The SSH daemon ClientAliveCountMax option must be set correctly.

From Apple OS X 10.10 (Yosemite) Workstation Security Technical Implementation Guide

Associated with: CCI-001133

SV-74115r1_rule The SSH daemon ClientAliveCountMax option must be set correctly.

Vulnerability discussion

SSH should be configured to log users out after a 15 minute interval of inactivity and to only wait 30 seconds before timing out login attempts. Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition, quickly terminating an idle session or an incomplete login attempt will also free up resources committed by the managed network element.

Check content

The SSH daemon ClientAliveCountMax option must be set correctly. To ensure the SSH idle timeout will occur when the 'ClientAliveCountMax' is set, run the following command: sudo grep ^ClientAliveCountMax /etc/sshd_config If the setting is not 'ClientAliveCountMax 0', this is a finding.

Fix text

In order to make sure that the SSH idle timeout occurs precisely when the 'ClientAliveCountMax' is set, run the following command: sudo sed -i.bak 's/.*ClientAliveCountMax.*/ClientAliveCountMax 0/' /etc/sshd_config

Pro Tips

Lavender hyperlinks in small type off to the right (of CSS class id, if you view the page source) point to globally unique URIs for each document and item. Copy the link location and paste anywhere you need to talk unambiguously about these things.

You can obtain data about documents and items in other formats. Simply provide an HTTP header Accept: text/turtle or Accept: application/rdf+xml.