[openssh.git] / mux.c

/* $OpenBSD: mux.c,v 1.2 2008/06/12 03:40:52 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"

/*
 * TODO:
 *   1. partial reads in muxserver_accept_control (maybe make channels
 *      from accepted connections)
 *   2. Better signalling from master to slave, especially passing of
 *      error messages
 *   3. Better fall-back from mux slave error to new connection.
 *   3. Add/delete forwardings via slave
 *   4. ExitOnForwardingFailure (after #3 obviously)
 *   5. Maybe extension mechanisms for multi-X11/multi-agent forwarding
 *   6. Document the mux mini-protocol somewhere.
 *   6. Support ~^Z in mux slaves.
 */

#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;

/* Context for session open confirmation callback */
struct mux_session_confirm_ctx {
	int want_tty;
	int want_subsys;
	int want_x_fwd;
	int want_agent_fwd;
	Buffer cmd;
	char *term;
	struct termios tio;
	char **env;
};

/* 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
mux_session_confirm(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, escape_char;
	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);
	escape_char = buffer_get_int(&m);

	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);

	c->ctl_fd = client_fd;
	if (cctx->want_tty && escape_char != 0xffffffff) {
		channel_register_filter(c->self,
		    client_simple_escape_filter, NULL,
		    client_new_escape_filter_ctx((int)escape_char));
	}

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

	channel_send_open(c->self);
	channel_register_open_confirm(c->self, mux_session_confirm, 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:
		buffer_put_cstring(&m, term ? term : "");
		if (options.escape_char == SSH_ESCAPECHAR_NONE)
			buffer_put_int(&m, 0xffffffff);
		else
			buffer_put_int(&m, options.escape_char);
		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]);
				}
			}
		}
		break;
	default:
		fatal("unrecognised muxclient_command %d", muxclient_command);
	}

	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
f17f705b	1	/* $OpenBSD: mux.c,v 1.2 2008/06/12 03:40:52 djm Exp $ */
3bcced4c	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
f17f705b	22	/*
	23	* TODO:
	24	* 1. partial reads in muxserver_accept_control (maybe make channels
	25	* from accepted connections)
	26	* 2. Better signalling from master to slave, especially passing of
	27	* error messages
	28	* 3. Better fall-back from mux slave error to new connection.
	29	* 3. Add/delete forwardings via slave
	30	* 4. ExitOnForwardingFailure (after #3 obviously)
	31	* 5. Maybe extension mechanisms for multi-X11/multi-agent forwarding
	32	* 6. Document the mux mini-protocol somewhere.
	33	* 6. Support ~^Z in mux slaves.
	34	*/
	35
3bcced4c	36	#include <sys/types.h>
	37	#include <sys/param.h>
	38	#include <sys/stat.h>
	39	#include <sys/socket.h>
	40	#include <sys/un.h>
	41
	42	#include <errno.h>
	43	#include <fcntl.h>
	44	#include <signal.h>
	45	#include <stdarg.h>
	46	#include <stddef.h>
	47	#include <stdlib.h>
	48	#include <stdio.h>
	49	#include <string.h>
	50	#include <unistd.h>
0894bbed	51	#ifdef HAVE_PATHS_H
3bcced4c	52	#include <paths.h>
0894bbed	53	#endif
3bcced4c	54
b3ef88dc	55	#ifdef HAVE_UTIL_H
	56	# include <util.h>
	57	#endif
	58
	59	#ifdef HAVE_LIBUTIL_H
	60	# include <libutil.h>
	61	#endif
	62
3bcced4c	63	#include "openbsd-compat/sys-queue.h"
	64	#include "xmalloc.h"
	65	#include "log.h"
	66	#include "ssh.h"
	67	#include "pathnames.h"
	68	#include "misc.h"
	69	#include "match.h"
	70	#include "buffer.h"
	71	#include "channels.h"
	72	#include "msg.h"
	73	#include "packet.h"
	74	#include "monitor_fdpass.h"
	75	#include "sshpty.h"
	76	#include "key.h"
	77	#include "readconf.h"
	78	#include "clientloop.h"
	79
	80	/* from ssh.c */
	81	extern int tty_flag;
	82	extern Options options;
	83	extern int stdin_null_flag;
