curvetun.c

   1 /*
   2  * curvetun - the cipherspace wormhole creator
   3  * Part of the netsniff-ng project
   4  * Copyright 2011 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,
   5  * Copyright 2011 Emmanuel Roullit.
   6  * Subject to the GPL, version 2.
   7  */
   8
   9 #define _GNU_SOURCE
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <fcntl.h>
  13 #include <string.h>
  14 #include <ctype.h>
  15 #include <getopt.h>
  16 #include <errno.h>
  17 #include <stdbool.h>
  18 #include <limits.h>
  19 #include <sys/types.h>
  20 #include <sys/stat.h>
  21 #include <sys/socket.h>
  22 #include <sys/ptrace.h>
  23 #include <sys/fsuid.h>
  24 #include <netinet/in.h>
  25 #include <unistd.h>
  26 #include <signal.h>
  27
  28 #include "die.h"
  29 #include "str.h"
  30 #include "sig.h"
  31 #include "stun.h"
  32 #include "cookie.h"
  33 #include "ioexact.h"
  34 #include "xmalloc.h"
  35 #include "curvetun.h"
  36 #include "curve.h"
  37 #include "config.h"
  38 #include "curvetun_mgmt.h"
  39 #include "ioops.h"
  40 #include "tprintf.h"
  41 #include "crypto.h"
  42
  43 enum working_mode {
  44         MODE_UNKNOW,
  45         MODE_KEYGEN,
  46         MODE_EXPORT,
  47         MODE_DUMPC,
  48         MODE_DUMPS,
  49         MODE_CLIENT,
  50         MODE_SERVER,
  51 };
  52
  53 volatile sig_atomic_t sigint = 0;
  54
  55 static const char *short_options = "kxc::svhp:t:d:uCS46DN";
  56 static const struct option long_options[] = {
  57         {"client",      optional_argument,      NULL, 'c'},
  58         {"dev",         required_argument,      NULL, 'd'},
  59         {"port",        required_argument,      NULL, 'p'},
  60         {"stun",        required_argument,      NULL, 't'},
  61         {"keygen",      no_argument,            NULL, 'k'},
  62         {"export",      no_argument,            NULL, 'x'},
  63         {"dumpc",       no_argument,            NULL, 'C'},
  64         {"dumps",       no_argument,            NULL, 'S'},
  65         {"no-logging",  no_argument,            NULL, 'N'},
  66         {"server",      no_argument,            NULL, 's'},
  67         {"udp",         no_argument,            NULL, 'u'},
  68         {"ipv4",        no_argument,            NULL, '4'},
  69         {"ipv6",        no_argument,            NULL, '6'},
  70         {"nofork",      no_argument,            NULL, 'D'},
  71         {"version",     no_argument,            NULL, 'v'},
  72         {"help",        no_argument,            NULL, 'h'},
  73         {NULL, 0, NULL, 0}
  74 };
  75
  76 static void signal_handler(int number)
  77 {
  78         switch (number) {
  79         case SIGINT:
  80         case SIGTERM:
  81                 sigint = 1;
  82                 break;
  83         default:
  84                 break;
  85         }
  86 }
  87
  88 static void __noreturn help(void)
  89 {
  90         printf("\ncurvetun %s, lightweight curve25519-based IP tunnel\n", VERSION_STRING);
  91         puts("http://www.netsniff-ng.org\n\n"
  92              "Usage: curvetun [options]\n"
  93              "Options, general:\n"
  94              "  -d|--dev <tun>          Networking tunnel device, e.g. tun0\n"
  95              "  -p|--port <num>         Server port number (mandatory)\n"
  96              "  -t|--stun <server>      Show public IP/Port mapping via STUN\n"
  97              "  -c|--client[=alias]     Client mode, server alias optional\n"
  98              "  -k|--keygen             Generate public/private keypair\n"
  99              "  -x|--export             Export your public data for remote servers\n"
 100              "  -C|--dumpc              Dump parsed clients\n"
 101              "  -S|--dumps              Dump parsed servers\n"
 102              "  -D|--nofork             Do not daemonize\n"
 103              "  -s|--server             Server mode, options follow below\n"
 104              "  -N|--no-logging         Disable server logging (for better anonymity)\n"
 105              "  -u|--udp                Use UDP as carrier instead of TCP\n"
 106              "  -4|--ipv4               Tunnel devices are IPv4\n"
 107              "  -6|--ipv6               Tunnel devices are IPv6\n"
 108              "  -v|--version            Print version and exit\n"
 109              "  -h|--help               Print this help and exit\n\n"
 110              "Example:\n"
 111              "  See curvetun's man page for a configuration example.\n"
 112              "  curvetun --server -4 -u -N --port 6666 --stun stunserver.org\n"
 113              "  curvetun --client=ethz\n\n"
 114              "  curvetun --keygen\n"
 115              "  curvetun --export\n"
 116              "Note:\n"
 117              "  There is no default port specified, so that you are forced\n"
 118              "  to select your own! For client/server status messages see syslog!\n"
