iodine/iodined.c

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/*
* Copyright (c) 2006 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
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#include <sys/stat.h>
#include <fcntl.h>
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#include <err.h>
#include <pwd.h>
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#include <arpa/inet.h>
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#include <zlib.h>
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#include "tun.h"
#include "dns.h"
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#ifndef MAX
#define MAX(a,b) ((a)>(b)?(a):(b))
#endif
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int running = 1;
static void
sigint(int sig) {
running = 0;
}
static int
tunnel(int tun_fd, int dns_fd)
{
int i;
int read;
fd_set fds;
struct timeval tv;
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struct tun_frame *frame;
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long buflen;
char buf[64*1024];
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frame = malloc(64*1024);
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while (running) {
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if (dnsd_hasack()) {
tv.tv_sec = 0;
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tv.tv_usec = 50000;
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} else {
tv.tv_sec = 1;
tv.tv_usec = 0;
}
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FD_ZERO(&fds);
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if(!dnsd_haspacket())
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FD_SET(tun_fd, &fds);
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FD_SET(dns_fd, &fds);
i = select(MAX(tun_fd, dns_fd) + 1, &fds, NULL, NULL, &tv);
if(i < 0) {
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if (running)
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warn("select");
return 1;
}
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if (i==0) {
if (dnsd_hasack())
dnsd_forceack(dns_fd);
} else {
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if(FD_ISSET(tun_fd, &fds)) {
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read = read_tun(tun_fd, frame, 64*1024);
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if(read > 0) {
buflen = sizeof(buf);
compress2(buf, &buflen, frame->data, read - 4, 9);
dnsd_queuepacket(buf, buflen);
}
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}
if(FD_ISSET(dns_fd, &fds)) {
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read = dnsd_read(dns_fd, buf, 64*1024-4);
if(read > 0) {
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buflen = 64*1024-4;
uncompress(frame->data, &buflen, buf, read);
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frame->flags = htons(0x0000);
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#ifdef LINUX
frame->proto = htons(0x0800); // Linux wants ETH_P_IP
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#else
frame->proto = htons(0x0002); // BSD wants AF_INET as long word
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#endif
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write_tun(tun_fd, frame, buflen + 4);
}
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}
}
}
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free(frame);
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return 0;
}
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extern char *__progname;
static void
usage() {
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printf("Usage: %s [-v] [-h] [-f] [-u user] topdomain\n", __progname);
exit(2);
}
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static void
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] topdomain\n", __progname);
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printf(" -f to keep running in foreground\n");
printf(" -u name to drop privileges and run as user 'name'\n");
exit(0);
}
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static void
version() {
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char *svnver = "$Rev$ from $Date$";
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printf("iodine IP over DNS tunneling server\n");
printf("SVN version: %s\n", svnver);
exit(0);
}
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int
main(int argc, char **argv)
{
int tun_fd;
int dnsd_fd;
int choice;
char *username;
struct passwd *pw;
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int foreground;
username = NULL;
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foreground = 0;
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if (geteuid() != 0) {
printf("Run as root and you'll be happy.\n");
usage();
}
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while ((choice = getopt(argc, argv, "vfhu:")) != -1) {
switch(choice) {
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case 'v':
version();
break;
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case 'f':
foreground = 1;
break;
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case 'h':
help();
break;
case 'u':
username = optarg;
break;
default:
usage();
break;
}
}
argc -= optind;
argv += optind;
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if (argc != 1) {
usage();
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}
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if (username) {
pw = getpwnam(username);
if (!pw) {
printf("User %s does not exist!\n", username);
usage();
}
}
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tun_fd = open_tun();
dnsd_fd = open_dnsd(argv[0]);
printf("Listening to dns for domain %s\n", argv[0]);
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if (!foreground) {
daemon(0, 0);
umask(0);
alarm(0);
}
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signal(SIGINT, sigint);
if (username) {
if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) {
printf("Could not switch to user %s!\n", username);
usage();
}
printf("Now running as user %s\n", username);
}
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tunnel(tun_fd, dnsd_fd);
close_dnsd(dnsd_fd);
close_tun(tun_fd);
return 0;
}