1 files changed, 598 insertions, 0 deletions
diff --git a/src/nat/gnunet-helper-nat-server-windows.c b/src/nat/gnunet-helper-nat-server-windows.c
new file mode 100644
index 0000000..d970ffd
--- /dev/null
+++ b/src/nat/gnunet-helper-nat-server-windows.c
@@ -0,0 +1,598 @@
+/*
+     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/nat/gnunet-helper-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
+ * - Christian Grothoff
+ */
+#define _GNU_SOURCE
+
+#define FD_SETSIZE 1024
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#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>
+
+/**
+ * Should we print some debug output?
+ */
+#define VERBOSE 0
+
+/**
+ * Must match IP given in the client.
+ */
+#define DUMMY_IP "192.0.2.86"
+
+/**
+ * Default Port
+ */
+#define NAT_TRAV_PORT 22225
+
+/**
+ * Must match packet ID used by gnunet-helper-nat-client.c
+ */
+#define PACKET_ID 256
+
+/**
+ * TTL to use for our outgoing messages.
+ */
+#define IPDEFTTL 64
+
+#define ICMP_ECHO 8
+
+#define ICMP_TIME_EXCEEDED 11
+
+/**
+ * How often do we send our ICMP messages to receive replies?
+ */
+#define ICMP_SEND_FREQUENCY_MS 500
+
+/**
+ * IPv4 header.
+ */
+struct ip_header
+{
+
+  /**
+   * Version (4 bits) + Internet header length (4 bits)
+   */
+  uint8_t vers_ihl;
+
+  /**
+   * Type of service
+   */
+  uint8_t tos;
+
+  /**
+   * Total length
+   */
+  uint16_t pkt_len;
+
+  /**
+   * Identification
+   */
+  uint16_t id;
+
+  /**
+   * Flags (3 bits) + Fragment offset (13 bits)
+   */
+  uint16_t flags_frag_offset;
+
+  /**
+   * Time to live
+   */
+  uint8_t ttl;
+
+  /**
+   * Protocol
+   */
+  uint8_t proto;
+
+  /**
+   * Header checksum
+   */
+  uint16_t checksum;
+
+  /**
+   * Source address
+   */
+  uint32_t src_ip;
+
+  /**
+   * Destination address
+   */
+  uint32_t dst_ip;
+};
+
+/**
+ * Format of ICMP packet.
+ */
+struct icmp_ttl_exceeded_header
+{
+  uint8_t type;
+
+  uint8_t code;
+
+  uint16_t checksum;
+
+  uint32_t unused;
+
+  /* followed by original payload */
+};
+
+struct icmp_echo_header
+{
+  uint8_t type;
+
+  uint8_t code;
+
+  uint16_t checksum;
+
+  uint32_t reserved;
+};
+
+/**
+ * Beginning of UDP packet.
+ */
+struct udp_header
+{
+  uint16_t src_port;
+
+  uint16_t dst_port;
+
+  uint16_t length;
+
+  uint16_t crc;
+};
+
+/**
+ * Socket we use to receive "fake" ICMP replies.
+ */
+static SOCKET icmpsock;
+
+/**
+ * Socket we use to send our ICMP requests.
+ */
+static SOCKET rawsock;
+
+/**
+ * Socket we use to send our UDP requests.
+ */
+static SOCKET udpsock;
+
+/**
+ * Target "dummy" address.
+ */
+static struct in_addr dummy;
+
+
+/**
+ * CRC-16 for IP/ICMP headers.
+ *
+ * @param data what to calculate the CRC over
+ * @param bytes number of bytes in data (must be multiple of 2)
+ * @return the CRC 16.
+ */
+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;
+}
+
+
+/**
+ * Convert IPv4 address from text to binary form.
+ *
+ * @param af address family
+ * @param cp the address to print
+ * @param buf where to write the address result
+ * @return 1 on success
+ */
+static int
+inet_pton (int af, const char *cp, struct in_addr *buf)
+{
+  buf->s_addr = inet_addr (cp);
+  if (buf->s_addr == INADDR_NONE)
+  {
+    fprintf (stderr, "Error %d handling address %s", WSAGetLastError (), cp);
+    return 0;
+  }
+  return 1;
+}
+
+
+/**
+ * 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)
+{
+  char packet[sizeof (struct ip_header) + sizeof (struct icmp_echo_header)];
+  struct icmp_echo_header icmp_echo;
+  struct ip_header ip_pkt;
+  struct sockaddr_in dst;
+  size_t off;
+  int err;
+
+  off = 0;
+  ip_pkt.vers_ihl = 0x45;
+  ip_pkt.tos = 0;
+  ip_pkt.pkt_len = htons (sizeof (packet));
+  ip_pkt.id = htons (PACKET_ID);
+  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 (struct ip_header)));
+  memcpy (&packet[off], &ip_pkt, sizeof (struct ip_header));
+  off += sizeof (struct ip_header);
+
+  icmp_echo.type = ICMP_ECHO;
+  icmp_echo.code = 0;
+  icmp_echo.reserved = 0;
+  icmp_echo.checksum = 0;
+  icmp_echo.checksum =
+      htons (calc_checksum
+             ((uint16_t *) & icmp_echo, sizeof (struct icmp_echo_header)));
+  memcpy (&packet[off], &icmp_echo, sizeof (struct icmp_echo_header));
+  off += sizeof (struct icmp_echo_header);
+
+  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");
+  }
+}
+
+
+/**
+ * Send a UDP message to the dummy IP.
