static void read_socket_handler(nsock_pool nsp, nsock_event evt, void *data)
{
enum nse_status status = nse_status(evt);
enum nse_type type = nse_type(evt);
char *buf;
int nbytes;
ncat_assert(type == NSE_TYPE_READ);
if (status == NSE_STATUS_EOF) {
Close(STDOUT_FILENO);
/* In --recv-only mode or non-TCP mode, exit after EOF on the socket. */
if (o.proto != IPPROTO_TCP || (o.proto == IPPROTO_TCP && o.recvonly))
nsock_loop_quit(nsp);
return;
} else if (status == NSE_STATUS_ERROR) {
loguser("%s.\n", socket_strerror(nse_errorcode(evt)));
exit(1);
} else if (status == NSE_STATUS_TIMEOUT) {
loguser("%s.\n", socket_strerror(ETIMEDOUT));
exit(1);
} else if (status == NSE_STATUS_CANCELLED || status == NSE_STATUS_KILL) {
return;
} else {
ncat_assert(status == NSE_STATUS_SUCCESS);
}
buf = nse_readbuf(evt, &nbytes);
if (o.linedelay)
ncat_delay_timer(o.linedelay);
if (o.telnet)
dotelnet(nsi_getsd(nse_iod(evt)), (unsigned char *) buf, nbytes);
/* Write socket data to stdout */
Write(STDOUT_FILENO, buf, nbytes);
ncat_log_recv(buf, nbytes);
nsock_readbytes(nsp, cs.sock_nsi, read_socket_handler, -1, NULL, 0);
refresh_idle_timer(nsp);
}
/* Read from a client socket into buf, returning the number of bytes read, or -1 on an error. This takes care of delays, Telnet negotiation, and logging. If there is more data pending that won't be noticed by select, a 1 is stored in *pending, otherwise 0 is stored there. The caller must loop, processing read data until *pending is false. The reason for this is the SSL_read function that this function may call, which takes data out of the socket buffer (so select may not indicate the socket is readable) and keeps it in its own buffer. *pending holds the result of calling SSL_pending. See http://www.mail-archive.com/[email protected]/msg24324.html. */ int ncat_recv(struct fdinfo *fdn, char *buf, size_t size, int *pending) { int n; *pending = 0; n = fdinfo_recv(fdn, buf, size); if (n <= 0) return n; if (o.linedelay) ncat_delay_timer(o.linedelay); if (o.telnet) dotelnet(fdn->fd, (unsigned char *) buf, n); ncat_log_recv(buf, n); /* SSL can buffer our input, so doing another select() won't necessarily work for us. Indicate to the caller that this function must be called again to get more data. */ *pending = fdinfo_pending(fdn); return n; }
/* This is sufficiently different from the TCP code (wrt SSL, etc) that it
* resides in its own simpler function
*/
static int ncat_listen_dgram(int proto)
{
struct {
int fd;
union sockaddr_u addr;
} sockfd[NUM_LISTEN_ADDRS];
int i, fdn = -1;
int fdmax, nbytes, n, fds_ready;
char buf[DEFAULT_UDP_BUF_LEN] = { 0 };
char *tempbuf = NULL;
fd_set read_fds;
union sockaddr_u remotess;
socklen_t sslen = sizeof(remotess.storage);
struct timeval tv;
struct timeval *tvp = NULL;
unsigned int num_sockets;
for (i = 0; i < NUM_LISTEN_ADDRS; i++) {
sockfd[i].fd = -1;
sockfd[i].addr.storage.ss_family = AF_UNSPEC;
}
FD_ZERO(&read_fds);
/* Initialize remotess struct so recvfrom() doesn't hit the fan.. */
zmem(&remotess.storage, sizeof(remotess.storage));
remotess.storage.ss_family = o.af;
#ifdef WIN32
set_pseudo_sigchld_handler(decrease_conn_count);
#else
/* Reap on SIGCHLD */
Signal(SIGCHLD, sigchld_handler);
/* Ignore the SIGPIPE that occurs when a client disconnects suddenly and we
