[openssh.git] / mux.c

/* $OpenBSD: mux.c,v 1.3 2008/06/12 05:32:30 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.
 *   7. Support ~^Z in mux slaves.
 *   8. Inspect or control sessions in master.
 *   9. If we ever support the "signal" channel request, send signals on
 *      sessions in master.
 */

#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
aacab402	1	/* $OpenBSD: mux.c,v 1.3 2008/06/12 05:32:30 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.
aacab402	33	* 7. Support ~^Z in mux slaves.
	34	* 8. Inspect or control sessions in master.
	35	* 9. If we ever support the "signal" channel request, send signals on
	36	* sessions in master.
f17f705b	37	*/
f17f705b	38
3bcced4c	39	#include <sys/types.h>
	40	#include <sys/param.h>
	41	#include <sys/stat.h>
	42	#include <sys/socket.h>
	43	#include <sys/un.h>
	44
	45	#include <errno.h>
	46	#include <fcntl.h>
	47	#include <signal.h>
	48	#include <stdarg.h>
	49	#include <stddef.h>
	50	#include <stdlib.h>
	51	#include <stdio.h>
	52	#include <string.h>
	53	#include <unistd.h>
0894bbed	54	#ifdef HAVE_PATHS_H
3bcced4c	55	#include <paths.h>
0894bbed	56	#endif
3bcced4c	57
b3ef88dc	58	#ifdef HAVE_UTIL_H
	59	# include <util.h>
	60	#endif
	61
	62	#ifdef HAVE_LIBUTIL_H
	63	# include <libutil.h>
	64	#endif
	65
3bcced4c	66	#include "openbsd-compat/sys-queue.h"
	67	#include "xmalloc.h"
	68	#include "log.h"
	69	#include "ssh.h"
	70	#include "pathnames.h"
	71	#include "misc.h"
	72	#include "match.h"
	73	#include "buffer.h"
	74	#include "channels.h"
	75	#include "msg.h"
	76	#include "packet.h"
	77	#include "monitor_fdpass.h"
	78	#include "sshpty.h"
	79	#include "key.h"
	80	#include "readconf.h"
	81	#include "clientloop.h"
	82
	83	/* from ssh.c */
	84	extern int tty_flag;
	85	extern Options options;
	86	extern int stdin_null_flag;
	87	extern char *host;
	88	int subsystem_flag;
	89	extern Buffer command;
	90
f17f705b	91	/* Context for session open confirmation callback */
	92	struct mux_session_confirm_ctx {
	93	int want_tty;
	94	int want_subsys;
	95	int want_x_fwd;
	96	int want_agent_fwd;
	97	Buffer cmd;
	98	char *term;
	99	struct termios tio;
	100	char **env;
	101	};
	102
3bcced4c	103	/* fd to control socket */
	104	int muxserver_sock = -1;
	105
	106	/* Multiplexing control command */
	107	u_int muxclient_command = 0;
	108
	109	/* Set when signalled. */
	110	static volatile sig_atomic_t muxclient_terminate = 0;
	111
	112	/* PID of multiplex server */
	113	static u_int muxserver_pid = 0;
	114
	115
	116	/* ** Multiplexing master support */
	117
	118	/* Prepare a mux master to listen on a Unix domain socket. */
	119	void
	120	muxserver_listen(void)
	121	{
	122	struct sockaddr_un addr;
	123	mode_t old_umask;
	124	int addr_len;
	125
	126	if (options.control_path == NULL \|\|
	127	options.control_master == SSHCTL_MASTER_NO)
	128	return;
	129
	130	debug("setting up multiplex master socket");
	131
	132	memset(&addr, '\0', sizeof(addr));
	133	addr.sun_family = AF_UNIX;
	134	addr_len = offsetof(struct sockaddr_un, sun_path) +
	135	strlen(options.control_path) + 1;
	136
	137	if (strlcpy(addr.sun_path, options.control_path,
	138	sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
	139	fatal("ControlPath too long");
