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#!/usr/bin/env perl
#
# Copyright (c) 2009 by Karl J. Runge <runge@karlrunge.com>
#
# ultravnc_repeater.pl 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.
#
# ultravnc_repeater.pl 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 ultravnc_repeater.pl; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA
# or see <http://www.gnu.org/licenses/>.
#
my $usage = '
ultravnc_repeater.pl:
perl script implementing the ultravnc repeater
proxy protocol.
protocol: Listen on one port for vnc clients (default 5900.)
Listen on one port for vnc servers (default 5500.)
Read 250 bytes from connecting vnc client or server.
Accept ID:<string> from clients and servers, connect them
together once both are present.
The string "RFB 000.000\n" is sent to the client (the client
must understand this means send ID:... or host:port.)
Also accept <host>:<port> from clients and make the
connection to the vnc server immediately.
Note there is no authentication or security WRT ID names or
identities; it us up to the client and server to manage that
and whether to encrypt the session, etc.
usage: ultravnc_repeater.pl [-r] [client_port [server_port]]
Use -r to refuse new server/client connections with an existing
server/client ID. The default is to close the previous one.
Examples:
ultravnc_repeater.pl -r
ultravnc_repeater.pl 5901
ultravnc_repeater.pl 5901 5501
';
use warnings;
use strict;
use IO::Socket::INET;
use IO::Select;
my $prog = 'ultravnc_repeater.pl';
my %ID;
my $refuse = 0;
my $init_timeout = 3;
if (@ARGV && $ARGV[0] =~ /-h/) {
print $usage;
exit 0;
}
if (@ARGV && $ARGV[0] eq '-r') {
$refuse = 1;
shift;
}
my $client_port = shift;
my $server_port = shift;
$client_port = 5900 unless $client_port;
$server_port = 5500 unless $server_port;
my $repeater_bufsize = 250;
$repeater_bufsize = $ENV{BUFSIZE} if exists $ENV{BUFSIZE};
my ($RIN, $WIN, $EIN, $ROUT);
my $client_listen = IO::Socket::INET->new(
Listen => 10,
LocalPort => $client_port,
Proto => "tcp"
);
if (! $client_listen) {
cleanup();
die "$prog: error: client listen on port $client_port: $!\n";
}
my $server_listen = IO::Socket::INET->new(
Listen => 10,
LocalPort => $server_port,
Proto => "tcp"
);
if (! $server_listen) {
cleanup();
die "$prog: error: server listen on port $server_port: $!\n";
}
my $select = new IO::Select();
if (! select) {
cleanup();
die "$prog: select $!\n";
}
$select->add($client_listen);
$select->add($server_listen);
$SIG{INT} = sub {cleanup(); exit;};
$SIG{TERM} = sub {cleanup(); exit;};
my $SOCK1 = '';
my $SOCK2 = '';
my $CURR = '';
print "watching for connections on ports $server_port/server and $client_port/client\n";
select(STDERR); $| = 1;
select(STDOUT); $| = 1;
my $alarm_sock = '';
my $got_alarm = 0;
sub alarm_handler {
print "$prog: got sig alarm.\n";
if ($alarm_sock ne '') {
close $alarm_sock;
}
$alarm_sock = '';
$got_alarm = 1;
}
while (my @ready = $select->can_read()) {
foreach my $fh (@ready) {
if ($fh == $client_listen) {
print "new vnc client connecting at ", scalar(localtime), "\n";
} elsif ($fh == $server_listen) {
print "new vnc server connecting at ", scalar(localtime), "\n";
}
my $sock = $fh->accept();
if (! $sock) {
print "$prog: accept $!\n";
next;
}
if ($fh == $client_listen) {
my $str = "RFB 000.000\n";
my $len = length $str;
my $n = syswrite($sock, $str, $len, 0);
if ($n != $len) {
print "$prog: bad $str write: $n != $len $!\n";
close $sock;
}
}
my $buf = '';
my $size = $repeater_bufsize;
$size = 1024 unless $size;
$SIG{ALRM} = "alarm_handler";
$alarm_sock = $sock;
$got_alarm = 0;
alarm($init_timeout);
my $n = sysread($sock, $buf, $size);
alarm(0);
if ($got_alarm) {
print "$prog: read timed out: $!\n";
} elsif (! defined $n) {
print "$prog: read error: $!\n";
} elsif ($repeater_bufsize > 0 && $n != $size) {
print "$prog: short read $n != $size $!\n";
close $sock;
} elsif ($fh == $client_listen) {
do_new_client($sock, $buf);
} elsif ($fh == $server_listen) {
do_new_server($sock, $buf);
}
}
}
sub do_new_client {
my ($sock, $buf) = @_;
if ($buf =~ /^ID:(\w+)/) {
my $id = $1;
if (exists $ID{$id}) {
if ($ID{$id}{client}) {
print "refusing extra vnc client for ID:$id\n";
close $sock;
return;
if ($refuse) {
print "refusing extra vnc client for ID:$id\n";
close $sock;
return;
} else {
