1 /* $OpenBSD: netcat.c,v 1.100 2011/01/09 22:16:46 jeremy 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 socks_connect(const char *, const char *, struct addrinfo, 111 const char *, const char *, struct addrinfo, int, const char *); 112 int udptest(int); 113 int unix_bind(char *); 114 int unix_connect(char *); 115 int unix_listen(char *); 116 void set_common_sockopts(int); 117 int parse_iptos(char *); 118 void usage(int); 119 120 #ifdef IPSEC 121 void add_ipsec_policy(int, char *); 122 123 char *ipsec_policy[2]; 124 #endif 125 126 int 127 main(int argc, char *argv[]) 128 { 129 int ch, s, ret, socksv, ipsec_count; 130 int numfibs; 131 size_t intsize = sizeof(int); 132 char *host, *uport; 133 struct addrinfo hints; 134 struct servent *sv; 135 socklen_t len; 136 struct sockaddr_storage cliaddr; 137 char *proxy; 138 const char *errstr, *proxyhost = "", *proxyport = NULL; 139 struct addrinfo proxyhints; 140 char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE]; 141 struct option longopts[] = { 142 { "no-tcpopt", no_argument, &FreeBSD_Oflag, 1 }, 143 { NULL, 0, NULL, 0 } 144 }; 145 146 ret = 1; 147 ipsec_count = 0; 148 s = 0; 149 socksv = 5; 150 host = NULL; 151 uport = NULL; 152 sv = NULL; 153 154 while ((ch = getopt_long(argc, argv, 155 "46DdEe:hI:i:jklnoO:P:p:rSs:tT:UuV:vw:X:x:z", 156 longopts, NULL)) != -1) { 157 switch (ch) { 158 case '4': 159 family = AF_INET; 160 break; 161 case '6': 162 family = AF_INET6; 163 break; 164 case 'U': 165 family = AF_UNIX; 166 break; 167 case 'X': 168 if (strcasecmp(optarg, "connect") == 0) 169 socksv = -1; /* HTTP proxy CONNECT */ 170 else if (strcmp(optarg, "4") == 0) 171 socksv = 4; /* SOCKS v.4 */ 172 else if (strcmp(optarg, "5") == 0) 173 socksv = 5; /* SOCKS v.5 */ 174 else 175 errx(1, "unsupported proxy protocol"); 176 break; 177 case 'd': 178 dflag = 1; 179 break; 180 case 'e': 181 #ifdef IPSEC 182 ipsec_policy[ipsec_count++ % 2] = optarg; 183 #else 184 errx(1, "IPsec support unavailable."); 185 #endif 186 break; 187 case 'E': 188 #ifdef IPSEC 189 ipsec_policy[0] = "in ipsec esp/transport//require"; 190 ipsec_policy[1] = "out ipsec esp/transport//require"; 191 #else 192 errx(1, "IPsec support unavailable."); 193 #endif 194 break; 195 case 'h': 196 help(); 197 break; 198 case 'i': 199 iflag = strtonum(optarg, 0, UINT_MAX, &errstr); 200 if (errstr) 201 errx(1, "interval %s: %s", errstr, optarg); 202 break; 203 #ifdef SO_JUMBO 204 case 'j': 205 jflag = 1; 206 break; 207 #endif 208 case 'k': 209 kflag = 1; 210 break; 211 case 'l': 212 lflag = 1; 213 break; 214 case 'n': 215 nflag = 1; 216 break; 217 case 'o': 218 fprintf(stderr, "option -o is deprecated.\n"); 219 break; 220 case 'P': 221 Pflag = optarg; 222 break; 223 case 'p': 224 pflag = optarg; 225 break; 226 case 'r': 227 rflag = 1; 228 break; 229 case 's': 230 sflag = optarg; 231 break; 232 case 't': 233 tflag = 1; 234 break; 235 case 'u': 236 uflag = 1; 237 break; 238 case 'V': 239 if (sysctlbyname("net.fibs", &numfibs, &intsize, NULL, 0) == -1) 240 errx(1, "Multiple FIBS not supported"); 241 rtableid = (unsigned int)strtonum(optarg, 0, 242 numfibs - 1, &errstr); 