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 "xmalloc.h"
  31 #include "curvetun.h"
  32 #include "curve.h"
  33 #include "ct_usermgmt.h"
  34 #include "ct_servmgmt.h"
  35 #include "xio.h"
  36 #include "tprintf.h"
  37 #include "crypto_verify_32.h"
  38 #include "crypto_box_curve25519xsalsa20poly1305.h"
  39 #include "crypto_scalarmult_curve25519.h"
  40 #include "crypto_auth_hmacsha512256.h"
  41
  42 #define CURVETUN_ENTROPY_SOURCE "/dev/random"
  43
  44 extern void print_stun_probe(char *server, uint16_t sport, uint16_t tunport);
  45
  46 enum working_mode {
  47         MODE_UNKNOW,
  48         MODE_KEYGEN,
  49         MODE_EXPORT,
  50         MODE_DUMPC,
  51         MODE_DUMPS,
  52         MODE_CLIENT,
  53         MODE_SERVER,
  54 };
  55
  56 volatile sig_atomic_t sigint = 0;
  57
  58 static const char *short_options = "kxc::svhp:t:d:uCS46DN";
  59 static const struct option long_options[] = {
  60         {"client",      optional_argument,      NULL, 'c'},
  61         {"dev",         required_argument,      NULL, 'd'},
  62         {"port",        required_argument,      NULL, 'p'},
  63         {"stun",        required_argument,      NULL, 't'},
  64         {"keygen",      no_argument,            NULL, 'k'},
  65         {"export",      no_argument,            NULL, 'x'},
  66         {"dumpc",       no_argument,            NULL, 'C'},
  67         {"dumps",       no_argument,            NULL, 'S'},
  68         {"no-logging",  no_argument,            NULL, 'N'},
  69         {"server",      no_argument,            NULL, 's'},
  70         {"udp",         no_argument,            NULL, 'u'},
  71         {"ipv4",        no_argument,            NULL, '4'},
  72         {"ipv6",        no_argument,            NULL, '6'},
  73         {"nofork",      no_argument,            NULL, 'D'},
  74         {"version",     no_argument,            NULL, 'v'},
  75         {"help",        no_argument,            NULL, 'h'},
  76         {NULL, 0, NULL, 0}
  77 };
  78
  79 static void signal_handler(int number)
  80 {
  81         switch (number) {
  82         case SIGINT:
  83         case SIGTERM:
  84                 sigint = 1;
  85                 break;
  86         default:
  87                 break;
  88         }
  89 }
  90
  91 static void help(void)
  92 {
  93         printf("\ncurvetun %s, lightweight curve25519-based VPN/IP tunnel\n", VERSION_STRING);
  94         puts("http://www.netsniff-ng.org\n\n"
  95              "Usage: curvetun [options]\n"
  96              "Options, general:\n"
  97              "  -d|--dev <tun>          Networking tunnel device, e.g. tun0\n"
  98              "  -p|--port <num>         Server port number (mandatory)\n"
  99              "  -t|--stun <server>      Show public IP/Port mapping via STUN\n"
 100              "  -c|--client[=alias]     Client mode, server alias optional\n"
 101              "  -k|--keygen             Generate public/private keypair\n"
 102              "  -x|--export             Export your public data for remote servers\n"
 103              "  -C|--dumpc              Dump parsed clients\n"
 104              "  -S|--dumps              Dump parsed servers\n"
 105              "  -D|--nofork             Do not daemonize\n"
 106              "  -s|--server             Server mode, options follow below\n"
 107              "  -N|--no-logging         Disable server logging (for better anonymity)\n"
 108              "  -u|--udp                Use UDP as carrier instead of TCP\n"
 109              "  -4|--ipv4               Tunnel devices are IPv4\n"
 110              "  -6|--ipv6               Tunnel devices are IPv6\n"
 111              "  -v|--version            Print version\n"
 112              "  -h|--help               Print this help\n\n"
 113              "Example:\n"
 114              "  See Documentation/Curvetun for a configuration example.\n"
 115              "  curvetun --server -4 -u -N --port 6666 --stun stunserver.org\n"
 116              "  curvetun --client=ethz\n\n"
 117              "  curvetun --keygen\n"
 118              "  curvetun --export\n"
 119              "Note:\n"
 120              "  There is no default port specified, so that you are forced\n"
 121              "  to select your own! For client/server status messages see syslog!\n"
 122              "  This software is an experimental prototype intended for researchers.\n\n"
 123              "Secret ingredient: 7647-14-5\n\n"
 124              "Please report bugs to <bugs@netsniff-ng.org>\n"
 125              "Copyright (C) 2011-2013 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
 126              "Swiss federal institute of technology (ETH Zurich)\n"
 127              "License: GNU GPL version 2.0\n"
 128              "This is free software: you are free to change and redistribute it.\n"
