src/iodine.c

   1 /*
   2  * Copyright (c) 2006-2007 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16
  17 #include <stdio.h>
  18 #include <stdint.h>
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <signal.h>
  22 #include <unistd.h>
  23 #include <netdb.h>
  24 #include <netinet/in.h>
  25 #include <sys/types.h>
  26 #include <sys/socket.h>
  27 #include <fcntl.h>
  28 #include <err.h>
  29 #include <pwd.h>
  30 #include <arpa/inet.h>
  31 #include <zlib.h>
  32 #include <arpa/nameser.h>
  33 #ifdef DARWIN
  34 #include <arpa/nameser8_compat.h>
  35 #endif
  36
  37 #include "common.h"
  38 #include "dns.h"
  39 #include "login.h"
  40 #include "tun.h"
  41 #include "version.h"
  42
  43 static void send_ping(int fd);
  44 static void send_chunk(int fd);
  45
  46 int running = 1;
  47 char password[33];
  48
  49 struct sockaddr_in peer;
  50 static char *topdomain;
  51
  52 uint16_t rand_seed;
  53
  54 /* Current IP packet */
  55 static char activepacket[4096];
  56 static char userid;
  57 static int lastlen;
  58 static int packetpos;
  59 static int packetlen;
  60 static uint16_t chunkid;
  61
  62 static void
  63 sighandler(int sig)
  64 {
  65         running = 0;
  66 }
  67
  68 static void
  69 send_packet(int fd, char cmd, const char *data, const size_t datalen)
  70 {
  71         char packet[4096];
  72         struct query q;
  73         char buf[4096];
  74         size_t len;
  75
  76         q.id = ++chunkid;
  77         q.type = T_NULL;
  78
  79         buf[0] = cmd;
  80
  81         len = dns_build_hostname(buf + 1, sizeof(buf) - 1, data, datalen, topdomain);
  82         len = dns_encode(packet, sizeof(packet), &q, QR_QUERY, buf, strlen(buf));
  83
  84         sendto(fd, packet, len, 0, (struct sockaddr*)&peer, sizeof(peer));
  85 }
  86
  87 int
  88 is_sending()
  89 {
  90         return (packetlen != 0);
  91 }
  92
  93 int
  94 read_dns(int fd, char *buf, int buflen)
  95 {
  96         struct sockaddr_in from;
  97         char packet[64*1024];
  98         socklen_t addrlen;
  99         struct query q;
 100         int rv;
 101         int r;
 102
 103         addrlen = sizeof(struct sockaddr);
 104         if ((r = recvfrom(fd, packet, sizeof(packet), 0,
 105                                           (struct sockaddr*)&from, &addrlen)) == -1) {
 106                 warn("recvfrom");
 107                 return 0;
 108         }
 109
 110         rv = dns_decode(buf, buflen, &q, QR_ANSWER, packet, r);
 111
 112         if (is_sending() && chunkid == q.id) {
 113                 /* Got ACK on sent packet */
 114                 packetpos += lastlen;
 115                 if (packetpos == packetlen) {
 116                         /* Packet completed */
 117                         packetpos = 0;
 118                         packetlen = 0;
 119                         lastlen = 0;
 120                 } else {
 121                         /* More to send */
 122                         send_chunk(fd);
 123                 }
 124         }
 125         return rv;
 126 }
 127
 128
 129 static int
 130 tunnel_tun(int tun_fd, int dns_fd)
 131 {
 132         unsigned long outlen;
 133         unsigned long inlen;
 134         char out[64*1024];
 135         char in[64*1024];
 136         size_t read;
 137
 138         if ((read = read_tun(tun_fd, in, sizeof(in))) <= 0)
 139                 return -1;
 140
 141         outlen = sizeof(out);
 142         inlen = read;
 143         compress2((uint8_t*)out, &outlen, (uint8_t*)in, inlen, 9);
 144
 145         memcpy(activepacket, out, MIN(outlen, sizeof(activepacket)));
 146         lastlen = 0;
 147         packetpos = 0;
 148         packetlen = outlen;
 149
 150         send_chunk(dns_fd);
 151
 152         return read;
 153 }
 154
 155 static int
 156 tunnel_dns(int tun_fd, int dns_fd)
 157 {
 158         unsigned long outlen;
 159         unsigned long inlen;
 160         char out[64*1024];
 161         char in[64*1024];
 162         size_t read;
 163
 164         if ((read = read_dns(dns_fd, in, sizeof(in))) <= 0)
 165                 return -1;
 166
 167         outlen = sizeof(out);
 168         inlen = read;
 169         if (uncompress((uint8_t*)out, &outlen, (uint8_t*)in, inlen) != Z_OK)
 170                 return -1;
 171
 172         write_tun(tun_fd, out, outlen);
 173         if (!is_sending())
 174                 send_ping(dns_fd);
 175
 176         return read;
 177 }
 178
 179 static int
 180 tunnel(int tun_fd, int dns_fd)
