1 /* $OpenBSD: netcat.c,v 1.121 2014/06/10 16:35:42 tedu Exp $ */ 2 /* 3 * Copyright (c) 2001 Eric Jackson <ericj@monkey.org> 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote products 15 * derived from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* 30 * Re-written nc(1) for OpenBSD. Original implementation by 31 * *Hobbit* <hobbit@avian.org>. 32 */ 33 34 #include <sys/types.h> 35 #include <sys/socket.h> 36 #include <sys/time.h> 37 #include <sys/uio.h> 38 #include <sys/un.h> 39 40 #include <netinet/in.h> 41 #include <netinet/in_systm.h> 42 #include <netinet/tcp.h> 43 #include <netinet/ip.h> 44 #include <arpa/telnet.h> 45 46 #include <err.h> 47 #include <errno.h> 48 #include <netdb.h> 49 #include <poll.h> 50 #include <stdarg.h> 51 #include <stdio.h> 52 #include <stdlib.h> 53 #include <string.h> 54 #include <unistd.h> 55 #include <fcntl.h> 56 #include <limits.h> 57 #include "atomicio.h" 58 59 #ifndef SUN_LEN 60 #define SUN_LEN(su) \ 61 (sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path)) 62 #endif 63 64 #define PORT_MAX 65535 65 #define PORT_MAX_LEN 6 66 #define UNIX_DG_TMP_SOCKET_SIZE 19 67 68 /* Command Line Options */ 69 int dflag; /* detached, no stdin */ 70 int Fflag; /* fdpass sock to stdout */ 71 unsigned int iflag; /* Interval Flag */ 72 int kflag; /* More than one connect */ 73 int lflag; /* Bind to local port */ 74 int Nflag; /* shutdown() network socket */ 75 int nflag; /* Don't do name look up */ 76 char *Pflag; /* Proxy username */ 77 char *pflag; /* Localport flag */ 78 int rflag; /* Random ports flag */ 79 char *sflag; /* Source Address */ 80 int tflag; /* Telnet Emulation */ 81 int uflag; /* UDP - Default to TCP */ 82 int vflag; /* Verbosity */ 83 int xflag; /* Socks proxy */ 84 int zflag; /* Port Scan Flag */ 85 int Dflag; /* sodebug */ 86 int Iflag; /* TCP receive buffer size */ 87 int Oflag; /* TCP send buffer size */ 88 int Sflag; /* TCP MD5 signature option */ 89 int Tflag = -1; /* IP Type of Service */ 90 int rtableid = -1; 91 92 int timeout = -1; 93 int family = AF_UNSPEC; 94 char *portlist[PORT_MAX+1]; 95 char *unix_dg_tmp_socket; 96 97 void atelnet(int, unsigned char *, unsigned int); 98 void build_ports(char *); 99 void help(void); 100 int local_listen(char *, char *, struct addrinfo); 101 void readwrite(int); 102 void fdpass(int nfd) __attribute__((noreturn)); 103 int remote_connect(const char *, const char *, struct addrinfo); 104 int timeout_connect(int, const struct sockaddr *, socklen_t); 105 int socks_connect(const char *, const char *, struct addrinfo, 106 const char *, const char *, struct addrinfo, int, const char *); 107 int udptest(int); 108 int unix_bind(char *); 109 int unix_connect(char *); 110 int unix_listen(char *); 111 void set_common_sockopts(int); 112 int map_tos(char *, int *); 113 void report_connect(const struct sockaddr *, socklen_t); 114 void usage(int); 115 116 int 117 main(int argc, char *argv[]) 118 { 119 int ch, s, ret, socksv; 120 char *host, *uport; 121 struct addrinfo hints; 122 struct servent *sv; 123 socklen_t len; 124 struct sockaddr_storage cliaddr; 125 char *proxy; 126 const char *errstr, *proxyhost = "", *proxyport = NULL; 127 struct addrinfo proxyhints; 128 char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE]; 129 130 ret = 1; 131 s = 