LightDM - Oct 2015 - Magic cookie doesn't work - no protocol specified

When I start an X-session via startx on my debian distro, I can get the
output of the two following commands:

$ xauth extract - $DISPLAY
morfikownia0MIT-MAGIC-COOKIE-1’E!ö½o`q!SD„%

$ xauth extract - morfikownia.mhouse.lh:0.0
À¨–0MIT-MAGIC-COOKIE-1­Ê¹2y0ºˆ%

I know that the output is a little unreadable, but the most important
thing is that I get the output from the two commands above. When I send
that cookie to another machine using this command:

$ xauth extract - morfikownia.mhouse.lh:0.0 | ssh -x morfik at 192.168.10.20
xauth merge -

I can get access to this X-server from that machine, and everything works
as expected.

When I start am X-session via LightDM, the command:

xauth extract - morfikownia.mhouse.lh:0.0

returns nothing, or actually it gives me the following message:

"No matches found, authority file "-" not written"

I can, of course, use the following command to get the cookie:

xauth extract - $DISPLAY

and then send it via:

$ xauth extract - $DISPLAY | ssh -x morfik at 192.168.10.20 xauth merge -

But in that case, when I try to connect remotely to this X-server, I'm
unable to do it. I get a message that "no protocol specified", and
nothing happens.

I think I have the exact same options set in both cases, i.e. in the
/etc/X11/xinit/xserverrc file I have the following line:

exec /usr/bin/X -auth "$HOME/.Xauthority" -listen tcp "$@"

And in the case of LightDM I have these options set in its config file
(/etc/lightdm/lightdm.conf):

egrep -v ^# /etc/lightdm/lightdm.conf
[LightDM]
greeter-user=lightdm
minimum-display-number=0
minimum-vt=7
logind-check-graphical=true
log-directory=/var/log/lightdm
run-directory=/var/run/lightdm
cache-directory=/var/cache/lightdm

[Seat:*]
xserver-command=X -listen tcp -auth "$HOME/.Xauthority"
xserver-allow-tcp=true
greeter-session=lightdm-gtk-greeter
greeter-hide-users=false
greeter-allow-guest=false
greeter-show-manual-login=true
greeter-show-remote-login=true
user-session=openbox
allow-user-switching=true
allow-guest=false
autologin-guest=false
autologin-user-timeout=0
autologin-in-background=false

[XDMCPServer]

[VNCServer]

Do you know why it fails to connect to the X-server when LightDM is used? Is
there a way to fix it?

Hi Mikhail,

It's hard to tell exactly what is wrong - if you attach both .Xauthority
files it will be easier to see the difference.

Check what version of Xorg you are running and check it is actually
enabling TCP connections - there was a behaviour change in X [1].

--Robert

[1] https://launchpad.net/bugs/1449282


On Fri, 30 Oct 2015 at 16:45 Mikhail Morfikov <mmorfikov at gmail.com>
wrote:
> When I start an X-session via startx on my debian distro, I can get the
> output of the two following commands:
>
> $ xauth extract - $DISPLAY
> morfikownia0MIT-MAGIC-COOKIE-1’E!ö½o`q!SD„%
>
> $ xauth extract - morfikownia.mhouse.lh:0.0
> À¨–0MIT-MAGIC-COOKIE-1­Ê¹2y0ºˆ%
>
> I know that the output is a little unreadable, but the most important
> thing is that I get the output from the two commands above. When I send
> that cookie to another machine using this command:
>
> $ xauth extract - morfikownia.mhouse.lh:0.0 | ssh -x morfik at
192.168.10.20
> xauth merge -
>
> I can get access to this X-server from that machine, and everything works
> as expected.
>
> When I start am X-session via LightDM, the command:
>
> xauth extract - morfikownia.mhouse.lh:0.0
>
> returns nothing, or actually it gives me the following message:
>
> "No matches found, authority file "-" not written"
>
> I can, of course, use the following command to get the cookie:
>
> xauth extract - $DISPLAY
>
> and then send it via:
>
> $ xauth extract - $DISPLAY | ssh -x morfik at 192.168.10.20 xauth merge -
>
> But in that case, when I try to connect remotely to this X-server, I'm
> unable to do it. I get a message that "no protocol specified",
and nothing
> happens.
>
> I think I have the exact same options set in both cases, i.e. in the
> /etc/X11/xinit/xserverrc file I have the following line:
>
> exec /usr/bin/X -auth "$HOME/.Xauthority" -listen tcp
"$@"
>
> And in the case of LightDM I have these options set in its config file
> (/etc/lightdm/lightdm.conf):
>
> egrep -v ^# /etc/lightdm/lightdm.conf
> [LightDM]
> greeter-user=lightdm
> minimum-display-number=0
> minimum-vt=7
> logind-check-graphical=true
> log-directory=/var/log/lightdm
> run-directory=/var/run/lightdm
> cache-directory=/var/cache/lightdm
>
> [Seat:*]
> xserver-command=X -listen tcp -auth "$HOME/.Xauthority"
> xserver-allow-tcp=true
> greeter-session=lightdm-gtk-greeter
> greeter-hide-users=false
> greeter-allow-guest=false
> greeter-show-manual-login=true
> greeter-show-remote-login=true
> user-session=openbox
> allow-user-switching=true
> allow-guest=false
> autologin-guest=false
> autologin-user-timeout=0
> autologin-in-background=false
>
> [XDMCPServer]
>
> [VNCServer]
>
> Do you know why it fails to connect to the X-server when LightDM is used?
> Is there a way to fix it?
> _______________________________________________
> LightDM mailing list
> LightDM at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/lightdm
>
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