 181 {
 182         struct timeval tv;
 183         fd_set fds;
 184         int rv;
 185         int i;
 186
 187         rv = 0;
 188
 189         while (running) {
 190                 tv.tv_sec = 1;
 191                 tv.tv_usec = 0;
 192
 193                 FD_ZERO(&fds);
 194                 if (!is_sending())
 195                         FD_SET(tun_fd, &fds);
 196                 FD_SET(dns_fd, &fds);
 197
 198                 i = select(MAX(tun_fd, dns_fd) + 1, &fds, NULL, NULL, &tv);
 199
 200                 if (running == 0)
 201                         break;
 202
 203                 if (i < 0)
 204                         err(1, "select");
 205
 206                 if (i == 0) /* timeout */
 207                         send_ping(dns_fd);
 208                 else {
 209                         if (FD_ISSET(tun_fd, &fds)) {
 210                                 if (tunnel_tun(tun_fd, dns_fd) <= 0)
 211                                         continue;
 212                         }
 213                         if (FD_ISSET(dns_fd, &fds)) {
 214                                 if (tunnel_dns(tun_fd, dns_fd) <= 0)
 215                                         continue;
 216                         }
 217                 }
 218         }
 219
 220         return rv;
 221 }
 222
 223 static void
 224 send_chunk(int fd)
 225 {
 226         char hex[] = "0123456789ABCDEF";
 227         char packet[4096];
 228         struct query q;
 229         char buf[4096];
 230         int avail;
 231         int code;
 232         char *p;
 233         int len;
 234
 235         q.id = ++chunkid;
 236         q.type = T_NULL;
 237
 238         p = activepacket;
 239         p += packetpos;
 240         avail = packetlen - packetpos;
 241
 242         lastlen = dns_build_hostname(buf + 1, sizeof(buf) - 1, p, avail, topdomain);
 243
 244         if (lastlen == avail)
 245                 code = 1;
 246         else
 247                 code = 0;
 248
 249         code |= (userid << 1);
 250         buf[0] = hex[code];
 251         len = dns_encode(packet, sizeof(packet), &q, QR_QUERY, buf, strlen(buf));
 252
 253         sendto(fd, packet, len, 0, (struct sockaddr*)&peer, sizeof(peer));
 254 }
 255
 256 void
 257 send_login(int fd, char *login, int len)
 258 {
 259         char data[19];
 260
 261         memset(data, 0, sizeof(data));
 262         data[0] = userid;
 263         memcpy(&data[1], login, MIN(len, 16));
 264
 265         data[17] = (rand_seed >> 8) & 0xff;
 266         data[18] = (rand_seed >> 0) & 0xff;
 267
 268         rand_seed++;
 269
 270         send_packet(fd, 'L', data, sizeof(data));
 271 }
 272
 273 static void
 274 send_ping(int fd)
 275 {
 276         char data[3];
 277
 278         if (is_sending()) {
 279                 lastlen = 0;
 280                 packetpos = 0;
 281                 packetlen = 0;
 282         }
 283
 284         data[0] = userid;
 285         data[1] = (rand_seed >> 8) & 0xff;
 286         data[2] = (rand_seed >> 0) & 0xff;
 287
 288         rand_seed++;
 289
 290         send_packet(fd, 'P', data, sizeof(data));
 291 }
 292
 293 void
 294 send_version(int fd, uint32_t version)
 295 {
 296         char data[6];
 297
 298         data[0] = (version >> 24) & 0xff;
 299         data[1] = (version >> 16) & 0xff;
 300         data[2] = (version >> 8) & 0xff;
 301         data[3] = (version >> 0) & 0xff;
 302
 303         data[4] = (rand_seed >> 8) & 0xff;
 304         data[5] = (rand_seed >> 0) & 0xff;
 305
 306         rand_seed++;
 307
 308         send_packet(fd, 'V', data, sizeof(data));
 309 }
 310
 311 static int
 312 handshake(int dns_fd)
 313 {
 314         struct timeval tv;
 315         uint32_t payload;
 316         char server[65];
 317         char client[65];
 318         char login[16];
 319         char in[4096];
 320         fd_set fds;
 321         int read;
 322         int mtu;
 323         int seed;
 324         int i;
 325         int r;
 326
 327         for (i = 0; running && i < 5; i++) {
 328                 tv.tv_sec = i + 1;
 329                 tv.tv_usec = 0;
 330
 331                 send_version(dns_fd, VERSION);
 332
 333                 FD_ZERO(&fds);
 334                 FD_SET(dns_fd, &fds);
 335
 336                 r = select(dns_fd + 1, &fds, NULL, NULL, &tv);
 337
 338                 if(r > 0) {
 339                         read = read_dns(dns_fd, in, sizeof(in));
 340
 341                         if(read < 0) {
 342                                 perror("read");