0; 132 socksv = 5; 133 host = NULL; 134 uport = NULL; 135 sv = NULL; 136 137 while ((ch = getopt(argc, argv, 138 "46DdFhI:i:klNnO:P:p:rSs:tT:UuV:vw:X:x:z")) != -1) { 139 switch (ch) { 140 case '4': 141 family = AF_INET; 142 break; 143 case '6': 144 family = AF_INET6; 145 break; 146 case 'U': 147 family = AF_UNIX; 148 break; 149 case 'X': 150 if (strcasecmp(optarg, "connect") == 0) 151 socksv = -1; /* HTTP proxy CONNECT */ 152 else if (strcmp(optarg, "4") == 0) 153 socksv = 4; /* SOCKS v.4 */ 154 else if (strcmp(optarg, "5") == 0) 155 socksv = 5; /* SOCKS v.5 */ 156 else 157 errx(1, "unsupported proxy protocol"); 158 break; 159 case 'd': 160 dflag = 1; 161 break; 162 case 'F': 163 Fflag = 1; 164 break; 165 case 'h': 166 help(); 167 break; 168 case 'i': 169 iflag = strtonum(optarg, 0, UINT_MAX, &errstr); 170 if (errstr) 171 errx(1, "interval %s: %s", errstr, optarg); 172 break; 173 case 'k': 174 kflag = 1; 175 break; 176 case 'l': 177 lflag = 1; 178 break; 179 case 'N': 180 Nflag = 1; 181 break; 182 case 'n': 183 nflag = 1; 184 break; 185 case 'P': 186 Pflag = optarg; 187 break; 188 case 'p': 189 pflag = optarg; 190 break; 191 case 'r': 192 rflag = 1; 193 break; 194 case 's': 195 sflag = optarg; 196 break; 197 case 't': 198 tflag = 1; 199 break; 200 case 'u': 201 uflag = 1; 202 break; 203 case 'V': 204 rtableid = (int)strtonum(optarg, 0, 205 RT_TABLEID_MAX, &errstr); 206 if (errstr) 207 errx(1, "rtable %s: %s", errstr, optarg); 208 break; 209 case 'v': 210 vflag = 1; 211 break; 212 case 'w': 213 timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr); 214 if (errstr) 215 errx(1, "timeout %s: %s", errstr, optarg); 216 timeout *= 1000; 217 break; 218 case 'x': 219 xflag = 1; 220 if ((proxy = strdup(optarg)) == NULL) 221 err(1, NULL); 222 break; 223 case 'z': 224 zflag = 1; 225 break; 226 case 'D': 227 Dflag = 1; 228 break; 229 case 'I': 230 Iflag = strtonum(optarg, 1, 65536 << 14, &errstr); 231 if (errstr != NULL) 232 errx(1, "TCP receive window %s: %s", 233 errstr, optarg); 234 break; 235 case 'O': 236 Oflag = strtonum(optarg, 1, 65536 << 14, &errstr); 237 if (errstr != NULL) 238 errx(1, "TCP send window %s: %s", 239 errstr, optarg); 240 break; 241 case 'S': 242 Sflag = 1; 243 break; 244 case 'T': 245 errstr = NULL; 246 errno = 0; 247 if (map_tos(optarg, &Tflag)) 248 break; 249 if (strlen(optarg) > 1 && optarg[0] == '0' && 250 optarg[1] == 'x') 251 Tflag = (int)strtol(optarg, NULL, 16); 252 else 253 Tflag = (int)strtonum(optarg, 0, 255, 254 &errstr); 255 if (Tflag < 0 || Tflag > 255 || errstr || errno) 256 errx(1, "illegal tos value %s", optarg); 257 break; 258 default: 259 usage(1); 260 } 261 } 262 argc -= optind; 263 argv += optind; 264 265 /* Cruft to make sure options are clean, and used properly. */ 266 if (argv[0] && !argv[1] && family == AF_UNIX) { 267 host = argv[0]; 268 uport = NULL; 269 } else if (argv[0] && !argv[1]) { 270 if (!lflag) 271 usage(1); 272 uport = argv[0]; 273 host = NULL; 274 } else if (argv[0] && argv[1]) { 275 host = argv[0]; 276 uport = argv[1]; 277 } else 278 usage(1); 279 280 if (lflag && sflag) 281 errx(1, "cannot use -s and -l"); 282 if (lflag && pflag) 283 errx(1, "cannot use -p and -l"); 284 if (lflag && zflag) 285 errx(1, "cannot use -z and -l"); 286 if (!lflag && kflag) 287 errx(1, "must use -l