Warning: No xauth data; using fake authentication data for X11 forwarding. (Doc ID 464257.1)

Last updated on JUNE 21, 2009

Applies to:

Linux Kernel - Version: 4.0 to 5.0
Linux x86-64
Checked for relevance on 22-Jun-2009

Symptoms

Using ssh with -X or -Y option, ssh prints "Warning: No xauth data; using fake authentication data for X11 forwarding."

From man ssh
     -X      Enables X11 forwarding.  This can also be specified on a per-host basis
             in a configuration file.

             X11 forwarding should be enabled with caution.  Users with the ability
             to bypass file permissions on the remote host (for the user's X autho-
             rization database) can access the local X11 display through the for-
             warded connection.  An attacker may then be able to perform activities
             such as keystroke monitoring.

             For this reason, X11 forwarding is subjected to X11 SECURITY extension
             restrictions by default.  Please refer to the ssh -Y option and the
             ForwardX11Trusted directive in ssh_config(5) for more information.

     -Y      Enables trusted X11 forwarding.  Trusted X11 forwardings are not sub-
             jected to the X11 SECURITY extension controls.

Cause

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