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 "xutils.h"
  29 #include "die.h"
  30 #include "str.h"
  31 #include "cookie.h"
  32 #include "ioexact.h"
  33 #include "xmalloc.h"
  34 #include "curvetun.h"
  35 #include "curve.h"
  36 #include "ct_usermgmt.h"
  37 #include "ct_servmgmt.h"
  38 #include "ioops.h"
  39 #include "tprintf.h"
  40 #include "crypto_verify_32.h"
  41 #include "crypto_box_curve25519xsalsa20poly1305.h"
  42 #include "crypto_scalarmult_curve25519.h"
  43 #include "crypto_auth_hmacsha512256.h"
  44
  45 #define CURVETUN_ENTROPY_SOURCE "/dev/random"
  46
  47 extern void print_stun_probe(char *server, uint16_t sport, uint16_t tunport);
  48
  49 enum working_mode {
  50         MODE_UNKNOW,
  51         MODE_KEYGEN,
  52         MODE_EXPORT,
  53         MODE_DUMPC,
  54         MODE_DUMPS,
  55         MODE_CLIENT,
  56         MODE_SERVER,
  57 };
  58
  59 volatile sig_atomic_t sigint = 0;
  60
  61 static const char *short_options = "kxc::svhp:t:d:uCS46DN";
  62 static const struct option long_options[] = {
  63         {"client",      optional_argument,      NULL, 'c'},
  64         {"dev",         required_argument,      NULL, 'd'},
  65         {"port",        required_argument,      NULL, 'p'},
  66         {"stun",        required_argument,      NULL, 't'},
  67         {"keygen",      no_argument,            NULL, 'k'},
  68         {"export",      no_argument,            NULL, 'x'},
  69         {"dumpc",       no_argument,            NULL, 'C'},
  70         {"dumps",       no_argument,            NULL, 'S'},
  71         {"no-logging",  no_argument,            NULL, 'N'},
  72         {"server",      no_argument,            NULL, 's'},
  73         {"udp",         no_argument,            NULL, 'u'},
  74         {"ipv4",        no_argument,            NULL, '4'},
  75         {"ipv6",        no_argument,            NULL, '6'},
  76         {"nofork",      no_argument,            NULL, 'D'},
  77         {"version",     no_argument,            NULL, 'v'},
  78         {"help",        no_argument,            NULL, 'h'},
  79         {NULL, 0, NULL, 0}
  80 };
  81
  82 static void signal_handler(int number)
  83 {
  84         switch (number) {
  85         case SIGINT:
  86         case SIGTERM:
  87                 sigint = 1;
  88                 break;
  89         default:
  90                 break;
  91         }
  92 }
  93
  94 static void __noreturn help(void)
  95 {
  96         printf("\ncurvetun %s, lightweight curve25519-based VPN/IP tunnel\n", VERSION_STRING);
  97         puts("http://www.netsniff-ng.org\n\n"
  98              "Usage: curvetun [options]\n"
  99              "Options, general:\n"
 100              "  -d|--dev <tun>          Networking tunnel device, e.g. tun0\n"
 101              "  -p|--port <num>         Server port number (mandatory)\n"
 102              "  -t|--stun <server>      Show public IP/Port mapping via STUN\n"
 103              "  -c|--client[=alias]     Client mode, server alias optional\n"
 104              "  -k|--keygen             Generate public/private keypair\n"
 105              "  -x|--export             Export your public data for remote servers\n"
 106              "  -C|--dumpc              Dump parsed clients\n"
 107              "  -S|--dumps              Dump parsed servers\n"
 108              "  -D|--nofork             Do not daemonize\n"
 109              "  -s|--server             Server mode, options follow below\n"
 110              "  -N|--no-logging         Disable server logging (for better anonymity)\n"
 111              "  -u|--udp                Use UDP as carrier instead of TCP\n"
 112              "  -4|--ipv4               Tunnel devices are IPv4\n"
 113              "  -6|--ipv6               Tunnel devices are IPv6\n"
 114              "  -v|--version            Print version and exit\n"
 115              "  -h|--help               Print this help and exit\n\n"
 116              "Example:\n"
 117              "  See curvetun's man page for a configuration example.\n"
 118              "  curvetun --server -4 -u -N --port 6666 --stun stunserver.org\n"
 119              "  curvetun --client=ethz\n\n"
 120              "  curvetun --keygen\n"
 121              "  curvetun --export\n"
 122              "Note:\n"
 123              "  There is no default port specified, so that you are forced\n"
 124              "  to select your own! For client/server status messages see syslog!\n"
 125              "  This software is an experimental prototype intended for researchers.\n\n"
 126              "Secret ingredient: 7647-14-5\n\n"
 127              "Please report bugs to <bugs@netsniff-ng.org>\n"
 128              "Copyright (C) 2011-2013 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
 129              "Swiss federal institute of technology (ETH Zurich)\n"