 343                                 continue;
 344                         }
 345
 346                         if (read >= 9) {
 347                                 payload =  (((in[4] & 0xff) << 24) |
 348                                                         ((in[5] & 0xff) << 16) |
 349                                                         ((in[6] & 0xff) << 8) |
 350                                                         ((in[7] & 0xff)));
 351
 352                                 if (strncmp("VACK", in, 4) == 0) {
 353                                         seed = payload;
 354                                         userid = in[8];
 355
 356                                         printf("Version ok, both running 0x%08x. You are user #%d\n", VERSION, userid);
 357                                         goto perform_login;
 358                                 } else if (strncmp("VNAK", in, 4) == 0) {
 359                                         errx(1, "you run 0x%08x, server runs 0x%08x. giving up\n",
 360                                                         VERSION, payload);
 361                                         /* NOTREACHED */
 362                                 } else if (strncmp("VFUL", in, 4) == 0) {
 363                                         errx(1, "server full, all %d slots are taken. try again later\n", payload);
 364                                         /* NOTREACHED */
 365                                 }
 366                         } else
 367                                 warnx("did not receive proper login challenge\n");
 368                 }
 369
 370                 printf("Retrying version check...\n");
 371         }
 372         errx(1, "couldn't connect to server");
 373         /* NOTREACHED */
 374
 375 perform_login:
 376         login_calculate(login, 16, password, seed);
 377
 378         for (i=0; running && i<5 ;i++) {
 379                 tv.tv_sec = i + 1;
 380                 tv.tv_usec = 0;
 381
 382                 send_login(dns_fd, login, 16);
 383
 384                 FD_ZERO(&fds);
 385                 FD_SET(dns_fd, &fds);
 386
 387                 r = select(dns_fd + 1, &fds, NULL, NULL, &tv);
 388
 389                 if(r > 0) {
 390                         read = read_dns(dns_fd, in, sizeof(in));
 391
 392                         if(read <= 0) {
 393                                 warn("read");
 394                                 continue;
 395                         }
 396
 397                         if (read > 0) {
 398                                 if (strncmp("LNAK", in, 4) == 0) {
 399                                         printf("Bad password\n");
 400                                         return 1;
 401                                 } else if (sscanf(in, "%64[^-]-%64[^-]-%d",
 402                                         server, client, &mtu) == 3) {
 403
 404                                         server[64] = 0;
 405                                         client[64] = 0;
 406                                         if (tun_setip(client) == 0 &&
 407                                                 tun_setmtu(mtu) == 0) {
 408                                                 return 0;
 409                                         } else {
 410                                                 warnx("Received handshake with bad data");
 411                                         }
 412                                 } else {
 413                                         printf("Received bad handshake\n");
 414                                 }
 415                         }
 416                 }
 417
 418                 printf("Retrying login...\n");
 419         }
 420
 421         return 1;
 422 }
 423
 424 static void
 425 set_target(const char *host)
 426 {
 427         struct hostent *h;
 428
 429         h = gethostbyname(host);
 430         if (!h)
 431                 err(1, "couldn't resolve name %s", host);
 432
 433         memset(&peer, 0, sizeof(peer));
 434         peer.sin_family = AF_INET;
 435         peer.sin_port = htons(53);
 436         peer.sin_addr = *((struct in_addr *) h->h_addr);
 437 }
 438
 439 static void
 440 usage() {
 441         extern char *__progname;
 442
 443         printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] "
 444                         "nameserver topdomain\n", __progname);
 445         exit(2);
 446 }
 447
 448 static void
 449 help() {
 450         extern char *__progname;
