RE: Cygwin/X server -query fails with recent versions of Gnome GDM

["Richard Evans" <richard dot evans at datanomic dot com>]

Thanks for the analysis.  I did try adding root and gdm /etc/passwd at
the cygwin end and the query then worked.

I agree that this is a bug in GDM - I will see about posting a report
there.  Might be worth adding this to a FAQ in case GDM is not fixed.

Richard

-----Original Message-----
From: Jon TURNEY [mailto:jon.turney@dronecode.org.uk] 
Sent: 07 October 2009 19:18
To: cygwin-xfree@cygwin.com
Cc: Richard Evans
Subject: Re: Cygwin/X server -query fails with recent versions of Gnome
GDM

On 30/09/2009 10:34, Richard Evans wrote:
> Cygwin 1.7beta, cygcheck output attached.
>
> I am trying to start a remote session using:
>
> XWin -query host
>
> where the host is running GDM from Gnome 2.28.  The connect fails.   A
> wireshark network snoop (attached) shows that GDM is sending

Thanks for the packet capture, that helps a lot understanding what's
happening 
here.

> X_ChangeHosts requests with an address family of 5 (ServerInterpreted)
> and a address like
>
> 	localuser:root
>
> XWin responds with a BadValue error and the connection attempt fails.
I
> speculate that XWin was compiled without support for the
> ServerInterpreted address family.

I don't think this speculation is well-founded. :-)

So GDM is doing the equivalent of:

$ xhost +si:localuser:root
$ xhost +si:localuser:gdm

... which fails, I'm guessing for the not entirely unreasonable reason
that 
these users don't exist.

> I cannot find a workround for this.

You might try adding users root and gdm in your cygwin installation
(perhaps 
by adding them to /etc/passwd)

If that works around the problem, I think it's probably a bug in GDM
that it 
fails if these users don't exist.

Even after reading the manpage formerly known as Xsecurity ('man 7
security') 
and the source, I'm really not clear about how this form of credentials
are 
supposed to work, but it seems pretty clear that they can only work
locally.

Note that a server built with NO_LOCAL_CLIENT_CRED (or old enough to
pre-date 
these credentials) will reject all si:localuser and si:localgroup
credentials, 
so it seems GDM should be prepared for it to fail...


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