamin Kuperman (22 Aug 2010)
43 * - Jacob Appelbaum (19 Dec 2011)
44 */
45#if HAVE_CONFIG_H
46/* Just needed for HAVE_SOCKADDR_IN_SIN_LEN test macro! */
47#include "gnunet_config.h"
48#else
49#define _GNU_SOURCE
50#endif
51#include <sys/types.h>
52#include <sys/socket.h>
53#include <arpa/inet.h>
54#include <sys/select.h>
55#include <sys/time.h>
56#include <sys/types.h>
57#include <unistd.h>
58#include <stdio.h>
59#include <string.h>
60#include <errno.h>
61#include <stdlib.h>
62#include <stdint.h>
63#include <time.h>
64#include <netinet/ip.h>
65#include <netinet/ip_icmp.h>
66#include <netinet/in.h>
67
68/* The following constant is missing from FreeBSD 9.2 */
69#ifndef ICMP_TIME_EXCEEDED
70#define ICMP_TIME_EXCEEDED 11
71#endif
72
73/**
74 * Call memcpy() but check for @a n being 0 first. In the latter
75 * case, it is now safe to pass NULL for @a src or @a dst.
76 * Unlike traditional memcpy(), returns nothing.
77 *
78 * @param dst destination of the copy, may be NULL if @a n is zero
79 * @param src source of the copy, may be NULL if @a n is zero
80 * @param n number of bytes to copy
81 */
82#define GNUNET_memcpy(dst, src, n) do { if (0 != n) { (void) memcpy (dst, src, \
83 n); \
84 } } while (0)
85
86/**
87 * Should we print some debug output?
88 */
89#define VERBOSE 0
90
91/**
92 * Must match packet ID used by gnunet-helper-nat-client.c
93 */
94#define PACKET_ID 256
95
96/**
97 * Must match IP given in the client.
98 */
99#define DUMMY_IP "192.0.2.86"
100
101/**
102 * Port for UDP
103 */
104#define NAT_TRAV_PORT 22225
105
106/**
107 * How often do we send our ICMP messages to receive replies?
108 */
109#define ICMP_SEND_FREQUENCY_MS 500
110
111/**
112 * IPv4 header.
113 */
114struct ip_header
115{
116 /**
117 * Version (4 bits) + Internet header length (4 bits)
118 */
119 uint8_t vers_ihl;
120
121 /**
122 * Type of service
123 */
124 uint8_t tos;
125
126 /**
127 * Total length
128 */
129 uint16_t pkt_len;
130
131 /**
132 * Identification
133 */
134 uint16_t id;
135
136 /**
137 * Flags (3 bits) + Fragment offset (13 bits)
138 */
139 uint16_t flags_frag_offset;
140
141 /**
142 * Time to live
143 */
144 uint8_t ttl;
145
146 /**
147 * Protocol
148 */
149 uint8_t proto;
150
151 /**
152 * Header checksum
153 */
154 uint16_t checksum;
155
156 /**
157 * Source address
158 */
159 uint32_t src_ip;
160
161 /**
162 * Destination address
163 */
164 uint32_t dst_ip;
165};
166
167/**
168 * Format of ICMP packet.
169 */
170struct icmp_ttl_exceeded_header
171{
172 uint8_t type;
173
174 uint8_t code;
175
176 uint16_t checksum;
177
178 uint32_t unused;
179
180 /* followed by original payload */
181};
182
183struct icmp_echo_header
184{
185 uint8_t type;
186
187 uint8_t code;
188
189 uint16_t checksum;
190
191 uint32_t reserved;
192};
193
194
195/**
196 * Beginning of UDP packet.
197 */
198struct udp_header
199{
200 uint16_t src_port;
201
202 uint16_t dst_port;
203
204 uint16_t length;
205
206 uint16_t crc;
207};
208
209/**
210 * Socket we use to receive "fake" ICMP replies.
211 */
212static int icmpsock;
213
214/**
215 * Socket we use to send our ICMP requests.
216 */
217static int rawsock;
218
219/**
220 * Socket we use to send our UDP requests.
221 */
222static int udpsock;
223
224/**
225 * Target "dummy" address.
226 */
227static struct in_addr dummy;
228
229
230/**
231 * CRC-16 for IP/ICMP headers.
232 *
233 * @param data what to calculate the CRC over
234 * @param bytes number of bytes in data (must be multiple of 2)
235 * @return the CRC 16.
236 */
237static uint16_t
238calc_checksum (const uint16_t *data, unsigned int bytes)
239{
240 uint32_t sum;
241 unsigned int i;
242
243 sum = 0;
244 for (i = 0; i < bytes / 2; i++)
245 sum += data[i];
246 sum = (sum & 0xffff) + (sum >> 16);
247 sum = htons (0xffff - sum);
248 return sum;
249}
250
251
252/**
253 * Send an ICMP message to the dummy IP.
