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iodine/src/iodined.c

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/*
* Copyright (c) 2006-2007 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>
#include <sys/time.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <err.h>
#include <time.h>
#include <pwd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <zlib.h>
#include "common.h"
#include "dns.h"
#include "encoding.h"
#include "base32.h"
#include "user.h"
#include "login.h"
#include "tun.h"
#include "version.h"
static int running = 1;
static char *topdomain;
static char password[33];
static struct encoder *b32;
static int my_mtu;
static in_addr_t my_ip;
static int read_dns(int, struct query *, char *, int);
static void write_dns(int, struct query *, char *, int);
static void
sigint(int sig)
{
running = 0;
}
static int
tunnel_tun(int tun_fd, int dns_fd)
{
unsigned long outlen;
struct ip *header;
char out[64*1024];
char in[64*1024];
int userid;
int read;
if ((read = read_tun(tun_fd, in, sizeof(in))) <= 0)
return 0;
/* find target ip in packet, in is padded with 4 bytes TUN header */
header = (struct ip*) (in + 4);
userid = find_user_by_ip(header->ip_dst.s_addr);
if (userid < 0)
return 0;
outlen = sizeof(out);
compress2((uint8_t*)out, &outlen, (uint8_t*)in, read, 9);
/* if another packet is queued, throw away this one. TODO build queue */
if (users[userid].outpacket.len == 0) {
memcpy(users[userid].outpacket.data, out, outlen);
users[userid].outpacket.len = outlen;
return outlen;
} else {
return 0;
}
}
typedef enum {
VERSION_ACK,
VERSION_NACK,
VERSION_FULL
} version_ack_t;
static void
send_version_response(int fd, version_ack_t ack, uint32_t payload, struct user *u)
{
char out[9];
switch (ack) {
case VERSION_ACK:
strncpy(out, "VACK", sizeof(out));
break;
case VERSION_NACK:
strncpy(out, "VNAK", sizeof(out));
break;
case VERSION_FULL:
strncpy(out, "VFUL", sizeof(out));
break;
}
out[4] = ((payload >> 24) & 0xff);
out[5] = ((payload >> 16) & 0xff);
out[6] = ((payload >> 8) & 0xff);
out[7] = ((payload) & 0xff);
out[8] = u->id;
write_dns(fd, &u->q, out, sizeof(out));
}
static int
tunnel_dns(int tun_fd, int dns_fd)
{
struct in_addr tempip;
struct user dummy;
struct ip *hdr;
unsigned long outlen;
char logindata[16];
char out[64*1024];
char in[64*1024];
char unpacked[64*1024];
char *tmp[2];
int userid;
int touser;
int version;
int read;
int code;
userid = -1;
if ((read = read_dns(dns_fd, &(dummy.q), in, sizeof(in))) <= 0)
return 0;
if(in[0] == 'V' || in[0] == 'v') {
read = unpack_data(unpacked, sizeof(unpacked), &(in[1]), read - 1, b32);
/* Version greeting, compare and send ack/nak */
if (read > 4) {
/* Received V + 32bits version */
version = (((unpacked[0] & 0xff) << 24) |
((unpacked[1] & 0xff) << 16) |
((unpacked[2] & 0xff) << 8) |
((unpacked[3] & 0xff)));
}
if (version == VERSION) {
userid = find_available_user();
if (userid >= 0) {
users[userid].seed = rand();
memcpy(&(users[userid].host), &(dummy.q.from), dummy.q.fromlen);
memcpy(&(users[userid].q), &(dummy.q), sizeof(struct query));
users[userid].addrlen = dummy.q.fromlen;
users[userid].encoder = get_base32_encoder();
send_version_response(dns_fd, VERSION_ACK, users[userid].seed, &users[userid]);
users[userid].q.id = 0;
} else {
/* No space for another user */
send_version_response(dns_fd, VERSION_FULL, USERS, &dummy);
}
} else {
send_version_response(dns_fd, VERSION_NACK, VERSION, &dummy);
}
} else if(in[0] == 'L' || in[0] == 'l') {
read = unpack_data(unpacked, sizeof(unpacked), &(in[1]), read - 1, b32);
/* Login phase, handle auth */
userid = unpacked[0];
if (userid < 0 || userid >= USERS) {
write_dns(dns_fd, &(dummy.q), "BADIP", 5);
return 0; /* illegal id */
}
users[userid].last_pkt = time(NULL);
login_calculate(logindata, 16, password, users[userid].seed);
if (dummy.q.fromlen != users[userid].addrlen ||
memcmp(&(users[userid].host), &(dummy.q.from), dummy.q.fromlen) != 0) {
