1 files changed, 550 insertions, 0 deletions

diff --git a/src/nat/gnunet-helper-nat-client-windows.c b/src/nat/gnunet-helper-nat-client-windows.c
new file mode 100644
index 000000000..0717eecfe
--- /dev/null
+++ b/src/nat/gnunet-helper-nat-client-windows.c
@@ -0,0 +1,550 @@
+/*
+     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-client-windows.c
+ * @brief Tool to help bypass NATs using ICMP method; must run as
+ *        administrator on W32
+ *        This code is forx W32.
+ * @author Nathan Evans
+ *
+ * This program will send ONE ICMP message using RAW sockets
+ * to the IP address specified as the second argument.  Since
+ * it uses RAW sockets, it must be installed SUID or run as 'root'.
+ * In order to keep the security risk of the resulting SUID binary
+ * minimal, the program ONLY opens the RAW socket with root
+ * 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):
+ *
+ * - Christian Grothoff
+ * - Nathan Evans
+ */
+#define _GNU_SOURCE
+
+#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>
+
+
+#define ICMP_ECHO 8
+#define IPDEFTTL 64
+#define ICMP_TIME_EXCEEDED 11
+
+/**
+ * Must match IP given in the server.
+ */
+#define DUMMY_IP "192.0.2.86"
+
+#define NAT_TRAV_PORT 22225
+
+/**
+ * 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 send our ICMP packets.
+ */
+static SOCKET rawsock;
+
+/**
+ * Target "dummy" address.
+ */
+static struct in_addr dummy;
+
+/**
+ * Port we are listening on (communicated to the server).
+ */
+static uint16_t port;
+
+
+
+/**
+ * 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;
+}
+
+
+/**
+ * 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;
+}
+
+
+/**
+ * Send an ICMP message to the target.
+ *
+ * @param my_ip source address
+ * @param other target address
+ */
+static void
+send_icmp_udp (const struct in_addr *my_ip,
+               const struct in_addr *other)
+{
+  char packet[sizeof(struct ip_header) * 2 +
+              sizeof(struct icmp_ttl_exceeded_header) +
+              sizeof(struct udp_header)];
+  struct ip_header ip_pkt;
+  struct icmp_ttl_exceeded_header icmp_pkt;
+  struct udp_header udp_pkt;
+  struct sockaddr_in dst;
+  size_t off;
+  int err;
+
+  /* ip header: send to (known) ip address */
+  off = 0;
+  ip_pkt.vers_ihl = 0x45;
+  ip_pkt.tos = 0;
+  ip_pkt.pkt_len = htons(sizeof (packet));
+  ip_pkt.id = htons(256);
+  ip_pkt.flags_frag_offset = 0;
+  ip_pkt.ttl = 128;
+  ip_pkt.proto = IPPROTO_ICMP;
+  ip_pkt.checksum = 0;
+  ip_pkt.src_ip = my_ip->s_addr;
+  ip_pkt.dst_ip = other->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_pkt.type = ICMP_TIME_EXCEEDED;
+  icmp_pkt.code = 0;
+  icmp_pkt.checksum = 0;
+  icmp_pkt.unused = 0;
+  memcpy(&packet[off],
+         &icmp_pkt,
+         sizeof(struct icmp_ttl_exceeded_header));
+  off += sizeof(struct icmp_ttl_exceeded_header);
+
+  /* ip header of the presumably 'lost' udp packet */
+  ip_pkt.vers_ihl = 0x45;
+  ip_pkt.tos = 0;
+  ip_pkt.pkt_len = htons(sizeof (struct ip_header) +
+                         sizeof (struct udp_header));
+  ip_pkt.id = htons(0);
+  ip_pkt.flags_frag_offset = 0;
+  ip_pkt.ttl = 128;
+  ip_pkt.proto = IPPROTO_UDP;
+  ip_pkt.checksum = 0;
+  ip_pkt.src_ip = other->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);
+
+  /* build UDP header */
+  udp_pkt.src_port = htons(NAT_TRAV_PORT);
+  udp_pkt.dst_port = htons(NAT_TRAV_PORT);
+  udp_pkt.length = htons (port);
+  udp_pkt.crc = 0;
+  memcpy(&packet[off],
+         &udp_pkt,
+         sizeof(struct udp_header));
+  off += sizeof(struct udp_header);
+
+  /* no go back to calculate ICMP packet checksum */
+  icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[off],
+                                          sizeof (struct icmp_ttl_exceeded_header) +
+                                          sizeof (struct ip_header) +
+                                          sizeof (struct udp_header)));
+  memcpy (&packet[sizeof (struct ip_header)],
+          &icmp_pkt,
+          sizeof (struct icmp_ttl_exceeded_header));
+
+  memset (&dst, 0, sizeof (dst));
+  dst.sin_family = AF_INET;
+  dst.sin_addr = *other;
+  err = sendto(rawsock,
+               packet,
+               sizeof (packet), 0,
+               (struct sockaddr*)&dst,
+               sizeof(dst));
+  if (err < 0)
+    {
+      fprintf(stderr,
+              "sendto failed: %s\n", strerror(errno));
+    }
+  else if (sizeof (packet) != (size_t) err)
+    {
+      fprintf(stderr,
+              "Error: partial send of ICMP message\n");
+    }
+}
+
+
+/**
+ * Send an ICMP message to the target.