	84	extern char *host;
	85	int subsystem_flag;
	86	extern Buffer command;
	87
f17f705b	88	/* Context for session open confirmation callback */
	89	struct mux_session_confirm_ctx {
	90	int want_tty;
	91	int want_subsys;
	92	int want_x_fwd;
	93	int want_agent_fwd;
	94	Buffer cmd;
	95	char *term;
	96	struct termios tio;
	97	char **env;
	98	};
	99
3bcced4c	100	/* fd to control socket */
	101	int muxserver_sock = -1;
	102
	103	/* Multiplexing control command */
	104	u_int muxclient_command = 0;
	105
	106	/* Set when signalled. */
	107	static volatile sig_atomic_t muxclient_terminate = 0;
	108
	109	/* PID of multiplex server */
	110	static u_int muxserver_pid = 0;
	111
	112
	113	/* ** Multiplexing master support */
	114
	115	/* Prepare a mux master to listen on a Unix domain socket. */
	116	void
	117	muxserver_listen(void)
	118	{
	119	struct sockaddr_un addr;
	120	mode_t old_umask;
	121	int addr_len;
	122
	123	if (options.control_path == NULL \|\|
	124	options.control_master == SSHCTL_MASTER_NO)
	125	return;
	126
	127	debug("setting up multiplex master socket");
	128
	129	memset(&addr, '\0', sizeof(addr));
	130	addr.sun_family = AF_UNIX;
	131	addr_len = offsetof(struct sockaddr_un, sun_path) +
	132	strlen(options.control_path) + 1;
	133
	134	if (strlcpy(addr.sun_path, options.control_path,
	135	sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
	136	fatal("ControlPath too long");
	137
	138	if ((muxserver_sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
	139	fatal("%s socket(): %s", __func__, strerror(errno));
	140
	141	old_umask = umask(0177);
	142	if (bind(muxserver_sock, (struct sockaddr *)&addr, addr_len) == -1) {
	143	muxserver_sock = -1;
	144	if (errno == EINVAL \|\| errno == EADDRINUSE)
	145	fatal("ControlSocket %s already exists",
	146	options.control_path);
	147	else
	148	fatal("%s bind(): %s", __func__, strerror(errno));
	149	}
	150	umask(old_umask);
	151
	152	if (listen(muxserver_sock, 64) == -1)
	153	fatal("%s listen(): %s", __func__, strerror(errno));
	154
	155	set_nonblock(muxserver_sock);
	156	}
	157
	158	/* Callback on open confirmation in mux master for a mux client session. */
	159	static void
f17f705b	160	mux_session_confirm(int id, void *arg)
3bcced4c	161	{
	162	struct mux_session_confirm_ctx *cctx = arg;
	163	const char *display;
	164	Channel *c;
	165	int i;
	166
	167	if (cctx == NULL)
	168	fatal("%s: cctx == NULL", __func__);
	169	if ((c = channel_lookup(id)) == NULL)
	170	fatal("%s: no channel for id %d", __func__, id);
	171
	172	display = getenv("DISPLAY");
	173	if (cctx->want_x_fwd && options.forward_x11 && display != NULL) {
	174	char proto, data;
	175	/* Get reasonable local authentication information. */
	176	client_x11_get_proto(display, options.xauth_location,
	177	options.forward_x11_trusted, &proto, &data);
	178	/* Request forwarding with authentication spoofing. */
	179	debug("Requesting X11 forwarding with authentication spoofing.");
	180	x11_request_forwarding_with_spoofing(id, display, proto, data);
	181	/* XXX wait for reply */
	182	}
	183
	184	if (cctx->want_agent_fwd && options.forward_agent) {
	185	debug("Requesting authentication agent forwarding.");
	186	channel_request_start(id, "auth-agent-req@openssh.com", 0);
	187	packet_send();
	188	}
	189
	190	client_session2_setup(id, cctx->want_tty, cctx->want_subsys,
	191	cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env);
	192
	193	c->open_confirm_ctx = NULL;
	194	buffer_free(&cctx->cmd);
	195	xfree(cctx->term);
	196	if (cctx->env != NULL) {
	197	for (i = 0; cctx->env[i] != NULL; i++)
	198	xfree(cctx->env[i]);
	199	xfree(cctx->env);
	200	}
	201	xfree(cctx);
	202	}
	203
	204	/*
	205	* Accept a connection on the mux master socket and process the
	206	* client's request. Returns flag indicating whether mux master should
	207	* begin graceful close.
