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