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refactor activation of rekeying

This makes automatic rekeying internal to the packet code (previously
the server and client loops needed to assist). In doing to it makes
application of rekey limits more accurate by accounting for packets
about to be sent as well as packets queued during rekeying events
themselves.

Based on a patch from dtucker@ which was in turn based on a patch
Aleksander Adamowski in bz#2521; ok markus@

/* $OpenBSD: serverloop.c,v 1.182 2016/02/08 10:57:07 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Server main loop for handling the interactive session.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 * SSH2 support by Markus Friedl.
 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
 *
 * 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.
 *
 * 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.
 */

#include <sys/param.h>	/* MIN MAX */
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/queue.h>

#include <netinet/in.h>

#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <signal.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <stdarg.h>

#include "xmalloc.h"
#include "packet.h"
#include "buffer.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
#include "canohost.h"
#include "sshpty.h"
#include "channels.h"
#include "compat.h"
#include "ssh1.h"
#include "ssh2.h"
#include "key.h"
#include "cipher.h"
#include "kex.h"
#include "hostfile.h"
#include "auth.h"
#include "session.h"
#include "dispatch.h"
#include "auth-options.h"
#include "serverloop.h"
#include "ssherr.h"

extern ServerOptions options;

/* XXX */
extern Authctxt *the_authctxt;
extern int use_privsep;

static Buffer stdin_buffer;	/* Buffer for stdin data. */
static Buffer stdout_buffer;	/* Buffer for stdout data. */
static Buffer stderr_buffer;	/* Buffer for stderr data. */
static int fdin;		/* Descriptor for stdin (for writing) */
static int fdout;		/* Descriptor for stdout (for reading);
				   May be same number as fdin. */
static int fderr;		/* Descriptor for stderr.  May be -1. */
static long stdin_bytes = 0;	/* Number of bytes written to stdin. */
static long stdout_bytes = 0;	/* Number of stdout bytes sent to client. */
static long stderr_bytes = 0;	/* Number of stderr bytes sent to client. */
static long fdout_bytes = 0;	/* Number of stdout bytes read from program. */
static int stdin_eof = 0;	/* EOF message received from client. */
static int fdout_eof = 0;	/* EOF encountered reading from fdout. */
static int fderr_eof = 0;	/* EOF encountered readung from fderr. */
static int fdin_is_tty = 0;	/* fdin points to a tty. */
static int connection_in;	/* Connection to client (input). */
static int connection_out;	/* Connection to client (output). */
static int connection_closed = 0;	/* Connection to client closed. */
static u_int buffer_high;	/* "Soft" max buffer size. */
static int no_more_sessions = 0; /* Disallow further sessions. */

/*
 * This SIGCHLD kludge is used to detect when the child exits.  The server
 * will exit after that, as soon as forwarded connections have terminated.
 */

static volatile sig_atomic_t child_terminated = 0;	/* The child has terminated. */

/* Cleanup on signals (!use_privsep case only) */
static volatile sig_atomic_t received_sigterm = 0;

/* prototypes */
static void server_init_dispatch(void);

/*
 * we write to this pipe if a SIGCHLD is caught in order to avoid
 * the race between select() and child_terminated
 */
static int notify_pipe[2];
static void
notify_setup(void)
{
	if (pipe(notify_pipe) < 0) {
		error("pipe(notify_pipe) failed %s", strerror(errno));
	} else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) ||
	    (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) {
		error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
		close(notify_pipe[0]);
		close(notify_pipe[1]);
	} else {
		set_nonblock(notify_pipe[0]);
		set_nonblock(notify_pipe[1]);
		return;
	}
	notify_pipe[0] = -1;	/* read end */
	notify_pipe[1] = -1;	/* write end */
}
static void
notify_parent(void)
{
	if (notify_pipe[1] != -1)
		(void)write(notify_pipe[1], "", 1);
}
static void
notify_prepare(fd_set *readset)
{
	if (notify_pipe[0] != -1)
		FD_SET(notify_pipe[0], readset);
}
static void
notify_done(fd_set *readset)
{
	char c;

	if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
		while (read(notify_pipe[0], &c, 1) != -1)
			debug2("notify_done: reading");
}

/*ARGSUSED*/
static void
sigchld_handler(int sig)
{
	int save_errno = errno;
	child_terminated = 1;
	signal(SIGCHLD, sigchld_handler);
	notify_parent();
	errno = save_errno;
}

/*ARGSUSED*/
static void
sigterm_handler(int sig)
{
	received_sigterm = sig;
}

/*
 * Make packets from buffered stderr data, and buffer it for sending
 * to the client.
 */
static void
make_packets_from_stderr_data(void)
{
	u_int len;