	140
	141	if ((muxserver_sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
	142	fatal("%s socket(): %s", __func__, strerror(errno));
	143
	144	old_umask = umask(0177);
	145	if (bind(muxserver_sock, (struct sockaddr *)&addr, addr_len) == -1) {
	146	muxserver_sock = -1;
	147	if (errno == EINVAL \|\| errno == EADDRINUSE)
	148	fatal("ControlSocket %s already exists",
	149	options.control_path);
	150	else
	151	fatal("%s bind(): %s", __func__, strerror(errno));
	152	}
	153	umask(old_umask);
	154
	155	if (listen(muxserver_sock, 64) == -1)
	156	fatal("%s listen(): %s", __func__, strerror(errno));
	157
	158	set_nonblock(muxserver_sock);
	159	}
	160
	161	/* Callback on open confirmation in mux master for a mux client session. */
	162	static void
f17f705b	163	mux_session_confirm(int id, void *arg)
3bcced4c	164	{
	165	struct mux_session_confirm_ctx *cctx = arg;
	166	const char *display;
	167	Channel *c;
	168	int i;
	169
	170	if (cctx == NULL)
	171	fatal("%s: cctx == NULL", __func__);
	172	if ((c = channel_lookup(id)) == NULL)
	173	fatal("%s: no channel for id %d", __func__, id);
	174
	175	display = getenv("DISPLAY");
	176	if (cctx->want_x_fwd && options.forward_x11 && display != NULL) {
	177	char proto, data;
	178	/* Get reasonable local authentication information. */
	179	client_x11_get_proto(display, options.xauth_location,
	180	options.forward_x11_trusted, &proto, &data);
	181	/* Request forwarding with authentication spoofing. */
	182	debug("Requesting X11 forwarding with authentication spoofing.");
	183	x11_request_forwarding_with_spoofing(id, display, proto, data);
	184	/* XXX wait for reply */
	185	}
	186
	187	if (cctx->want_agent_fwd && options.forward_agent) {
	188	debug("Requesting authentication agent forwarding.");
	189	channel_request_start(id, "auth-agent-req@openssh.com", 0);
	190	packet_send();
	191	}
	192
	193	client_session2_setup(id, cctx->want_tty, cctx->want_subsys,
	194	cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env);
	195
	196	c->open_confirm_ctx = NULL;
	197	buffer_free(&cctx->cmd);
	198	xfree(cctx->term);
	199	if (cctx->env != NULL) {
	200	for (i = 0; cctx->env[i] != NULL; i++)
	201	xfree(cctx->env[i]);
	202	xfree(cctx->env);
	203	}
	204	xfree(cctx);
	205	}
	206
	207	/*
	208	* Accept a connection on the mux master socket and process the
	209	* client's request. Returns flag indicating whether mux master should
	210	* begin graceful close.
	211	*/
	212	int
	213	muxserver_accept_control(void)
	214	{
	215	Buffer m;
	216	Channel *c;
	217	int client_fd, new_fd[3], ver, allowed, window, packetmax;
	218	socklen_t addrlen;
	219	struct sockaddr_storage addr;
	220	struct mux_session_confirm_ctx *cctx;
	221	char *cmd;
f17f705b	222	u_int i, j, len, env_len, mux_command, flags, escape_char;
3bcced4c	223	uid_t euid;
	224	gid_t egid;
	225	int start_close = 0;
	226
	227	/*
	228	* Accept connection on control socket
	229	*/
	230	memset(&addr, 0, sizeof(addr));
	231	addrlen = sizeof(addr);
	232	if ((client_fd = accept(muxserver_sock,
	233	(struct sockaddr*)&addr, &addrlen)) == -1) {
	234	error("%s accept: %s", __func__, strerror(errno));
	235	return 0;
	236	}
	237
	238	if (getpeereid(client_fd, &euid, &egid) < 0) {
