1 /* $OpenBSD: netcat.c,v 1.109 2012/07/07 15:33:02 haesbaert 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/un.h> 38 39 #include <netinet/in.h> 40 #include <netinet/in_systm.h> 41 #include <netinet/tcp.h> 42 #include <netinet/ip.h> 43 #include <arpa/telnet.h> 44 45 #include <err.h> 46 #include <errno.h> 47 #include <netdb.h> 48 #include <poll.h> 49 #include <stdarg.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include <unistd.h> 54 #include <fcntl.h> 55 #include <limits.h> 56 #include "atomicio.h" 57 58 #ifndef SUN_LEN 59 #define SUN_LEN(su) \ 60 (sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path)) 61 #endif 62 63 #define PORT_MAX 65535 64 #define PORT_MAX_LEN 6 65 #define UNIX_DG_TMP_SOCKET_SIZE 19 66 67 /* Command Line Options */ 68 int dflag; /* detached, no stdin */ 69 unsigned int iflag; /* Interval Flag */ 70 int kflag; /* More than one connect */ 71 int lflag; /* Bind to local port */ 72 int nflag; /* Don't do name look up */ 73 char *Pflag; /* Proxy username */ 74 char *pflag; /* Localport flag */ 75 int rflag; /* Random ports flag */ 76 char *sflag; /* Source Address */ 77 int tflag; /* Telnet Emulation */ 78 int uflag; /* UDP - Default to TCP */ 79 int vflag; /* Verbosity */ 80 int xflag; /* Socks proxy */ 81 int zflag; /* Port Scan Flag */ 82 int Dflag; /* sodebug */ 83 int Iflag; /* TCP receive buffer size */ 84 int Oflag; /* TCP send buffer size */ 85 int Sflag; /* TCP MD5 signature option */ 86 int Tflag = -1; /* IP Type of Service */ 87 u_int rtableid; 88 89 int timeout = -1; 90 int family = AF_UNSPEC; 91 char *portlist[PORT_MAX+1]; 92 char *unix_dg_tmp_socket; 93 94 void atelnet(int, unsigned char *, unsigned int); 95 void build_ports(char *); 96 void help(void); 97 int local_listen(char *, char *, struct addrinfo); 98 void readwrite(int); 99 int remote_connect(const char *, const char *, struct addrinfo); 100 int timeout_connect(int, const struct sockaddr *, socklen_t); 101 int socks_connect(const char *, const char *, struct addrinfo, 102 const char *, const char *, struct addrinfo, int, const char *); 103 int udptest(int); 104 int unix_bind(char *); 105 int unix_connect(char *); 106 int unix_listen(char *); 107 void set_common_sockopts(int); 108 int map_tos(char *, int *); 109 void report_connect(const struct sockaddr *, socklen_t); 110 void usage(int); 111 112 int 113 main(int argc, char *argv[]) 114 { 115 int ch, s, ret, socksv; 116 char *host, *uport; 117 struct addrinfo hints; 118 struct servent *sv; 119 socklen_t len; 120 struct sockaddr_storage cliaddr; 121 char *proxy; 122 const char *errstr, *proxyhost = "", *proxyport = NULL; 123 struct addrinfo proxyhints; 124 char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE]; 125 126 ret = 1; 127 s = 0; 128 socksv = 5; 129 host = NULL; 130 uport = NULL; 131 sv = NULL; 132 133 while ((ch = getopt(argc, argv, 134 "46DdhI:i:klnO:P:p:rSs:tT:UuV:vw:X:x:z")) != -1) { 135 switch (ch) { 136 case '4': 137 family = AF_INET; 138 break; 139 case '6': 140 family = AF_INET6; 