 119              "  This software is an experimental prototype intended for researchers.\n\n"
 120              "Secret ingredient: 7647-14-5\n\n"
 121              "Please report bugs to <bugs@netsniff-ng.org>\n"
 122              "Copyright (C) 2011-2013 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
 123              "Swiss federal institute of technology (ETH Zurich)\n"
 124              "License: GNU GPL version 2.0\n"
 125              "This is free software: you are free to change and redistribute it.\n"
 126              "There is NO WARRANTY, to the extent permitted by law.\n");
 127         die();
 128 }
 129
 130 static void __noreturn version(void)
 131 {
 132         printf("\ncurvetun %s, Git id: %s\n", VERSION_LONG, GITVERSION);
 133         puts("lightweight curve25519-based IP tunnel\n"
 134              "http://www.netsniff-ng.org\n\n"
 135              "Please report bugs to <bugs@netsniff-ng.org>\n"
 136              "Copyright (C) 2011-2013 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
 137              "Swiss federal institute of technology (ETH Zurich)\n"
 138              "License: GNU GPL version 2.0\n"
 139              "This is free software: you are free to change and redistribute it.\n"
 140              "There is NO WARRANTY, to the extent permitted by law.\n");
 141         die();
 142 }
 143
 144 static void check_file_or_die(char *home, char *file, int maybeempty)
 145 {
 146         char path[PATH_MAX];
 147         struct stat st;
 148
 149         memset(path, 0, sizeof(path));
 150         slprintf(path, sizeof(path), "%s/%s", home, file);
 151
 152         if (stat(path, &st))
 153                 panic("No such file %s! Type --help for further information\n",
 154                       path);
 155
 156         if (!S_ISREG(st.st_mode))
 157                 panic("%s is not a regular file!\n", path);
 158
 159         if ((st.st_mode & ~S_IFREG) != (S_IRUSR | S_IWUSR))
 160                 panic("You have set too many permissions on %s (%o)!\n",
 161                       path, st.st_mode);
 162
 163         if (maybeempty == 0 && st.st_size == 0)
 164                 panic("%s is empty!\n", path);
 165 }
 166
 167 static void check_config_exists_or_die(char *home)
 168 {
 169         if (!home)
 170                 panic("No home dir specified!\n");
 171
 172         check_file_or_die(home, FILE_CLIENTS, 1);
 173         check_file_or_die(home, FILE_SERVERS, 1);
 174         check_file_or_die(home, FILE_PRIVKEY, 0);
 175         check_file_or_die(home, FILE_PUBKEY, 0);
 176         check_file_or_die(home, FILE_USERNAM, 0);
 177 }
 178
 179 static char *fetch_home_dir(void)
 180 {
 181         char *home = getenv("HOME");
 182         if (!home)
 183                 panic("No HOME defined!\n");
 184         return home;
 185 }
 186
 187 static void write_username(char *home)
 188 {
 189         int fd, ret;
 190         char path[PATH_MAX];
 191         char user[512];
 192
 193         memset(path, 0, sizeof(path));
 194         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 195
 196         printf("Username: [%s] ", getenv("USER"));
 197         fflush(stdout);
 198
 199         memset(user, 0, sizeof(user));
 200         if (fgets(user, sizeof(user), stdin) == NULL)
 201                 panic("Could not read from stdin!\n");
 202         user[sizeof(user) - 1] = 0;
 203         user[strlen(user) - 1] = 0; /* omit last \n */
 204         if (strlen(user) == 0)
 205                 strlcpy(user, getenv("USER"), sizeof(user));
 206
 207         fd = open_or_die_m(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 208
 209         ret = write(fd, user, strlen(user));
 210         if (ret != strlen(user))
 211                 panic("Could not write username!\n");
 212
 213         close(fd);
 214
 215         printf("Username written to %s!\n", path);
 216 }
 217
 218 static void create_curvedir(char *home)
 219 {
 220         int ret;
 221         char path[PATH_MAX];
 222
 223         memset(path, 0, sizeof(path));
 224         slprintf(path, sizeof(path), "%s/%s", home, ".curvetun/");
 225
 226         errno = 0;
 227
 228         ret = mkdir(path, S_IRWXU);
 229         if (ret < 0 && errno != EEXIST)
 230                 panic("Cannot create curvetun dir!\n");
 231
 232         printf("curvetun directory %s created!\n", path);
 233         /* We also create empty files for clients and servers! */
 234
 235         memset(path, 0, sizeof(path));
 236         slprintf(path, sizeof(path), "%s/%s", home, FILE_CLIENTS);
 237
 238         create_or_die(path, S_IRUSR | S_IWUSR);
 239
 240         printf("Empty client file written to %s!\n", path);
 241
 242         memset(path, 0, sizeof(path));
 243         slprintf(path, sizeof(path), "%s/%s", home, FILE_SERVERS);
 244
