--- /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-client-windows.c
+ * @brief Tool to help bypass NATs using ICMP method; must run as
+ * root (SUID will do) or administrator on W32
+ * This code will work under GNU/Linux or 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
+#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 unsigned int uid_t;
+typedef SOCKET Socket;
+typedef unsigned short ushort;
+#define ICMP_ECHO 8
+#define IPDEFTTL 64 /* default ttl, from RFC 1340 */
+#define ICMP_TIME_EXCEEDED 11 /* Time Exceeded */
+#define IP_HDRINCL 3 /* int; Header is included with data. */
+#else
+typedef int Socket;
+#endif
+
+/**
+ * Must match IP given in the server.
+ */
+#define DUMMY_IP "192.0.2.86"
+
+#define NAT_TRAV_PORT 22225
+
+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 icmp_echo_packet
+{
+ uint8_t type;
+ uint8_t code;
+ uint16_t checksum;
+ uint32_t reserved;
+ uint32_t data;
+};
+
+struct udp_packet
+{
+ uint16_t src_port;
+
+ uint16_t dst_port;
+
+ uint32_t length;
+};
+
+static Socket rawsock;
+
+static struct in_addr dummy;
+
+static uint32_t port;
+
+#if WIN32
+/**
+ * @param af address family
+ * @param cp the address to print
+ * @param buf where to write the address result
+ */
+static int inet_pton (int af, char *cp, struct in_addr *buf)
+{
+ //ret = WSAStringToAddress (cp, af, NULL, (LPSOCKADDR)buf, &ssize);
+ buf->s_addr = inet_addr(cp);
+ if (buf->s_addr == INADDR_NONE)
+ {
+ fprintf(stderr, "Error %d handling address %s", WSAGetLastError(), cp);
+ return 0;
+ }
+ else
+ return 1;
+}
+#endif
+
+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_echo_packet *echo, uint32_t num)
+{
+ memset(echo, 0, sizeof(struct icmp_echo_packet));
+ echo->type = ICMP_ECHO;
+ echo->code = 0;
+ echo->reserved = 0;
+ echo->checksum = 0;
+ echo->data = htons(num);
+ echo->checksum = htons(calc_checksum((uint16_t*)echo,
+ sizeof (struct icmp_echo_packet)));
+}
+
+
+/**
+ * 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)
+{
+ struct ip_packet ip_pkt;
+ struct icmp_packet icmp_pkt;
+ struct udp_packet udp_pkt;
+
+ struct sockaddr_in dst;
+ char packet[sizeof(ip_pkt) * 2 + sizeof(icmp_pkt) * 2 + sizeof(uint32_t)];
+
+ size_t off;
+ int err;
+
+ /* ip header: send to (known) ip address */
+ off = 0;
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ 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 (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ /* ip header of the presumably 'lost' udp packet */
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
+
+ icmp_pkt.type = 11; /* TTL exceeded */
+ icmp_pkt.code = 0;
+ icmp_pkt.checksum = 0;
+ icmp_pkt.reserved = 0;
+ memcpy(&packet[off], &icmp_pkt, sizeof(icmp_pkt));
+ off += sizeof(icmp_pkt);
+
+ /* build inner IP header */
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = htons(sizeof (ip_pkt) + sizeof(udp_pkt));
+ 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 (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ /* build UDP header */
+ udp_pkt.src_port = htons(NAT_TRAV_PORT); /* FIXME: does this port matter? */
+ udp_pkt.dst_port = htons(NAT_TRAV_PORT);
+
+ memset(&udp_pkt.length, 0, sizeof(uint32_t));
+ udp_pkt.length = htonl(port);
+ memcpy(&packet[off], &udp_pkt, sizeof(udp_pkt));
+ off += sizeof(udp_pkt);
+
+ /* set ICMP checksum */
+ icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[sizeof(ip_pkt)],
+ sizeof (icmp_pkt) + sizeof(ip_pkt) + sizeof(udp_pkt)));
+ memcpy (&packet[sizeof(ip_pkt)], &icmp_pkt, sizeof (icmp_pkt));
+
+
+ memset (&dst, 0, sizeof (dst));
+ dst.sin_family = AF_INET;
+ dst.sin_addr = *other;
+ err = sendto(rawsock,
+ packet,
+ off, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst));
+
+ if (err < 0)
+ {
+ fprintf(stderr,
+ "sendto failed: %s\n", strerror(errno));
+ }
+ else if (err != off)
+ {
+ 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_packet ip_pkt;
+ struct icmp_packet *icmp_pkt;
+ struct icmp_echo_packet icmp_echo;
+ struct sockaddr_in dst;
+ char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet) + sizeof(struct icmp_echo_packet)];
+
+ size_t off;
+ int err;
+
+ /* ip header: send to (known) ip address */
+ off = 0;
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = sizeof (packet); /* huh? */
+ 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 = other->s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
+ memcpy (packet, &ip_pkt, sizeof (struct ip_packet));
+ off += sizeof (ip_pkt);
+ /* icmp reply: time exceeded */
+ icmp_pkt = (struct icmp_packet*) &packet[off];
+ memset(icmp_pkt, 0, sizeof(struct icmp_packet));
+ icmp_pkt->type = ICMP_TIME_EXCEEDED;
+ icmp_pkt->code = 0;
+ icmp_pkt->reserved = 0;
+ icmp_pkt->checksum = 0;
+
+ off += sizeof (struct icmp_packet);
+
+ /* ip header of the presumably 'lost' udp packet */
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
+
+ ip_pkt.id = 1;
+ 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_packet)));
+ memcpy (&packet[off], &ip_pkt, sizeof (struct ip_packet));
+ off += sizeof (struct ip_packet);
+
+ make_echo (other, &icmp_echo, port);
+ memcpy (&packet[off], &icmp_echo, sizeof(struct icmp_echo_packet));
+ off += sizeof (struct icmp_echo_packet);
+
+ icmp_pkt->checksum = htons(calc_checksum((uint16_t*)icmp_pkt,
+ sizeof (struct icmp_packet) + sizeof(struct ip_packet) + sizeof(struct icmp_echo_packet)));
+
+ memset (&dst, 0, sizeof (dst));
+ dst.sin_family = AF_INET;
+ dst.sin_addr = *other;
+ err = sendto(rawsock,
+ packet,
+ off, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst)); /* or sizeof 'struct sockaddr'? */
+ if (err < 0)
+ {
+ fprintf(stderr,
+ "sendto failed: %s\n", strerror(errno));
+ }
+ else if (err != off)
+ {
+ fprintf(stderr,
+ "Error: partial send of ICMP message\n");
+ }
+}
+
+
+static Socket
+make_raw_socket ()
+{
+ const int one = 1;
+ int 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;
+ struct in_addr target;
+#ifndef WIN32
+ uid_t uid;
+#endif
+
+#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 == (rawsock = make_raw_socket()))
+ return 1;
+
+#ifndef WIN32
+ uid = getuid ();
+ if (0 != setresuid (uid, uid, uid))
+ fprintf (stderr,
+ "Failed to setresuid: %s\n",
+ strerror (errno));
+#endif
+ 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;
+ }
+ port = atoi(argv[3]);
+
+ 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 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
+ send_icmp (&external,
+ &target);
+ send_icmp_udp (&external,
+ &target);
+ close (rawsock);
+ return 0;
+}
+
+/* end of gnunet-nat-client.c */
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