1 /* $OpenBSD: netcat.c,v 1.105 2012/02/09 06:25:35 lum 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 * $FreeBSD$ 29 */ 30 31 /* 32 * Re-written nc(1) for OpenBSD. Original implementation by 33 * *Hobbit* <hobbit@avian.org>. 34 */ 35 36 #include <sys/limits.h> 37 #include <sys/types.h> 38 #include <sys/socket.h> 39 #include <sys/sysctl.h> 40 #include <sys/time.h> 41 #include <sys/un.h> 42 43 #include <netinet/in.h> 44 #include <netinet/in_systm.h> 45 #ifdef IPSEC 46 #include <netipsec/ipsec.h> 47 #endif 48 #include <netinet/tcp.h> 49 #include <netinet/ip.h> 50 #include <arpa/telnet.h> 51 52 #include <err.h> 53 #include <errno.h> 54 #include <getopt.h> 55 #include <netdb.h> 56 #include <poll.h> 57 #include <stdarg.h> 58 #include <stdio.h> 59 #include <stdlib.h> 60 #include <string.h> 61 #include <unistd.h> 62 #include <fcntl.h> 63 #include <limits.h> 64 #include "atomicio.h" 65 66 #ifndef SUN_LEN 67 #define SUN_LEN(su) \ 68 (sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path)) 69 #endif 70 71 #define PORT_MAX 65535 72 #define PORT_MAX_LEN 6 73 #define UNIX_DG_TMP_SOCKET_SIZE 19 74 75 /* Command Line Options */ 76 int dflag; /* detached, no stdin */ 77 unsigned int iflag; /* Interval Flag */ 78 int jflag; /* use jumbo frames if we can */ 79 int kflag; /* More than one connect */ 80 int lflag; /* Bind to local port */ 81 int nflag; /* Don't do name look up */ 82 int FreeBSD_Oflag; /* Do not use TCP options */ 83 char *Pflag; /* Proxy username */ 84 char *pflag; /* Localport flag */ 85 int rflag; /* Random ports flag */ 86 char *sflag; /* Source Address */ 87 int tflag; /* Telnet Emulation */ 88 int uflag; /* UDP - Default to TCP */ 89 int vflag; /* Verbosity */ 90 int xflag; /* Socks proxy */ 91 int zflag; /* Port Scan Flag */ 92 int Dflag; /* sodebug */ 93 int Iflag; /* TCP receive buffer size */ 94 int Oflag; /* TCP send buffer size */ 95 int Sflag; /* TCP MD5 signature option */ 96 int Tflag = -1; /* IP Type of Service */ 97 u_int rtableid; 98 99 int timeout = -1; 100 int family = AF_UNSPEC; 101 char *portlist[PORT_MAX+1]; 102 char *unix_dg_tmp_socket; 103 104 void atelnet(int, unsigned char *, unsigned int); 105 void build_ports(char *); 106 void help(void); 107 int local_listen(char *, char *, struct addrinfo); 108 void readwrite(int); 109 int remote_connect(const char *, const char *, struct addrinfo); 110 int timeout_connect(int, const struct sockaddr *, socklen_t); 111 int socks_connect(const char *, const char *, struct addrinfo, 112 const char *, const char *, struct addrinfo, int, const char *); 113 int udptest(int); 114 int unix_bind(char *); 115 int unix_connect(char *); 116 int unix_listen(char *); 117 void set_common_sockopts(int); 118 int map_tos(char *, int *); 119 void usage(int); 120 121 #ifdef IPSEC 122 void add_ipsec_policy(int, char *); 123 124 char *ipsec_policy[2]; 125 #endif 126 127 int 128 main(int argc, char *argv[]) 129 { 130 int ch, s, ret, socksv, ipsec_count; 131 int numfibs; 132 size_t intsize = sizeof(int); 133 char *host, *uport; 134 struct addrinfo hints; 135 struct servent *sv; 136 socklen_t len; 137 struct sockaddr_storage cliaddr; 138 char *proxy; 139 const char *errstr, *proxyhost = "", *proxyport = NULL; 140 struct addrinfo proxyhints; 141 char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE]; 