tigervnc/unix/vncserver/vncserver

#!/usr/bin/env perl
#
#  Copyright (C) 2015-2019 Pierre Ossman for Cendio AB
#  Copyright (C) 2009-2010 D. R. Commander.  All Rights Reserved.
#  Copyright (C) 2005-2006 Sun Microsystems, Inc.  All Rights Reserved.
#  Copyright (C) 2002-2003 Constantin Kaplinsky.  All Rights Reserved.
#  Copyright (C) 2002-2005 RealVNC Ltd.
#  Copyright (C) 1999 AT&T Laboratories Cambridge.  All Rights Reserved.
#
#  This is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This software is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this software; if not, write to the Free Software
#  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
#  USA.
#

#
# vncserver - wrapper script to start an X VNC server.
#

# First make sure we're operating in a sane environment.
$exedir = "";
$slashndx = rindex($0, "/");
if($slashndx>=0) {
    $exedir = substr($0, 0, $slashndx+1);
}

&SanityCheck();

#
# Global variables.  You may want to configure some of these for
# your site
#

$vncUserDir = "$ENV{HOME}/.vnc";
$vncUserConfig = "$vncUserDir/config";

$vncSystemConfigDir = "/etc/tigervnc";
$vncSystemConfigDefaultsFile = "$vncSystemConfigDir/vncserver-config-defaults";
$vncSystemConfigMandatoryFile = "$vncSystemConfigDir/vncserver-config-mandatory";

$skipxstartup = 0;
$xauthorityFile = "$ENV{XAUTHORITY}" || "$ENV{HOME}/.Xauthority";

$xstartupFile = $vncUserDir . "/xstartup";
$defaultXStartup
    = ("#!/bin/sh\n\n".
       "OS=`uname -s`\n".
       "if [ \$OS = 'Linux' ]; then\n".
       "  case \"\$WINDOWMANAGER\" in\n".
       "    \*gnome\*)\n".
       "      if [ -e /etc/SuSE-release ]; then\n".
       "        PATH=\$PATH:/opt/gnome/bin\n".
       "        export PATH\n".
       "      fi\n".
       "      ;;\n".
       "  esac\n".
       "fi\n".
       "if [ -x /etc/X11/xinit/xinitrc ]; then\n".
       "  exec /etc/X11/xinit/xinitrc\n".
       "fi\n".
       "if [ -f /etc/X11/xinit/xinitrc ]; then\n".
       "  exec sh /etc/X11/xinit/xinitrc\n".
       "fi\n".
       "[ -r \$HOME/.Xresources ] && xrdb \$HOME/.Xresources\n".
       "xsetroot -solid grey\n".
       "xterm -geometry 80x24+10+10 -ls -title \"\$VNCDESKTOP Desktop\" &\n".
       "twm\n");

chop($host = `uname -n`);

if (-d "/etc/X11/fontpath.d") {
    $fontPath = "catalogue:/etc/X11/fontpath.d";
}

@fontpaths = ('/usr/share/X11/fonts', '/usr/share/fonts', '/usr/share/fonts/X11/');
if (! -l "/usr/lib/X11") {push(@fontpaths, '/usr/lib/X11/fonts');}
if (! -l "/usr/X11") {push(@fontpaths, '/usr/X11/lib/X11/fonts');}
if (! -l "/usr/X11R6") {push(@fontpaths, '/usr/X11R6/lib/X11/fonts');}
push(@fontpaths, '/usr/share/fonts/default');

@fonttypes = ('misc',
             '75dpi',
             '100dpi',
             'Speedo',
             'Type1');

foreach $_fpath (@fontpaths) {
    foreach $_ftype (@fonttypes) {
        if (-f "$_fpath/$_ftype/fonts.dir") {
            if (! -l "$_fpath/$_ftype") {
                $defFontPath .= "$_fpath/$_ftype,";
            }
        }
    }
}

if ($defFontPath) {
    if (substr($defFontPath, -1, 1) == ',') {
        chop $defFontPath;
    }
}

if ($fontPath eq "") {
    $fontPath = $defFontPath;
}

# Check command line options

&ParseOptions("-kill",1,"-help",0,"-h",0,"--help",0,"-list",0,
	      "-fg",0,"-autokill",0,"-noxstartup",0,"-xstartup",1);

&Usage() if ($opt{'-help'} || $opt{'-h'} || $opt{'--help'});

&Kill() if ($opt{'-kill'});

