[openssh.git] / mux.c

/* $OpenBSD: mux.c,v 1.1 2008/05/09 14:18:44 djm Exp $ */
/*
 * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* ssh session multiplexing support */

#include "includes.h"

#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/un.h>

#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#ifdef HAVE_PATHS_H
#include <paths.h>
#endif

#ifdef HAVE_UTIL_H
# include <util.h>
#endif

#ifdef HAVE_LIBUTIL_H
# include <libutil.h>
#endif

#include "openbsd-compat/sys-queue.h"
#include "xmalloc.h"
#include "log.h"
#include "ssh.h"
#include "pathnames.h"
#include "misc.h"
#include "match.h"
#include "buffer.h"
#include "channels.h"
#include "msg.h"
#include "packet.h"
#include "monitor_fdpass.h"
#include "sshpty.h"
#include "key.h"
#include "readconf.h"
#include "clientloop.h"

/* from ssh.c */
extern int tty_flag;
extern Options options;
extern int stdin_null_flag;
extern char *host;
int subsystem_flag;
extern Buffer command;

/* fd to control socket */
int muxserver_sock = -1;

/* Multiplexing control command */
u_int muxclient_command = 0;

/* Set when signalled. */
static volatile sig_atomic_t muxclient_terminate = 0;

/* PID of multiplex server */
static u_int muxserver_pid = 0;


/* ** Multiplexing master support */

/* Prepare a mux master to listen on a Unix domain socket. */
void
muxserver_listen(void)
{
	struct sockaddr_un addr;
	mode_t old_umask;
	int addr_len;

	if (options.control_path == NULL ||
	    options.control_master == SSHCTL_MASTER_NO)
		return;

	debug("setting up multiplex master socket");

	memset(&addr, '\0', sizeof(addr));
	addr.sun_family = AF_UNIX;
	addr_len = offsetof(struct sockaddr_un, sun_path) +
	    strlen(options.control_path) + 1;

	if (strlcpy(addr.sun_path, options.control_path,
	    sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
		fatal("ControlPath too long");

	if ((muxserver_sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
		fatal("%s socket(): %s", __func__, strerror(errno));

	old_umask = umask(0177);
	if (bind(muxserver_sock, (struct sockaddr *)&addr, addr_len) == -1) {
		muxserver_sock = -1;
		if (errno == EINVAL || errno == EADDRINUSE)
			fatal("ControlSocket %s already exists",
			    options.control_path);
		else
			fatal("%s bind(): %s", __func__, strerror(errno));
	}
	umask(old_umask);

	if (listen(muxserver_sock, 64) == -1)
		fatal("%s listen(): %s", __func__, strerror(errno));

	set_nonblock(muxserver_sock);
}

/* Callback on open confirmation in mux master for a mux client session. */
static void
client_extra_session2_setup(int id, void *arg)
{
	struct mux_session_confirm_ctx *cctx = arg;
	const char *display;
	Channel *c;
	int i;

	if (cctx == NULL)
		fatal("%s: cctx == NULL", __func__);
	if ((c = channel_lookup(id)) == NULL)
		fatal("%s: no channel for id %d", __func__, id);

	display = getenv("DISPLAY");
	if (cctx->want_x_fwd && options.forward_x11 && display != NULL) {
		char *proto, *data;
		/* Get reasonable local authentication information. */
		client_x11_get_proto(display, options.xauth_location,
		    options.forward_x11_trusted, &proto, &data);
		/* Request forwarding with authentication spoofing. */
		debug("Requesting X11 forwarding with authentication spoofing.");
		x11_request_forwarding_with_spoofing(id, display, proto, data);
		/* XXX wait for reply */
	}

	if (cctx->want_agent_fwd && options.forward_agent) {
		debug("Requesting authentication agent forwarding.");
		channel_request_start(id, "auth-agent-req@openssh.com", 0);
		packet_send();
	}

	client_session2_setup(id, cctx->want_tty, cctx->want_subsys,
	    cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env);

	c->open_confirm_ctx = NULL;
	buffer_free(&cctx->cmd);
	xfree(cctx->term);
	if (cctx->env != NULL) {
		for (i = 0; cctx->env[i] != NULL; i++)
			xfree(cctx->env[i]);
		xfree(cctx->env);
	}
	xfree(cctx);
}

/*
 * Accept a connection on the mux master socket and process the
 * client's request. Returns flag indicating whether mux master should
 * begin graceful close.
 */
int
muxserver_accept_control(void)
{
	Buffer m;
	Channel *c;
	int client_fd, new_fd[3], ver, allowed, window, packetmax;
	socklen_t addrlen;
	struct sockaddr_storage addr;
	struct mux_session_confirm_ctx *cctx;
	char *cmd;
	u_int i, j, len, env_len, mux_command, flags;
	uid_t euid;
	gid_t egid;
	int start_close = 0;