 129              "There is NO WARRANTY, to the extent permitted by law.\n");
 130         die();
 131 }
 132
 133 static void version(void)
 134 {
 135         printf("\ncurvetun %s, lightweight curve25519-based VPN/IP tunnel\n", VERSION_STRING);
 136         puts("http://www.netsniff-ng.org\n\n"
 137              "Please report bugs to <bugs@netsniff-ng.org>\n"
 138              "Copyright (C) 2011-2013 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
 139              "Swiss federal institute of technology (ETH Zurich)\n"
 140              "License: GNU GPL version 2.0\n"
 141              "This is free software: you are free to change and redistribute it.\n"
 142              "There is NO WARRANTY, to the extent permitted by law.\n");
 143         die();
 144 }
 145
 146 static void check_file_or_die(char *home, char *file, int maybeempty)
 147 {
 148         char path[PATH_MAX];
 149         struct stat st;
 150
 151         memset(path, 0, sizeof(path));
 152         slprintf(path, sizeof(path), "%s/%s", home, file);
 153
 154         if (stat(path, &st))
 155                 panic("No such file %s! Type --help for further information\n",
 156                       path);
 157
 158         if (!S_ISREG(st.st_mode))
 159                 panic("%s is not a regular file!\n", path);
 160
 161         if ((st.st_mode & ~S_IFREG) != (S_IRUSR | S_IWUSR))
 162                 panic("You have set too many permissions on %s (%o)!\n",
 163                       path, st.st_mode);
 164
 165         if (maybeempty == 0 && st.st_size == 0)
 166                 panic("%s is empty!\n", path);
 167 }
 168
 169 static void check_config_exists_or_die(char *home)
 170 {
 171         if (!home)
 172                 panic("No home dir specified!\n");
 173
 174         check_file_or_die(home, FILE_CLIENTS, 1);
 175         check_file_or_die(home, FILE_SERVERS, 1);
 176         check_file_or_die(home, FILE_PRIVKEY, 0);
 177         check_file_or_die(home, FILE_PUBKEY, 0);
 178         check_file_or_die(home, FILE_USERNAM, 0);
 179 }
 180
 181 static char *fetch_home_dir(void)
 182 {
 183         char *home = getenv("HOME");
 184         if (!home)
 185                 panic("No HOME defined!\n");
 186         return home;
 187 }
 188
 189 static void write_username(char *home)
 190 {
 191         int fd, ret;
 192         char path[PATH_MAX];
 193         char user[512];
 194
 195         memset(path, 0, sizeof(path));
 196         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 197
 198         printf("Username: [%s] ", getenv("USER"));
 199         fflush(stdout);
 200
 201         memset(user, 0, sizeof(user));
 202         if (fgets(user, sizeof(user), stdin) == NULL)
 203                 panic("Could not read from stdin!\n");
 204         user[sizeof(user) - 1] = 0;
 205         user[strlen(user) - 1] = 0; /* omit last \n */
 206         if (strlen(user) == 0)
 207                 strlcpy(user, getenv("USER"), sizeof(user));
 208
 209         fd = open_or_die_m(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 210
 211         ret = write(fd, user, strlen(user));
 212         if (ret != strlen(user))
 213                 panic("Could not write username!\n");
 214
 215         close(fd);
 216
 217         printf("Username written to %s!\n", path);
 218 }
 219
 220 static void create_curvedir(char *home)
 221 {
 222         int ret;
 223         char path[PATH_MAX];
 224
 225         memset(path, 0, sizeof(path));
 226         slprintf(path, sizeof(path), "%s/%s", home, ".curvetun/");
 227
 228         errno = 0;
 229
 230         ret = mkdir(path, S_IRWXU);
 231         if (ret < 0 && errno != EEXIST)
 232                 panic("Cannot create curvetun dir!\n");
 233
 234         printf("curvetun directory %s created!\n", path);
 235         /* We also create empty files for clients and servers! */
 236
 237         memset(path, 0, sizeof(path));
 238         slprintf(path, sizeof(path), "%s/%s", home, FILE_CLIENTS);
 239
 240         create_or_die(path, S_IRUSR | S_IWUSR);
 241
 242         printf("Empty client file written to %s!\n", path);
 243
 244         memset(path, 0, sizeof(path));
 245         slprintf(path, sizeof(path), "%s/%s", home, FILE_SERVERS);
 246
 247         create_or_die(path, S_IRUSR | S_IWUSR);
 248
 249         printf("Empty server file written to %s!\n", path);
 250 }
 251
 252 static void create_keypair(char *home)
 253 {
 254         int fd, err = 0;
 255         ssize_t ret;
 256         unsigned char publickey[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES] = { 0 };
 257         unsigned char secretkey[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES] = { 0 };
 258         char path[PATH_MAX];
 259         const char * errstr = NULL;
 260