 245         create_or_die(path, S_IRUSR | S_IWUSR);
 246
 247         printf("Empty server file written to %s!\n", path);
 248 }
 249
 250 static void create_keypair(char *home)
 251 {
 252         int fd, err = 0;
 253         ssize_t ret;
 254         unsigned char publickey[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES] = { 0 };
 255         unsigned char secretkey[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES] = { 0 };
 256         char path[PATH_MAX];
 257         const char * errstr = NULL;
 258
 259         printf("Reading from %s (this may take a while) ...\n", HIG_ENTROPY_SOURCE);
 260
 261         gen_key_bytes(secretkey, sizeof(secretkey));
 262         crypto_scalarmult_curve25519_base(publickey, secretkey);
 263
 264         memset(path, 0, sizeof(path));
 265         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 266
 267         fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 268         if (fd < 0) {
 269                 err = EIO;
 270                 errstr = "Cannot open pubkey file!\n";
 271                 goto out_noclose;
 272         }
 273
 274         ret = write(fd, publickey, sizeof(publickey));
 275         if (ret != sizeof(publickey)) {
 276                 err = EIO;
 277                 errstr = "Cannot write public key!\n";
 278                 goto out;
 279         }
 280
 281         close(fd);
 282
 283         printf("Public key written to %s!\n", path);
 284
 285         memset(path, 0, sizeof(path));
 286         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 287
 288         fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 289         if (fd < 0) {
 290                 err = EIO;
 291                 errstr = "Cannot open privkey file!\n";
 292                 goto out_noclose;
 293         }
 294
 295         ret = write(fd, secretkey, sizeof(secretkey));
 296         if (ret != sizeof(secretkey)) {
 297                 err = EIO;
 298                 errstr = "Cannot write private key!\n";
 299                 goto out;
 300         }
 301 out:
 302         close(fd);
 303 out_noclose:
 304         xmemset(publickey, 0, sizeof(publickey));
 305         xmemset(secretkey, 0, sizeof(secretkey));
 306
 307         if (err)
 308                 panic("%s: %s", errstr, strerror(errno));
 309         else
 310                 printf("Private key written to %s!\n", path);
 311 }
 312
 313 static void check_config_keypair_or_die(char *home)
 314 {
 315         int fd, err;
 316         ssize_t ret;
 317         const char * errstr = NULL;
 318         unsigned char publickey[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 319         unsigned char publicres[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 320         unsigned char secretkey[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES];
 321         char path[PATH_MAX];
 322
 323         memset(path, 0, sizeof(path));
 324         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 325
 326         fd = open(path, O_RDONLY);
 327         if (fd < 0) {
 328                 err = EIO;
 329                 errstr = "Cannot open privkey file!\n";
 330                 goto out;
 331         }
 332
 333         ret = read(fd, secretkey, sizeof(secretkey));
 334         if (ret != sizeof(secretkey)) {
 335                 err = EIO;
 336                 errstr = "Cannot read private key!\n";
 337                 goto out;
 338         }
 339
 340         close(fd);
 341
 342         memset(path, 0, sizeof(path));
 343         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 344
 345         fd = open(path, O_RDONLY);
 346         if (fd < 0) {
 347                 err = EIO;
 348                 errstr = "Cannot open pubkey file!\n";
 349                 goto out;
 350         }
 351
 352         ret = read(fd, publickey, sizeof(publickey));
 353         if (ret != sizeof(publickey)) {
 354                 err = EIO;
 355                 errstr = "Cannot read public key!\n";
 356                 goto out;
 357         }
 358
 359         crypto_scalarmult_curve25519_base(publicres, secretkey);
 360
 361         err = crypto_verify_32(publicres, publickey);
 362         if (err) {
 363                 err = EINVAL;
 364                 errstr = "WARNING: your keypair is corrupted!!! You need to "
 365                          "generate new keys!!!\n";
 366                 goto out;
 367         }
 368 out:
 369         close(fd);
 370
 371         xmemset(publickey, 0, sizeof(publickey));
 372         xmemset(publicres, 0, sizeof(publicres));
 373         xmemset(secretkey, 0, sizeof(secretkey));
 374
 375         if (err)
 376                 panic("%s: %s\n", errstr, strerror(errno));
 377 }
 378
 379 static int main_keygen(char *home)
 380 {
 381         create_curvedir(home);
 382         write_username(home);
 383         create_keypair(home);