243 if (errstr) 244 errx(1, "rtable %s: %s", errstr, optarg); 245 break; 246 case 'v': 247 vflag = 1; 248 break; 249 case 'w': 250 timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr); 251 if (errstr) 252 errx(1, "timeout %s: %s", errstr, optarg); 253 timeout *= 1000; 254 break; 255 case 'x': 256 xflag = 1; 257 if ((proxy = strdup(optarg)) == NULL) 258 err(1, NULL); 259 break; 260 case 'z': 261 zflag = 1; 262 break; 263 case 'D': 264 Dflag = 1; 265 break; 266 case 'I': 267 Iflag = strtonum(optarg, 1, 65536 << 14, &errstr); 268 if (errstr != NULL) 269 errx(1, "TCP receive window %s: %s", 270 errstr, optarg); 271 break; 272 case 'O': 273 Oflag = strtonum(optarg, 1, 65536 << 14, &errstr); 274 if (errstr != NULL) { 275 if (strcmp(errstr, "invalid") != 0) 276 errx(1, "TCP send window %s: %s", 277 errstr, optarg); 278 } 279 break; 280 case 'S': 281 Sflag = 1; 282 break; 283 case 'T': 284 Tflag = parse_iptos(optarg); 285 break; 286 default: 287 usage(1); 288 } 289 } 290 argc -= optind; 291 argv += optind; 292 293 /* Cruft to make sure options are clean, and used properly. */ 294 if (argv[0] && !argv[1] && family == AF_UNIX) { 295 host = argv[0]; 296 uport = NULL; 297 } else if (argv[0] && !argv[1]) { 298 if (!lflag) 299 usage(1); 300 uport = argv[0]; 301 host = NULL; 302 } else if (argv[0] && argv[1]) { 303 host = argv[0]; 304 uport = argv[1]; 305 } else 306 usage(1); 307 308 if (lflag && sflag) 309 errx(1, "cannot use -s and -l"); 310 if (lflag && pflag) 311 errx(1, "cannot use -p and -l"); 312 if (lflag && zflag) 313 errx(1, "cannot use -z and -l"); 314 if (!lflag && kflag) 315 errx(1, "must use -l with -k"); 316 317 /* Get name of temporary socket for unix datagram client */ 318 if ((family == AF_UNIX) && uflag && !lflag) { 319 if (sflag) { 320 unix_dg_tmp_socket = sflag; 321 } else { 322 strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX", 323 UNIX_DG_TMP_SOCKET_SIZE); 324 if (mktemp(unix_dg_tmp_socket_buf) == NULL) 325 err(1, "mktemp"); 326 unix_dg_tmp_socket = unix_dg_tmp_socket_buf; 327 } 328 } 329 330 /* Initialize addrinfo structure. */ 331 if (family != AF_UNIX) { 332 memset(&hints, 0, sizeof(struct addrinfo)); 333 hints.ai_family = family; 334 hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; 335 hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; 336 if (nflag) 337 hints.ai_flags |= AI_NUMERICHOST; 338 } 339 340 if (xflag) { 341 if (uflag) 342 errx(1, "no proxy support for UDP mode"); 343 344 if (lflag) 345 errx(1, "no proxy support for listen"); 346 347 if (family == AF_UNIX) 348 errx(1, "no proxy support for unix sockets"); 349 350 /* XXX IPv6 transport to proxy would probably work */ 351 if (family == AF_INET6) 352 errx(1, "no proxy support for IPv6"); 353 354 if (sflag) 355 errx(1, "no proxy support for local source address"); 356 357 proxyhost = strsep(&proxy, ":"); 358 proxyport = proxy; 359 360 memset(&proxyhints, 0, sizeof(struct addrinfo)); 361 proxyhints.ai_family = family; 362 proxyhints.ai_socktype = SOCK_STREAM; 363 proxyhints.ai_protocol = IPPROTO_TCP; 364 if (nflag) 365 proxyhints.ai_flags |= AI_NUMERICHOST; 366 } 367 368 if (lflag) { 369 int connfd; 370 ret = 0; 371 372 if (family == AF_UNIX) { 373 if (uflag) 374 s = unix_bind(host); 375 else 376 s = unix_listen(host); 377 } 378 379 /* Allow only one connection at a time, but stay alive. */ 380 for (;;) { 381 if (family != AF_UNIX) 382 s = local_listen(host, uport, hints); 383 if (s < 0) 384 err(1, NULL); 385 /* 386 * For UDP, we will use recvfrom() initially 387 * to wait for a caller, then use the regular 388 * functions to talk to the caller. 389 */ 390 if (uflag) { 391 int rv, plen; 392 char buf[16384]; 393 struct sockaddr_storage z; 394 395 len = sizeof(z); 396 plen = jflag ? 16384 : 2048; 397 rv = recvfrom(s, buf, plen, MSG_PEEK, 398 (struct sockaddr *)&z, &len); 399 if (rv < 0) 400 err(1, "recvfrom"); 401 402 rv = connect(s, (struct sockaddr *)&z, len); 403 if (rv < 0) 404 err(1, "connect"); 405 406 readwrite(s); 407 } else { 408 len = sizeof(cliaddr); 409 connfd = accept(s, (struct sockaddr *)&cliaddr, 410 &len); 411 readwrite(connfd); 412 close(connfd); 413 } 414 415 if (family != AF_UNIX) 416 close(s); 417 else if (uflag) { 418 if (connect(s, NULL, 0) < 0) 419 err(1, "connect"); 420 } 421 422 if (!kflag) 423 break; 424 } 425 } else if (family == AF_UNIX) { 426 ret = 0; 427 428 if ((s = unix_connect(host)) > 0 && !zflag) { 429 readwrite(s); 430 close(s); 431 } else 432 ret = 1; 433 434 if (uflag) 435 unlink(unix_dg_tmp_socket); 436 exit(ret); 437 438 } else { 439 int i = 0; 440 441 /* Construct the portlist[] array. */ 442 build_ports(uport); 443 444 /* Cycle through portlist, connecting to each port. */ 445 for (i = 0; portlist[i] != NULL; i++) { 446 if (s) 447 close(s); 448 449 if (xflag) 450 s = socks_connect(host, portlist[i], hints, 451 proxyhost, proxyport, proxyhints, socksv, 452 Pflag); 453 else 454 s = remote_connect(host, portlist[i], hints); 455 456 if (s < 0) 457 continue; 458 459 ret = 0; 460 if (vflag || zflag) { 461 /* For UDP, make sure we are connected. */ 462 if (uflag) { 463 if (udptest(s) == -1) { 464 ret = 1; 465 continue; 466 } 467 } 468 469 /* Don't look up port if -n. */ 470 if (nflag) 471 sv = NULL; 472 else { 473 sv = getservbyport( 474 ntohs(atoi(portlist[i])), 475 uflag ? "udp" : "tcp"); 476 } 477 478 fprintf(stderr, 479 "Connection to %s %s port [%s/%s] " 480 "succeeded!\n", host, portlist[i], 481 uflag ? "udp" : "tcp", 482 sv ? sv->s_name : "*"); 483 } 484 if (!zflag) 485 readwrite(s); 486 } 487 } 488 489 if (s) 490 close(s); 491 492 exit(ret); 493 } 494 495 /* 496 * unix_bind() 497 * Returns a unix socket bound to the given path 498 */ 499 int 500 unix_bind(char *path) 501 { 502 struct sockaddr_un sun; 503 int s; 504 505 /* Create unix domain socket. */ 506 if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM, 507 0)) < 0) 508 return (-1); 509 510 memset(&sun, 0, sizeof(struct sockaddr_un)); 511 sun.sun_family = AF_UNIX; 512 513 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= 514 sizeof(sun.sun_path)) { 515 close(s); 516 errno = ENAMETOOLONG; 517 return (-1); 518 } 519 520 if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { 521 close(s); 522 return (-1); 523 } 524 return (s); 525 } 526 527 /* 528 * unix_connect() 529 * Returns a socket connected to a local unix socket. Returns -1 on failure. 