+ */
+static void
+send_udp ()
+{
+  struct sockaddr_in dst;
+  ssize_t err;
+
+  memset (&dst, 0, sizeof (dst));
+  dst.sin_family = AF_INET;
+  dst.sin_addr = dummy;
+  dst.sin_port = htons (NAT_TRAV_PORT);
+  err = sendto (udpsock, NULL, 0, 0, (struct sockaddr *) &dst, sizeof (dst));
+  if (err < 0)
+  {
+#if VERBOSE
+    fprintf (stderr, "sendto failed: %s\n", strerror (errno));
+#endif
+  }
+  else if (0 != err)
+  {
+    fprintf (stderr, "Error: partial send of ICMP message\n");
+  }
+}
+
+
+/**
+ * We've received an ICMP response.  Process it.
+ */
+static void
+process_icmp_response ()
+{
+  char buf[65536];
+  ssize_t have;
+  struct in_addr source_ip;
+  struct ip_header ip_pkt;
+  struct icmp_ttl_exceeded_header icmp_ttl;
+  struct icmp_echo_header icmp_echo;
+  struct udp_header udp_pkt;
+  size_t off;
+  uint16_t port;
+  DWORD ssize;
+
+  have = read (icmpsock, buf, sizeof (buf));
+  if (have == -1)
+  {
+    fprintf (stderr, "Error reading raw socket: %s\n", strerror (errno));
+    return;
+  }
+#if VERBOSE
+  fprintf (stderr, "Received message of %u bytes\n", (unsigned int) have);
+#endif
+  if (have <
+      (ssize_t) (sizeof (struct ip_header) +
+                 sizeof (struct icmp_ttl_exceeded_header) +
+                 sizeof (struct ip_header)))
+  {
+    /* malformed */
+    return;
+  }
+  off = 0;
+  memcpy (&ip_pkt, &buf[off], sizeof (struct ip_header));
+  off += sizeof (struct ip_header);
+  memcpy (&source_ip, &ip_pkt.src_ip, sizeof (source_ip));
+  memcpy (&icmp_ttl, &buf[off], sizeof (struct icmp_ttl_exceeded_header));
+  off += sizeof (struct icmp_ttl_exceeded_header);
+  if ((ICMP_TIME_EXCEEDED != icmp_ttl.type) || (0 != icmp_ttl.code))
+  {
+    /* different type than what we want */
+    return;
+  }
+  /* skip 2nd IP header */
+  memcpy (&ip_pkt, &buf[off], sizeof (struct ip_header));
+  off += sizeof (struct ip_header);
+
+  switch (ip_pkt.proto)
+  {
+  case IPPROTO_ICMP:
+    if (have !=
+        (sizeof (struct ip_header) * 2 +
+         sizeof (struct icmp_ttl_exceeded_header) +
+         sizeof (struct icmp_echo_header)))
+    {
+      /* malformed */
+      return;
+    }
+    /* grab ICMP ECHO content */
+    memcpy (&icmp_echo, &buf[off], sizeof (struct icmp_echo_header));
+    port = (uint16_t) ntohl (icmp_echo.reserved);
+    break;
+  case IPPROTO_UDP:
+    if (have !=
+        (sizeof (struct ip_header) * 2 +
+         sizeof (struct icmp_ttl_exceeded_header) + sizeof (struct udp_header)))
+    {
+      /* malformed */
+      return;
+    }
+    /* grab UDP content */
+    memcpy (&udp_pkt, &buf[off], sizeof (struct udp_header));
+    port = ntohs (udp_pkt.length);
+    break;
+  default:
+    /* different type than what we want */
+    return;
+  }
+
+  ssize = sizeof (buf);
+  WSAAddressToString ((LPSOCKADDR) & source_ip, sizeof (source_ip), NULL, buf,
+                      &ssize);
+  if (port == 0)
+    fprintf (stdout, "%s\n", buf);
+  else
+    fprintf (stdout, "%s:%u\n", buf, (unsigned int) port);
+  fflush (stdout);
+}
+
+
+/**
+ * Create an ICMP raw socket for reading.