with -k"); 288 289 /* Get name of temporary socket for unix datagram client */ 290 if ((family == AF_UNIX) && uflag && !lflag) { 291 if (sflag) { 292 unix_dg_tmp_socket = sflag; 293 } else { 294 strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX", 295 UNIX_DG_TMP_SOCKET_SIZE); 296 if (mktemp(unix_dg_tmp_socket_buf) == NULL) 297 err(1, "mktemp"); 298 unix_dg_tmp_socket = unix_dg_tmp_socket_buf; 299 } 300 } 301 302 /* Initialize addrinfo structure. */ 303 if (family != AF_UNIX) { 304 memset(&hints, 0, sizeof(struct addrinfo)); 305 hints.ai_family = family; 306 hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; 307 hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; 308 if (nflag) 309 hints.ai_flags |= AI_NUMERICHOST; 310 } 311 312 if (xflag) { 313 if (uflag) 314 errx(1, "no proxy support for UDP mode"); 315 316 if (lflag) 317 errx(1, "no proxy support for listen"); 318 319 if (family == AF_UNIX) 320 errx(1, "no proxy support for unix sockets"); 321 322 /* XXX IPv6 transport to proxy would probably work */ 323 if (family == AF_INET6) 324 errx(1, "no proxy support for IPv6"); 325 326 if (sflag) 327 errx(1, "no proxy support for local source address"); 328 329 proxyhost = strsep(&proxy, ":"); 330 proxyport = proxy; 331 332 memset(&proxyhints, 0, sizeof(struct addrinfo)); 333 proxyhints.ai_family = family; 334 proxyhints.ai_socktype = SOCK_STREAM; 335 proxyhints.ai_protocol = IPPROTO_TCP; 336 if (nflag) 337 proxyhints.ai_flags |= AI_NUMERICHOST; 338 } 339 340 if (lflag) { 341 int connfd; 342 ret = 0; 343 344 if (family == AF_UNIX) { 345 if (uflag) 346 s = unix_bind(host); 347 else 348 s = unix_listen(host); 349 } 350 351 /* Allow only one connection at a time, but stay alive. */ 352 for (;;) { 353 if (family != AF_UNIX) 354 s = local_listen(host, uport, hints); 355 if (s < 0) 356 err(1, NULL); 357 /* 358 * For UDP and -k, don't connect the socket, let it 359 * receive datagrams from multiple socket pairs. 360 */ 361 if (uflag && kflag) 362 readwrite(s); 363 /* 364 * For UDP and not -k, we will use recvfrom() initially 365 * to wait for a caller, then use the regular functions 366 * to talk to the caller. 367 */ 368 else if (uflag && !kflag) { 369 int rv, plen; 370 char buf[16384]; 371 struct sockaddr_storage z; 372 373 len = sizeof(z); 374 plen = 2048; 375 rv = recvfrom(s, buf, plen, MSG_PEEK, 376 (struct sockaddr *)&z, &len); 377 if (rv < 0) 378 err(1, "recvfrom"); 379 380 rv = connect(s, (struct sockaddr *)&z, len); 381 if (rv < 0) 382 err(1, "connect"); 383 384 if (vflag) 385 report_connect((struct sockaddr *)&z, len); 386 387 readwrite(s); 388 } else { 389 len = sizeof(cliaddr); 390 connfd = accept(s, (struct sockaddr *)&cliaddr, 391 &len); 392 if (connfd == -1) { 393 /* For now, all errnos are fatal */ 394 err(1, "accept"); 395 } 396 if (vflag) 397 report_connect((struct sockaddr *)&cliaddr, len); 398 399 readwrite(connfd); 400 close(connfd); 401 } 402 403 if (family != AF_UNIX) 404 close(s); 405 else if (uflag) { 406 if (connect(s, NULL, 0) < 0) 407 err(1, "connect"); 408 } 409 410 if (!kflag) 411 break; 412 } 413 } else if (family == AF_UNIX) { 414 ret = 0; 415 416 if ((s = unix_connect(host)) > 0 && !zflag) { 417 readwrite(s); 418 close(s); 419 } else 420 ret = 1; 421 422 if (uflag) 423 unlink(unix_dg_tmp_socket); 