530 */ 531 int 532 unix_connect(char *path) 533 { 534 struct sockaddr_un sun; 535 int s; 536 537 if (uflag) { 538 if ((s = unix_bind(unix_dg_tmp_socket)) < 0) 539 return (-1); 540 } else { 541 if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) 542 return (-1); 543 } 544 (void)fcntl(s, F_SETFD, 1); 545 546 memset(&sun, 0, sizeof(struct sockaddr_un)); 547 sun.sun_family = AF_UNIX; 548 549 if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= 550 sizeof(sun.sun_path)) { 551 close(s); 552 errno = ENAMETOOLONG; 553 return (-1); 554 } 555 if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { 556 close(s); 557 return (-1); 558 } 559 return (s); 560 561 } 562 563 /* 564 * unix_listen() 565 * Create a unix domain socket, and listen on it. 566 */ 567 int 568 unix_listen(char *path) 569 { 570 int s; 571 if ((s = unix_bind(path)) < 0) 572 return (-1); 573 574 if (listen(s, 5) < 0) { 575 close(s); 576 return (-1); 577 } 578 return (s); 579 } 580 581 /* 582 * remote_connect() 583 * Returns a socket connected to a remote host. Properly binds to a local 584 * port or source address if needed. Returns -1 on failure. 585 */ 586 int 587 remote_connect(const char *host, const char *port, struct addrinfo hints) 588 { 589 struct addrinfo *res, *res0; 590 int s, error, on = 1; 591 592 if ((error = getaddrinfo(host, port, &hints, &res))) 593 errx(1, "getaddrinfo: %s", gai_strerror(error)); 594 595 res0 = res; 596 do { 597 if ((s = socket(res0->ai_family, res0->ai_socktype, 598 res0->ai_protocol)) < 0) 599 continue; 600 #ifdef IPSEC 601 if (ipsec_policy[0] != NULL) 602 add_ipsec_policy(s, ipsec_policy[0]); 603 if (ipsec_policy[1] != NULL) 604 add_ipsec_policy(s, ipsec_policy[1]); 605 #endif 606 607 if (rtableid) { 608 if (setfib(rtableid) == -1) 609 err(1, "setfib"); 610 } 611 612 /* Bind to a local port or source address if specified. */ 613 if (sflag || pflag) { 614 struct addrinfo ahints, *ares; 615 616 /* try IP_BINDANY, but don't insist */ 617 setsockopt(s, IPPROTO_IP, IP_BINDANY, &on, sizeof(on)); 618 memset(&ahints, 0, sizeof(struct addrinfo)); 619 ahints.ai_family = res0->ai_family; 620 ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; 621 ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; 622 ahints.ai_flags = AI_PASSIVE; 623 if ((error = getaddrinfo(sflag, pflag, &ahints, &ares))) 624 errx(1, "getaddrinfo: %s", gai_strerror(error)); 625 626 if (bind(s, (struct sockaddr *)ares->ai_addr, 627 ares->ai_addrlen) < 0) 628 errx(1, "bind failed: %s", strerror(errno)); 629 freeaddrinfo(ares); 630 } 631 632 set_common_sockopts(s); 633 634 if (connect(s, res0->ai_addr, res0->ai_addrlen) == 0) 635 break; 636 else if (vflag) 637 warn("connect to %s port %s (%s) failed", host, port, 638 uflag ? "udp" : "tcp"); 639 640 close(s); 641 s = -1; 642 } while ((res0 = res0->ai_next) != NULL); 643 644 freeaddrinfo(res); 645 646 return (s); 647 } 648 649 /* 650 * local_listen() 651 * Returns a socket listening on a local port, binds to specified source 652 * address. Returns -1 on failure. 