iodine/src/iodine.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 <netdb.h>
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#include <netinet/in.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>
#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>
#include <arpa/nameser.h>
#ifdef DARWIN
#include <arpa/nameser8_compat.h>
#endif
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#include "common.h"
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#include "dns.h"
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#include "login.h"
#include "tun.h"
#include "version.h"
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static void send_ping(int fd);
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static void send_chunk(int fd);
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int running = 1;
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char password[33];
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struct sockaddr_in peer;
static char *topdomain;
uint16_t rand_seed;
/* Current IP packet */
static char activepacket[4096];
static int lastlen;
static int packetpos;
static int packetlen;
static uint16_t chunkid;
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static void
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sighandler(int sig)
{
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running = 0;
}
static void
send_packet(int fd, char cmd, const char *data, const size_t datalen)
{
char packet[4096];
struct query q;
char buf[4096];
size_t len;
q.id = ++chunkid;
q.type = T_NULL;
buf[0] = cmd;
len = dns_build_hostname(buf + 1, sizeof(buf) - 1, data, datalen, topdomain);
len = dns_encode(packet, sizeof(packet), &q, QR_QUERY, buf, strlen(buf));
sendto(fd, packet, len, 0, (struct sockaddr*)&peer, sizeof(peer));
}
int
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is_sending()
{
return (packetlen != 0);
}
int
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read_dns(int fd, char *buf, int buflen)
{
struct sockaddr_in from;
char packet[64*1024];
socklen_t addrlen;
struct query q;
int rv;
int r;
addrlen = sizeof(struct sockaddr);
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if ((r = recvfrom(fd, packet, sizeof(packet), 0,
(struct sockaddr*)&from, &addrlen)) == -1) {
warn("recvfrom");
return 0;
}
rv = dns_decode(buf, buflen, &q, QR_ANSWER, packet, r);
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if (is_sending() && chunkid == q.id) {
/* Got ACK on sent packet */
packetpos += lastlen;
if (packetpos == packetlen) {
/* Packet completed */
packetpos = 0;
packetlen = 0;
lastlen = 0;
} else {
/* More to send */
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send_chunk(fd);
}
}
return rv;
}
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static int
tunnel_tun(int tun_fd, int dns_fd)
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{
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unsigned long outlen;
unsigned long inlen;
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char out[64*1024];
char in[64*1024];
size_t read;
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if ((read = read_tun(tun_fd, in, sizeof(in))) <= 0)
return -1;
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outlen = sizeof(out);
inlen = read;
compress2(out, &outlen, in, inlen, 9);
memcpy(activepacket, out, MIN(outlen, sizeof(activepacket)));
lastlen = 0;
packetpos = 0;
packetlen = outlen;
send_chunk(dns_fd);
return read;
}
static int
tunnel_dns(int tun_fd, int dns_fd)
{
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unsigned long outlen;
unsigned long inlen;
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char out[64*1024];
char in[64*1024];
size_t read;
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if ((read = read_dns(dns_fd, in, sizeof(in))) <= 0)
return -1;
outlen = sizeof(out);
inlen = read;
uncompress(out, &outlen, in, inlen);
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write_tun(tun_fd, out, outlen);
if (!is_sending())
send_ping(dns_fd);
return read;
}
static int
tunnel(int tun_fd, int dns_fd)
{
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struct timeval tv;
fd_set fds;
int rv;
int i;
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rv = 0;
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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 (!is_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 (running == 0)
break;
if (i < 0)
err(1, "select");
if (i == 0) /* timeout */
send_ping(dns_fd);
else {
if (FD_ISSET(tun_fd, &fds)) {
if (tunnel_tun(tun_fd, dns_fd) <= 0)
continue;
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}
if (FD_ISSET(dns_fd, &fds)) {
if (tunnel_dns(tun_fd, dns_fd) <= 0)
continue;
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}
}
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}
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return rv;
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}
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static void
send_chunk(int fd)
{
char packet[4096];
struct query q;
char buf[4096];
int avail;
char *p;
int len;
q.id = ++chunkid;
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q.type = T_NULL;
p = activepacket;
p += packetpos;
avail = packetlen - packetpos;
lastlen = dns_build_hostname(buf + 1, sizeof(buf) - 1, p, avail, topdomain);
if (lastlen == avail)
buf[0] = '1';
else
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buf[0] = '0';
len = dns_encode(packet, sizeof(packet), &q, QR_QUERY, buf, strlen(buf));
sendto(fd, packet, len, 0, (struct sockaddr*)&peer, sizeof(peer));
}
void
send_login(int fd, char *login, int len)
{
char data[18];
memset(data, 0, sizeof(data));
memcpy(data, login, MIN(len, 16));
data[16] = (rand_seed >> 8) & 0xff;
data[17] = (rand_seed >> 0) & 0xff;
rand_seed++;
send_packet(fd, 'L', data, sizeof(data));
}
static void
send_ping(int fd)
{
char data[2];
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if (is_sending()) {
lastlen = 0;
packetpos = 0;
packetlen = 0;
}
data[0] = (rand_seed >> 8) & 0xff;
data[1] = (rand_seed >> 0) & 0xff;
rand_seed++;
send_packet(fd, 'P', data, sizeof(data));
}
void
send_version(int fd, uint32_t version)
{
char data[6];
data[0] = (version >> 24) & 0xff;
data[1] = (version >> 16) & 0xff;
data[2] = (version >> 8) & 0xff;
data[3] = (version >> 0) & 0xff;
data[4] = (rand_seed >> 8) & 0xff;
data[5] = (rand_seed >> 0) & 0xff;
rand_seed++;
send_packet(fd, 'V', data, sizeof(data));
}
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static int
handshake(int dns_fd)
{
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struct timeval tv;
uint32_t payload;
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char server[65];
char client[65];
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char login[16];
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char in[4096];
fd_set fds;
int read;
int mtu;