	/*
	 * Accept connection on control socket
	 */
	memset(&addr, 0, sizeof(addr));
	addrlen = sizeof(addr);
	if ((client_fd = accept(muxserver_sock,
	    (struct sockaddr*)&addr, &addrlen)) == -1) {
		error("%s accept: %s", __func__, strerror(errno));
		return 0;
	}

	if (getpeereid(client_fd, &euid, &egid) < 0) {
		error("%s getpeereid failed: %s", __func__, strerror(errno));
		close(client_fd);
		return 0;
	}
	if ((euid != 0) && (getuid() != euid)) {
		error("control mode uid mismatch: peer euid %u != uid %u",
		    (u_int) euid, (u_int) getuid());
		close(client_fd);
		return 0;
	}

	/* XXX handle asynchronously */
	unset_nonblock(client_fd);

	/* Read command */
	buffer_init(&m);
	if (ssh_msg_recv(client_fd, &m) == -1) {
		error("%s: client msg_recv failed", __func__);
		close(client_fd);
		buffer_free(&m);
		return 0;
	}
	if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
		error("%s: wrong client version %d", __func__, ver);
		buffer_free(&m);
		close(client_fd);
		return 0;
	}

	allowed = 1;
	mux_command = buffer_get_int(&m);
	flags = buffer_get_int(&m);

	buffer_clear(&m);

	switch (mux_command) {
	case SSHMUX_COMMAND_OPEN:
		if (options.control_master == SSHCTL_MASTER_ASK ||
		    options.control_master == SSHCTL_MASTER_AUTO_ASK)
			allowed = ask_permission("Allow shared connection "
			    "to %s? ", host);
		/* continue below */
		break;
	case SSHMUX_COMMAND_TERMINATE:
		if (options.control_master == SSHCTL_MASTER_ASK ||
		    options.control_master == SSHCTL_MASTER_AUTO_ASK)
			allowed = ask_permission("Terminate shared connection "
			    "to %s? ", host);
		if (allowed)
			start_close = 1;
		/* FALLTHROUGH */
	case SSHMUX_COMMAND_ALIVE_CHECK:
		/* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */
		buffer_clear(&m);
		buffer_put_int(&m, allowed);
		buffer_put_int(&m, getpid());
		if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
			error("%s: client msg_send failed", __func__);
			close(client_fd);
			buffer_free(&m);
			return start_close;
		}
		buffer_free(&m);
		close(client_fd);
		return start_close;
	default:
		error("Unsupported command %d", mux_command);
		buffer_free(&m);
		close(client_fd);
		return 0;
	}

	/* Reply for SSHMUX_COMMAND_OPEN */
	buffer_clear(&m);
	buffer_put_int(&m, allowed);
	buffer_put_int(&m, getpid());
	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
		error("%s: client msg_send failed", __func__);
		close(client_fd);
		buffer_free(&m);
		return 0;
	}

	if (!allowed) {
		error("Refused control connection");
		close(client_fd);
		buffer_free(&m);
		return 0;
	}

	buffer_clear(&m);
	if (ssh_msg_recv(client_fd, &m) == -1) {
		error("%s: client msg_recv failed", __func__);
		close(client_fd);
		buffer_free(&m);
		return 0;
	}
	if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
		error("%s: wrong client version %d", __func__, ver);
		buffer_free(&m);
		close(client_fd);
		return 0;
	}

	cctx = xcalloc(1, sizeof(*cctx));
	cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0;
	cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0;
	cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0;
	cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0;
	cctx->term = buffer_get_string(&m, &len);

	cmd = buffer_get_string(&m, &len);
	buffer_init(&cctx->cmd);
	buffer_append(&cctx->cmd, cmd, strlen(cmd));

	env_len = buffer_get_int(&m);
	env_len = MIN(env_len, 4096);
	debug3("%s: receiving %d env vars", __func__, env_len);
	if (env_len != 0) {
		cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env));
		for (i = 0; i < env_len; i++)
			cctx->env[i] = buffer_get_string(&m, &len);
		cctx->env[i] = NULL;
	}

	debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__,
	    cctx->want_tty, cctx->want_subsys, cmd);
	xfree(cmd);

	/* Gather fds from client */
	for(i = 0; i < 3; i++) {
		if ((new_fd[i] = mm_receive_fd(client_fd)) == -1) {
			error("%s: failed to receive fd %d from slave",
			    __func__, i);
			for (j = 0; j < i; j++)
				close(new_fd[j]);
			for (j = 0; j < env_len; j++)
				xfree(cctx->env[j]);
			if (env_len > 0)
				xfree(cctx->env);
			xfree(cctx->term);
			buffer_free(&cctx->cmd);
			close(client_fd);
			xfree(cctx);
			return 0;
		}
	}

	debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__,
	    new_fd[0], new_fd[1], new_fd[2]);

	/* Try to pick up ttymodes from client before it goes raw */
	if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1)
		error("%s: tcgetattr: %s", __func__, strerror(errno));

	/* This roundtrip is just for synchronisation of ttymodes */
	buffer_clear(&m);
	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
		error("%s: client msg_send failed", __func__);
		close(client_fd);
		close(new_fd[0]);
		close(new_fd[1]);
		close(new_fd[2]);
		buffer_free(&m);
		xfree(cctx->term);
		if (env_len != 0) {
			for (i = 0; i < env_len; i++)
				xfree(cctx->env[i]);
			xfree(cctx->env);
		}
		return 0;
	}
	buffer_free(&m);

