tiptunnel.c 11.5 KB
Newer Older
Chad Barb's avatar
Chad Barb committed
1 2 3 4 5 6 7 8 9 10
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

Chad Barb's avatar
 
Chad Barb committed
11 12
#ifdef WITHSSL
#include <openssl/ssl.h>
Chad Barb's avatar
 
Chad Barb committed
13
#include <openssl/err.h>
Chad Barb's avatar
 
Chad Barb committed
14
#endif /* WITHSSL */
Chad Barb's avatar
Chad Barb committed
15 16 17

#include "capdecls.h"

18 19 20

#define DEFAULT_PROGRAM "xterm -T TIP -e telnet %s %s"

Chad Barb's avatar
Chad Barb committed
21 22 23 24 25 26 27 28 29 30 31 32 33 34
int debug = 0;
int allowRemote = 0;

unsigned short port = 0;
int sock = 0;

unsigned short tunnelPort = 0;
int tunnelSock = 0;

char * programToLaunch = NULL;
char * hostname = NULL;

secretkey_t key;

Chad Barb's avatar
 
Chad Barb committed
35 36 37 38 39 40
typedef int WriteFunc( void * data, int size );
typedef int ReadFunc( void * data, int size );

WriteFunc * writeFunc;
ReadFunc  * readFunc;

Chad Barb's avatar
Chad Barb committed
41 42 43 44 45 46 47
void usage();
void loadAcl( const char * filename );
void doConnect();
void doAuthenticate();
void doCreateTunnel();
void doTunnelConnection();

Chad Barb's avatar
 
Chad Barb committed
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
int writeNormal( void * data, int size );
int readNormal( void * data, int size );

#ifdef WITHSSL

void initSSL();
void sslConnect();

int writeSSL( void * data, int size );
int readSSL( void * data, int size );

SSL * ssl;
SSL_CTX * ctx;

int usingSSL = 0;
char * certString = NULL;

#endif /* WITHSSL */
Chad Barb's avatar
Chad Barb committed
66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93

int main( int argc, char ** argv )
{
  int op;

  while ((op = getopt( argc, argv, "sp:rd" )) != -1) {
    switch (op) {
      case 'p':
        tunnelPort = atoi( optarg );
	break;
      case 'd':
	debug++;
	break;
      case 'r':
	allowRemote++;
	break;
    }
  }

  argc -= optind;
  argv += optind;

  if (argc < 1) {
    usage();
  }

  if (argc > 1) {
    programToLaunch = strdup( argv[1] );    
94 95
  } else {
    programToLaunch = DEFAULT_PROGRAM;
Chad Barb's avatar
Chad Barb committed
96 97 98 99
  }

  loadAcl( argv[0] );

Chad Barb's avatar
 
Chad Barb committed
100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115
#ifdef WITHSSL
  if (usingSSL) { 
    writeFunc = writeSSL;
    readFunc  = readSSL;
    initSSL();
    doConnect();
    sslConnect();
  } else
#endif /* WITHSSL */
  {
    /* either there is no SSL, or they're not using it. */
    writeFunc = writeNormal;
    readFunc  = readNormal;
    doConnect();
  }

Chad Barb's avatar
Chad Barb committed
116 117
  doAuthenticate();
  doCreateTunnel();
Chad Barb's avatar
 
Chad Barb committed
118

Chad Barb's avatar
Chad Barb committed
119 120
  if (programToLaunch) {
    char portString[12];
121 122 123
    char runString[1024];
    char * foo;

Chad Barb's avatar
Chad Barb committed
124
    sprintf( portString, "%i", tunnelPort );
125 126 127

    /*
      if (debug) printf("Launching %s with args localhost, %s.\n",
Chad Barb's avatar
Chad Barb committed
128
		      programToLaunch, portString );
129 130 131 132 133 134 135 136 137 138
    */

    sprintf(runString, programToLaunch, "localhost", portString);
    for (foo = runString; *foo; foo++);
    foo[0] = ' ';
    foo[1] = '&';
    foo[2] = '\0';
    if (debug) printf("Running '%s'\n", runString);
    system( runString );
    /*
Chad Barb's avatar
Chad Barb committed
139 140 141 142
    if (!fork()) {
      execlp( programToLaunch, 
	      programToLaunch, "localhost", portString, NULL );
    }
143
    */
Chad Barb's avatar
Chad Barb committed
144 145 146 147 148 149 150 151 152 153 154 155 156
  }
  doTunnelConnection();
  if (debug) { printf("tiptunnel closing.\n"); }
}

void usage()
{
  printf("Usage:\n"
	 "tiptunnel [-p <portnum>] [-d] [-r] aclfile [program]\n"
	 "-p <portnum>     specifies tunnel port number\n"
	 "-d               turns on more verbose messages\n"
	 "-r               allows connections to tunnel from non-localhost\n"
	 "\n"
157 158 159
	 "[program]        path of program to launch; default is\n"
	 "                 \"%s\"\n",
         DEFAULT_PROGRAM
Chad Barb's avatar
 
