x11vnc -users, fix -solid on gnome/kde, configure.ac pwd.h wait.h and utmpx.h

6 files changed, 959 insertions, 158 deletions

diff --git a/x11vnc/ChangeLog b/x11vnc/ChangeLog
index 799ca9e..cc93296 100644
--- a/x11vnc/ChangeLog
+++ b/x11vnc/ChangeLog
@@ -1,3 +1,8 @@
+2005-02-09  Karl Runge <runge@karlrunge.com>
+	* Add -users switch user mechanism and related utilities.
+	* fix -solid for gnome and kde.
+	* exit earlier on trapped XIO errors.
+
 2005-02-05  Karl Runge <runge@karlrunge.com>
 	* -solid solid color background when clients are connected. 
 	* -opts/-? to show option names only.
diff --git a/x11vnc/README b/x11vnc/README
index 3126bec..392af22 100644
--- a/x11vnc/README
+++ b/x11vnc/README
@@ -1,5 +1,5 @@
 
-x11vnc README file                         Date: Sat Feb  5 12:56:36 EST 2005
+x11vnc README file                         Date: Wed Feb  9 00:21:28 EST 2005
 
 The following information is taken from these URLs:
 
@@ -354,16 +354,34 @@ vncviewer -via $host localhost:0      # must be TightVNC vncviewer.
    TightVNC encoding gives very good compression and performance, it even
    makes a noticeable difference over a fast LAN)
 
+   Shortcut: On Solaris 10 you can pick up everything just by insuring
+   that your PATH has /usr/sfw/bin (for gcc) and /usr/ccs/bin (for other
+   build tools), e.g.:
+
+  env PATH=/usr/sfw/bin:/usr/ccs/bin:$PATH sh -c './configure; make'
+
    libjpeg is included in Solaris 9 and later (/usr/sfw/include and
    /usr/sfw/lib), and zlib in Solaris 8 and later (/usr/include and
-   /usr/lib). To get the source for these libraries: libjpeg is available
-   at [36]ftp://ftp.uu.net/graphics/jpeg/ and zlib at
+   /usr/lib).
+
+   So on Solaris 9 you can pick up everything with something like this:
+  env PATH=/usr/local/bin:/usr/ccs/bin:$PATH CPPFLAGS='-I /usr/sfw/include' LDF
+LAGS='-L/usr/sfw/lib -R/usr/sfw/lib' sh -c './configure; make'
+
+   assuming your gcc is in /usr/local/bin. That is getting pretty long,
+   see those assignments split up in the build script below.
+
+   If your system does not have these libraries you can get the source
+   for these libraries to build them: libjpeg is available at
+   [36]ftp://ftp.uu.net/graphics/jpeg/ and zlib at
    [37]http://www.gzip.org/zlib/. See also
    [38]http://www.sunfreeware.com/ for Solaris binary packages of these
-   libraries.
+   libraries as well as for gcc. Normally they will install into
+   /usr/local.
 
    Here is a build script that indicates one way to pass the library
-   locations information to the libvncserver configuration:
+   locations information to the libvncserver configuration via the
+   CPPFLAGS and LDFLAGS environmental variables:
 #!/bin/sh
 
 # Build script for Solaris, etc, with gcc, libjpeg and libz in
@@ -511,11 +529,12 @@ ls -l ./x11vnc/x11vnc
 
    SunRay Gotcha #1:   Note that even though your SunRay X11 DISPLAY is
    something like :137, x11vnc still tries for port 5900 as its listening
-   if it can get it, in which case the VNC display (i.e. the information
-   you supply to the VNC viewer) is something like sunray-server:0
-   (note the :0 corresponding to port 5900, it is not :137). If it cannot
-   get 5900, it tries for 5901, and so on. You can also try to force the
-   port (and thereby the VNC display) using the -rfbport NNNN option.
+   port if it can get it, in which case the VNC display (i.e. the
+   information you supply to the VNC viewer) is something like
+   sunray-server:0   (note the :0 corresponding to port 5900, it is not
+   :137). If it cannot get 5900, it tries for 5901, and so on. You can
+   also try to force the port (and thereby the VNC display) using the
+   -rfbport NNNN option.
 
     Limitations:
 
@@ -530,8 +549,8 @@ ls -l ./x11vnc/x11vnc
      * A rate limiting factor for x11vnc performance is that video
        hardware is optimized for writing, not reading (x11vnc reads the
        video framebuffer for the screen image data). The difference can
-       be a factor of 10-50, and it usually takes about 0.5-1 sec to read
-       in the whole video hardware framebuffer (5MB for 1280x1024 at
+       be a factor of 10-200, and it usually takes about 0.5-1 sec to
+       read in the whole video hardware framebuffer (5MB for 1280x1024 at
        depth 24). So whenever activity changes most of the screen there
        is a delay of 0.5-1 sec while x11vnc reads the changed regions in.
        To get a sense of the read and write speeds of your video card,
@@ -540,7 +559,7 @@ ls -l ./x11vnc/x11vnc
        direct graphics access the dga command (press "b" to run the
        benchmark and then after a few seconds press "q" to quit).
        On XFree86 it is actually possible to increase the framebuffer
-       read speed considerably (5-50 times) by using the Shadow
+       read speed considerably (5-100 times) by using the Shadow
        Framebuffer (a copy of the framebuffer is kept in main memory and
        this can be read much more quickly). To do this one puts the line
        Option "ShadowFB" "true" (and depending on video card driver,
diff --git a/x11vnc/tkx11vnc b/x11vnc/tkx11vnc
index 3e8f491..875ddd2 100755
--- a/x11vnc/tkx11vnc
+++ b/x11vnc/tkx11vnc
@@ -1660,6 +1660,7 @@ proc split_query {query} {
 proc set_x11_display {name} {
 	global x11_display
 	set x11_display "x11vnc X display: $name"
+	wm title . "tkx11vnc - $name"
 }
 proc set_vnc_display {name} {
 	global vnc_display
@@ -1671,6 +1672,7 @@ proc set_vnc_url {name} {
 }
 proc no_x11_display {} {
 	set_x11_display "(*none*)"
+	wm title . "tkx11vnc"
 }
 proc no_vnc_display {} {
 	set_vnc_display "(*none*)"
@@ -2391,6 +2393,7 @@ proc start_x11vnc {} {
 
 proc run_remote_cmd {opts} {
 	global menu_var x11vnc_prog x11vnc_cmdline x11vnc_xdisplay
+	global x11vnc_auth_file
 
 	set debug [in_debug_mode]
 
@@ -2413,6 +2416,10 @@ proc run_remote_cmd {opts} {
 		lappend cmd "-display"
 		lappend cmd $x11vnc_xdisplay
 	}
+	if {$x11vnc_auth_file != ""} {
+		lappend cmd "-auth"
+		lappend cmd $x11vnc_auth_file
+	}
 	lappend cmd "-sync"
 	foreach word $opts {
 		lappend cmd $word
@@ -2501,6 +2508,7 @@ proc try_connect {} {
 # main:
 
 global env x11vnc_prog x11vnc_cmdline x11vnc_xdisplay x11vnc_connect;
+global x11vnc_auth_file
 global helpall helptext helpremote helplabel hostname;
 global all_settings reply_xdisplay always_update
 global max_text_height max_text_width
@@ -2585,6 +2593,13 @@ if {[info exists env(X11VNC_XDISPLAY)]} {
 	set x11vnc_xdisplay ":0";
 }
 