254 *
255 * @param my_ip source address (our ip address)
256 */
257static void
258send_icmp_echo (const struct in_addr *my_ip)
259{
260 char packet[sizeof(struct ip_header) + sizeof(struct icmp_echo_header)];
261 struct icmp_echo_header icmp_echo;
262 struct ip_header ip_pkt;
263 struct sockaddr_in dst;
264 size_t off;
265 int err;
266
267 off = 0;
268 ip_pkt.vers_ihl = 0x45;
269 ip_pkt.tos = 0;
270 ip_pkt.pkt_len = htons (sizeof(packet));
271 ip_pkt.id = htons (PACKET_ID);
272 ip_pkt.flags_frag_offset = 0;
273 ip_pkt.ttl = IPDEFTTL;
274 ip_pkt.proto = IPPROTO_ICMP;
275 ip_pkt.checksum = 0;
276 ip_pkt.src_ip = my_ip->s_addr;
277 ip_pkt.dst_ip = dummy.s_addr;
278 ip_pkt.checksum =
279 htons (calc_checksum ((uint16_t *) &ip_pkt,
280 sizeof(struct ip_header)));
281 GNUNET_memcpy (&packet[off],
282 &ip_pkt,
283 sizeof(struct ip_header));
284 off += sizeof(struct ip_header);
285
286 icmp_echo.type = ICMP_ECHO;
287 icmp_echo.code = 0;
288 icmp_echo.checksum = 0;
289 icmp_echo.reserved = 0;
290 icmp_echo.checksum =
291 htons (calc_checksum
292 ((uint16_t *) &icmp_echo,
293 sizeof(struct icmp_echo_header)));
294 GNUNET_memcpy (&packet[off],
295 &icmp_echo,
296 sizeof(struct icmp_echo_header));
297 off += sizeof(struct icmp_echo_header);
298
299 memset (&dst, 0, sizeof(dst));
300 dst.sin_family = AF_INET;
301#if HAVE_SOCKADDR_IN_SIN_LEN
302 dst.sin_len = sizeof(struct sockaddr_in);
303#endif
304 dst.sin_addr = dummy;
305 err = sendto (rawsock,
306 packet,
307 off,
308 0,
309 (struct sockaddr *) &dst,
310 sizeof(dst));
311 if (err < 0)
312 {
313#if VERBOSE
314 fprintf (stderr,
315 "sendto failed: %s\n",
316 strerror (errno));
317#endif
318 }
319 else if (sizeof(packet) != err)
320 {
321 fprintf (stderr,
322 "Error: partial send of ICMP message\n");
323 }
324}
325
326
327/**
328 * Send a UDP message to the dummy IP.
329 */
330static void
331send_udp ()
332{
333 struct sockaddr_in dst;
334 ssize_t err;
335
336 memset (&dst, 0, sizeof(dst));
337 dst.sin_family = AF_INET;
338#if HAVE_SOCKADDR_IN_SIN_LEN
339 dst.sin_len = sizeof(struct sockaddr_in);
340#endif
341 dst.sin_addr = dummy;
342 dst.sin_port = htons (NAT_TRAV_PORT);
343 err = sendto (udpsock,
344 NULL,
345 0,
346 0,
347 (struct sockaddr *) &dst,
348 sizeof(dst));
349 if (err < 0)
350 {
351#if VERBOSE
352 fprintf (stderr,
353 "sendto failed: %s\n",
354 strerror (errno));
355#endif
356 }
357 else if (0 != err)
358 {
359 fprintf (stderr,
360 "Error: partial send of ICMP message\n");
361 }
362}
363
364
365/**
366 * We've received an ICMP response. Process it.
