[RFC] framework of Ruby/Tk + VNC

[Hidetoshi NAGAI]

Hi,

I'm working on a framework of Ruby/Tk + VNC.
Its purpose is to put GUI applications of Ruby/Tk on internet view.
The concept of the framework is,

* Use VNC (RFB protocol)

* A GUI application is running on a safe (safe-Tk) based
slave interpreter (usually, $SAFE == 4).
If required, you can also use a non-safe based slave.

* Never use general window managers to decrease security risk.
Except a VNC server, only one Ruby/Tk process is running.
# In the future, it may be expected that Ruby/Tk has
# RFB server functions and no VNC server is required
# for this purpose.

* A canvas widget of the master interpreter works like
as a window manager. The canvas widget administers the
slave interpreter's root/toplevel widgets by window items
embedded them.

By comparison with using tclplugin, probably, the followings
are advantages.

* If the user already has a kind of VNC viewer,
he can use it to access the application.

* When the user access the application by a web browser,
the application server can send a JAVA viewer applet.
Therefore, the user doesn't need to install any plugins.

* Even if the application uses some Tcl/Tk extensions,
the user doesn't need to install such extensions.

* No need to send the source of the application.
Funcamentally, interchanged data are only window events
and display images on RFB protocol.
So, it can decrease the cost of care for security.

Disadvantages are,

* Slow, because it is remote access through networks.

* Much resources are required on the server.

A sample script based on this concept is attached
at the end of this mail.
That requires 2005/06/08 or later version of Ruby.
Please note that, because of using multi-tk library,
the description of script on the slave interpreter is
almost same as the description of usual Ruby/Tk script.

Although it is an old and slow machine and is not
decided how long term it is available to use,
there is a server to try the sample script.
Please access 131.206.154.81:33 by VNC viewer,
or http://131.206.154.81/ by web browser.
Of course, Ruby is not required on user's machine.

# When by a web browser, a dialog to require password is shown.
# Please ignore it and press the "OK" button with empty password.

Any comments (or wish to participate in the development ;-))
are welcome.

Hidetoshi NAGAI ([email protected])

---------------------------------------------------------------
The following is the sample script.
===============================================================
#!/usr/bin/env ruby
#
# Ruby/Tk+VNC :: concept example
#
# by Hidetoshi NAGAI ([email protected])
#
require 'multi-tk'
require 'singleton'

class VNC_Wall < TkCanvas
include Singleton

def initialize
@new_relx = 0.4
@new_rely = 0.4

superwidth=>TkWinfo.screenwidth('.'),
:height=>TkWinfo.screenheight('.'))
self.pack
end

######################################

class Window_Frame < TkcWindow
def _title_bind
@titlebar.bind('ButtonPress-1',
proc{|rx, ry|
@rx = rx; @ry = ry; @sx, @sy = self.coords
@base.raise
}, '%X', '%Y')

@titlebar.bind('B1-Motion',
proc{|rx, ry|
wx = @wall.winfo_rootx; wy = @wall.winfo_rooty
if rx > wx && rx < wx + @wall.width &&
ry > wy && ry < wy + @wall.height
self.coords = [@sx + (rx - @rx), @sy + (ry - @ry)]
end
}, '%X', '%Y')
end
private :_title_bind

def initialize(wall, title, coords, keys={})
@wall = wall
@base = TkFrame.new(@wall, :borderwidth=>3, :relief=>:ridge)
@titlebar = TkLabel.new(@base, :text=>" #{title} ", :relief=>:raised,
:foreground=>'white',
:background=>'midnight blue').packfill=>:x)
@container = TkFrame.new(@base, :container=>true).packfill=>:both,
:expand=>true)
super(@wall, coords[0], coords[1], keys)
self.window = @base
_title_bind
end

def winid
@container.winfo_id
end

def title(txt)
@titlebar.text(txt)
end
end

######################################

def new_window(title, coords, keys={})
keys = _symbolkey2str(keys)
keys['anchor'] = 'nw'
Window_Frame.new(self, title, coords, keys)
end

def new_root(keys={})
keys = _symbolkey2str(keys)
coords = keys.delete('coords') ||
[self.width * @new_relx, self.height * @new_rely]
title = keys.delete('title') || 'root'
new_window(title, coords, keys)
end
private :new_root