142 struct option longopts[] = { 143 { "no-tcpopt", no_argument, &FreeBSD_Oflag, 1 }, 144 { NULL, 0, NULL, 0 } 145 }; 146 147 ret = 1; 148 ipsec_count = 0; 149 s = 0; 150 socksv = 5; 151 host = NULL; 152 uport = NULL; 153 sv = NULL; 154 155 while ((ch = getopt_long(argc, argv, 156 "46DdEe:hI:i:jklnoO:P:p:rSs:tT:UuV:vw:X:x:z", 157 longopts, NULL)) != -1) { 158 switch (ch) { 159 case '4': 160 family = AF_INET; 161 break; 162 case '6': 163 family = AF_INET6; 164 break; 165 case 'U': 166 family = AF_UNIX; 167 break; 168 case 'X': 169 if (strcasecmp(optarg, "connect") == 0) 170 socksv = -1; /* HTTP proxy CONNECT */ 171 else if (strcmp(optarg, "4") == 0) 172 socksv = 4; /* SOCKS v.4 */ 173 else if (strcmp(optarg, "5") == 0) 174 socksv = 5; /* SOCKS v.5 */ 175 else 176 errx(1, "unsupported proxy protocol"); 177 break; 178 case 'd': 179 dflag = 1; 180 break; 181 case 'e': 182 #ifdef IPSEC 183 ipsec_policy[ipsec_count++ % 2] = optarg; 184 #else 185 errx(1, "IPsec support unavailable."); 186 #endif 187 break; 188 case 'E': 189 #ifdef IPSEC 190 ipsec_policy[0] = "in ipsec esp/transport//require"; 191 ipsec_policy[1] = "out ipsec esp/transport//require"; 192 #else 193 errx(1, "IPsec support unavailable."); 194 #endif 195 break; 196 case 'h': 197 help(); 198 break; 199 case 'i': 200 iflag = strtonum(optarg, 0, UINT_MAX, &errstr); 201 if (errstr) 202 errx(1, "interval %s: %s", errstr, optarg); 203 break; 204 #ifdef SO_JUMBO 205 case 'j': 206 jflag = 1; 207 break; 208 #endif 209 case 'k': 210 kflag = 1; 211 break; 212 case 'l': 213 lflag = 1; 214 break; 215 case 'n': 216 nflag = 1; 217 break; 218 case 'o': 219 fprintf(stderr, "option -o is deprecated.\n"); 220 break; 221 case 'P': 222 Pflag = optarg; 223 break; 224 case 'p': 225 pflag = optarg; 226 break; 227 case 'r': 228 rflag = 1; 229 break; 230 case 's': 231 sflag = optarg; 232 break; 233 case 't': 234 tflag = 1; 235 break; 236 case 'u': 237 uflag = 1; 238 break; 239 case 'V': 240 if (sysctlbyname("net.fibs", &numfibs, &intsize, NULL, 0) == -1) 241 errx(1, "Multiple FIBS not supported"); 242 rtableid = (unsigned int)strtonum(optarg, 0, 243 numfibs - 1, &errstr); 244 if (errstr) 245 errx(1, "rtable %s: %s", errstr, optarg); 246 break; 247 case 'v': 248 vflag = 1; 249 break; 250 case 'w': 251 timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr); 252 if (errstr) 253 errx(1, "timeout %s: %s", errstr, optarg); 254 timeout *= 1000; 255 break; 256 case 'x': 257 xflag = 1; 258 if ((proxy = strdup(optarg)) == NULL) 259 err(1, NULL); 260 break; 261 case 'z': 262 zflag = 1; 263 break; 264 case 'D': 265 Dflag = 1; 266 break; 267 case 'I': 268 Iflag = strtonum(optarg, 1, 65536 << 14, &errstr); 269 if (errstr != NULL) 270 errx(1, "TCP receive window %s: %s", 271 errstr, optarg); 272 break; 273 case 'O': 274 Oflag = strtonum(optarg, 1, 65536 << 14, &errstr); 275 if (errstr != NULL) { 276 if (strcmp(errstr, "invalid") != 0) 277 errx(1, "TCP send window %s: %s", 278 errstr, optarg); 279 } 280 break; 281 case 'S': 282 Sflag = 1; 283 break; 284 case 'T': 285 errstr = NULL; 286 errno = 0; 287 if (map_tos(optarg, &Tflag)) 288 break; 289 if (strlen(optarg) > 1 && optarg[0] == '0' && 290 optarg[1] == 'x') 291 Tflag = (int)strtol(optarg, NULL, 16); 292 else 293 Tflag = (int)strtonum(optarg, 0, 255, 294 &errstr); 295 if (Tflag < 0 || Tflag > 255 || errstr || errno) 296 errx(1, "illegal tos value %s", optarg); 297 break; 298 default: 299 usage(1); 300 } 301 } 302 argc -= optind; 303 argv += optind; 304 305 /* Cruft to make sure options are clean, and used properly. */ 306 if (argv[0] && !argv[1] && family == AF_UNIX) { 307 host = argv[0]; 308 uport = NULL; 309 } else if (argv[0] && !argv[1]) { 310 if (!lflag) 311 usage(1); 312 uport = argv[0]; 313 host = NULL; 314 } else if (argv[0] && argv[1]) { 315 host = argv[0]; 316 uport = argv[1]; 317 } else 318 usage(1); 319 320 if (lflag && sflag) 321 errx(1, "cannot use -s and -l"); 322 if (lflag && pflag) 323 errx(1, "cannot use -p and -l"); 324 if (lflag && zflag) 325 errx(1, "cannot use -z and -l"); 326 if (!lflag && kflag) 327 errx(1, "must use -l with -k"); 328 329 /* Get name of temporary socket for unix datagram client */ 330 if ((family == AF_UNIX) && uflag && !lflag) { 331 if (sflag) { 332 unix_dg_tmp_socket = sflag; 333 } else { 334 strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX", 335 UNIX_DG_TMP_SOCKET_SIZE); 336 if (mktemp(unix_dg_tmp_socket_buf) == NULL) 337 err(1, "mktemp"); 338 unix_dg_tmp_socket = unix_dg_tmp_socket_buf; 339 } 340 } 341 342 /* Initialize addrinfo structure. */ 343 if (family != AF_UNIX) { 344 memset(&hints, 0, sizeof(struct addrinfo)); 345 hints.ai_family = family; 346 hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; 347 hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; 348 if (nflag) 349 hints.ai_flags |= AI_NUMERICHOST; 350 } 351 352 if (xflag) { 353 if (uflag) 354 errx(1, "no proxy support for UDP mode"); 355 356 if (lflag) 357 errx(1, "no proxy support for listen"); 358 359 if (family == AF_UNIX) 360 errx(1, "no proxy support for unix sockets"); 361 362 /* XXX IPv6 transport to proxy would probably work */ 363 if (family == AF_INET6) 364 errx(1, "no proxy support for IPv6"); 365 366 if (sflag) 367 errx(1, "no proxy support for local source address"); 368 369 proxyhost = strsep(&proxy, ":"); 370 proxyport = proxy; 371 372 memset(&proxyhints, 0, sizeof(struct addrinfo)); 373 proxyhints.ai_family = family; 374 proxyhints.ai_socktype = SOCK_STREAM; 375 proxyhints.ai_protocol = IPPROTO_TCP; 376 if (nflag) 377 proxyhints.ai_flags |= AI_NUMERICHOST; 378 } 379 380 if (lflag) { 381 int connfd; 382 ret = 0; 383 384 if (family == AF_UNIX) { 385 if (uflag) 386 s = unix_bind(host); 387 else 388 s = unix_listen(host); 389 } 390 391 /* Allow only one connection at a time, but stay alive. */ 392 for (;;) { 393 if (family != AF_UNIX) 394 s = local_listen(host, uport, hints); 395 if (s < 0) 396 err(1, NULL); 397 /* 398 * For UDP, we will use recvfrom() initially 399 * to wait for a caller, then use the regular 400 * functions to talk to the caller. 401 */ 402 if (uflag) { 403 int rv, plen; 404 char buf[16384]; 405 struct sockaddr_storage z; 406 407 len = sizeof(z); 408 plen = jflag ? 