2 This file is part of GNUnet.
3 (C) 2010 Christian Grothoff (and other contributing authors)
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13 General Public License for more details.
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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
48 #include <sys/types.h>
49 #include <sys/socket.h>
50 #include <arpa/inet.h>
51 #include <sys/select.h>
52 #include <netinet/ip.h>
53 #include <netinet/ip_icmp.h>
54 #include <netinet/in.h>
57 #include <sys/types.h>
68 typedef unsigned int uid_t;
69 typedef SOCKET Socket;
70 typedef unsigned short ushort;
72 #define IPDEFTTL 64 /* default ttl, from RFC 1340 */
73 #define ICMP_TIME_EXCEEDED 11 /* Time Exceeded */
74 #define IP_HDRINCL 3 /* int; Header is included with data. */
80 * Must match IP given in the server.
82 #define DUMMY_IP "192.0.2.86"
84 #define NAT_TRAV_PORT 22225
92 uint16_t flags_frag_offset;
109 struct icmp_echo_packet
127 static Socket rawsock;
129 static struct in_addr dummy;
131 static uint32_t port;
135 * @param af address family
136 * @param cp the address to print
137 * @param buf where to write the address result
139 static int inet_pton (int af, char *cp, struct in_addr *buf)
141 //ret = WSAStringToAddress (cp, af, NULL, (LPSOCKADDR)buf, &ssize);
142 buf->s_addr = inet_addr(cp);
143 if (buf->s_addr == INADDR_NONE)
145 fprintf(stderr, "Error %d handling address %s", WSAGetLastError(), cp);
154 calc_checksum(const uint16_t *data,
161 for (i=0;i<bytes/2;i++)
163 sum = (sum & 0xffff) + (sum >> 16);
164 sum = htons(0xffff - sum);
170 make_echo (const struct in_addr *src_ip,
171 struct icmp_echo_packet *echo, uint32_t num)
173 memset(echo, 0, sizeof(struct icmp_echo_packet));
174 echo->type = ICMP_ECHO;
178 echo->data = htons(num);
179 echo->checksum = htons(calc_checksum((uint16_t*)echo,
180 sizeof (struct icmp_echo_packet)));
185 * Send an ICMP message to the target.
187 * @param my_ip source address
188 * @param other target address
191 send_icmp_udp (const struct in_addr *my_ip,
192 const struct in_addr *other)
194 struct ip_packet ip_pkt;
195 struct icmp_packet icmp_pkt;
196 struct udp_packet udp_pkt;
198 struct sockaddr_in dst;
199 char packet[sizeof(ip_pkt) * 2 + sizeof(icmp_pkt) * 2 + sizeof(uint32_t)];
204 /* ip header: send to (known) ip address */
206 memset(&ip_pkt, 0, sizeof(ip_pkt));
207 ip_pkt.vers_ihl = 0x45;
209 ip_pkt.pkt_len = htons(sizeof (packet));
210 ip_pkt.id = htons(256);
211 ip_pkt.flags_frag_offset = 0;
213 ip_pkt.proto = IPPROTO_ICMP;
215 ip_pkt.src_ip = my_ip->s_addr;
216 ip_pkt.dst_ip = other->s_addr;
217 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
218 memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
219 off += sizeof(ip_pkt);
221 /* ip header of the presumably 'lost' udp packet */
222 ip_pkt.vers_ihl = 0x45;
224 ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
226 icmp_pkt.type = 11; /* TTL exceeded */
228 icmp_pkt.checksum = 0;
229 icmp_pkt.reserved = 0;
230 memcpy(&packet[off], &icmp_pkt, sizeof(icmp_pkt));
231 off += sizeof(icmp_pkt);
233 /* build inner IP header */
234 memset(&ip_pkt, 0, sizeof(ip_pkt));
235 ip_pkt.vers_ihl = 0x45;
237 ip_pkt.pkt_len = htons(sizeof (ip_pkt) + sizeof(udp_pkt));
238 ip_pkt.id = htons(0);
239 ip_pkt.flags_frag_offset = 0;
241 ip_pkt.proto = IPPROTO_UDP;
243 ip_pkt.src_ip = other->s_addr;
244 ip_pkt.dst_ip = dummy.s_addr;
245 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
246 memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
247 off += sizeof(ip_pkt);
249 /* build UDP header */
250 udp_pkt.src_port = htons(NAT_TRAV_PORT); /* FIXME: does this port matter? */
251 udp_pkt.dst_port = htons(NAT_TRAV_PORT);
253 memset(&udp_pkt.length, 0, sizeof(uint32_t));
254 udp_pkt.length = htonl(port);
255 memcpy(&packet[off], &udp_pkt, sizeof(udp_pkt));
256 off += sizeof(udp_pkt);
258 /* set ICMP checksum */
259 icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[sizeof(ip_pkt)],
260 sizeof (icmp_pkt) + sizeof(ip_pkt) + sizeof(udp_pkt)));
261 memcpy (&packet[sizeof(ip_pkt)], &icmp_pkt, sizeof (icmp_pkt));
264 memset (&dst, 0, sizeof (dst));
265 dst.sin_family = AF_INET;
266 dst.sin_addr = *other;
267 err = sendto(rawsock,
270 (struct sockaddr*)&dst,
276 "sendto failed: %s\n", strerror(errno));
281 "Error: partial send of ICMP message\n");
287 * Send an ICMP message to the target.