+if {[info exists env(X11VNC_AUTH_FILE)]} {
+	set x11vnc_auth_file $env(X11VNC_AUTH_FILE)
+} else {
+	set x11vnc_auth_file ""
+}
+
+
 set hostname [exec uname -n]
 #puts [exec env]
 #puts "x11vnc_xdisplay: $x11vnc_xdisplay"
diff --git a/x11vnc/tkx11vnc.h b/x11vnc/tkx11vnc.h
index 32ccbc2..cc60b8b 100644
--- a/x11vnc/tkx11vnc.h
+++ b/x11vnc/tkx11vnc.h
@@ -1666,6 +1666,7 @@
 "proc set_x11_display {name} {\n"
 "	global x11_display\n"
 "	set x11_display \"x11vnc X display: $name\"\n"
+"	wm title . \"tkx11vnc - $name\"\n"
 "}\n"
 "proc set_vnc_display {name} {\n"
 "	global vnc_display\n"
@@ -1677,6 +1678,7 @@
 "}\n"
 "proc no_x11_display {} {\n"
 "	set_x11_display \"(*none*)\"\n"
+"	wm title . \"tkx11vnc\"\n"
 "}\n"
 "proc no_vnc_display {} {\n"
 "	set_vnc_display \"(*none*)\"\n"
@@ -2397,6 +2399,7 @@
 "\n"
 "proc run_remote_cmd {opts} {\n"
 "	global menu_var x11vnc_prog x11vnc_cmdline x11vnc_xdisplay\n"
+"	global x11vnc_auth_file\n"
 "\n"
 "	set debug [in_debug_mode]\n"
 "\n"
@@ -2419,6 +2422,10 @@
 "		lappend cmd \"-display\"\n"
 "		lappend cmd $x11vnc_xdisplay\n"
 "	}\n"
+"	if {$x11vnc_auth_file != \"\"} {\n"
+"		lappend cmd \"-auth\"\n"
+"		lappend cmd $x11vnc_auth_file\n"
+"	}\n"
 "	lappend cmd \"-sync\"\n"
 "	foreach word $opts {\n"
 "		lappend cmd $word\n"
@@ -2507,6 +2514,7 @@
 "# main:\n"
 "\n"
 "global env x11vnc_prog x11vnc_cmdline x11vnc_xdisplay x11vnc_connect;\n"
+"global x11vnc_auth_file\n"
 "global helpall helptext helpremote helplabel hostname;\n"
 "global all_settings reply_xdisplay always_update\n"
 "global max_text_height max_text_width\n"
@@ -2591,6 +2599,13 @@
 "	set x11vnc_xdisplay \":0\";\n"
 "}\n"
 "\n"
+"if {[info exists env(X11VNC_AUTH_FILE)]} {\n"
+"	set x11vnc_auth_file $env(X11VNC_AUTH_FILE)\n"
+"} else {\n"
+"	set x11vnc_auth_file \"\"\n"
+"}\n"
+"\n"
+"\n"
 "set hostname [exec uname -n]\n"
 "#puts [exec env]\n"
 "#puts \"x11vnc_xdisplay: $x11vnc_xdisplay\"\n"
diff --git a/x11vnc/x11vnc.1 b/x11vnc/x11vnc.1
index a95106a..66bb57d 100644
--- a/x11vnc/x11vnc.1
+++ b/x11vnc/x11vnc.1
@@ -2,7 +2,7 @@
 .TH X11VNC "1" "February 2005" "x11vnc " "User Commands"
 .SH NAME
 x11vnc - allow VNC connections to real X11 displays
-         version: 0.7.1pre, lastmod: 2005-02-05
+         version: 0.7.1pre, lastmod: 2005-02-08
 .SH SYNOPSIS
 .B x11vnc
 [OPTION]...
@@ -58,11 +58,11 @@ environment variable to \fIdisp\fR.
 .IP
 Set the X authority file to be \fIfile\fR, equivalent to
 setting the XAUTHORITY environment variable to \fIfile\fR
-before startup.  See 
+before startup.  Same as \fB-xauth\fR file.  See 
 .IR Xsecurity (7)
-, 
+,
 .IR xauth (1)
-man pages.
+man pages for more info.
 .PP
 \fB-id\fR \fIwindowid\fR
 .IP
@@ -210,10 +210,17 @@ Note: if you are not redirecting stderr to a log file
 For use with "vncviewer -listen" reverse connections.
 If \fIstring\fR has the form "host" or "host:port"
 the connection is made once at startup.  Use commas
-for a list of host's and host:port's.  If \fIstring\fR
-contains "/" it is instead interpreted as a file to
-periodically check for new hosts.  The first line is
-read and then the file is truncated.
+for a list of host's and host:port's.
+.IP
+If \fIstring\fR contains "/" it is instead interpreted
+as a file to periodically check for new hosts.
+The first line is read and then the file is truncated.
+Be careful for this usage mode if x11vnc is running as
+root (e.g. via 
+.IR inetd (1)
+or 
+.IR gdm (1)
+).
 .PP
 \fB-vncconnect,\fR \fB-novncconnect\fR
 .IP
@@ -277,6 +284,17 @@ external command returns 0 the client is accepted,
 otherwise the client is rejected.  See below for an
 extension to accept a client view-only.
 .IP
+If x11vnc is running as root (say from 
+.IR inetd (1)
+or from
+display managers 
+.IR xdm (1)
+, 
+.IR gdm (1)
+, etc), think about the
+security implications carefully before supplying this
+option (likewise for the \fB-gone\fR option).
+.IP
 Environment: The RFB_CLIENT_IP environment variable will
 be set to the incoming client IP number and the port
 in RFB_CLIENT_PORT (or -1 if unavailable).  Similarly,
@@ -332,6 +350,61 @@ set to "gone" and the other RFB_* variables are as
 in \fB-accept.\fR  Unlike \fB-accept,\fR the command return code
 is not interpreted by x11vnc.  Example: \fB-gone\fR 'xlock &'
 .PP
+\fB-users\fR \fIlist\fR
+.IP
+If x11vnc is started as root (say from 
+.IR inetd (1)
+or
+from display managers 
+.IR xdm (1)
+, 
+.IR gdm (1)
+, etc), then as
+soon as possible after connections to the display are
+established try to switch to one of the users in the
+comma separated \fIlist\fR.  If x11vnc is not running as
+root this option is ignored.
+.IP
+Why use this option?  In general it is not needed
+since x11vnc is already connected to the display and
+can perform its primary functions.  It was added to
+make some of the *external* utility commands x11vnc
+occasionally runs work properly.  In particular under
+GNOME and KDE to implement the "\fB-solid\fR \fIcolor\fR" feature
+external commands (gconftool-2 and dcop) must be run as
+the user owning the desktop session.  This option also
+affects the userid used to run the processes for the
+\fB-accept\fR and \fB-gone\fR options.  It also affects the ability
+to read files for options such as \fB-connect,\fR \fB-allow,\fR and
+\fB-remap.\fR Note that the \fB-connect\fR file is also written to.
+.IP
+So be careful with this option since in many situations
+its use can decrease security.
+.IP
+The switch to a user will only take place if the display
+can still be opened as that user (this is primarily to
+try to guess the actual owner of the session). Example:
+"\fB-users\fR \fIfred,wilma,betty\fR".  Note that a malicious
+user "barney" by quickly using "xhost +" when
+logging in can get x11vnc to switch to user "fred".
+What happens next?
+.IP
+Under display managers it may be a long time before
+the switch succeeds (i.e. a user logs in).  To make
+it switch immediately regardless if the display can
+be reopened or not prefix the username with the +
+character. E.g. "\fB-users\fR \fI+bob\fR" or "\fB-users\fR \fI+nobody\fR".
+The latter is probably the only use of this option
+that increases security.  To switch to a user *before*
+connections to the display are made or any files opened
+use the "=" character: "\fB-users\fR \fI=username\fR".
+.IP
+The special user "guess" means to examine the utmpx
+database looking for a user attached to the display
+number and try him/her.  To limit the list of guesses,
+use: "\fB-users\fR \fIguess=bob,fred\fR".  Be especially careful
+using this mode.
+.PP
 \fB-noshm\fR
 .IP
 Do not use the MIT-SHM extension for the polling.
@@ -357,15 +430,22 @@ To improve performance, when VNC clients are connected
 try to change the desktop background to a solid color.
 The [color] is optional: the default color is "cyan4".
 For a different one specify the X color (rgb.txt name,
-e.g. "darkblue" or numerical "#RRGGBB"). Currently
-this option only works on GNOME, KDE, and classic X
-(i.e. with the background image on the root window).
-The "gconftool-2" and "dcop" external commands are
-run for GNOME and KDE respectively.  Other desktops
-won't work, e.g. XFCE (send us the corresponding
-commands if you find them).  If x11vnc guesses your
-desktop incorrectly, you can force it by prefixing
-color with "gnome:", "kde:", or "root:".
+e.g. "darkblue" or numerical "#RRGGBB").
+.IP
+Currently this option only works on GNOME, KDE, and
+classic X (i.e. with the background image on the root
+window).  The "gconftool-2" and "dcop" external
+commands are run for GNOME and KDE respectively.
+Other desktops won't work, e.g. XFCE (send us the
+corresponding commands if you find them).  If x11vnc
+is running as root (
+.IR inetd (1)
+or 
+.IR gdm (1)
+), the \fB-users\fR
+option may be needed for GNOME and KDE.  If x11vnc
+guesses your desktop incorrectly, you can force it by
+prefixing color with "gnome:", "kde:", or "root:".
 .PP
 \fB-blackout\fR \fIstring\fR
 .IP
@@ -930,8 +1010,7 @@ the gui to come back to you via your ssh redirected X
 display (e.g. localhost:10).
 .IP
 Examples: "x11vnc \fB-gui",\fR "x11vnc \fB-gui\fR localhost:10",
-"x11vnc \fB-gui\fR :10", "x11vnc \fB-gui\fR wait,:10",
-"x11vnc \fB-gui\fR <x11vnc-opts...>"
+"x11vnc \fB-gui\fR :10", "x11vnc \fB-gui\fR conn,host:10",
 .IP
 If you do not specify a gui X display in "gui-opts"
 then the DISPLAY environment variable and \fB-display\fR
@@ -1361,7 +1440,7 @@ noalwaysshared nevershared noalwaysshared dontdisconnect
 nodontdisconnect desktop noremote
 .IP
 aro=  display vncdisplay desktopname http_url auth
-rootshift scale_str scaled_x scaled_y scale_numer
+users rootshift scale_str scaled_x scaled_y scale_numer
 scale_denom scale_fac scaling_noblend scaling_nomult4
 scaling_pad scaling_interpolate inetd safer unsafe
 passwdfile using_shm logfile o rc norc h help V version
diff --git a/x11vnc/x11vnc.c b/x11vnc/x11vnc.c
index fbf896a..af15260 100644
--- a/x11vnc/x11vnc.c
+++ b/x11vnc/x11vnc.c
@@ -137,11 +137,17 @@
 