16384 : 2048; 409 rv = recvfrom(s, buf, plen, MSG_PEEK, 410 (struct sockaddr *)&z, &len); 411 if (rv < 0) 412 err(1, "recvfrom"); 413 414 rv = connect(s, (struct sockaddr *)&z, len); 415 if (rv < 0) 416 err(1, "connect"); 417 418 readwrite(s); 419 } else { 420 len = sizeof(cliaddr); 421 connfd = accept(s, (struct sockaddr *)&cliaddr, 422 &len); 423 readwrite(connfd); 424 close(connfd); 425 } 426 427 if (family != AF_UNIX) 428 close(s); 429 else if (uflag) { 430 if (connect(s, NULL, 0) < 0) 431 err(1, "connect"); 432 } 433 434 if (!kflag) 435 break; 436 } 437 } else if (family == AF_UNIX) { 438 ret = 0; 439 440 if ((s = unix_connect(host)) > 0 && !zflag) { 441 readwrite(s); 442 close(s); 443 } else 444 ret = 1; 445 446 if (uflag) 447 unlink(unix_dg_tmp_socket); 448 exit(ret); 449 450 } else { 451 int i = 0; 452 453 /* Construct the portlist[] array. */ 454 build_ports(uport); 455 456 /* Cycle through portlist, connecting to each port. */ 457 for (i = 0; portlist[i] != NULL; i++) { 458 if (s) 459 close(s); 460 461 if (xflag) 462 s = socks_connect(host, portlist[i], hints, 463 proxyhost, proxyport, proxyhints, socksv, 464 Pflag); 465 else 466 s = remote_connect(host, portlist[i], hints); 467 468 if (s < 0) 469 continue; 470 471 ret = 0; 472 if (vflag || zflag) { 473 /* For UDP, make sure we are connected. */ 474 if (uflag) { 475 if (udptest(s) == -1) { 476 ret = 1; 477 continue; 478 } 479 } 480 481 /* Don't look up port if -n. */ 482 if (nflag) 483 sv = NULL; 484 else { 485 sv = getservbyport( 486 ntohs(atoi(portlist[i])), 487 uflag ? "udp" : "tcp"); 488 } 489 490 fprintf(stderr, 491 "Connection to %s %s port [%s/%s] " 492 "succeeded!\n", host, portlist[i], 493 uflag ? "udp" : "tcp", 494 sv ? sv->s_name : "*"); 495 } 496 if (!zflag) 497 readwrite(s); 498 } 499 } 500 501 if (s) 502 close(s); 503 504 exit(ret); 505 } 506 507 /* 508 * unix_bind() 509 * Returns a unix socket bound to the given path 510 */ 511 int 512 unix_bind(char *path) 513 { 514 struct sockaddr_un sun; 515 int s; 516 517 /* Create unix domain socket. */ 518 if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM, 519 0)) < 0) 520 return (-1); 521 522 memset(&sun, 0, sizeof(struct sockaddr_un)); 523 sun.sun_family = AF_UNIX; 524 525 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= 526 sizeof(sun.sun_path)) { 527 close(s); 528 errno = ENAMETOOLONG; 529 return (-1); 530 } 531 532 if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { 533 close(s); 534 return (-1); 535 } 536 return (s); 537 } 538 539 /* 540 * unix_connect() 541 * Returns a socket connected to a local unix socket. Returns -1 on failure. 542 */ 543 int 544 unix_connect(char *path) 545 { 546 struct sockaddr_un sun; 547 int s; 548 549 if (uflag) { 550 if ((s = unix_bind(unix_dg_tmp_socket)) < 0) 551 return (-1); 552 } else { 553 if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) 554 return (-1); 555 } 556 (void)fcntl(s, F_SETFD, 1); 557 558 memset(&sun, 0, sizeof(struct sockaddr_un)); 559 sun.sun_family = AF_UNIX; 560 561 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= 562 sizeof(sun.sun_path)) { 563 close(s); 564 errno = ENAMETOOLONG; 565 return (-1); 566 } 567 if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { 568 close(s); 569 return (-1); 570 } 571 return (s); 572 573 } 574 575 /* 576 * unix_listen() 577 * Create a unix domain socket, and listen on it. 578 */ 579 int 580 unix_listen(char *path) 581 { 582 int s; 583 if ((s = unix_bind(path)) < 0) 584 return (-1); 585 586 if (listen(s, 5) < 0) { 587 close(s); 588 return (-1); 589 } 590 return (s); 591 } 592 593 /* 594 * remote_connect() 595 * Returns a socket connected to a remote host. Properly binds to a local 596 * port or source address if needed. Returns -1 on failure. 