	239	error("%s getpeereid failed: %s", __func__, strerror(errno));
	240	close(client_fd);
	241	return 0;
	242	}
	243	if ((euid != 0) && (getuid() != euid)) {
	244	error("control mode uid mismatch: peer euid %u != uid %u",
	245	(u_int) euid, (u_int) getuid());
	246	close(client_fd);
	247	return 0;
	248	}
	249
	250	/* XXX handle asynchronously */
	251	unset_nonblock(client_fd);
	252
	253	/* Read command */
	254	buffer_init(&m);
	255	if (ssh_msg_recv(client_fd, &m) == -1) {
	256	error("%s: client msg_recv failed", __func__);
	257	close(client_fd);
	258	buffer_free(&m);
	259	return 0;
	260	}
	261	if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
	262	error("%s: wrong client version %d", __func__, ver);
	263	buffer_free(&m);
	264	close(client_fd);
	265	return 0;
	266	}
	267
	268	allowed = 1;
	269	mux_command = buffer_get_int(&m);
	270	flags = buffer_get_int(&m);
	271
	272	buffer_clear(&m);
	273
	274	switch (mux_command) {
	275	case SSHMUX_COMMAND_OPEN:
	276	if (options.control_master == SSHCTL_MASTER_ASK \|\|
	277	options.control_master == SSHCTL_MASTER_AUTO_ASK)
	278	allowed = ask_permission("Allow shared connection "
	279	"to %s? ", host);
	280	/* continue below */
	281	break;
	282	case SSHMUX_COMMAND_TERMINATE:
	283	if (options.control_master == SSHCTL_MASTER_ASK \|\|
	284	options.control_master == SSHCTL_MASTER_AUTO_ASK)
	285	allowed = ask_permission("Terminate shared connection "
	286	"to %s? ", host);
287	if (allowed)
288	start_close = 1;
289	/* FALLTHROUGH */
290	case SSHMUX_COMMAND_ALIVE_CHECK:
291	/* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */
292	buffer_clear(&m);
293	buffer_put_int(&m, allowed);
294	buffer_put_int(&m, getpid());
295	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
296	error("%s: client msg_send failed", __func__);
297	close(client_fd);
298	buffer_free(&m);
299	return start_close;
300	}
301	buffer_free(&m);
302	close(client_fd);
303	return start_close;
304	default:
305	error("Unsupported command %d", mux_command);
306	buffer_free(&m);
307	close(client_fd);
308	return 0;
309	}
310
311	/* Reply for SSHMUX_COMMAND_OPEN */
312	buffer_clear(&m);
313	buffer_put_int(&m, allowed);
314	buffer_put_int(&m, getpid());
315	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
316	error("%s: client msg_send failed", __func__);
317	close(client_fd);
318	buffer_free(&m);
319	return 0;
320	}
321
322	if (!allowed) {
323	error("Refused control connection");
324	close(client_fd);
325	buffer_free(&m);
326	return 0;
327	}
328
329	buffer_clear(&m);
330	if (ssh_msg_recv(client_fd, &m) == -1) {
331	error("%s: client msg_recv failed", __func__);
332	close(client_fd);
333	buffer_free(&m);
334	return 0;
335	}
336	if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
337	error("%s: wrong client version %d", __func__, ver);
338	buffer_free(&m);
339	close(client_fd);
340	return 0;
341	}
342
343	cctx = xcalloc(1, sizeof(*cctx));
344	cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0;
345	cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0;
346	cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0;
347	cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0;
348	cctx->term = buffer_get_string(&m, &len);
f17f705b	349	escape_char = buffer_get_int(&m);
3bcced4c	350
