iodine/iodined.c

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6.9 KiB
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/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 <netinet/in.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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struct packet packetbuf;
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struct packet outpacket;
int outid;
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struct query q;
int my_mtu;
in_addr_t my_ip;
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static void
sigint(int sig) {
running = 0;
}
static int
tunnel(int tun_fd, int dns_fd)
{
int i;
int read;
int code;
int ipadder;
struct in_addr nextip;
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fd_set fds;
struct timeval tv;
char in[64*1024];
long outlen;
char out[64*1024];
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while (running) {
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 {
tv.tv_sec = 1;
tv.tv_usec = 0;
}
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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);
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) {
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if (q.id != 0) {
dnsd_send(dns_fd, &q, outpacket.data, outpacket.len);
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outpacket.len = 0;
q.id = 0;
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}
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} else {
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if(FD_ISSET(tun_fd, &fds)) {
read = read_tun(tun_fd, in, sizeof(in));
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if (read <= 0)
continue;
outlen = sizeof(out);
compress2(out, &outlen, in, read, 9);
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memcpy(outpacket.data, out, outlen);
outpacket.len = outlen;
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}
if(FD_ISSET(dns_fd, &fds)) {
read = dnsd_read(dns_fd, &q, in, sizeof(in));
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if (read < 0)
continue;
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if(in[0] == 'H' || in[0] == 'h') {
ipadder = htonl(my_ip); // To get the last byte last
if ((ipadder & 0xFF) == 0xFF) {
// IP ends with 255.
ipadder--;
} else {
ipadder++;
}
nextip.s_addr = ntohl(ipadder);
read = snprintf(out, sizeof(out), "%s-%d", inet_ntoa(nextip), my_mtu);
dnsd_send(dns_fd, &q, out, read);
q.id = 0;
} else if((in[0] >= '0' && in[0] <= '9')
|| (in[0] >= 'a' && in[0] <= 'f')
|| (in[0] >= 'A' && in[0] <= 'F')) {
if ((in[0] >= '0' && in[0] <= '9'))
code = in[0] - '0';
if ((in[0] >= 'a' && in[0] <= 'f'))
code = in[0] - 'a' + 10;
if ((in[0] >= 'A' && in[0] <= 'F'))
code = in[0] - 'A' + 10;
memcpy(packetbuf.data + packetbuf.offset, in + 1, read - 1);
packetbuf.len += read - 1;
packetbuf.offset += read - 1;
if (code & 1) {
outlen = sizeof(out);
uncompress(out, &outlen, packetbuf.data, packetbuf.len);
write_tun(tun_fd, out, outlen);
packetbuf.len = packetbuf.offset = 0;
}
}
if (outpacket.len > 0) {
dnsd_send(dns_fd, &q, outpacket.data, outpacket.len);
outpacket.len = 0;
q.id = 0;
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}
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}
}
}
return 0;
}
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extern char *__progname;
static void
usage() {
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);
exit(2);
}
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static void
help() {
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printf("iodine IP over DNS tunneling server\n");
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");
printf(" -h to print this help and exit\n");
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printf(" -f 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(" -d device to set tunnel device name\n");
printf(" -m mtu to set tunnel device mtu\n");
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");
printf("topdomain is the FQDN that is delegated to this server.\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 server\n");
printf("SVN version: %s\n", svnver);
exit(0);
}
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int
main(int argc, char **argv)
{
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int choice;
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int tun_fd;
int dnsd_fd;
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char *newroot;
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;
in_addr_t listen_ip;
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;
listen_ip = INADDR_ANY;
packetbuf.len = 0;
packetbuf.offset = 0;
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outpacket.len = 0;
q.id = 0;
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while ((choice = getopt(argc, argv, "vfhu:t:d:m:l:")) != -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 'm':
mtu = atoi(optarg);
break;
case 'l':
listen_ip = inet_addr(optarg);
break;
default:
usage();
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break;
}
}
argc -= optind;
argv += optind;
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if (geteuid() != 0) {
printf("Run as root and you'll be happy.\n");
usage();
}
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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 (mtu == 0) {
printf("Bad MTU given.\n");
usage();
}
if (listen_ip == INADDR_NONE) {
printf("Bad IP address to listen on.\n");
usage();
}
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if ((tun_fd = open_tun(device)) == -1)
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goto cleanup0;
if (tun_setip(argv[0]) != 0 || tun_setmtu(mtu) != 0)
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goto cleanup1;
if ((dnsd_fd = open_dns(argv[1], 53, listen_ip)) == -1)
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goto cleanup2;
my_ip = inet_addr(argv[0]);
my_mtu = mtu;
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printf("Listening to dns for domain %s\n", argv[1]);
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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);
}
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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();
}
}
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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;
}