597 */ 598 int 599 remote_connect(const char *host, const char *port, struct addrinfo hints) 600 { 601 struct addrinfo *res, *res0; 602 int s, error, on = 1; 603 604 if ((error = getaddrinfo(host, port, &hints, &res))) 605 errx(1, "getaddrinfo: %s", gai_strerror(error)); 606 607 res0 = res; 608 do { 609 if ((s = socket(res0->ai_family, res0->ai_socktype, 610 res0->ai_protocol)) < 0) 611 continue; 612 #ifdef IPSEC 613 if (ipsec_policy[0] != NULL) 614 add_ipsec_policy(s, ipsec_policy[0]); 615 if (ipsec_policy[1] != NULL) 616 add_ipsec_policy(s, ipsec_policy[1]); 617 #endif 618 619 if (rtableid) { 620 if (setsockopt(s, SOL_SOCKET, SO_SETFIB, &rtableid, 621 sizeof(rtableid)) == -1) 622 err(1, "setsockopt(.., SO_SETFIB, %u, ..)", 623 rtableid); 624 } 625 626 /* Bind to a local port or source address if specified. */ 627 if (sflag || pflag) { 628 struct addrinfo ahints, *ares; 629 630 /* try IP_BINDANY, but don't insist */ 631 setsockopt(s, IPPROTO_IP, IP_BINDANY, &on, sizeof(on)); 632 memset(&ahints, 0, sizeof(struct addrinfo)); 633 ahints.ai_family = res0->ai_family; 634 ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; 635 ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; 636 ahints.ai_flags = AI_PASSIVE; 637 if ((error = getaddrinfo(sflag, pflag, &ahints, &ares))) 638 errx(1, "getaddrinfo: %s", gai_strerror(error)); 639 640 if (bind(s, (struct sockaddr *)ares->ai_addr, 641 ares->ai_addrlen) < 0) 642 errx(1, "bind failed: %s", strerror(errno)); 643 freeaddrinfo(ares); 644 } 645 646 set_common_sockopts(s); 647 648 if (timeout_connect(s, res0->ai_addr, res0->ai_addrlen) == 0) 649 break; 650 else if (vflag) 651 warn("connect to %s port %s (%s) failed", host, port, 652 uflag ? "udp" : "tcp"); 653 654 close(s); 655 s = -1; 656 } while ((res0 = res0->ai_next) != NULL); 657 658 freeaddrinfo(res); 659 660 return (s); 661 } 662 663 int 664 timeout_connect(int s, const struct sockaddr *name, socklen_t namelen) 665 { 666 struct pollfd pfd; 667 socklen_t optlen; 668 int flags, optval; 669 int ret; 670 671 if (timeout != -1) { 672 flags = fcntl(s, F_GETFL, 0); 673 if (fcntl(s, F_SETFL, flags | O_NONBLOCK) == -1) 674 err(1, "set non-blocking mode"); 675 } 676 677 if ((ret = connect(s, name, namelen)) != 0 && errno == EINPROGRESS) { 678 pfd.fd = s; 679 pfd.events = POLLOUT; 680 if ((ret = poll(&pfd, 1, timeout)) == 1) { 681 optlen = sizeof(optval); 682 if ((ret = getsockopt(s, SOL_SOCKET, SO_ERROR, 683 &optval, &optlen)) == 0) { 684 errno = optval; 685 ret = optval == 0 ? 0 : -1; 686 } 687 } else if (ret == 0) { 688 errno = ETIMEDOUT; 689 ret = -1; 690 } else 691 err(1, "poll failed"); 692 } 693 694 if (timeout != -1 && fcntl(s, F_SETFL, flags) == -1) 695 err(1, "restoring flags"); 696 697 return (ret); 698 } 699 700 /* 701 * local_listen() 702 * Returns a socket listening on a local port, binds to specified source 703 * address. Returns -1 on failure. 704 */ 705 int 706 local_listen(char *host, char *port, struct addrinfo hints) 707 { 708 struct addrinfo *res, *res0; 709 int s, ret, x = 1; 710 int error; 711 712 /* Allow nodename to be null. */ 713 hints.ai_flags |= AI_PASSIVE; 714 715 /* 716 * In the case of binding to a wildcard address 717 * default to binding to an ipv4 address. 