	208	*/
	209	int
	210	muxserver_accept_control(void)
	211	{
	212	Buffer m;
	213	Channel *c;
	214	int client_fd, new_fd[3], ver, allowed, window, packetmax;
	215	socklen_t addrlen;
	216	struct sockaddr_storage addr;
	217	struct mux_session_confirm_ctx *cctx;
	218	char *cmd;
f17f705b	219	u_int i, j, len, env_len, mux_command, flags, escape_char;
3bcced4c	220	uid_t euid;
	221	gid_t egid;
	222	int start_close = 0;
	223
	224	/*
	225	* Accept connection on control socket
	226	*/
	227	memset(&addr, 0, sizeof(addr));
	228	addrlen = sizeof(addr);
	229	if ((client_fd = accept(muxserver_sock,
	230	(struct sockaddr*)&addr, &addrlen)) == -1) {
	231	error("%s accept: %s", __func__, strerror(errno));
	232	return 0;
	233	}
	234
	235	if (getpeereid(client_fd, &euid, &egid) < 0) {
	236	error("%s getpeereid failed: %s", __func__, strerror(errno));
	237	close(client_fd);
	238	return 0;
	239	}
	240	if ((euid != 0) && (getuid() != euid)) {
	241	error("control mode uid mismatch: peer euid %u != uid %u",
	242	(u_int) euid, (u_int) getuid());
	243	close(client_fd);
	244	return 0;
	245	}
	246
	247	/* XXX handle asynchronously */
	248	unset_nonblock(client_fd);
	249
	250	/* Read command */
	251	buffer_init(&m);
	252	if (ssh_msg_recv(client_fd, &m) == -1) {
	253	error("%s: client msg_recv failed", __func__);
	254	close(client_fd);
	255	buffer_free(&m);
	256	return 0;
	257	}
	258	if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
	259	error("%s: wrong client version %d", __func__, ver);
	260	buffer_free(&m);
	261	close(client_fd);
	262	return 0;
	263	}
	264
	265	allowed = 1;
	266	mux_command = buffer_get_int(&m);
	267	flags = buffer_get_int(&m);
	268
	269	buffer_clear(&m);
	270
	271	switch (mux_command) {
	272	case SSHMUX_COMMAND_OPEN:
	273	if (options.control_master == SSHCTL_MASTER_ASK \|\|
	274	options.control_master == SSHCTL_MASTER_AUTO_ASK)
	275	allowed = ask_permission("Allow shared connection "
	276	"to %s? ", host);
	277	/* continue below */
	278	break;
	279	case SSHMUX_COMMAND_TERMINATE:
	280	if (options.control_master == SSHCTL_MASTER_ASK \|\|
	281	options.control_master == SSHCTL_MASTER_AUTO_ASK)
	282	allowed = ask_permission("Terminate shared connection "
	283	"to %s? ", host);
284	if (allowed)
285	start_close = 1;
286	/* FALLTHROUGH */
287	case SSHMUX_COMMAND_ALIVE_CHECK:
288	/* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */
289	buffer_clear(&m);
290	buffer_put_int(&m, allowed);
291	buffer_put_int(&m, getpid());
292	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
293	error("%s: client msg_send failed", __func__);
294	close(client_fd);
295	buffer_free(&m);
296	return start_close;
297	}
298	buffer_free(&m);
299	close(client_fd);
300	return start_close;
301	default:
302	error("Unsupported command %d", mux_command);
303	buffer_free(&m);
304	close(client_fd);
305	return 0;
306	}
307
308	/* Reply for SSHMUX_COMMAND_OPEN */
309	buffer_clear(&m);
310	buffer_put_int(&m, allowed);
311	buffer_put_int(&m, getpid());
312	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
313	error("%s: client msg_send failed", __func__);
314	close(client_fd);
315	buffer_free(&m);
316	return 0;
317	}
318
319	if (!allowed) {
320	error("Refused control connection");
321	close(client_fd);
322	buffer_free(&m);
323	return 0;
324	}
325
326	buffer_clear(&m);
327	if (ssh_msg_recv(client_fd, &m) == -1) {
328	error("%s: client msg_recv failed", __func__);
329	close(client_fd);
330	buffer_free(&m);
331	return 0;
332	}
333	if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
334	error("%s: wrong client version %d", __func__, ver);
335	buffer_free(&m);
336	close(client_fd);
337	return 0;
