The macOS system must be configured with the SSH daemon LoginGraceTime set to 30 or less.

From Apple OS X 10.13 Security Technical Implementation Guide

Associated with: CCI-001133

SV-96369r1_rule The macOS system must be configured with the SSH daemon LoginGraceTime set to 30 or less.

Vulnerability discussion

SSH should be configured to log users out after a 15-minute interval of inactivity and to wait only 30 seconds before timing out logon 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 logon attempt will also free up resources committed by the managed network element.

Check content

The SSH daemon "LoginGraceTime" must be set correctly. To check the amount of time that a user can log on through SSH, run the following command: /usr/bin/sudo /usr/bin/grep ^LoginGraceTime /etc/ssh/sshd_config If the value is not set to "30" or less, this is a finding.

Fix text

To ensure that "LoginGraceTime" is configured correctly, run the following command: /usr/bin/sudo /usr/bin/sed -i.bak 's/.*LoginGraceTime.*/LoginGraceTime 30/' /etc/ssh/sshd_config

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