424 exit(ret); 425 426 } else { 427 int i = 0; 428 429 /* Construct the portlist[] array. */ 430 build_ports(uport); 431 432 /* Cycle through portlist, connecting to each port. */ 433 for (i = 0; portlist[i] != NULL; i++) { 434 if (s) 435 close(s); 436 437 if (xflag) 438 s = socks_connect(host, portlist[i], hints, 439 proxyhost, proxyport, proxyhints, socksv, 440 Pflag); 441 else 442 s = remote_connect(host, portlist[i], hints); 443 444 if (s < 0) 445 continue; 446 447 ret = 0; 448 if (vflag || zflag) { 449 /* For UDP, make sure we are connected. */ 450 if (uflag) { 451 if (udptest(s) == -1) { 452 ret = 1; 453 continue; 454 } 455 } 456 457 /* Don't look up port if -n. */ 458 if (nflag) 459 sv = NULL; 460 else { 461 sv = getservbyport( 462 ntohs(atoi(portlist[i])), 463 uflag ? "udp" : "tcp"); 464 } 465 466 fprintf(stderr, 467 "Connection to %s %s port [%s/%s] " 468 "succeeded!\n", host, portlist[i], 469 uflag ? "udp" : "tcp", 470 sv ? sv->s_name : "*"); 471 } 472 if (Fflag) 473 fdpass(s); 474 else if (!zflag) 475 readwrite(s); 476 } 477 } 478 479 if (s) 480 close(s); 481 482 exit(ret); 483 } 484 485 /* 486 * unix_bind() 487 * Returns a unix socket bound to the given path 488 */ 489 int 490 unix_bind(char *path) 491 { 492 struct sockaddr_un sun; 493 int s; 494 495 /* Create unix domain socket. */ 496 if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM, 497 0)) < 0) 498 return (-1); 499 500 memset(&sun, 0, sizeof(struct sockaddr_un)); 501 sun.sun_family = AF_UNIX; 502 503 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= 504 sizeof(sun.sun_path)) { 505 close(s); 506 errno = ENAMETOOLONG; 507 return (-1); 508 } 509 510 if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { 511 close(s); 512 return (-1); 513 } 514 return (s); 515 } 516 517 /* 518 * unix_connect() 519 * Returns a socket connected to a local unix socket. Returns -1 on failure. 520 */ 521 int 522 unix_connect(char *path) 523 { 524 struct sockaddr_un sun; 525 int s; 526 527 if (uflag) { 528 if ((s = unix_bind(unix_dg_tmp_socket)) < 0) 529 return (-1); 530 } else { 531 if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) 532 return (-1); 533 } 534 (void)fcntl(s, F_SETFD, FD_CLOEXEC); 535 536 memset(&sun, 0, sizeof(struct sockaddr_un)); 537 sun.sun_family = AF_UNIX; 538 539 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= 540 sizeof(sun.sun_path)) { 541 close(s); 542 errno = ENAMETOOLONG; 543 return (-1); 544 } 545 if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { 546 close(s); 547 return (-1); 548 } 549 return (s); 550 551 } 552 553 /* 554 * unix_listen() 555 * Create a unix domain socket, and listen on it. 556 */ 557 int 558 unix_listen(char *path) 559 { 560 int s; 561 if ((s = unix_bind(path)) < 0) 562 return (-1); 563 564 if (listen(s, 5) < 0) { 565 close(s); 566 return (-1); 567 } 568 return (s); 569 } 570 571 /* 572 * remote_connect() 573 * Returns a socket connected to a remote host. Properly binds to a local 574 * port or source address if needed. Returns -1 on failure. 