&List() if ($opt{'-list'});

if ($opt{'-noxstartup'}) {
    $skipxstartup = 1;
}
if ($opt{'-xstartup'}) {
    $xstartupFile = $opt{'-xstartup'};
}

# Create the user's vnc directory if necessary.
if (!(-e $vncUserDir)) {
    if (!mkdir($vncUserDir,0755)) {
	die "$prog: Could not create $vncUserDir.\n";
    }
}

# Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
    $displayNumber = $1;
    shift(@ARGV);
    if (!&CheckDisplayNumber($displayNumber)) {
	die "A VNC server is already running as :$displayNumber\n";
    }
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
    &Usage();
} else {
    $displayNumber = &GetDisplayNumber();
}

$vncPort = 5900 + $displayNumber;

$desktopName = "$host:$displayNumber ($ENV{USER})";

my %default_opts;
my %config;

# We set some reasonable defaults. Config file settings
# override these where present.
$default_opts{desktop} = &quotedString($desktopName);
$default_opts{auth} = &quotedString($xauthorityFile);
$default_opts{rfbwait} = 30000;
$default_opts{rfbauth} = "$vncUserDir/passwd";
$default_opts{rfbport} = $vncPort;
$default_opts{fp} = $fontPath if ($fontPath);
$default_opts{pn} = "";

# Load user-overrideable system defaults
LoadConfig($vncSystemConfigDefaultsFile);

# Then the user's settings
LoadConfig($vncUserConfig);

# And then override anything set above if mandatory settings exist.
# WARNING: "Mandatory" is used loosely here! As the man page says,
# there is nothing stopping someone from EASILY subverting the
# settings in $vncSystemConfigMandatoryFile by simply passing
# CLI args to vncserver, which trump config files! To properly
# hard force policy in a non-subvertible way would require major
# development work that touches Xvnc itself.
LoadConfig($vncSystemConfigMandatoryFile, 1);

#
# Check whether VNC authentication is enabled, and if so, prompt the user to
# create a VNC password if they don't already have one.
#

$securityTypeArgSpecified = 0;
$vncAuthEnabled = 0;
$passwordArgSpecified = 0;
@vncAuthStrings = ("vncauth", "tlsvnc", "x509vnc");

# ...first we check our configuration files' settings
if ($config{'securitytypes'}) {
  $securityTypeArgSpecified = 1;
  foreach $arg2 (split(',', $config{'securitytypes'})) {
    if (grep {$_ eq lc($arg2)} @vncAuthStrings) {
      $vncAuthEnabled = 1;
    }
  }
}
if ($config{'password'} ||
    $config{'passwordfile'} ||
    $config{'rfbauth'}) {
    $passwordArgSpecified = 1;
}

if ((!$securityTypeArgSpecified || $vncAuthEnabled) && !$passwordArgSpecified) {
    ($z,$z,$mode) = stat("$vncUserDir/passwd");
    if (!(-e "$vncUserDir/passwd") || ($mode & 077)) {
        warn "\nYou will require a password to access your desktops.\n\n";
        system($exedir."vncpasswd -q $vncUserDir/passwd");
        if (($? >> 8) != 0) {
            exit 1;
        }
    }
}

$desktopLog = "$vncUserDir/$host:$displayNumber.log";
unlink($desktopLog);

# Make an X server cookie and set up the Xauthority file
# mcookie is a part of util-linux, usually only GNU/Linux systems have it.
$cookie = `mcookie`;
# Fallback for non GNU/Linux OS - use /dev/urandom on systems that have it,
# otherwise use perl's random number generator, seeded with the sum
# of the current time, our PID and part of the encrypted form of the password.
if ($cookie eq "" && open(URANDOM, '<', '/dev/urandom')) {
  my $randata;
  if (sysread(URANDOM, $randata, 16) == 16) {
    $cookie = unpack 'h*', $randata;
  }
  close(URANDOM);
}
if ($cookie eq "") {
  srand(time+$$+unpack("L",`cat $vncUserDir/passwd`));
  for (1..16) {
    $cookie .= sprintf("%02x", int(rand(256)) % 256);
  }
}

open(XAUTH, "|xauth -f $xauthorityFile source -");
print XAUTH "add $host:$displayNumber . $cookie\n";
print XAUTH "add $host/unix:$displayNumber . $cookie\n";
close(XAUTH);

# Now start the X VNC Server

# We build up our Xvnc command with options
$cmd = $exedir."Xvnc :$displayNumber";

foreach my $k (sort keys %config) {
  $cmd .= " -$k $config{$k}";
  delete $default_opts{$k}; # file options take precedence
}

foreach my $k (sort keys %default_opts) {
  $cmd .= " -$k $default_opts{$k}";
}

# Run $cmd and record the process ID.
$pidFile = "$vncUserDir/$host:$displayNumber.pid";
system("$cmd & echo \$! >$pidFile");