718 */ 719 if (host == NULL && hints.ai_family == AF_UNSPEC) 720 hints.ai_family = AF_INET; 721 722 if ((error = getaddrinfo(host, port, &hints, &res))) 723 errx(1, "getaddrinfo: %s", gai_strerror(error)); 724 725 res0 = res; 726 do { 727 if ((s = socket(res0->ai_family, res0->ai_socktype, 728 res0->ai_protocol)) < 0) 729 continue; 730 731 if (rtableid) { 732 ret = setsockopt(s, SOL_SOCKET, SO_SETFIB, &rtableid, 733 sizeof(rtableid)); 734 if (ret == -1) 735 err(1, "setsockopt(.., SO_SETFIB, %u, ..)", 736 rtableid); 737 } 738 739 ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x)); 740 if (ret == -1) 741 err(1, NULL); 742 #ifdef IPSEC 743 if (ipsec_policy[0] != NULL) 744 add_ipsec_policy(s, ipsec_policy[0]); 745 if (ipsec_policy[1] != NULL) 746 add_ipsec_policy(s, ipsec_policy[1]); 747 #endif 748 if (FreeBSD_Oflag) { 749 if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT, 750 &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1) 751 err(1, "disable TCP options"); 752 } 753 754 if (bind(s, (struct sockaddr *)res0->ai_addr, 755 res0->ai_addrlen) == 0) 756 break; 757 758 close(s); 759 s = -1; 760 } while ((res0 = res0->ai_next) != NULL); 761 762 if (!uflag && s != -1) { 763 if (listen(s, 1) < 0) 764 err(1, "listen"); 765 } 766 767 freeaddrinfo(res); 768 769 return (s); 770 } 771 772 /* 773 * readwrite() 774 * Loop that polls on the network file descriptor and stdin. 775 */ 776 void 777 readwrite(int nfd) 778 { 779 struct pollfd pfd[2]; 780 unsigned char buf[16384]; 781 int n, wfd = fileno(stdin); 782 int lfd = fileno(stdout); 783 int plen; 784 785 plen = jflag ? 16384 : 2048; 786 787 /* Setup Network FD */ 788 pfd[0].fd = nfd; 789 pfd[0].events = POLLIN; 790 791 /* Set up STDIN FD. */ 792 pfd[1].fd = wfd; 793 pfd[1].events = POLLIN; 794 795 while (pfd[0].fd != -1) { 796 if (iflag) 797 sleep(iflag); 798 799 if ((n = poll(pfd, 2 - dflag, timeout)) < 0) { 800 close(nfd); 801 err(1, "Polling Error"); 802 } 803 804 if (n == 0) 805 return; 806 807 if (pfd[0].revents & POLLIN) { 808 if ((n = read(nfd, buf, plen)) < 0) 809 return; 810 else if (n == 0) { 811 shutdown(nfd, SHUT_RD); 812 pfd[0].fd = -1; 813 pfd[0].events = 0; 814 } else { 815 if (tflag) 816 atelnet(nfd, buf, n); 817 if (atomicio(vwrite, lfd, buf, n) != n) 818 return; 819 } 820 } 821 822 if (!dflag && pfd[1].revents & POLLIN) { 823 if ((n = read(wfd, buf, plen)) < 0) 824 return; 825 else if (n == 0) { 826 shutdown(nfd, SHUT_WR); 827 pfd[1].fd = -1; 828 pfd[1].events = 0; 829 } else { 830 if (atomicio(vwrite, nfd, buf, n) != n) 831 return; 832 } 833 } 834 } 835 } 836 837 /* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */ 838 void 839 atelnet(int nfd, unsigned char *buf, unsigned int size) 840 { 841 unsigned char *p, *end; 842 unsigned char obuf[4]; 843 844 if (size < 3) 845 return; 846 end = buf + size - 2; 847 848 for (p = buf; p < end; p++) { 849 if (*p != IAC) 850 continue; 851 852 obuf[0] = IAC; 853 p++; 854 if ((*p == WILL) || (*p == WONT)) 855 obuf[1] = DONT; 856 else if ((*p == DO) || (*p == DONT)) 857 obuf[1] = WONT; 858 else 859 continue; 860 861 p++; 862 obuf[2] = *p; 863 if (atomicio(vwrite, nfd, obuf, 3) != 3) 864 warn("Write Error!"); 865 } 866 } 867 868 /* 869 * build_ports() 870 * Build an array of ports in portlist[], listing each port 871 * that we should try to connect to. 872 */ 873 void 874 build_ports(char *p) 875 { 876 const