367 */
368static void
369process_icmp_response ()
370{
371 char buf[65536];
372 ssize_t have;
373 struct in_addr source_ip;
374 struct ip_header ip_pkt;
375 struct icmp_ttl_exceeded_header icmp_ttl;
376 struct icmp_echo_header icmp_echo;
377 struct udp_header udp_pkt;
378 size_t off;
379 uint16_t port;
380
381 have = read (icmpsock, buf, sizeof(buf));
382 if (-1 == have)
383 {
384 fprintf (stderr,
385 "Error reading raw socket: %s\n",
386 strerror (errno));
387 return;
388 }
389#if VERBOSE
390 fprintf (stderr,
391 "Received message of %u bytes\n",
392 (unsigned int) have);
393#endif
394 if (have <
395 (ssize_t) (sizeof(struct ip_header)
396 + sizeof(struct icmp_ttl_exceeded_header)
397 + sizeof(struct ip_header)))
398 {
399 /* malformed */
400 return;
401 }
402 off = 0;
403 GNUNET_memcpy (&ip_pkt,
404 &buf[off],
405 sizeof(struct ip_header));
406 off += sizeof(struct ip_header);
407 GNUNET_memcpy (&icmp_ttl,
408 &buf[off],
409 sizeof(struct icmp_ttl_exceeded_header));
410 off += sizeof(struct icmp_ttl_exceeded_header);
411 if ((ICMP_TIME_EXCEEDED != icmp_ttl.type) || (0 != icmp_ttl.code))
412 {
413 /* different type than what we want */
414 return;
415 }
416 /* grab source IP of 1st IP header */
417 source_ip.s_addr = ip_pkt.src_ip;
418
419 /* skip 2nd IP header */
420 GNUNET_memcpy (&ip_pkt,
421 &buf[off],
422 sizeof(struct ip_header));
423 off += sizeof(struct ip_header);
424
425 switch (ip_pkt.proto)
426 {
427 case IPPROTO_ICMP:
428 if (have !=
429 (sizeof(struct ip_header) * 2
430 + sizeof(struct icmp_ttl_exceeded_header)
431 + sizeof(struct icmp_echo_header)))
432 {
433 /* malformed */
434 return;
435 }
436 /* grab ICMP ECHO content */
437 GNUNET_memcpy (&icmp_echo,
438 &buf[off],
439 sizeof(struct icmp_echo_header));
440 port = (uint16_t) ntohl (icmp_echo.reserved);
441 break;
442
443 case IPPROTO_UDP:
444 if (have !=
445 (sizeof(struct ip_header) * 2
446 + sizeof(struct icmp_ttl_exceeded_header) + sizeof(struct udp_header)))
447 {
448 /* malformed */
449 return;
450 }
451 /* grab UDP content */
452 GNUNET_memcpy (&udp_pkt,
453 &buf[off],
454 sizeof(struct udp_header));
455 port = ntohs (udp_pkt.length);
456 break;
457
458 default:
459 /* different type than what we want */
460 return;
461 }
462
463 if (port == 0)
464 fprintf (stdout, "%s\n",
465 inet_ntop (AF_INET, &source_ip, buf, sizeof(buf)));
466 else
467 fprintf (stdout, "%s:%u\n",
468 inet_ntop (AF_INET, &source_ip, buf, sizeof(buf)),
469 (unsigned int) port);
470 fflush (stdout);
471}
472
473
474/**
475 * Fully initialize the raw socket.
476 *
477 * @return -1 on error, 0 on success
478 */
479static int
480setup_raw_socket ()
481{
482 const int one = 1;
483
484 if (-1 ==
485 setsockopt (rawsock,
486 SOL_SOCKET,
487 SO_BROADCAST,
488 (char *) &one,
489 sizeof(one)))
490 {
491 fprintf (stderr,
492 "setsockopt failed: %s\n",
493 strerror (errno));
494 return -1;
495 }
496 if (-1 ==
497 setsockopt (rawsock,
498 IPPROTO_IP,
499 IP_HDRINCL,
500 (char *) &one,
501 sizeof(one)))
502 {
503 fprintf (stderr,
504 "setsockopt failed: %s\n",
505 strerror (errno));
506 return -1;
507 }
508 return 0;
509}
510
511
512/**
513 * Create a UDP socket for writing.