141 break; 142 case 'U': 143 family = AF_UNIX; 144 break; 145 case 'X': 146 if (strcasecmp(optarg, "connect") == 0) 147 socksv = -1; /* HTTP proxy CONNECT */ 148 else if (strcmp(optarg, "4") == 0) 149 socksv = 4; /* SOCKS v.4 */ 150 else if (strcmp(optarg, "5") == 0) 151 socksv = 5; /* SOCKS v.5 */ 152 else 153 errx(1, "unsupported proxy protocol"); 154 break; 155 case 'd': 156 dflag = 1; 157 break; 158 case 'h': 159 help(); 160 break; 161 case 'i': 162 iflag = strtonum(optarg, 0, UINT_MAX, &errstr); 163 if (errstr) 164 errx(1, "interval %s: %s", errstr, optarg); 165 break; 166 case 'k': 167 kflag = 1; 168 break; 169 case 'l': 170 lflag = 1; 171 break; 172 case 'n': 173 nflag = 1; 174 break; 175 case 'P': 176 Pflag = optarg; 177 break; 178 case 'p': 179 pflag = optarg; 180 break; 181 case 'r': 182 rflag = 1; 183 break; 184 case 's': 185 sflag = optarg; 186 break; 187 case 't': 188 tflag = 1; 189 break; 190 case 'u': 191 uflag = 1; 192 break; 193 case 'V': 194 rtableid = (unsigned int)strtonum(optarg, 0, 195 RT_TABLEID_MAX, &errstr); 196 if (errstr) 197 errx(1, "rtable %s: %s", errstr, optarg); 198 break; 199 case 'v': 200 vflag = 1; 201 break; 202 case 'w': 203 timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr); 204 if (errstr) 205 errx(1, "timeout %s: %s", errstr, optarg); 206 timeout *= 1000; 207 break; 208 case 'x': 209 xflag = 1; 210 if ((proxy = strdup(optarg)) == NULL) 211 err(1, NULL); 212 break; 213 case 'z': 214 zflag = 1; 215 break; 216 case 'D': 217 Dflag = 1; 218 break; 219 case 'I': 220 Iflag = strtonum(optarg, 1, 65536 << 14, &errstr); 221 if (errstr != NULL) 222 errx(1, "TCP receive window %s: %s", 223 errstr, optarg); 224 break; 225 case 'O': 226 Oflag = strtonum(optarg, 1, 65536 << 14, &errstr); 227 if (errstr != NULL) 228 errx(1, "TCP send window %s: %s", 229 errstr, optarg); 230 break; 231 case 'S': 232 Sflag = 1; 233 break; 234 case 'T': 235 errstr = NULL; 236 errno = 0; 237 if (map_tos(optarg, &Tflag)) 238 break; 239 if (strlen(optarg) > 1 && optarg[0] == '0' && 240 optarg[1] == 'x') 241 Tflag = (int)strtol(optarg, NULL, 16); 242 else 243 Tflag = (int)strtonum(optarg, 0, 255, 244 &errstr); 245 if (Tflag < 0 || Tflag > 255 || errstr || errno) 246 errx(1, "illegal tos value %s", optarg); 247 break; 248 default: 249 usage(1); 250 } 251 } 252 argc -= optind; 253 argv += optind; 254 255 /* Cruft to make sure options are clean, and used properly. */ 256 if (argv[0] && !argv[1] && family == AF_UNIX) { 257 host = argv[0]; 258 uport = NULL; 259 } else if (argv[0] && !argv[1]) { 260 if (!lflag) 261 usage(1); 262 uport = argv[0]; 263 host = NULL; 264 } else if (argv[0] && argv[1]) { 265 host = argv[0]; 266 uport = argv[1]; 267 } else 268 usage(1); 269 270 if (lflag && sflag) 271 errx(1, "cannot use -s and -l"); 272 if (lflag && pflag) 273 errx(1, "cannot use -p and -l"); 274 if (lflag && zflag) 275 errx(1, "cannot use -z and -l"); 276 if (!lflag && kflag) 277 errx(1, "must use -l with -k"); 278 279 /* Get name of temporary socket