send data to it before noticing. */
Signal(SIGPIPE, SIG_IGN);
#endif
/* Not sure if this problem exists on Windows, but fcntl and /dev/null don't */
#ifndef WIN32
/* Check whether stdin is closed. Because we treat this fd specially, we
* can't risk it being reopened for an incoming connection, so we'll hold
* it open instead. */
if (fcntl(STDIN_FILENO, F_GETFD) == -1 && errno == EBADF) {
logdebug("stdin is closed, attempting to reserve STDIN_FILENO\n");
i = open("/dev/null", O_RDONLY);
if (i >= 0 && i != STDIN_FILENO) {
/* Oh well, we tried */
logdebug("Couldn't reserve STDIN_FILENO\n");
close(i);
}
}
#endif
/* set for selecting udp listening sockets */
fd_set listen_fds;
fd_list_t listen_fdlist;
FD_ZERO(&listen_fds);
init_fdlist(&listen_fdlist, num_listenaddrs);
num_sockets = 0;
for (i = 0; i < num_listenaddrs; i++) {
/* create the UDP listen sockets */
sockfd[num_sockets].fd = do_listen(SOCK_DGRAM, proto, &listenaddrs[i]);
if (sockfd[num_sockets].fd == -1) {
if (o.debug > 0)
logdebug("do_listen(\"%s\"): %s\n", inet_ntop_ez(&listenaddrs[i].storage, sizeof(listenaddrs[i].storage)), socket_strerror(socket_errno()));
continue;
}
FD_SET(sockfd[num_sockets].fd, &listen_fds);
add_fd(&listen_fdlist, sockfd[num_sockets].fd);
sockfd[num_sockets].addr = listenaddrs[i];
num_sockets++;
}
if (num_sockets == 0) {
if (num_listenaddrs == 1)
bye("Unable to open listening socket on %s: %s", inet_ntop_ez(&listenaddrs[0].storage, sizeof(listenaddrs[0].storage)), socket_strerror(socket_errno()));
else
bye("Unable to open any listening sockets.");
}
if (o.idletimeout > 0)
tvp = &tv;
while (1) {
int i, j, conn_count, socket_n;
if (fdn != -1) {
/*remove socket descriptor which is burnt */
FD_CLR(sockfd[fdn].fd, &listen_fds);
rm_fd(&listen_fdlist, sockfd[fdn].fd);
/* Rebuild the udp socket which got burnt */
sockfd[fdn].fd = do_listen(SOCK_DGRAM, proto, &sockfd[fdn].addr);
if (sockfd[fdn].fd == -1)
bye("do_listen: %s", socket_strerror(socket_errno()));
FD_SET(sockfd[fdn].fd, &listen_fds);
add_fd(&listen_fdlist, sockfd[fdn].fd);
}
fdn = -1;
socket_n = -1;
fd_set fds;
FD_ZERO(&fds);
while (1) {
/*
* We just select to get a list of sockets which we can talk to
*/
if (o.debug > 1)
logdebug("selecting, fdmax %d\n", listen_fdlist.fdmax);
fds = listen_fds;
if (o.idletimeout > 0)
ms_to_timeval(tvp, o.idletimeout);
fds_ready = fselect(listen_fdlist.fdmax + 1, &fds, NULL, NULL, tvp);
if (o.debug > 1)
logdebug("select returned %d fds ready\n", fds_ready);
if (fds_ready == 0)
bye("Idle timeout expired (%d ms).", o.idletimeout);
/*
* Figure out which listening socket got a connection. This loop should
* really call a function for each ready socket instead of breaking on
* the first one.
*/
for (i = 0; i <= listen_fdlist.fdmax && fds_ready > 0; i++) {
/* Loop through descriptors until there is something ready */
if (!FD_ISSET(i, &fds))
continue;
/* Check each listening socket */
for (j = 0; j < num_sockets; j++) {
if (i == sockfd[j].fd) {
if (o.debug > 1)
logdebug("Valid descriptor %d \n", i);
fdn = j;
socket_n = i;
break;
}
}
/* if we found a valid socket break */
if (fdn != -1) {
fds_ready--;
break;
}
}
/* Make sure someone connected */
if (fdn == -1)
continue;
/*
* We just peek so we can get the client connection details without
* removing anything from the queue. Sigh.