 130              "License: GNU GPL version 2.0\n"
 131              "This is free software: you are free to change and redistribute it.\n"
 132              "There is NO WARRANTY, to the extent permitted by law.\n");
 133         die();
 134 }
 135
 136 static void __noreturn version(void)
 137 {
 138         printf("\ncurvetun %s, lightweight curve25519-based VPN/IP tunnel\n", VERSION_LONG);
 139         puts("http://www.netsniff-ng.org\n\n"
 140              "Please report bugs to <bugs@netsniff-ng.org>\n"
 141              "Copyright (C) 2011-2013 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
 142              "Swiss federal institute of technology (ETH Zurich)\n"
 143              "License: GNU GPL version 2.0\n"
 144              "This is free software: you are free to change and redistribute it.\n"
 145              "There is NO WARRANTY, to the extent permitted by law.\n");
 146         die();
 147 }
 148
 149 static void check_file_or_die(char *home, char *file, int maybeempty)
 150 {
 151         char path[PATH_MAX];
 152         struct stat st;
 153
 154         memset(path, 0, sizeof(path));
 155         slprintf(path, sizeof(path), "%s/%s", home, file);
 156
 157         if (stat(path, &st))
 158                 panic("No such file %s! Type --help for further information\n",
 159                       path);
 160
 161         if (!S_ISREG(st.st_mode))
 162                 panic("%s is not a regular file!\n", path);
 163
 164         if ((st.st_mode & ~S_IFREG) != (S_IRUSR | S_IWUSR))
 165                 panic("You have set too many permissions on %s (%o)!\n",
 166                       path, st.st_mode);
 167
 168         if (maybeempty == 0 && st.st_size == 0)
 169                 panic("%s is empty!\n", path);
 170 }
 171
 172 static void check_config_exists_or_die(char *home)
 173 {
 174         if (!home)
 175                 panic("No home dir specified!\n");
 176
 177         check_file_or_die(home, FILE_CLIENTS, 1);
 178         check_file_or_die(home, FILE_SERVERS, 1);
 179         check_file_or_die(home, FILE_PRIVKEY, 0);
 180         check_file_or_die(home, FILE_PUBKEY, 0);
 181         check_file_or_die(home, FILE_USERNAM, 0);
 182 }
 183
 184 static char *fetch_home_dir(void)
 185 {
 186         char *home = getenv("HOME");
 187         if (!home)
 188                 panic("No HOME defined!\n");
 189         return home;
 190 }
 191
 192 static void write_username(char *home)
 193 {
 194         int fd, ret;
 195         char path[PATH_MAX];
 196         char user[512];
 197
 198         memset(path, 0, sizeof(path));
 199         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 200
 201         printf("Username: [%s] ", getenv("USER"));
 202         fflush(stdout);
 203
 204         memset(user, 0, sizeof(user));
 205         if (fgets(user, sizeof(user), stdin) == NULL)
 206                 panic("Could not read from stdin!\n");
 207         user[sizeof(user) - 1] = 0;
 208         user[strlen(user) - 1] = 0; /* omit last \n */
 209         if (strlen(user) == 0)
 210                 strlcpy(user, getenv("USER"), sizeof(user));
 211
 212         fd = open_or_die_m(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 213
 214         ret = write(fd, user, strlen(user));
 215         if (ret != strlen(user))
 216                 panic("Could not write username!\n");
 217
 218         close(fd);
 219
 220         printf("Username written to %s!\n", path);
 221 }
 222
 223 static void create_curvedir(char *home)
 224 {
 225         int ret;
 226         char path[PATH_MAX];
 227
 228         memset(path, 0, sizeof(path));
 229         slprintf(path, sizeof(path), "%s/%s", home, ".curvetun/");
 230
 231         errno = 0;
 232
 233         ret = mkdir(path, S_IRWXU);
 234         if (ret < 0 && errno != EEXIST)
 235                 panic("Cannot create curvetun dir!\n");
 236
 237         printf("curvetun directory %s created!\n", path);
 238         /* We also create empty files for clients and servers! */
 239
 240         memset(path, 0, sizeof(path));
 241         slprintf(path, sizeof(path), "%s/%s", home, FILE_CLIENTS);
 242
 243         create_or_die(path, S_IRUSR | S_IWUSR);
 244
 245         printf("Empty client file written to %s!\n", path);
 246
 247         memset(path, 0, sizeof(path));
 248         slprintf(path, sizeof(path), "%s/%s", home, FILE_SERVERS);
 249
 250         create_or_die(path, S_IRUSR | S_IWUSR);
 251
 252         printf("Empty server file written to %s!\n", path);
 253 }
 254
 255 static void create_keypair(char *home)
 256 {
 257         int fd, err = 0;
 258         ssize_t ret;
 259         unsigned char publickey[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES] = { 0 };
 260         unsigned char secretkey[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES] = { 0 };