	/* enable nonblocking unless tty */
	if (!isatty(new_fd[0]))
		set_nonblock(new_fd[0]);
	if (!isatty(new_fd[1]))
		set_nonblock(new_fd[1]);
	if (!isatty(new_fd[2]))
		set_nonblock(new_fd[2]);

	set_nonblock(client_fd);

	window = CHAN_SES_WINDOW_DEFAULT;
	packetmax = CHAN_SES_PACKET_DEFAULT;
	if (cctx->want_tty) {
		window >>= 1;
		packetmax >>= 1;
	}
	
	c = channel_new("session", SSH_CHANNEL_OPENING,
	    new_fd[0], new_fd[1], new_fd[2], window, packetmax,
	    CHAN_EXTENDED_WRITE, "client-session", /*nonblock*/0);

	/* XXX */
	c->ctl_fd = client_fd;

	debug3("%s: channel_new: %d", __func__, c->self);

	channel_send_open(c->self);
	channel_register_open_confirm(c->self,
	    client_extra_session2_setup, cctx);
	return 0;
}

/* ** Multiplexing client support */

/* Exit signal handler */
static void
control_client_sighandler(int signo)
{
	muxclient_terminate = signo;
}

/*
 * Relay signal handler - used to pass some signals from mux client to
 * mux master.
 */
static void
control_client_sigrelay(int signo)
{
	int save_errno = errno;

	if (muxserver_pid > 1)
		kill(muxserver_pid, signo);

	errno = save_errno;
}

/* Check mux client environment variables before passing them to mux master. */
static int
env_permitted(char *env)
{
	int i, ret;
	char name[1024], *cp;

	if ((cp = strchr(env, '=')) == NULL || cp == env)
		return (0);
	ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
	if (ret <= 0 || (size_t)ret >= sizeof(name))
		fatal("env_permitted: name '%.100s...' too long", env);

	for (i = 0; i < options.num_send_env; i++)
		if (match_pattern(name, options.send_env[i]))
			return (1);

	return (0);
}

/* Multiplex client main loop. */
void
muxclient(const char *path)
{
	struct sockaddr_un addr;
	int i, r, fd, sock, exitval[2], num_env, addr_len;
	Buffer m;
	char *term;
	extern char **environ;
	u_int  flags;

	if (muxclient_command == 0)
		muxclient_command = SSHMUX_COMMAND_OPEN;

	switch (options.control_master) {
	case SSHCTL_MASTER_AUTO:
	case SSHCTL_MASTER_AUTO_ASK:
		debug("auto-mux: Trying existing master");
		/* FALLTHROUGH */
	case SSHCTL_MASTER_NO:
		break;
	default:
		return;
	}

	memset(&addr, '\0', sizeof(addr));
	addr.sun_family = AF_UNIX;
	addr_len = offsetof(struct sockaddr_un, sun_path) +
	    strlen(path) + 1;

	if (strlcpy(addr.sun_path, path,
	    sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
		fatal("ControlPath too long");

	if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
		fatal("%s socket(): %s", __func__, strerror(errno));

	if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
		if (muxclient_command != SSHMUX_COMMAND_OPEN) {
			fatal("Control socket connect(%.100s): %s", path,
			    strerror(errno));
		}
		if (errno == ENOENT)
			debug("Control socket \"%.100s\" does not exist", path);
		else {
			error("Control socket connect(%.100s): %s", path,
			    strerror(errno));
		}
		close(sock);
		return;
	}

	if (stdin_null_flag) {
		if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
			fatal("open(/dev/null): %s", strerror(errno));
		if (dup2(fd, STDIN_FILENO) == -1)
			fatal("dup2: %s", strerror(errno));
		if (fd > STDERR_FILENO)
			close(fd);
	}

	term = getenv("TERM");

	flags = 0;
	if (tty_flag)
		flags |= SSHMUX_FLAG_TTY;
	if (subsystem_flag)
		flags |= SSHMUX_FLAG_SUBSYS;
	if (options.forward_x11)
		flags |= SSHMUX_FLAG_X11_FWD;
	if (options.forward_agent)
		flags |= SSHMUX_FLAG_AGENT_FWD;

	signal(SIGPIPE, SIG_IGN);

	buffer_init(&m);

	/* Send our command to server */
	buffer_put_int(&m, muxclient_command);
	buffer_put_int(&m, flags);
	if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
		fatal("%s: msg_send", __func__);
	buffer_clear(&m);

