329 lines
6.9 KiB
C
329 lines
6.9 KiB
C
/*
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* Copyright (c) 2006 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <netinet/in.h>
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#include <signal.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <err.h>
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#include <pwd.h>
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#include <arpa/inet.h>
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#include <netinet/in.h>
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#include <zlib.h>
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#include "tun.h"
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#include "structs.h"
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#include "dns.h"
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#ifndef MAX
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#define MAX(a,b) ((a)>(b)?(a):(b))
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#endif
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int running = 1;
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struct packet packetbuf;
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struct packet outpacket;
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int outid;
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struct query q;
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int my_mtu;
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in_addr_t my_ip;
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static void
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sigint(int sig) {
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running = 0;
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}
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static int
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tunnel(int tun_fd, int dns_fd)
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{
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int i;
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int read;
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int code;
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int ipadder;
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struct in_addr nextip;
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fd_set fds;
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struct timeval tv;
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char in[64*1024];
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long outlen;
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char out[64*1024];
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while (running) {
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if (q.id != 0) {
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tv.tv_sec = 0;
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tv.tv_usec = 5000;
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} else {
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tv.tv_sec = 1;
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tv.tv_usec = 0;
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}
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FD_ZERO(&fds);
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if(outpacket.len == 0)
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FD_SET(tun_fd, &fds);
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FD_SET(dns_fd, &fds);
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i = select(MAX(tun_fd, dns_fd) + 1, &fds, NULL, NULL, &tv);
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if(i < 0) {
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if (running)
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warn("select");
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return 1;
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}
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if (i==0) {
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if (q.id != 0) {
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dnsd_send(dns_fd, &q, outpacket.data, outpacket.len);
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outpacket.len = 0;
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q.id = 0;
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}
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} else {
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if(FD_ISSET(tun_fd, &fds)) {
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read = read_tun(tun_fd, in, sizeof(in));
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if (read <= 0)
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continue;
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outlen = sizeof(out);
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compress2(out, &outlen, in, read, 9);
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memcpy(outpacket.data, out, outlen);
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outpacket.len = outlen;
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}
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if(FD_ISSET(dns_fd, &fds)) {
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read = dnsd_read(dns_fd, &q, in, sizeof(in));
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if (read < 0)
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continue;
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if(in[0] == 'H' || in[0] == 'h') {
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ipadder = htonl(my_ip); // To get the last byte last
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if ((ipadder & 0xFF) == 0xFF) {
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// IP ends with 255.
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ipadder--;
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} else {
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ipadder++;
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}
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nextip.s_addr = ntohl(ipadder);
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read = snprintf(out, sizeof(out), "%s-%d", inet_ntoa(nextip), my_mtu);
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dnsd_send(dns_fd, &q, out, read);
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q.id = 0;
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} else if((in[0] >= '0' && in[0] <= '9')
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|| (in[0] >= 'a' && in[0] <= 'f')
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|| (in[0] >= 'A' && in[0] <= 'F')) {
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if ((in[0] >= '0' && in[0] <= '9'))
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code = in[0] - '0';
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if ((in[0] >= 'a' && in[0] <= 'f'))
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code = in[0] - 'a' + 10;
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if ((in[0] >= 'A' && in[0] <= 'F'))
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code = in[0] - 'A' + 10;
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memcpy(packetbuf.data + packetbuf.offset, in + 1, read - 1);
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packetbuf.len += read - 1;
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packetbuf.offset += read - 1;
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if (code & 1) {
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outlen = sizeof(out);
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uncompress(out, &outlen, packetbuf.data, packetbuf.len);
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write_tun(tun_fd, out, outlen);
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packetbuf.len = packetbuf.offset = 0;
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}
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}
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if (outpacket.len > 0) {
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dnsd_send(dns_fd, &q, outpacket.data, outpacket.len);
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outpacket.len = 0;
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q.id = 0;
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}
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}
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}
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}
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return 0;
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}
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extern char *__progname;
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static void
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usage() {
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printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] [-m mtu] [-l ip address to listen on] "
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"tunnel_ip topdomain\n", __progname);
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exit(2);
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}
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static void
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help() {
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printf("iodine IP over DNS tunneling server\n");
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printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] [-m mtu] [-l ip address to listen on] "
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"tunnel_ip topdomain\n", __progname);
