iodine/iodine.c

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5.4 KiB
C
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/*
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* Copyright (c) 2006 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
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*
* 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>
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#include <string.h>
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#include <signal.h>
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#include <unistd.h>
#include <sys/types.h>
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#include <sys/socket.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 "structs.h"
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#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;
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int tun_fd;
int dns_fd;
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static void
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sighandler(int sig) {
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running = 0;
}
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static int
tunnel(int tun_fd, int dns_fd)
{
int i;
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int read;
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fd_set fds;
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struct timeval tv;
char in[64*1024];
long outlen;
char out[64*1024];
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while (running) {
tv.tv_sec = 1;
tv.tv_usec = 0;
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FD_ZERO(&fds);
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if (!dns_sending())
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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) {
if (running) {
warn("select");
}
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return 1;
}
if(i == 0) {
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dns_ping(dns_fd);
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} else {
if(FD_ISSET(tun_fd, &fds)) {
read = read_tun(tun_fd, in, sizeof(in));
if(read <= 0)
continue;
outlen = sizeof(out);
compress2(out, &outlen, in, read, 9);
dns_handle_tun(dns_fd, out, outlen);
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}
if(FD_ISSET(dns_fd, &fds)) {
read = dns_read(dns_fd, in, sizeof(in));
if (read <= 0)
continue;
outlen = sizeof(out);
uncompress(out, &outlen, in, read);
write_tun(tun_fd, out, outlen);
if (!dns_sending())
dns_ping(dns_fd);
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}
}
}
return 0;
}
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static int
handshake(int dns_fd)
{
int i;
int r;
char *p;
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int mtu;
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int read;
fd_set fds;
int timeout;
char in[4096];
struct timeval tv;
timeout = 1;
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for (i=0; running && i<5 ;i++) {
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tv.tv_sec = timeout++;
tv.tv_usec = 0;
dns_handshake(dns_fd);
FD_ZERO(&fds);
FD_SET(dns_fd, &fds);
r = select(dns_fd + 1, &fds, NULL, NULL, &tv);
if(r > 0) {
read = dns_read(dns_fd, in, sizeof(in));
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if(read < 0) {
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perror("read");
continue;
}
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if (read > 0) {
p = strchr(in, '-');
if (p) {
*p++ = '\0';
mtu = atoi(p);
if (tun_setip(in) == 0 && tun_setmtu(atoi(p)) == 0)
return 0;
else
warn("Received handshake but b0rk");
}
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}
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}
printf("Retrying...\n");
}
return 1;
}
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extern char *__progname;
static void
usage() {
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printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] "
"nameserver topdomain\n", __progname);
exit(2);
}
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static void
help() {
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printf("iodine IP over DNS tunneling client\n");
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printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] "
"nameserver topdomain\n", __progname);
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printf(" -f is to keep running in foreground\n");
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("nameserver is the IP number of the relaying nameserver\n");
printf("topdomain is the FQDN that is delegated to the tunnel endpoint.\n");
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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 client\n");
printf("SVN version: %s\n", svnver);
exit(0);
}
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int
main(int argc, char **argv)
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{
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int choice;
char *newroot;
char *username;
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int foreground;
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struct passwd *pw;
newroot = NULL;
username = NULL;
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foreground = 0;
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while ((choice = getopt(argc, argv, "vfhu:t:")) != -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;
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case 't':
newroot = optarg;
break;
default:
usage();
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break;
}
}
if (geteuid() != 0) {
printf("Run as root and you'll be happy.\n");
usage();
}
argc -= optind;
argv += optind;
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if (argc != 2)
usage();
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if(username) {
pw = getpwnam(username);
if (!pw) {
printf("User %s does not exist!\n", username);
usage();
}
}
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if ((tun_fd = open_tun()) == -1)
goto cleanup1;
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if ((dns_fd = open_dns(argv[1], 0)) == -1)
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goto cleanup2;
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if (dns_settarget(argv[0]) == -1)
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goto cleanup2;
printf("Sending queries for %s to %s\n", argv[1], argv[0]);
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signal(SIGINT, sighandler);
signal(SIGTERM, sighandler);
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if(handshake(dns_fd))
goto cleanup2;
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if (newroot) {
if (chroot(newroot) != 0 || chdir("/") != 0)
err(1, "%s", newroot);
seteuid(geteuid());
setuid(getuid());
}
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if (!foreground) {
printf("Detaching from terminal...\n");
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daemon(0, 0);
umask(0);
alarm(0);
}
if (username) {
if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) {
printf("Could not switch to user %s!\n", username);
usage();
}
}
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tunnel(tun_fd, dns_fd);
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cleanup2:
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close_dns(dns_fd);
close_tun(tun_fd);
cleanup1:
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return 0;
}