 261         printf("Reading from %s (this may take a while) ...\n", CURVETUN_ENTROPY_SOURCE);
 262
 263         fd = open_or_die(CURVETUN_ENTROPY_SOURCE, O_RDONLY);
 264
 265         ret = read_exact(fd, secretkey, sizeof(secretkey), 0);
 266         if (ret != sizeof(secretkey)) {
 267                 err = EIO;
 268                 errstr = "Cannot read from "CURVETUN_ENTROPY_SOURCE"!\n";
 269                 goto out;
 270         }
 271
 272         close(fd);
 273
 274         crypto_scalarmult_curve25519_base(publickey, secretkey);
 275
 276         memset(path, 0, sizeof(path));
 277         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 278
 279         fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 280         if (fd < 0) {
 281                 err = EIO;
 282                 errstr = "Cannot open pubkey file!\n";
 283                 goto out_noclose;
 284         }
 285
 286         ret = write(fd, publickey, sizeof(publickey));
 287         if (ret != sizeof(publickey)) {
 288                 err = EIO;
 289                 errstr = "Cannot write public key!\n";
 290                 goto out;
 291         }
 292
 293         close(fd);
 294
 295         printf("Public key written to %s!\n", path);
 296
 297         memset(path, 0, sizeof(path));
 298         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 299
 300         fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 301         if (fd < 0) {
 302                 err = EIO;
 303                 errstr = "Cannot open privkey file!\n";
 304                 goto out_noclose;
 305         }
 306
 307         ret = write(fd, secretkey, sizeof(secretkey));
 308         if (ret != sizeof(secretkey)) {
 309                 err = EIO;
 310                 errstr = "Cannot write private key!\n";
 311                 goto out;
 312         }
 313 out:
 314         close(fd);
 315 out_noclose:
 316         xmemset(publickey, 0, sizeof(publickey));
 317         xmemset(secretkey, 0, sizeof(secretkey));
 318
 319         if (err)
 320                 panic("%s: %s", errstr, strerror(errno));
 321         else
 322                 printf("Private key written to %s!\n", path);
 323 }
 324
 325 static void check_config_keypair_or_die(char *home)
 326 {
 327         int fd, err;
 328         ssize_t ret;
 329         const char * errstr = NULL;
 330         unsigned char publickey[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 331         unsigned char publicres[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 332         unsigned char secretkey[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES];
 333         char path[PATH_MAX];
 334
 335         memset(path, 0, sizeof(path));
 336         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 337
 338         fd = open(path, O_RDONLY);
 339         if (fd < 0) {
 340                 err = EIO;
 341                 errstr = "Cannot open privkey file!\n";
 342                 goto out;
 343         }
 344
 345         ret = read(fd, secretkey, sizeof(secretkey));
 346         if (ret != sizeof(secretkey)) {
 347                 err = EIO;
 348                 errstr = "Cannot read private key!\n";
 349                 goto out;
 350         }
 351
 352         close(fd);
 353
 354         memset(path, 0, sizeof(path));
 355         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 356
 357         fd = open(path, O_RDONLY);
 358         if (fd < 0) {
 359                 err = EIO;
 360                 errstr = "Cannot open pubkey file!\n";
 361                 goto out;
 362         }
 363
 364         ret = read(fd, publickey, sizeof(publickey));
 365         if (ret != sizeof(publickey)) {
 366                 err = EIO;
 367                 errstr = "Cannot read public key!\n";
 368                 goto out;
 369         }
 370
 371         crypto_scalarmult_curve25519_base(publicres, secretkey);
 372
 373         err = crypto_verify_32(publicres, publickey);
 374         if (err) {
 375                 err = EINVAL;
 376                 errstr = "WARNING: your keypair is corrupted!!! You need to "
 377                          "generate new keys!!!\n";
 378                 goto out;
 379         }
 380 out:
 381         close(fd);
 382
 383         xmemset(publickey, 0, sizeof(publickey));
 384         xmemset(publicres, 0, sizeof(publicres));
 385         xmemset(secretkey, 0, sizeof(secretkey));
 386
 387         if (err)
 388                 panic("%s: %s\n", errstr, strerror(errno));
 389 }
 390
 391 static int main_keygen(char *home)
 392 {
 393         create_curvedir(home);
 394         write_username(home);
 395         create_keypair(home);
 396         check_config_keypair_or_die(home);
 397
 398         return 0;
 399 }
 400
 401 static int main_export(char *home)
 402 {
 403         int fd, i;
 404         ssize_t ret;
