[CentOS] An odd X question

Alexandru Chiscan
2015-06-26T07:16:00Z

Hello Stuart,

On 06/25/2015 11:51 PM, Stuart Barkley wrote:
> For (ssh based) X forwarding no X server needs to run on the server.
> I usually install the xorg-x11-xauth (necessary) and xterm (optional)
> rpms on all my servers in case X forwarding becomes necessary.
>
> Then from your desktop (assuming Linux already running X) in a local
> xterm do something like:
>
>      ssh -Y remote-system
Do not use that because any user logged on the server can connect to your X
server display
and snoop what you are doing, open windows etc.

-Y disables all the X server authentication mechanisms
(http://www.x.org/wiki/Development/Documentation/Security/)
> Note about -X versus -Y with ssh:
>
> -X enables basic X forwarding, It disables some X functionality making
> it "safer" to allow.  -X also stops working after about 20
minutes
> (this is by design but not well documented).  I only recently learned
> why it would stop working after pulling out the last of my hair.
I have been using ssh X forwarding for current work use (local betwork) for more
than 15
years and never got into this kind of problem from RH 7 to Centos 7, AIX and
Solaris.

Maybe it is some other issue that is closing your ssh connection (maybe you
should use the
KeepAlive options on the ssh server/client); just
guessing.
> -Y allows the full X protocol which might be a security risk.  Some
> applications will only work with -Y.  With this, remote X applications
> can grab keyboard interactions, grab passwords, put windows on top of
> other windows (obscuring security messages), etc.
>
> For my own choice I use -Y (although I only enable it occasionally to
> specific systems).

It is a security risk as I said above any user logged on the server can connect
to your
display X server without you knowing.

Lec