write_dns(dns_fd, &(dummy.q), "BADIP", 5);
} else {
if (read >= 18 && (memcmp(logindata, unpacked+1, 16) == 0)) {
/* Login ok, send ip/mtu info */
tempip.s_addr = my_ip;
tmp[0] = strdup(inet_ntoa(tempip));
tempip.s_addr = users[userid].tun_ip;
tmp[1] = strdup(inet_ntoa(tempip));
read = snprintf(out, sizeof(out), "%s-%s-%d",
tmp[0], tmp[1], my_mtu);
write_dns(dns_fd, &(dummy.q), out, read);
dummy.q.id = 0;
free(tmp[1]);
free(tmp[0]);
} else {
write_dns(dns_fd, &(dummy.q), "LNAK", 4);
}
}
} else if(in[0] == 'P' || in[0] == 'p') {
read = unpack_data(unpacked, sizeof(unpacked), &(in[1]), read - 1, b32);
/* Ping packet, store userid */
userid = unpacked[0];
if (userid < 0 || userid >= USERS) {
write_dns(dns_fd, &(dummy.q), "BADIP", 5);
return 0; /* illegal id */
}
memcpy(&(users[userid].q), &(dummy.q), sizeof(struct query));
users[userid].last_pkt = time(NULL);
} else if(in[0] == 'Z' || in[0] == 'z') {
/* Case conservation check */
/* Reply with received hostname as data */
write_dns(dns_fd, &(dummy.q), in, read);
return 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;
userid = code >> 1;
if (userid < 0 || userid >= USERS) {
write_dns(dns_fd, &(dummy.q), "BADIP", 5);
return 0; /* illegal id */
}
/* Check sending ip number */
if (dummy.q.fromlen != users[userid].addrlen ||
memcmp(&(users[userid].host), &(dummy.q.from), dummy.q.fromlen) != 0) {
write_dns(dns_fd, &(dummy.q), "BADIP", 5);
} else {
/* decode with this users encoding */
read = unpack_data(unpacked, sizeof(unpacked), &(in[1]), read - 1,
users[userid].encoder);
users[userid].last_pkt = time(NULL);
memcpy(&(users[userid].q), &(dummy.q), sizeof(struct query));
users[userid].addrlen = dummy.q.fromlen;
memcpy(users[userid].inpacket.data + users[userid].inpacket.offset, unpacked, read);
users[userid].inpacket.len += read;
users[userid].inpacket.offset += read;
if (code & 1) {
outlen = sizeof(out);
uncompress((uint8_t*)out, &outlen,
(uint8_t*)users[userid].inpacket.data, users[userid].inpacket.len);
hdr = (struct ip*) (out + 4);
touser = find_user_by_ip(hdr->ip_dst.s_addr);
if (touser == -1) {
/* send the uncompressed packet to tun device */
write_tun(tun_fd, out, outlen);
} else {
/* send the compressed packet to other client
* if another packet is queued, throw away this one. TODO build queue */
if (users[touser].outpacket.len == 0) {
memcpy(users[touser].outpacket.data, users[userid].inpacket.data, users[userid].inpacket.len);
users[touser].outpacket.len = users[userid].inpacket.len;
}
}
users[userid].inpacket.len = users[userid].inpacket.offset = 0;
}
}
}
/* userid must be set for a reply to be sent */
if (userid >= 0 && userid < USERS && dummy.q.fromlen == users[userid].addrlen &&
memcmp(&(users[userid].host), &(dummy.q.from), dummy.q.fromlen) == 0 &&
users[userid].outpacket.len > 0) {
write_dns(dns_fd, &(dummy.q), users[userid].outpacket.data, users[userid].outpacket.len);
users[userid].outpacket.len = 0;
users[userid].q.id = 0;
}
return 0;
}
static int
tunnel(int tun_fd, int dns_fd)
{
struct timeval tv;
fd_set fds;
int i;
int j;
while (running) {
if (users_waiting_on_reply()) {
tv.tv_sec = 0;
tv.tv_usec = 5000;
} else {
tv.tv_sec = 1;
tv.tv_usec = 0;
}
FD_ZERO(&fds);
/* TODO : use some kind of packet queue */
if(!all_users_waiting_to_send()) {
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;
}
if (i==0) {
for (j = 0; j < USERS; j++) {
if (users[j].q.id != 0) {
write_dns(dns_fd, &(users[j].q), users[j].outpacket.data, users[j].outpacket.len);
users[j].outpacket.len = 0;
users[j].q.id = 0;
}
}
} else {
if(FD_ISSET(tun_fd, &fds)) {
tunnel_tun(tun_fd, dns_fd);
continue;
}
if(FD_ISSET(dns_fd, &fds)) {
tunnel_dns(tun_fd, dns_fd);
continue;
}
}
}
return 0;
}
static int
read_dns(int fd, struct query *q, char *buf, int buflen)
{
struct sockaddr_in from;
char packet[64*1024];
char *domain;
socklen_t addrlen;
int rv;
int r;
addrlen = sizeof(struct sockaddr);