	/* Get authorisation status and PID of controlee */
	if (ssh_msg_recv(sock, &m) == -1)
		fatal("%s: msg_recv", __func__);
	if (buffer_get_char(&m) != SSHMUX_VER)
		fatal("%s: wrong version", __func__);
	if (buffer_get_int(&m) != 1)
		fatal("Connection to master denied");
	muxserver_pid = buffer_get_int(&m);

	buffer_clear(&m);

	switch (muxclient_command) {
	case SSHMUX_COMMAND_ALIVE_CHECK:
		fprintf(stderr, "Master running (pid=%d)\r\n",
		    muxserver_pid);
		exit(0);
	case SSHMUX_COMMAND_TERMINATE:
		fprintf(stderr, "Exit request sent.\r\n");
		exit(0);
	case SSHMUX_COMMAND_OPEN:
		/* continue below */
		break;
	default:
		fatal("silly muxclient_command %d", muxclient_command);
	}

	/* SSHMUX_COMMAND_OPEN */
	buffer_put_cstring(&m, term ? term : "");
	buffer_append(&command, "\0", 1);
	buffer_put_cstring(&m, buffer_ptr(&command));

	if (options.num_send_env == 0 || environ == NULL) {
		buffer_put_int(&m, 0);
	} else {
		/* Pass environment */
		num_env = 0;
		for (i = 0; environ[i] != NULL; i++)
			if (env_permitted(environ[i]))
				num_env++; /* Count */

		buffer_put_int(&m, num_env);

		for (i = 0; environ[i] != NULL && num_env >= 0; i++)
			if (env_permitted(environ[i])) {
				num_env--;
				buffer_put_cstring(&m, environ[i]);
			}
	}

	if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
		fatal("%s: msg_send", __func__);

	if (mm_send_fd(sock, STDIN_FILENO) == -1 ||
	    mm_send_fd(sock, STDOUT_FILENO) == -1 ||
	    mm_send_fd(sock, STDERR_FILENO) == -1)
		fatal("%s: send fds failed", __func__);

	/* Wait for reply, so master has a chance to gather ttymodes */
	buffer_clear(&m);
	if (ssh_msg_recv(sock, &m) == -1)
		fatal("%s: msg_recv", __func__);
	if (buffer_get_char(&m) != SSHMUX_VER)
		fatal("%s: wrong version", __func__);
	buffer_free(&m);

	signal(SIGHUP, control_client_sighandler);
	signal(SIGINT, control_client_sighandler);
	signal(SIGTERM, control_client_sighandler);
	signal(SIGWINCH, control_client_sigrelay);

	if (tty_flag)
		enter_raw_mode();

	/*
	 * Stick around until the controlee closes the client_fd.
	 * Before it does, it is expected to write this process' exit
	 * value (one int). This process must read the value and wait for
	 * the closure of the client_fd; if this one closes early, the 
	 * multiplex master will terminate early too (possibly losing data).
	 */
	exitval[0] = 0;
	for (i = 0; !muxclient_terminate && i < (int)sizeof(exitval);) {
		r = read(sock, (char *)exitval + i, sizeof(exitval) - i);
		if (r == 0) {
			debug2("Received EOF from master");
			break;
		}
		if (r == -1) {
			if (errno == EINTR)
				continue;
			fatal("%s: read %s", __func__, strerror(errno));
		}
		i += r;
	}

	close(sock);
	leave_raw_mode();
	if (i > (int)sizeof(int))
		fatal("%s: master returned too much data (%d > %lu)",
		    __func__, i, sizeof(int));
	if (muxclient_terminate) {
		debug2("Exiting on signal %d", muxclient_terminate);
		exitval[0] = 255;
	} else if (i < (int)sizeof(int)) {
		debug2("Control master terminated unexpectedly");
		exitval[0] = 255;
	} else
		debug2("Received exit status from master %d", exitval[0]);

	if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
		fprintf(stderr, "Shared connection to %s closed.\r\n", host);