	351	cmd = buffer_get_string(&m, &len);
	352	buffer_init(&cctx->cmd);
	353	buffer_append(&cctx->cmd, cmd, strlen(cmd));
	354
	355	env_len = buffer_get_int(&m);
	356	env_len = MIN(env_len, 4096);
	357	debug3("%s: receiving %d env vars", __func__, env_len);
	358	if (env_len != 0) {
	359	cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env));
	360	for (i = 0; i < env_len; i++)
	361	cctx->env[i] = buffer_get_string(&m, &len);
	362	cctx->env[i] = NULL;
	363	}
	364
	365	debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__,
	366	cctx->want_tty, cctx->want_subsys, cmd);
	367	xfree(cmd);
	368
	369	/* Gather fds from client */
	370	for(i = 0; i < 3; i++) {
	371	if ((new_fd[i] = mm_receive_fd(client_fd)) == -1) {
	372	error("%s: failed to receive fd %d from slave",
	373	__func__, i);
	374	for (j = 0; j < i; j++)
	375	close(new_fd[j]);
	376	for (j = 0; j < env_len; j++)
	377	xfree(cctx->env[j]);
	378	if (env_len > 0)
	379	xfree(cctx->env);
	380	xfree(cctx->term);
	381	buffer_free(&cctx->cmd);
	382	close(client_fd);
	383	xfree(cctx);
	384	return 0;
	385	}
	386	}
	387
	388	debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__,
	389	new_fd[0], new_fd[1], new_fd[2]);
	390
	391	/* Try to pick up ttymodes from client before it goes raw */
	392	if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1)
	393	error("%s: tcgetattr: %s", __func__, strerror(errno));
	394
	395	/* This roundtrip is just for synchronisation of ttymodes */
	396	buffer_clear(&m);
	397	if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
	398	error("%s: client msg_send failed", __func__);
	399	close(client_fd);
	400	close(new_fd[0]);
	401	close(new_fd[1]);
	402	close(new_fd[2]);
	403	buffer_free(&m);
	404	xfree(cctx->term);
	405	if (env_len != 0) {
	406	for (i = 0; i < env_len; i++)
	407	xfree(cctx->env[i]);
	408	xfree(cctx->env);
	409	}
	410	return 0;
	411	}
	412	buffer_free(&m);
	413
414	/* enable nonblocking unless tty */
415	if (!isatty(new_fd[0]))
416	set_nonblock(new_fd[0]);
417	if (!isatty(new_fd[1]))
418	set_nonblock(new_fd[1]);
419	if (!isatty(new_fd[2]))
420	set_nonblock(new_fd[2]);
421
422	set_nonblock(client_fd);
423
424	window = CHAN_SES_WINDOW_DEFAULT;
425	packetmax = CHAN_SES_PACKET_DEFAULT;
426	if (cctx->want_tty) {
427	window >>= 1;
428	packetmax >>= 1;
429	}
430
431	c = channel_new("session", SSH_CHANNEL_OPENING,
432	new_fd[0], new_fd[1], new_fd[2], window, packetmax,
433	CHAN_EXTENDED_WRITE, "client-session", /nonblock/0);
434
3bcced4c	435	c->ctl_fd = client_fd;
f17f705b	436	if (cctx->want_tty && escape_char != 0xffffffff) {
	437	channel_register_filter(c->self,
	438	client_simple_escape_filter, NULL,
	439	client_new_escape_filter_ctx((int)escape_char));
	440	}
3bcced4c	441
	442	debug3("%s: channel_new: %d", __func__, c->self);
	443
	444	channel_send_open(c->self);
f17f705b	445	channel_register_open_confirm(c->self, mux_session_confirm, cctx);
3bcced4c	446	return 0;
	447	}
	448
	449	/* ** Multiplexing client support */
	450
	451	/* Exit signal handler */
	452	static void
	453	control_client_sighandler(int signo)
	454	{
	455	muxclient_terminate = signo;
	456	}
	457
	458	/*
	459	* Relay signal handler - used to pass some signals from mux client to
	460	* mux master.