 #define LIBVNCSERVER_HAVE_XSHM 1
 #define LIBVNCSERVER_HAVE_XTEST 1
+
+#define LIBVNCSERVER_HAVE_PWD_H 1
+#define LIBVNCSERVER_HAVE_SYS_WAIT_H 1
+#define LIBVNCSERVER_HAVE_UTMPX_H 1
+
 /*
 #define LIBVNCSERVER_HAVE_LIBXINERAMA 1
 #define LIBVNCSERVER_HAVE_XFIXES 1
 #define LIBVNCSERVER_HAVE_XDAMAGE 1
  */
+
 #endif	/* OLD_TREE */
 
 #include <unistd.h>
@@ -215,6 +221,17 @@ extern int h_errno;
 #include <arpa/inet.h>
 #endif
 
+/* XXX autoconf */
+#if LIBVNCSERVER_HAVE_PWD_H
+#include <pwd.h>
+#endif
+#if LIBVNCSERVER_HAVE_SYS_WAIT_H
+#include <sys/wait.h>
+#endif
+#if LIBVNCSERVER_HAVE_UTMPX_H
+#include <utmpx.h>
+#endif
+
 /*
  * overlay/multi-depth screen reading support
  * undef SOLARIS_OVERLAY or IRIX_OVERLAY if there are problems building.
@@ -273,7 +290,7 @@ static int xdamage_base_event_type;
 #endif
 
 /*               date +'lastmod: %Y-%m-%d' */
-char lastmod[] = "0.7.1pre lastmod: 2005-02-05";
+char lastmod[] = "0.7.1pre lastmod: 2005-02-08";
 
 /* X display info */
 
@@ -371,6 +388,10 @@ time_t last_event, last_input, last_client = 0;
 /* last client to move pointer */
 rfbClientPtr last_pointer_client = NULL;
 
+int accepted_client = 0;
+int client_count = 0;
+int clients_served = 0;
+
 /* more transient kludge variables: */
 int cursor_x, cursor_y;		/* x and y from the viewer(s) */
 int got_user_input = 0;
@@ -433,6 +454,7 @@ void initialize_polling_images(void);
 void initialize_signals(void);
 void initialize_tiles(void);
 void initialize_speeds(void);
+void clean_shm(int);
 void free_tiles(void);
 void initialize_watch_bell(void);
 void initialize_xinerama(void);
@@ -545,6 +567,8 @@ int shared = 0;			/* share vnc display. */
 int deny_all = 0;		/* global locking of new clients */
 int accept_remote_cmds = 1;	/* -noremote */
 int safe_remote_only = 0;	/* -safer, -unsafe */
+int started_as_root = 0;
+char *users_list = NULL;	/* -users */
 char *allow_list = NULL;	/* for -allow and -localhost */
 char *allow_once = NULL;	/* one time -allow */
 char *accept_cmd = NULL;	/* for -accept */
@@ -752,6 +776,17 @@ void lowercase(char *str) {
 	}
 }
 
+char *lblanks(char *str) {
+	char *p = str;
+	while (*p) {
+		if (! isspace(*p)) {
+			break;
+		}
+		p++;
+	}
+	return p;
+}
+
 int scan_hexdec(char *str, unsigned long *num) {
 	if (sscanf(str, "0x%lx", num) != 1) {
 		if (sscanf(str, "%ld", num) != 1) {
@@ -852,6 +887,424 @@ char *bitprint(unsigned int st, int nbits) {
 	return str;	/* take care to use or copy immediately */
 }
 