Chad Barb committed
160
	 //"-k keeps accepting connections until killed"
Chad Barb's avatar
Chad Barb committed
161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189
	 );
  exit(-1);
}

void loadAcl( const char * filename )
{
  FILE * aclFile = fopen( filename, "r" );
  char b1[256];
  char b2[256];

  if (!aclFile) {
    perror("open");
    fprintf( stderr, "Error opening ACL file '%s'\n", filename );
    exit(-1);
  }

  if (debug) { printf("Opened ACL file '%s'\n", filename ); }
  
  bzero( &key, sizeof( key ) );

  while (fscanf(aclFile, "%s %s\n", &b1, &b2) != EOF) {
    if ( strcmp(b1, "host:") == 0 ) {
      hostname = strdup( b2 );
    } else if ( strcmp(b1, "port:") == 0 ) {
      port = atoi( b2 );
    } else if ( strcmp(b1, "keylen:") == 0 ) {
      key.keylen = atoi( b2 );
    } else if ( strcmp(b1, "key:") == 0 ) {
      strcpy( key.key, b2 );
Chad Barb's avatar
 
Chad Barb committed
190 191 192 193 194 195
#ifdef WITHSSL
    } else if ( strcmp(b1, "ssl-server-cert:") == 0 ) {
      if (debug) { printf("Using SSL to connect to capture.\n"); }
      certString = strdup( b2 );
      usingSSL++;
#endif /* WITHSSL */
Chad Barb's avatar
Chad Barb committed
196 197 198 199 200 201 202 203 204 205 206 207
    } else {
      fprintf(stderr, "Ignored unknown ACL: %s %s\n", b1, b2);
    }
  }

  if (!port || !hostname || !key.keylen || !strlen(key.key)) {
    fprintf(stderr, "Incomplete ACL\n");
    exit(-1);
  }

}

Chad Barb's avatar
 
Chad Barb committed
208 209 210 211 212 213 214 215 216 217
int writeNormal( void * data, int size )
{
  return write( sock, data, size );
}

int readNormal( void * data, int size )
{
  return read( sock, data, size );
}

Chad Barb's avatar
Chad Barb committed
218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250
void doConnect()
{
  struct sockaddr_in name;
  struct hostent *he;

  name.sin_family = AF_INET;
  name.sin_port   = htons(port);

  he = gethostbyname(hostname);   
  if (!he) {
    fprintf(stderr, "Unknown hostname %s: %s\n",
	    hostname, hstrerror(h_errno));
    exit(-1);
  }
  
  memcpy ((char *)&name.sin_addr, he->h_addr, he->h_length);
  sock = socket(AF_INET, SOCK_STREAM, 0);
  if (sock < 0) {
    perror("socket");
    exit(-1);
  }

  if (connect( sock, (struct sockaddr *)&name, sizeof(name)) < 0) {
    close( sock );
    perror("connect");
    exit(-1);
  }
}
  
void doAuthenticate()
{
  capret_t capret;

Chad Barb's avatar
 
Chad Barb committed
251 252 253 254
  if ( writeFunc( /*sock,*/ &key, sizeof(key) ) == sizeof(key) &&
       readFunc( /*sock,*/ &capret, sizeof(capret)) > 0 ) {
    switch( capret ) {
    case CAPOK: 
Chad Barb's avatar
Chad Barb committed
255
      return;
Chad Barb's avatar
 
Chad Barb committed
256
    case CAPBUSY:       
Chad Barb's avatar
Chad Barb committed
257
      fprintf(stderr, "Tip line busy.\n");
Chad Barb's avatar
 
Chad Barb committed
258 259 260 261 262 263 264
      break;
    case CAPNOPERM:
      fprintf(stderr, "You do not have permission. No TIP for you!\n");
      break;
    default:
      fprintf(stderr, "Unknown return code 0x%02x.\n", (unsigned int)capret);
      return; // XXX Final version should break here. 
Chad Barb's avatar
Chad Barb committed
265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319
    }
  } else {
    // write or read hosed.
    fprintf(stderr, "Error authenticating\n");
  }

  close( sock );
  exit(-1);
}


void doCreateTunnel()
{
  int i;
  struct sockaddr_in name;

  tunnelSock = socket(AF_INET, SOCK_STREAM, 0);
  if (tunnelSock < 0) { 
    perror("socket");
    exit(-1);
  }

