iodine/iodine.c
2006-08-24 22:04:12 +00:00

298 lines
5.7 KiB
C

/*
* 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 <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <err.h>
#include <pwd.h>
#include <arpa/inet.h>
#include <zlib.h>
#include "tun.h"
#include "structs.h"
#include "dns.h"
#ifndef MAX
#define MAX(a,b) ((a)>(b)?(a):(b))
#endif
int running = 1;
int tun_fd;
int dns_fd;
static void
sighandler(int sig) {
running = 0;
}
static int
tunnel(int tun_fd, int dns_fd)
{
int i;
int read;
fd_set fds;
struct timeval tv;
char in[64*1024];
long outlen;
char out[64*1024];
while (running) {
tv.tv_sec = 1;
tv.tv_usec = 0;
FD_ZERO(&fds);
if (!dns_sending())
FD_SET(tun_fd, &fds);
FD_SET(dns_fd, &fds);
i = select(MAX(tun_fd, dns_fd) + 1, &fds, NULL, NULL, &tv);
if(i < 0) {
if (running) {
warn("select");
}
return 1;
} else if (i > 0) {
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);
}
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);
}
} else
dns_ping(dns_fd);
}
return 0;
}
static int
handshake(int dns_fd)
{
struct timeval tv;
char server[128];
char client[128];
char in[4096];
int timeout;
fd_set fds;
int read;
int mtu;
int i;
int r;
timeout = 1;
for (i=0; running && i<5 ;i++) {
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));
if(read < 0) {
perror("read");
continue;
}
if (read > 0) {
if (sscanf(in, "%[^-]-%[^-]-%d", server, client, &mtu) == 3) {
if (tun_setip(client) == 0 && tun_setmtu(mtu) == 0)
return 0;
else
warn("Received handshake but b0rk");
}
}
}
printf("Retrying...\n");
}
return 1;
}
static void
usage() {
extern char *__progname;
printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] "
"nameserver topdomain\n", __progname);
exit(2);
}
static void
help() {
extern char *__progname;
printf("iodine IP over DNS tunneling client\n");
printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] "
"nameserver topdomain\n", __progname);
printf(" -v to print version info and exit\n");
printf(" -h to print this help and exit\n");
printf(" -f to keep running in foreground\n");
printf(" -u name to drop privileges and run as user 'name'\n");
printf(" -t dir to chroot to directory dir\n");
printf(" -d device to set tunnel device name\n");
printf("nameserver is the IP number of the relaying nameserver\n");
printf("topdomain is the FQDN that is delegated to the tunnel endpoint.\n");
exit(0);
}
static void
version() {
char *svnver = "$Rev$ from $Date$";
printf("iodine IP over DNS tunneling client\n");
printf("SVN version: %s\n", svnver);
exit(0);
}
int
main(int argc, char **argv)
{
struct passwd *pw;
char *username;
int foreground;
char *newroot;
char *device;
int choice;
username = NULL;
foreground = 0;
newroot = NULL;
device = NULL;
while ((choice = getopt(argc, argv, "vfhu:t:d:")) != -1) {
switch(choice) {
case 'v':
version();
break;
case 'f':
foreground = 1;
break;
case 'h':
help();
break;
case 'u':
username = optarg;
break;
case 't':
newroot = optarg;
break;
case 'd':
device = optarg;
break;
default:
usage();
break;
}
}
if (geteuid() != 0) {
printf("Run as root and you'll be happy.\n");
usage();
}
argc -= optind;
argv += optind;
if (argc != 2)
usage();
if(username) {
pw = getpwnam(username);
if (!pw) {
printf("User %s does not exist!\n", username);
usage();
}
}
if ((tun_fd = open_tun(device)) == -1)
goto cleanup1;
if ((dns_fd = open_dns(argv[1], 0, INADDR_ANY)) == -1)
goto cleanup2;
if (dns_settarget(argv[0]) == -1)
goto cleanup2;
printf("Sending queries for %s to %s\n", argv[1], argv[0]);
signal(SIGINT, sighandler);
signal(SIGTERM, sighandler);
if(handshake(dns_fd))
goto cleanup2;
if (newroot) {
if (chroot(newroot) != 0 || chdir("/") != 0)
err(1, "%s", newroot);
seteuid(geteuid());
setuid(getuid());
}
if (!foreground) {
printf("Detaching from terminal...\n");
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();
}
}
tunnel(tun_fd, dns_fd);
cleanup2:
close_dns(dns_fd);
close_tun(tun_fd);
cleanup1:
return 0;
}