	461	*/
	462	static void
	463	control_client_sigrelay(int signo)
	464	{
	465	int save_errno = errno;
	466
	467	if (muxserver_pid > 1)
	468	kill(muxserver_pid, signo);
	469
	470	errno = save_errno;
	471	}
	472
	473	/* Check mux client environment variables before passing them to mux master. */
	474	static int
	475	env_permitted(char *env)
	476	{
	477	int i, ret;
	478	char name[1024], *cp;
	479
	480	if ((cp = strchr(env, '=')) == NULL \|\| cp == env)
	481	return (0);
	482	ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
	483	if (ret <= 0 \|\| (size_t)ret >= sizeof(name))
	484	fatal("env_permitted: name '%.100s...' too long", env);
	485
	486	for (i = 0; i < options.num_send_env; i++)
	487	if (match_pattern(name, options.send_env[i]))
	488	return (1);
	489
	490	return (0);
	491	}
	492
	493	/* Multiplex client main loop. */
	494	void
	495	muxclient(const char *path)
	496	{
	497	struct sockaddr_un addr;
	498	int i, r, fd, sock, exitval[2], num_env, addr_len;
	499	Buffer m;
	500	char *term;
	501	extern char **environ;
	502	u_int flags;
	503
	504	if (muxclient_command == 0)
	505	muxclient_command = SSHMUX_COMMAND_OPEN;
	506
	507	switch (options.control_master) {
	508	case SSHCTL_MASTER_AUTO:
	509	case SSHCTL_MASTER_AUTO_ASK:
510	debug("auto-mux: Trying existing master");
511	/* FALLTHROUGH */
512	case SSHCTL_MASTER_NO:
513	break;
514	default:
515	return;
516	}
517
518	memset(&addr, '\0', sizeof(addr));
519	addr.sun_family = AF_UNIX;
520	addr_len = offsetof(struct sockaddr_un, sun_path) +
521	strlen(path) + 1;
522
523	if (strlcpy(addr.sun_path, path,
524	sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
525	fatal("ControlPath too long");
526
527	if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
528	fatal("%s socket(): %s", __func__, strerror(errno));
529
530	if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
531	if (muxclient_command != SSHMUX_COMMAND_OPEN) {
532	fatal("Control socket connect(%.100s): %s", path,
533	strerror(errno));
534	}
535	if (errno == ENOENT)
536	debug("Control socket \"%.100s\" does not exist", path);
537	else {
538	error("Control socket connect(%.100s): %s", path,
539	strerror(errno));
540	}
541	close(sock);
542	return;
543	}
544
545	if (stdin_null_flag) {
546	if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
547	fatal("open(/dev/null): %s", strerror(errno));
548	if (dup2(fd, STDIN_FILENO) == -1)
549	fatal("dup2: %s", strerror(errno));
550	if (fd > STDERR_FILENO)
551	close(fd);
552	}
553
554	term = getenv("TERM");
555
556	flags = 0;
557	if (tty_flag)
558	flags \|= SSHMUX_FLAG_TTY;
559	if (subsystem_flag)
560	flags \|= SSHMUX_FLAG_SUBSYS;
561	if (options.forward_x11)
562	flags \|= SSHMUX_FLAG_X11_FWD;
563	if (options.forward_agent)
564	flags \|= SSHMUX_FLAG_AGENT_FWD;
565
566	signal(SIGPIPE, SIG_IGN);
567
568	buffer_init(&m);
569
570	/* Send our command to server */
571	buffer_put_int(&m, muxclient_command);
572	buffer_put_int(&m, flags);
573	if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
574	fatal("%s: msg_send", __func__);
575	buffer_clear(&m);
576
577	/* Get authorisation status and PID of controlee */
578	if (ssh_msg_recv(sock, &m) == -1)
579	fatal("%s: msg_recv", __func__);
580	if (buffer_get_char(&m) != SSHMUX_VER)
581	fatal("%s: wrong version", __func__);
582	if (buffer_get_int(&m) != 1)
583	fatal("Connection to master denied");
584	muxserver_pid = buffer_get_int(&m);
585