	exit(exitval[0]);
}
Commit	Line	Data
3bcced4c	1	/* $OpenBSD: mux.c,v 1.1 2008/05/09 14:18:44 djm Exp $ */
	2	/*
	3	* Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
	4	*
	5	* Permission to use, copy, modify, and distribute this software for any
	6	* purpose with or without fee is hereby granted, provided that the above
	7	* copyright notice and this permission notice appear in all copies.
	8	*
	9	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	10	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	11	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	12	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	13	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	14	* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	15	* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	16	*/
	17
	18	/* ssh session multiplexing support */
	19
b3ef88dc	20	#include "includes.h"
b3ef88dc	21
3bcced4c	22	#include <sys/types.h>
	23	#include <sys/param.h>
	24	#include <sys/stat.h>
	25	#include <sys/socket.h>
	26	#include <sys/un.h>
	27
	28	#include <errno.h>
	29	#include <fcntl.h>
	30	#include <signal.h>
	31	#include <stdarg.h>
	32	#include <stddef.h>
	33	#include <stdlib.h>
	34	#include <stdio.h>
	35	#include <string.h>
	36	#include <unistd.h>
0894bbed	37	#ifdef HAVE_PATHS_H
3bcced4c	38	#include <paths.h>
0894bbed	39	#endif
3bcced4c	40
b3ef88dc	41	#ifdef HAVE_UTIL_H
	42	# include <util.h>
	43	#endif
	44
	45	#ifdef HAVE_LIBUTIL_H
	46	# include <libutil.h>
	47	#endif
	48
3bcced4c	49	#include "openbsd-compat/sys-queue.h"
	50	#include "xmalloc.h"
	51	#include "log.h"
	52	#include "ssh.h"
	53	#include "pathnames.h"
	54	#include "misc.h"
	55	#include "match.h"
	56	#include "buffer.h"
	57	#include "channels.h"
	58	#include "msg.h"
	59	#include "packet.h"
	60	#include "monitor_fdpass.h"
	61	#include "sshpty.h"
	62	#include "key.h"
	63	#include "readconf.h"
	64	#include "clientloop.h"
	65
	66	/* from ssh.c */
	67	extern int tty_flag;
	68	extern Options options;
	69	extern int stdin_null_flag;
	70	extern char *host;
	71	int subsystem_flag;
	72	extern Buffer command;
	73
	74	/* fd to control socket */
	75	int muxserver_sock = -1;
	76
	77	/* Multiplexing control command */
	78	u_int muxclient_command = 0;
	79
	80	/* Set when signalled. */
	81	static volatile sig_atomic_t muxclient_terminate = 0;
	82
	83	/* PID of multiplex server */
	84	static u_int muxserver_pid = 0;
	85
	86
	87	/* ** Multiplexing master support */
	88
	89	/* Prepare a mux master to listen on a Unix domain socket. */
	90	void
	91	muxserver_listen(void)
	92	{
	93	struct sockaddr_un addr;
	94	mode_t old_umask;
	95	int addr_len;
	96
	97	if (options.control_path == NULL \|\|
	98	options.control_master == SSHCTL_MASTER_NO)
	99	return;
	100
	101	debug("setting up multiplex master socket");
	102
	103	memset(&addr, '\0', sizeof(addr));
	104	addr.sun_family = AF_UNIX;
	105	addr_len = offsetof(struct sockaddr_un, sun_path) +
	106	strlen(options.control_path) + 1;
	107
	108	if (strlcpy(addr.sun_path, options.control_path,
	109	sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
	110	fatal("ControlPath too long");
	111
	112	if ((muxserver_sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
113	fatal("%s socket(): %s", __func__, strerror(errno));
114
115	old_umask = umask(0177);
116	if (bind(muxserver_sock, (struct sockaddr *)&addr, addr_len) == -1) {
117	muxserver_sock = -1;
118	if (errno == EINVAL \|\| errno == EADDRINUSE)
119	fatal("ControlSocket %s already exists",
120	options.control_path);
121	else
122	fatal("%s bind(): %s", __func__, strerror(errno));
123	}
124	umask(old_umask);
125
126	if (listen(muxserver_sock, 64) == -1)
127	fatal("%s listen(): %s", __func__, strerror(errno));
128
129	set_nonblock(muxserver_sock);
130	}
131
132	/* Callback on open confirmation in mux master for a mux client session. */
133	static void
134	client_extra_session2_setup(int id, void *arg)
135	{
136	struct mux_session_confirm_ctx *cctx = arg;
137	const char *display;
138	Channel *c;
139	int i;
140
141	if (cctx == NULL)
142	fatal("%s: cctx == NULL", __func__);
143	if ((c = channel_lookup(id)) == NULL)
144	fatal("%s: no channel for id %d", __func__, id);
145
146	display = getenv("DISPLAY");
147	if (cctx->want_x_fwd && options.forward_x11 && display != NULL) {
148	char proto, data;
149	/* Get reasonable local authentication information. */
150	client_x11_get_proto(display, options.xauth_location,
151	options.forward_x11_trusted, &proto, &data);
152	/* Request forwarding with authentication spoofing. */
153	debug("Requesting X11 forwarding with authentication spoofing.");
154	x11_request_forwarding_with_spoofing(id, display, proto, data);
155	/* XXX wait for reply */