514 *
515 * @param my_ip source address (our ip address)
516 * @return -1 on error
517 */
518static int
519make_udp_socket (const struct in_addr *my_ip)
520{
521 int ret;
522 struct sockaddr_in addr;
523
524 ret = socket (AF_INET, SOCK_DGRAM, 0);
525 if (-1 == ret)
526 {
527 fprintf (stderr,
528 "Error opening UDP socket: %s\n",
529 strerror (errno));
530 return -1;
531 }
532 memset (&addr, 0, sizeof(addr));
533 addr.sin_family = AF_INET;
534#if HAVE_SOCKADDR_IN_SIN_LEN
535 addr.sin_len = sizeof(struct sockaddr_in);
536#endif
537 addr.sin_addr = *my_ip;
538 addr.sin_port = htons (NAT_TRAV_PORT);
539
540 if (0 != bind (ret,
541 (struct sockaddr *) &addr,
542 sizeof(addr)))
543 {
544 fprintf (stderr,
545 "Error binding UDP socket to port %u: %s\n",
546 NAT_TRAV_PORT,
547 strerror (errno));
548 (void) close (ret);
549 return -1;
550 }
551 return ret;
552}
553
554
555int
556main (int argc,
557 char *const *argv)
558{
559 struct in_addr external;
560 fd_set rs;
561 struct timeval tv;
562 uid_t uid;
563 unsigned int alt;
564 int icmp_eno;
565 int raw_eno;
566 int global_ret;
567
568 /* Create an ICMP raw socket for reading (we'll check errors later) */
569 icmpsock = socket (AF_INET,
570 SOCK_RAW,
571 IPPROTO_ICMP);
572 icmp_eno = errno;
573
574 /* Create an (ICMP) raw socket for writing (we'll check errors later) */
575 rawsock = socket (AF_INET,
576 SOCK_RAW,
577 IPPROTO_RAW);
578 raw_eno = errno;
579 udpsock = -1;
580
581 /* drop root rights */
582 uid = getuid ();
583#ifdef HAVE_SETRESUID
584 if (0 != setresuid (uid, uid, uid))
585 {
586 fprintf (stderr,
587 "Failed to setresuid: %s\n",
588 strerror (errno));
589 global_ret = 1;
590 goto error_exit;
591 }
592#else
593 if (0 != (setuid (uid) | seteuid (uid)))
594 {
595 fprintf (stderr,
596 "Failed to setuid: %s\n",
597 strerror (errno));
598 global_ret = 2;
599 goto error_exit;
600 }
601#endif
602
603 /* Now that we run without root rights, we can do error checking... */
604 if (2 != argc)
605 {
606 fprintf (stderr,
607 "This program must be started with our (internal NAT) IP as the only argument.\n");
608 global_ret = 3;
609 goto error_exit;
610 }
611 if (1 != inet_pton (AF_INET, argv[1], &external))
612 {
613 fprintf (stderr,
614 "Error parsing IPv4 address: %s\n",
615 strerror (errno));
616 global_ret = 4;
617 goto error_exit;
618 }
619 if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
620 {
621 fprintf (stderr,
622 "Internal error converting dummy IP to binary.\n");
623 global_ret = 5;
624 goto error_exit;
625 }
626
627 /* error checking icmpsock */
628 if (-1 == icmpsock)
629 {
630 fprintf (stderr,
631 "Error opening RAW socket: %s\n",
632 strerror (icmp_eno));
633 global_ret = 6;
634 goto error_exit;
635 }
636 if (icmpsock >= FD_SETSIZE)
637 {
638 /* this could happen if we were started with a large number of already-open
639 file descriptors... */
640 fprintf (stderr,
641 "Socket number too large (%d > %u)\n",
642 icmpsock,
643 (unsigned int) FD_SETSIZE);
644 global_ret = 7;
645 goto error_exit;
646 }
647
648 /* error checking rawsock */
649 if (-1 == rawsock)
650 {
651 fprintf (stderr,
652 "Error opening RAW socket: %s\n",
653 strerror (raw_eno));
654 global_ret = 8;
655 goto error_exit;
656 }
657 /* no need to check 'rawsock' against FD_SETSIZE as it is never used
658 with 'select' */
659
660 if (0 != setup_raw_socket ())
661 {
662 global_ret = 9;
663 goto error_exit;
664 }
665
666 if (-1 == (udpsock = make_udp_socket (&external)))
667 {
668 global_ret = 10;
669 goto error_exit;
670 }
671
672 alt = 0;
673 while (1)
674 {
675 FD_ZERO (&rs);
676 FD_SET (icmpsock, &rs);
677 tv.tv_sec = 0;
678 tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
679 if (-1 == select (icmpsock + 1, &rs, NULL, NULL, &tv))
680 {
681 if (errno == EINTR)
682 continue;
683 fprintf (stderr,
684 "select failed: %s\n",
685 strerror (errno));
686 break;
687 }
688 if (1 == getppid ()) /* Check the parent process id, if 1 the parent has died, so we should die too */
689 break;
690 if (FD_ISSET (icmpsock, &rs))
691 {
692 process_icmp_response ();
693 continue;
694 }
695 if (0 == (++alt % 2))
696 send_icmp_echo (&external);
697 else
698 send_udp ();
699 }
700
701 /* select failed (internal error or OS out of resources) */
702 global_ret = 11;
703error_exit:
704 if (-1 != icmpsock)
705 (void) close (icmpsock);
706 if (-1 != rawsock)
707 (void) close (rawsock);
708 if (-1 != udpsock)
709 (void) close (udpsock);
710 return global_ret;
711}
712
713
714/* end of gnunet-helper-nat-server.c */
generated by cgit v1.2.3 (git 2.39.1) at 2024-04-26 12:42:41 +0000