/* $OpenBSD: netcat.c,v 1.84 2005/10/25 06:51:37 dtucker 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 "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 /* Command Line Options */ int dflag; /* detached, no stdin */ int iflag; /* Interval Flag */ int jflag; /* use jumbo frames if we can */ int kflag; /* More than one connect */ int lflag; /* Bind to local port */ int nflag; /* Don't do name look up */ 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 Sflag; /* TCP MD5 signature option */ int Tflag = -1; /* IP Type of Service */ int timeout = -1; int family = AF_UNSPEC; char *portlist[PORT_MAX+1]; void atelnet(int, unsigned char *, unsigned int); void build_ports(char *); void help(void); int local_listen(char *, char *, struct addrinfo); void readwrite(int); int remote_connect(const char *, const char *, struct addrinfo); int socks_connect(const char *, const char *, struct addrinfo, const char *, const char *, struct addrinfo, int); int udptest(int); int unix_connect(char *); int unix_listen(char *); void set_common_sockopts(int); int parse_iptos(char *); void usage(int); int main(int argc, char *argv[]) { int ch, s, ret, socksv; char *host, *uport, *endp; struct addrinfo hints; struct servent *sv; socklen_t len; struct sockaddr_storage cliaddr; char *proxy; const char *proxyhost = "", *proxyport = NULL; struct addrinfo proxyhints; ret = 1; s = 0; socksv = 5; host = NULL; uport = NULL; endp = NULL; sv = NULL; while ((ch = getopt(argc, argv, "46Ddhi:jklnp:rSs:tT:Uuvw: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 'h': help(); break; case 'i': iflag = (int)strtoul(optarg, &endp, 10); if (iflag < 0 || *endp != '\0') errx(1, "interval cannot be negative"); break; case 'j': jflag = 1; break; case 'k': kflag = 1; break; case 'l': lflag = 1; break; case 'n': nflag = 1; 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': vflag = 1; break; case 'w': timeout = (int)strtoul(optarg, &endp, 10); if (timeout < 0 || *endp != '\0') errx(1, "timeout cannot be negative"); if (timeout >= (INT_MAX / 1000)) errx(1, "timeout too large"); 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 'S': Sflag = 1; break; case 'T': Tflag = parse_iptos(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) { if (uflag) errx(1, "cannot use -u and -U"); 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"); /* 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) 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, we will use recvfrom() initially * to wait for a caller, then use the regular * functions to talk to the caller. */ if (uflag) { int rv, plen; char buf[8192]; struct sockaddr_storage z; len = sizeof(z); plen = jflag ? 8192 : 1024; 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"); connfd = s; } else { len = sizeof(cliaddr); connfd = accept(s, (struct sockaddr *)&cliaddr, &len); } readwrite(connfd); close(connfd); if (family != AF_UNIX) close(s); if (!kflag) break; } } else if (family == AF_UNIX) { ret = 0; if ((s = unix_connect(host)) > 0 && !zflag) { readwrite(s); close(s); } else ret = 1; 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); 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"); } printf("Connection to %s %s port [%s/%s] succeeded!\n", host, portlist[i], uflag ? "udp" : "tcp", sv ? sv->s_name : "*"); } if (!zflag) readwrite(s); } } if (s) close(s); exit(ret); } /* * 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 ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) return (-1); (void)fcntl(s, F_SETFD, 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 (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) { struct sockaddr_un sun; int s; /* Create unix domain socket. */ if ((s = socket(AF_UNIX, 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); } 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; 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; /* Bind to a local port or source address if specified. */ if (sflag || pflag) { struct addrinfo ahints, *ares; if (!