/* $OpenBSD: netcat.c,v 1.126 2014/10/30 16:08:31 tedu Exp $ */ /* * Copyright (c) 2001 Eric Jackson * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* * Re-written nc(1) for OpenBSD. Original implementation by * *Hobbit* . */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "atomicio.h" #ifndef SUN_LEN #define SUN_LEN(su) \ (sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path)) #endif #define PORT_MAX 65535 #define PORT_MAX_LEN 6 #define UNIX_DG_TMP_SOCKET_SIZE 19 #define POLL_STDIN 0 #define POLL_NETOUT 1 #define POLL_NETIN 2 #define POLL_STDOUT 3 #define BUFSIZE 16384 /* Command Line Options */ int dflag; /* detached, no stdin */ int Fflag; /* fdpass sock to stdout */ unsigned int iflag; /* Interval Flag */ int kflag; /* More than one connect */ int lflag; /* Bind to local port */ int Nflag; /* shutdown() network socket */ int nflag; /* Don't do name look up */ char *Pflag; /* Proxy username */ char *pflag; /* Localport flag */ int rflag; /* Random ports flag */ char *sflag; /* Source Address */ int tflag; /* Telnet Emulation */ int uflag; /* UDP - Default to TCP */ int vflag; /* Verbosity */ int xflag; /* Socks proxy */ int zflag; /* Port Scan Flag */ int Dflag; /* sodebug */ int Iflag; /* TCP receive buffer size */ int Oflag; /* TCP send buffer size */ int Sflag; /* TCP MD5 signature option */ int Tflag = -1; /* IP Type of Service */ int rtableid = -1; int timeout = -1; int family = AF_UNSPEC; char *portlist[PORT_MAX+1]; char *unix_dg_tmp_socket; void atelnet(int, unsigned char *, unsigned int); void build_ports(char *); void help(void); int local_listen(char *, char *, struct addrinfo); void readwrite(int); void fdpass(int nfd) __attribute__((noreturn)); int remote_connect(const char *, const char *, struct addrinfo); int timeout_connect(int, const struct sockaddr *, socklen_t); int socks_connect(const char *, const char *, struct addrinfo, const char *, const char *, struct addrinfo, int, const char *); int udptest(int); int unix_bind(char *); int unix_connect(char *); int unix_listen(char *); void set_common_sockopts(int); int map_tos(char *, int *); void report_connect(const struct sockaddr *, socklen_t); void usage(int); ssize_t drainbuf(int, unsigned char *, size_t *); ssize_t fillbuf(int, unsigned char *, size_t *); int main(int argc, char *argv[]) { int ch, s, ret, socksv; char *host, *uport; struct addrinfo hints; struct servent *sv; socklen_t len; struct sockaddr_storage cliaddr; char *proxy; const char *errstr, *proxyhost = "", *proxyport = NULL; struct addrinfo proxyhints; char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE]; ret = 1; s = 0; socksv = 5; host = NULL; uport = NULL; sv = NULL; while ((ch = getopt(argc, argv, "46DdFhI:i:klNnO:P:p:rSs:tT:UuV:vw:X:x:z")) != -1) { switch (ch) { case '4': family = AF_INET; break; case '6': family = AF_INET6; break; case 'U': family = AF_UNIX; break; case 'X': if (strcasecmp(optarg, "connect") == 0) socksv = -1; /* HTTP proxy CONNECT */ else if (strcmp(optarg, "4") == 0) socksv = 4; /* SOCKS v.4 */ else if (strcmp(optarg, "5") == 0) socksv = 5; /* SOCKS v.5 */ else errx(1, "unsupported proxy protocol"); break; case 'd': dflag = 1; break; case 'F': Fflag = 1; break; case 'h': help(); break; case 