######################################

class TOPLEVEL_ARG < Exception
alias value message
end

######################################

def new_toplevel(slave_ip, top,
coords=[self.width * @new_relx, self.height * @new_rely])
w = new_window("toplevel(#{top})", coords)
MultiTkIp.invoke_hidden(slave_ip, 'toplevel', top, '-use', w.winid)
end

def replace_toplevel_cmd(slave_ip)
th = Thread.new(slave_ip){|ip|
begin
Thread.stop
rescue TOPLEVEL_ARG => arg
begin
new_toplevel(ip, arg.value)
rescue Exception => e
end
retry
end
}

cmd = TkComm._get_eval_string(proc{|t|
th.raise(TOPLEVEL_ARG.new(t))
until slave_ip.eval_proc{TkWinfo.exist?(t)}
Thread.pass
Tk.update
end
})
slave_ip._eval("proc toplevel {path} {#{cmd} $path}")
end

######################################

def new_slave(safe=nil, keys={}, &b)
if safe.kind_of?(Hash)
keys = _symbolkey2str(safe)
safe = keys.delete('safe')
end
w = new_root(keys)
ip = MultiTkIp.new_trusted_slave(safe, {:use=>w.winid}, &b)
MultiTkIp.hide_cmd(ip, 'toplevel')
replace_toplevel_cmd(ip)
ip
end
alias new_trusted_slave new_slave

def new_safe_slave(safe=4, keys={}, &b)
if safe.kind_of?(Hash)
keys = _symbolkey2str(safe)
safe = keys.delete('safe') || 4
end
w = new_root(keys)
ip = MultiTkIp.new_safe_slave(safe, {:use=>w.winid}, &b)
replace_toplevel_cmd(ip)
ip
end
alias new_safeTk new_safe_slave
end

#===============================================================

if $0 == __FILE__
timeout = 60

wall = VNC_Wall.instance
wall[:background] = 'skyblue'

#-----------------------------------------------------------

TkcText.new(wall, 150, 50, :fill=>'navyblue', :font=>'courier -14',
:text=>"Ruby/Tk+VNC :: concept example")
TkcText.new(wall, 370, 170, :text=><<EOT)
The root window of the safeTk IP is
embedded in Master IP's frame widget.

You can move the root window by
'Button-1 + Motion' on the titlebar.
Master IP works like as a window manager.

No window manager on the VNC server.
Running one Ruby/Tk process only.
EOT
#'
TkcText.new(wall, 150, 300,
:text=>"This example will exit in #{timeout} seconds.")
TkcText.new(wall, 350, 350,
:text=>"This is Master IP's canvas widget.\n\t($SAFE==#{$SAFE})")

#-----------------------------------------------------------

# ip = wall.new_trusted_slavetitle=>'slave root', :coords=>[50, 70]){
# ip = wall.new_safeTk(3, :title=>'slave root', :coords=>[50, 70]){
ip = wall.new_safeTktitle=>'slave root', :coords=>[50, 70]){
TkLabel.newtext=>"safeTk interpreter's root").packpadx=>10, ady=>5)

top = nil
cnt = 0

b1 = TkButton.newtext=>'create Toplevel')

b2 = TkButton.newtext=>'add label to the toplevel', :state=>:disabled,
:command=>proc{
cnt += 1
TkLabel.new(top,
:text=>"Pressed(#{cnt})!! $SAFE=#{$SAFE}"
).pack
})

b1.command = proc{
top = TkToplevel.new
b1[:state] = :disabled
b2[:state] = :active
TkLabel.new(top,
:text=>'New toplevel of slaveIP').packpadx=>20, ady=>30)
}

label = TkLabel.newforeground=>'red', :text=>"\n")
timer = TkTimer.new(500, 1, proc{label.text = "\n"})
TkButton.newtext=>'BUTTON',
:command=>proc{
timer.cancel
label.text = "button is pressed!!\n($SAFE==#{$SAFE})"
timer.start
}).packpadx=>5, ady=>5, :fill=>:x)
label.pack

Tk.pack(b1, b2, :fill=>:x, adx=>5, ady=>5)
}

#-----------------------------------------------------------

Tk.after(timeout * 1000){exit}
Tk.mainloop
end

 

[Logan Capaldo]

