--- /dev/null
+/*
+ This file is part of GNUnet.
+ (C) 2010 Christian Grothoff (and other contributing authors)
+
+ GNUnet is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published
+ by the Free Software Foundation; either version 3, or (at your
+ option) any later version.
+
+ GNUnet is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with GNUnet; see the file COPYING. If not, write to the
+ Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file src/transport/gnunet-nat-server-windows.c
+ * @brief Windows tool to help bypass NATs using ICMP method
+ * This code will work under W32 only
+ * @author Christian Grothoff
+ *
+ * This program will send ONE ICMP message every 500 ms RAW sockets
+ * to a DUMMY IP address and also listens for ICMP replies. Since
+ * it uses RAW sockets, it must be run as an administrative user.
+ * In order to keep the security risk of the resulting binary
+ * minimal, the program ONLY opens the two RAW sockets with administrative
+ * privileges, then drops them and only then starts to process
+ * command line arguments. The code also does not link against
+ * any shared libraries (except libc) and is strictly minimal
+ * (except for checking for errors). The following list of people
+ * have reviewed this code and considered it safe since the last
+ * modification (if you reviewed it, please have your name added
+ * to the list):
+ *
+ * - Nathan Evans
+ */
+#define _GNU_SOURCE
+#ifdef WIN32
+#include <winsock2.h>
+#else
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <sys/select.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <netinet/in.h>
+#endif
+#include <sys/time.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <time.h>
+
+#ifdef WIN32
+typedef SOCKET Socket;
+typedef unsigned short ushort;
+#else
+typedef int Socket;
+#endif
+
+/**
+ * Must match IP given in the client.
+ */
+#define DUMMY_IP "192.0.2.86"
+
+#define VERBOSE 0
+
+/**
+ * How often do we send our ICMP messages to receive replies?
+ */
+#define ICMP_SEND_FREQUENCY_MS 500
+
+struct ip_packet
+{
+ uint8_t vers_ihl;
+ uint8_t tos;
+ uint16_t pkt_len;
+ uint16_t id;
+ uint16_t flags_frag_offset;
+ uint8_t ttl;
+ uint8_t proto;
+ uint16_t checksum;
+ uint32_t src_ip;
+ uint32_t dst_ip;
+};
+
+struct icmp_packet
+{
+ uint8_t type;
+ uint8_t code;
+ uint16_t checksum;
+ uint32_t reserved;
+};
+
+struct udp_packet
+{
+ uint16_t src_port;
+
+ uint16_t dst_port;
+
+ uint32_t length;
+};
+
+static Socket icmpsock;
+
+static Socket rawsock;
+
+static struct in_addr dummy;
+
+static uint16_t
+calc_checksum(const uint16_t *data,
+ unsigned int bytes)
+{
+ uint32_t sum;
+ unsigned int i;
+
+ sum = 0;
+ for (i=0;i<bytes/2;i++)
+ sum += data[i];
+ sum = (sum & 0xffff) + (sum >> 16);
+ sum = htons(0xffff - sum);
+ return sum;
+}
+
+
+static void
+make_echo (const struct in_addr *src_ip,
+ struct icmp_packet *echo)
+{
+ memset(echo, 0, sizeof(struct icmp_packet));
+ echo->type = ICMP_ECHO;
+ echo->code = 0;
+ echo->reserved = 0;
+ echo->checksum = 0;
+ echo->checksum = htons(calc_checksum((uint16_t*)echo, sizeof (struct icmp_packet)));
+}
+
+
+/**
+ * Send an ICMP message to the dummy IP.
+ *
+ * @param my_ip source address (our ip address)
+ */
+static void
+send_icmp_echo (const struct in_addr *my_ip)
+{
+ struct icmp_packet icmp_echo;
+ struct sockaddr_in dst;
+ size_t off;
+ int err;
+ struct ip_packet ip_pkt;
+ struct icmp_packet icmp_pkt;
+ char packet[sizeof (ip_pkt) + sizeof (icmp_pkt)];
+
+ off = 0;
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = sizeof (packet);
+ ip_pkt.id = 1;
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = IPDEFTTL;
+ ip_pkt.proto = IPPROTO_ICMP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = my_ip->s_addr;
+ ip_pkt.dst_ip = dummy.s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
+ memcpy (packet, &ip_pkt, sizeof (ip_pkt));
+ off += sizeof (ip_pkt);
+ make_echo (my_ip, &icmp_echo);
+ memcpy (&packet[off], &icmp_echo, sizeof (icmp_echo));
+ off += sizeof (icmp_echo);
+
+ memset (&dst, 0, sizeof (dst));
+ dst.sin_family = AF_INET;
+ dst.sin_addr = dummy;
+ err = sendto(rawsock,
+ packet, off, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst));
+ if (err < 0)
+ {
+#if VERBOSE
+ fprintf(stderr,
+ "sendto failed: %s\n", strerror(errno));
+#endif
+ }
+ else if (err != off)
+ {
+ fprintf(stderr,
+ "Error: partial send of ICMP message\n");