 261         char path[PATH_MAX];
 262         const char * errstr = NULL;
 263
 264         printf("Reading from %s (this may take a while) ...\n", CURVETUN_ENTROPY_SOURCE);
 265
 266         fd = open_or_die(CURVETUN_ENTROPY_SOURCE, O_RDONLY);
 267
 268         ret = read_exact(fd, secretkey, sizeof(secretkey), 0);
 269         if (ret != sizeof(secretkey)) {
 270                 err = EIO;
 271                 errstr = "Cannot read from "CURVETUN_ENTROPY_SOURCE"!\n";
 272                 goto out;
 273         }
 274
 275         close(fd);
 276
 277         crypto_scalarmult_curve25519_base(publickey, secretkey);
 278
 279         memset(path, 0, sizeof(path));
 280         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 281
 282         fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 283         if (fd < 0) {
 284                 err = EIO;
 285                 errstr = "Cannot open pubkey file!\n";
 286                 goto out_noclose;
 287         }
 288
 289         ret = write(fd, publickey, sizeof(publickey));
 290         if (ret != sizeof(publickey)) {
 291                 err = EIO;
 292                 errstr = "Cannot write public key!\n";
 293                 goto out;
 294         }
 295
 296         close(fd);
 297
 298         printf("Public key written to %s!\n", path);
 299
 300         memset(path, 0, sizeof(path));
 301         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 302
 303         fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 304         if (fd < 0) {
 305                 err = EIO;
 306                 errstr = "Cannot open privkey file!\n";
 307                 goto out_noclose;
 308         }
 309
 310         ret = write(fd, secretkey, sizeof(secretkey));
 311         if (ret != sizeof(secretkey)) {
 312                 err = EIO;
 313                 errstr = "Cannot write private key!\n";
 314                 goto out;
 315         }
 316 out:
 317         close(fd);
 318 out_noclose:
 319         xmemset(publickey, 0, sizeof(publickey));
 320         xmemset(secretkey, 0, sizeof(secretkey));
 321
 322         if (err)
 323                 panic("%s: %s", errstr, strerror(errno));
 324         else
 325                 printf("Private key written to %s!\n", path);
 326 }
 327
 328 static void check_config_keypair_or_die(char *home)
 329 {
 330         int fd, err;
 331         ssize_t ret;
 332         const char * errstr = NULL;
 333         unsigned char publickey[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 334         unsigned char publicres[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 335         unsigned char secretkey[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES];
 336         char path[PATH_MAX];
 337
 338         memset(path, 0, sizeof(path));
 339         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 340
 341         fd = open(path, O_RDONLY);
 342         if (fd < 0) {
 343                 err = EIO;
 344                 errstr = "Cannot open privkey file!\n";
 345                 goto out;
 346         }
 347
 348         ret = read(fd, secretkey, sizeof(secretkey));
 349         if (ret != sizeof(secretkey)) {
 350                 err = EIO;
 351                 errstr = "Cannot read private key!\n";
 352                 goto out;
 353         }
 354
 355         close(fd);
 356
 357         memset(path, 0, sizeof(path));
 358         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 359
 360         fd = open(path, O_RDONLY);
 361         if (fd < 0) {
 362                 err = EIO;
 363                 errstr = "Cannot open pubkey file!\n";
 364                 goto out;
 365         }
 366
 367         ret = read(fd, publickey, sizeof(publickey));
 368         if (ret != sizeof(publickey)) {
 369                 err = EIO;
 370                 errstr = "Cannot read public key!\n";
 371                 goto out;
 372         }
 373
 374         crypto_scalarmult_curve25519_base(publicres, secretkey);
 375
 376         err = crypto_verify_32(publicres, publickey);
 377         if (err) {
 378                 err = EINVAL;
 379                 errstr = "WARNING: your keypair is corrupted!!! You need to "
 380                          "generate new keys!!!\n";
 381                 goto out;
 382         }
 383 out:
 384         close(fd);
 385
 386         xmemset(publickey, 0, sizeof(publickey));
 387         xmemset(publicres, 0, sizeof(publicres));
 388         xmemset(secretkey, 0, sizeof(secretkey));
 389
 390         if (err)
 391                 panic("%s: %s\n", errstr, strerror(errno));
 392 }
 393
 394 static int main_keygen(char *home)
 395 {
 396         create_curvedir(home);
 397         write_username(home);
 398         create_keypair(home);
 399         check_config_keypair_or_die(home);