# Give Xvnc a chance to start up

sleep(3);
if ($fontPath ne $defFontPath) {
    unless (kill 0, `cat $pidFile`) {
        if ($fpArgSpecified) {
	    warn "\nWARNING: The first attempt to start Xvnc failed, probably because the font\n";
	    warn "path you specified using the -fp argument is incorrect.  Attempting to\n";
	    warn "determine an appropriate font path for this system and restart Xvnc using\n";
	    warn "that font path ...\n";
        } else {
	    warn "\nWARNING: The first attempt to start Xvnc failed, possibly because the font\n";
	    warn "catalog is not properly configured.  Attempting to determine an appropriate\n";
	    warn "font path for this system and restart Xvnc using that font path ...\n";
        }
	$cmd =~ s@-fp [^ ]+@@;
	$cmd .= " -fp $defFontPath" if ($defFontPath);
	system("$cmd & echo \$! >$pidFile");
	sleep(3);
    }
}
unless (kill 0, `cat $pidFile`) {
    warn "Could not start Xvnc.\n\n";
    unlink $pidFile;
    open(LOG, "<$desktopLog");
    while (<LOG>) { print; }
    close(LOG);
    die "\n";
}

warn "\nNew '$desktopName' desktop is $host:$displayNumber\n\n";

# Create the user's xstartup script if necessary.
if (! $skipxstartup) {
    if (!(-e "$xstartupFile")) {
	warn "Creating default startup script $xstartupFile\n";
	open(XSTARTUP, ">$xstartupFile");
        print XSTARTUP $defaultXStartup;
        close(XSTARTUP);
        chmod 0755, "$xstartupFile";
    }
}

# Run the X startup script.
if (! $skipxstartup) {
    warn "Starting applications specified in $xstartupFile\n";
}
warn "Log file is $desktopLog\n\n";

# If the unix domain socket exists then use that (DISPLAY=:n) otherwise use
# TCP (DISPLAY=host:n)

if (-e "/tmp/.X11-unix/X$displayNumber" ||
    -e "/usr/spool/sockets/X11/$displayNumber")
{
    $ENV{DISPLAY}= ":$displayNumber";
} else {
    $ENV{DISPLAY}= "$host:$displayNumber";
}
$ENV{VNCDESKTOP}= $desktopName;

if ($opt{'-fg'}) {
    if (! $skipxstartup) {
        system("$xstartupFile >> " . &quotedString($desktopLog) . " 2>&1");
    }
    if (kill 0, `cat $pidFile`) {
        $opt{'-kill'} = ':'.$displayNumber;
        &Kill();
    }
} else {
    if ($opt{'-autokill'}) {
    	if (! $skipxstartup) {
            system("($xstartupFile; $0 -kill :$displayNumber) >> "
	     . &quotedString($desktopLog) . " 2>&1 &");
    	}
    } else {
    	if (! $skipxstartup) {
            system("$xstartupFile >> " . &quotedString($desktopLog)
	     . " 2>&1 &");
    	}
    }
}

exit;

###############################################################################
# Functions
###############################################################################

#
# Populate the global %config hash with settings from a specified
# vncserver configuration file if it exists
#
# Args: 1. file path
#       2. optional boolean flag to enable warning when a previously
#          set configuration setting is being overridden
#
sub LoadConfig {
  local ($configFile, $warnoverride) = @_;
  local ($toggle) = undef;

  if (stat($configFile)) {
    if (open(IN, $configFile)) {
      while (<IN>) {
        next if /^#/;
        if (my ($k, $v) = /^\s*(\w+)\s*=\s*(.+)$/) {
          $k = lc($k); # must normalize key case
          if ($warnoverride && $config{$k}) {
            print("Warning: $configFile is overriding previously defined '$k' to be '$v'\n");
          }
          $config{$k} = $v;
        } elsif ($_ =~ m/^\s*(\S+)/) {
          # We can't reasonably warn on override of toggles (e.g. AlwaysShared)
          # because it would get crazy to do so. We'd have to check if the
          # current config file being loaded defined the logical opposite setting
          # (NeverShared vs. AlwaysShared, etc etc).
          $toggle = lc($1); # must normalize key case
          $config{$toggle} = $k;
        }
      }
      close(IN);
    }
  }
}