+char *get_user_name(void) {
+	char *user = NULL;
+
+	user = getenv("USER");
+	if (user == NULL) {
+		user = getenv("LOGNAME");
+	}
+
+#if LIBVNCSERVER_HAVE_PWD_H
+	if (user == NULL) {
+		struct passwd *pw = getpwuid(getuid());
+		if (pw) {
+			user = pw->pw_name;
+		}
+	}
+#endif
+
+	if (user) {
+		return(strdup(user));
+	} else {
+		return(strdup("unknown-user"));
+	}
+}
+
+char *get_home_dir(void) {
+	char *home = NULL;
+
+	home = getenv("HOME");
+
+#if LIBVNCSERVER_HAVE_PWD_H
+	if (home == NULL) {
+		struct passwd *pw = getpwuid(getuid());
+		if (pw) {
+			home = pw->pw_dir;
+		}
+	}
+#endif
+
+	if (home) {
+		return(strdup(home));
+	} else {
+		return(strdup("/"));
+	}
+}
+
+char *get_shell(void) {
+	char *shell = NULL;
+
+	shell = getenv("SHELL");
+
+#if LIBVNCSERVER_HAVE_PWD_H
+	if (shell == NULL) {
+		struct passwd *pw = getpwuid(getuid());
+		if (pw) {
+			shell = pw->pw_shell;
+		}
+	}
+#endif
+
+	if (shell) {
+		return(strdup(shell));
+	} else {
+		return(strdup("/bin/sh"));
+	}
+}
+
+int switch_user(char *);
+void try_to_switch_users(void);
+char *guess_desktop(void);
+
+void switch_user_dummy(void) {
+	;	/* dummy does nothing */
+}
+void switch_user_solid_bg(void) {
+	/* we have switched users, some things to do. */
+	if (use_solid_bg && client_count) {
+		solid_bg(0);
+	}
+}
+
+void check_switched_user (void) {
+	static time_t sched_switched_user = 0;
+	static int did_solid = 0;
+	static int did_dummy = 0;
+	int delay = 15;
+	time_t now = time(0);
+
+	if (started_as_root == 1 && users_list) {
+		try_to_switch_users();
+		if (started_as_root == 2) {
+			/*
+			 * schedule the switch_user_tasks() call
+			 * 15 secs is for piggy desktops to start up.
+			 * might not be enough for slow machines...
+			 */
+			sched_switched_user = now;
+			did_dummy = 0;
+			did_solid = 0;
+			/* add other activities */
+		}
+	}
+	if (! sched_switched_user) {
+		return;
+	}
+
+	if (! did_dummy) {
+		switch_user_dummy();
+		did_dummy = 1;
+	}
+	if (! did_solid) {
+		int doit = 0;
+		char *ss = solid_str;
+		if (now >= sched_switched_user + delay) {
+			doit = 1;
+		} else if (ss && strstr(ss, "root:") == ss) {
+		    	if (now >= sched_switched_user + 3) {
+				doit = 1;
+			}
+		} else if (strcmp("root", guess_desktop())) {
+			usleep(1000 * 1000);
+			doit = 1;
+		}
+		if (doit) {
+			switch_user_solid_bg();
+			did_solid = 1;
+		}
+	}
+
+	if (did_dummy && did_solid) {
+		sched_switched_user = 0;
+	}
+}
+
+int guess_user_and_switch(char *str) {
+#if LIBVNCSERVER_HAVE_UTMPX_H
+	char *q, *dstr, *d = DisplayString(dpy);
+	char *allowed = NULL;
+	int i, ret = 0, max = 300;
+
+	if (strstr(str, "guess=") == str) {
+		char *allowed = strchr(str, '=');
+		allowed++;
+	}
+
+	/* pick out ":N" */
+	dstr = strchr(d, ':');
+	if (! dstr) {
+		return 0;
+	}
+	q = strchr(dstr, '.');
+	if (q) {
+		*q = '\0';
+	}
+
+	/* look over the utmpx entries looking for this display */
+	setutxent();
+	for (i=0; i<max; i++) {
+		char *str;
+		struct utmpx *utx = getutxent();
+
+		if (! utx) {
+			break;
+		}
+
+		str = lblanks(utx->ut_user);
+		if (*str == '\0') {
+			continue;	/* blank user */
+		}
+		if (allowed) {
+			char *p, *t = strdup(allowed);	
+			int ok = 0;
+			p = strtok(t, ",");
+			while (p) {
+				if (!strcmp(p, utx->ut_user)) {
+					ok = 1;
+				}
+				p = strtok(NULL, ",");
+			}
+			free(t);
+			if (! ok) {
+				continue;
+			}
+		}
+		if (!strcmp(utx->ut_user, "guess")) {
+			continue;	/* never... */
+		}
+
+		/* try the line for leading :N */
+		str = lblanks(utx->ut_line);
+		if (strstr(str, dstr) == str) {
+			int n = strlen(dstr);
+			if (isdigit(*(str+n))) {
+				continue;	/* :1 vs. :10 */
+			} else if (switch_user(utx->ut_user)) {
+				rfbLog("switched to guessed user: %s\n",
+				    utx->ut_user);
+				ret = 1;
+				break;
+			} else {
+				continue;
+			}
+		}
+
+		/* try the host for leading :N */
+		str = lblanks(utx->ut_host);
+		if (strstr(str, dstr) == str) {
+			int n = strlen(dstr);
+			if (isdigit(*(str+n))) {
+				continue;	/* :1 vs. :10 */
+			} else if (switch_user(utx->ut_user)) {
+				rfbLog("switched to guessed user: %s\n",
+				    utx->ut_user);
+				ret = 1;
+				break;
+			} else {
+				continue;
+			}
+		}
+	}
+	endutxent();
+
+	return ret;
+#else
+	return 0;
+#endif
+}
+
+int switch_user(char *user) {
+	int force = 0, numerical = 1;
+	uid_t uid = 0;
+	char *q, *name, *home;
+
+	if (*user == '+') {
+		force = 1;
+		user++;
+	}
+
+	if (!strcmp(user, "guess") || strstr(user, "guess=") == user) {
+		return guess_user_and_switch(user);
+	}
+
+	q = user;
+	while (*q) {
+		if (! isdigit(*q)) {
+			numerical = 0;
+			break;
+		}
+		q++;
+	}
+
+#if LIBVNCSERVER_HAVE_PWD_H
+	if (numerical) {
+		int u = atoi(user);
+		struct passwd *pw;
+
+		if (u > 0) {
+			uid = (uid_t) u;
+		} else {
+			return 0;
+		}
+		pw = getpwuid(uid);
+		if (pw) {
+			name = pw->pw_name;
+			home = pw->pw_dir;
+		} else {
+			return 0;
+		}
+	} else {
+		struct passwd *pw = getpwnam(user);
+		if (pw) {
+			uid = pw->pw_uid;
+			name = pw->pw_name;
+			home = pw->pw_dir;
+		} else {
+			return 0;
+		}
+	}
+#else
+	return 0;
+#endif
+	if (! uid) {
+		return 0;
+	}
+
+	if (! force) {
+#if LIBVNCSERVER_HAVE_FORK && LIBVNCSERVER_HAVE_SYS_WAIT_H
+		pid_t pid, pidw;
+		int st;
+		
+		/* 
+		 * We fork here and try to open the display again as the
+		 * new user.  Unreadable XAUTHORITY could be a problem...
+		 * This is not really needed since we have DISPLAY open
+		 * but: 1) is a good indicator this user owns the session
+		 * and  2) some activities do spawn new X apps, e.g.
+		 * xmessage(1), etc.
+		 */
+		if ((pid = fork()) > 0) {
+			;
+		} else if (pid == -1) {
+			fprintf(stderr, "could not fork\n");
+			rfbLogPerror("fork");
+			return 0;
+		} else {
+			Display *dpy2 = 0;
+			char *xauth = getenv("XAUTHORITY");
+#if LIBVNCSERVER_HAVE_SETUID
+			if (setuid(uid) != 0) {
+				exit(1);	/* fail */
+			}
+#else
+			exit(1);
+#endif
+			if (xauth && access(xauth, R_OK) != 0) {
+				*(xauth-2) = '_';	/* yow */
+			}
+			set_env("USER", name);
+			set_env("LOGNAME", name);
+			set_env("HOME", home);
+			fclose(stderr);
+			dpy2 = XOpenDisplay(DisplayString(dpy));
+			if (dpy2) {
+				XCloseDisplay(dpy2);
+				exit(0);	/* success */
+			} else {
+				exit(2);	/* fail */
+			}
+		}
+
+		/* see what the child says: */
+		pidw = waitpid(pid, &st, 0);
+		if (pidw == pid && WIFEXITED(st) && WEXITSTATUS(st) == 0) {
+			force = 1;
+		}
+#else
+		force = 1;
+#endif
+	}
+
+	if (force) {
+		char *xauth = getenv("XAUTHORITY");
+
+		/*
+		 * OK tricky here, we need to free the shm... otherwise
+		 * we won't be able to delete it as the other user...
+		 */
+#if !LIBVNCSERVER_HAVE_SETUID
+		return 0;
+#else
+		if (using_shm) {
+			clean_shm(0);
+			free_tiles();
+		}
+		if (setuid(uid) != 0) {
+			if (using_shm) {
+				/* 2 means we did clean_shm and free_tiles */
+				do_new_fb(2);
+			}
+			return 0;
+		}
+#endif
+		if (using_shm) {
+			do_new_fb(2);
+		}
+
+		if (xauth && access(xauth, R_OK) != 0) {
+			*(xauth-2) = '_';	/* yow */
+		}
+		set_env("USER", name);
+		set_env("LOGNAME", name);
+		set_env("HOME", home);
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+void try_to_switch_users(void) {
+	static time_t last_try = 0;
+	time_t now = time(0);
+	char *users, *p;
+
+	if (getuid() && geteuid()) {
+		rfbLog("try_to_switch_users: not root\n");
+		started_as_root = 2;
+		return;
+	}
+	if (!last_try) {
+		last_try = now;
+	} else if (now <= last_try + 2) {
+		/* try every 3 secs or so */
+		return;
+	}
+	last_try = now;
+
+	users = strdup(users_list);
+
+	if (strstr(users, "guess=") == users) {
+		if (switch_user(users)) {
+			started_as_root = 2;
+			rfbLog("try_to_switch_users: now %s\n", p);
+		}
+		free(users);
+		return;
+	}
+
+	p = strtok(users, ",");
+	while (p) {
+		if (switch_user(p)) {
+			started_as_root = 2;
+			rfbLog("try_to_switch_users: now %s\n", p);
+			break;
+		}
+		p = strtok(NULL, ",");
+	}
+	free(users);
+}
+
 /*
  * Simple utility to map host name to dotted IP address.  Ignores aliases.
  * Up to caller to free returned string.
@@ -1318,7 +1771,7 @@ void clean_shm(int quick) {
 			break;
 		}
 	}
-	if (!quiet && !quick) {
+	if (!quiet) {
 		rfbLog("deleted %d tile_row polling images.\n", cnt);
 	}
 }
@@ -1356,62 +1809,13 @@ void clean_up_exit (int ret) {
 	exit(ret);
 }
 