653 */ 654 int 655 local_listen(char *host, char *port, struct addrinfo hints) 656 { 657 struct addrinfo *res, *res0; 658 int s, ret, x = 1; 659 int error; 660 661 /* Allow nodename to be null. */ 662 hints.ai_flags |= AI_PASSIVE; 663 664 /* 665 * In the case of binding to a wildcard address 666 * default to binding to an ipv4 address. 667 */ 668 if (host == NULL && hints.ai_family == AF_UNSPEC) 669 hints.ai_family = AF_INET; 670 671 if ((error = getaddrinfo(host, port, &hints, &res))) 672 errx(1, "getaddrinfo: %s", gai_strerror(error)); 673 674 res0 = res; 675 do { 676 if ((s = socket(res0->ai_family, res0->ai_socktype, 677 res0->ai_protocol)) < 0) 678 continue; 679 680 if (rtableid) { 681 if (setfib(rtableid) == -1) 682 err(1, "setfib"); 683 } 684 685 ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x)); 686 if (ret == -1) 687 err(1, NULL); 688 #ifdef IPSEC 689 if (ipsec_policy[0] != NULL) 690 add_ipsec_policy(s, ipsec_policy[0]); 691 if (ipsec_policy[1] != NULL) 692 add_ipsec_policy(s, ipsec_policy[1]); 693 #endif 694 if (FreeBSD_Oflag) { 695 if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT, 696 &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1) 697 err(1, "disable TCP options"); 698 } 699 700 if (bind(s, (struct sockaddr *)res0->ai_addr, 701 res0->ai_addrlen) == 0) 702 break; 703 704 close(s); 705 s = -1; 706 } while ((res0 = res0->ai_next) != NULL); 707 708 if (!uflag && s != -1) { 709 if (listen(s, 1) < 0) 710 err(1, "listen"); 711 } 712 713 freeaddrinfo(res); 714 715 return (s); 716 } 717 718 /* 719 * readwrite() 720 * Loop that polls on the network file descriptor and stdin. 721 */ 722 void 723 readwrite(int nfd) 724 { 725 struct pollfd pfd[2]; 726 unsigned char buf[16384]; 727 int n, wfd = fileno(stdin); 728 int lfd = fileno(stdout); 729 int plen; 730 731 plen = jflag ? 16384 : 2048; 732 733 /* Setup Network FD */ 734 pfd[0].fd = nfd; 735 pfd[0].events = POLLIN; 736 737 /* Set up STDIN FD. */ 738 pfd[1].fd = wfd; 739 pfd[1].events = POLLIN; 740 741 while (pfd[0].fd != -1) { 742 if (iflag) 743 sleep(iflag); 744 745 if ((n = poll(pfd, 2 - dflag, timeout)) < 0) { 746 close(nfd); 747 err(1, "Polling Error"); 748 } 749 750 if (n == 0) 751 return; 752 753 if (pfd[0].revents & POLLIN) { 754 if ((n = read(nfd, buf, plen)) < 0) 755 return; 756 else if (n == 0) { 757 shutdown(nfd, SHUT_RD); 758 pfd[0].fd = -1; 759 pfd[0].events = 0; 760 } else { 761 if (tflag) 762 atelnet(nfd, buf, n); 763 if (atomicio(vwrite, lfd, buf, n) != n) 764 return; 765 } 766 } 767 768 if (!dflag && pfd[1].revents & POLLIN) { 769 if ((n = read(wfd, buf, plen)) < 0) 770 return; 771 else if (n == 0) { 772 shutdown(nfd, SHUT_WR); 773 pfd[1].fd = -1; 774 pfd[1].events = 0; 775 } else { 776 if (atomicio(vwrite, nfd, buf, n) != n) 777 return; 778 } 779 } 780 } 781 } 782 783 /* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */ 784 void 785 atelnet(int nfd, unsigned char *buf, unsigned int size) 786 { 787 unsigned char *p, *end; 788 unsigned char obuf[4]; 789 790 if (size < 3) 791 return; 792 end = buf + size - 2; 793 794 for (p = buf; p < end; p++) { 795 if (*p != IAC) 