+ }
+}
+
+
+static void
+process_icmp_response ()
+{
+ char buf[65536];
+ ssize_t have;
+ struct in_addr sip;
+ struct ip_packet ip_pkt;
+ struct icmp_packet icmp_pkt;
+ struct udp_packet udp_pkt;
+ size_t off;
+ int have_port;
+ int have_udp;
+ uint32_t port;
+
+ have = read (icmpsock, buf, sizeof (buf));
+ if (have == -1)
+ {
+ fprintf (stderr,
+ "Error reading raw socket: %s\n",
+ strerror (errno));
+ return;
+ }
+ have_port = 0;
+
+ if (have == sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2 + sizeof(uint32_t))
+ {
+ have_port = 1;
+ }
+ else if (have != sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2)
+ {
+#if VERBOSE
+ fprintf (stderr,
+ "Received ICMP message of unexpected size: %u bytes\n",
+ (unsigned int) have);
+#endif
+ return;
+ }
+ off = 0;
+ memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
+ off += sizeof (ip_pkt);
+ memcpy (&icmp_pkt, &buf[off], sizeof (icmp_pkt));
+ off += sizeof (icmp_pkt);
+ if ( ((ip_pkt.proto != IPPROTO_ICMP) && (ip_pkt.proto != IPPROTO_UDP)) ||
+ (icmp_pkt.type != ICMP_TIME_EXCEEDED) ||
+ (icmp_pkt.code != 0) )
+ {
+ /* maybe we got an actual reply back... */
+ return;
+ }
+ memcpy(&sip,
+ &ip_pkt.src_ip,
+ sizeof (sip));
+
+ memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
+ off += sizeof (ip_pkt);
+
+ have_udp = 0;
+ if (ip_pkt.proto == IPPROTO_UDP)
+ {
+ have_udp = 1;
+ }
+
+ if (have_port)
+ {
+ memcpy(&port, &buf[sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2], sizeof(uint32_t));
+ port = ntohs(port);
+ fprintf (stdout,
+ "%s:%d\n",
+ inet_ntop (AF_INET,
+ &sip,
+ buf,
+ sizeof (buf)), port);
+ }
+ else if (have_udp)
+ {
+ memcpy(&udp_pkt, &buf[off], sizeof(udp_pkt));
+ fprintf (stdout,
+ "%s:%d\n",
+ inet_ntop (AF_INET,
+ &sip,
+ buf,
+ sizeof (buf)), ntohl(udp_pkt.length));
+ }
+ else
+ {
+ fprintf (stdout,
+ "%s\n",
+ inet_ntop (AF_INET,
+ &sip,
+ buf,
+ sizeof (buf)));
+ }
+ fflush (stdout);
+}
+
+
+static Socket
+make_icmp_socket ()
+{
+ Socket ret;
+
+ ret = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
+ if (-1 == ret)
+ {
+ fprintf (stderr,
+ "Error opening RAW socket: %s\n",
+ strerror (errno));
+ return -1;
+ }
+ if (ret >= FD_SETSIZE)
+ {
+ fprintf (stderr,
+ "Socket number too large (%d > %u)\n",
+ ret,
+ (unsigned int) FD_SETSIZE);
+#ifdef WIN32
+ closesocket (ret);
+#else
+ close (ret);
+#endif
+ return -1;
+ }
+ return ret;
+}
+
+
+static Socket
+make_raw_socket ()
+{
+ const int one = 1;
+ Socket ret;
+
+ ret = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
+ if (-1 == ret)
+ {
+ fprintf (stderr,
+ "Error opening RAW socket: %s\n",
+ strerror (errno));
+ return -1;
+ }
+ if (setsockopt(ret, SOL_SOCKET, SO_BROADCAST,
+ (char *)&one, sizeof(one)) == -1)
+ fprintf(stderr,
+ "setsockopt failed: %s\n",
+ strerror (errno));
+ if (setsockopt(ret, IPPROTO_IP, IP_HDRINCL,
+ (char *)&one, sizeof(one)) == -1)
+ fprintf(stderr,
+ "setsockopt failed: %s\n",
+ strerror (errno));
+ return ret;
+}
+
+
+int
+main (int argc, char *const *argv)
+{
+ struct in_addr external;
+ fd_set rs;
+ struct timeval tv;
+ uid_t uid;
+
+#ifdef WIN32
+ // WSA startup
+ WSAData wsaData;
+ if (WSAStartup (MAKEWORD (2, 1), &wsaData) != 0)
+ {
+ fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
+ return 4; // ERROR
+ }
+#endif
+
+ if (-1 == (icmpsock = make_icmp_socket()))
+ return 1;
+ if (-1 == (rawsock = make_raw_socket()))
+ {
+ close (icmpsock);
+ return 1;
+ }
+ uid = getuid ();
+ if (0 != setresuid (uid, uid, uid))
+ fprintf (stderr,
+ "Failed to setresuid: %s\n",
+ strerror (errno));
+ if (argc != 2)
+ {
+ fprintf (stderr,
+ "This program must be started with our (internal NAT) IP as the only argument.\n");
+ return 1;
+ }
+ if (1 != inet_pton (AF_INET, argv[1], &external))
+ {
+ fprintf (stderr,
+ "Error parsing IPv4 address: %s\n",
+ strerror (errno));
+ return 1;
+ }
+ if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
+ while (1)
+ {
+ FD_ZERO (&rs);
+ FD_SET (icmpsock, &rs);
+ tv.tv_sec = 0;
+ tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
+ select (icmpsock + 1, &rs, NULL, NULL, &tv);
+ if (FD_ISSET (icmpsock, &rs))
+ process_icmp_response ();
+ send_icmp_echo (&external);
+ }
+
+#ifdef WIN32
+ closesocket(icmpsock);
+ closesocket(rawsock);
+ WSACleanup ();
+#endif
+ return 0;
+}
+
+
+/* end of gnunet-nat-server-windows.c */
projects / oweals / gnunet.git / commitdiff