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printf(" -v to print version info and exit\n");
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printf(" -h to print this help and exit\n");
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printf(" -f to keep running in foreground\n");
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printf(" -u name to drop privileges and run as user 'name'\n");
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printf(" -t dir to chroot to directory dir\n");
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printf(" -d device to set tunnel device name\n");
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printf(" -m mtu to set tunnel device mtu\n");
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printf(" -l ip address to listen on for incoming dns traffic (default 0.0.0.0)\n");
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printf("tunnel_ip is the IP number of the local tunnel interface.\n");
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printf("topdomain is the FQDN that is delegated to this server.\n");
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exit(0);
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}
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static void
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version() {
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char *svnver = "$Rev$ from $Date$";
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printf("iodine IP over DNS tunneling server\n");
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printf("SVN version: %s\n", svnver);
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exit(0);
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}
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int
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main(int argc, char **argv)
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{
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int choice;
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int tun_fd;
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int dnsd_fd;
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char *newroot;
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char *username;
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char *device;
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int foreground;
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int mtu;
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struct passwd *pw;
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in_addr_t listen_ip;
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username = NULL;
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newroot = NULL;
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device = NULL;
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foreground = 0;
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mtu = 1024;
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listen_ip = INADDR_ANY;
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packetbuf.len = 0;
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packetbuf.offset = 0;
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outpacket.len = 0;
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q.id = 0;
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while ((choice = getopt(argc, argv, "vfhu:t:d:m:l:")) != -1) {
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switch(choice) {
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case 'v':
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version();
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break;
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case 'f':
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foreground = 1;
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break;
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case 'h':
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help();
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break;
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case 'u':
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username = optarg;
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break;
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case 't':
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newroot = optarg;
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break;
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case 'd':
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device = optarg;
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break;
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case 'm':
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mtu = atoi(optarg);
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break;
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case 'l':
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listen_ip = inet_addr(optarg);
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break;
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default:
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usage();
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break;
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}
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}
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argc -= optind;
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argv += optind;
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if (geteuid() != 0) {
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printf("Run as root and you'll be happy.\n");
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usage();
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}
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if (argc != 2)
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usage();
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if (username) {
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pw = getpwnam(username);
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if (!pw) {
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printf("User %s does not exist!\n", username);
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usage();
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}
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}
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if (mtu == 0) {
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printf("Bad MTU given.\n");
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usage();
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}
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if (listen_ip == INADDR_NONE) {
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printf("Bad IP address to listen on.\n");
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usage();
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}
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if ((tun_fd = open_tun(device)) == -1)
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goto cleanup0;
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if (tun_setip(argv[0]) != 0 || tun_setmtu(mtu) != 0)
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goto cleanup1;
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if ((dnsd_fd = open_dns(argv[1], 53, listen_ip)) == -1)
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goto cleanup2;
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my_ip = inet_addr(argv[0]);
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my_mtu = mtu;
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printf("Listening to dns for domain %s\n", argv[1]);
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if (newroot) {
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if (chroot(newroot) != 0 || chdir("/") != 0)
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err(1, "%s", newroot);
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seteuid(geteuid());
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setuid(getuid());
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}
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if (!foreground) {
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printf("Detaching from terminal...\n");
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daemon(0, 0);
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umask(0);
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alarm(0);
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}
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signal(SIGINT, sigint);
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if (username) {
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if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) {
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printf("Could not switch to user %s!\n", username);
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usage();
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}
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}
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tunnel(tun_fd, dnsd_fd);
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cleanup2:
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close_dns(dnsd_fd);
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cleanup1:
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close_tun(tun_fd);
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cleanup0:
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return 0;
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}
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