for unix datagram client */ 280 if ((family == AF_UNIX) && uflag && !lflag) { 281 if (sflag) { 282 unix_dg_tmp_socket = sflag; 283 } else { 284 strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX", 285 UNIX_DG_TMP_SOCKET_SIZE); 286 if (mktemp(unix_dg_tmp_socket_buf) == NULL) 287 err(1, "mktemp"); 288 unix_dg_tmp_socket = unix_dg_tmp_socket_buf; 289 } 290 } 291 292 /* Initialize addrinfo structure. */ 293 if (family != AF_UNIX) { 294 memset(&hints, 0, sizeof(struct addrinfo)); 295 hints.ai_family = family; 296 hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; 297 hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; 298 if (nflag) 299 hints.ai_flags |= AI_NUMERICHOST; 300 } 301 302 if (xflag) { 303 if (uflag) 304 errx(1, "no proxy support for UDP mode"); 305 306 if (lflag) 307 errx(1, "no proxy support for listen"); 308 309 if (family == AF_UNIX) 310 errx(1, "no proxy support for unix sockets"); 311 312 /* XXX IPv6 transport to proxy would probably work */ 313 if (family == AF_INET6) 314 errx(1, "no proxy support for IPv6"); 315 316 if (sflag) 317 errx(1, "no proxy support for local source address"); 318 319 proxyhost = strsep(&proxy, ":"); 320 proxyport = proxy; 321 322 memset(&proxyhints, 0, sizeof(struct addrinfo)); 323 proxyhints.ai_family = family; 324 proxyhints.ai_socktype = SOCK_STREAM; 325 proxyhints.ai_protocol = IPPROTO_TCP; 326 if (nflag) 327 proxyhints.ai_flags |= AI_NUMERICHOST; 328 } 329 330 if (lflag) { 331 int connfd; 332 ret = 0; 333 334 if (family == AF_UNIX) { 335 if (uflag) 336 s = unix_bind(host); 337 else 338 s = unix_listen(host); 339 } 340 341 /* Allow only one connection at a time, but stay alive. */ 342 for (;;) { 343 if (family != AF_UNIX) 344 s = local_listen(host, uport, hints); 345 if (s < 0) 346 err(1, NULL); 347 /* 348 * For UDP and -k, don't connect the socket, let it 349 * receive datagrams from multiple socket pairs. 350 */ 351 if (uflag && kflag) 352 readwrite(s); 353 /* 354 * For UDP and not -k, we will use recvfrom() initially 355 * to wait for a caller, then use the regular functions 356 * to talk to the caller. 357 */ 358 else if (uflag && !kflag) { 359 int rv, plen; 360 char buf[16384]; 361 struct sockaddr_storage z; 362 363 len = sizeof(z); 364 plen = 2048; 365 rv = recvfrom(s, buf, plen, MSG_PEEK, 366 (struct sockaddr *)&z, &len); 367 if (rv < 0) 368 err(1, "recvfrom"); 369 370 rv = connect(s, (struct sockaddr *)&z, len); 371 if (rv < 0) 372 err(1, "connect"); 373 374 if (vflag) 375 report_connect((struct sockaddr *)&z, len); 376 377 readwrite(s); 378 } else { 379 len = sizeof(cliaddr); 380 connfd = accept(s, (struct sockaddr *)&cliaddr, 381 &len); 382 if (connfd == -1) 383 err(1, "accept"); 384 385 if (vflag) 386 report_connect((struct sockaddr *)&cliaddr, len); 387 388 readwrite(connfd); 389 close(connfd); 390 } 391 392 if (family != AF_UNIX) 393 close(s); 394 else if (uflag) { 395 if (connect(s, NULL, 0) < 0) 396 err(1, "connect"); 397 } 398 399 if (!kflag) 400 break; 401 } 402 } else if (family == AF_UNIX) { 403 ret = 0; 404 405 if ((s = unix_connect(host)) > 0 && !zflag) { 406 readwrite(s); 407 close(s); 408 } else 409 ret = 1; 410 411 if (uflag) 412 unlink(unix_dg_tmp_socket); 413 exit(ret); 414 415 } else { 416 int i = 0; 417 418 /* Construct the portlist[] array. */ 419 build_ports(uport); 420 421 /* Cycle through portlist, connecting to each port. */ 422 for (i = 0; portlist[i] != NULL; i++) { 423 if (s) 424 close(s); 425 426 if (xflag) 427 s = socks_connect(host, portlist[i], hints, 428 proxyhost, proxyport, proxyhints, socksv, 429 Pflag); 430 else 431 s = remote_connect(host, portlist[i], hints); 432 433 if (s < 0) 434 continue; 435 436 ret = 0; 437 if (vflag || zflag) { 438 /* For UDP, make sure we are connected. */ 439 if (uflag) { 440 if (udptest(s) == -1) { 441 ret = 1; 442 continue; 443 } 444 } 445 446 /* Don't look up port if -n. */ 447 if (nflag) 448 sv = NULL; 449 else { 450 sv = getservbyport( 451 ntohs(atoi(portlist[i])), 452 uflag ? "udp" : "tcp"); 453 } 454 455 fprintf(stderr, 456 "Connection to %s %s port [%s/%s] " 457 "succeeded!\n", host, portlist[i], 458 uflag ? "udp" : "tcp", 459 sv ? sv->s_name : "*"); 460 } 461 if (!zflag) 462 readwrite(s); 463 } 464 } 465 466 if (s) 467 close(s); 468 469 exit(ret); 470 } 471 472 /* 473 * unix_bind() 474 * Returns a unix socket bound to the given path 475 */ 476 int 477 unix_bind(char *path) 478 { 479 struct sockaddr_un sun; 480 int s; 481 482 /* Create unix domain socket. */ 483 if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM, 484 0)) < 0) 485 return (-1); 486 487 memset(&sun, 0, sizeof(struct sockaddr_un)); 488 sun.sun_family = AF_UNIX; 489 490 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= 491 sizeof(sun.sun_path)) { 492 close(s); 493 errno = ENAMETOOLONG; 494 return (-1); 495 } 496 497 if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { 498 close(s); 499 return (-1); 500 } 501 return (s); 502 } 503 504 /* 505 * unix_connect() 506 * Returns a socket connected to a local unix socket. Returns -1 on failure. 507 */ 508 int 509 unix_connect(char *path) 510 { 511 struct sockaddr_un sun; 512 int s; 513 514 if (uflag) { 515 if ((s = unix_bind(unix_dg_tmp_socket)) < 0) 516 return (-1); 517 } else { 518 if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) 519 return (-1); 520 } 521 (void)fcntl(s, F_SETFD, 1); 522 523 memset(&sun, 0, sizeof(struct sockaddr_un)); 524 sun.sun_family = AF_UNIX; 525 526 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= 527 sizeof(sun.sun_path)) { 528 close(s); 529 errno = ENAMETOOLONG; 530 return (-1); 531 } 532 if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { 533 close(s); 534 return (-1); 535 } 536 return (s); 537 538 } 539 540 /* 541 * unix_listen() 542 * Create a unix domain socket, and listen on it. 543 */ 544 int 545 unix_listen(char *path) 546 { 547 int s; 548 if ((s = unix_bind(path)) < 0) 549 return (-1); 550 551 if (listen(s, 5) < 0) { 552 close(s); 553 return (-1); 554 } 555 return (s); 556 } 557 558 /* 559 * remote_connect() 560 * Returns a socket connected to a remote host. Properly binds to a local 561 * port or source address if needed. Returns -1 on failure. 