	/* Send buffered stderr data to the client. */
	while (buffer_len(&stderr_buffer) > 0 &&
	    packet_not_very_much_data_to_write()) {
		len = buffer_len(&stderr_buffer);
		if (packet_is_interactive()) {
			if (len > 512)
				len = 512;
		} else {
			/* Keep the packets at reasonable size. */
			if (len > packet_get_maxsize())
				len = packet_get_maxsize();
		}
		packet_start(SSH_SMSG_STDERR_DATA);
		packet_put_string(buffer_ptr(&stderr_buffer), len);
		packet_send();
		buffer_consume(&stderr_buffer, len);
		stderr_bytes += len;
	}
}

/*
 * Make packets from buffered stdout data, and buffer it for sending to the
 * client.
 */
static void
make_packets_from_stdout_data(void)
{
	u_int len;

	/* Send buffered stdout data to the client. */
	while (buffer_len(&stdout_buffer) > 0 &&
	    packet_not_very_much_data_to_write()) {
		len = buffer_len(&stdout_buffer);
		if (packet_is_interactive()) {
			if (len > 512)
				len = 512;
		} else {
			/* Keep the packets at reasonable size. */
			if (len > packet_get_maxsize())
				len = packet_get_maxsize();
		}
		packet_start(SSH_SMSG_STDOUT_DATA);
		packet_put_string(buffer_ptr(&stdout_buffer), len);
		packet_send();
		buffer_consume(&stdout_buffer, len);
		stdout_bytes += len;
	}
}

static void
client_alive_check(void)
{
	int channel_id;

	/* timeout, check to see how many we have had */
	if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
		logit("Timeout, client not responding.");
		cleanup_exit(255);
	}

	/*
	 * send a bogus global/channel request with "wantreply",
	 * we should get back a failure
	 */
	if ((channel_id = channel_find_open()) == -1) {
		packet_start(SSH2_MSG_GLOBAL_REQUEST);
		packet_put_cstring("keepalive@openssh.com");
		packet_put_char(1);	/* boolean: want reply */
	} else {
		channel_request_start(channel_id, "keepalive@openssh.com", 1);
	}
	packet_send();
}

/*
 * Sleep in select() until we can do something.  This will initialize the
 * select masks.  Upon return, the masks will indicate which descriptors
 * have data or can accept data.  Optionally, a maximum time can be specified
 * for the duration of the wait (0 = infinite).
 */
static void
wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
    u_int *nallocp, u_int64_t max_time_milliseconds)
{
	struct timeval tv, *tvp;
	int ret;
	time_t minwait_secs = 0;
	int client_alive_scheduled = 0;

	/* Allocate and update select() masks for channel descriptors. */
	channel_prepare_select(readsetp, writesetp, maxfdp, nallocp,
	    &minwait_secs, 0);

	if (minwait_secs != 0)
		max_time_milliseconds = MIN(max_time_milliseconds,
		    (u_int)minwait_secs * 1000);

	/*
	 * if using client_alive, set the max timeout accordingly,
	 * and indicate that this particular timeout was for client
	 * alive by setting the client_alive_scheduled flag.
	 *
	 * this could be randomized somewhat to make traffic
	 * analysis more difficult, but we're not doing it yet.
	 */
	if (compat20 &&
	    max_time_milliseconds == 0 && options.client_alive_interval) {
		client_alive_scheduled = 1;
		max_time_milliseconds =
		    (u_int64_t)options.client_alive_interval * 1000;
	}

	if (compat20) {
#if 0
		/* wrong: bad condition XXX */
		if (channel_not_very_much_buffered_data())
#endif
		FD_SET(connection_in, *readsetp);
	} else {
		/*
		 * Read packets from the client unless we have too much
		 * buffered stdin or channel data.
		 */
		if (buffer_len(&stdin_buffer) < buffer_high &&
		    channel_not_very_much_buffered_data())
			FD_SET(connection_in, *readsetp);
		/*
		 * If there is not too much data already buffered going to
		 * the client, try to get some more data from the program.
		 */
		if (packet_not_very_much_data_to_write()) {
			if (!fdout_eof)
				FD_SET(fdout, *readsetp);
			if (!fderr_eof)
				FD_SET(fderr, *readsetp);
		}
		/*
		 * If we have buffered data, try to write some of that data
		 * to the program.
		 */
		if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
			FD_SET(fdin, *writesetp);
	}
	notify_prepare(*readsetp);

	/*
	 * If we have buffered packet data going to the client, mark that
	 * descriptor.
	 */
	if (packet_have_data_to_write())
		FD_SET(connection_out, *writesetp);

	/*
	 * If child has terminated and there is enough buffer space to read
	 * from it, then read as much as is available and exit.
	 */
	if (child_terminated && packet_not_very_much_data_to_write())
		if (max_time_milliseconds == 0 || client_alive_scheduled)
			max_time_milliseconds = 100;

	if (max_time_milliseconds == 0)
		tvp = NULL;
	else {
		tv.tv_sec = max_time_milliseconds / 1000;
		tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
		tvp = &tv;
	}