 384         check_config_keypair_or_die(home);
 385
 386         return 0;
 387 }
 388
 389 static int main_export(char *home)
 390 {
 391         int fd, i;
 392         ssize_t ret;
 393         char path[PATH_MAX], tmp[64];
 394
 395         check_config_exists_or_die(home);
 396         check_config_keypair_or_die(home);
 397
 398         printf("Your exported public information:\n\n");
 399
 400         memset(path, 0, sizeof(path));
 401         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 402
 403         fd = open_or_die(path, O_RDONLY);
 404
 405         while ((ret = read(fd, tmp, sizeof(tmp))) > 0) {
 406                 ret = write(STDOUT_FILENO, tmp, ret);
 407         }
 408
 409         close(fd);
 410
 411         printf(";");
 412
 413         memset(path, 0, sizeof(path));
 414         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 415
 416         fd = open_or_die(path, O_RDONLY);
 417
 418         ret = read(fd, tmp, sizeof(tmp));
 419         if (ret != crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES)
 420                 panic("Cannot read public key!\n");
 421
 422         for (i = 0; i < ret; ++i)
 423                 if (i == ret - 1)
 424                         printf("%02x\n\n", (unsigned char) tmp[i]);
 425                 else
 426                         printf("%02x:", (unsigned char) tmp[i]);
 427
 428         close(fd);
 429         fflush(stdout);
 430
 431         return 0;
 432 }
 433
 434 static int main_dumpc(char *home)
 435 {
 436         check_config_exists_or_die(home);
 437         check_config_keypair_or_die(home);
 438
 439         printf("Your clients:\n\n");
 440
 441         parse_userfile_and_generate_user_store_or_die(home);
 442
 443         dump_user_store();
 444
 445         destroy_user_store();
 446
 447         printf("\n");
 448         die();
 449         return 0;
 450 }
 451
 452 static int main_dumps(char *home)
 453 {
 454         check_config_exists_or_die(home);
 455         check_config_keypair_or_die(home);
 456
 457         printf("Your servers:\n\n");
 458
 459         parse_userfile_and_generate_serv_store_or_die(home);
 460
 461         dump_serv_store();
 462
 463         destroy_serv_store();
 464
 465         printf("\n");
 466         die();
 467         return 0;
 468 }
 469
 470 static void daemonize(const char *lockfile)
 471 {
 472         char pidstr[8];
 473         mode_t lperm = S_IRWXU | S_IRGRP | S_IXGRP; /* 0750 */
 474         int lfp;
 475
 476         if (getppid() == 1)
 477                 return;
 478
 479         if (daemon(0, 1))
 480                 panic("Cannot daemonize: %s", strerror(errno));
 481
 482         to_std_log(&stdout);
 483         to_std_log(&stderr);
 484
 485         umask(lperm);
 486         if (lockfile) {
 487                 lfp = open(lockfile, O_RDWR | O_CREAT | O_EXCL,
 488                            S_IRUSR | S_IWUSR | S_IRGRP);
 489                 if (lfp < 0)
 490                         syslog_panic("Cannot create lockfile at %s! "
 491                                      "curvetun server already running?\n",
 492                                      lockfile);
 493
 494                 slprintf(pidstr, sizeof(pidstr), "%u", getpid());
 495                 if (write(lfp, pidstr, strlen(pidstr)) <= 0)
 496                         syslog_panic("Could not write pid to pidfile %s",
 497                                      lockfile);
 498
 499                 close(lfp);
 500         }
 501 }
 502
 503 static int main_client(char *home, char *dev, char *alias, int daemon)
 504 {
 505         int ret, udp;
 506         char *host, *port;
 507
 508         check_config_exists_or_die(home);
 509         check_config_keypair_or_die(home);
 510
 511         parse_userfile_and_generate_serv_store_or_die(home);
 512
 513         get_serv_store_entry_by_alias(alias, alias ? strlen(alias) + 1 : 0,
 514                                       &host, &port, &udp);
 515         if (!host || !port || udp < 0)
 516                 panic("Did not find alias/entry in configuration!\n");
 517
 518         printf("Using [%s] -> %s:%s via %s as endpoint!\n",
 519                alias ? : "default", host, port, udp ? "udp" : "tcp");
 520         if (daemon)
 521                 daemonize(NULL);
 522
 523         ret = client_main(home, dev, host, port, udp);
 524
 525         destroy_serv_store();
 526
 527         return ret;
 528 }
 529
 530 static int main_server(char *home, char *dev, char *port, int udp,
 531                        int ipv4, int daemon, int log)
 532 {
 533         int ret;
 534
 535         check_config_exists_or_die(home);
 536         check_config_keypair_or_die(home);
 537
 538         if (daemon)
 539                 daemonize(LOCKFILE);
 540
 541         ret = server_main(home, dev, port, udp, ipv4, log);
