/*************************************************************************** * ncat_broker.c -- --broker and --chat modes. * ***********************IMPORTANT NMAP LICENSE TERMS************************ * * * The Nmap Security Scanner is (C) 1996-2011 Insecure.Com LLC. Nmap is * * also a registered trademark of Insecure.Com LLC. This program is free * * software; you may redistribute and/or modify it under the terms of the * * GNU General Public License as published by the Free Software * * Foundation; Version 2 with the clarifications and exceptions described * * below. This guarantees your right to use, modify, and redistribute * * this software under certain conditions. If you wish to embed Nmap * * technology into proprietary software, we sell alternative licenses * * (contact sales@insecure.com). Dozens of software vendors already * * license Nmap technology such as host discovery, port scanning, OS * * detection, and version detection. * * * * Note that the GPL places important restrictions on "derived works", yet * * it does not provide a detailed definition of that term. To avoid * * misunderstandings, we consider an application to constitute a * * "derivative work" for the purpose of this license if it does any of the * * following: * * o Integrates source code from Nmap * * o Reads or includes Nmap copyrighted data files, such as * * nmap-os-db or nmap-service-probes. * * o Executes Nmap and parses the results (as opposed to typical shell or * * execution-menu apps, which simply display raw Nmap output and so are * * not derivative works.) * * o Integrates/includes/aggregates Nmap into a proprietary executable * * installer, such as those produced by InstallShield. * * o Links to a library or executes a program that does any of the above * * * * The term "Nmap" should be taken to also include any portions or derived * * works of Nmap. This list is not exclusive, but is meant to clarify our * * interpretation of derived works with some common examples. Our * * interpretation applies only to Nmap--we don't speak for other people's * * GPL works. * * * * If you have any questions about the GPL licensing restrictions on using * * Nmap in non-GPL works, we would be happy to help. As mentioned above, * * we also offer alternative license to integrate Nmap into proprietary * * applications and appliances. These contracts have been sold to dozens * * of software vendors, and generally include a perpetual license as well * * as providing for priority support and updates as well as helping to * * fund the continued development of Nmap technology. Please email * * sales@insecure.com for further information. * * * * As a special exception to the GPL terms, Insecure.Com LLC grants * * permission to link the code of this program with any version of the * * OpenSSL library which is distributed under a license identical to that * * listed in the included docs/licenses/OpenSSL.txt file, and distribute * * linked combinations including the two. You must obey the GNU GPL in all * * respects for all of the code used other than OpenSSL. If you modify * * this file, you may extend this exception to your version of the file, * * but you are not obligated to do so. * * * * If you received these files with a written license agreement or * * contract stating terms other than the terms above, then that * * alternative license agreement takes precedence over these comments. * * * * Source is provided to this software because we believe users have a * * right to know exactly what a program is going to do before they run it. * * This also allows you to audit the software for security holes (none * * have been found so far). * * * * Source code also allows you to port Nmap to new platforms, fix bugs, * * and add new features. You are highly encouraged to send your changes * * to nmap-dev@insecure.org for possible incorporation into the main * * distribution. By sending these changes to Fyodor or one of the * * Insecure.Org development mailing lists, it is assumed that you are * * offering the Nmap Project (Insecure.Com LLC) the unlimited, * * non-exclusive right to reuse, modify, and relicense the code. Nmap * * will always be available Open Source, but this is important because the * * inability to relicense code has caused devastating problems for other * * Free Software projects (such as KDE and NASM). We also occasionally * * relicense the code to third parties as discussed above. If you wish to * * specify special license conditions of your contributions, just say so * * when you send them. * * * * This program is distributed in the hope that it will be useful, but * * WITHOUT ANY WARRANTY; without even the implied warranty of * * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * * General Public License v2.0 for more details at * * http://www.gnu.org/licenses/gpl-2.0.html , or in the COPYING file * * included with Nmap. * * * ***************************************************************************/ /* $Id$ */ #include "ncat.h" #include #include #include #include #include #include #include #ifndef WIN32 #include #include #include #include #include #else #include #endif #ifdef HAVE_OPENSSL #include #include #endif /* read_fds is the clients we are accepting data from. broadcast_fds is the clients were are sending data to. broadcast_fds doesn't include the listening socket and stdin. Network clients are not added to read_fds when --send-only is used, because they would be always selected without having data read. */ static fd_set read_fds, broadcast_fds; /* These are bookkeeping data structures that are parallel to read_fds and broadcast_fds. */ static fd_list_t read_fdlist, broadcast_fdlist; static int listen_socket; static int conn_count = 0; /* Has stdin seen EOF? */ static int stdin_eof = 0; static int crlf_state = 0; static void handle_connection(void); static void read_and_broadcast(int recv_socket); static int chat_announce_connect(int fd, const union sockaddr_u *su); static int chat_announce_disconnect(int fd); static char *chat_filter(char *buf, size_t size, int fd, int *nwritten); int ncat_broker(void) { #ifdef HAVE_OPENSSL SSL_CTX *ctx; #endif /* clear out structs */ FD_ZERO(&read_fds); FD_ZERO(&broadcast_fds); zmem(&read_fdlist, sizeof(read_fdlist)); zmem(&broadcast_fdlist, sizeof(broadcast_fdlist)); #ifndef WIN32 /* Ignore the SIGPIPE that occurs when a client disconnects suddenly and we send data to it before noticing. */ Signal(SIGPIPE, SIG_IGN); #endif #ifdef HAVE_OPENSSL if (o.ssl) ctx = setup_ssl_listen(); #endif /* setup the main listening socket */ listen_socket = do_listen(SOCK_STREAM, IPPROTO_TCP); /* Make our listening socket non-blocking because there are timing issues * which could cause us to block on accept() even though select() says it's * readable. See UNPv1 2nd ed, p422 for more. */ unblock_socket(listen_socket); /* setup select sets and max fd */ FD_SET(listen_socket, &read_fds); /* we need a list of fds to keep current fdmax */ init_fdlist(&read_fdlist, sadd(o.conn_limit, 2)); add_fd(&read_fdlist, listen_socket); add_fd(&read_fdlist, STDIN_FILENO); init_fdlist(&broadcast_fdlist, o.conn_limit); while (1) { fd_set fds; int i, fds_ready; if (o.debug > 1) logdebug("Broker connection count is %d\n", conn_count); fds = read_fds; fds_ready = fselect(read_fdlist.fdmax + 1, &fds, NULL, NULL, NULL); if(o.debug > 1) logdebug("select returned %d fds ready\n", fds_ready); /* * FIXME: optimize this loop to look only at the fds in the fd list, * doing it this way means that if you have one descriptor that is very * large, say 500, and none close to it, that you'll loop many times for * nothing. */ for (i = 0; i <= read_fdlist.fdmax && fds_ready > 0; i++) { /* Loop through descriptors until there's something to read */ if (!FD_ISSET(i, &fds)) continue; if (o.debug > 1) logdebug("fd %d is ready\n", i); if (i == listen_socket) { /* we have a new connection request */ handle_connection(); } else if (i == STDIN_FILENO || !o.sendonly) { /* Handle incoming client data and distribute it. */ read_and_broadcast(i); } fds_ready--; } } return 0; } /* Accept a connection on a listening socket. Allow or deny the connection. If allowed, add the new socket to the watch set. */ static void handle_connection(void) { union sockaddr_u remoteaddr; socklen_t ss_len; struct fdinfo s = { 0 }; ss_len = sizeof(remoteaddr.storage); errno = 0; s.fd = accept(listen_socket, &remoteaddr.sockaddr, &ss_len); if (s.fd < 0) { if (o.debug) logdebug("Error in accept: %s\n", strerror(errno)); close(s.fd); return; } if (o.verbose) { if (o.chat) loguser("Connection from %s on file descriptor %d.\n", inet_socktop(&remoteaddr), s.fd); else loguser("Connection from %s.\n", inet_socktop(&remoteaddr)); } /* Check conditions that might cause us to deny the connection. */ if (conn_count >= o.conn_limit) { if (o.verbose) loguser("New connection denied: connection limit reached (%d)\n", conn_count); Close(s.fd); return; } if (!allow_access(&remoteaddr)) { if (o.verbose) loguser("New connection denied: not allowed\n"); Close(s.fd); return; } /* On Linux the new socket will be blocking, but on BSD it inherits the non-blocking status of the listening socket. The socket must be blocking for operations like SSL_accept to work in the way that we use them. */ block_socket(s.fd); #ifdef HAVE_OPENSSL if (o.ssl) { s.ssl = new_ssl(s.fd); if (SSL_accept(s.ssl) != 1) { if (o.verbose) { loguser("Failed SSL connection from %s: %s\n", inet_socktop(&remoteaddr), ERR_error_string(ERR_get_error(), NULL)); } SSL_free(s.ssl); Close(s.fd); return; } } #endif conn_count++; /* Now that a client is connected, pay attention to stdin. */ if (!stdin_eof) FD_SET(STDIN_FILENO, &read_fds); if (!o.sendonly) { /* add to our lists */ FD_SET(s.fd, &read_fds); /* add