Hi,
=20
I'm working on a framework of Ruby/Tk + VNC.
Its purpose is to put GUI applications of Ruby/Tk on internet view.
The concept of the framework is,
=20
* Use VNC (RFB protocol)
=20
* A GUI application is running on a safe (safe-Tk) based
slave interpreter (usually, $SAFE =3D=3D 4).
If required, you can also use a non-safe based slave.
=20
* Never use general window managers to decrease security risk.
Except a VNC server, only one Ruby/Tk process is running.
# In the future, it may be expected that Ruby/Tk has
# RFB server functions and no VNC server is required
# for this purpose.
=20
* A canvas widget of the master interpreter works like
as a window manager. The canvas widget administers the
slave interpreter's root/toplevel widgets by window items
embedded them.
=20
By comparison with using tclplugin, probably, the followings
are advantages.
=20
* If the user already has a kind of VNC viewer,
he can use it to access the application.
=20
* When the user access the application by a web browser,
the application server can send a JAVA viewer applet.
Therefore, the user doesn't need to install any plugins.
=20
* Even if the application uses some Tcl/Tk extensions,
the user doesn't need to install such extensions.
=20
* No need to send the source of the application.
Funcamentally, interchanged data are only window events
and display images on RFB protocol.
So, it can decrease the cost of care for security.
=20
Disadvantages are,
=20
* Slow, because it is remote access through networks.
=20
* Much resources are required on the server.
=20
A sample script based on this concept is attached
at the end of this mail.
That requires 2005/06/08 or later version of Ruby.
Please note that, because of using multi-tk library,
the description of script on the slave interpreter is
almost same as the description of usual Ruby/Tk script.
=20
Although it is an old and slow machine and is not
decided how long term it is available to use,
there is a server to try the sample script.
Please access 131.206.154.81:33 by VNC viewer,
or http://131.206.154.81/ by web browser.
Of course, Ruby is not required on user's machine.
=20
# When by a web browser, a dialog to require password is shown.
# Please ignore it and press the "OK" button with empty password.
=20
Any comments (or wish to participate in the development ;-))
are welcome.
=20
Hidetoshi NAGAI ([email protected])
=20

=20

Neat! Once upon a time I read up on the RFB protocol, I don't believe
it would be too difficult to make a Tk/RFB server assuming Tk's
drawing and input layers are abstracted (which I am sure they are
since it is so portable).

 

[gregarican]

* Never use general window managers to decrease security risk.
Except a VNC server, only one Ruby/Tk process is running.
# In the future, it may be expected that Ruby/Tk has
# RFB server functions and no VNC server is required
# for this purpose.

This is a very interesting project. One question. The server isn't
running a window manager and the Ruby/Tk process is acting as the
window manager through the TkCanvas object, correct? What I don't
understand is how a VNC client automatically connects to this TkCanvas
object that's acting as the VNC server's window manager. Is there some
static mapping or correlation that has to be made manually on the
server? How does the VNC server bind itself to the Ruby/Tk process?

 

[Hidetoshi NAGAI]

From: Logan Capaldo <[email protected]>
Subject: Re: [RFC] framework of Ruby/Tk + VNC
Date: Fri, 10 Jun 2005 20:35:56 +0900

Neat! Once upon a time I read up on the RFB protocol, I don't believe
it would be too difficult to make a Tk/RFB server assuming Tk's
drawing and input layers are abstracted (which I am sure they are
since it is so portable).

I think so too.
But, unfortunately, I couldn't find such Tk/RFB server.

 

[Hidetoshi NAGAI]

From: "gregarican" <[email protected]>
Subject: Re: framework of Ruby/Tk + VNC
Date: Fri, 10 Jun 2005 22:55:28 +0900

This is a very interesting project.

Thank you.

One question. The server isn't
running a window manager and the Ruby/Tk process is acting as the
window manager through the TkCanvas object, correct?

The TkCanvas object is not a real window manager.
So, at present, I don't expect running other window applications
at same time.
However, I want to make the TkCanvas object a window manager for
the slave interpreter.

What I don't
understand is how a VNC client automatically connects to this TkCanvas
object that's acting as the VNC server's window manager. Is there some
static mapping or correlation that has to be made manually on the
server? How does the VNC server bind itself to the Ruby/Tk process?