 400
 401         return 0;
 402 }
 403
 404 static int main_export(char *home)
 405 {
 406         int fd, i;
 407         ssize_t ret;
 408         char path[PATH_MAX], tmp[64];
 409
 410         check_config_exists_or_die(home);
 411         check_config_keypair_or_die(home);
 412
 413         printf("Your exported public information:\n\n");
 414
 415         memset(path, 0, sizeof(path));
 416         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 417
 418         fd = open_or_die(path, O_RDONLY);
 419
 420         while ((ret = read(fd, tmp, sizeof(tmp))) > 0) {
 421                 ret = write(STDOUT_FILENO, tmp, ret);
 422         }
 423
 424         close(fd);
 425
 426         printf(";");
 427
 428         memset(path, 0, sizeof(path));
 429         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 430
 431         fd = open_or_die(path, O_RDONLY);
 432
 433         ret = read(fd, tmp, sizeof(tmp));
 434         if (ret != crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES)
 435                 panic("Cannot read public key!\n");
 436
 437         for (i = 0; i < ret; ++i)
 438                 if (i == ret - 1)
 439                         printf("%02x\n\n", (unsigned char) tmp[i]);
 440                 else
 441                         printf("%02x:", (unsigned char) tmp[i]);
 442
 443         close(fd);
 444         fflush(stdout);
 445
 446         return 0;
 447 }
 448
 449 static int main_dumpc(char *home)
 450 {
 451         check_config_exists_or_die(home);
 452         check_config_keypair_or_die(home);
 453
 454         printf("Your clients:\n\n");
 455
 456         parse_userfile_and_generate_user_store_or_die(home);
 457
 458         dump_user_store();
 459
 460         destroy_user_store();
 461
 462         printf("\n");
 463         die();
 464         return 0;
 465 }
 466
 467 static int main_dumps(char *home)
 468 {
 469         check_config_exists_or_die(home);
 470         check_config_keypair_or_die(home);
 471
 472         printf("Your servers:\n\n");
 473
 474         parse_userfile_and_generate_serv_store_or_die(home);
 475
 476         dump_serv_store();
 477
 478         destroy_serv_store();
 479
 480         printf("\n");
 481         die();
 482         return 0;
 483 }
 484
 485 static void daemonize(const char *lockfile)
 486 {
 487         char pidstr[8];
 488         mode_t lperm = S_IRWXU | S_IRGRP | S_IXGRP; /* 0750 */
 489         int lfp;
 490
 491         if (getppid() == 1)
 492                 return;
 493
 494         if (daemon(0, 1))
 495                 panic("Cannot daemonize: %s", strerror(errno));
 496
 497         to_std_log(&stdout);
 498         to_std_log(&stderr);
 499
 500         umask(lperm);
 501         if (lockfile) {
 502                 lfp = open(lockfile, O_RDWR | O_CREAT | O_EXCL,
 503                            S_IRUSR | S_IWUSR | S_IRGRP);
 504                 if (lfp < 0)
 505                         syslog_panic("Cannot create lockfile at %s! "
 506                                      "curvetun server already running?\n",
 507                                      lockfile);
 508
 509                 slprintf(pidstr, sizeof(pidstr), "%u", getpid());
 510                 if (write(lfp, pidstr, strlen(pidstr)) <= 0)
 511                         syslog_panic("Could not write pid to pidfile %s",
 512                                      lockfile);
 513
 514                 close(lfp);
 515         }
 516 }
 517
 518 static int main_client(char *home, char *dev, char *alias, int daemon)
 519 {
 520         int ret, udp;
 521         char *host, *port;
 522
 523         check_config_exists_or_die(home);
 524         check_config_keypair_or_die(home);
 525
 526         parse_userfile_and_generate_serv_store_or_die(home);
 527
 528         get_serv_store_entry_by_alias(alias, alias ? strlen(alias) + 1 : 0,
 529                                       &host, &port, &udp);
 530         if (!host || !port || udp < 0)
 531                 panic("Did not find alias/entry in configuration!\n");
 532
 533         printf("Using [%s] -> %s:%s via %s as endpoint!\n",
 534                alias ? : "default", host, port, udp ? "udp" : "tcp");
 535         if (daemon)
 536                 daemonize(NULL);
 537
 538         ret = client_main(home, dev, host, port, udp);
 539
 540         destroy_serv_store();
 541
 542         return ret;
 543 }
 544
 545 static int main_server(char *home, char *dev, char *port, int udp,
 546                        int ipv4, int daemon, int log)
 547 {
 548         int ret;
 549
 550         check_config_exists_or_die(home);
 551         check_config_keypair_or_die(home);
 552
 553         if (daemon)
 554                 daemonize(LOCKFILE);
 555
 556         ret = server_main(home, dev, port, udp, ipv4, log);
 557
 558         unlink(LOCKFILE);