it to our list of fds for maintaining maxfd */ if (add_fdinfo(&read_fdlist, &s) < 0) bye("add_fdinfo() failed."); } FD_SET(s.fd, &broadcast_fds); if (add_fdinfo(&broadcast_fdlist, &s) < 0) bye("add_fdinfo() failed."); if (o.chat) chat_announce_connect(s.fd, &remoteaddr); } /* Read from recv_fd and broadcast whatever is read to all other descriptors in read_fds, with the exception of stdin, listen_socket, and recv_fd itself. Handles EOL translation and chat mode. On read error or end of stream, closes the socket and removes it from the read_fds list. */ static void read_and_broadcast(int recv_fd) { struct fdinfo *fdn; int pending; fdn = get_fdinfo(&read_fdlist, recv_fd); assert(fdn); /* Loop while ncat_recv indicates data is pending. */ do { char buf[DEFAULT_TCP_BUF_LEN]; char *chatbuf, *outbuf; char *tempbuf = NULL; fd_set fds; int n; /* Behavior differs depending on whether this is stdin or a socket. */ if (recv_fd == STDIN_FILENO) { n = read(recv_fd, buf, sizeof(buf)); if (n <= 0) { if (n < 0 && o.verbose) logdebug("Error reading from stdin: %s\n", strerror(errno)); if (n == 0 && o.debug) logdebug("EOF on stdin\n"); /* Don't close the file because that allows a socket to be fd 0. */ FD_CLR(recv_fd, &read_fds); /* But mark that we've seen EOF so it doesn't get re-added to the select list. */ stdin_eof = 1; return; } if (o.crlf) fix_line_endings((char *) buf, &n, &tempbuf, &crlf_state); pending = 0; } else { /* From a connected socket, not stdin. */ n = ncat_recv(fdn, buf, sizeof(buf), &pending); if (n <= 0) { if (o.debug) logdebug("Closing connection.\n"); #ifdef HAVE_OPENSSL if (o.ssl && fdn->ssl) { if (n == 0) SSL_shutdown(fdn->ssl); SSL_free(fdn->ssl); } #endif close(recv_fd); FD_CLR(recv_fd, &read_fds); rm_fd(&read_fdlist, recv_fd); FD_CLR(recv_fd, &broadcast_fds); rm_fd(&broadcast_fdlist, recv_fd); conn_count--; if (conn_count == 0) FD_CLR(STDIN_FILENO, &read_fds); if (o.chat) chat_announce_disconnect(recv_fd); return; } } if (o.debug > 1) logdebug("Handling data from client %d.\n", recv_fd); chatbuf = NULL; /* tempbuf is in use if we read from STDIN and fixed EOL */ if (tempbuf == NULL) outbuf = buf; else outbuf = tempbuf; if (o.chat) { chatbuf = chat_filter(outbuf, n, recv_fd, &n); if (chatbuf == NULL) { if (o.verbose) logdebug("Error formatting chat message from fd %d\n", recv_fd); } else { outbuf = chatbuf; } } /* Send to everyone except the one who sent this message. */ fds = broadcast_fds; FD_CLR(recv_fd, &fds); ncat_broadcast(&fds, &broadcast_fdlist, outbuf, n); free(chatbuf); free(tempbuf); tempbuf = NULL; } while (pending); } /* Announce the new connection and who is already connected. */ static int chat_announce_connect(int fd, const union sockaddr_u *su) { char *buf = NULL; size_t size = 0, offset = 0; int i, count, ret; strbuf_sprintf(&buf, &size, &offset, " %s is connected as .\n", inet_socktop(su), fd); strbuf_sprintf(&buf, &size, &offset, " already connected: "); count = 0; for (i = 0; i < read_fdlist.fdmax; i++) { union sockaddr_u su; socklen_t len = sizeof(su.storage); if (i == fd || !FD_ISSET(i, &broadcast_fds)) continue; if (getpeername(i, &su.sockaddr, &len) == -1) bye("getpeername for sd %d failed: %s.", strerror(errno)); if (count > 0) strbuf_sprintf(&buf, &size, &offset, ", "); strbuf_sprintf(&buf, &size, &offset, "%s as ", inet_socktop(&su), i); count++; } if (count == 0) strbuf_sprintf(&buf, &size, &offset, "nobody"); strbuf_sprintf(&buf, &size, &offset, ".\n"); ret = ncat_broadcast(&broadcast_fds, &broadcast_fdlist, buf, offset); free(buf); return ret; } static int chat_announce_disconnect(int fd) { char buf[128]; int n; n = Snprintf(buf, sizeof(buf), " is disconnected.\n", fd); if (n >= sizeof(buf) || n < 0) return -1; return ncat_broadcast(&broadcast_fds, &broadcast_fdlist, buf, n); } /* * This is stupid. But it's just a bit of fun. * * The file descriptor of the sender is prepended to the * message sent to clients, so you can distinguish * each other with a degree of sanity. This gives a * similar effect to an IRC session. But stupider. */ static char *chat_filter(char *buf, size_t size, int fd, int *nwritten) { char *result = NULL; size_t n = 0; const char *p; int i; n = 32; result = (char *) safe_malloc(n); i = Snprintf(result, n, " ", fd); /* Escape control characters. */ for (p = buf; p - buf < size; p++) { char repl[32]; int repl_len; if (isprint((int) (unsigned char) *p) || *p == '\r' || *p == '\n' || *p == '\t') { repl[0] = *p; repl_len = 1; } else { repl_len = Snprintf(repl, sizeof(repl), "\\%03o", (unsigned char) *p); } if (i + repl_len > n) { n = (i + repl_len) * 2; result = (char *) safe_realloc(result, n + 1); } memcpy(result + i, repl, repl_len); i += repl_len; } /* Trim to length. (Also does initial allocation when str is empty.) */ result = (char *) safe_realloc(result, i + 1); result[i] = '\0'; *nwritten = i; return result; }