562 */ 563 int 564 remote_connect(const char *host, const char *port, struct addrinfo hints) 565 { 566 struct addrinfo *res, *res0; 567 int s, error, on = 1; 568 569 if ((error = getaddrinfo(host, port, &hints, &res))) 570 errx(1, "getaddrinfo: %s", gai_strerror(error)); 571 572 res0 = res; 573 do { 574 if ((s = socket(res0->ai_family, res0->ai_socktype, 575 res0->ai_protocol)) < 0) 576 continue; 577 578 if (rtableid) { 579 if (setsockopt(s, SOL_SOCKET, SO_RTABLE, &rtableid, 580 sizeof(rtableid)) == -1) 581 err(1, "setsockopt SO_RTABLE"); 582 } 583 584 /* Bind to a local port or source address if specified. */ 585 if (sflag || pflag) { 586 struct addrinfo ahints, *ares; 587 588 /* try SO_BINDANY, but don't insist */ 589 setsockopt(s, SOL_SOCKET, SO_BINDANY, &on, sizeof(on)); 590 memset(&ahints, 0, sizeof(struct addrinfo)); 591 ahints.ai_family = res0->ai_family; 592 ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; 593 ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; 594 ahints.ai_flags = AI_PASSIVE; 595 if ((error = getaddrinfo(sflag, pflag, &ahints, &ares))) 596 errx(1, "getaddrinfo: %s", gai_strerror(error)); 597 598 if (bind(s, (struct sockaddr *)ares->ai_addr, 599 ares->ai_addrlen) < 0) 600 errx(1, "bind failed: %s", strerror(errno)); 601 freeaddrinfo(ares); 602 } 603 604 set_common_sockopts(s); 605 606 if (timeout_connect(s, res0->ai_addr, res0->ai_addrlen) == 0) 607 break; 608 else if (vflag) 609 warn("connect to %s port %s (%s) failed", host, port, 610 uflag ? "udp" : "tcp"); 611 612 close(s); 613 s = -1; 614 } while ((res0 = res0->ai_next) != NULL); 615 616 freeaddrinfo(res); 617 618 return (s); 619 } 620 621 int 622 timeout_connect(int s, const struct sockaddr *name, socklen_t namelen) 623 { 624 struct pollfd pfd; 625 socklen_t optlen; 626 int flags, optval; 627 int ret; 628 629 if (timeout != -1) { 630 flags = fcntl(s, F_GETFL, 0); 631 if (fcntl(s, F_SETFL, flags | O_NONBLOCK) == -1) 632 err(1, "set non-blocking mode"); 633 } 634 635 if ((ret = connect(s, name, namelen)) != 0 && errno == EINPROGRESS) { 636 pfd.fd = s; 637 pfd.events = POLLOUT; 638 if ((ret = poll(&pfd, 1, timeout)) == 1) { 639 optlen = sizeof(optval); 640 if ((ret = getsockopt(s, SOL_SOCKET, SO_ERROR, 641 &optval, &optlen)) == 0) { 642 errno = optval; 643 ret = optval == 0 ? 0 : -1; 644 } 645 } else if (ret == 0) { 646 errno = ETIMEDOUT; 647 ret = -1; 648 } else 649 err(1, "poll failed"); 650 } 651 652 if (timeout != -1 && fcntl(s, F_SETFL, flags) == -1) 653 err(1, "restoring flags"); 654 655 return (ret); 656 } 657 658 /* 659 * local_listen() 660 * Returns a socket listening on a local port, binds to specified source 661 * address. Returns -1 on failure. 