print "closing and deleting previous vnc client with ID:$id\n";
close $ID{$id}{sock};
print "storing new vnc client with ID:$id\n";
$ID{$id}{client} = 1;
$ID{$id}{sock} = $sock;
}
} else {
print "hooking up new vnc client with existing vnc server for ID:$id\n";
my $sock2 = $ID{$id}{sock};
delete $ID{$id};
hookup($sock, $sock2, "ID:$id");
}
} else {
print "storing new vnc client with ID:$id\n";
$ID{$id}{client} = 1;
$ID{$id}{sock} = $sock;
}
} else {
my $str = sprintf("%s", $buf);
my $host = '';
my $port = '';
if ($str =~ /^(.+):(\d+)/) {
$host = $1;
$port = $2;
} else {
$host = $str;
$port = 5900;
}
if ($port < 0) {
my $pnew = -$port;
print "resetting port from $port to $pnew\n";
$port = $pnew;
} elsif ($port < 200) {
my $pnew = $port + 5900;
print "resetting port from $port to $pnew\n";
$port = $pnew;
}
print "making vnc client connection directly to vnc server $host:$port\n";
my $sock2 = IO::Socket::INET->new(
PeerAddr => $host,
PeerPort => $port,
Proto => "tcp"
);
if (!$sock2) {
print "failed to connect to $host:$port\n";
close $sock;
return;
}
hookup($sock, $sock2, "$host:$port");
}
}
sub do_new_server {
my ($sock, $buf) = @_;
if ($buf =~ /^ID:(\w+)/) {
my $id = $1;
my $store = 1;
if (exists $ID{$id}) {
if (! $ID{$id}{client}) {
if ($refuse) {
print "refusing extra vnc server for ID:$id\n";
close $sock;
return;
} else {
print "closing and deleting previous vnc server with ID:$id\n";
close $ID{$id}{sock};
print "storing new vnc server with ID:$id\n";
$ID{$id}{client} = 0;
$ID{$id}{sock} = $sock;
}
} else {
print "hooking up new vnc server with existing vnc client for ID:$id\n";
my $sock2 = $ID{$id}{sock};
delete $ID{$id};
hookup($sock, $sock2, "ID:$id");
}
} else {
print "storing new vnc server with ID:$id\n";
$ID{$id}{client} = 0;
$ID{$id}{sock} = $sock;
}
} else {
print "invalid ID:NNNNN string for vnc server: $buf\n";
close $sock;
return;
}
}
sub handler {
print STDERR "$prog\[$$/$CURR]: got SIGTERM.\n";
close $SOCK1 if $SOCK1;
close $SOCK2 if $SOCK2;
exit;
}
sub hookup {
my ($sock1, $sock2, $tag) = @_;
my $worker = fork();
if (! defined $worker) {
print "failed to fork worker: $!\n";
close $sock1;
close $sock2;
return;
} elsif ($worker) {
close $sock1;
close $sock2;
wait;
} else {
cleanup();
if (fork) {
exit 0;
}
setpgrp(0, 0);
$SOCK1 = $sock1;
$SOCK2 = $sock2;
$CURR = $tag;
$SIG{TERM} = "handler";
$SIG{INT} = "handler";
xfer_both($sock1, $sock2);
exit 0;
}
}
sub xfer {
my ($in, $out) = @_;
$RIN = $WIN = $EIN = "";
$ROUT = "";
vec($RIN, fileno($in), 1) = 1;
vec($WIN, fileno($in), 1) = 1;
$EIN = $RIN | $WIN;
my $buf;
while (1) {
my $nf = 0;
while (! $nf) {
$nf = select($ROUT=$RIN, undef, undef, undef);
}
my $len = sysread($in, $buf, 8192);
if (! defined($len)) {
next if $! =~ /^Interrupted/;
print STDERR "$prog\[$$/$CURR]: $!\n";
last;
} elsif ($len == 0) {
print STDERR "$prog\[$$/$CURR]: Input is EOF.\n";
last;
}
my $offset = 0;
my $quit = 0;
while ($len) {
my $written = syswrite($out, $buf, $len, $offset);
if (! defined $written) {
print STDERR "$prog\[$$/$CURR]: Output is EOF. $!\n";
$quit = 1;
last;
}
$len -= $written;
$offset += $written;
}
last if $quit;
}
close($out);
close($in);
print STDERR "$prog\[$$/$CURR]: finished xfer.\n";
}
sub xfer_both {
my ($sock1, $sock2) = @_;
my $parent = $$;
my $child = fork();
if (! defined $child) {
print STDERR "$prog\[$$/$CURR] failed to fork: $!\n";
return;
}
$SIG{TERM} = "handler";
$SIG{INT} = "handler";
if ($child) {
print STDERR "$prog parent[$$/$CURR] 1 -> 2\n";
xfer($sock1, $sock2);
select(undef, undef, undef, 0.25);
if (kill 0, $child) {
select(undef, undef, undef, 0.9);
if (kill 0, $child) {
print STDERR "$prog\[$$/$CURR]: kill TERM child $child\n";
kill "TERM", $child;
} else {
print STDERR "$prog\[$$/$CURR]: child $child gone.\n";
}
}
} else {
select(undef, undef, undef, 0.05);
print STDERR "$prog child [$$/$CURR] 2 -> 1\n";
xfer($sock2, $sock1);
select(undef, undef, undef, 0.25);
if (kill 0, $parent) {
select(undef, undef, undef, 0.8);
if (kill 0, $parent) {
print STDERR "$prog\[$$/$CURR]: kill TERM parent $parent\n";
kill "TERM", $parent;
} else {
print STDERR "$prog\[$$/$CURR]: parent $parent gone.\n";
}
}
}
}
sub cleanup {
close $client_listen if defined $client_listen;
close $server_listen if defined $server_listen;
foreach my $id (keys %ID) {
close $ID{$id}{sock};
}
}
|