575 */ 576 int 577 remote_connect(const char *host, const char *port, struct addrinfo hints) 578 { 579 struct addrinfo *res, *res0; 580 int s, error, on = 1; 581 582 if ((error = getaddrinfo(host, port, &hints, &res))) 583 errx(1, "getaddrinfo: %s", gai_strerror(error)); 584 585 res0 = res; 586 do { 587 if ((s = socket(res0->ai_family, res0->ai_socktype, 588 res0->ai_protocol)) < 0) 589 continue; 590 591 if (rtableid >= 0 && (setsockopt(s, SOL_SOCKET, SO_RTABLE, 592 &rtableid, sizeof(rtableid)) == -1)) 593 err(1, "setsockopt SO_RTABLE"); 594 595 /* Bind to a local port or source address if specified. */ 596 if (sflag || pflag) { 597 struct addrinfo ahints, *ares; 598 599 /* try SO_BINDANY, but don't insist */ 600 setsockopt(s, SOL_SOCKET, SO_BINDANY, &on, sizeof(on)); 601 memset(&ahints, 0, sizeof(struct addrinfo)); 602 ahints.ai_family = res0->ai_family; 603 ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; 604 ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; 605 ahints.ai_flags = AI_PASSIVE; 606 if ((error = getaddrinfo(sflag, pflag, &ahints, &ares))) 607 errx(1, "getaddrinfo: %s", gai_strerror(error)); 608 609 if (bind(s, (struct sockaddr *)ares->ai_addr, 610 ares->ai_addrlen) < 0) 611 err(1, "bind failed"); 612 freeaddrinfo(ares); 613 } 614 615 set_common_sockopts(s); 616 617 if (timeout_connect(s, res0->ai_addr, res0->ai_addrlen) == 0) 618 break; 619 else if (vflag) 620 warn("connect to %s port %s (%s) failed", host, port, 621 uflag ? "udp" : "tcp"); 622 623 close(s); 624 s = -1; 625 } while ((res0 = res0->ai_next) != NULL); 626 627 freeaddrinfo(res); 628 629 return (s); 630 } 631 632 int 633 timeout_connect(int s, const struct sockaddr *name, socklen_t namelen) 634 { 635 struct pollfd pfd; 636 socklen_t optlen; 637 int flags, optval; 638 int ret; 639 640 if (timeout != -1) { 641 flags = fcntl(s, F_GETFL, 0); 642 if (fcntl(s, F_SETFL, flags | O_NONBLOCK) == -1) 643 err(1, "set non-blocking mode"); 644 } 645 646 if ((ret = connect(s, name, namelen)) != 0 && errno == EINPROGRESS) { 647 pfd.fd = s; 648 pfd.events = POLLOUT; 649 if ((ret = poll(&pfd, 1, timeout)) == 1) { 650 optlen = sizeof(optval); 651 if ((ret = getsockopt(s, SOL_SOCKET, SO_ERROR, 652 &optval, &optlen)) == 0) { 653 errno = optval; 654 ret = optval == 0 ? 0 : -1; 655 } 656 } else if (ret == 0) { 657 errno = ETIMEDOUT; 658 ret = -1; 659 } else 660 err(1, "poll failed"); 661 } 662 663 if (timeout != -1 && fcntl(s, F_SETFL, flags) == -1) 664 err(1, "restoring flags"); 665 666 return (ret); 667 } 668 669 /* 670 * local_listen() 671 * Returns a socket listening on a local port, binds to specified source 672 * address. Returns -1 on failure. 673 */ 674 int 675 local_listen(char *host, char *port, struct addrinfo hints) 676 { 677 struct addrinfo *res, *res0; 678 int s, ret, x = 1; 679 int error; 680 681 /* Allow nodename to be null. */ 682 hints.ai_flags |= AI_PASSIVE; 683 684 /* 685 * In the case of binding to a wildcard address 686 * default to binding to an ipv4 address. 687 */ 688 if (host == NULL && hints.ai_family == AF_UNSPEC) 689 hints.ai_family = AF_INET; 690 691 if ((error = getaddrinfo(host, port, &hints, &res))) 692 errx(1, "getaddrinfo: %s", gai_strerror(error)); 693 694 res0 = res; 695 do { 696 if ((s = socket(res0->ai_family, res0->ai_socktype, 697 res0->ai_protocol)) < 0) 698 continue; 699 700 if (rtableid >= 0 && (setsockopt(s, SOL_SOCKET, SO_RTABLE, 701 &rtableid, sizeof(rtableid)) == -1)) 702 err(1, "setsockopt SO_RTABLE"); 703 704 ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x)); 705 if (ret == -1) 706 err(1, NULL); 707 708 set_common_sockopts(s); 709 710 if (bind(s, (struct sockaddr *)res0->ai_addr, 711 res0->ai_addrlen) == 0) 712 break; 713 714 close(s); 715 s = -1; 716 } while ((res0 = res0->ai_next) != NULL); 717 718 if (!uflag && s != -1) { 719 if (listen(s, 1) < 0) 720 err(1, "listen"); 721 } 722 723 freeaddrinfo(res); 724 725 return (s); 726 } 727 728 /* 729 * readwrite() 730 * Loop that polls on the network file descriptor and stdin. 