+ *
+ * @param my_ip source address
+ * @param other target address
+ */
+static void
+send_icmp (const struct in_addr *my_ip,
+           const struct in_addr *other)
+{
+  struct ip_header ip_pkt;
+  struct icmp_ttl_exceeded_header icmp_ttl;
+  struct icmp_echo_header icmp_echo;
+  struct sockaddr_in dst;
+  char packet[sizeof (struct ip_header) * 2 +
+              sizeof (struct icmp_ttl_exceeded_header) +
+              sizeof(struct icmp_echo_header)];
+  size_t off;
+  int err;
+
+  /* ip header: send to (known) ip address */
+  off = 0;
+  ip_pkt.vers_ihl = 0x45;
+  ip_pkt.tos = 0;
+  ip_pkt.pkt_len = htons (sizeof (packet));
+  ip_pkt.id = htons(256);
+  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 = other->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 (ip_pkt);
+
+  /* icmp reply: time exceeded */
+  icmp_ttl.type = ICMP_TIME_EXCEEDED;
+  icmp_ttl.code = 0;
+  icmp_ttl.checksum = 0;
+  icmp_ttl.unused = 0; 
+  memcpy (&packet[off],
+          &icmp_ttl,
+          sizeof (struct icmp_ttl_exceeded_header));
+  off += sizeof (struct icmp_ttl_exceeded_header);
+
+  /* ip header of the presumably 'lost' udp packet */
+  ip_pkt.vers_ihl = 0x45;
+  ip_pkt.tos = 0;
+  ip_pkt.pkt_len = htons(sizeof (struct ip_header) + sizeof (struct icmp_echo_header));
+  ip_pkt.id = htons (256);
+  ip_pkt.flags_frag_offset = 0;
+  ip_pkt.ttl = 1; /* real TTL would be 1 on a time exceeded packet */
+  ip_pkt.proto = IPPROTO_ICMP;
+  ip_pkt.src_ip = other->s_addr;
+  ip_pkt.dst_ip = dummy.s_addr;
+  ip_pkt.checksum = 0;
+  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 = htonl(port);
+  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));
+
+  /* no go back to calculate ICMP packet checksum */
+  off = sizeof (struct ip_header);
+  icmp_ttl.checksum = htons(calc_checksum((uint16_t*) &packet[off],
+                                          sizeof (struct icmp_ttl_exceeded_header) +
+                                          sizeof (struct ip_header) +
+                                          sizeof (struct icmp_echo_header)));
+  memcpy (&packet[off],
+          &icmp_ttl,
+          sizeof (struct icmp_ttl_exceeded_header));
+
+  memset (&dst, 0, sizeof (dst));
+  dst.sin_family = AF_INET;
+  dst.sin_addr = *other;
+
+  err = sendto(rawsock,
+               packet,
+               sizeof (packet), 0,
+               (struct sockaddr*)&dst,
+               sizeof(dst));
+
+  if (err < 0)
+    {
+      fprintf(stderr,
+              "sendto failed: %s\n", strerror(errno));
+    }
+  else if (sizeof (packet) != (size_t) err)
+    {
+      fprintf(stderr,
+              "Error: partial send of ICMP message\n");
+    }
+}
+
+
+/**
+ * Create an ICMP raw socket.
+ *
+ * @return INVALID_SOCKET on error
+ */
+static SOCKET
+make_raw_socket ()
+{
+  DWORD bOptVal = TRUE;
+  int bOptLen = sizeof(bOptVal);
+  SOCKET ret;
+
+  ret = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
+  if (INVALID_SOCKET == ret)
+    {
+      fprintf (stderr,
+               "Error opening RAW socket: %s\n",
+               strerror (errno));
+      return INVALID_SOCKET;
+    }
+  if (0 != setsockopt(ret, 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(ret, 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 ret;
+}
+
+
+int
+main (int argc, char *const *argv)
+{
+  struct in_addr external;
+  struct in_addr target;
+  WSADATA wsaData;
+
+  unsigned int p;
+
+  if (argc != 4)
+    {
+      fprintf (stderr,
+               "This program must be started with our IP, the targets external IP, and our port as arguments.\n");
+      return 1;
+    }
+  if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
+       (1 != inet_pton (AF_INET, argv[2], &target)) )
+    {
+      fprintf (stderr,
+               "Error parsing IPv4 address: %s\n",
+               strerror (errno));
+      return 1;
+    }
+  if ( (1 != sscanf (argv[3], "%u", &p) ) ||
+       (0 == p) ||
+       (0xFFFF < p) )
+    {
+      fprintf (stderr,
+               "Error parsing port value `%s'\n",
+               argv[3]);
+      return 1;
+    }
+  port = (uint16_t) p;
+
+  if (0 != WSAStartup (MAKEWORD (2, 1), &wsaData))
+    {
+      fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
+      return 2;
+    }
+  if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
+    {
+      fprintf (stderr,
+               "Internal error converting dummy IP to binary.\n");
+      return 2;
+    }
+  if (-1 == (rawsock = make_raw_socket()))
+    return 3;
+  send_icmp (&external,
+             &target);
+  send_icmp_udp (&external,
+                 &target);
+  closesocket (rawsock);
+  WSACleanup ();
+  return 0;
+}
+
+/* end of gnunet-helper-nat-client-windows.c */