#
# GetDisplayNumber gets the lowest available display number.  A display number
# n is taken if something is listening on the VNC server port (5900+n) or the
# X server port (6000+n).
#

sub GetDisplayNumber
{
    foreach $n (1..99) {
	if (&CheckDisplayNumber($n)) {
	    return $n+0; # Bruce Mah's workaround for bug in perl 5.005_02
	}
    }

    die "$prog: no free display number on $host.\n";
}


#
# CheckDisplayNumber checks if the given display number is available.  A
# display number n is taken if something is listening on the VNC server port
# (5900+n) or the X server port (6000+n).
#

sub CheckDisplayNumber
{
    local ($n) = @_;

    socket(S, $AF_INET, $SOCK_STREAM, 0) || die "$prog: socket failed: $!\n";
    eval 'setsockopt(S, &SOL_SOCKET, &SO_REUSEADDR, pack("l", 1))';
    if (!bind(S, pack('S n x12', $AF_INET, 6000 + $n))) {
	close(S);
	return 0;
    }
    close(S);

    socket(S, $AF_INET, $SOCK_STREAM, 0) || die "$prog: socket failed: $!\n";
    eval 'setsockopt(S, &SOL_SOCKET, &SO_REUSEADDR, pack("l", 1))';
    if (!bind(S, pack('S n x12', $AF_INET, 5900 + $n))) {
	close(S);
	return 0;
    }
    close(S);

    if (-e "/tmp/.X$n-lock") {
	warn "\nWarning: $host:$n is taken because of /tmp/.X$n-lock\n";
	warn "Remove this file if there is no X server $host:$n\n";
	return 0;
    }

    if (-e "/tmp/.X11-unix/X$n") {
	warn "\nWarning: $host:$n is taken because of /tmp/.X11-unix/X$n\n";
	warn "Remove this file if there is no X server $host:$n\n";
	return 0;
    }

    if (-e "/usr/spool/sockets/X11/$n") {
	warn("\nWarning: $host:$n is taken because of ".
             "/usr/spool/sockets/X11/$n\n");
	warn "Remove this file if there is no X server $host:$n\n";
	return 0;
    }

    return 1;
}

#
# quotedString returns a string which yields the original string when parsed
# by a shell.
#

sub quotedString
{
    local ($in) = @_;

    $in =~ s/\'/\'\"\'\"\'/g;

    return "'$in'";
}


#
# removeSlashes turns slashes into underscores for use as a file name.
#

sub removeSlashes
{
    local ($in) = @_;

    $in =~ s|/|_|g;

    return "$in";
}


#
# Usage
#

sub Usage
{
    die("\nusage: $prog [:<number>]\n".
	"                 [-fg]\n".
	"                 [-autokill]\n".
	"                 [-noxstartup]\n".
	"                 [-xstartup <file>]\n".
	"\n".
	"       $prog -kill <X-display>\n\n".
	"       $prog -list\n\n");
}


#
# List
#

sub List
{
    opendir(dir, $vncUserDir);
    my @filelist = readdir(dir);
    closedir(dir);
    print "\nTigerVNC server sessions:\n\n";
    print "X DISPLAY #\tPROCESS ID\n";
    foreach my $file (@filelist) {
	if ($file =~ /$host:(\d+)$\.pid/) {
	    chop($tmp_pid = `cat $vncUserDir/$file`);
	    if (kill 0, $tmp_pid) {
		print ":".$1."\t\t".`cat $vncUserDir/$file`;
	    } else {
		unlink ($vncUserDir . "/" . $file);
	    }
	}
    }
    exit;
}


#
# Kill
#

sub Kill
{
    $opt{'-kill'} =~ s/(:\d+)\.\d+$/$1/; # e.g. turn :1.0 into :1

    if ($opt{'-kill'} =~ /^:\d+$/) {
	$pidFile = "$vncUserDir/$host$opt{'-kill'}.pid";
    } else {
	if ($opt{'-kill'} !~ /^$host:/) {
	    die "\nCan't tell if $opt{'-kill'} is on $host\n".
		"Use -kill :<number> instead\n\n";
	}
	$pidFile = "$vncUserDir/$opt{'-kill'}.pid";
    }

    if (! -r $pidFile) {
	die "\nCan't find file $pidFile\n".
	    "You'll have to kill the Xvnc process manually\n\n";
    }