156	}
157
158	if (cctx->want_agent_fwd && options.forward_agent) {
159	debug("Requesting authentication agent forwarding.");
160	channel_request_start(id, "auth-agent-req@openssh.com", 0);
161	packet_send();
162	}
163
164	client_session2_setup(id, cctx->want_tty, cctx->want_subsys,
165	cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env);
166
167	c->open_confirm_ctx = NULL;
168	buffer_free(&cctx->cmd);
169	xfree(cctx->term);
170	if (cctx->env != NULL) {
171	for (i = 0; cctx->env[i] != NULL; i++)
172	xfree(cctx->env[i]);
173	xfree(cctx->env);
174	}
175	xfree(cctx);
176	}
177
178	/*
179	* Accept a connection on the mux master socket and process the
180	* client's request. Returns flag indicating whether mux master should
181	* begin graceful close.
182	*/
183	int
184	muxserver_accept_control(void)
185	{
186	Buffer m;
187	Channel *c;
188	int client_fd, new_fd[3], ver, allowed, window, packetmax;
189	socklen_t addrlen;
190	struct sockaddr_storage addr;
191	struct mux_session_confirm_ctx *cctx;
192	char *cmd;
193	u_int i, j, len, env_len, mux_command, flags;
194	uid_t euid;
195	gid_t egid;
196	int start_close = 0;
197
198	/*
199	* Accept connection on control socket
200	*/
201	memset(&addr, 0, sizeof(addr));
202	addrlen = sizeof(addr);
203	if ((client_fd = accept(muxserver_sock,
204	(struct sockaddr*)&addr, &addrlen)) == -1) {
205	error("%s accept: %s", __func__, strerror(errno));
206	return 0;
207	}
208
209	if (getpeereid(client_fd, &euid, &egid) < 0) {
210	error("%s getpeereid failed: %s", __func__, strerror(errno));
211	close(client_fd);
212	return 0;
213	}
214	if ((euid != 0) && (getuid() != euid)) {
215	error("control mode uid mismatch: peer euid %u != uid %u",
216	(u_int) euid, (u_int) getuid());
217	close(client_fd);
218	return 0;
219	}
220
221	/* XXX handle asynchronously */
222	unset_nonblock(client_fd);
223
224	/* Read command */
225	buffer_init(&m);
226	if (ssh_msg_recv(client_fd, &m) == -1) {
227	error("%s: client msg_recv failed", __func__);
228	close(client_fd);
229	buffer_free(&m);
230	return 0;
231	}
232	if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
233	error("%s: wrong client version %d", __func__, ver);
234	buffer_free(&m);
235	close(client_fd);
236	return 0;
237	}
238
239	allowed = 1;
240	mux_command = buffer_get_int(&m);
241	flags = buffer_get_int(&m);
242
243	buffer_clear(&m);
244
245	switch (mux_command) {
246	case SSHMUX_COMMAND_OPEN:
247	if (options.control_master == SSHCTL_MASTER_ASK \|\|
248	options.control_master == SSHCTL_MASTER_AUTO_ASK)
249	allowed = ask_permission("Allow shared connection "
250	"to %s? ", host);
251	/* continue below */
252	break;
253	case SSHMUX_COMMAND_TERMINATE:
254	if (options.control_master == SSHCTL_MASTER_ASK \|\|
255	options.control_master == SSHCTL_MASTER_AUTO_ASK)
256	allowed = ask_permission("Terminate shared connection "
257	"to %s? ", host);
258	if (allowed)
259	start_close = 1;
260	/* FALLTHROUGH */
261	case SSHMUX_COMMAND_ALIVE_CHECK:
262	/* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */
263	buffer_clear(&m);
264	buffer_put_int(&m, allowed);
265	buffer_put_int(&m, getpid());
266	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
267	error("%s: client msg_send failed", __func__);
268	close(client_fd);
269	buffer_free(&m);
270	return start_close;
271	}
272	buffer_free(&m);
273	close(client_fd);
274	return start_close;
275	default:
276	error("Unsupported command %d", mux_command);
277	buffer_free(&m);
278	close(client_fd);
279	return 0;
280	}
281
282	/* Reply for SSHMUX_COMMAND_OPEN */
283	buffer_clear(&m);
284	buffer_put_int(&m, allowed);
285	buffer_put_int(&m, getpid());
286	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
287	error("%s: client msg_send failed", __func__);
288	close(client_fd);
289	buffer_free(&m);
290	return 0;
291	}
292
293	if (!allowed) {
294	error("Refused control connection");
295	close(client_fd);
296	buffer_free(&m);
297	return 0;
298	}
299
300	buffer_clear(&m);
301	if (ssh_msg_recv(client_fd, &m) == -1) {
302	error("%s: client msg_recv failed", __func__);
303	close(client_fd);
304	buffer_free(&m);
305	return 0;
306	}
307	if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
308	error("%s: wrong client version %d", __func__, ver);
309	buffer_free(&m);
310	close(client_fd);
311	return 0;
312	}
313
314	cctx = xcalloc(1, sizeof(*cctx));
315	cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0;
316	cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0;
317	cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0;
318	cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0;
319	cctx->term = buffer_get_string(&m, &len);
320
321	cmd = buffer_get_string(&m, &len);
322	buffer_init(&cctx->cmd);