796 continue; 797 798 obuf[0] = IAC; 799 p++; 800 if ((*p == WILL) || (*p == WONT)) 801 obuf[1] = DONT; 802 else if ((*p == DO) || (*p == DONT)) 803 obuf[1] = WONT; 804 else 805 continue; 806 807 p++; 808 obuf[2] = *p; 809 if (atomicio(vwrite, nfd, obuf, 3) != 3) 810 warn("Write Error!"); 811 } 812 } 813 814 /* 815 * build_ports() 816 * Build an array or ports in portlist[], listing each port 817 * that we should try to connect to. 818 */ 819 void 820 build_ports(char *p) 821 { 822 const char *errstr; 823 char *n; 824 int hi, lo, cp; 825 int x = 0; 826 827 if ((n = strchr(p, '-')) != NULL) { 828 if (lflag) 829 errx(1, "Cannot use -l with multiple ports!"); 830 831 *n = '\0'; 832 n++; 833 834 /* Make sure the ports are in order: lowest->highest. */ 835 hi = strtonum(n, 1, PORT_MAX, &errstr); 836 if (errstr) 837 errx(1, "port number %s: %s", errstr, n); 838 lo = strtonum(p, 1, PORT_MAX, &errstr); 839 if (errstr) 840 errx(1, "port number %s: %s", errstr, p); 841 842 if (lo > hi) { 843 cp = hi; 844 hi = lo; 845 lo = cp; 846 } 847 848 /* Load ports sequentially. */ 849 for (cp = lo; cp <= hi; cp++) { 850 portlist[x] = calloc(1, PORT_MAX_LEN); 851 if (portlist[x] == NULL) 852 err(1, NULL); 853 snprintf(portlist[x], PORT_MAX_LEN, "%d", cp); 854 x++; 855 } 856 857 /* Randomly swap ports. */ 858 if (rflag) { 859 int y; 860 char *c; 861 862 for (x = 0; x <= (hi - lo); x++) { 863 y = (arc4random() & 0xFFFF) % (hi - lo); 864 c = portlist[x]; 865 portlist[x] = portlist[y]; 866 portlist[y] = c; 867 } 868 } 869 } else { 870 hi = strtonum(p, 1, PORT_MAX, &errstr); 871 if (errstr) 872 errx(1, "port number %s: %s", errstr, p); 873 portlist[0] = strdup(p); 874 if (portlist[0] == NULL) 875 err(1, NULL); 876 } 877 } 878 879 /* 880 * udptest() 881 * Do a few writes to see if the UDP port is there. 882 * XXX - Better way of doing this? Doesn't work for IPv6. 883 * Also fails after around 100 ports checked. 884 */ 885 int 886 udptest(int s) 887 { 888 int i, ret; 889 890 for (i = 0; i <= 3; i++) { 891 if (write(s, "X", 1) == 1) 892 ret = 1; 893 else 894 ret = -1; 895 } 896 return (ret); 897 } 898 899 void 900 set_common_sockopts(int s) 901 { 902 int x = 1; 903 904 if (Sflag) { 905 if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG, 906 &x, sizeof(x)) == -1) 907 err(1, NULL); 908 } 909 if (Dflag) { 910 if (setsockopt(s, SOL_SOCKET, SO_DEBUG, 911 &x, sizeof(x)) == -1) 912 err(1, NULL); 913 } 914 #ifdef SO_JUMBO 915 if (jflag) { 916 if (setsockopt(s, SOL_SOCKET, SO_JUMBO, 917 &x, sizeof(x)) == -1) 918 err(1, NULL); 919 } 920 #endif 921 if (Tflag != -1) { 922 if (setsockopt(s, IPPROTO_IP, IP_TOS, 923 &Tflag, sizeof(Tflag)) == -1) 924 err(1, "set IP ToS"); 925 } 926 if (Iflag) { 927 if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, 928 &Iflag, sizeof(Iflag)) == -1) 929 err(1, "set TCP receive buffer size"); 930 } 931 if (Oflag) { 932 if (setsockopt(s, SOL_SOCKET, SO_SNDBUF, 933 &Oflag, sizeof(Oflag)) == -1) 934 err(1, "set TCP send buffer size"); 935 } 936 if (FreeBSD_Oflag) { 937 if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT, 938 &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1) 