`What is the difference between SSH -y` (trusted X11 forwarding) and 'SSH -x` (untrusted X11 forwarding)?

ssh -Y( trusted X11 forward ) and ssh -X( Unbelievable X11 forward ) What's the difference between ？

Both options are related to X11 Forwarding related . This means that if this function is enabled , You can use the SSH The session uses the graphics client ( That is to use Firefox Or others ).

If you use ssh -X remotemachine, Then the remote computer will be regarded as an untrusted client . So your local client sends a command to the remote machine and receives the graphic output . If your command violates some security settings , You will receive an error message .

But if you use ssh -Y remotemachine, Then the remote computer will be regarded as a trusted client . The last option may turn on security issues . Because of other graphics (X11) Clients can sniff data from remote machines ( Make screenshots , Make keyboard records and other annoying things ), You can even change these data .

If you want to know more about these contents , I suggest you read Xsecurity manpage or X Security extension spec. Besides , You can check /etc/ssh/ssh_config Options in ForwardX11 and ForwardX11Trusted.