Review: My understanding was that this message was due to the lack of an .Xauthority file:
Warning: untrusted X11 forwarding setup failed: xauth key data not generated Trying to generate one with xauth generate $DISPLAY . yielded: xauth: (argv):1: couldn't query Security extension on display ":0" lead me to the discovery that the security extension was not enabled in the server. That's when I wrote the original posting. Then I realized that I could go from one gentoo machine to the other, just not in the other direction. The equery command told me both servers were compiled with the same USE flags. So, I captured the -vvv output from both ssh sessions and I see this: 151,152c161,165 < debug2: client_x11_get_proto: xauth command: /usr/bin/xauth -f /tmp/ssh-xxxxxxxx/xauthfile generate :0 MIT-MAGIC-COOKIE-1 untrusted timeout 1260 2>/dev/null < Warning: untrusted X11 forwarding setup failed: xauth key data not generated --- > debug2: x11_get_proto: /usr/bin/xauth list :0 2>/dev/null > Warning: No xauth data; using fake authentication data for X11 forwarding. > debug1: Requesting X11 forwarding with authentication spoofing. > debug2: channel 0: request x11-req confirm 1 > debug3: send packet: type 98 If I interpret that correctly, one simply failed, and the other used fake security. Someone subsequently mentioned that the -Y flag would generate the .Xauthority file, which I tested and saw that that indeed was true - although, the thusly generated .Xauthority file did *not* allow a subsequent usage with -X. It's not clear to me at this point why I'm configured on the one machine to allow fake security data, but I intend to rebuild the servers with the security extensions enabled. On 12/22/19 22:17, n952162 wrote:
xauth(1) says: /if [the X server] does not support the SECURITY extension, the [generate] command fails./ The xauth command is used to generate the .Xauthority file, which is required for X11Forwarding. But the Security Extension is not enabled by default: - - xcsecurity : Build Security extension but I don't find anybody asking why X11 forwarding doesn't work under gentoo. What am I missing?