  i = 1;
  if (setsockopt(tunnelSock, SOL_SOCKET, SO_REUSEADDR,
		 (char *)&i, sizeof(i)) < 0) {
    perror("setsockopt: SO_REUSEADDR");
    exit(-1);
  }

  name.sin_family = AF_INET;
  name.sin_addr.s_addr = INADDR_ANY;
  name.sin_port = htons( tunnelPort );
  if (bind(tunnelSock, (struct sockaddr *) &name, sizeof(name))) {
    perror("bind");
    exit(-1);
  }

  i = sizeof(name);
  if (getsockname(tunnelSock, (struct sockaddr *)&name, &i)) {
    perror("getsockname");
    exit(-1);
  }

  tunnelPort = ntohs(name.sin_port);

  printf("Listening on port %i.\n", tunnelPort);

  if (listen(tunnelSock, 1) < 0) {
    perror("listen");
    exit(-1);
  }
}

void doTunnelConnection()
{
Chad Barb's avatar
 
Chad Barb committed
320
  int i;
Chad Barb's avatar
Chad Barb committed
321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348
  int conSock;
  struct sockaddr_in name;
  socklen_t namelen = sizeof( name );

acceptor:
  conSock = accept( tunnelSock, (struct sockaddr *)&name, &namelen );

  if (name.sin_family != AF_INET) {
    fprintf(stderr,"Error: non AF_INET connection.\n");
    exit(-1);
  }

  if (!allowRemote && 
      ntohl( name.sin_addr.s_addr ) != INADDR_LOOPBACK) {
    const char reject[] = 
      "Connection attempted from non-local machine (ignored.)\n"
      "Use -r switch to allow non-local connections.\n";
    write( conSock, reject, sizeof( reject ) );
    fprintf( stderr, "%s", reject );
    close( conSock );
    goto acceptor;
  }

  if (conSock < 0 ) {
    perror("accept");
    exit(-1);
  }

Chad Barb's avatar
 
Chad Barb committed
349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372
  { 
    /*
      lets pretend that we are a telnetd (RFC854).. 
      It will be crackling good fun! 

      we enable "SUPPRESS GO AHEAD" and "ECHO",
      thus (through something commonly called "kludge line mode")
      telling the client _not_ to send a line at a time (and not to echo locally.) 

      I'm actually not totally sure why this works, but I'm afraid if I 
      think too hard about it, it will stop.
    */

    const char telnet_commands[] = 
    { 
      // IAC WILL SUPPRESS GO AHEAD:
      255, 251, 3,
      // IAC WILL ECHO:
      255, 251, 1   
    };

    write( conSock, telnet_commands, sizeof( telnet_commands ) );
  }

Chad Barb's avatar
Chad Barb committed
373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393
  while (1) {
    fd_set fds;
    char buf[4096];
    
    FD_ZERO( &fds );
    FD_SET( conSock, &fds );
    FD_SET( sock, &fds );
    
    if (select( MAX( conSock, sock ) + 1, &fds, NULL, NULL, NULL ) < 0) {
      perror("select");
      exit(-1);
    }

    if ( FD_ISSET( conSock, &fds ) ) {
      int got = read( conSock, buf, 4096);
      if (got <= 0) {
	if (got < 0) { perror("read conSock"); }
	if (debug) { printf("conSock read %i; exiting.\n", got); }
	return;
      }

Chad Barb's avatar
 
Chad Barb committed
394 395 396 397 398 399 400 401
      /*  
	  we could implement some kind of search to remove 
	  "IAC DO SUPPRESS GO AHEAD" and "IAC DO ECHO" bytes from the stream,
	  or just trash any packet starting in "IAC" (255).
	  Yeah.
      */

      if ((unsigned char)buf[0] != 255) {
402 403 404 405 406 407 408 409 410 411 412 413 414 415

	if (buf[got - 1] == '\0') { got--; }

	/*
	for(i = 0; i < got; i++ ) {
	  if ((unsigned char)buf[i] > 127 || 
	      (unsigned char)buf[i] < 32) {
	    printf("Special to server %i\n", 
		   (unsigned int)(unsigned char)buf[i] );
	    //buf[i] = '#';
	  }
	}
	*/

Chad Barb's avatar
 
Chad Barb committed
416 417 418 419
	if (writeFunc( /*sock,*/ buf, got ) < 0) {
	  perror("write sock");
	  return;
	}
420
      } 
Chad Barb's avatar
Chad Barb committed
421 422 423
    }

    if ( FD_ISSET( sock, &fds ) ) {
Chad Barb's avatar
 
Chad Barb committed
424
      int got = readFunc( /*sock,*/ buf, 4096);
Chad Barb's avatar
Chad Barb committed
425 426 427 428 429 430
      if (got <= 0) {
	if (got < 0) { perror("read sock"); }
	if (debug) { printf("sock read %i; exiting.\n", got); }
	return;
      }