-/*
- * General problem handler
- */
-static void interrupted (int sig) {
-	exit_sig = sig;
-	if (exit_flag) {
-		exit_flag++;
-		if (use_threads) {
-			usleep2(250 * 1000);
-		} else if (exit_flag <= 2) {
-			return;
-		}
-		exit(4);
-	}
-	exit_flag++;
-	if (sig == 0) {
-		fprintf(stderr, "caught X11 error:\n");
-	} else {
-		fprintf(stderr, "caught signal: %d\n", sig);
-	}
-	if (sig == SIGINT) {
-		shut_down = 1;
-		return;
-	}
-
-	X_UNLOCK;
-
-	/* remove the shm areas with quick=1: */
-	clean_shm(1);
-
-	/* X keyboard cleanups */
-	delete_added_keycodes();
-
-	if (clear_mods == 1) {
-		clear_modifiers(0);
-	} else if (clear_mods == 2) {
-		clear_keys();
-	}
-	if (no_autorepeat) {
-		autorepeat(1);
-	}
-	if (use_solid_bg) {
-		solid_bg(1);
-	}
-
-	if (sig) {
-		exit(2);
-	}
-}
-
 /* X11 error handlers */
 
 static XErrorHandler   Xerror_def;
 static XIOErrorHandler XIOerr_def;
 XErrorEvent *trapped_xerror_event;
 int trapped_xerror = 0;
+int trapped_xioerror = 0;
 int trapped_getimage_xerror = 0;
 
 int trap_xerror(Display *d, XErrorEvent *error) {
@@ -1420,12 +1824,19 @@ int trap_xerror(Display *d, XErrorEvent *error) {
 	return 0;
 }
 
+int trap_xioerror(Display *d) {
+	trapped_xioerror = 1;
+	return 0;
+}
+
 int trap_getimage_xerror(Display *d, XErrorEvent *error) {
 	trapped_getimage_xerror = 1;
 	trapped_xerror_event = error;
 	return 0;
 }
 
+void interrupted(int);
+
 static int Xerror(Display *d, XErrorEvent *error) {
 	X_UNLOCK;
 	interrupted(0);
@@ -1434,7 +1845,7 @@ static int Xerror(Display *d, XErrorEvent *error) {
 
 static int XIOerr(Display *d) {
 	X_UNLOCK;
-	interrupted(0);
+	interrupted(-1);
 	return (*XIOerr_def)(d);
 }
 
@@ -1473,6 +1884,63 @@ char *xerror_string(XErrorEvent *error) {
 	}
 }
 
+/*
+ * General problem handler
+ */
+void interrupted (int sig) {
+	exit_sig = sig;
+	if (exit_flag) {
+		exit_flag++;
+		if (use_threads) {
+			usleep2(250 * 1000);
+		} else if (exit_flag <= 2) {
+			return;
+		}
+		exit(4);
+	}
+	exit_flag++;
+	if (sig == 0) {
+		fprintf(stderr, "caught X11 error:\n");
+	} else if (sig == -1) {
+		fprintf(stderr, "caught XIO error:\n");
+	} else {
+		fprintf(stderr, "caught signal: %d\n", sig);
+	}
+	if (sig == SIGINT) {
+		shut_down = 1;
+		return;
+	}
+
+	X_UNLOCK;
+
+	/* remove the shm areas with quick=1: */
+	clean_shm(1);
+
+	if (sig == -1) {
+		/* not worth trying any more cleanup, X server probably gone */
+		exit(3);
+	}
+
+	/* X keyboard cleanups */
+	delete_added_keycodes();
+
+	if (clear_mods == 1) {
+		clear_modifiers(0);
+	} else if (clear_mods == 2) {
+		clear_keys();
+	}
+	if (no_autorepeat) {
+		autorepeat(1);
+	}
+	if (use_solid_bg) {
+		solid_bg(1);
+	}
+
+	if (sig) {
+		exit(2);
+	}
+}
+
 /* trapping utility to check for a valid window: */
 int valid_window(Window win) {
 	XErrorHandler old_handler;
@@ -1563,10 +2031,6 @@ void initialize_signals(void) {
  * routines for handling incoming, outgoing, etc connections
  */
 
-static int accepted_client = 0;
-static int client_count = 0;
-static int clients_served = 0;
-
 /*
  * check that all clients are in RFB_NORMAL state
  */
@@ -3189,16 +3653,9 @@ void initialize_remap(char *infile) {
 		rewind(in);
 	}
 	while (fgets(line, 256, in) != NULL) {
-		int blank = 1, isbtn = 0;
-		p = line;
-		while (*p) {
-			if (! isspace(*p)) {
-				blank = 0;
-				break;
-			}
-			p++;
-		}
-		if (blank) {
+		int isbtn = 0;
+		p = lblanks(line);
+		if (*p == '\0') {
 			continue;
 		}
 		if (strchr(line, '#')) {
@@ -7987,6 +8444,8 @@ char *process_remote_cmd(char *cmd, int stringonly) {
 			}
 		} else if (!strcmp(p, "auth")) {
 			snprintf(buf, bufn, "aro=%s:%s", p, NONUL(auth_file));
+		} else if (!strcmp(p, "users")) {
+			snprintf(buf, bufn, "aro=%s:%s", p, NONUL(users_list));
 		} else if (!strcmp(p, "rootshift")) {
 			snprintf(buf, bufn, "aro=%s:%d", p, rootshift);
 		} else if (!strcmp(p, "scale_str")) {
@@ -9156,6 +9615,10 @@ int get_which_cursor(void) {
 					which = CURS_TERM;
 				} else if (strstr(winfo.res_class, "text")) {
 					which = CURS_TERM;
+				} else if (strstr(winfo.res_name, "onsole")) {
+					which = CURS_TERM;
+				} else if (strstr(winfo.res_class, "onsole")) {
+					which = CURS_TERM;
 				}
 			}
 		}
@@ -9796,7 +10259,8 @@ void do_new_fb(int reset_mem) {
 		rfbLog(" not work, do not use -threads if problems arise.\n");
 	}
 
-	if (reset_mem) {
+	if (reset_mem == 1) {
+		/* reset_mem == 2 is a hack for changing users... */
 		clean_shm(0);
 		free_tiles();
 	}
@@ -10655,13 +11119,45 @@ void initialize_screen(int *argc, char **argv, XImage *fb) {
 
 /* -- solid.c -- */
 
-int do_cmd(char *cmd) {
+void usr_bin_path(int restore) {
+	static char *oldpath = NULL;
+	char *newpath;
+	char addpath[] = "/usr/bin:/bin:";
+
+	if (restore) {
+		if (oldpath) {
+			set_env("PATH", oldpath);
+			free(oldpath);
+			oldpath = NULL;
+		}
+		return;
+	}
+
+	if (getenv("PATH")) {
+		oldpath = strdup(getenv("PATH"));
+	} else {
+		oldpath = strdup("/usr/bin");
+	}
+	newpath = (char *) malloc(strlen(oldpath) + strlen(addpath) + 1);
+	newpath[0] = '\0';
+	strcat(newpath, addpath);
+	strcat(newpath, oldpath);
+	set_env("PATH", newpath);
+	free(newpath);
+}
+
+int dt_cmd(char *cmd) {
 	int rc;
+
 	if (!cmd || *cmd == '\0') {
 		return 0;
 	}
+
 	rfbLog("running command:\n  %s\n", cmd);
+	usr_bin_path(0);
 	rc = system(cmd);
+	usr_bin_path(1);
+
 	if (rc >= 256) {
 		rc = rc/256;
 	}
@@ -10674,8 +11170,14 @@ char *cmd_output(char *cmd) {
 	char line[1024];
 	int rc;
 
+	if (!cmd || *cmd == '\0') {
+		return "";
+	}
+
 	rfbLog("running pipe:\n  %s\n", cmd);
+	usr_bin_path(0);
 	p = popen(cmd, "r");
+	usr_bin_path(1);
 
 	output[0] = '\0';
 