	/* Wait for something to happen, or the timeout to expire. */
	ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);

	if (ret == -1) {
		memset(*readsetp, 0, *nallocp);
		memset(*writesetp, 0, *nallocp);
		if (errno != EINTR)
			error("select: %.100s", strerror(errno));
	} else if (ret == 0 && client_alive_scheduled)
		client_alive_check();

	notify_done(*readsetp);
}

/*
 * Processes input from the client and the program.  Input data is stored
 * in buffers and processed later.
 */
static void
process_input(fd_set *readset)
{
	int len;
	char buf[16384];

	/* Read and buffer any input data from the client. */
	if (FD_ISSET(connection_in, readset)) {
		len = read(connection_in, buf, sizeof(buf));
		if (len == 0) {
			verbose("Connection closed by %.100s",
			    get_remote_ipaddr());
			connection_closed = 1;
			if (compat20)
				return;
			cleanup_exit(255);
		} else if (len < 0) {
			if (errno != EINTR && errno != EAGAIN) {
				verbose("Read error from remote host "
				    "%.100s: %.100s",
				    get_remote_ipaddr(), strerror(errno));
				cleanup_exit(255);
			}
		} else {
			/* Buffer any received data. */
			packet_process_incoming(buf, len);
		}
	}
	if (compat20)
		return;

	/* Read and buffer any available stdout data from the program. */
	if (!fdout_eof && FD_ISSET(fdout, readset)) {
		len = read(fdout, buf, sizeof(buf));
		if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
			/* do nothing */
		} else if (len <= 0) {
			fdout_eof = 1;
		} else {
			buffer_append(&stdout_buffer, buf, len);
			fdout_bytes += len;
		}
	}
	/* Read and buffer any available stderr data from the program. */
	if (!fderr_eof && FD_ISSET(fderr, readset)) {
		len = read(fderr, buf, sizeof(buf));
		if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
			/* do nothing */
		} else if (len <= 0) {
			fderr_eof = 1;
		} else {
			buffer_append(&stderr_buffer, buf, len);
		}
	}
}

/*
 * Sends data from internal buffers to client program stdin.
 */
static void
process_output(fd_set *writeset)
{
	struct termios tio;
	u_char *data;
	u_int dlen;
	int len;

	/* Write buffered data to program stdin. */
	if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
		data = buffer_ptr(&stdin_buffer);
		dlen = buffer_len(&stdin_buffer);
		len = write(fdin, data, dlen);
		if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
			/* do nothing */
		} else if (len <= 0) {
			if (fdin != fdout)
				close(fdin);
			else
				shutdown(fdin, SHUT_WR); /* We will no longer send. */
			fdin = -1;
		} else {
			/* Successful write. */
			if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
			    tcgetattr(fdin, &tio) == 0 &&
			    !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
				/*
				 * Simulate echo to reduce the impact of
				 * traffic analysis
				 */
				packet_send_ignore(len);
				packet_send();
			}
			/* Consume the data from the buffer. */
			buffer_consume(&stdin_buffer, len);
			/* Update the count of bytes written to the program. */
			stdin_bytes += len;
		}
	}
	/* Send any buffered packet data to the client. */
	if (FD_ISSET(connection_out, writeset))
		packet_write_poll();
}

/*
 * Wait until all buffered output has been sent to the client.
 * This is used when the program terminates.
 */
static void
drain_output(void)
{
	/* Send any buffered stdout data to the client. */
	if (buffer_len(&stdout_buffer) > 0) {
		packet_start(SSH_SMSG_STDOUT_DATA);
		packet_put_string(buffer_ptr(&stdout_buffer),
				  buffer_len(&stdout_buffer));
		packet_send();
		/* Update the count of sent bytes. */
		stdout_bytes += buffer_len(&stdout_buffer);
	}
	/* Send any buffered stderr data to the client. */
	if (buffer_len(&stderr_buffer) > 0) {
		packet_start(SSH_SMSG_STDERR_DATA);
		packet_put_string(buffer_ptr(&stderr_buffer),
				  buffer_len(&stderr_buffer));
		packet_send();
		/* Update the count of sent bytes. */
		stderr_bytes += buffer_len(&stderr_buffer);
	}
	/* Wait until all buffered data has been written to the client. */
	packet_write_wait();
}

static void
process_buffered_input_packets(void)
{
	dispatch_run(DISPATCH_NONBLOCK, NULL, active_state);
}