 451
 452         printf("iodine IP over DNS tunneling client\n");
 453         printf("Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] "
 454                         "[-P password] nameserver topdomain\n", __progname);
 455         printf("  -v to print version info and exit\n");
 456         printf("  -h to print this help and exit\n");
 457         printf("  -f to keep running in foreground\n");
 458         printf("  -u name to drop privileges and run as user 'name'\n");
 459         printf("  -t dir to chroot to directory dir\n");
 460         printf("  -d device to set tunnel device name\n");
 461         printf("  -P password used for authentication (max 32 chars will be used)\n");
 462         printf("nameserver is the IP number of the relaying nameserver\n");
 463         printf("topdomain is the FQDN that is delegated to the tunnel endpoint.\n");
 464
 465         exit(0);
 466 }
 467
 468 static void
 469 version() {
 470
 471         printf("iodine IP over DNS tunneling client\n");
 472         printf("version: 0.4.0 from 2007-03-25\n");
 473
 474         exit(0);
 475 }
 476
 477 int
 478 main(int argc, char **argv)
 479 {
 480         struct passwd *pw;
 481         char *username;
 482         int foreground;
 483         char *newroot;
 484         char *device;
 485         int choice;
 486         int tun_fd;
 487         int dns_fd;
 488
 489         memset(password, 0, 33);
 490         username = NULL;
 491         foreground = 0;
 492         newroot = NULL;
 493         device = NULL;
 494         chunkid = 0;
 495
 496         while ((choice = getopt(argc, argv, "vfhu:t:d:P:")) != -1) {
 497                 switch(choice) {
 498                 case 'v':
 499                         version();
 500                         break;
 501                 case 'f':
 502                         foreground = 1;
 503                         break;
 504                 case 'h':
 505                         help();
 506                         break;
 507                 case 'u':
 508                         username = optarg;
 509                         break;
 510                 case 't':
 511                         newroot = optarg;
 512                         break;
 513                 case 'd':
 514                         device = optarg;
 515                         break;
 516                 case 'P':
 517                         strncpy(password, optarg, 32);
 518                         password[32] = 0;
 519                         break;
 520                 default:
 521                         usage();
 522                         /* NOTREACHED */
 523                 }
 524         }
 525
 526         if (geteuid() != 0) {
 527                 printf("Run as root and you'll be happy.\n");
 528                 usage();
 529         }
 530
 531         argc -= optind;
 532         argv += optind;
 533
 534         if (argc != 2)
 535                 usage();
 536
 537         topdomain = strdup(argv[1]);
 538
 539         if(username) {
 540                 pw = getpwnam(username);
 541                 if (!pw) {
 542                         printf("User %s does not exist!\n", username);
 543                         usage();
 544                 }
 545         }
 546
 547         if (strlen(password) == 0) {
 548                 printf("Enter password on stdin:\n");
 549                 scanf("%32s", password);
 550                 password[32] = 0;
 551         }
 552
 553         if ((tun_fd = open_tun(device)) == -1)
 554                 goto cleanup1;
 555         if ((dns_fd = open_dns(0, INADDR_ANY)) == -1)
 556                 goto cleanup2;
 557         set_target(argv[0]);
 558
 559         signal(SIGINT, sighandler);
 560         signal(SIGTERM, sighandler);
 561
 562         if(handshake(dns_fd))
 563                 goto cleanup2;
 564
 565         printf("Sending queries for %s to %s\n", argv[1], argv[0]);
 566
 567         do_chroot(newroot);
 568
 569         if (username) {
 570                 if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) {
 571                         printf("Could not switch to user %s!\n", username);
 572                         usage();
 573                 }
 574         }
 575
 576         if (!foreground) {
 577                 do_detach();
 578         }
 579
 580         tunnel(tun_fd, dns_fd);
 581
 582 cleanup2:
 583         close_dns(dns_fd);
 584         close_tun(tun_fd);
 585 cleanup1:
 586
 587         return 0;
 588 }