2 This file is part of GNUnet.
3 (C) 2010 Christian Grothoff (and other contributing authors)
5 GNUnet is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published
7 by the Free Software Foundation; either version 3, or (at your
8 option) any later version.
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 General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with GNUnet; see the file COPYING. If not, write to the
17 Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA.
22 * @file src/transport/gnunet-nat-client-windows.c
23 * @brief Tool to help bypass NATs using ICMP method; must run as
24 * root (SUID will do) or administrator on W32
25 * This code will work under GNU/Linux or W32.
26 * @author Nathan Evans
28 * This program will send ONE ICMP message using RAW sockets
29 * to the IP address specified as the second argument. Since
30 * it uses RAW sockets, it must be installed SUID or run as 'root'.
31 * In order to keep the security risk of the resulting SUID binary
32 * minimal, the program ONLY opens the RAW socket with root
33 * privileges, then drops them and only then starts to process
34 * command line arguments. The code also does not link against
35 * any shared libraries (except libc) and is strictly minimal
36 * (except for checking for errors). The following list of people
37 * have reviewed this code and considered it safe since the last
38 * modification (if you reviewed it, please have your name added
41 * - Christian Grothoff
49 #include <sys/types.h>
61 #define ICMP_TIME_EXCEEDED 11
64 * Must match IP given in the server.
66 #define DUMMY_IP "192.0.2.86"
68 #define NAT_TRAV_PORT 22225
77 * Version (4 bits) + Internet header length (4 bits)
97 * Flags (3 bits) + Fragment offset (13 bits)
99 uint16_t flags_frag_offset;
122 * Destination address
129 * Format of ICMP packet.
142 struct icmp_echo_packet
152 * Beginning of UDP packet.
165 * Socket we use to send our ICMP packets.
167 static SOCKET rawsock;
170 * Target "dummy" address.
172 static struct in_addr dummy;
174 static uint16_t port;
179 * Convert IPv4 address from text to binary form.
181 * @param af address family
182 * @param cp the address to print
183 * @param buf where to write the address result
184 * @return 1 on success
191 buf->s_addr = inet_addr(cp);
192 if (buf->s_addr == INADDR_NONE)
195 "Error %d handling address %s",
205 * CRC-16 for IP/ICMP headers.
207 * @param data what to calculate the CRC over
208 * @param bytes number of bytes in data (must be multiple of 2)
209 * @return the CRC 16.
212 calc_checksum(const uint16_t *data,
219 for (i=0;i<bytes/2;i++)
221 sum = (sum & 0xffff) + (sum >> 16);
222 sum = htons(0xffff - sum);
228 * Send an ICMP message to the target.
230 * @param my_ip source address
231 * @param other target address
234 send_icmp_udp (const struct in_addr *my_ip,
235 const struct in_addr *other)
237 struct ip_packet ip_pkt;
238 struct icmp_packet icmp_pkt;
239 struct udp_packet udp_pkt;
241 struct sockaddr_in dst;
242 char packet[sizeof(ip_pkt) * 2 + sizeof(icmp_pkt) * 2 + sizeof(uint32_t)];
247 /* ip header: send to (known) ip address */
249 memset(&ip_pkt, 0, sizeof(ip_pkt));
250 ip_pkt.vers_ihl = 0x45;
252 ip_pkt.pkt_len = htons(sizeof (packet));
253 ip_pkt.id = htons(256);
254 ip_pkt.flags_frag_offset = 0;
256 ip_pkt.proto = IPPROTO_ICMP;
258 ip_pkt.src_ip = my_ip->s_addr;
259 ip_pkt.dst_ip = other->s_addr;
260 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
261 memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
262 off += sizeof(ip_pkt);
264 /* ip header of the presumably 'lost' udp packet */
265 ip_pkt.vers_ihl = 0x45;
267 ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
269 icmp_pkt.type = 11; /* TTL exceeded */
271 icmp_pkt.checksum = 0;
272 icmp_pkt.reserved = 0;
273 memcpy(&packet[off], &icmp_pkt, sizeof(icmp_pkt));
274 off += sizeof(icmp_pkt);
276 /* build inner IP header */
277 memset(&ip_pkt, 0, sizeof(ip_pkt));
278 ip_pkt.vers_ihl = 0x45;
280 ip_pkt.pkt_len = htons(sizeof (ip_pkt) + sizeof(udp_pkt));
281 ip_pkt.id = htons(0);
282 ip_pkt.flags_frag_offset = 0;
284 ip_pkt.proto = IPPROTO_UDP;
286 ip_pkt.src_ip = other->s_addr;
287 ip_pkt.dst_ip = dummy.s_addr;
288 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
289 memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
290 off += sizeof(ip_pkt);
292 /* build UDP header */
293 udp_pkt.src_port = htons(NAT_TRAV_PORT);
294 udp_pkt.dst_port = htons(NAT_TRAV_PORT);
296 memset(&udp_pkt.length, 0, sizeof(uint32_t));
297 udp_pkt.length = htons (port);
298 memcpy(&packet[off], &udp_pkt, sizeof(udp_pkt));
299 off += sizeof(udp_pkt);
301 /* set ICMP checksum */
302 icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[sizeof(ip_pkt)],
303 sizeof (icmp_pkt) + sizeof(ip_pkt) + sizeof(udp_pkt)));
304 memcpy (&packet[sizeof(ip_pkt)], &icmp_pkt, sizeof (icmp_pkt));
307 memset (&dst, 0, sizeof (dst));
308 dst.sin_family = AF_INET;
309 dst.sin_addr = *other;
310 err = sendto(rawsock,
313 (struct sockaddr*)&dst,
319 "sendto failed: %s\n", strerror(errno));
324 "Error: partial send of ICMP message\n");
330 * Send an ICMP message to the target.
