source: src/iodine.c @ 692b59

/*
 * 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 "common.h"
#include "dns.h"
#include "login.h"
#include "tun.h"
#include "version.h"

#ifndef MAX
#define MAX(a,b) ((a)>(b)?(a):(b))
#endif

int running = 1;
char password[33];

static void
sighandler(int sig) {
        running = 0;
}

static int
tunnel_tun(int tun_fd, int dns_fd)
{
        char out[64*1024];
        char in[64*1024];
        size_t outlen;
        int read;

        read = read_tun(tun_fd, in, sizeof(in));
        if(read > 0) {
                outlen = sizeof(out);
                compress2(out, &outlen, in, read, 9);
                dns_handle_tun(dns_fd, out, outlen);
        }

        return read;
}

static int
tunnel_dns(int tun_fd, int dns_fd)
{
        char out[64*1024];
        char in[64*1024];
        size_t outlen;
        int read;

        read = dns_read(dns_fd, in, sizeof(in));
        if (read > 0) {
                outlen = sizeof(out);
                uncompress(out, &outlen, in, read);

                write_tun(tun_fd, out, outlen);
                if (!dns_sending()) 
                        dns_ping(dns_fd);
        }
        
        return read;
}

static int
tunnel(int tun_fd, int dns_fd)
{
        struct timeval tv;
        fd_set fds;
        int i;
        int rv;

        rv = 0;

        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 (running == 0 || i < 0) {
                        rv = 1;
                        break;
                }
                
                if (i == 0) /* timeout */
                        dns_ping(dns_fd);
                else {  
                        if(FD_ISSET(tun_fd, &fds)) {
                                if (tunnel_tun(tun_fd, dns_fd) <= 0)
                                        continue;
                        }
                        if(FD_ISSET(dns_fd, &fds)) {
                                if (tunnel_dns(tun_fd, dns_fd) <= 0)
                                        continue;
                        } 
                }
        }

        return rv;
}

static int
handshake(int dns_fd)
{
        struct timeval tv;
        char server[65];
        char client[65];
        char login[16];
        char in[4096];
        fd_set fds;
        int read;
        int mtu;
        int seed;
        int version;
        int i;
        int r;

        for (i=0; running && i<5 ;i++) {
                tv.tv_sec = i + 1;
                tv.tv_usec = 0;

                dns_send_version(dns_fd, VERSION);
                
                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 (strncmp("VACK", in, 4) == 0) {
                                        if (read >= 8) {
                                                memcpy(&seed, in + 4, 4);
                                                seed = ntohl(seed);
                                                printf("Version ok, both running 0x%08x\n", VERSION);
                                                break;
                                        } else {
                                                printf("Version ok but did not receive proper login challenge\n");
                                        }
                                } else {
                                        memcpy(&version, in + 4, 4);
                                        version = ntohl(version);
                                        printf("You run 0x%08x, server runs 0x%08x. Giving up\n", VERSION, version);
                                        return 1;
                                }
                        }
                }
                
                if (i == 4)
                        return 1;
                printf("Retrying version check...\n");
        }
        
        login_calculate(login, 16, password, seed);
        for (i=0; running && i<5 ;i++) {
                tv.tv_sec = i + 1;
                tv.tv_usec = 0;

                dns_login(dns_fd, login, 16);
                
                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 (strncmp("LNAK", in, 4) == 0) {
                                        printf("Bad password\n");
                                        return 1;
                                } else if (sscanf(in, "%64[^-]-%64[^-]-%d", 
                                        server, client, &mtu) == 3) {
                                        
                                        server[64] = 0;
                                        client[64] = 0;
                                        if (tun_setip(client) == 0 && 
                                                tun_setmtu(mtu) == 0) {
                                                return 0;
                                        } else {
                                                warn("Received handshake with bad data");
                                        }
                                } else {
                                        printf("Received bad handshake\n");
                                }
                        }
                }

                printf("Retrying login...\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;
        int tun_fd;
        int dns_fd;

        username = NULL;
        memset(password, 0, 33);
        foreground = 0;
        newroot = NULL;
        device = NULL;
        
        while ((choice = getopt(argc, argv, "vfhu:t:d: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 'P':
                        strncpy(password, optarg, 32);
                        password[32] = 0;
                        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 (strlen(password) == 0) {
                printf("Enter password on stdin:\n");
                scanf("%32s", password);
                password[32] = 0;
        }

        if ((tun_fd = open_tun(device)) == -1)
                goto cleanup1;
        dns_set_topdomain(argv[1]);
        if ((dns_fd = open_dns(0, INADDR_ANY)) == -1)
                goto cleanup2;
        if (dns_settarget(argv[0]) == -1)
                goto cleanup2;

        signal(SIGINT, sighandler);
        signal(SIGTERM, sighandler);

        if(handshake(dns_fd))
                goto cleanup2;
        
        printf("Sending queries for %s to %s\n", argv[1], argv[0]);

        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;
}