/*
 * Performs the interactive session.  This handles data transmission between
 * the client and the program.  Note that the notion of stdin, stdout, and
 * stderr in this function is sort of reversed: this function writes to
 * stdin (of the child program), and reads from stdout and stderr (of the
 * child program).
 */
void
server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
{
	fd_set *readset = NULL, *writeset = NULL;
	int max_fd = 0;
	u_int nalloc = 0;
	int wait_status;	/* Status returned by wait(). */
	pid_t wait_pid;		/* pid returned by wait(). */
	int waiting_termination = 0;	/* Have displayed waiting close message. */
	u_int64_t max_time_milliseconds;
	u_int previous_stdout_buffer_bytes;
	u_int stdout_buffer_bytes;
	int type;

	debug("Entering interactive session.");

	/* Initialize the SIGCHLD kludge. */
	child_terminated = 0;
	signal(SIGCHLD, sigchld_handler);

	if (!use_privsep) {
		signal(SIGTERM, sigterm_handler);
		signal(SIGINT, sigterm_handler);
		signal(SIGQUIT, sigterm_handler);
	}

	/* Initialize our global variables. */
	fdin = fdin_arg;
	fdout = fdout_arg;
	fderr = fderr_arg;

	/* nonblocking IO */
	set_nonblock(fdin);
	set_nonblock(fdout);
	/* we don't have stderr for interactive terminal sessions, see below */
	if (fderr != -1)
		set_nonblock(fderr);

	if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
		fdin_is_tty = 1;

	connection_in = packet_get_connection_in();
	connection_out = packet_get_connection_out();

	notify_setup();

	previous_stdout_buffer_bytes = 0;

	/* Set approximate I/O buffer size. */
	if (packet_is_interactive())
		buffer_high = 4096;
	else
		buffer_high = 64 * 1024;

#if 0
	/* Initialize max_fd to the maximum of the known file descriptors. */
	max_fd = MAX(connection_in, connection_out);
	max_fd = MAX(max_fd, fdin);
	max_fd = MAX(max_fd, fdout);
	if (fderr != -1)
		max_fd = MAX(max_fd, fderr);
#endif

	/* Initialize Initialize buffers. */
	buffer_init(&stdin_buffer);
	buffer_init(&stdout_buffer);
	buffer_init(&stderr_buffer);

	/*
	 * If we have no separate fderr (which is the case when we have a pty
	 * - there we cannot make difference between data sent to stdout and
	 * stderr), indicate that we have seen an EOF from stderr.  This way
	 * we don't need to check the descriptor everywhere.
	 */
	if (fderr == -1)
		fderr_eof = 1;

	server_init_dispatch();

	/* Main loop of the server for the interactive session mode. */
	for (;;) {

		/* Process buffered packets from the client. */
		process_buffered_input_packets();

		/*
		 * If we have received eof, and there is no more pending
		 * input data, cause a real eof by closing fdin.
		 */
		if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
			if (fdin != fdout)
				close(fdin);
			else
				shutdown(fdin, SHUT_WR); /* We will no longer send. */
			fdin = -1;
		}
		/* Make packets from buffered stderr data to send to the client. */
		make_packets_from_stderr_data();

		/*
		 * Make packets from buffered stdout data to send to the
		 * client. If there is very little to send, this arranges to
		 * not send them now, but to wait a short while to see if we
		 * are getting more data. This is necessary, as some systems
		 * wake up readers from a pty after each separate character.
		 */
		max_time_milliseconds = 0;
		stdout_buffer_bytes = buffer_len(&stdout_buffer);
		if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
		    stdout_buffer_bytes != previous_stdout_buffer_bytes) {
			/* try again after a while */
			max_time_milliseconds = 10;
		} else {
			/* Send it now. */
			make_packets_from_stdout_data();
		}
		previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);

		/* Send channel data to the client. */
		if (packet_not_very_much_data_to_write())
			channel_output_poll();

		/*
		 * Bail out of the loop if the program has closed its output
		 * descriptors, and we have no more data to send to the
		 * client, and there is no pending buffered data.
		 */
		if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
		    buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
			if (!channel_still_open())
				break;
			if (!waiting_termination) {
				const char *s = "Waiting for forwarded connections to terminate...\r\n";
				char *cp;
				waiting_termination = 1;
				buffer_append(&stderr_buffer, s, strlen(s));

				/* Display list of open channels. */
				cp = channel_open_message();
				buffer_append(&stderr_buffer, cp, strlen(cp));
				free(cp);
			}
		}
		max_fd = MAX(connection_in, connection_out);
		max_fd = MAX(max_fd, fdin);
		max_fd = MAX(max_fd, fdout);
		max_fd = MAX(max_fd, fderr);
		max_fd = MAX(max_fd, notify_pipe[0]);

