gsmartcontrol, gparted problems with userhelper and X credentials?

[Adam Jackson]

On 12/23/11 5:14 AM, Eric Smith wrote:
> I wrote:
>  > Now if I try to launch gsmartcontrol from the Gnome Shell, I get
>  > the prompt from userhelper for my password, but it fails to run.
>  > From the command line, the same thing happens, but at least it
>  > shows the error message "Gtk-WARNING **: cannot open display: :0".
>
> I withdraw the question. After rebooting the system, gsmartcontrol and
> gparted both work fine. I'm not sure what went wrong before.

I am.

You moved between networks, which caused your hostname to change [1]. 
This meant that the xauth cookie for your current session no longer 
matched, because it embeds the hostname, because the spec says that's 
what you do.

We set up X with two levels of authentication.  The second is the 
traditional xauth cookie mechanism, but the first matches against UID 
instead [2]:

% DISPLAY=:0 xhost
access control enabled, only authorized clients can connect
SI:localuser:ajax

So this keeps normal users from being affected when the hostname 
changes.  But once you've switched UID you fall back to the xauth cookie 
and things break.

I wrote a patch for this once:

https://bugzilla.redhat.com/show_bug.cgi?id=679486#c43

And it got no conclusive testing or whatever, I forget.  The patch 
itself is in package git, although not enabled in the libXau build:

http://pkgs.fedoraproject.org/gitweb/?p=libXau.git;a=commitdiff;h=bdfc287eca3dfeaf457d7607763beae782f0004b

If someone wanted to test it, that'd rule.

[1] - This is debateably correct.

[2] - The real reason we do this is because it eliminates the security 
issues if your ~ is on NFS, and because it keeps you from needing to 
touch (ie, wake up) the disk in the common case.

- ajax