939 err(1, "disable TCP options"); 940 } 941 } 942 943 int 944 parse_iptos(char *s) 945 { 946 int tos = -1; 947 948 if (strcmp(s, "lowdelay") == 0) 949 return (IPTOS_LOWDELAY); 950 if (strcmp(s, "throughput") == 0) 951 return (IPTOS_THROUGHPUT); 952 if (strcmp(s, "reliability") == 0) 953 return (IPTOS_RELIABILITY); 954 955 if (sscanf(s, "0x%x", &tos) != 1 || tos < 0 || tos > 0xff) 956 errx(1, "invalid IP Type of Service"); 957 return (tos); 958 } 959 960 void 961 help(void) 962 { 963 usage(0); 964 fprintf(stderr, "\tCommand Summary:\n\ 965 \t-4 Use IPv4\n\ 966 \t-6 Use IPv6\n\ 967 \t-D Enable the debug socket option\n\ 968 \t-d Detach from stdin\n"); 969 #ifdef IPSEC 970 fprintf(stderr, "\ 971 \t-E Use IPsec ESP\n\ 972 \t-e policy Use specified IPsec policy\n"); 973 #endif 974 fprintf(stderr, "\ 975 \t-h This help text\n\ 976 \t-I length TCP receive buffer length\n\ 977 \t-i secs\t Delay interval for lines sent, ports scanned\n\ 978 \t-k Keep inbound sockets open for multiple connects\n\ 979 \t-l Listen mode, for inbound connects\n\ 980 \t-n Suppress name/port resolutions\n\ 981 \t--no-tcpopt Disable TCP options\n\ 982 \t-O length TCP send buffer length\n\ 983 \t-P proxyuser\tUsername for proxy authentication\n\ 984 \t-p port\t Specify local port for remote connects\n\ 985 \t-r Randomize remote ports\n\ 986 \t-S Enable the TCP MD5 signature option\n\ 987 \t-s addr\t Local source address\n\ 988 \t-T ToS\t Set IP Type of Service\n\ 989 \t-t Answer TELNET negotiation\n\ 990 \t-U Use UNIX domain socket\n\ 991 \t-u UDP mode\n\ 992 \t-V rtable Specify alternate routing table\n\ 993 \t-v Verbose\n\ 994 \t-w secs\t Timeout for connects and final net reads\n\ 995 \t-X proto Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\ 996 \t-x addr[:port]\tSpecify proxy address and port\n\ 997 \t-z Zero-I/O mode [used for scanning]\n\ 998 Port numbers can be individual or ranges: lo-hi [inclusive]\n"); 999 #ifdef IPSEC 1000 fprintf(stderr, "See ipsec_set_policy(3) for -e argument format\n"); 1001 #endif 1002 exit(1); 1003 } 1004 1005 #ifdef IPSEC 1006 void 1007 add_ipsec_policy(int s, char *policy) 1008 { 1009 char *raw; 1010 int e; 1011 1012 raw = ipsec_set_policy(policy, strlen(policy)); 1013 if (raw == NULL) 1014 errx(1, "ipsec_set_policy `%s': %s", policy, 1015 ipsec_strerror()); 1016 e = setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, raw, 1017 ipsec_get_policylen(raw)); 1018 if (e < 0) 1019 err(1, "ipsec policy cannot be configured"); 1020 free(raw); 1021 if (vflag) 1022 fprintf(stderr, "ipsec policy configured: `%s'\n", policy); 1023 return; 1024 } 1025 #endif /* IPSEC */ 1026 1027 void 1028 usage(int ret) 1029 { 1030 fprintf(stderr, 1031 #ifdef IPSEC 1032 "usage: nc [-46DdEhklnrStUuvz] [-e policy] [-I length] [-i interval] [-O length]\n" 1033 #else 1034 "usage: nc [-46DdhklnrStUuvz] [-I length] [-i interval] [-O length]\n" 1035 #endif 1036 "\t [-P proxy_username] [-p source_port] [-s source] [-T ToS]\n" 1037 "\t [-V rtable] [-w timeout] [-X proxy_protocol]\n" 1038 "\t [-x proxy_address[:port]] [destination] [port]\n"); 1039 if (ret) 1040 exit(1); 1041 } 1042