431
      //printf("%i server->consock\n", got );
Chad Barb's avatar
 
Chad Barb committed
432

433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448
      if ((unsigned char)buf[0] != 255) {
	/*
	for(i = 0; i < got; i++ ) {
	  if (buf[i] == '^') { buf[i] = '!'; }
	  if ((unsigned char)buf[i] > 127 || 
	      (unsigned char)buf[i] < 32) {
	    printf("Special from server %i\n", 
		   (unsigned int)(unsigned char)buf[i] );
	    //buf[i] = '#';
	  }
	}
	*/
	if (write( conSock, buf, got ) < 0) {
	  perror("write conSock");
	  return;
	}
Chad Barb's avatar
Chad Barb committed
449 450 451 452
      }
    }
  }
}
Chad Barb's avatar
 
Chad Barb committed
453 454 455 456 457 458 459 460


#ifdef WITHSSL

void initSSL()
{
  SSL_library_init();
  ctx = SSL_CTX_new( SSLv23_method() );
Chad Barb's avatar
 
Chad Barb committed
461
  SSL_load_error_strings();
Chad Barb's avatar
 
Chad Barb committed
462 463 464 465 466 467 468 469 470 471 472 473
  
  //  if (!(SSL_CTX_load_verify_location( ctx, CA_LIST, 0 ))
}

void sslConnect()
{
  unsigned char digest[256];
  unsigned int len = sizeof( digest );
  unsigned char digestHex[512];
  X509 * peer;
  BIO * sbio;
  int i;
Chad Barb's avatar
 
Chad Barb committed
474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490
  
  // inform server of desire to use SSL
  {
    secretkey_t sslHintKey;
    char ret[4];

    sslHintKey.keylen = 7;
    strncpy( sslHintKey.key, "USESSL", 7 );
    write( sock, &sslHintKey, sizeof( sslHintKey ) );
    /*
    if (4 != read( sock, ret, 4 ) || 
	0 != strncmp( ret, "OKAY", 4) ) {
      fprintf( stderr, "Didnt get SSL OKAY from server.\n");
      exit(-1);
    }
    */
  } 
Chad Barb's avatar
 
Chad Barb committed
491 492 493 494

  ssl = SSL_new( ctx );
  SSL_set_fd( ssl, sock );

Chad Barb's avatar
 
Chad Barb committed
495 496 497 498 499 500 501 502 503 504
  /*
  i = 0;
  while (1) {
    char * n = SSL_get_cipher_list( ssl, i );
    if (!n) { break;}
    printf("Cipher #%i is %s\n", i, n );
    i++;
  }
  */

Chad Barb's avatar
 
Chad Barb committed
505 506
  // sbio = BIO_new_socket( sock, BIO_NOCLOSE );
  // SSL_set_bio( ssl, sbio, sbio );
Chad Barb's avatar
 
Chad Barb committed
507
  sleep(1);
Chad Barb's avatar
 
Chad Barb committed
508 509 510
  
  if (SSL_connect( ssl ) <= 0) {
    fprintf(stderr, "SSL Connect error.\n");
Chad Barb's avatar
 
Chad Barb committed
511
    ERR_print_errors_fp( stderr );
Chad Barb's avatar
 
Chad Barb committed
512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559
    exit(-1);
  }

  peer = SSL_get_peer_certificate( ssl );

  // X509_print_fp( stdout );
  // X509_digest( &peer, EVP_sha() , digest, &len );

  //X509_digest( peer, EVP_md5(), digest, &len );
  
  X509_digest( peer, EVP_sha(), digest, &len );

  for (i = 0; i < len; i++) {
    sprintf( digestHex + (i * 2), "%02x", (unsigned int) digest[i] );
  }

  if (debug) {
    printf("ACL's  cert digest: %s\n"
	   "Server cert digest: %s\n",
	   certString, 
	   digestHex );
  }

  if (0 != strcmp( certString, digestHex )) {
    fprintf(stderr, 
	    "Server does not have certificate described in ACL:\n"
	    "ACL's  cert digest: %s\n" 
	    "Server cert digest: %s\n"
	    "Possible man-in-the-middle attack. Aborting.\n\n",
	    certString,
	    digestHex );

    exit(-1);
  }
}


int writeSSL( void * data, int size )
{
  return SSL_write( ssl, data, size );
}

int readSSL( void * data, int size )
{
  return SSL_read( ssl, data, size );
}

#endif /* WITHSSL */