In this case, I use the following way.

* Xvnc is started from inetd and connected to X Display Manager
(Xvnc -inet -query localhost ...).

* X Display Manager starts up a greeter on the X (Xvnc) server.
But the greeter is replaced to a Ruby/Tk application launcher.

* The application launcher do setup steps (if needed),
and executes Ruby/Tk.
So, the Ruby/Tk process is placed on a window manager proces.

* When the Ruby/Tk process is finished,
Xvnc treats it as the end of Xsession, and shuts down the socket.

 

[gregarican]

In this case, I use the following way.

* Xvnc is started from inetd and connected to X Display Manager
(Xvnc -inet -query localhost ...).


* X Display Manager starts up a greeter on the X (Xvnc) server.
But the greeter is replaced to a Ruby/Tk application launcher.


* The application launcher do setup steps (if needed),
and executes Ruby/Tk.
So, the Ruby/Tk process is placed on a window manager proces.


* When the Ruby/Tk process is finished,
Xvnc treats it as the end of Xsession, and shuts down the socket.

Oh I see now. In the past I have used VNC on everything from Sharp
Zaurus PDA's to Linux boxes to my Windows boxes. But I hadn't looked
"under the hood" to see how it connected for sessions. In terms of the
Ruby/Tk framwork for it I was thinking in terms of my Windows
environment. And I wasn't sure of a way to redirect a VNC session from
the default window manager (i.e. - Windows itself). But this makes
sense how you can redirect things through the Xvnc/XDM session for the
non-Windows world. There's a lot more flexibility there.

Great work. I must say I am constantly impressed with the Ruby
community. It is friendly, knowledgeable, and has a very mature
application/binding collection. This is just another example.

 

[Hidetoshi NAGAI]

From: "gregarican" <[email protected]>
Subject: Re: framework of Ruby/Tk + VNC
Date: Sat, 11 Jun 2005 03:10:29 +0900

Oh I see now. In the past I have used VNC on everything from Sharp
Zaurus PDA's to Linux boxes to my Windows boxes. But I hadn't looked
"under the hood" to see how it connected for sessions. In terms of the
Ruby/Tk framwork for it I was thinking in terms of my Windows
environment. And I wasn't sure of a way to redirect a VNC session from
the default window manager (i.e. - Windows itself).

Although I don't know details of Windows version of VNC server,
I heard that a (some?) kind of VNC server on Windows supports
to treat only one window under a VNC session.
If that is true, by supplying the master-IP's root window of
the framework on such VNC server, you'll be able to make a
multi-window application which allows restricted access to
your Windows boxes.

 

[Michal 'hramrach' Suchanek]

Hi, Hello

I'm working on a framework of Ruby/Tk + VNC.
Its purpose is to put GUI applications of Ruby/Tk on internet view.
The concept of the framework is,

* Use VNC (RFB protocol)

* A GUI application is running on a safe (safe-Tk) based
slave interpreter (usually, $SAFE == 4).
If required, you can also use a non-safe based slave.

* Never use general window managers to decrease security risk.
Except a VNC server, only one Ruby/Tk process is running.
# In the future, it may be expected that Ruby/Tk has
# RFB server functions and no VNC server is required
# for this purpose.

Isn't there already some rfb support for tk? I beleive I found it while
seaching for widget toolkits for vnc a fwe weeks ago. Given that the
only one I found was tk I decided I will use web instead.

Thanks

Michal Suchanek

 

[gregarican]

You are correct. There are options under the various Windows VNC
flavors that allows you to specify which window to share for a VNC
session, as opposed to sharing the entire Windows desktop as a whole.
So I suppose this could be very possible on the Win32 platform as well.

 

[Hidetoshi NAGAI]

From: Michal 'hramrach' Suchanek <[email protected]>
Subject: Re: [RFC] framework of Ruby/Tk + VNC
Date: Mon, 13 Jun 2005 00:17:22 +0900

Isn't there already some rfb support for tk? I beleive I found it while
seaching for widget toolkits for vnc a fwe weeks ago.

I couldn't find such library.
Although I could find tclRFB library, it doesn't seem to treat
Tk widgets directly.
If you know a download site of such RFB for Tk widgets,
please tell me the URL.
I'll create Ruby/Tk's wrapper library for the library.