		/* Sleep in select() until we can do something. */
		wait_until_can_do_something(&readset, &writeset, &max_fd,
		    &nalloc, max_time_milliseconds);

		if (received_sigterm) {
			logit("Exiting on signal %d", (int)received_sigterm);
			/* Clean up sessions, utmp, etc. */
			cleanup_exit(255);
		}

		/* Process any channel events. */
		channel_after_select(readset, writeset);

		/* Process input from the client and from program stdout/stderr. */
		process_input(readset);

		/* Process output to the client and to program stdin. */
		process_output(writeset);
	}
	free(readset);
	free(writeset);

	/* Cleanup and termination code. */

	/* Wait until all output has been sent to the client. */
	drain_output();

	debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
	    stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);

	/* Free and clear the buffers. */
	buffer_free(&stdin_buffer);
	buffer_free(&stdout_buffer);
	buffer_free(&stderr_buffer);

	/* Close the file descriptors. */
	if (fdout != -1)
		close(fdout);
	fdout = -1;
	fdout_eof = 1;
	if (fderr != -1)
		close(fderr);
	fderr = -1;
	fderr_eof = 1;
	if (fdin != -1)
		close(fdin);
	fdin = -1;

	channel_free_all();

	/* We no longer want our SIGCHLD handler to be called. */
	signal(SIGCHLD, SIG_DFL);

	while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
		if (errno != EINTR)
			packet_disconnect("wait: %.100s", strerror(errno));
	if (wait_pid != pid)
		error("Strange, wait returned pid %ld, expected %ld",
		    (long)wait_pid, (long)pid);

	/* Check if it exited normally. */
	if (WIFEXITED(wait_status)) {
		/* Yes, normal exit.  Get exit status and send it to the client. */
		debug("Command exited with status %d.", WEXITSTATUS(wait_status));
		packet_start(SSH_SMSG_EXITSTATUS);
		packet_put_int(WEXITSTATUS(wait_status));
		packet_send();
		packet_write_wait();

		/*
		 * Wait for exit confirmation.  Note that there might be
		 * other packets coming before it; however, the program has
		 * already died so we just ignore them.  The client is
		 * supposed to respond with the confirmation when it receives
		 * the exit status.
		 */
		do {
			type = packet_read();
		}
		while (type != SSH_CMSG_EXIT_CONFIRMATION);

		debug("Received exit confirmation.");
		return;
	}
	/* Check if the program terminated due to a signal. */
	if (WIFSIGNALED(wait_status))
		packet_disconnect("Command terminated on signal %d.",
				  WTERMSIG(wait_status));

	/* Some weird exit cause.  Just exit. */
	packet_disconnect("wait returned status %04x.", wait_status);
	/* NOTREACHED */
}

static void
collect_children(void)
{
	pid_t pid;
	sigset_t oset, nset;
	int status;

	/* block SIGCHLD while we check for dead children */
	sigemptyset(&nset);
	sigaddset(&nset, SIGCHLD);
	sigprocmask(SIG_BLOCK, &nset, &oset);
	if (child_terminated) {
		debug("Received SIGCHLD.");
		while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
		    (pid < 0 && errno == EINTR))
			if (pid > 0)
				session_close_by_pid(pid, status);
		child_terminated = 0;
	}
	sigprocmask(SIG_SETMASK, &oset, NULL);
}

void
server_loop2(Authctxt *authctxt)
{
	fd_set *readset = NULL, *writeset = NULL;
	int max_fd;
	u_int nalloc = 0;
	u_int64_t rekey_timeout_ms = 0;

	debug("Entering interactive session for SSH2.");

	signal(SIGCHLD, sigchld_handler);
	child_terminated = 0;
	connection_in = packet_get_connection_in();
	connection_out = packet_get_connection_out();

	if (!use_privsep) {
		signal(SIGTERM, sigterm_handler);
		signal(SIGINT, sigterm_handler);
		signal(SIGQUIT, sigterm_handler);
	}

	notify_setup();

	max_fd = MAX(connection_in, connection_out);
	max_fd = MAX(max_fd, notify_pipe[0]);

	server_init_dispatch();

	for (;;) {
		process_buffered_input_packets();

		if (!ssh_packet_is_rekeying(active_state) &&
		    packet_not_very_much_data_to_write())
			channel_output_poll();
		if (options.rekey_interval > 0 && compat20 &&
		    !ssh_packet_is_rekeying(active_state))
			rekey_timeout_ms = packet_get_rekey_timeout() * 1000;
		else
			rekey_timeout_ms = 0;

		wait_until_can_do_something(&readset, &writeset, &max_fd,
		    &nalloc, rekey_timeout_ms);

		if (received_sigterm) {
			logit("Exiting on signal %d", (int)received_sigterm);
			/* Clean up sessions, utmp, etc. */
			cleanup_exit(255);
		}

		collect_children();
		if (!ssh_packet_is_rekeying(active_state))
			channel_after_select(readset, writeset);
		process_input(readset);
		if (connection_closed)
			break;
		process_output(writeset);
	}
	collect_children();

	free(readset);
	free(writeset);