r = recvfrom(fd, packet, sizeof(packet), 0, (struct sockaddr*)&from, &addrlen);
if (r > 0) {
dns_decode(buf, buflen, q, QR_QUERY, packet, r);
domain = strstr(q->name, topdomain);
if (domain) {
rv = (int) (domain - q->name);
memcpy(buf, q->name, MIN(rv, buflen));
q->fromlen = addrlen;
memcpy((struct sockaddr*)&q->from, (struct sockaddr*)&from, addrlen);
} else {
rv = 0;
}
} else if (r < 0) {
/* Error */
warn("read dns");
rv = 0;
}
return rv;
}
static void
write_dns(int fd, struct query *q, char *data, int datalen)
{
char buf[64*1024];
int len;
len = dns_encode(buf, sizeof(buf), q, QR_ANSWER, data, datalen);
sendto(fd, buf, len, 0, (struct sockaddr*)&q->from, q->fromlen);
}
static void
usage() {
extern char *__progname;
printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] [-m mtu] "
"[-l ip address to listen on] [-p port] [-P password]"
" tunnel_ip topdomain\n", __progname);
exit(2);
}
static void
help() {
extern char *__progname;
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] [-p port] [-P password]"
" tunnel_ip 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(" -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");
printf(" -p port to listen on for incoming dns traffic (default 53)\n");
printf(" -P password used for authentication (max 32 chars will be used)\n");
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");
exit(0);
}
static void
version() {
char *svnver = "$Rev$ from $Date$";
printf("iodine IP over DNS tunneling server\n");
printf("SVN version: %s\n", svnver);
exit(0);
}
int
main(int argc, char **argv)
{
in_addr_t listen_ip;
struct passwd *pw;
int foreground;
char *username;
char *newroot;
char *device;
int dnsd_fd;
int tun_fd;
int choice;
int port;
int mtu;
username = NULL;
newroot = NULL;
device = NULL;
foreground = 0;
mtu = 1024;
listen_ip = INADDR_ANY;
port = 53;
b32 = get_base32_encoder();
memset(password, 0, sizeof(password));
srand(time(NULL));
while ((choice = getopt(argc, argv, "vfhu:t:d:m:l:p:P:")) != -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;
case 'm':
mtu = atoi(optarg);
break;
case 'l':
listen_ip = inet_addr(optarg);
break;
case 'p':
port = atoi(optarg);
if (port) {
printf("ALERT! Other dns servers expect you to run on port 53.\n");
printf("You must manually forward port 53 to port %d for things to work.\n", port);
}
break;
case 'P':
strncpy(password, optarg, sizeof(password));
password[sizeof(password)-1] = 0;
/* XXX: find better way of cleaning up ps(1) */
memset(optarg, 0, strlen(optarg));
break;
default:
usage();
break;
}
}
argc -= optind;
argv += optind;
if (geteuid() != 0) {
warnx("Run as root and you'll be happy.\n");
usage();
}
if (argc != 2)
usage();
topdomain = strdup(argv[1]);
if (strlen(topdomain) > 128 || topdomain[0] == '.') {
warnx("Use a topdomain max 128 chars long. Do not start it with a dot.\n");
usage();
}
if (username != NULL) {
if ((pw = getpwnam(username)) == NULL) {
warnx("User %s does not exist!\n", username);
usage();
}
}
if (mtu == 0) {
warnx("Bad MTU given.\n");
usage();
}
if (listen_ip == INADDR_NONE) {
warnx("Bad IP address to listen on.\n");
usage();
}
if (strlen(password) == 0)
read_password(password, sizeof(password));
if ((tun_fd = open_tun(device)) == -1)
goto cleanup0;
if (tun_setip(argv[0]) != 0 || tun_setmtu(mtu) != 0)
goto cleanup1;
if ((dnsd_fd = open_dns(port, listen_ip)) == -1)
goto cleanup2;
my_ip = inet_addr(argv[0]);
my_mtu = mtu;
init_users(my_ip);
printf("Listening to dns for domain %s\n", topdomain);
if (foreground == 0)
do_detach();
if (newroot != NULL)
do_chroot(newroot);
signal(SIGINT, sigint);
if (username != NULL) {
if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) {
warnx("Could not switch to user %s!\n", username);
usage();
}
}
tunnel(tun_fd, dnsd_fd);
cleanup2:
close_dns(dnsd_fd);
cleanup1:
close_tun(tun_fd);
cleanup0:
return 0;
}
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