'i': iflag = strtonum(optarg, 0, UINT_MAX, &errstr); if (errstr) errx(1, "interval %s: %s", errstr, optarg); break; case 'k': kflag = 1; break; case 'l': lflag = 1; break; case 'N': Nflag = 1; break; case 'n': nflag = 1; break; case 'P': Pflag = optarg; break; case 'p': pflag = optarg; break; case 'r': rflag = 1; break; case 's': sflag = optarg; break; case 't': tflag = 1; break; case 'u': uflag = 1; break; case 'V': rtableid = (int)strtonum(optarg, 0, RT_TABLEID_MAX, &errstr); if (errstr) errx(1, "rtable %s: %s", errstr, optarg); break; case 'v': vflag = 1; break; case 'w': timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr); if (errstr) errx(1, "timeout %s: %s", errstr, optarg); timeout *= 1000; break; case 'x': xflag = 1; if ((proxy = strdup(optarg)) == NULL) err(1, NULL); break; case 'z': zflag = 1; break; case 'D': Dflag = 1; break; case 'I': Iflag = strtonum(optarg, 1, 65536 << 14, &errstr); if (errstr != NULL) errx(1, "TCP receive window %s: %s", errstr, optarg); break; case 'O': Oflag = strtonum(optarg, 1, 65536 << 14, &errstr); if (errstr != NULL) errx(1, "TCP send window %s: %s", errstr, optarg); break; case 'S': Sflag = 1; break; case 'T': errstr = NULL; errno = 0; if (map_tos(optarg, &Tflag)) break; if (strlen(optarg) > 1 && optarg[0] == '0' && optarg[1] == 'x') Tflag = (int)strtol(optarg, NULL, 16); else Tflag = (int)strtonum(optarg, 0, 255, &errstr); if (Tflag < 0 || Tflag > 255 || errstr || errno) errx(1, "illegal tos value %s", optarg); break; default: usage(1); } } argc -= optind; argv += optind; /* Cruft to make sure options are clean, and used properly. */ if (argv[0] && !argv[1] && family == AF_UNIX) { host = argv[0]; uport = NULL; } else if (argv[0] && !argv[1]) { if (!lflag) usage(1); uport = argv[0]; host = NULL; } else if (argv[0] && argv[1]) { host = argv[0]; uport = argv[1]; } else usage(1); if (lflag && sflag) errx(1, "cannot use -s and -l"); if (lflag && pflag) errx(1, "cannot use -p and -l"); if (lflag && zflag) errx(1, "cannot use -z and -l"); if (!lflag && kflag) errx(1, "must use -l with -k"); /* Get name of temporary socket for unix datagram client */ if ((family == AF_UNIX) && uflag && !lflag) { if (sflag) { unix_dg_tmp_socket = sflag; } else { strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX", UNIX_DG_TMP_SOCKET_SIZE); if (mktemp(unix_dg_tmp_socket_buf) == NULL) err(1, "mktemp"); unix_dg_tmp_socket = unix_dg_tmp_socket_buf; } } /* Initialize addrinfo structure. */ if (family != AF_UNIX) { memset(&hints, 0, sizeof(struct addrinfo)); hints.ai_family = family; hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; if (nflag) hints.ai_flags |= AI_NUMERICHOST; } if (xflag) { if (uflag) errx(1, "no proxy support for UDP mode"); if (lflag) errx(1, "no proxy support for listen"); if (family == AF_UNIX) errx(1, "no proxy support for unix sockets"); /* XXX IPv6 transport to proxy would probably work */ if (family == AF_INET6) errx(1, "no proxy support for IPv6"); if (sflag) errx(1, "no proxy support for local source address"); proxyhost = strsep(&proxy, ":"); proxyport = proxy; memset(&proxyhints, 0, sizeof(struct addrinfo)); proxyhints.ai_family = family; proxyhints.ai_socktype = SOCK_STREAM; proxyhints.ai_protocol = IPPROTO_TCP; if (nflag) proxyhints.ai_flags |= AI_NUMERICHOST; } if (lflag) { int connfd; ret = 0; if (family == AF_UNIX) { if (uflag) s = unix_bind(host); else s = unix_listen(host); } /* Allow only one connection at a time, but stay alive. */ for (;;) { if (family != AF_UNIX) s = local_listen(host, uport, hints); if (s < 0) err(1, NULL); /* * For UDP and -k, don't connect the socket, let it * receive datagrams from multiple socket pairs. */ if (uflag && kflag) readwrite(s); /* * For UDP and not -k, we will use recvfrom() initially * to wait for a caller, then use the regular functions * to talk to the caller. */ else if (uflag && !kflag) { int rv, plen; char buf[16384]; struct sockaddr_storage z; len = sizeof(z); plen = 2048; rv = recvfrom(s, buf, plen, MSG_PEEK, (struct sockaddr *)&z, &len); if (rv < 0) err(1, "recvfrom"); rv = connect(s, (struct sockaddr *)&z, len); if (rv < 0) err(1, "connect"); if (vflag) report_connect((struct sockaddr *)&z, len); readwrite(s); } else { len = sizeof(cliaddr); connfd = accept(s, (struct sockaddr *)&cliaddr, &len); if (connfd == -1) { /* For now, all errnos are fatal */ err(1, "accept"); } if (vflag) report_connect((struct sockaddr *)&cliaddr, len); readwrite(connfd); close(connfd); } if (family != AF_UNIX) close(s); else if (uflag) { if (connect(s, NULL, 0) < 0) err(1, "connect"); } if (!kflag) break; } } else if (family == AF_UNIX) { ret = 0; if ((s = unix_connect(host)) > 0 && !zflag) { readwrite(s); close(s); } else ret = 1; if (uflag) unlink(unix_dg_tmp_socket); exit(ret); } else { int i = 0; /* Construct the portlist[] array. */ build_ports(uport); /* Cycle through portlist, connecting to each port. */ for (i = 0; portlist[i] != NULL; i++) { if (s) close(s); if (xflag) s = socks_connect(host, portlist[i], hints, proxyhost, proxyport, proxyhints, socksv, Pflag); else s = remote_connect(host, portlist[i], hints); if (s < 0) continue; ret = 0; if (vflag || zflag) { /* For UDP, make sure we are connected. */ if (uflag) { if (udptest(s) == -1) { ret = 1; continue; } } /* Don't look up port if -n. */ if (nflag) sv = NULL; else { sv = getservbyport( ntohs(atoi(portlist[i])), uflag ? "udp" : "tcp"); } fprintf(stderr, "Connection to %s %s port [%s/%s] " "succeeded!\n", host, portlist[i], uflag ? "udp" : "tcp", sv ? sv->s_name : "*"); } if (Fflag) fdpass(s); else if (!zflag) readwrite(s); } } if (s) close(s); exit(ret); } /* * unix_bind() * Returns a unix socket bound to the given path */ int unix_bind(char *path) { struct sockaddr_un sun; int s; /* Create unix domain socket. */ if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM, 0)) < 0) return (-1); memset(&sun, 0, sizeof(struct sockaddr_un)); sun.sun_family = AF_UNIX; if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= sizeof(sun.sun_path)) { close(s); errno = ENAMETOOLONG; return (-1); } if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { close(s); return (-1); } return (s); } /* * unix_connect() * Returns a socket connected to a local unix socket. Returns -1 on failure. */ int unix_connect(char *path) { struct sockaddr_un sun; int s; if (uflag) { if ((s = unix_bind(unix_dg_tmp_socket)) < 0) return (-1); } else { if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) return (-1); } (void)fcntl(s, F_SETFD, FD_CLOEXEC); memset(&sun, 0, sizeof(struct sockaddr_un)); sun.sun_family = AF_UNIX; if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >= sizeof(sun.sun_path)) { close(s); errno = ENAMETOOLONG; return (-1); } if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { close(s); return (-1); } return (s); } /* * unix_listen() * Create a unix domain socket, and listen on it. */ int unix_listen(char *path) { int s; if ((s = unix_bind(path)) < 0) return (-1); if (listen(s, 5) < 0) { close(s); return (-1); } return (s); } /* * remote_connect() * Returns a socket connected to a remote host. Properly binds to a local * port or source address if needed. Returns -1 on failure. */ int remote_connect(const char *host, const char *port, struct addrinfo hints) { struct addrinfo *res, *res0; int s, error, on = 1; if ((error = getaddrinfo(host, port, &hints, &res))) errx(1, "getaddrinfo: %s", gai_strerror(error)); res0 = res; do { if ((s = socket(res0->ai_family, res0->ai_socktype, res0->ai_protocol)) < 0) continue; if (rtableid >= 0 && (setsockopt(s, SOL_SOCKET, SO_RTABLE, &rtableid, sizeof(rtableid)) == -1)) err(1, "setsockopt SO_RTABLE"); /* Bind to a local port or source address if specified. */ if (sflag || pflag) { struct addrinfo ahints, *ares; /* try SO_BINDANY, but don't insist */ setsockopt(s, SOL_SOCKET, SO_BINDANY, &on, sizeof(on)); memset(&ahints, 0, sizeof(struct addrinfo)); ahints.ai_family = res0->ai_family; ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM; ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP; ahints.ai_flags = AI_PASSIVE; if ((error = getaddrinfo(sflag, pflag, &ahints, &ares))) errx(1, "getaddrinfo: %s", gai_strerror(error)); if (bind(s, (struct sockaddr *)ares->ai_addr, ares->ai_addrlen) < 0) err(1, "bind failed"); freeaddrinfo(ares); } set_common_sockopts(s); if (timeout_connect(s, res0->ai_addr, res0->ai_addrlen) == 0) break; else if (vflag) warn("connect to %s port %s (%s) failed", host, port, uflag ? "udp" : "tcp"); close(s); s = -1; } while ((res0 = res0->ai_next) != NULL); freeaddrinfo(res); return (s); } int timeout_connect(int s, const struct sockaddr *name, socklen_t namelen) { struct pollfd pfd; socklen_t optlen; int flags, optval; int ret; if (timeout != -1) { flags = fcntl(s, F_GETFL, 0); if (fcntl(s, F_SETFL, flags | O_NONBLOCK) == -1) err(1, "set non-blocking mode"); } if ((ret = connect(s, name, namelen)) != 0 && errno == EINPROGRESS) { pfd.fd = s; pfd.events = POLLOUT; if ((ret = poll(&pfd, 1, timeout)) == 1) { optlen = sizeof(optval); if ((ret = getsockopt(s, SOL_SOCKET, SO_ERROR, &optval, &optlen)) == 0) { errno = optval; ret = optval == 0 ? 0 : -1; } } else if (ret == 0) { errno = ETIMEDOUT; ret = -1; } else err(1, "poll failed"); } if (timeout != -1 && fcntl(s, F_SETFL, flags) == -1) err(1, "restoring flags"); return (ret); } /* * local_listen() * Returns a socket listening on a local port, binds to specified source * address. Returns -1 on failure. */ int local_listen(char *host, char *port, struct addrinfo hints) { struct addrinfo *res, *res0; int s, ret, x = 1; int error; /* Allow nodename to be null. */ hints.ai_flags |= AI_PASSIVE; /* * In the case of binding to a wildcard