@@ -10826,12 +11328,12 @@ void solid_gnome(char *color) {
 		cmd = (char *)malloc(strlen(set_option) - 2 +
 		    strlen(orig_option) + 1);
 		sprintf(cmd, set_option, orig_option);
-		do_cmd(cmd);
+		dt_cmd(cmd);
 		free(cmd);
 		cmd = (char *)malloc(strlen(set_color) - 2 +
 		    strlen(orig_color) + 1);
 		sprintf(cmd, set_color, orig_color);
-		do_cmd(cmd);
+		dt_cmd(cmd);
 		free(cmd);
 		return;
 	}
@@ -10860,24 +11362,42 @@ void solid_gnome(char *color) {
 		rfbLog("bad color: %s\n", color);
 		return;
 	}
-	cmd = (char *)malloc(strlen(set_color) - 2 + strlen(color) + 1);
+	cmd = (char *)malloc(strlen(set_color) + strlen(color) + 1);
 	sprintf(cmd, set_color, color);
-	do_cmd(cmd);
+	dt_cmd(cmd);
 	free(cmd);
-	cmd = (char *)malloc(strlen(set_option) - 2 + strlen("none") + 1);
+
+	cmd = (char *)malloc(strlen(set_option) + strlen("none") + 1);
 	sprintf(cmd, set_option, "none");
-	do_cmd(cmd);
+	dt_cmd(cmd);
 	free(cmd);
 }
 
 void solid_kde(char *color) {
-	char set_color[] = "dcop kdesktop KBackgroundIface setColor '%s' 1";
-	char bg_off[] = "dcop kdesktop KBackgroundIface setBackgroundEnabled 0";
-	char bg_on[]  = "dcop kdesktop KBackgroundIface setBackgroundEnabled 1";
-	char *cmd;
+	char set_color[] =
+	    "dcop --user '%s' kdesktop KBackgroundIface setColor '%s' 1";
+	char bg_off[] =
+	    "dcop --user '%s' kdesktop KBackgroundIface setBackgroundEnabled 0";
+	char bg_on[] =
+	    "dcop --user '%s' kdesktop KBackgroundIface setBackgroundEnabled 1";
+	char *cmd, *user = NULL;
+	int len;
+
+	user = get_user_name();
+	if (strstr(user, "'") != NULL)  {
+		rfbLog("bad user: %s\n", user);
+		free(user);
+		return;
+	}
 
 	if (! color) {
-		do_cmd(bg_on);
+		len = strlen(bg_on) + strlen(user) + 1;
+		cmd = (char *)malloc(len);
+		sprintf(cmd, bg_on, user);
+		dt_cmd(cmd);
+		free(cmd);
+		free(user);
+
 		return;
 	}
 
@@ -10886,11 +11406,18 @@ void solid_kde(char *color) {
 		return;
 	}
 
-	cmd = (char *)malloc(strlen(set_color) - 2 + strlen(color) + 1);
-	sprintf(cmd, set_color, color);
-	do_cmd(cmd);
-	do_cmd(bg_off);
+	len = strlen(set_color) + strlen(user) + strlen(color) + 1;
+	cmd = (char *)malloc(len);
+	sprintf(cmd, set_color, user, color);
+	dt_cmd(cmd);
 	free(cmd);
+
+	len = strlen(bg_off) + strlen(user) + 1;
+	cmd = (char *)malloc(len);
+	sprintf(cmd, bg_off, user);
+	dt_cmd(cmd);
+	free(cmd);
+	free(user);
 }
 
 char *guess_desktop() {
@@ -10912,6 +11439,11 @@ void solid_bg(int restore) {
 	static char *prev_str;
 	char *dtname, *color;
 
+	if (started_as_root == 1 && users_list) {
+		/* we are still root, don't try. */
+		return;
+	}
+
 	if (restore) {
 		if (! solid_on) {
 			return;
@@ -11644,6 +12176,7 @@ void shm_clean(XShmSegmentInfo *shm, XImage *xim) {
 #endif
 	if (xim != NULL) {
 		XDestroyImage(xim);
+		xim = NULL;
 	}
 	X_UNLOCK;
 
@@ -13669,6 +14202,7 @@ void run_gui(char *gui_xdisplay, int connect_to_x11vnc, pid_t parent) {
 	    ":/usr/X11R6/bin:/usr/openwin/bin:/usr/dt/bin";
 	char cmd[100];
 	char *wish = NULL, *orig_path, *full_path, *tpath, *p;
+	char *old_xauth = NULL;
 	int try_max = 4, sleep = 300;
 	pid_t mypid = getpid();
 	FILE *pipe, *tmpf;
@@ -13687,7 +14221,14 @@ void run_gui(char *gui_xdisplay, int connect_to_x11vnc, pid_t parent) {
 		int rc, i;
 		rfbLogEnable(0);
 		if (! client_connect_file) {
+			if (getenv("XAUTHORITY") != NULL) {
+				old_xauth = strdup(getenv("XAUTHORITY"));
+			}
 			dpy = XOpenDisplay(x11vnc_xdisplay); 
+			if (! dpy && auth_file) {
+				set_env("XAUTHORITY", auth_file);
+				dpy = XOpenDisplay(x11vnc_xdisplay);
+			}
 			if (! dpy && ! x11vnc_xdisplay) {
 				x11vnc_xdisplay = strdup(":0");
 				dpy = XOpenDisplay(x11vnc_xdisplay); 
@@ -13719,6 +14260,9 @@ void run_gui(char *gui_xdisplay, int connect_to_x11vnc, pid_t parent) {
 			}
 		}
 		set_env("X11VNC_XDISPLAY", x11vnc_xdisplay);
+		if (getenv("XAUTHORITY") != NULL) {
+			set_env("X11VNC_XAUTHORITY", getenv("XAUTHORITY"));
+		}
 		if (rc == 0) {
 			fprintf(stderr, "gui: ping succeeded.\n");
 			set_env("X11VNC_CONNECT", "1");
@@ -13726,6 +14270,13 @@ void run_gui(char *gui_xdisplay, int connect_to_x11vnc, pid_t parent) {
 			fprintf(stderr, "gui: could not connect to: '%s', try"
 			    " again manually.\n", x11vnc_xdisplay);
 		}
+		if (dpy)  {
+			XCloseDisplay(dpy);
+		}
+		if (old_xauth) {
+			set_env("XAUTHORITY", old_xauth);
+			free(old_xauth);
+		}
 	}
 
 	orig_path = getenv("PATH");
@@ -13768,6 +14319,9 @@ void run_gui(char *gui_xdisplay, int connect_to_x11vnc, pid_t parent) {
 	set_env("DISPLAY", gui_xdisplay);
 	set_env("X11VNC_PROG", program_name);
 	set_env("X11VNC_CMDLINE", program_cmdline);
+	if (auth_file) {
+		set_env("X11VNC_AUTH_FILE", auth_file);
+	}
 
 	sprintf(cmd, "%s -", wish);
 	tmpf = tmpfile();
@@ -13871,6 +14425,7 @@ void do_gui(char *opts) {
 	if (! test_dpy) {
 		fprintf(stderr, "error: cannot connect to gui X DISPLAY: %s\n",
 		    gui_xdisplay);
+		exit(1);
 	}
 	XCloseDisplay(test_dpy);
 
@@ -14776,11 +15331,15 @@ static void watch_loop(void) {
 		check_xevents();
 		check_connect_inputs();		
 		check_padded_fb();		
+		if (started_as_root) {
+			check_switched_user();
+		}
 
 		if (first_conn_timeout < 0) {
 			start = time(0);
 			first_conn_timeout = -first_conn_timeout;
 		}
+
 		if (! screen || ! screen->clientHead) {
 			/* waiting for a client */
 			if (first_conn_timeout) {
@@ -14788,13 +15347,15 @@ static void watch_loop(void) {
 					rfbLog("No client after %d secs.\n",
 					    first_conn_timeout);
 					shut_down = 1;
-					continue;
 				}
 			}
 			usleep(200 * 1000);
 			continue;
 		}
-		first_conn_timeout = 0;
+
+		if (first_conn_timeout && all_clients_initialized()) {
+			first_conn_timeout = 0;
+		}
 