*/
nbytes = recvfrom(socket_n, buf, sizeof(buf), MSG_PEEK,
&remotess.sockaddr, &sslen);
if (nbytes < 0) {
loguser("%s.\n", socket_strerror(socket_errno()));
close(socket_n);
return 1;
}
/* Check conditions that might cause us to deny the connection. */
conn_count = get_conn_count();
if (conn_count >= o.conn_limit) {
if (o.verbose)
loguser("New connection denied: connection limit reached (%d)\n", conn_count);
} else if (!allow_access(&remotess)) {
if (o.verbose)
loguser("New connection denied: not allowed\n");
} else {
/* Good to go. */
break;
}
/* Dump the current datagram */
nbytes = recv(socket_n, buf, sizeof(buf), 0);
if (nbytes < 0) {
loguser("%s.\n", socket_strerror(socket_errno()));
close(socket_n);
return 1;
}
ncat_log_recv(buf, nbytes);
}
if (o.debug > 1)
logdebug("Valid Connection from %d\n", socket_n);
conn_inc++;
/*
* We're using connected udp. This has the down side of only
* being able to handle one udp client at a time
*/
Connect(socket_n, &remotess.sockaddr, sslen);
/* clean slate for buf */
zmem(buf, sizeof(buf));
/* are we executing a command? then do it */
if (o.cmdexec) {
struct fdinfo info = { 0 };
info.fd = socket_n;
if (o.keepopen)
netrun(&info, o.cmdexec);
else
netexec(&info, o.cmdexec);
continue;
}
FD_SET(socket_n, &read_fds);
FD_SET(STDIN_FILENO, &read_fds);
fdmax = socket_n;
/* stdin -> socket and socket -> stdout */
while (1) {
fd_set fds;
fds = read_fds;
if (o.debug > 1)
logdebug("udp select'ing\n");
if (o.idletimeout > 0)
ms_to_timeval(tvp, o.idletimeout);
fds_ready = fselect(fdmax + 1, &fds, NULL, NULL, tvp);
if (fds_ready == 0)
bye("Idle timeout expired (%d ms).", o.idletimeout);
if (FD_ISSET(STDIN_FILENO, &fds)) {
nbytes = Read(STDIN_FILENO, buf, sizeof(buf));
if (nbytes <= 0) {
if (nbytes < 0 && o.verbose) {
logdebug("Error reading from stdin: %s\n", strerror(errno));
} else if (nbytes == 0 && o.debug) {
logdebug("EOF on stdin\n");
}
FD_CLR(STDIN_FILENO, &read_fds);
if (nbytes < 0)
return 1;
continue;
}
if (o.crlf)
fix_line_endings((char *) buf, &nbytes, &tempbuf, &crlf_state);
if (!o.recvonly) {
if (tempbuf != NULL)
n = send(socket_n, tempbuf, nbytes, 0);
else
n = send(socket_n, buf, nbytes, 0);
if (n < nbytes) {
loguser("%s.\n", socket_strerror(socket_errno()));
close(socket_n);
return 1;
}
ncat_log_send(buf, nbytes);
}
if (tempbuf != NULL) {
free(tempbuf);
tempbuf = NULL;
}
}
if (FD_ISSET(socket_n, &fds)) {
nbytes = recv(socket_n, buf, sizeof(buf), 0);
if (nbytes < 0) {
loguser("%s.\n", socket_strerror(socket_errno()));
close(socket_n);
return 1;
}
ncat_log_recv(buf, nbytes);
if (!o.sendonly)
Write(STDOUT_FILENO, buf, nbytes);
}
zmem(buf, sizeof(buf));
}
}
return 0;
}