 559
 560         return ret;
 561 }
 562
 563 int main(int argc, char **argv)
 564 {
 565         int ret = 0, c, opt_index, udp = 0, ipv4 = -1, daemon = 1, log = 1;
 566         char *port = NULL, *stun = NULL, *dev = NULL, *home = NULL, *alias = NULL;
 567         enum working_mode wmode = MODE_UNKNOW;
 568
 569         setfsuid(getuid());
 570         setfsgid(getgid());
 571
 572         home = fetch_home_dir();
 573
 574         while ((c = getopt_long(argc, argv, short_options, long_options,
 575                &opt_index)) != EOF) {
 576                 switch (c) {
 577                 case 'h':
 578                         help();
 579                         break;
 580                 case 'v':
 581                         version();
 582                         break;
 583                 case 'D':
 584                         daemon = 0;
 585                         break;
 586                 case 'N':
 587                         log = 0;
 588                         break;
 589                 case 'C':
 590                         wmode = MODE_DUMPC;
 591                         break;
 592                 case 'S':
 593                         wmode = MODE_DUMPS;
 594                         break;
 595                 case 'c':
 596                         wmode = MODE_CLIENT;
 597                         if (optarg) {
 598                                 if (*optarg == '=')
 599                                         optarg++;
 600                                 alias = xstrdup(optarg);
 601                         }
 602                         break;
 603                 case 'd':
 604                         dev = xstrdup(optarg);
 605                         break;
 606                 case 'k':
 607                         wmode = MODE_KEYGEN;
 608                         break;
 609                 case '4':
 610                         ipv4 = 1;
 611                         break;
 612                 case '6':
 613                         ipv4 = 0;
 614                         break;
 615                 case 'x':
 616                         wmode = MODE_EXPORT;
 617                         break;
 618                 case 's':
 619                         wmode = MODE_SERVER;
 620                         break;
 621                 case 'u':
 622                         udp = 1;
 623                         break;
 624                 case 't':
 625                         stun = xstrdup(optarg);
 626                         break;
 627                 case 'p':
 628                         port = xstrdup(optarg);
 629                         break;
 630                 case '?':
 631                         switch (optopt) {
 632                         case 't':
 633                         case 'd':
 634                         case 'u':
 635                         case 'p':
 636                                 panic("Option -%c requires an argument!\n",
 637                                       optopt);
 638                         default:
 639                                 if (isprint(optopt))
 640                                         printf("Unknown option character `0x%X\'!\n", optopt);
 641                                 die();
 642                         }
 643                 default:
 644                         break;
 645                 }
 646         }
 647
 648         if (argc < 2)
 649                 help();
 650
 651         register_signal(SIGINT, signal_handler);
 652         register_signal(SIGHUP, signal_handler);
 653         register_signal(SIGTERM, signal_handler);
 654         register_signal(SIGPIPE, signal_handler);
 655
 656         curve25519_selftest();
 657
 658         switch (wmode) {
 659         case MODE_KEYGEN:
 660                 ret = main_keygen(home);
 661                 break;
 662         case MODE_EXPORT:
 663                 ret = main_export(home);
 664                 break;
 665         case MODE_DUMPC:
 666                 ret = main_dumpc(home);
 667                 break;
 668         case MODE_DUMPS:
 669                 ret = main_dumps(home);
 670                 break;
 671         case MODE_CLIENT:
 672                 ret = main_client(home, dev, alias, daemon);
 673                 break;
 674         case MODE_SERVER:
 675                 if (!port)
 676                         panic("No port specified!\n");
 677                 if (stun)
 678                         print_stun_probe(stun, 3478, strtoul(port, NULL, 10));
 679                 ret = main_server(home, dev, port, udp, ipv4, daemon, log);
 680                 break;
 681         default:
 682                 die();
 683         }
 684
 685         free(dev);
 686         free(stun);
 687         free(port);
 688         free(alias);
 689
 690         return ret;
 691 }