 		if (nofb) {
 			/* no framebuffer polling needed */
@@ -14897,7 +15458,8 @@ static void print_help(int mode) {
 "                       environment variable to \"disp\".\n"
 "-auth file             Set the X authority file to be \"file\", equivalent to\n"
 "                       setting the XAUTHORITY environment variable to \"file\"\n"
-"                       before startup.  See Xsecurity(7), xauth(1) man pages.\n"
+"                       before startup.  Same as -xauth file.  See Xsecurity(7),\n"
+"                       xauth(1) man pages for more info.\n"
 "\n"
 "-id windowid           Show the window corresponding to \"windowid\" not\n"
 "                       the entire display.  New windows like popup menus,\n"
@@ -14994,10 +15556,13 @@ static void print_help(int mode) {
 "-connect string        For use with \"vncviewer -listen\" reverse connections.\n"
 "                       If \"string\" has the form \"host\" or \"host:port\"\n"
 "                       the connection is made once at startup.  Use commas\n"
-"                       for a list of host's and host:port's.  If \"string\"\n"
-"                       contains \"/\" it is instead interpreted as a file to\n"
-"                       periodically check for new hosts.  The first line is\n"
-"                       read and then the file is truncated.\n"
+"                       for a list of host's and host:port's.\n"
+"\n"
+"                       If \"string\" contains \"/\" it is instead interpreted\n"
+"                       as a file to periodically check for new hosts.\n"
+"                       The first line is read and then the file is truncated.\n"
+"                       Be careful for this usage mode if x11vnc is running as\n"
+"                       root (e.g. via inetd(1) or gdm(1)).\n"
 "-vncconnect            Monitor the VNC_CONNECT X property set by the standard\n"
 "-novncconnect          VNC program vncconnect(1).  When the property is\n"
 "                       set to \"host\" or \"host:port\" establish a reverse\n"
@@ -15035,6 +15600,11 @@ static void print_help(int mode) {
 "                       otherwise the client is rejected.  See below for an\n"
 "                       extension to accept a client view-only.\n"
 "\n"
+"                       If x11vnc is running as root (say from inetd(1) or from\n"
+"                       display managers xdm(1), gdm(1), etc), think about the\n"
+"                       security implications carefully before supplying this\n"
+"                       option (likewise for the -gone option).\n"
+"\n"
 "                       Environment: The RFB_CLIENT_IP environment variable will\n"
 "                       be set to the incoming client IP number and the port\n"
 "                       in RFB_CLIENT_PORT (or -1 if unavailable).  Similarly,\n"
@@ -15086,6 +15656,53 @@ static void print_help(int mode) {
 "                       in -accept.  Unlike -accept, the command return code\n"
 "                       is not interpreted by x11vnc.  Example: -gone 'xlock &'\n"
 "\n"
+"-users list            If x11vnc is started as root (say from inetd(1) or\n"
+"                       from display managers xdm(1), gdm(1), etc), then as\n"
+"                       soon as possible after connections to the display are\n"
+"                       established try to switch to one of the users in the\n"
+"                       comma separated \"list\".  If x11vnc is not running as\n"
+"                       root this option is ignored.\n"
+"                       \n"
+"                       Why use this option?  In general it is not needed\n"
+"                       since x11vnc is already connected to the display and\n"
+"                       can perform its primary functions.  It was added to\n"
+"                       make some of the *external* utility commands x11vnc\n"
+"                       occasionally runs work properly.  In particular under\n"
+"                       GNOME and KDE to implement the \"-solid color\" feature\n"
+"                       external commands (gconftool-2 and dcop) must be run as\n"
+"                       the user owning the desktop session.  This option also\n"
+"                       affects the userid used to run the processes for the\n"
+"                       -accept and -gone options.  It also affects the ability\n"
+"                       to read files for options such as -connect, -allow, and\n"
+"                       -remap. Note that the -connect file is also written to.\n"
+"                       \n"
+"                       So be careful with this option since in many situations\n"
+"                       its use can decrease security.\n"
+"                       \n"
+"                       The switch to a user will only take place if the display\n"
+"                       can still be opened as that user (this is primarily to\n"
+"                       try to guess the actual owner of the session). Example:\n"
+"                       \"-users fred,wilma,betty\".  Note that a malicious\n"
+"                       user \"barney\" by quickly using \"xhost +\" when\n"
+"                       logging in can get x11vnc to switch to user \"fred\".\n"
+"                       What happens next?\n"
+"                       \n"
+"                       Under display managers it may be a long time before\n"
+"                       the switch succeeds (i.e. a user logs in).  To make\n"
+"                       it switch immediately regardless if the display can\n"
+"                       be reopened or not prefix the username with the +\n"
+"                       character. E.g. \"-users +bob\" or \"-users +nobody\".\n"
+"                       The latter is probably the only use of this option\n"
+"                       that increases security.  To switch to a user *before*\n"
+"                       connections to the display are made or any files opened\n"
+"                       use the \"=\" character: \"-users =username\".\n"
+"                       \n"
+"                       The special user \"guess\" means to examine the utmpx\n"
+"                       database looking for a user attached to the display\n"
+"                       number and try him/her.  To limit the list of guesses,\n"
+"                       use: \"-users guess=bob,fred\".  Be especially careful\n"
+"                       using this mode.\n"
+"                       \n"
 "-noshm                 Do not use the MIT-SHM extension for the polling.\n"
 "                       Remote displays can be polled this way: be careful this\n"
 "                       can use large amounts of network bandwidth.  This is\n"
@@ -15101,15 +15718,18 @@ static void print_help(int mode) {
 "                       try to change the desktop background to a solid color.\n"
 "                       The [color] is optional: the default color is \"cyan4\".\n"
 "                       For a different one specify the X color (rgb.txt name,\n"
-"                       e.g. \"darkblue\" or numerical \"#RRGGBB\"). Currently\n"
-"                       this option only works on GNOME, KDE, and classic X\n"
-"                       (i.e. with the background image on the root window).\n"
-"                       The \"gconftool-2\" and \"dcop\" external commands are\n"
-"                       run for GNOME and KDE respectively.  Other desktops\n"
-"                       won't work, e.g. XFCE (send us the corresponding\n"
-"                       commands if you find them).  If x11vnc guesses your\n"
-"                       desktop incorrectly, you can force it by prefixing\n"
-"                       color with \"gnome:\", \"kde:\", or \"root:\".\n"
+"                       e.g. \"darkblue\" or numerical \"#RRGGBB\").\n"
+"\n"
+"                       Currently this option only works on GNOME, KDE, and\n"
+"                       classic X (i.e. with the background image on the root\n"
+"                       window).  The \"gconftool-2\" and \"dcop\" external\n"
+"                       commands are run for GNOME and KDE respectively.\n"
+"                       Other desktops won't work, e.g. XFCE (send us the\n"
+"                       corresponding commands if you find them).  If x11vnc\n"
+"                       is running as root (inetd(1) or gdm(1)), the -users\n"
+"                       option may be needed for GNOME and KDE.  If x11vnc\n"
+"                       guesses your desktop incorrectly, you can force it by\n"
+"                       prefixing color with \"gnome:\", \"kde:\", or \"root:\".\n"
 "-blackout string       Black out rectangles on the screen. \"string\" is a\n"
 "                       comma separated list of WxH+X+Y type geometries for\n"
 "                       each rectangle.\n"
@@ -15535,8 +16155,7 @@ static void print_help(int mode) {
 "                       display (e.g. localhost:10).\n"
 "\n"
 "                       Examples: \"x11vnc -gui\", \"x11vnc -gui localhost:10\",\n"
-"                       \"x11vnc -gui :10\", \"x11vnc -gui wait,:10\",\n"
-"                       \"x11vnc -gui <x11vnc-opts...>\"\n"
+"                       \"x11vnc -gui :10\", \"x11vnc -gui conn,host:10\",\n"
 "\n"
 "                       If you do not specify a gui X display in \"gui-opts\"\n"
 "                       then the DISPLAY environment variable and -display\n"
@@ -15591,6 +16210,7 @@ static void print_help(int mode) {
 "                                       \"zero:x1,y1,x2,y2\" for a rectangle.\n"
 "                       refresh         send the entire fb to all clients.\n"
 "                       reset           recreate the fb, polling memory, etc.\n"
+/* ext. cmd. */
 "                       id:windowid     set -id window to \"windowid\". empty\n"
 "                                       or \"root\" to go back to root window\n"
 "                       sid:windowid    set -sid window to \"windowid\"\n"
@@ -15606,6 +16226,7 @@ static void print_help(int mode) {
 "                       visual:vis      set -visual to \"vis\"\n"
 "                       scale:frac      set -scale to \"frac\"\n"
 "                       viewonly        enable  -viewonly mode.\n"
+/* access view,share,forever */
 "                       noviewonly      disable -viewonly mode.\n"
 "                       shared          enable  -shared mode.\n"
 "                       noshared        disable -shared mode.\n"
@@ -15616,6 +16237,7 @@ static void print_help(int mode) {
 "                                       connects in the next n secs.\n"
 "                       deny            deny any new connections, same as \"lock\"\n"
 "                       nodeny          allow new connections, same as \"unlock\"\n"
+/* access, filename */
 "                       connect:host    do reverse connection to host, \"host\"\n"
 "                                       may be a comma separated list of hosts\n"
 "                                       or host:ports.  See -connect.\n"
@@ -15625,8 +16247,10 @@ static void print_help(int mode) {
 "                                       If you know the client internal hex ID,\n"
 "                                       e.g. 0x3 (returned by -query clients and\n"
 "                                       RFB_CLIENT_ID), you can use that too.\n"
+/* access */
 "                       allowonce:host  For the next connection only, allow\n"
 "                                       connection from \"host\".\n"
+/* access */
 "                       allow:hostlist  set -allow list to (comma separated)\n"
 "                                       \"hostlist\". See -allow and -localhost.\n"
 "                                       Do not use with -allow /path/to/file\n"
@@ -15634,6 +16258,7 @@ static void print_help(int mode) {
 "                                       use \"-host\" to delete a single host\n"
 "                       localhost       enable  -localhost mode\n"
 "                       nolocalhost     disable -localhost mode\n"
+/* ext. cmd. */
 "                       accept:cmd      set -accept \"cmd\" (empty to disable).\n"
 "                       gone:cmd        set -gone \"cmd\" (empty to disable).\n"
 "                       noshm           enable  -noshm mode.\n"
@@ -15644,6 +16269,7 @@ static void print_help(int mode) {
 "                       onetile         enable  -onetile mode. (you may need to\n"
 "                                       set shm for this to do something)\n"
 "                       noonetile       disable -onetile mode.\n"
+/* ext. cmd. */
 "                       solid           enable  -solid mode\n"
 "                       nosolid         disable -solid mode.\n"
 "                       solid_color:color set -solid color (and apply it).\n"
@@ -15674,6 +16300,7 @@ static void print_help(int mode) {
 "                       noclear_mods    disable -clear_mods mode.\n"
 "                       clear_keys      enable  -clear_keys mode and clear them.\n"
 "                       noclear_keys    disable -clear_keys mode.\n"
+/* filename */
 "                       remap:str       set -remap \"str\" (empty to disable).\n"
 "                                       See -remap for the form of \"str\"\n"
 "                                       (basically: key1-key2,key3-key4,...)\n"
@@ -15733,6 +16360,7 @@ static void print_help(int mode) {
 "                                       height parameter to n.\n"
 "                       desktop:str     set -desktop name to str for new clients.\n"
 "                       rfbport:n       set -rfbport to n.\n"
+/* access */
 "                       http            enable  http client connections.\n"
 "                       nohttp          disable http client connections.\n"
 "                       httpport:n      set -httpport to n.\n"
@@ -15817,7 +16445,7 @@ static void print_help(int mode) {
 "                       nodontdisconnect desktop noremote\n"
 "\n"
 "                       aro=  display vncdisplay desktopname http_url auth\n"
-"                       rootshift scale_str scaled_x scaled_y scale_numer\n"
+"                       users rootshift scale_str scaled_x scaled_y scale_numer\n"
 "                       scale_denom scale_fac scaling_noblend scaling_nomult4\n"
 "                       scaling_pad scaling_interpolate inetd safer unsafe\n"
 "                       passwdfile using_shm logfile o rc norc h help V version\n"
@@ -16097,17 +16725,22 @@ static void check_rcfile(int argc, char **argv) {
 			perror("fopen");
 			exit(1);
 		}
-	} else if (getenv("HOME") == NULL) {
-		norc = 1;
 	} else {
-		strncpy(rcfile, getenv("HOME"), 500);
-		strcat(rcfile, "/.x11vncrc");
-		infile = rcfile;
-		rc = fopen(rcfile, "r");
-		if (rc == NULL) {
+		char *home = get_home_dir();
+		if (! home) {
 			norc = 1;
 		} else {
-			rc_rcfile = strdup(rcfile);
+			strncpy(rcfile, home, 500);
+			free(home);
+
+			strcat(rcfile, "/.x11vncrc");
+			infile = rcfile;
+			rc = fopen(rcfile, "r");
+			if (rc == NULL) {
+				norc = 1;
+			} else {
+				rc_rcfile = strdup(rcfile);
+			}
 		}
 	}
 