 405         char path[PATH_MAX], tmp[64];
 406
 407         check_config_exists_or_die(home);
 408         check_config_keypair_or_die(home);
 409
 410         printf("Your exported public information:\n\n");
 411
 412         memset(path, 0, sizeof(path));
 413         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 414
 415         fd = open_or_die(path, O_RDONLY);
 416
 417         while ((ret = read(fd, tmp, sizeof(tmp))) > 0) {
 418                 ret = write(STDOUT_FILENO, tmp, ret);
 419         }
 420
 421         close(fd);
 422
 423         printf(";");
 424
 425         memset(path, 0, sizeof(path));
 426         slprintf(path, sizeof(path), "%s/%s", home, FILE_PUBKEY);
 427
 428         fd = open_or_die(path, O_RDONLY);
 429
 430         ret = read(fd, tmp, sizeof(tmp));
 431         if (ret != crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES)
 432                 panic("Cannot read public key!\n");
 433
 434         for (i = 0; i < ret; ++i)
 435                 if (i == ret - 1)
 436                         printf("%02x\n\n", (unsigned char) tmp[i]);
 437                 else
 438                         printf("%02x:", (unsigned char) tmp[i]);
 439
 440         close(fd);
 441         fflush(stdout);
 442
 443         return 0;
 444 }
 445
 446 static int main_dumpc(char *home)
 447 {
 448         check_config_exists_or_die(home);
 449         check_config_keypair_or_die(home);
 450
 451         printf("Your clients:\n\n");
 452
 453         parse_userfile_and_generate_user_store_or_die(home);
 454
 455         dump_user_store();
 456
 457         destroy_user_store();
 458
 459         printf("\n");
 460         die();
 461         return 0;
 462 }
 463
 464 static int main_dumps(char *home)
 465 {
 466         check_config_exists_or_die(home);
 467         check_config_keypair_or_die(home);
 468
 469         printf("Your servers:\n\n");
 470
 471         parse_userfile_and_generate_serv_store_or_die(home);
 472
 473         dump_serv_store();
 474
 475         destroy_serv_store();
 476
 477         printf("\n");
 478         die();
 479         return 0;
 480 }
 481
 482 static void daemonize(const char *lockfile)
 483 {
 484         char pidstr[8];
 485         mode_t lperm = S_IRWXU | S_IRGRP | S_IXGRP; /* 0750 */
 486         int lfp;
 487
 488         if (getppid() == 1)
 489                 return;
 490
 491         if (daemon(0, 1))
 492                 panic("Cannot daemonize: %s", strerror(errno));
 493
 494         to_std_log(&stdout);
 495         to_std_log(&stderr);
 496
 497         umask(lperm);
 498         if (lockfile) {
 499                 lfp = open(lockfile, O_RDWR | O_CREAT | O_EXCL,
 500                            S_IRUSR | S_IWUSR | S_IRGRP);
 501                 if (lfp < 0)
 502                         syslog_panic("Cannot create lockfile at %s! "
 503                                      "curvetun server already running?\n",
 504                                      lockfile);
 505
 506                 slprintf(pidstr, sizeof(pidstr), "%u", getpid());
 507                 if (write(lfp, pidstr, strlen(pidstr)) <= 0)
 508                         syslog_panic("Could not write pid to pidfile %s",
 509                                      lockfile);
 510
 511                 close(lfp);
 512         }
 513 }
 514
 515 static int main_client(char *home, char *dev, char *alias, int daemon)
 516 {
 517         int ret, udp;
 518         char *host, *port;
 519
 520         check_config_exists_or_die(home);
 521         check_config_keypair_or_die(home);
 522
 523         parse_userfile_and_generate_serv_store_or_die(home);
 524
 525         get_serv_store_entry_by_alias(alias, alias ? strlen(alias) + 1 : 0,
 526                                       &host, &port, &udp);
 527         if (!host || !port || udp < 0)
 528                 panic("Did not find alias/entry in configuration!\n");
 529
 530         printf("Using [%s] -> %s:%s via %s as endpoint!\n",
 531                alias ? : "default", host, port, udp ? "udp" : "tcp");
 532         if (daemon)
 533                 daemonize(NULL);
 534
 535         ret = client_main(home, dev, host, port, udp);
 536
 537         destroy_serv_store();
 538
 539         return ret;
 540 }
 541
 542 static int main_server(char *home, char *dev, char *port, int udp,
 543                        int ipv4, int daemon, int log)
 544 {
 545         int ret;
 546
 547         check_config_exists_or_die(home);
 548         check_config_keypair_or_die(home);
 549
 550         if (daemon)
 551                 daemonize(LOCKFILE);
 552
 553         ret = server_main(home, dev, port, udp, ipv4, log);
 554
 555         unlink(LOCKFILE);
 556
 557         return ret;
 558 }
 559
 560 int main(int argc, char **argv)
 561 {