323	buffer_append(&cctx->cmd, cmd, strlen(cmd));
324
325	env_len = buffer_get_int(&m);
326	env_len = MIN(env_len, 4096);
327	debug3("%s: receiving %d env vars", __func__, env_len);
328	if (env_len != 0) {
329	cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env));
330	for (i = 0; i < env_len; i++)
331	cctx->env[i] = buffer_get_string(&m, &len);
332	cctx->env[i] = NULL;
333	}
334
335	debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__,
336	cctx->want_tty, cctx->want_subsys, cmd);
337	xfree(cmd);
338
339	/* Gather fds from client */
340	for(i = 0; i < 3; i++) {
341	if ((new_fd[i] = mm_receive_fd(client_fd)) == -1) {
342	error("%s: failed to receive fd %d from slave",
343	__func__, i);
344	for (j = 0; j < i; j++)
345	close(new_fd[j]);
346	for (j = 0; j < env_len; j++)
347	xfree(cctx->env[j]);
348	if (env_len > 0)
349	xfree(cctx->env);
350	xfree(cctx->term);
351	buffer_free(&cctx->cmd);
352	close(client_fd);
353	xfree(cctx);
354	return 0;
355	}
356	}
357
358	debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__,
359	new_fd[0], new_fd[1], new_fd[2]);
360
361	/* Try to pick up ttymodes from client before it goes raw */
362	if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1)
363	error("%s: tcgetattr: %s", __func__, strerror(errno));
364
365	/* This roundtrip is just for synchronisation of ttymodes */
366	buffer_clear(&m);
367	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
368	error("%s: client msg_send failed", __func__);
369	close(client_fd);
370	close(new_fd[0]);
371	close(new_fd[1]);
372	close(new_fd[2]);
373	buffer_free(&m);
374	xfree(cctx->term);
375	if (env_len != 0) {
376	for (i = 0; i < env_len; i++)
377	xfree(cctx->env[i]);
378	xfree(cctx->env);
379	}
380	return 0;
381	}
382	buffer_free(&m);
383
384	/* enable nonblocking unless tty */
385	if (!isatty(new_fd[0]))
386	set_nonblock(new_fd[0]);
387	if (!isatty(new_fd[1]))
388	set_nonblock(new_fd[1]);
389	if (!isatty(new_fd[2]))
390	set_nonblock(new_fd[2]);
391
392	set_nonblock(client_fd);
393
394	window = CHAN_SES_WINDOW_DEFAULT;
395	packetmax = CHAN_SES_PACKET_DEFAULT;
396	if (cctx->want_tty) {
397	window >>= 1;
398	packetmax >>= 1;
399	}
400
401	c = channel_new("session", SSH_CHANNEL_OPENING,
402	new_fd[0], new_fd[1], new_fd[2], window, packetmax,
403	CHAN_EXTENDED_WRITE, "client-session", /nonblock/0);
404
405	/* XXX */
406	c->ctl_fd = client_fd;
407
408	debug3("%s: channel_new: %d", __func__, c->self);
409
410	channel_send_open(c->self);
411	channel_register_open_confirm(c->self,
412	client_extra_session2_setup, cctx);
413	return 0;
414	}
415
416	/* ** Multiplexing client support */
417
418	/* Exit signal handler */
419	static void
420	control_client_sighandler(int signo)
421	{
422	muxclient_terminate = signo;
423	}
424
425	/*
426	* Relay signal handler - used to pass some signals from mux client to
427	* mux master.
428	*/
429	static void
430	control_client_sigrelay(int signo)
431	{
432	int save_errno = errno;
433
434	if (muxserver_pid > 1)
435	kill(muxserver_pid, signo);
436
437	errno = save_errno;
438	}
439
440	/* Check mux client environment variables before passing them to mux master. */
441	static int
442	env_permitted(char *env)
443	{
444	int i, ret;
445	char name[1024], *cp;
446
447	if ((cp = strchr(env, '=')) == NULL \|\| cp == env)
448	return (0);
449	ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
450	if (ret <= 0 \|\| (size_t)ret >= sizeof(name))
451	fatal("env_permitted: name '%.100s...' too long", env);
452
453	for (i = 0; i < options.num_send_env; i++)
454	if (match_pattern(name, options.send_env[i]))
455	return (1);
456
457	return (0);
458	}
459
460	/* Multiplex client main loop. */
461	void
462	muxclient(const char *path)
463	{
464	struct sockaddr_un addr;
465	int i, r, fd, sock, exitval[2], num_env, addr_len;
466	Buffer m;
467	char *term;
468	extern char **environ;
469	u_int flags;
470
471	if (muxclient_command == 0)
472	muxclient_command = SSHMUX_COMMAND_OPEN;
473
474	switch (options.control_master) {
475	case SSHCTL_MASTER_AUTO:
476	case SSHCTL_MASTER_AUTO_ASK:
477	debug("auto-mux: Trying existing master");
478	/* FALLTHROUGH */
479	case SSHCTL_MASTER_NO:
480	break;
481	default:
482	return;
483	}
484
485	memset(&addr, '\0', sizeof(addr));
486	addr.sun_family = AF_UNIX;
487	addr_len = offsetof(struct sockaddr_un, sun_path) +
488	strlen(path) + 1;
489
490	if (strlcpy(addr.sun_path, path,
491	sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
492	fatal("ControlPath too long");
493
494	if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
495	fatal("%s socket(): %s", __func__, strerror(errno));
496
497	if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