char *errstr; 877 char *n; 878 int hi, lo, cp; 879 int x = 0; 880 881 if ((n = strchr(p, '-')) != NULL) { 882 *n = '\0'; 883 n++; 884 885 /* Make sure the ports are in order: lowest->highest. */ 886 hi = strtonum(n, 1, PORT_MAX, &errstr); 887 if (errstr) 888 errx(1, "port number %s: %s", errstr, n); 889 lo = strtonum(p, 1, PORT_MAX, &errstr); 890 if (errstr) 891 errx(1, "port number %s: %s", errstr, p); 892 893 if (lo > hi) { 894 cp = hi; 895 hi = lo; 896 lo = cp; 897 } 898 899 /* Load ports sequentially. */ 900 for (cp = lo; cp <= hi; cp++) { 901 portlist[x] = calloc(1, PORT_MAX_LEN); 902 if (portlist[x] == NULL) 903 err(1, NULL); 904 snprintf(portlist[x], PORT_MAX_LEN, "%d", cp); 905 x++; 906 } 907 908 /* Randomly swap ports. */ 909 if (rflag) { 910 int y; 911 char *c; 912 913 for (x = 0; x <= (hi - lo); x++) { 914 y = (arc4random() & 0xFFFF) % (hi - lo); 915 c = portlist[x]; 916 portlist[x] = portlist[y]; 917 portlist[y] = c; 918 } 919 } 920 } else { 921 hi = strtonum(p, 1, PORT_MAX, &errstr); 922 if (errstr) 923 errx(1, "port number %s: %s", errstr, p); 924 portlist[0] = strdup(p); 925 if (portlist[0] == NULL) 926 err(1, NULL); 927 } 928 } 929 930 /* 931 * udptest() 932 * Do a few writes to see if the UDP port is there. 933 * Fails once PF state table is full. 934 */ 935 int 936 udptest(int s) 937 { 938 int i, ret; 939 940 for (i = 0; i <= 3; i++) { 941 if (write(s, "X", 1) == 1) 942 ret = 1; 943 else 944 ret = -1; 945 } 946 return (ret); 947 } 948 949 void 950 set_common_sockopts(int s) 951 { 952 int x = 1; 953 954 if (Sflag) { 955 if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG, 956 &x, sizeof(x)) == -1) 957 err(1, NULL); 958 } 959 if (Dflag) { 960 if (setsockopt(s, SOL_SOCKET, SO_DEBUG, 961 &x, sizeof(x)) == -1) 962 err(1, NULL); 963 } 964 #ifdef SO_JUMBO 965 if (jflag) { 966 if (setsockopt(s, SOL_SOCKET, SO_JUMBO, 967 &x, sizeof(x)) == -1) 968 err(1, NULL); 969 } 970 #endif 971 if (Tflag != -1) { 972 if (setsockopt(s, IPPROTO_IP, IP_TOS, 973 &Tflag, sizeof(Tflag)) == -1) 974 err(1, "set IP ToS"); 975 } 976 if (Iflag) { 977 if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, 978 &Iflag, sizeof(Iflag)) == -1) 979 err(1, "set TCP receive buffer size"); 980 } 981 if (Oflag) { 982 if (setsockopt(s, SOL_SOCKET, SO_SNDBUF, 983 &Oflag, sizeof(Oflag)) == -1) 984 err(1, "set TCP send buffer size"); 985 } 986 if (FreeBSD_Oflag) { 987 if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT, 988 &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1) 989 err(1, "disable TCP options"); 990 } 991 } 992 993 int 994 map_tos(char *s, int *val) 995 { 996 /* DiffServ Codepoints and other TOS mappings */ 997 const struct toskeywords { 998 const char *keyword; 999 int val; 1000 } *t, toskeywords[] = { 1001 { "af11", IPTOS_DSCP_AF11 }, 1002 { "af12", IPTOS_DSCP_AF12 }, 1003 { "af13", IPTOS_DSCP_AF13 }, 1004 { "af21", IPTOS_DSCP_AF21 }, 1005 { "af22", IPTOS_DSCP_AF22 }, 1006 { "af23", IPTOS_DSCP_AF23 }, 1007 { "af31", IPTOS_DSCP_AF31 }, 1008 { "af32", IPTOS_DSCP_AF32 }, 1009 { "af33", IPTOS_DSCP_AF33 }, 1010 { "af41", IPTOS_DSCP_AF41 }, 1011 { "af42", IPTOS_DSCP_AF42 }, 1012 { "af43", IPTOS_DSCP_AF43 }, 1013 { "critical", IPTOS_PREC_CRITIC_ECP }, 1014 { "cs0", IPTOS_DSCP_CS0 }, 1015 { "cs1", IPTOS_DSCP_CS1 }, 1016 { "cs2", IPTOS_DSCP_CS2 }, 1017 { "cs3", IPTOS_DSCP_CS3 }, 1018 { "cs4", IPTOS_DSCP_CS4 }, 1019 { "cs5", IPTOS_DSCP_CS5 }, 1020 { "cs6", IPTOS_DSCP_CS6 }, 1021 { "cs7", IPTOS_DSCP_CS7 }, 1022 { "ef", IPTOS_DSCP_EF }, 1023 { "inetcontrol", IPTOS_PREC_INTERNETCONTROL }, 1024 { "lowdelay", IPTOS_LOWDELAY }, 1025 { "netcontrol", IPTOS_PREC_NETCONTROL }, 1026 { "reliability", IPTOS_RELIABILITY }, 1027 { "throughput", IPTOS_THROUGHPUT }, 1028 { NULL, -1 }, 1029 }; 1030 1031 for (t = toskeywords; t->keyword != NULL; t++) { 1032 if (strcmp(s, t->keyword) == 0) { 1033 *val = t->val; 1034 return (1); 1035 } 1036 } 1037 1038 return (0); 1039 } 1040 1041 void 1042 help(void) 1043 { 1044 usage(0); 1045 fprintf(stderr, "\tCommand Summary:\n\ 1046 \t-4 Use IPv4\n\ 1047 \t-6 Use IPv6\n\ 1048 \t-D Enable the debug socket option\n\ 1049 \t-d Detach from stdin\n"); 1050 #ifdef IPSEC 1051 fprintf(stderr, "\ 1052 \t-E Use IPsec ESP\n\ 1053 \t-e policy Use specified IPsec policy\n"); 1054 #endif 1055 fprintf(stderr, "\ 1056 \t-h This help text\n\ 1057 \t-I length TCP receive buffer length\n\ 1058 \t-i secs\t Delay interval for lines sent, ports scanned\n\ 1059 \t-k Keep inbound sockets open for multiple connects\n\ 1060 \t-l Listen mode, for inbound connects\n\ 1061 \t-n Suppress name/port resolutions\n\ 1062 \t--no-tcpopt Disable TCP options\n\ 1063 \t-O length TCP send buffer length\n\ 1064 \t-P proxyuser\tUsername for proxy authentication\n\ 1065 \t-p port\t Specify local port for remote connects\n\ 1066 \t-r Randomize remote ports\n\ 1067 \t-S Enable the TCP MD5 signature option\n\ 1068 \t-s addr\t Local source address\n\ 1069 \t-T toskeyword\tSet IP Type of Service\n\ 1070 \t-t Answer TELNET negotiation\n\ 1071 \t-U Use UNIX domain socket\n\ 1072 \t-u UDP mode\n\ 1073 \t-V rtable Specify alternate routing table\n\ 1074 \t-v Verbose\n\ 1075 \t-w secs\t Timeout for connects and final net reads\n\ 1076 \t-X proto Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\ 1077 \t-x addr[:port]\tSpecify proxy address and port\n\ 1078 \t-z Zero-I/O mode [used for scanning]\n\ 1079 Port numbers can be individual or ranges: lo-hi [inclusive]\n"); 1080 #ifdef IPSEC 1081 fprintf(stderr, "See ipsec_set_policy(3) for -e argument format\n"); 1082 #endif 1083 exit(1); 1084 } 1085 1086 #ifdef IPSEC 1087 void 1088 add_ipsec_policy(int s, char *policy) 1089 { 1090 char *raw; 1091 int e; 1092 1093 raw = ipsec_set_policy(policy, strlen(policy)); 1094 if (raw == NULL) 1095 errx(1, "ipsec_set_policy `%s': %s", policy, 1096 ipsec_strerror()); 1097 e = setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, raw, 1098 ipsec_get_policylen(raw)); 1099 if (e < 0) 1100 err(1, "ipsec policy cannot be configured"); 1101 free(raw); 1102 if (vflag) 1103 fprintf(stderr, "ipsec policy configured: `%s'\n", policy); 1104 return; 1105 } 1106 #endif /* IPSEC */ 1107 1108 void 1109 usage(int ret) 1110 { 1111 fprintf(stderr, 1112 #ifdef IPSEC 1113 "usage: nc [-46DdEhklnrStUuvz] [-e policy] [-I length] [-i interval] [-O length]\n" 1114 #else 1115 "usage: nc [-46DdhklnrStUuvz] [-I length] [-i interval] [-O length]\n" 1116 #endif 1117 "\t [-P proxy_username] [-p source_port] [-s source] [-T ToS]\n" 1118 "\t [-V rtable] [-w timeout] [-X proxy_protocol]\n" 1119 "\t [-x proxy_address[:port]] [destination] [port]\n"); 1120 if (ret) 1121 exit(1); 1122 } 1123