338	}
339
340	cctx = xcalloc(1, sizeof(*cctx));
341	cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0;
342	cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0;
343	cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0;
344	cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0;
345	cctx->term = buffer_get_string(&m, &len);
f17f705b	346	escape_char = buffer_get_int(&m);
3bcced4c	347
	348	cmd = buffer_get_string(&m, &len);
	349	buffer_init(&cctx->cmd);
	350	buffer_append(&cctx->cmd, cmd, strlen(cmd));
	351
	352	env_len = buffer_get_int(&m);
	353	env_len = MIN(env_len, 4096);
	354	debug3("%s: receiving %d env vars", __func__, env_len);
	355	if (env_len != 0) {
	356	cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env));
	357	for (i = 0; i < env_len; i++)
	358	cctx->env[i] = buffer_get_string(&m, &len);
	359	cctx->env[i] = NULL;
	360	}
	361
	362	debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__,
	363	cctx->want_tty, cctx->want_subsys, cmd);
	364	xfree(cmd);
	365
	366	/* Gather fds from client */
	367	for(i = 0; i < 3; i++) {
	368	if ((new_fd[i] = mm_receive_fd(client_fd)) == -1) {
	369	error("%s: failed to receive fd %d from slave",
	370	__func__, i);
	371	for (j = 0; j < i; j++)
	372	close(new_fd[j]);
	373	for (j = 0; j < env_len; j++)
	374	xfree(cctx->env[j]);
	375	if (env_len > 0)
	376	xfree(cctx->env);
	377	xfree(cctx->term);
	378	buffer_free(&cctx->cmd);
	379	close(client_fd);
	380	xfree(cctx);
	381	return 0;
	382	}
	383	}
	384
	385	debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__,
	386	new_fd[0], new_fd[1], new_fd[2]);
	387
	388	/* Try to pick up ttymodes from client before it goes raw */
	389	if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1)
	390	error("%s: tcgetattr: %s", __func__, strerror(errno));
	391
	392	/* This roundtrip is just for synchronisation of ttymodes */
	393	buffer_clear(&m);
	394	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
	395	error("%s: client msg_send failed", __func__);
	396	close(client_fd);
	397	close(new_fd[0]);
	398	close(new_fd[1]);
	399	close(new_fd[2]);
	400	buffer_free(&m);
	401	xfree(cctx->term);
	402	if (env_len != 0) {
	403	for (i = 0; i < env_len; i++)
	404	xfree(cctx->env[i]);
	405	xfree(cctx->env);
	406	}
	407	return 0;
	408	}
	409	buffer_free(&m);
	410
411	/* enable nonblocking unless tty */
412	if (!isatty(new_fd[0]))
413	set_nonblock(new_fd[0]);
414	if (!isatty(new_fd[1]))
415	set_nonblock(new_fd[1]);
416	if (!isatty(new_fd[2]))
417	set_nonblock(new_fd[2]);
418
419	set_nonblock(client_fd);
420
421	window = CHAN_SES_WINDOW_DEFAULT;
422	packetmax = CHAN_SES_PACKET_DEFAULT;
423	if (cctx->want_tty) {
424	window >>= 1;
425	packetmax >>= 1;
426	}
427
428	c = channel_new("session", SSH_CHANNEL_OPENING,
429	new_fd[0], new_fd[1], new_fd[2], window, packetmax,
430	CHAN_EXTENDED_WRITE, "client-session", /nonblock/0);
431
3bcced4c	432	c->ctl_fd = client_fd;
f17f705b	433	if (cctx->want_tty && escape_char != 0xffffffff) {
	434	channel_register_filter(c->self,
	435	client_simple_escape_filter, NULL,
	436	client_new_escape_filter_ctx((int)escape_char));
	437	}
3bcced4c	438
	439	debug3("%s: channel_new: %d", __func__, c->self);
	440
	441	channel_send_open(c->self);
f17f705b	442	channel_register_open_confirm(c->self, mux_session_confirm, cctx);
3bcced4c	443	return 0;
	444	}
	445
	446	/* ** Multiplexing client support */
	447
	448	/* Exit signal handler */
	449	static void
	450	control_client_sighandler(int signo)
	451	{
	452	muxclient_terminate = signo;
	453	}
	454
	455	/*
	456	* Relay signal handler - used to pass some signals from mux client to
	457	* mux master.