498	if (muxclient_command != SSHMUX_COMMAND_OPEN) {
499	fatal("Control socket connect(%.100s): %s", path,
500	strerror(errno));
501	}
502	if (errno == ENOENT)
503	debug("Control socket \"%.100s\" does not exist", path);
504	else {
505	error("Control socket connect(%.100s): %s", path,
506	strerror(errno));
507	}
508	close(sock);
509	return;
510	}
511
512	if (stdin_null_flag) {
513	if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
514	fatal("open(/dev/null): %s", strerror(errno));
515	if (dup2(fd, STDIN_FILENO) == -1)
516	fatal("dup2: %s", strerror(errno));
517	if (fd > STDERR_FILENO)
518	close(fd);
519	}
520
521	term = getenv("TERM");
522
523	flags = 0;
524	if (tty_flag)
525	flags \|= SSHMUX_FLAG_TTY;
526	if (subsystem_flag)
527	flags \|= SSHMUX_FLAG_SUBSYS;
528	if (options.forward_x11)
529	flags \|= SSHMUX_FLAG_X11_FWD;
530	if (options.forward_agent)
531	flags \|= SSHMUX_FLAG_AGENT_FWD;
532
533	signal(SIGPIPE, SIG_IGN);
534
535	buffer_init(&m);
536
537	/* Send our command to server */
538	buffer_put_int(&m, muxclient_command);
539	buffer_put_int(&m, flags);
540	if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
541	fatal("%s: msg_send", __func__);
542	buffer_clear(&m);
543
544	/* Get authorisation status and PID of controlee */
545	if (ssh_msg_recv(sock, &m) == -1)
546	fatal("%s: msg_recv", __func__);
547	if (buffer_get_char(&m) != SSHMUX_VER)
548	fatal("%s: wrong version", __func__);
549	if (buffer_get_int(&m) != 1)
550	fatal("Connection to master denied");
551	muxserver_pid = buffer_get_int(&m);
552
553	buffer_clear(&m);
554
555	switch (muxclient_command) {
556	case SSHMUX_COMMAND_ALIVE_CHECK:
557	fprintf(stderr, "Master running (pid=%d)\r\n",
558	muxserver_pid);
559	exit(0);
560	case SSHMUX_COMMAND_TERMINATE:
561	fprintf(stderr, "Exit request sent.\r\n");
562	exit(0);
563	case SSHMUX_COMMAND_OPEN:
564	/* continue below */
565	break;
566	default:
567	fatal("silly muxclient_command %d", muxclient_command);
568	}
569
570	/* SSHMUX_COMMAND_OPEN */
571	buffer_put_cstring(&m, term ? term : "");
572	buffer_append(&command, "\0", 1);
573	buffer_put_cstring(&m, buffer_ptr(&command));
574
575	if (options.num_send_env == 0 \|\| environ == NULL) {
576	buffer_put_int(&m, 0);
577	} else {
578	/* Pass environment */
579	num_env = 0;
580	for (i = 0; environ[i] != NULL; i++)
581	if (env_permitted(environ[i]))
582	num_env++; /* Count */
583
584	buffer_put_int(&m, num_env);
585
586	for (i = 0; environ[i] != NULL && num_env >= 0; i++)
587	if (env_permitted(environ[i])) {
588	num_env--;
589	buffer_put_cstring(&m, environ[i]);
590	}
591	}
592
593	if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
594	fatal("%s: msg_send", __func__);
595
596	if (mm_send_fd(sock, STDIN_FILENO) == -1 \|\|
597	mm_send_fd(sock, STDOUT_FILENO) == -1 \|\|
598	mm_send_fd(sock, STDERR_FILENO) == -1)
599	fatal("%s: send fds failed", __func__);
600
601	/* Wait for reply, so master has a chance to gather ttymodes */
602	buffer_clear(&m);
603	if (ssh_msg_recv(sock, &m) == -1)
604	fatal("%s: msg_recv", __func__);
605	if (buffer_get_char(&m) != SSHMUX_VER)
606	fatal("%s: wrong version", __func__);
607	buffer_free(&m);
608
609	signal(SIGHUP, control_client_sighandler);
610	signal(SIGINT, control_client_sighandler);
611	signal(SIGTERM, control_client_sighandler);
612	signal(SIGWINCH, control_client_sigrelay);
613
614	if (tty_flag)
615	enter_raw_mode();
616
617	/*
618	* Stick around until the controlee closes the client_fd.
619	* Before it does, it is expected to write this process' exit
620	* value (one int). This process must read the value and wait for
621	* the closure of the client_fd; if this one closes early, the
622	* multiplex master will terminate early too (possibly losing data).
623	*/
624	exitval[0] = 0;
625	for (i = 0; !muxclient_terminate && i < (int)sizeof(exitval);) {
626	r = read(sock, (char *)exitval + i, sizeof(exitval) - i);
627	if (r == 0) {
628	debug2("Received EOF from master");
629	break;
630	}
631	if (r == -1) {
632	if (errno == EINTR)
633	continue;
634	fatal("%s: read %s", __func__, strerror(errno));
635	}
636	i += r;
637	}
638
639	close(sock);
640	leave_raw_mode();
641	if (i > (int)sizeof(int))
642	fatal("%s: master returned too much data (%d > %lu)",
643	__func__, i, sizeof(int));
644	if (muxclient_terminate) {
645	debug2("Exiting on signal %d", muxclient_terminate);
646	exitval[0] = 255;
647	} else if (i < (int)sizeof(int)) {
648	debug2("Control master terminated unexpectedly");
649	exitval[0] = 255;
650	} else
651	debug2("Received exit status from master %d", exitval[0]);
652
653	if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
654	fprintf(stderr, "Shared connection to %s closed.\r\n", host);
655
656	exit(exitval[0]);
657	}