	/* free all channels, no more reads and writes */
	channel_free_all();

	/* free remaining sessions, e.g. remove wtmp entries */
	session_destroy_all(NULL);
}

static int
server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
{
	debug("Got %d/%u for keepalive", type, seq);
	/*
	 * reset timeout, since we got a sane answer from the client.
	 * even if this was generated by something other than
	 * the bogus CHANNEL_REQUEST we send for keepalives.
	 */
	packet_set_alive_timeouts(0);
	return 0;
}

static int
server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
{
	char *data;
	u_int data_len;

	/* Stdin data from the client.  Append it to the buffer. */
	/* Ignore any data if the client has closed stdin. */
	if (fdin == -1)
		return 0;
	data = packet_get_string(&data_len);
	packet_check_eom();
	buffer_append(&stdin_buffer, data, data_len);
	explicit_bzero(data, data_len);
	free(data);
	return 0;
}

static int
server_input_eof(int type, u_int32_t seq, void *ctxt)
{
	/*
	 * Eof from the client.  The stdin descriptor to the
	 * program will be closed when all buffered data has
	 * drained.
	 */
	debug("EOF received for stdin.");
	packet_check_eom();
	stdin_eof = 1;
	return 0;
}

static int
server_input_window_size(int type, u_int32_t seq, void *ctxt)
{
	u_int row = packet_get_int();
	u_int col = packet_get_int();
	u_int xpixel = packet_get_int();
	u_int ypixel = packet_get_int();

	debug("Window change received.");
	packet_check_eom();
	if (fdin != -1)
		pty_change_window_size(fdin, row, col, xpixel, ypixel);
	return 0;
}

static Channel *
server_request_direct_tcpip(void)
{
	Channel *c = NULL;
	char *target, *originator;
	u_short target_port, originator_port;

	target = packet_get_string(NULL);
	target_port = packet_get_int();
	originator = packet_get_string(NULL);
	originator_port = packet_get_int();
	packet_check_eom();

	debug("server_request_direct_tcpip: originator %s port %d, target %s "
	    "port %d", originator, originator_port, target, target_port);

	/* XXX fine grained permissions */
	if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
	    !no_port_forwarding_flag) {
		c = channel_connect_to_port(target, target_port,
		    "direct-tcpip", "direct-tcpip");
	} else {
		logit("refused local port forward: "
		    "originator %s port %d, target %s port %d",
		    originator, originator_port, target, target_port);
	}

	free(originator);
	free(target);

	return c;
}

static Channel *
server_request_direct_streamlocal(void)
{
	Channel *c = NULL;
	char *target, *originator;
	u_short originator_port;

	target = packet_get_string(NULL);
	originator = packet_get_string(NULL);
	originator_port = packet_get_int();
	packet_check_eom();

	debug("server_request_direct_streamlocal: originator %s port %d, target %s",
	    originator, originator_port, target);

	/* XXX fine grained permissions */
	if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
	    !no_port_forwarding_flag) {
		c = channel_connect_to_path(target,
		    "direct-streamlocal@openssh.com", "direct-streamlocal");
	} else {
		logit("refused streamlocal port forward: "
		    "originator %s port %d, target %s",
		    originator, originator_port, target);
	}

	free(originator);
	free(target);

	return c;
}

static Channel *
server_request_tun(void)
{
	Channel *c = NULL;
	int mode, tun;
	int sock;

	mode = packet_get_int();
	switch (mode) {
	case SSH_TUNMODE_POINTOPOINT:
	case SSH_TUNMODE_ETHERNET:
		break;
	default:
		packet_send_debug("Unsupported tunnel device mode.");
		return NULL;
	}
	if ((options.permit_tun & mode) == 0) {
		packet_send_debug("Server has rejected tunnel device "
		    "forwarding");
		return NULL;
	}

	tun = packet_get_int();
	if (forced_tun_device != -1) {
		if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
			goto done;
		tun = forced_tun_device;
	}
	sock = tun_open(tun, mode);
	if (sock < 0)
		goto done;
	c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
	    CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
	c->datagram = 1;

 done:
	if (c == NULL)
		packet_send_debug("Failed to open the tunnel device.");
	return c;
}

static Channel *
server_request_session(void)
{
	Channel *c;

	debug("input_session_request");
	packet_check_eom();

	if (no_more_sessions) {
		packet_disconnect("Possible attack: attempt to open a session "
		    "after additional sessions disabled");
	}