332 * @param my_ip source address
333 * @param other target address
336 send_icmp (const struct in_addr *my_ip,
337 const struct in_addr *other)
339 struct ip_packet ip_pkt;
340 struct icmp_packet *icmp_pkt;
341 struct icmp_echo_packet icmp_echo;
342 struct sockaddr_in dst;
343 char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet) + sizeof(struct icmp_echo_packet)];
348 memset(packet, 0, sizeof(packet));
349 /* ip header: send to (known) ip address */
351 memset(&ip_pkt, 0, sizeof(ip_pkt));
352 ip_pkt.vers_ihl = 0x45;
354 ip_pkt.pkt_len = sizeof (packet); /* huh? */
356 ip_pkt.flags_frag_offset = 0;
357 ip_pkt.ttl = IPDEFTTL;
358 ip_pkt.proto = IPPROTO_ICMP;
360 ip_pkt.src_ip = my_ip->s_addr;
361 ip_pkt.dst_ip = other->s_addr;
362 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
364 memcpy (packet, &ip_pkt, sizeof (struct ip_packet));
365 off += sizeof (ip_pkt);
366 memset (&dst, 0, sizeof (dst));
367 dst.sin_family = AF_INET;
368 dst.sin_addr = *other;
370 /* icmp reply: time exceeded */
371 icmp_pkt = (struct icmp_packet*) &packet[off];
372 memset(icmp_pkt, 0, sizeof(struct icmp_packet));
373 icmp_pkt->type = ICMP_TIME_EXCEEDED;
375 icmp_pkt->reserved = 0;
376 icmp_pkt->checksum = 0;
378 off += sizeof (struct icmp_packet);
380 /* ip header of the presumably 'lost' udp packet */
381 ip_pkt.vers_ihl = 0x45;
383 ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
385 ip_pkt.flags_frag_offset = 0;
386 ip_pkt.ttl = 1; /* real TTL would be 1 on a time exceeded packet */
387 ip_pkt.proto = IPPROTO_ICMP;
388 ip_pkt.src_ip = other->s_addr;
389 ip_pkt.dst_ip = dummy.s_addr;
391 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
392 memcpy (&packet[off], &ip_pkt, sizeof (struct ip_packet));
393 off += sizeof (struct ip_packet);
395 icmp_echo.type = ICMP_ECHO;
397 icmp_echo.reserved = 0;
398 icmp_echo.checksum = 0;
399 icmp_echo.data = htons(port);
400 icmp_echo.checksum = htons(calc_checksum((uint16_t*) &icmp_echo,
401 sizeof (struct icmp_echo_packet)));
403 memcpy (&packet[off], &icmp_echo, sizeof(struct icmp_echo_packet));
404 off += sizeof (struct icmp_echo_packet);
406 icmp_pkt->checksum = htons(calc_checksum((uint16_t*)icmp_pkt,
407 sizeof (struct icmp_packet) + sizeof(struct ip_packet) + sizeof(struct icmp_echo_packet)));
409 err = sendto(rawsock,
412 (struct sockaddr*)&dst,
413 sizeof(dst)); /* or sizeof 'struct sockaddr'? */
418 "sendto failed: %s\n", strerror(errno));
423 "Error: partial send of ICMP message\n");
429 * Create an ICMP raw socket.
431 * @return INVALID_SOCKET on error
436 DWORD bOptVal = TRUE;
437 int bOptLen = sizeof(bOptVal);
440 ret = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
441 if (INVALID_SOCKET == ret)
444 "Error opening RAW socket: %s\n",
446 return INVALID_SOCKET;
448 if (setsockopt(ret, SOL_SOCKET, SO_BROADCAST, (char*)&bOptVal, bOptLen) != 0)
451 "Error setting SO_BROADCAST to ON: %s\n",
453 closesocket(rawsock);
454 return INVALID_SOCKET;
457 if (setsockopt(ret, IPPROTO_IP, IP_HDRINCL, (char*)&bOptVal, bOptLen) != 0)
460 "Error setting IP_HDRINCL to ON: %s\n",
462 closesocket(rawsock);
463 return INVALID_SOCKET;
470 main (int argc, char *const *argv)
472 struct in_addr external;
473 struct in_addr target;
481 "This program must be started with our IP, the targets external IP, and our port as arguments.\n");
484 if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
485 (1 != inet_pton (AF_INET, argv[2], &target)) )
488 "Error parsing IPv4 address: %s\n",
492 if ( (1 != sscanf (argv[3], "%u", &p) ) ||
497 "Error parsing port value `%s'\n",
503 if (WSAStartup (MAKEWORD (2, 1), &wsaData) != 0)
505 fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
508 if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
511 "Internal error converting dummy IP to binary.\n");
514 if (-1 == (rawsock = make_raw_socket()))
516 send_icmp (&external,
518 send_icmp_udp (&external,
520 closesocket (rawsock);
525 /* end of gnunet-nat-client-windows.c */