 562         int ret = 0, c, opt_index, udp = 0, ipv4 = -1, daemon = 1, log = 1;
 563         char *port = NULL, *stun = NULL, *dev = NULL, *home = NULL, *alias = NULL;
 564         enum working_mode wmode = MODE_UNKNOW;
 565
 566         setfsuid(getuid());
 567         setfsgid(getgid());
 568
 569         home = fetch_home_dir();
 570
 571         while ((c = getopt_long(argc, argv, short_options, long_options,
 572                &opt_index)) != EOF) {
 573                 switch (c) {
 574                 case 'h':
 575                         help();
 576                         break;
 577                 case 'v':
 578                         version();
 579                         break;
 580                 case 'D':
 581                         daemon = 0;
 582                         break;
 583                 case 'N':
 584                         log = 0;
 585                         break;
 586                 case 'C':
 587                         wmode = MODE_DUMPC;
 588                         break;
 589                 case 'S':
 590                         wmode = MODE_DUMPS;
 591                         break;
 592                 case 'c':
 593                         wmode = MODE_CLIENT;
 594                         if (optarg) {
 595                                 if (*optarg == '=')
 596                                         optarg++;
 597                                 alias = xstrdup(optarg);
 598                         }
 599                         break;
 600                 case 'd':
 601                         dev = xstrdup(optarg);
 602                         break;
 603                 case 'k':
 604                         wmode = MODE_KEYGEN;
 605                         break;
 606                 case '4':
 607                         ipv4 = 1;
 608                         break;
 609                 case '6':
 610                         ipv4 = 0;
 611                         break;
 612                 case 'x':
 613                         wmode = MODE_EXPORT;
 614                         break;
 615                 case 's':
 616                         wmode = MODE_SERVER;
 617                         break;
 618                 case 'u':
 619                         udp = 1;
 620                         break;
 621                 case 't':
 622                         stun = xstrdup(optarg);
 623                         break;
 624                 case 'p':
 625                         port = xstrdup(optarg);
 626                         break;
 627                 case '?':
 628                         switch (optopt) {
 629                         case 't':
 630                         case 'd':
 631                         case 'u':
 632                         case 'p':
 633                                 panic("Option -%c requires an argument!\n",
 634                                       optopt);
 635                         default:
 636                                 if (isprint(optopt))
 637                                         printf("Unknown option character `0x%X\'!\n", optopt);
 638                                 die();
 639                         }
 640                 default:
 641                         break;
 642                 }
 643         }
 644
 645         if (argc < 2)
 646                 help();
 647
 648         register_signal(SIGINT, signal_handler);
 649         register_signal(SIGHUP, signal_handler);
 650         register_signal(SIGTERM, signal_handler);
 651         register_signal(SIGPIPE, signal_handler);
 652
 653         curve25519_selftest();
 654
 655         switch (wmode) {
 656         case MODE_KEYGEN:
 657                 ret = main_keygen(home);
 658                 break;
 659         case MODE_EXPORT:
 660                 ret = main_export(home);
 661                 break;
 662         case MODE_DUMPC:
 663                 ret = main_dumpc(home);
 664                 break;
 665         case MODE_DUMPS:
 666                 ret = main_dumps(home);
 667                 break;
 668         case MODE_CLIENT:
 669                 ret = main_client(home, dev, alias, daemon);
 670                 break;
 671         case MODE_SERVER:
 672                 if (!port)
 673                         panic("No port specified!\n");
 674                 if (stun)
 675                         print_stun_probe(stun, 3478, strtoul(port, NULL, 10));
 676                 ret = main_server(home, dev, port, udp, ipv4, daemon, log);
 677                 break;
 678         default:
 679                 die();
 680         }
 681
 682         if (dev)
 683                 xfree(dev);
 684         if (stun)
 685                 xfree(stun);
 686         if (port)
 687                 xfree(port);
 688         if (alias)
 689                 xfree(alias);
 690
 691         return ret;
 692 }