address * default to binding to an ipv4 address. */ if (host == NULL && hints.ai_family == AF_UNSPEC) hints.ai_family = AF_INET; if ((error = getaddrinfo(host, port, &hints, &res))) errx(1, "getaddrinfo: %s", gai_strerror(error)); res0 = res; do { if ((s = socket(res0->ai_family, res0->ai_socktype, res0->ai_protocol)) < 0) continue; if (rtableid >= 0 && (setsockopt(s, SOL_SOCKET, SO_RTABLE, &rtableid, sizeof(rtableid)) == -1)) err(1, "setsockopt SO_RTABLE"); ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x)); if (ret == -1) err(1, NULL); set_common_sockopts(s); if (bind(s, (struct sockaddr *)res0->ai_addr, res0->ai_addrlen) == 0) break; close(s); s = -1; } while ((res0 = res0->ai_next) != NULL); if (!uflag && s != -1) { if (listen(s, 1) < 0) err(1, "listen"); } freeaddrinfo(res); return (s); } /* * readwrite() * Loop that polls on the network file descriptor and stdin. */ void readwrite(int net_fd) { struct pollfd pfd[4]; int stdin_fd = STDIN_FILENO; int stdout_fd = STDOUT_FILENO; unsigned char netinbuf[BUFSIZE]; size_t netinbufpos = 0; unsigned char stdinbuf[BUFSIZE]; size_t stdinbufpos = 0; int n, num_fds, flags; ssize_t ret; /* don't read from stdin if requested */ if (dflag) stdin_fd = -1; /* stdin */ pfd[POLL_STDIN].fd = stdin_fd; pfd[POLL_STDIN].events = POLLIN; /* network out */ pfd[POLL_NETOUT].fd = net_fd; pfd[POLL_NETOUT].events = 0; /* network in */ pfd[POLL_NETIN].fd = net_fd; pfd[POLL_NETIN].events = POLLIN; /* stdout */ pfd[POLL_STDOUT].fd = stdout_fd; pfd[POLL_STDOUT].events = 0; while (1) { /* both inputs are gone, buffers are empty, we are done */ if (pfd[POLL_STDIN].fd == -1 && pfd[POLL_NETIN].fd == -1 && stdinbufpos == 0 && netinbufpos == 0) { close(net_fd); return; } /* both outputs are gone, we can't continue */ if (pfd[POLL_NETOUT].fd == -1 && pfd[POLL_STDOUT].fd == -1) { close(net_fd); return; } /* listen and net in gone, queues empty, done */ if (lflag && pfd[POLL_NETIN].fd == -1 && stdinbufpos == 0 && netinbufpos == 0) { close(net_fd); return; } /* help says -i is for "wait between lines sent". We read and * write arbitrary amounts of data, and we don't want to start * scanning for newlines, so this is as good as it gets */ if (iflag) sleep(iflag); /* poll */ num_fds = poll(pfd, 4, timeout); /* treat poll errors */ if (num_fds == -1) { close(net_fd); err(1, "polling error"); } /* timeout happened */ if (num_fds == 0) return; /* treat socket error conditions */ for (n = 0; n < 4; n++) { if (pfd[n].revents & (POLLERR|POLLNVAL)) { pfd[n].fd = -1; } } /* reading is possible after HUP */ if (pfd[POLL_STDIN].events & POLLIN && pfd[POLL_STDIN].revents & POLLHUP && ! (pfd[POLL_STDIN].revents & POLLIN)) pfd[POLL_STDIN].fd = -1; if (pfd[POLL_NETIN].events & POLLIN && pfd[POLL_NETIN].revents & POLLHUP && ! (pfd[POLL_NETIN].revents & POLLIN)) pfd[POLL_NETIN].fd = -1; if (pfd[POLL_NETOUT].revents & POLLHUP) { if (Nflag) shutdown(pfd[POLL_NETOUT].fd, SHUT_WR); pfd[POLL_NETOUT].fd = -1; } /* if HUP, stop watching stdout */ if (pfd[POLL_STDOUT].revents & POLLHUP) pfd[POLL_STDOUT].fd = -1; /* if no net out, stop watching stdin */ if (pfd[POLL_NETOUT].fd == -1) pfd[POLL_STDIN].fd = -1; /* if no stdout, stop watching net in */ if (pfd[POLL_STDOUT].fd == -1) { if (pfd[POLL_NETIN].fd != -1) shutdown(pfd[POLL_NETIN].fd, SHUT_RD); pfd[POLL_NETIN].fd = -1; } /* try to read from stdin */ if (pfd[POLL_STDIN].revents & POLLIN && stdinbufpos < BUFSIZE) { ret = fillbuf(pfd[POLL_STDIN].fd, stdinbuf, &stdinbufpos); /* error or eof on stdin - remove from pfd */ if (ret == 0 || ret == -1) pfd[POLL_STDIN].fd = -1; /* read something - poll net out */ if (stdinbufpos > 0) pfd[POLL_NETOUT].events = POLLOUT; /* filled buffer - remove self from polling */ if (stdinbufpos == BUFSIZE) pfd[POLL_STDIN].events = 0; } /* try to write to network */ if (pfd[POLL_NETOUT].revents & POLLOUT && stdinbufpos > 0) { ret = drainbuf(pfd[POLL_NETOUT].fd, stdinbuf, &stdinbufpos); if (ret == -1) pfd[POLL_NETOUT].fd = -1; /* buffer empty - remove self from polling */ if (stdinbufpos == 0) pfd[POLL_NETOUT].events = 0; /* buffer no longer full - poll stdin again */ if (stdinbufpos < BUFSIZE) pfd[POLL_STDIN].events = POLLIN; } /* try to read from network */ if (pfd[POLL_NETIN].revents & POLLIN && netinbufpos < BUFSIZE) { ret = fillbuf(pfd[POLL_NETIN].fd, netinbuf, &netinbufpos); if (ret == -1) pfd[POLL_NETIN].fd = -1; /* eof on net in - remove from pfd */ if (ret == 0) { shutdown(pfd[POLL_NETIN].fd, SHUT_RD); pfd[POLL_NETIN].fd = -1; } /* read something - poll stdout */ if (netinbufpos > 0) pfd[POLL_STDOUT].events = POLLOUT; /* filled buffer - remove self from polling */ if (netinbufpos == BUFSIZE) pfd[POLL_NETIN].events = 0; /* handle telnet */ if (tflag) atelnet(pfd[POLL_NETIN].fd, netinbuf, netinbufpos); } /* try to write to stdout */ if (pfd[POLL_STDOUT].revents & POLLOUT && netinbufpos > 0) { ret = drainbuf(pfd[POLL_STDOUT].fd, netinbuf, &netinbufpos); if (ret == -1) pfd[POLL_STDOUT].fd = -1; /* buffer empty - remove self from polling */ if (netinbufpos == 0) pfd[POLL_STDOUT].events = 0; /* buffer no longer full - poll net in again */ if (netinbufpos < BUFSIZE) pfd[POLL_NETIN].events = POLLIN; } /* stdin gone and queue empty? */ if (pfd[POLL_STDIN].fd == -1 && stdinbufpos == 0) { if (pfd[POLL_NETOUT].fd != -1 && Nflag) shutdown(pfd[POLL_NETOUT].fd, SHUT_WR); pfd[POLL_NETOUT].fd = -1; } /* net in gone and queue empty? */ if (pfd[POLL_NETIN].fd == -1 && netinbufpos == 0) { pfd[POLL_STDOUT].fd = -1; } } } ssize_t drainbuf(int fd, unsigned char *buf, size_t *bufpos) { ssize_t n; ssize_t adjust; n = write(fd, buf, *bufpos); /* don't treat EAGAIN, EINTR as error */ if (n == -1 && (errno == EAGAIN || errno == EINTR)) n = -2; if (n <= 0) return n; /* adjust buffer */ adjust = *bufpos - n; if (adjust > 0) memmove(buf, buf + n, adjust); *bufpos -= n; return n; } ssize_t fillbuf(int fd, unsigned char *buf, size_t *bufpos) { size_t num = BUFSIZE - *bufpos; ssize_t n; n = read(fd, buf + *bufpos, num); /* don't treat EAGAIN, EINTR as error */ if (n == -1 && (errno == EAGAIN || errno == EINTR)) n = -2; if (n <= 0) return n; *bufpos += n; return n; } /* * fdpass() * Pass the connected file descriptor to stdout and exit. */ void fdpass(int nfd) { struct msghdr mh; union { struct cmsghdr hdr; char buf[CMSG_SPACE(sizeof(int))]; } cmsgbuf; struct cmsghdr *cmsg; struct iovec iov; char c = '\0'; ssize_t r; struct pollfd pfd; /* Avoid obvious stupidity */ if (isatty(STDOUT_FILENO)) errx(1, "Cannot