(sflag && pflag)) { if (!sflag) sflag = NULL; else pflag = NULL; } 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) errx(1, "bind failed: %s", strerror(errno)); freeaddrinfo(ares); } set_common_sockopts(s); if (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); } /* * 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; 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 nfd) { struct pollfd pfd[2]; unsigned char buf[8192]; int n, wfd = fileno(stdin); int lfd = fileno(stdout); int plen; plen = jflag ? 8192 : 1024; /* Setup Network FD */ pfd[0].fd = nfd; pfd[0].events = POLLIN; /* Set up STDIN FD. */ pfd[1].fd = wfd; pfd[1].events = POLLIN; while (pfd[0].fd != -1) { if (iflag) sleep(iflag); if ((n = poll(pfd, 2 - dflag, timeout)) < 0) { close(nfd); err(1, "Polling Error"); } if (n == 0) return; if (pfd[0].revents & POLLIN) { if ((n = read(nfd, buf, plen)) < 0) return; else if (n == 0) { shutdown(nfd, SHUT_RD); pfd[0].fd = -1; pfd[0].events = 0; } else { if (tflag) atelnet(nfd, buf, n); if (atomicio(vwrite, lfd, buf, n) != n) return; } } if (!dflag && pfd[1].revents & POLLIN) { if ((n = read(wfd, buf, plen)) < 0) return; else if (n == 0) { shutdown(nfd, SHUT_WR); pfd[1].fd = -1; pfd[1].events = 0; } else { if (atomicio(vwrite, nfd, buf, n) != n) return; } } } } /* 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]; end = buf + size; obuf[0] = '\0'; for (p = buf; p < end; p++) { if (*p != IAC) break; obuf[0] = IAC; p++; if ((*p == WILL) || (*p == WONT)) obuf[1] = DONT; if ((*p == DO) || (*p == DONT)) obuf[1] = WONT; if (obuf) { p++; obuf[2] = *p; obuf[3] = '\0'; if (atomicio(vwrite, nfd, obuf, 3) != 3) warn("Write Error!"); obuf[0] = '\0'; } } } /* * build_ports() * Build an array or ports in portlist[], listing each port * that we should try to connect to. */ void build_ports(char *p) { char *n, *endp; int hi, lo, cp; int x = 0; if ((n = strchr(p, '-')) != NULL) { if (lflag) errx(1, "Cannot use -l with multiple ports!"); *n = '\0'; n++; /* Make sure the ports are in order: lowest->highest. */ hi = (int)strtoul(n, &endp, 10); if (hi <= 0 || hi > PORT_MAX || *endp != '\0') errx(1, "port range not valid"); lo = (int)strtoul(p, &endp, 10); if (lo <= 0 || lo > PORT_MAX || *endp != '\0') errx(1, "port range not valid"); 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 = (int)strtoul(p, &endp, 10); if (hi <= 0 || hi > PORT_MAX || *endp != '\0') errx(1, "port range not valid"); portlist[0] = calloc(1, PORT_MAX_LEN); if (portlist[0] == NULL) err(1, NULL); portlist[0] = p; } } /* * udptest() * Do a few writes to see if the UDP port is there. * XXX - Better way of doing this? Doesn't work for IPv6. * Also fails after around 100 ports checked. */ 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 (jflag) { if (setsockopt(s, SOL_SOCKET, SO_JUMBO, &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"); } } int parse_iptos(char *s) { int tos = -1; if (strcmp(s, "lowdelay") == 0) return (IPTOS_LOWDELAY); if (strcmp(s, "throughput") == 0) return (IPTOS_THROUGHPUT); if (strcmp(s, "reliability") == 0) return (IPTOS_RELIABILITY); if (sscanf(s, "0x%x", &tos) != 1 || tos < 0 || tos > 0xff) errx(1, "invalid IP Type of Service"); return (tos); } 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-h This help text\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 Suppress name/port resolutions\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 ToS\t Set 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 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 [-46DdhklnrStUuvz] [-i interval] [-p source_port]\n"); fprintf(stderr, "\t [-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_version]\n"); fprintf(stderr, "\t [-x proxy_address[:port]] [hostname] [port[s]]\n"); if (ret) exit(1); }