Disable X11 Forwarding for SSH

MediumLevel 1Automatedsolaris

Description

The X11 Forwarding parameter defined within the /etc/ssh/sshd_config file specifies whether or not X11 Forwarding via SSH is enabled on the server: The Secure Shell service provides an encrypted 'tunnel' for the data traffic passing through it. As enabling X11Forwarding on the host can permit a malicious user to secretly open another X11 connection to another remote client during the session and perform unobtrusive activities such as keystroke monitoring, if the X11 services are not required for ... Audit: pattern match on /etc/ssh/sshd_config as described in the CIS audit procedure.

How it is checked

Audit method: File pattern

File: /etc/ssh/sshd_config
Pattern: (?m)^X11Forwarding\s+no\b

How it is fixed

Fix method: Guidance or infrastructure patch

Perform the following to implement the recommended state: # cp /etc/ssh/sshd_config /etc/ssh/sshd_config.orig # awk '/^X11Forwarding / { $2 = "no" } { print }' /etc/ssh/sshd_config > /etc/ssh/sshd_config.CIS # mv /etc/ssh/sshd_config.CIS /etc/ssh/sshd_config # svcadm restart svc:/network/ssh

Properties

Operating systems: Any
Tags: solarisssh
Reference: CIS Oracle Solaris 11.4 Benchmark v1.1.0 - 6.13 Disable X11 Forwarding for SSH

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target solaris