pass file descriptor to tty"); bzero(&mh, sizeof(mh)); bzero(&cmsgbuf, sizeof(cmsgbuf)); bzero(&iov, sizeof(iov)); bzero(&pfd, sizeof(pfd)); mh.msg_control = (caddr_t)&cmsgbuf.buf; mh.msg_controllen = sizeof(cmsgbuf.buf); cmsg = CMSG_FIRSTHDR(&mh); cmsg->cmsg_len = CMSG_LEN(sizeof(int)); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_RIGHTS; *(int *)CMSG_DATA(cmsg) = nfd; iov.iov_base = &c; iov.iov_len = 1; mh.msg_iov = &iov; mh.msg_iovlen = 1; bzero(&pfd, sizeof(pfd)); pfd.fd = STDOUT_FILENO; for (;;) { r = sendmsg(STDOUT_FILENO, &mh, 0); if (r == -1) { if (errno == EAGAIN || errno == EINTR) { pfd.events = POLLOUT; if (poll(&pfd, 1, -1) == -1) err(1, "poll"); continue; } err(1, "sendmsg"); } else if (r == -1) errx(1, "sendmsg: unexpected return value %zd", r); else break; } exit(0); } /* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */ void atelnet(int nfd, unsigned char *buf, unsigned int size) { unsigned char *p, *end; unsigned char obuf[4]; if (size < 3) return; end = buf + size - 2; for (p = buf; p < end; p++) { if (*p != IAC) continue; obuf[0] = IAC; p++; if ((*p == WILL) || (*p == WONT)) obuf[1] = DONT; else if ((*p == DO) || (*p == DONT)) obuf[1] = WONT; else continue; p++; obuf[2] = *p; if (atomicio(vwrite, nfd, obuf, 3) != 3) warn("Write Error!"); } } /* * build_ports() * Build an array of ports in portlist[], listing each port * that we should try to connect to. */ void build_ports(char *p) { const char *errstr; char *n; int hi, lo, cp; int x = 0; if ((n = strchr(p, '-')) != NULL) { *n = '\0'; n++; /* Make sure the ports are in order: lowest->highest. */ hi = strtonum(n, 1, PORT_MAX, &errstr); if (errstr) errx(1, "port number %s: %s", errstr, n); lo = strtonum(p, 1, PORT_MAX, &errstr); if (errstr) errx(1, "port number %s: %s", errstr, p); if (lo > hi) { cp = hi; hi = lo; lo = cp; } /* Load ports sequentially. */ for (cp = lo; cp <= hi; cp++) { portlist[x] = calloc(1, PORT_MAX_LEN); if (portlist[x] == NULL) err(1, NULL); snprintf(portlist[x], PORT_MAX_LEN, "%d", cp); x++; } /* Randomly swap ports. */ if (rflag) { int y; char *c; for (x = 0; x <= (hi - lo); x++) { y = (arc4random() & 0xFFFF) % (hi - lo); c = portlist[x]; portlist[x] = portlist[y]; portlist[y] = c; } } } else { hi = strtonum(p, 1, PORT_MAX, &errstr); if (errstr) errx(1, "port number %s: %s", errstr, p); portlist[0] = strdup(p); if (portlist[0] == NULL) err(1, NULL); } } /* * udptest() * Do a few writes to see if the UDP port is there. * Fails once PF state table is full. */ int udptest(int s) { int i, ret; for (i = 0; i <= 3; i++) { if (write(s, "X", 1) == 1) ret = 1; else ret = -1; } return (ret); } void set_common_sockopts(int s) { int x = 1; if (Sflag) { if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG, &x, sizeof(x)) == -1) err(1, NULL); } if (Dflag) { if (setsockopt(s, SOL_SOCKET, SO_DEBUG, &x, sizeof(x)) == -1) err(1, NULL); } if (Tflag != -1) { if (setsockopt(s, IPPROTO_IP, IP_TOS, &Tflag, sizeof(Tflag)) == -1) err(1, "set IP ToS"); } if (Iflag) { if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, &Iflag, sizeof(Iflag)) == -1) err(1, "set TCP receive buffer size"); } if (Oflag) { if (setsockopt(s, SOL_SOCKET, SO_SNDBUF, &Oflag, sizeof(Oflag)) == -1) err(1, "set