- djm@cvs.openbsd.org 2008/05/09 14:18:44

     [clientloop.c clientloop.h ssh.c mux.c]
     tidy up session multiplexing code, moving it into its own file and
     making the function names more consistent - making ssh.c and
     clientloop.c a fair bit more readable.
     ok markus@

1 files changed, 646 insertions, 0 deletions

diff --git a/mux.c b/mux.c
new file mode 100644
index 000000000..78ba63153
--- /dev/null
+++ b/mux.c
@@ -0,0 +1,646 @@
+/* $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 <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>
+#include <util.h>
+#include <paths.h>
+
+#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]);
+}