@@ -16161,12 +16794,7 @@ static void check_rcfile(int argc, char **argv) {
 			if ( (q = strchr(p, '#')) != NULL) {
 				*q = '\0';
 			}
-			while (*p) {
-				if (! isspace(*p)) {
-					break;
-				}
-				p++;
-			}
+			p = lblanks(p);
 
 			strncat(buf, p, sz - strlen(buf) - 1);
 			if (cont) {
@@ -16195,12 +16823,7 @@ static void check_rcfile(int argc, char **argv) {
 			
 			p = buf;
 			p += strlen(parm);
-			while (*p) {
-				if (! isspace(*p)) {
-					break;
-				}
-				p++;
-			}
+			p = lblanks(p);
 			if (*p == '\0') {
 				buf[0] = '\0';
 				continue;
@@ -16258,6 +16881,45 @@ int main(int argc, char* argv[]) {
 	/* if we are root limit some remote commands: */
 	if (!getuid() || !geteuid()) {
 		safe_remote_only = 1;
+		started_as_root = 1;
+
+		/* check for '-users =fred' */
+		for (i=1; i < argc; i++) {
+			char *u;
+			int saved;
+
+			if (strcmp(argv[i], "-users")) {
+				continue;
+			}
+			if (i == argc - 1) {
+				fprintf(stderr, "not enough arguments for: "
+				    "-users\n");
+				exit(1);
+			}
+			if (*(argv[i+1]) != '=') {
+				break;
+			}
+			u = strdup(argv[i+1]);
+			*u = '+';
+			if (strstr(u, "+guess") == u) {
+				fprintf(stderr, "invalid user: %s\n", u);
+				exit(1);
+			}
+			/* kludge... */
+			saved = using_shm;
+			using_shm = 0;
+			if (!switch_user(u)) {
+				fprintf(stderr, "Could not switch to user: "
+				    "%s\n", u+1);
+				exit(1);
+			} else {
+				fprintf(stderr, "Switched to user: %s\n", u+1);
+				started_as_root = 2;
+			}
+			using_shm = saved;
+			free(u);
+			break;
+		}
 	}
 
 	argv_vnc[0] = strdup(argv[0]);
@@ -16305,7 +16967,7 @@ int main(int argc, char* argv[]) {
 		if (!strcmp(arg, "-display")) {
 			CHECK_ARGC
 			use_dpy = strdup(argv[++i]);
-		} else if (!strcmp(arg, "-auth")) {
+		} else if (!strcmp(arg, "-auth") || !strcmp(arg, "-xauth")) {
 			CHECK_ARGC
 			auth_file = strdup(argv[++i]);
 		} else if (!strcmp(arg, "-id") || !strcmp(arg, "-sid")) {
@@ -16361,6 +17023,9 @@ int main(int argc, char* argv[]) {
 		} else if (!strcmp(arg, "-timeout")) {
 			CHECK_ARGC
 			first_conn_timeout = atoi(argv[++i]);
+		} else if (!strcmp(arg, "-users")) {
+			CHECK_ARGC
+			users_list = strdup(argv[++i]);
 		} else if (!strcmp(arg, "-inetd")) {
 			inetd = 1;
 		} else if (!strcmp(arg, "-connect")) {
@@ -16927,6 +17592,8 @@ int main(int argc, char* argv[]) {
                     : "null");
 		fprintf(stderr, " gone:       %s\n", gone_cmd ? gone_cmd
                     : "null");
+		fprintf(stderr, " users:      %s\n", users_list ? users_list
+                    : "null");
 		fprintf(stderr, " using_shm:  %d\n", using_shm);
 		fprintf(stderr, " flipbytes:  %d\n", flip_byte_order);
 		fprintf(stderr, " onetile:    %d\n", single_copytile);
@@ -17162,7 +17829,8 @@ int main(int argc, char* argv[]) {
 				    " cursor mode\n");
 				rfbLog("  to: '-cursor most'.\n");
 				rfbLog("  to disable this behavior use: "
-				    "'-cursor arrow'.\n");
+				    "'-cursor arrow'\n");
+				rfbLog("  or '-noxfixes'.\n");
 			}
 		}
 		if(!strcmp(multiple_cursors_mode, "most")) {