731 */ 732 void 733 readwrite(int nfd) 734 { 735 struct pollfd pfd[2]; 736 unsigned char buf[16 * 1024]; 737 int n, wfd = fileno(stdin); 738 int lfd = fileno(stdout); 739 int plen; 740 741 plen = sizeof(buf); 742 743 /* Setup Network FD */ 744 pfd[0].fd = nfd; 745 pfd[0].events = POLLIN; 746 747 /* Set up STDIN FD. */ 748 pfd[1].fd = wfd; 749 pfd[1].events = POLLIN; 750 751 while (pfd[0].fd != -1) { 752 if (iflag) 753 sleep(iflag); 754 755 if ((n = poll(pfd, 2 - dflag, timeout)) < 0) { 756 close(nfd); 757 err(1, "Polling Error"); 758 } 759 760 if (n == 0) 761 return; 762 763 if (pfd[0].revents & POLLIN) { 764 if ((n = read(nfd, buf, plen)) < 0) 765 return; 766 else if (n == 0) { 767 shutdown(nfd, SHUT_RD); 768 pfd[0].fd = -1; 769 pfd[0].events = 0; 770 } else { 771 if (tflag) 772 atelnet(nfd, buf, n); 773 if (atomicio(vwrite, lfd, buf, n) != n) 774 return; 775 } 776 } 777 778 if (!dflag && pfd[1].revents & POLLIN) { 779 if ((n = read(wfd, buf, plen)) < 0) 780 return; 781 else if (n == 0) { 782 if (Nflag) 783 shutdown(nfd, SHUT_WR); 784 pfd[1].fd = -1; 785 pfd[1].events = 0; 786 } else { 787 if (atomicio(vwrite, nfd, buf, n) != n) 788 return; 789 } 790 } 791 } 792 } 793 794 /* 795 * fdpass() 796 * Pass the connected file descriptor to stdout and exit. 797 */ 798 void 799 fdpass(int nfd) 800 { 801 struct msghdr mh; 802 union { 803 struct cmsghdr hdr; 804 char buf[CMSG_SPACE(sizeof(int))]; 805 } cmsgbuf; 806 struct cmsghdr *cmsg; 807 struct iovec iov; 808 char c = '\0'; 809 ssize_t r; 810 struct pollfd pfd; 811 812 /* Avoid obvious stupidity */ 813 if (isatty(STDOUT_FILENO)) 814 errx(1, "Cannot pass file descriptor to tty"); 815 816 bzero(&mh, sizeof(mh)); 817 bzero(&cmsgbuf, sizeof(cmsgbuf)); 818 bzero(&iov, sizeof(iov)); 819 bzero(&pfd, sizeof(pfd)); 820 821 mh.msg_control = (caddr_t)&cmsgbuf.buf; 822 mh.msg_controllen = sizeof(cmsgbuf.buf); 823 cmsg = CMSG_FIRSTHDR(&mh); 824 cmsg->cmsg_len = CMSG_LEN(sizeof(int)); 825 cmsg->cmsg_level = SOL_SOCKET; 826 cmsg->cmsg_type = SCM_RIGHTS; 827 *(int *)CMSG_DATA(cmsg) = nfd; 828 829 iov.iov_base = &c; 830 iov.iov_len = 1; 831 mh.msg_iov = &iov; 832 mh.msg_iovlen = 1; 833 834 bzero(&pfd, sizeof(pfd)); 835 pfd.fd = STDOUT_FILENO; 836 for (;;) { 837 r = sendmsg(STDOUT_FILENO, &mh, 0); 838 if (r == -1) { 839 if (errno == EAGAIN || errno == EINTR) { 840 pfd.events = POLLOUT; 841 if (poll(&pfd, 1, -1) == -1) 842 err(1, "poll"); 843 continue; 844 } 845 err(1, "sendmsg"); 846 } else if (r == -1) 847 errx(1, "sendmsg: unexpected return value %zd", r); 848 else 849 break; 850 } 851 exit(0); 852 } 853 854 /* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */ 855 void 856 atelnet(int nfd, unsigned char *buf, unsigned int size) 857 { 858 unsigned char *p, *end; 859 unsigned char obuf[4]; 860 861 if (size < 3) 862 return; 863 end = buf + size - 2; 864 865 for (p = buf; p < end; p++) { 866 if (*p != IAC) 867 continue; 868 869 obuf[0] = IAC; 870 p++; 871 if ((*p == WILL) || (*p == WONT)) 872 obuf[1] = DONT; 873 else if ((*p == DO) || (*p == DONT)) 874 obuf[1] = WONT; 875 else 876 continue; 877 878 p++; 879 obuf[2] = *p; 880 if (atomicio(vwrite, nfd, obuf, 3) != 3) 881 warn("Write Error!"); 882 } 883 } 884 885 /* 886 * build_ports() 887 * Build an array of ports in portlist[], listing each port 888 * that we should try to connect to. 889 */ 890 void 891 build_ports(char *p) 892 { 893 const char *errstr; 894 char *n; 895 int hi, lo, cp; 896 int x = 0; 897 898 if ((n = strchr(p, '-')) != NULL) { 899 *n = '\0'; 900 n++; 901 902 /* Make sure the ports are in order: lowest->highest. */ 903 hi = strtonum(n, 1, PORT_MAX, &errstr); 904 if (errstr) 905 errx(1, "port number %s: %s", errstr, n); 906 lo = strtonum(p, 1, PORT_MAX, &errstr); 907 if (errstr) 908 errx(1, "port number %s: %s", errstr, p); 909 910 if (lo > hi) { 911 cp = hi; 912 hi = lo; 913 lo = cp; 914 } 915 916 /* Load ports sequentially. */ 917 for (cp = lo; cp <= hi; cp++) { 918 portlist[x] = calloc(1, PORT_MAX_LEN); 919 if (portlist[x] == NULL) 920 err(1, NULL); 921 snprintf(portlist[x], PORT_MAX_LEN, "%d", cp); 922 x++; 923 } 924 925 /* Randomly swap ports. */ 926 if (rflag) { 927 int y; 928 char *c; 929 930 for (x = 0; x <= (hi - lo); x++) { 931 y = (arc4random() & 0xFFFF) % (hi - lo); 932 c = portlist[x]; 933 portlist[x] = portlist[y]; 934 portlist[y] = c; 935 } 936 } 937 } else { 938 hi = strtonum(p, 1, PORT_MAX, &errstr); 939 if (errstr) 940 errx(1, "port number %s: %s", errstr, p); 941 portlist[0] = strdup(p); 942 if (portlist[0] == NULL) 943 err(1, NULL); 944 } 945 } 946 947 /* 948 * udptest() 949 * Do a few writes to see if the UDP port is there. 950 * Fails once PF state table is full. 951 */ 952 int 953 udptest(int s) 954 { 955 int i, ret; 956 957 for (i = 0; i <= 3; i++) { 958 if (write(s, "X", 1) == 1) 959 ret = 1; 960 else 961 ret = -1; 962 } 963 return (ret); 964 } 965 966 void 967 set_common_sockopts(int s) 968 { 969 int x = 1; 970 971 if (Sflag) { 972 if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG, 973 &x, sizeof(x)) == -1) 974 err(1, NULL); 975 } 976 if (Dflag) { 977 if (setsockopt(s, SOL_SOCKET, SO_DEBUG, 978 &x, sizeof(x)) == -1) 979 err(1, NULL); 980 } 981 if (Tflag != -1) { 982 if (setsockopt(s, IPPROTO_IP, IP_TOS, 983 &Tflag, sizeof(Tflag)) == -1) 984 err(1, "set IP ToS"); 985 } 986 if (Iflag) { 987 if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, 988 &Iflag, sizeof(Iflag)) == -1) 989 err(1, "set TCP receive buffer size"); 990 } 991 if (Oflag) { 992 if (setsockopt(s, SOL_SOCKET, SO_SNDBUF, 993 &Oflag, sizeof(Oflag)) == -1) 994 err(1, "set TCP send buffer size"); 995 } 996 } 997 998 int 999 map_tos(char *s, int *val) 1000 { 1001 /* DiffServ Codepoints and other TOS mappings */ 1002 const struct toskeywords { 1003 const char *keyword; 1004 int val; 1005 } *t, toskeywords[] = { 1006 { "af11", IPTOS_DSCP_AF11 }, 1007 { "af12", IPTOS_DSCP_AF12 }, 1008 { "af13", IPTOS_DSCP_AF13 }, 1009 { "af21", IPTOS_DSCP_AF21 }, 1010 { "af22", IPTOS_DSCP_AF22 }, 1011 { "af23", IPTOS_DSCP_AF23 }, 1012 { "af31", IPTOS_DSCP_AF31 }, 1013 { "af32", IPTOS_DSCP_AF32 }, 1014 { "af33", IPTOS_DSCP_AF33 }, 1015 { "af41", IPTOS_DSCP_AF41 }, 1016 { "af42", IPTOS_DSCP_AF42 }, 1017 { "af43", IPTOS_DSCP_AF43 }, 1018 { "critical", IPTOS_PREC_CRITIC_ECP }, 1019 { "cs0", IPTOS_DSCP_CS0 }, 1020 { "cs1", IPTOS_DSCP_CS1 }, 1021 { "cs2", IPTOS_DSCP_CS2 }, 1022 { "cs3", IPTOS_DSCP_CS3 }, 1023 { "cs4", IPTOS_DSCP_CS4 }, 1024 { "cs5", IPTOS_DSCP_CS5 }, 1025 { "cs6", IPTOS_DSCP_CS6 }, 1026 { "cs7", IPTOS_DSCP_CS7 }, 1027 { "ef", IPTOS_DSCP_EF }, 1028 { "inetcontrol", IPTOS_PREC_INTERNETCONTROL }, 1029 { "lowdelay", IPTOS_LOWDELAY }, 1030 { "netcontrol", IPTOS_PREC_NETCONTROL }, 1031 { "reliability", IPTOS_RELIABILITY }, 1032 { "throughput", IPTOS_THROUGHPUT }, 1033 { NULL, -1 }, 1034 }; 1035 1036 for (t = toskeywords; t->keyword != NULL; t++) { 1037 if (strcmp(s, t->keyword) == 0) { 1038 *val = t->val; 1039 return (1); 1040 } 1041 } 1042 1043 return (0); 1044 } 1045 1046 void 1047 report_connect(const struct sockaddr *sa, socklen_t salen) 1048 { 1049 char remote_host[NI_MAXHOST]; 1050 char remote_port[NI_MAXSERV]; 1051 int herr; 1052 int flags = NI_NUMERICSERV; 1053 1054 if (nflag) 1055 flags |= NI_NUMERICHOST; 1056 1057 if ((herr = getnameinfo(sa, salen, 1058 remote_host, sizeof(remote_host), 1059 remote_port, sizeof(remote_port), 1060 flags)) != 0) { 1061 if (herr == EAI_SYSTEM) 1062 err(1, "getnameinfo"); 1063 else 1064 errx(1, "getnameinfo: %s", gai_strerror(herr)); 1065 } 1066 1067 fprintf(stderr, 1068 "Connection from %s %s " 1069 "received!\n", remote_host, remote_port); 1070 } 1071 1072 void 1073 help(void) 1074 { 1075 usage(0); 1076 fprintf(stderr, "\tCommand Summary:\n\ 1077 \t-4 Use IPv4\n\ 1078 \t-6 Use IPv6\n\ 1079 \t-D Enable the debug socket option\n\ 1080 \t-d Detach from stdin\n\ 1081 \t-F Pass socket fd\n\ 1082 \t-h This help text\n\ 1083 \t-I length TCP receive buffer length\n\ 1084 \t-i secs\t Delay interval for lines sent, ports scanned\n\ 1085 \t-k Keep inbound sockets open for multiple connects\n\ 1086 \t-l Listen mode, for inbound connects\n\ 1087 \t-N Shutdown the network socket after EOF on stdin\n\ 1088 \t-n Suppress name/port resolutions\n\ 1089 \t-O length TCP send buffer length\n\ 1090 \t-P proxyuser\tUsername for proxy authentication\n\ 1091 \t-p port\t Specify local port for remote connects\n\ 1092 \t-r Randomize remote ports\n\ 1093 \t-S Enable the TCP MD5 signature option\n\ 1094 \t-s addr\t Local source address\n\ 1095 \t-T toskeyword\tSet IP Type of Service\n\ 1096 \t-t Answer TELNET negotiation\n\ 1097 \t-U Use UNIX domain socket\n\ 1098 \t-u UDP mode\n\ 1099 \t-V rtable Specify alternate routing table\n\ 1100 \t-v Verbose\n\ 1101 \t-w secs\t Timeout for connects and final net reads\n\ 1102 \t-X proto Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\ 1103 \t-x addr[:port]\tSpecify proxy address and port\n\ 1104 \t-z Zero-I/O mode [used for scanning]\n\ 1105 Port numbers can be individual or ranges: lo-hi [inclusive]\n"); 1106 exit(1); 1107 } 1108 1109 void 1110 usage(int ret) 1111 { 1112 fprintf(stderr, 1113 "usage: nc [-46DdFhklNnrStUuvz] [-I length] [-i interval] [-O length]\n" 1114 "\t [-P proxy_username] [-p source_port] [-s source] [-T ToS]\n" 1115 "\t [-V rtable] [-w timeout] [-X proxy_protocol]\n" 1116 "\t [-x proxy_address[:port]] [destination] [port]\n"); 1117 if (ret) 1118 exit(1); 1119 } 1120