WinVNC & -nevershared

Rob Kenyon robdkenyon "at"
Wed, 06 Mar 2002 01:26:29 +0000

I did.

I can honestly state that I actually read the docs before posting.
Notice that "ConnectPriority" states:  

By default, all WinVNC servers will disconnect any existing connections
when an incoming, non-shared connection is authenticated.  This
behaviour is undesirable when the server machine is being used as a
shared workstation by several users or when remoting a single display to
multiple clients for vewing, as in a classroom situation. 

ConnectPriority indicates what WinVNC should do when a non-shared
connection is received: 
0 = Disconnect all existing connections. 
1 = Don't disconnect any existing connections. 
2 = Refuse the new connection. 

Note the "non-shared" throughout.   Non-shared is fine and works fine
and is rejected properly and doesn't kick the first user.  The problem
is that if the second user asked for a shared connection, it's accepted
- even if the first client did not say that they wanted a shared
connection (default on the java/web client is non-shared).

Now you see the security issue.  A second user can ALWAYS join a
connection and see the screen (in fact, they can help type or move the
mouse) even if the first user requested a non-shared session.

The Xvnc --nevershared option looks like what I need as it states that
it instructs the server to never accept a request for shared sessions.

Any more thoughts?

This isn't intended as a challenge/quiz/test - I really would like to
know if there's an answer.

Note, locking by IP does not work in this case as most clients will be
dial up, non-static IP.


-----Original Message-----
From: owner-vnc-list "at"
[mailto:owner-vnc-list "at"] On Behalf Of Michael Ossmann
Sent: Tuesday, March 05, 2002 11:20 AM
To: vnc-list "at"
Subject: Re: WinVNC & -nevershared

On Mon, Mar 04, 2002 at 06:59:11PM -0700, Rob Kenyon wrote:
> As my message stated, ConnectPriorty works fine, but it doesn't 
> prevent a second user from requesting a shared session, connecting and

> seeing the first user's screen.

Yes, but did you actually try setting it to 2, not 1?

Mike Ossmann, Tarantella/UNIX Engineer/Instructor
Alternative Technology, Inc.
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