+ *
+ * @return INVALID_SOCKET on error
+ */
+static SOCKET
+make_icmp_socket ()
+{
+  SOCKET ret;
+
+  ret = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
+  if (INVALID_SOCKET == ret)
+  {
+    fprintf (stderr, "Error opening RAW socket: %s\n", strerror (errno));
+    return INVALID_SOCKET;
+  }
+  return ret;
+}
+
+
+/**
+ * Create an ICMP raw socket for writing.
+ *
+ * @return INVALID_SOCKET on error
+ */
+static SOCKET
+make_raw_socket ()
+{
+  DWORD bOptVal = TRUE;
+  int bOptLen = sizeof (bOptVal);
+
+  rawsock = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
+  if (INVALID_SOCKET == rawsock)
+  {
+    fprintf (stderr, "Error opening RAW socket: %s\n", strerror (errno));
+    return INVALID_SOCKET;
+  }
+
+  if (0 !=
+      setsockopt (rawsock, SOL_SOCKET, SO_BROADCAST, (char *) &bOptVal,
+                  bOptLen))
+  {
+    fprintf (stderr, "Error setting SO_BROADCAST to ON: %s\n",
+             strerror (errno));
+    closesocket (rawsock);
+    return INVALID_SOCKET;
+  }
+  if (0 !=
+      setsockopt (rawsock, IPPROTO_IP, IP_HDRINCL, (char *) &bOptVal, bOptLen))
+  {
+    fprintf (stderr, "Error setting IP_HDRINCL to ON: %s\n", strerror (errno));
+    closesocket (rawsock);
+    return INVALID_SOCKET;
+  }
+  return rawsock;
+}
+
+
+/**
+ * Create a UDP socket for writing.
+ *
+ * @param my_ip source address (our ip address)
+ * @return INVALID_SOCKET on error
+ */
+static SOCKET
+make_udp_socket (const struct in_addr *my_ip)
+{
+  SOCKET ret;
+  struct sockaddr_in addr;
+
+  ret = socket (AF_INET, SOCK_DGRAM, 0);
+  if (INVALID_SOCKET == ret)
+  {
+    fprintf (stderr, "Error opening UDP socket: %s\n", strerror (errno));
+    return INVALID_SOCKET;
+  }
+  memset (&addr, 0, sizeof (addr));
+  addr.sin_family = AF_INET;
+  addr.sin_addr = *my_ip;
+  addr.sin_port = htons (NAT_TRAV_PORT);
+  if (0 != bind (ret, (struct sockaddr *) &addr, sizeof (addr)))
+  {
+    fprintf (stderr, "Error binding UDP socket to port %u: %s\n", NAT_TRAV_PORT,
+             strerror (errno));
+    /* likely problematic, but not certain, try to continue */
+  }
+  return ret;
+}
+
+
+int
+main (int argc, char *const *argv)
+{
+  struct in_addr external;
+  fd_set rs;
+  struct timeval tv;
+  WSADATA wsaData;
+  unsigned int alt;
+
+  alt = 0;
+  if (2 != argc)
+  {
+    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, error %s\n", argv[1],
+             strerror (errno));
+    return 1;
+  }
+  if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
+  {
+    fprintf (stderr, "Internal error converting dummy IP to binary.\n");
+    return 2;
+  }
+  if (WSAStartup (MAKEWORD (2, 1), &wsaData) != 0)
+  {
+    fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
+    return 2;
+  }
+  if (INVALID_SOCKET == (icmpsock = make_icmp_socket ()))
+  {
+    return 3;
+  }
+  if (INVALID_SOCKET == (make_raw_socket ()))
+  {
+    closesocket (icmpsock);
+    return 3;
+  }
+  if (INVALID_SOCKET == (udpsock = make_udp_socket (&external)))
+  {
+    closesocket (icmpsock);
+    closesocket (rawsock);
+    return 3;
+  }
+  while (1)
+  {
+    FD_ZERO (&rs);
+    FD_SET (icmpsock, &rs);
+    tv.tv_sec = 0;
+    tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
+    if (-1 == select (icmpsock + 1, &rs, NULL, NULL, &tv))
+    {
+      if (errno == EINTR)
+        continue;
+      fprintf (stderr, "select failed: %s\n", strerror (errno));
+      break;
+    }
+    if (FD_ISSET (icmpsock, &rs))
+      process_icmp_response ();
+    if (0 == (++alt % 2))
+      send_icmp_echo (&external);
+    else
+      send_udp ();
+  }
+  /* select failed (internal error or OS out of resources) */
+  closesocket (icmpsock);
+  closesocket (rawsock);
+  closesocket (udpsock);
+  WSACleanup ();
+  return 4;
+}
+
+
+/* end of gnunet-helper-nat-server-windows.c */