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int seed;
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int i;
int r;
for (i = 0; running && i < 5; i++) {
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tv.tv_sec = i + 1;
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tv.tv_usec = 0;
send_version(dns_fd, VERSION);
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FD_ZERO(&fds);
FD_SET(dns_fd, &fds);
r = select(dns_fd + 1, &fds, NULL, NULL, &tv);
if(r > 0) {
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read = read_dns(dns_fd, in, sizeof(in));
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if(read < 0) {
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perror("read");
continue;
}
if (read >= 8) {
payload = (((in[4] & 0xff) << 24) |
((in[5] & 0xff) << 16) |
((in[6] & 0xff) << 8) |
((in[7] & 0xff)));
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if (strncmp("VACK", in, 4) == 0) {
seed = payload;
printf("Version ok, both running 0x%08x\n", VERSION);
goto perform_login;
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} else {
errx(1, "you run 0x%08x, server runs 0x%08x. giving up\n",
VERSION, payload);
/* NOTREACHED */
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}
} else
warnx("did not receive proper login challenge\n");
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}
printf("Retrying version check...\n");
}
errx(1, "couldn't connect to server");
/* NOTREACHED */
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perform_login:
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login_calculate(login, 16, password, seed);
for (i=0; running && i<5 ;i++) {
tv.tv_sec = i + 1;
tv.tv_usec = 0;
send_login(dns_fd, login, 16);
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FD_ZERO(&fds);
FD_SET(dns_fd, &fds);
r = select(dns_fd + 1, &fds, NULL, NULL, &tv);
if(r > 0) {
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read = read_dns(dns_fd, in, sizeof(in));
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if(read <= 0) {
warn("read");
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continue;
}
if (read > 0) {
if (strncmp("LNAK", in, 4) == 0) {
printf("Bad password\n");
return 1;
} else if (sscanf(in, "%64[^-]-%64[^-]-%d",
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server, client, &mtu) == 3) {
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server[64] = 0;
client[64] = 0;
if (tun_setip(client) == 0 &&
tun_setmtu(mtu) == 0) {
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return 0;
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} else {
warnx("Received handshake with bad data");
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}
} else {
printf("Received bad handshake\n");
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}
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}
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}
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printf("Retrying login...\n");
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}
return 1;
}
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static void
set_target(const char *host)
{
struct hostent *h;
if ((h = gethostbyname(host)) <= 0)
err(1, "couldn't resovle name %s", host);
memset(&peer, 0, sizeof(peer));
peer.sin_family = AF_INET;
peer.sin_port = htons(53);
peer.sin_addr = *((struct in_addr *) h->h_addr);
}
static void
usage() {
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extern char *__progname;
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printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] "
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"nameserver topdomain\n", __progname);
exit(2);
}
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static void
help() {
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extern char *__progname;
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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] [-d device] "
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"[-P password] nameserver topdomain\n", __progname);
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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");
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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(" -P password used for authentication (max 32 chars will be used)\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;
svnver = "$Rev$ from $Date$";
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printf("iodine IP over DNS tunneling client\n");
printf("SVN version: %s\n", svnver);
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exit(0);
}
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int
main(int argc, char **argv)
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{
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struct passwd *pw;
char *username;
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int foreground;
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char *newroot;
char *device;
int choice;
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int tun_fd;
int dns_fd;
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memset(password, 0, 33);
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username = NULL;
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foreground = 0;
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newroot = NULL;
device = NULL;
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chunkid = 0;
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while ((choice = getopt(argc, argv, "vfhu:t:d:P:")) != -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;
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case 'd':
device = optarg;
break;
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case 'P':
strncpy(password, optarg, 32);
password[32] = 0;
break;
default:
usage();
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/* NOTREACHED */
}
}
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();
topdomain = strdup(argv[1]);
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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 (strlen(password) == 0) {
printf("Enter password on stdin:\n");
scanf("%32s", password);
password[32] = 0;
}
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if ((tun_fd = open_tun(device)) == -1)
goto cleanup1;
if ((dns_fd = open_dns(0, INADDR_ANY)) == -1)
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goto cleanup2;
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set_target(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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printf("Sending queries for %s to %s\n", argv[1], argv[0]);
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if (newroot) {
if (chroot(newroot) != 0 || chdir("/") != 0)
err(1, "%s", newroot);
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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;
}