	/*
	 * A server session has no fd to read or write until a
	 * CHANNEL_REQUEST for a shell is made, so we set the type to
	 * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
	 * CHANNEL_REQUEST messages is registered.
	 */
	c = channel_new("session", SSH_CHANNEL_LARVAL,
	    -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
	    0, "server-session", 1);
	if (session_open(the_authctxt, c->self) != 1) {
		debug("session open failed, free channel %d", c->self);
		channel_free(c);
		return NULL;
	}
	channel_register_cleanup(c->self, session_close_by_channel, 0);
	return c;
}

static int
server_input_channel_open(int type, u_int32_t seq, void *ctxt)
{
	Channel *c = NULL;
	char *ctype;
	int rchan;
	u_int rmaxpack, rwindow, len;

	ctype = packet_get_string(&len);
	rchan = packet_get_int();
	rwindow = packet_get_int();
	rmaxpack = packet_get_int();

	debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
	    ctype, rchan, rwindow, rmaxpack);

	if (strcmp(ctype, "session") == 0) {
		c = server_request_session();
	} else if (strcmp(ctype, "direct-tcpip") == 0) {
		c = server_request_direct_tcpip();
	} else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
		c = server_request_direct_streamlocal();
	} else if (strcmp(ctype, "tun@openssh.com") == 0) {
		c = server_request_tun();
	}
	if (c != NULL) {
		debug("server_input_channel_open: confirm %s", ctype);
		c->remote_id = rchan;
		c->remote_window = rwindow;
		c->remote_maxpacket = rmaxpack;
		if (c->type != SSH_CHANNEL_CONNECTING) {
			packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
			packet_put_int(c->remote_id);
			packet_put_int(c->self);
			packet_put_int(c->local_window);
			packet_put_int(c->local_maxpacket);
			packet_send();
		}
	} else {
		debug("server_input_channel_open: failure %s", ctype);
		packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
		packet_put_int(rchan);
		packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
		if (!(datafellows & SSH_BUG_OPENFAILURE)) {
			packet_put_cstring("open failed");
			packet_put_cstring("");
		}
		packet_send();
	}
	free(ctype);
	return 0;
}

static int
server_input_hostkeys_prove(struct sshbuf **respp)
{
	struct ssh *ssh = active_state; /* XXX */
	struct sshbuf *resp = NULL;
	struct sshbuf *sigbuf = NULL;
	struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
	int r, ndx, success = 0;
	const u_char *blob;
	u_char *sig = 0;
	size_t blen, slen;

	if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new", __func__);

	while (ssh_packet_remaining(ssh) > 0) {
		sshkey_free(key);
		key = NULL;
		if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
		    (r = sshkey_from_blob(blob, blen, &key)) != 0) {
			error("%s: couldn't parse key: %s",
			    __func__, ssh_err(r));
			goto out;
		}
		/*
		 * Better check that this is actually one of our hostkeys
		 * before attempting to sign anything with it.
		 */
		if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
			error("%s: unknown host %s key",
			    __func__, sshkey_type(key));
			goto out;
		}
		/*
		 * XXX refactor: make kex->sign just use an index rather
		 * than passing in public and private keys
		 */
		if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
		    (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
			error("%s: can't retrieve hostkey %d", __func__, ndx);
			goto out;
		}
		sshbuf_reset(sigbuf);
		free(sig);
		sig = NULL;
		if ((r = sshbuf_put_cstring(sigbuf,
		    "hostkeys-prove-00@openssh.com")) != 0 ||
		    (r = sshbuf_put_string(sigbuf,
		    ssh->kex->session_id, ssh->kex->session_id_len)) != 0 ||
		    (r = sshkey_puts(key, sigbuf)) != 0 ||
		    (r = ssh->kex->sign(key_prv, key_pub, &sig, &slen,
		    sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), NULL, 0)) != 0 ||
		    (r = sshbuf_put_string(resp, sig, slen)) != 0) {
			error("%s: couldn't prepare signature: %s",
			    __func__, ssh_err(r));
			goto out;
		}
	}
	/* Success */
	*respp = resp;
	resp = NULL; /* don't free it */
	success = 1;
 out:
	free(sig);
	sshbuf_free(resp);
	sshbuf_free(sigbuf);
	sshkey_free(key);
	return success;
}

static int
server_input_global_request(int type, u_int32_t seq, void *ctxt)
{
	char *rtype;
	int want_reply;
	int r, success = 0, allocated_listen_port = 0;
	struct sshbuf *resp = NULL;

	rtype = packet_get_string(NULL);
	want_reply = packet_get_char();
	debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);