TCP send buffer size"); } } int map_tos(char *s, int *val) { /* DiffServ Codepoints and other TOS mappings */ const struct toskeywords { const char *keyword; int val; } *t, toskeywords[] = { { "af11", IPTOS_DSCP_AF11 }, { "af12", IPTOS_DSCP_AF12 }, { "af13", IPTOS_DSCP_AF13 }, { "af21", IPTOS_DSCP_AF21 }, { "af22", IPTOS_DSCP_AF22 }, { "af23", IPTOS_DSCP_AF23 }, { "af31", IPTOS_DSCP_AF31 }, { "af32", IPTOS_DSCP_AF32 }, { "af33", IPTOS_DSCP_AF33 }, { "af41", IPTOS_DSCP_AF41 }, { "af42", IPTOS_DSCP_AF42 }, { "af43", IPTOS_DSCP_AF43 }, { "critical", IPTOS_PREC_CRITIC_ECP }, { "cs0", IPTOS_DSCP_CS0 }, { "cs1", IPTOS_DSCP_CS1 }, { "cs2", IPTOS_DSCP_CS2 }, { "cs3", IPTOS_DSCP_CS3 }, { "cs4", IPTOS_DSCP_CS4 }, { "cs5", IPTOS_DSCP_CS5 }, { "cs6", IPTOS_DSCP_CS6 }, { "cs7", IPTOS_DSCP_CS7 }, { "ef", IPTOS_DSCP_EF }, { "inetcontrol", IPTOS_PREC_INTERNETCONTROL }, { "lowdelay", IPTOS_LOWDELAY }, { "netcontrol", IPTOS_PREC_NETCONTROL }, { "reliability", IPTOS_RELIABILITY }, { "throughput", IPTOS_THROUGHPUT }, { NULL, -1 }, }; for (t = toskeywords; t->keyword != NULL; t++) { if (strcmp(s, t->keyword) == 0) { *val = t->val; return (1); } } return (0); } void report_connect(const struct sockaddr *sa, socklen_t salen) { char remote_host[NI_MAXHOST]; char remote_port[NI_MAXSERV]; int herr; int flags = NI_NUMERICSERV; if (nflag) flags |= NI_NUMERICHOST; if ((herr = getnameinfo(sa, salen, remote_host, sizeof(remote_host), remote_port, sizeof(remote_port), flags)) != 0) { if (herr == EAI_SYSTEM) err(1, "getnameinfo"); else errx(1, "getnameinfo: %s", gai_strerror(herr)); } fprintf(stderr, "Connection from %s %s " "received!\n", remote_host, remote_port); } void help(void) { usage(0); fprintf(stderr, "\tCommand Summary:\n\ \t-4 Use IPv4\n\ \t-6 Use IPv6\n\ \t-D Enable the debug socket option\n\ \t-d Detach from stdin\n\ \t-F Pass socket fd\n\ \t-h This help text\n\ \t-I length TCP receive buffer length\n\ \t-i secs\t Delay interval for lines sent, ports scanned\n\ \t-k Keep inbound sockets open for multiple connects\n\ \t-l Listen mode, for inbound connects\n\ \t-N Shutdown the network socket after EOF on stdin\n\ \t-n Suppress name/port resolutions\n\ \t-O length TCP send buffer length\n\ \t-P proxyuser\tUsername for proxy authentication\n\ \t-p port\t Specify local port for remote connects\n\ \t-r Randomize remote ports\n\ \t-S Enable the TCP MD5 signature option\n\ \t-s addr\t Local source address\n\ \t-T toskeyword\tSet IP Type of Service\n\ \t-t Answer TELNET negotiation\n\ \t-U Use UNIX domain socket\n\ \t-u UDP mode\n\ \t-V rtable Specify alternate routing table\n\ \t-v Verbose\n\ \t-w secs\t Timeout for connects and final net reads\n\ \t-X proto Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\ \t-x addr[:port]\tSpecify proxy address and port\n\ \t-z Zero-I/O mode [used for scanning]\n\ Port numbers can be individual or ranges: lo-hi [inclusive]\n"); exit(1); } void usage(int ret) { fprintf(stderr, "usage: nc [-46DdFhklNnrStUuvz] [-I length] [-i interval] [-O length]\n" "\t [-P proxy_username] [-p source_port] [-s source] [-T ToS]\n" "\t [-V rtable] [-w timeout] [-X proxy_protocol]\n" "\t [-x proxy_address[:port]] [destination] [port]\n"); if (ret) exit(1); }