	458	*/
	459	static void
	460	control_client_sigrelay(int signo)
	461	{
	462	int save_errno = errno;
	463
	464	if (muxserver_pid > 1)
	465	kill(muxserver_pid, signo);
	466
	467	errno = save_errno;
	468	}
	469
	470	/* Check mux client environment variables before passing them to mux master. */
	471	static int
	472	env_permitted(char *env)
	473	{
	474	int i, ret;
	475	char name[1024], *cp;
	476
	477	if ((cp = strchr(env, '=')) == NULL \|\| cp == env)
	478	return (0);
	479	ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
	480	if (ret <= 0 \|\| (size_t)ret >= sizeof(name))
	481	fatal("env_permitted: name '%.100s...' too long", env);
	482
	483	for (i = 0; i < options.num_send_env; i++)
	484	if (match_pattern(name, options.send_env[i]))
	485	return (1);
	486
	487	return (0);
	488	}
	489
	490	/* Multiplex client main loop. */
	491	void
	492	muxclient(const char *path)
	493	{
	494	struct sockaddr_un addr;
	495	int i, r, fd, sock, exitval[2], num_env, addr_len;
	496	Buffer m;
	497	char *term;
	498	extern char **environ;
	499	u_int flags;
	500
	501	if (muxclient_command == 0)
	502	muxclient_command = SSHMUX_COMMAND_OPEN;
	503
	504	switch (options.control_master) {
	505	case SSHCTL_MASTER_AUTO:
	506	case SSHCTL_MASTER_AUTO_ASK:
507	debug("auto-mux: Trying existing master");
508	/* FALLTHROUGH */
509	case SSHCTL_MASTER_NO:
510	break;
511	default:
512	return;
513	}
514
515	memset(&addr, '\0', sizeof(addr));
516	addr.sun_family = AF_UNIX;
517	addr_len = offsetof(struct sockaddr_un, sun_path) +
518	strlen(path) + 1;
519
520	if (strlcpy(addr.sun_path, path,
521	sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
522	fatal("ControlPath too long");
523
524	if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
525	fatal("%s socket(): %s", __func__, strerror(errno));
526
527	if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
528	if (muxclient_command != SSHMUX_COMMAND_OPEN) {
529	fatal("Control socket connect(%.100s): %s", path,
530	strerror(errno));
531	}
532	if (errno == ENOENT)
533	debug("Control socket \"%.100s\" does not exist", path);
534	else {
535	error("Control socket connect(%.100s): %s", path,
536	strerror(errno));
537	}
538	close(sock);
539	return;
540	}
541
542	if (stdin_null_flag) {
543	if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
544	fatal("open(/dev/null): %s", strerror(errno));
545	if (dup2(fd, STDIN_FILENO) == -1)
546	fatal("dup2: %s", strerror(errno));
547	if (fd > STDERR_FILENO)
548	close(fd);
549	}
550
551	term = getenv("TERM");
552
553	flags = 0;
554	if (tty_flag)
555	flags \|= SSHMUX_FLAG_TTY;
556	if (subsystem_flag)
557	flags \|= SSHMUX_FLAG_SUBSYS;
558	if (options.forward_x11)
559	flags \|= SSHMUX_FLAG_X11_FWD;
560	if (options.forward_agent)
561	flags \|= SSHMUX_FLAG_AGENT_FWD;
562
563	signal(SIGPIPE, SIG_IGN);
564
565	buffer_init(&m);
566
567	/* Send our command to server */
568	buffer_put_int(&m, muxclient_command);
569	buffer_put_int(&m, flags);
570	if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
571	fatal("%s: msg_send", __func__);
572	buffer_clear(&m);
573
574	/* Get authorisation status and PID of controlee */
575	if (ssh_msg_recv(sock, &m) == -1)
576	fatal("%s: msg_recv", __func__);
577	if (buffer_get_char(&m) != SSHMUX_VER)
578	fatal("%s: wrong version", __func__);
579	if (buffer_get_int(&m) != 1)
580	fatal("Connection to master denied");
581	muxserver_pid = buffer_get_int(&m);
582