289 * @param my_ip source address
290 * @param other target address
293 send_icmp (const struct in_addr *my_ip,
294 const struct in_addr *other)
296 struct ip_packet ip_pkt;
297 struct icmp_packet *icmp_pkt;
298 struct icmp_echo_packet icmp_echo;
299 struct sockaddr_in dst;
300 char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet) + sizeof(struct icmp_echo_packet)];
305 /* ip header: send to (known) ip address */
307 memset(&ip_pkt, 0, sizeof(ip_pkt));
308 ip_pkt.vers_ihl = 0x45;
310 ip_pkt.pkt_len = sizeof (packet); /* huh? */
312 ip_pkt.flags_frag_offset = 0;
313 ip_pkt.ttl = IPDEFTTL;
314 ip_pkt.proto = IPPROTO_ICMP;
316 ip_pkt.src_ip = my_ip->s_addr;
317 ip_pkt.dst_ip = other->s_addr;
318 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
319 memcpy (packet, &ip_pkt, sizeof (struct ip_packet));
320 off += sizeof (ip_pkt);
321 /* icmp reply: time exceeded */
322 icmp_pkt = (struct icmp_packet*) &packet[off];
323 memset(icmp_pkt, 0, sizeof(struct icmp_packet));
324 icmp_pkt->type = ICMP_TIME_EXCEEDED;
326 icmp_pkt->reserved = 0;
327 icmp_pkt->checksum = 0;
329 off += sizeof (struct icmp_packet);
331 /* ip header of the presumably 'lost' udp packet */
332 ip_pkt.vers_ihl = 0x45;
334 ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
337 ip_pkt.flags_frag_offset = 0;
338 ip_pkt.ttl = 1; /* real TTL would be 1 on a time exceeded packet */
339 ip_pkt.proto = IPPROTO_ICMP;
340 ip_pkt.src_ip = other->s_addr;
341 ip_pkt.dst_ip = dummy.s_addr;
343 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
344 memcpy (&packet[off], &ip_pkt, sizeof (struct ip_packet));
345 off += sizeof (struct ip_packet);
347 make_echo (other, &icmp_echo, port);
348 memcpy (&packet[off], &icmp_echo, sizeof(struct icmp_echo_packet));
349 off += sizeof (struct icmp_echo_packet);
351 icmp_pkt->checksum = htons(calc_checksum((uint16_t*)icmp_pkt,
352 sizeof (struct icmp_packet) + sizeof(struct ip_packet) + sizeof(struct icmp_echo_packet)));
354 memset (&dst, 0, sizeof (dst));
355 dst.sin_family = AF_INET;
356 dst.sin_addr = *other;
357 err = sendto(rawsock,
360 (struct sockaddr*)&dst,
361 sizeof(dst)); /* or sizeof 'struct sockaddr'? */
365 "sendto failed: %s\n", strerror(errno));
370 "Error: partial send of ICMP message\n");
381 ret = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
385 "Error opening RAW socket: %s\n",
389 if (setsockopt(ret, SOL_SOCKET, SO_BROADCAST,
390 (char *)&one, sizeof(one)) == -1)
392 "setsockopt failed: %s\n",
394 if (setsockopt(ret, IPPROTO_IP, IP_HDRINCL,
395 (char *)&one, sizeof(one)) == -1)
397 "setsockopt failed: %s\n",
404 main (int argc, char *const *argv)
406 struct in_addr external;
407 struct in_addr target;
415 if (WSAStartup (MAKEWORD (2, 1), &wsaData) != 0)
417 fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
422 if (-1 == (rawsock = make_raw_socket()))
427 if (0 != setresuid (uid, uid, uid))
429 "Failed to setresuid: %s\n",
435 "This program must be started with our IP, the targets external IP, and our port as arguments.\n");
438 port = atoi(argv[3]);
440 if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
441 (1 != inet_pton (AF_INET, argv[2], &target)) )
444 "Error parsing IPv4 address: %s\n",
448 if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
449 send_icmp (&external,
451 send_icmp_udp (&external,
457 /* end of gnunet-nat-client.c */