662 */ 663 int 664 local_listen(char *host, char *port, struct addrinfo hints) 665 { 666 struct addrinfo *res, *res0; 667 int s, ret, x = 1; 668 int error; 669 670 /* Allow nodename to be null. */ 671 hints.ai_flags |= AI_PASSIVE; 672 673 /* 674 * In the case of binding to a wildcard address 675 * default to binding to an ipv4 address. 676 */ 677 if (host == NULL && hints.ai_family == AF_UNSPEC) 678 hints.ai_family = AF_INET; 679 680 if ((error = getaddrinfo(host, port, &hints, &res))) 681 errx(1, "getaddrinfo: %s", gai_strerror(error)); 682 683 res0 = res; 684 do { 685 if ((s = socket(res0->ai_family, res0->ai_socktype, 686 res0->ai_protocol)) < 0) 687 continue; 688 689 if (rtableid) { 690 if (setsockopt(s, IPPROTO_IP, SO_RTABLE, &rtableid, 691 sizeof(rtableid)) == -1) 692 err(1, "setsockopt SO_RTABLE"); 693 } 694 695 ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x)); 696 if (ret == -1) 697 err(1, NULL); 698 699 set_common_sockopts(s); 700 701 if (bind(s, (struct sockaddr *)res0->ai_addr, 702 res0->ai_addrlen) == 0) 703 break; 704 705 close(s); 706 s = -1; 707 } while ((res0 = res0->ai_next) != NULL); 708 709 if (!uflag && s != -1) { 710 if (listen(s, 1) < 0) 711 err(1, "listen"); 712 } 713 714 freeaddrinfo(res); 715 716 return (s); 717 } 718 719 /* 720 * readwrite() 721 * Loop that polls on the network file descriptor and stdin. 722 */ 723 void 724 readwrite(int nfd) 725 { 726 struct pollfd pfd[2]; 727 unsigned char buf[16384]; 728 int n, wfd = fileno(stdin); 729 int lfd = fileno(stdout); 730 int plen; 731 732 plen = 2048; 733 734 /* Setup Network FD */ 735 pfd[0].fd = nfd; 736 pfd[0].events = POLLIN; 737 738 /* Set up STDIN FD. */ 739 pfd[1].fd = wfd; 740 pfd[1].events = POLLIN; 741 742 while (pfd[0].fd != -1) { 743 if (iflag) 744 sleep(iflag); 745 746 if ((n = poll(pfd, 2 - dflag, timeout)) < 0) { 747 close(nfd); 748 err(1, "Polling Error"); 749 } 750 751 if (n == 0) 752 return; 753 754 if (pfd[0].revents & POLLIN) { 755 if ((n = read(nfd, buf, plen)) < 0) 756 return; 757 else if (n == 0) { 758 shutdown(nfd, SHUT_RD); 759 pfd[0].fd = -1; 760 pfd[0].events = 0; 761 } else { 762 if (tflag) 763 atelnet(nfd, buf, n); 764 if (atomicio(vwrite, lfd, buf, n) != n) 765 return; 766 } 767 } 768 769 if (!dflag && pfd[1].revents & POLLIN) { 770 if ((n = read(wfd, buf, plen)) < 0) 771 return; 772 else if (n == 0) { 773 shutdown(nfd, SHUT_WR); 774 pfd[1].fd = -1; 775 pfd[1].events = 0; 776 } else { 777 if (atomicio(vwrite, nfd, buf, n) != n) 778 return; 779 } 780 } 781 } 782 } 783 784 /* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */ 785 void 786 atelnet(int nfd, unsigned char *buf, unsigned int size) 787 { 788 unsigned char *p, *end; 789 unsigned char obuf[4]; 790 791 if (size < 3) 792 return; 793 end = buf + size - 2; 794 795 for (p = buf; p < end; p++) { 796 if (*p != IAC) 797 continue; 798 799 obuf[0] = IAC; 800 p++; 801 if ((*p == WILL) || (*p == WONT)) 802 obuf[1] = DONT; 803 else if ((*p == DO) || (*p == DONT)) 804 obuf[1] = WONT; 805 else 806 continue; 807 808 p++; 809 obuf[2] = *p; 810 if (atomicio(vwrite, nfd, obuf, 3) != 3) 811 warn("Write Error!"); 812 } 813 } 814 815 /* 816 * build_ports() 817 * Build an array of ports in portlist[], listing each port 818 * that we should try to connect to. 819 */ 820 void 821 build_ports(char *p) 822 { 823 const char *errstr; 824 char *n; 825 int hi, lo, cp; 826 int x = 0; 827 828 if ((n = strchr(p, '-')) != NULL) { 829 *n = '\0'; 830 n++; 831 832 /* Make sure the ports are in order: lowest->highest. */ 833 hi = strtonum(n, 1, PORT_MAX, &errstr); 834 if (errstr) 835 errx(1, "port number %s: %s", errstr, n); 836 lo = strtonum(p, 1, PORT_MAX, &errstr); 837 if (errstr) 838 errx(1, "port number %s: %s", errstr, p); 839 840 if (lo > hi) { 841 cp = hi; 842 hi = lo; 843 lo = cp; 844 } 845 846 /* Load ports sequentially. */ 847 for (cp = lo; cp <= hi; cp++) { 848 portlist[x] = calloc(1, PORT_MAX_LEN); 849 if (portlist[x] == NULL) 850 err(1, NULL); 851 snprintf(portlist[x], PORT_MAX_LEN, "%d", cp); 852 x++; 853 } 854 855 /* Randomly swap ports. */ 856 if (rflag) { 857 int y; 858 char *c; 859 860 for (x = 0; x <= (hi - lo); x++) { 861 y = (arc4random() & 0xFFFF) % (hi - lo); 862 c = portlist[x]; 863 portlist[x] = portlist[y]; 864 portlist[y] = c; 865 } 866 } 867 } else { 868 hi = strtonum(p, 1, PORT_MAX, &errstr); 869 if (errstr) 870 errx(1, "port number %s: %s", errstr, p); 871 portlist[0] = strdup(p); 872 if (portlist[0] == NULL) 873 err(1, NULL); 874 } 875 } 876 877 /* 878 * udptest() 879 * Do a few writes to see if the UDP port is there. 880 * Fails once PF state table is full. 881 */ 882 int 883 udptest(int s) 884 { 885 int i, ret; 886 887 for (i = 0; i <= 3; i++) { 888 if (write(s, "X", 1) == 1) 889 ret = 1; 890 else 891 ret = -1; 892 } 893 return (ret); 894 } 895 896 void 897 set_common_sockopts(int s) 898 { 899 int x = 1; 900 901 if (Sflag) { 902 if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG, 903 &x, sizeof(x)) == -1) 904 err(1, NULL); 905 } 906 if (Dflag) { 907 if (setsockopt(s, SOL_SOCKET, SO_DEBUG, 908 &x, sizeof(x)) == -1) 909 err(1, NULL); 910 } 911 if (Tflag != -1) { 912 if (setsockopt(s, IPPROTO_IP, IP_TOS, 913 &Tflag, sizeof(Tflag)) == -1) 914 err(1, "set IP ToS"); 915 } 916 if (Iflag) { 917 if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, 918 &Iflag, sizeof(Iflag)) == -1) 919 err(1, "set TCP receive buffer size"); 920 } 921 if (Oflag) { 922 if (setsockopt(s, SOL_SOCKET, SO_SNDBUF, 923 &Oflag, sizeof(Oflag)) == -1) 924 err(1, "set TCP send buffer size"); 925 } 926 } 927 928 int 929 map_tos(char *s, int *val) 930 { 931 /* DiffServ Codepoints and other TOS mappings */ 932 const struct toskeywords { 933 const char *keyword; 934 int val; 935 } *t, toskeywords[] = { 936 { "af11", IPTOS_DSCP_AF11 }, 937 { "af12", IPTOS_DSCP_AF12 }, 938 { "af13", IPTOS_DSCP_AF13 }, 939 { "af21", IPTOS_DSCP_AF21 }, 940 { "af22", IPTOS_DSCP_AF22 }, 941 { "af23", IPTOS_DSCP_AF23 }, 942 { "af31", IPTOS_DSCP_AF31 }, 943 { "af32", IPTOS_DSCP_AF32 }, 944 { "af33", IPTOS_DSCP_AF33 }, 945 { "af41", IPTOS_DSCP_AF41 }, 946 { "af42", IPTOS_DSCP_AF42 }, 947 { "af43", IPTOS_DSCP_AF43 }, 948 { "critical", IPTOS_PREC_CRITIC_ECP }, 949 { "cs0", IPTOS_DSCP_CS0 }, 950 { "cs1", IPTOS_DSCP_CS1 }, 951 { "cs2", IPTOS_DSCP_CS2 }, 952 { "cs3", IPTOS_DSCP_CS3 }, 953 { "cs4", IPTOS_DSCP_CS4 }, 954 { "cs5", IPTOS_DSCP_CS5 }, 955 { "cs6", IPTOS_DSCP_CS6 }, 956 { "cs7", IPTOS_DSCP_CS7 }, 957 { "ef", IPTOS_DSCP_EF }, 958 { "inetcontrol", IPTOS_PREC_INTERNETCONTROL }, 959 { "lowdelay", IPTOS_LOWDELAY }, 960 { "netcontrol", IPTOS_PREC_NETCONTROL }, 961 { "reliability", IPTOS_RELIABILITY }, 962 { "throughput", IPTOS_THROUGHPUT }, 963 { NULL, -1 }, 964 }; 965 966 for (t = toskeywords; t->keyword != NULL; t++) { 967 if (strcmp(s, t->keyword) == 0) { 968 *val = t->val; 969 return (1); 970 } 971 } 972 973 return (0); 974 } 975 976 void 977 report_connect(const struct sockaddr *sa, socklen_t salen) 978 { 979 char remote_host[NI_MAXHOST]; 980 char remote_port[NI_MAXSERV]; 981 int herr; 982 int flags = NI_NUMERICSERV; 983 984 if (nflag) 985 flags |= NI_NUMERICHOST; 986 987 if ((herr = getnameinfo(sa, salen, 988 remote_host, sizeof(remote_host), 989 remote_port, sizeof(remote_port), 990 flags)) != 0) { 991 if (herr == EAI_SYSTEM) 992 err(1, "getnameinfo"); 993 else 994 errx(1, "getnameinfo: %s", gai_strerror(herr)); 995 } 996 997 fprintf(stderr, 998 "Connection from %s %s " 999 "received!\n", remote_host, remote_port); 1000 } 1001 1002 void 1003 help(void) 1004 { 1005 usage(0); 1006 fprintf(stderr, "\tCommand Summary:\n\ 1007 \t-4 Use IPv4\n\ 1008 \t-6 Use IPv6\n\ 1009 \t-D Enable the debug socket option\n\ 1010 \t-d Detach from stdin\n\ 1011 \t-h This help text\n\ 1012 \t-I length TCP receive buffer length\n\ 1013 \t-i secs\t Delay interval for lines sent, ports scanned\n\ 1014 \t-k Keep inbound sockets open for multiple connects\n\ 1015 \t-l Listen mode, for inbound connects\n\ 1016 \t-n Suppress name/port resolutions\n\ 1017 \t-O length TCP send buffer length\n\ 1018 \t-P proxyuser\tUsername for proxy authentication\n\ 1019 \t-p port\t Specify local port for remote connects\n\ 1020 \t-r Randomize remote ports\n\ 1021 \t-S Enable the TCP MD5 signature option\n\ 1022 \t-s addr\t Local source address\n\ 1023 \t-T toskeyword\tSet IP Type of Service\n\ 1024 \t-t Answer TELNET negotiation\n\ 1025 \t-U Use UNIX domain socket\n\ 1026 \t-u UDP mode\n\ 1027 \t-V rtable Specify alternate routing table\n\ 1028 \t-v Verbose\n\ 1029 \t-w secs\t Timeout for connects and final net reads\n\ 1030 \t-X proto Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\ 1031 \t-x addr[:port]\tSpecify proxy address and port\n\ 1032 \t-z Zero-I/O mode [used for scanning]\n\ 1033 Port numbers can be individual or ranges: lo-hi [inclusive]\n"); 1034 exit(1); 1035 } 1036 1037 void 1038 usage(int ret) 1039 { 1040 fprintf(stderr, 1041 "usage: nc [-46DdhklnrStUuvz] [-I length] [-i interval] [-O length]\n" 1042 "\t [-P proxy_username] [-p source_port] [-s source] [-T ToS]\n" 1043 "\t [-V rtable] [-w timeout] [-X proxy_protocol]\n" 1044 "\t [-x proxy_address[:port]] [destination] [port]\n"); 1045 if (ret) 1046 exit(1); 1047 } 1048