583	buffer_clear(&m);
584
585	switch (muxclient_command) {
586	case SSHMUX_COMMAND_ALIVE_CHECK:
587	fprintf(stderr, "Master running (pid=%d)\r\n",
588	muxserver_pid);
589	exit(0);
590	case SSHMUX_COMMAND_TERMINATE:
591	fprintf(stderr, "Exit request sent.\r\n");
592	exit(0);
593	case SSHMUX_COMMAND_OPEN:
f17f705b	594	buffer_put_cstring(&m, term ? term : "");
	595	if (options.escape_char == SSH_ESCAPECHAR_NONE)
	596	buffer_put_int(&m, 0xffffffff);
	597	else
	598	buffer_put_int(&m, options.escape_char);
	599	buffer_append(&command, "\0", 1);
	600	buffer_put_cstring(&m, buffer_ptr(&command));
	601
	602	if (options.num_send_env == 0 \|\| environ == NULL) {
	603	buffer_put_int(&m, 0);
	604	} else {
	605	/* Pass environment */
	606	num_env = 0;
	607	for (i = 0; environ[i] != NULL; i++) {
	608	if (env_permitted(environ[i]))
	609	num_env++; /* Count */
	610	}
	611	buffer_put_int(&m, num_env);
	612	for (i = 0; environ[i] != NULL && num_env >= 0; i++) {
	613	if (env_permitted(environ[i])) {
	614	num_env--;
	615	buffer_put_cstring(&m, environ[i]);
	616	}
	617	}
	618	}
3bcced4c	619	break;
3bcced4c	620	default:
f17f705b	621	fatal("unrecognised muxclient_command %d", muxclient_command);
3bcced4c	622	}
	623
	624	if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
	625	fatal("%s: msg_send", __func__);
	626
	627	if (mm_send_fd(sock, STDIN_FILENO) == -1 \|\|
	628	mm_send_fd(sock, STDOUT_FILENO) == -1 \|\|
	629	mm_send_fd(sock, STDERR_FILENO) == -1)
	630	fatal("%s: send fds failed", __func__);
	631
	632	/* Wait for reply, so master has a chance to gather ttymodes */
	633	buffer_clear(&m);
	634	if (ssh_msg_recv(sock, &m) == -1)
	635	fatal("%s: msg_recv", __func__);
	636	if (buffer_get_char(&m) != SSHMUX_VER)
	637	fatal("%s: wrong version", __func__);
	638	buffer_free(&m);
	639
	640	signal(SIGHUP, control_client_sighandler);
	641	signal(SIGINT, control_client_sighandler);
	642	signal(SIGTERM, control_client_sighandler);
	643	signal(SIGWINCH, control_client_sigrelay);
	644
	645	if (tty_flag)
	646	enter_raw_mode();
	647
	648	/*
	649	* Stick around until the controlee closes the client_fd.
	650	* Before it does, it is expected to write this process' exit
	651	* value (one int). This process must read the value and wait for
	652	* the closure of the client_fd; if this one closes early, the
	653	* multiplex master will terminate early too (possibly losing data).
	654	*/
	655	exitval[0] = 0;
	656	for (i = 0; !muxclient_terminate && i < (int)sizeof(exitval);) {
	657	r = read(sock, (char *)exitval + i, sizeof(exitval) - i);
	658	if (r == 0) {
	659	debug2("Received EOF from master");
	660	break;
	661	}
	662	if (r == -1) {
	663	if (errno == EINTR)
	664	continue;
	665	fatal("%s: read %s", __func__, strerror(errno));
	666	}
	667	i += r;
	668	}
	669
	670	close(sock);
	671	leave_raw_mode();
	672	if (i > (int)sizeof(int))
	673	fatal("%s: master returned too much data (%d > %lu)",
	674	__func__, i, sizeof(int));
	675	if (muxclient_terminate) {
	676	debug2("Exiting on signal %d", muxclient_terminate);
	677	exitval[0] = 255;
	678	} else if (i < (int)sizeof(int)) {
	679	debug2("Control master terminated unexpectedly");
	680	exitval[0] = 255;
	681	} else
	682	debug2("Received exit status from master %d", exitval[0]);
	683
	684	if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
	685	fprintf(stderr, "Shared connection to %s closed.\r\n", host);
686
687	exit(exitval[0]);
688	}