    $SIG{'HUP'} = 'IGNORE';
    chop($pid = `cat $pidFile`);
    warn "Killing Xvnc process ID $pid\n";

    if (kill 0, $pid) {
	system("kill $pid");
	sleep(1);
	if (kill 0, $pid) {
	    print "Xvnc seems to be deadlocked.  Kill the process manually and then re-run\n";
	    print "    ".$0." -kill ".$opt{'-kill'}."\n";
	    print "to clean up the socket files.\n";
	    exit
	}

    } else {
	warn "Xvnc process ID $pid already killed\n";
	$opt{'-kill'} =~ s/://;

	if (-e "/tmp/.X11-unix/X$opt{'-kill'}") {
	    print "Xvnc did not appear to shut down cleanly.";
	    print " Removing /tmp/.X11-unix/X$opt{'-kill'}\n";
	    unlink "/tmp/.X11-unix/X$opt{'-kill'}";
	}
	if (-e "/tmp/.X$opt{'-kill'}-lock") {
	    print "Xvnc did not appear to shut down cleanly.";
	    print " Removing /tmp/.X$opt{'-kill'}-lock\n";
	    unlink "/tmp/.X$opt{'-kill'}-lock";
	}
    }

    unlink $pidFile;
    exit;
}


#
# ParseOptions takes a list of possible options and a boolean indicating
# whether the option has a value following, and sets up an associative array
# %opt of the values of the options given on the command line. It removes all
# the arguments it uses from @ARGV and returns them in @optArgs.
#

sub ParseOptions
{
    local (@optval) = @_;
    local ($opt, @opts, %valFollows, @newargs);

    while (@optval) {
	$opt = shift(@optval);
	push(@opts,$opt);
	$valFollows{$opt} = shift(@optval);
    }

    @optArgs = ();
    %opt = ();

    arg: while (defined($arg = shift(@ARGV))) {
	foreach $opt (@opts) {
	    if ($arg eq $opt) {
		push(@optArgs, $arg);
		if ($valFollows{$opt}) {
		    if (@ARGV == 0) {
			&Usage();
		    }
		    $opt{$opt} = shift(@ARGV);
		    push(@optArgs, $opt{$opt});
		} else {
		    $opt{$opt} = 1;
		}
		next arg;
	    }
	}
	push(@newargs,$arg);
    }

    @ARGV = @newargs;
}


# Routine to make sure we're operating in a sane environment.
sub SanityCheck
{
    local ($cmd);

    # Get the program name
    ($prog) = ($0 =~ m|([^/]+)$|);

    #
    # Check we have all the commands we'll need on the path.
    #

 cmd:
    foreach $cmd ("uname","xauth") {
	for (split(/:/,$ENV{PATH})) {
	    if (-x "$_/$cmd") {
		next cmd;
	    }
	}
	die "$prog: couldn't find \"$cmd\" on your PATH.\n";
    }

    if($exedir eq "") {
      cmd2:
	foreach $cmd ("Xvnc","vncpasswd") {
	    for (split(/:/,$ENV{PATH})) {
		if (-x "$_/$cmd") {
		    next cmd2;
		}
	    }
	    die "$prog: couldn't find \"$cmd\" on your PATH.\n";
	}
    }
    else {
      cmd3:
	foreach $cmd ($exedir."Xvnc",$exedir."vncpasswd") {
	    for (split(/:/,$ENV{PATH})) {
		if (-x "$cmd") {
		    next cmd3;
		}
	    }
	    die "$prog: couldn't find \"$cmd\".\n";
	}
    }

    if (!defined($ENV{HOME})) {
	die "$prog: The HOME environment variable is not set.\n";
    }

    #
    # Find socket constants. 'use Socket' is a perl5-ism, so we wrap it in an
    # eval, and if it fails we try 'require "sys/socket.ph"'.  If this fails,
    # we just guess at the values.  If you find perl moaning here, just
    # hard-code the values of AF_INET and SOCK_STREAM.  You can find these out
    # for your platform by looking in /usr/include/sys/socket.h and related
    # files.
    #

    chop($os = `uname`);
    chop($osrev = `uname -r`);

    eval 'use Socket';
    if ($@) {
	eval 'require "sys/socket.ph"';
	if ($@) {
	    if (($os eq "SunOS") && ($osrev !~ /^4/)) {
		$AF_INET = 2;
		$SOCK_STREAM = 2;
	    } else {
		$AF_INET = 2;
		$SOCK_STREAM = 1;
	    }
	} else {
	    $AF_INET = &AF_INET;
	    $SOCK_STREAM = &SOCK_STREAM;
	}
    } else {
	$AF_INET = &AF_INET;
	$SOCK_STREAM = &SOCK_STREAM;
    }
}