586	buffer_clear(&m);
587
588	switch (muxclient_command) {
589	case SSHMUX_COMMAND_ALIVE_CHECK:
590	fprintf(stderr, "Master running (pid=%d)\r\n",
591	muxserver_pid);
592	exit(0);
593	case SSHMUX_COMMAND_TERMINATE:
594	fprintf(stderr, "Exit request sent.\r\n");
595	exit(0);
596	case SSHMUX_COMMAND_OPEN:
f17f705b	597	buffer_put_cstring(&m, term ? term : "");
	598	if (options.escape_char == SSH_ESCAPECHAR_NONE)
	599	buffer_put_int(&m, 0xffffffff);
	600	else
	601	buffer_put_int(&m, options.escape_char);
	602	buffer_append(&command, "\0", 1);
	603	buffer_put_cstring(&m, buffer_ptr(&command));
	604
	605	if (options.num_send_env == 0 \|\| environ == NULL) {
	606	buffer_put_int(&m, 0);
	607	} else {
	608	/* Pass environment */
	609	num_env = 0;
	610	for (i = 0; environ[i] != NULL; i++) {
	611	if (env_permitted(environ[i]))
	612	num_env++; /* Count */
	613	}
	614	buffer_put_int(&m, num_env);
	615	for (i = 0; environ[i] != NULL && num_env >= 0; i++) {
	616	if (env_permitted(environ[i])) {
	617	num_env--;
	618	buffer_put_cstring(&m, environ[i]);
	619	}
	620	}
	621	}
3bcced4c	622	break;
3bcced4c	623	default:
f17f705b	624	fatal("unrecognised muxclient_command %d", muxclient_command);
3bcced4c	625	}
	626
	627	if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
	628	fatal("%s: msg_send", __func__);
	629
	630	if (mm_send_fd(sock, STDIN_FILENO) == -1 \|\|
	631	mm_send_fd(sock, STDOUT_FILENO) == -1 \|\|
	632	mm_send_fd(sock, STDERR_FILENO) == -1)
	633	fatal("%s: send fds failed", __func__);
	634
	635	/* Wait for reply, so master has a chance to gather ttymodes */
	636	buffer_clear(&m);
	637	if (ssh_msg_recv(sock, &m) == -1)
	638	fatal("%s: msg_recv", __func__);
	639	if (buffer_get_char(&m) != SSHMUX_VER)
	640	fatal("%s: wrong version", __func__);
	641	buffer_free(&m);
	642
	643	signal(SIGHUP, control_client_sighandler);
	644	signal(SIGINT, control_client_sighandler);
	645	signal(SIGTERM, control_client_sighandler);
	646	signal(SIGWINCH, control_client_sigrelay);
	647
	648	if (tty_flag)
	649	enter_raw_mode();
	650
	651	/*
	652	* Stick around until the controlee closes the client_fd.
	653	* Before it does, it is expected to write this process' exit
	654	* value (one int). This process must read the value and wait for
	655	* the closure of the client_fd; if this one closes early, the
	656	* multiplex master will terminate early too (possibly losing data).
	657	*/
	658	exitval[0] = 0;
	659	for (i = 0; !muxclient_terminate && i < (int)sizeof(exitval);) {
	660	r = read(sock, (char *)exitval + i, sizeof(exitval) - i);
	661	if (r == 0) {
	662	debug2("Received EOF from master");
	663	break;
	664	}
	665	if (r == -1) {
	666	if (errno == EINTR)
	667	continue;
	668	fatal("%s: read %s", __func__, strerror(errno));
	669	}
	670	i += r;
	671	}
	672
	673	close(sock);
	674	leave_raw_mode();
	675	if (i > (int)sizeof(int))
	676	fatal("%s: master returned too much data (%d > %lu)",
	677	__func__, i, sizeof(int));
	678	if (muxclient_terminate) {
	679	debug2("Exiting on signal %d", muxclient_terminate);
	680	exitval[0] = 255;
	681	} else if (i < (int)sizeof(int)) {
	682	debug2("Control master terminated unexpectedly");
	683	exitval[0] = 255;
	684	} else
	685	debug2("Received exit status from master %d", exitval[0]);
	686
	687	if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
	688	fprintf(stderr, "Shared connection to %s closed.\r\n", host);
689
690	exit(exitval[0]);
691	}