	/* -R style forwarding */
	if (strcmp(rtype, "tcpip-forward") == 0) {
		struct passwd *pw;
		struct Forward fwd;

		pw = the_authctxt->pw;
		if (pw == NULL || !the_authctxt->valid)
			fatal("server_input_global_request: no/invalid user");
		memset(&fwd, 0, sizeof(fwd));
		fwd.listen_host = packet_get_string(NULL);
		fwd.listen_port = (u_short)packet_get_int();
		debug("server_input_global_request: tcpip-forward listen %s port %d",
		    fwd.listen_host, fwd.listen_port);

		/* check permissions */
		if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
		    no_port_forwarding_flag ||
		    (!want_reply && fwd.listen_port == 0) ||
		    (fwd.listen_port != 0 && fwd.listen_port < IPPORT_RESERVED &&
		    pw->pw_uid != 0)) {
			success = 0;
			packet_send_debug("Server has disabled port forwarding.");
		} else {
			/* Start listening on the port */
			success = channel_setup_remote_fwd_listener(&fwd,
			    &allocated_listen_port, &options.fwd_opts);
		}
		free(fwd.listen_host);
		if ((resp = sshbuf_new()) == NULL)
			fatal("%s: sshbuf_new", __func__);
		if (allocated_listen_port != 0 &&
		    (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
			fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r));
	} else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
		struct Forward fwd;

		memset(&fwd, 0, sizeof(fwd));
		fwd.listen_host = packet_get_string(NULL);
		fwd.listen_port = (u_short)packet_get_int();
		debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
		    fwd.listen_host, fwd.listen_port);

		success = channel_cancel_rport_listener(&fwd);
		free(fwd.listen_host);
	} else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
		struct Forward fwd;

		memset(&fwd, 0, sizeof(fwd));
		fwd.listen_path = packet_get_string(NULL);
		debug("server_input_global_request: streamlocal-forward listen path %s",
		    fwd.listen_path);

		/* check permissions */
		if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
		    || no_port_forwarding_flag) {
			success = 0;
			packet_send_debug("Server has disabled port forwarding.");
		} else {
			/* Start listening on the socket */
			success = channel_setup_remote_fwd_listener(
			    &fwd, NULL, &options.fwd_opts);
		}
		free(fwd.listen_path);
	} else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
		struct Forward fwd;

		memset(&fwd, 0, sizeof(fwd));
		fwd.listen_path = packet_get_string(NULL);
		debug("%s: cancel-streamlocal-forward path %s", __func__,
		    fwd.listen_path);

		success = channel_cancel_rport_listener(&fwd);
		free(fwd.listen_path);
	} else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
		no_more_sessions = 1;
		success = 1;
	} else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
		success = server_input_hostkeys_prove(&resp);
	}
	if (want_reply) {
		packet_start(success ?
		    SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
		if (success && resp != NULL)
			ssh_packet_put_raw(active_state, sshbuf_ptr(resp),
			    sshbuf_len(resp));
		packet_send();
		packet_write_wait();
	}
	free(rtype);
	sshbuf_free(resp);
	return 0;
}

static int
server_input_channel_req(int type, u_int32_t seq, void *ctxt)
{
	Channel *c;
	int id, reply, success = 0;
	char *rtype;

	id = packet_get_int();
	rtype = packet_get_string(NULL);
	reply = packet_get_char();

	debug("server_input_channel_req: channel %d request %s reply %d",
	    id, rtype, reply);

	if ((c = channel_lookup(id)) == NULL)
		packet_disconnect("server_input_channel_req: "
		    "unknown channel %d", id);
	if (!strcmp(rtype, "eow@openssh.com")) {
		packet_check_eom();
		chan_rcvd_eow(c);
	} else if ((c->type == SSH_CHANNEL_LARVAL ||
	    c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
		success = session_input_channel_req(c, rtype);
	if (reply && !(c->flags & CHAN_CLOSE_SENT)) {
		packet_start(success ?
		    SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
		packet_put_int(c->remote_id);
		packet_send();
	}
	free(rtype);
	return 0;
}

static void
server_init_dispatch_20(void)
{
	debug("server_init_dispatch_20");
	dispatch_init(&dispatch_protocol_error);
	dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
	dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
	dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
	dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
	dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
	dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
	dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
	dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
	dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
	dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
	/* client_alive */
	dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
	dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
	dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
	dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
	/* rekeying */
	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
}
static void
server_init_dispatch_13(void)
{
	debug("server_init_dispatch_13");
	dispatch_init(NULL);
	dispatch_set(SSH_CMSG_EOF, &server_input_eof);
	dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
	dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
	dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
	dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
	dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
	dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
	dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
	dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
}
static void
server_init_dispatch_15(void)
{
	server_init_dispatch_13();
	debug("server_init_dispatch_15");
	dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
	dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
}
static void
server_init_dispatch(void)
{
	if (compat20)
		server_init_dispatch_20();
	else if (compat13)
		server_init_dispatch_13();
	else
		server_init_dispatch_15();
}