 542
 543         unlink(LOCKFILE);
 544
 545         return ret;
 546 }
 547
 548 int main(int argc, char **argv)
 549 {
 550         int ret = 0, c, opt_index, udp = 0, ipv4 = -1, daemon = 1, log = 1;
 551         char *port = NULL, *stun = NULL, *dev = NULL, *home = NULL, *alias = NULL;
 552         enum working_mode wmode = MODE_UNKNOW;
 553
 554         setfsuid(getuid());
 555         setfsgid(getgid());
 556
 557         home = fetch_home_dir();
 558
 559         while ((c = getopt_long(argc, argv, short_options, long_options,
 560                &opt_index)) != EOF) {
 561                 switch (c) {
 562                 case 'h':
 563                         help();
 564                         break;
 565                 case 'v':
 566                         version();
 567                         break;
 568                 case 'D':
 569                         daemon = 0;
 570                         break;
 571                 case 'N':
 572                         log = 0;
 573                         break;
 574                 case 'C':
 575                         wmode = MODE_DUMPC;
 576                         break;
 577                 case 'S':
 578                         wmode = MODE_DUMPS;
 579                         break;
 580                 case 'c':
 581                         wmode = MODE_CLIENT;
 582                         if (optarg) {
 583                                 if (*optarg == '=')
 584                                         optarg++;
 585                                 alias = xstrdup(optarg);
 586                         }
 587                         break;
 588                 case 'd':
 589                         dev = xstrdup(optarg);
 590                         break;
 591                 case 'k':
 592                         wmode = MODE_KEYGEN;
 593                         break;
 594                 case '4':
 595                         ipv4 = 1;
 596                         break;
 597                 case '6':
 598                         ipv4 = 0;
 599                         break;
 600                 case 'x':
 601                         wmode = MODE_EXPORT;
 602                         break;
 603                 case 's':
 604                         wmode = MODE_SERVER;
 605                         break;
 606                 case 'u':
 607                         udp = 1;
 608                         break;
 609                 case 't':
 610                         stun = xstrdup(optarg);
 611                         break;
 612                 case 'p':
 613                         port = xstrdup(optarg);
 614                         break;
 615                 case '?':
 616                         switch (optopt) {
 617                         case 't':
 618                         case 'd':
 619                         case 'u':
 620                         case 'p':
 621                                 panic("Option -%c requires an argument!\n",
 622                                       optopt);
 623                         default:
 624                                 if (isprint(optopt))
 625                                         printf("Unknown option character `0x%X\'!\n", optopt);
 626                                 die();
 627                         }
 628                 default:
 629                         break;
 630                 }
 631         }
 632
 633         if (argc < 2)
 634                 help();
 635
 636         register_signal(SIGINT, signal_handler);
 637         register_signal(SIGHUP, signal_handler);
 638         register_signal(SIGTERM, signal_handler);
 639         register_signal(SIGPIPE, signal_handler);
 640
 641         curve25519_selftest();
 642
 643         switch (wmode) {
 644         case MODE_KEYGEN:
 645                 ret = main_keygen(home);
 646                 break;
 647         case MODE_EXPORT:
 648                 ret = main_export(home);
 649                 break;
 650         case MODE_DUMPC:
 651                 ret = main_dumpc(home);
 652                 break;
 653         case MODE_DUMPS:
 654                 ret = main_dumps(home);
 655                 break;
 656         case MODE_CLIENT:
 657                 ret = main_client(home, dev, alias, daemon);
 658                 break;
 659         case MODE_SERVER:
 660                 if (!port)
 661                         panic("No port specified!\n");
 662                 if (stun)
 663                         print_stun_probe(stun, 3478, strtoul(port, NULL, 10));
 664                 ret = main_server(home, dev, port, udp, ipv4, daemon, log);
 665                 break;
 666         default:
 667                 die();
 668         }
 669
 670         free(dev);
 671         free(stun);
 672         free(port);
 673         free(alias);
 674
 675         return ret;
 676 }