Vulnerability Discussion

If SSHD is enabled, it must be configured with unused connection timeout set to 900.

This will set the timeout when there are no open channels within a session.

Note: /etc/ssh/sshd_config will be automatically modified to its original state following any update or major upgrade to the operating system.

Satisfies: SRG-OS-000163-GPOS-00072, SRG-OS-000279-GPOS-00109

Check

Verify the macOS system is configured to set the SSHD unused connection timeout to 900 with the following command:

/usr/sbin/sshd -G | /usr/bin/awk '/unusedconnectiontimeout/{print $2}'

If the result is not "900", this is a finding.

Fix

Configure the macOS system to set the SSHD unused connection timeout to 900 with the following command:

include_dir=$(/usr/bin/awk '/^Include/ {print $2}' /etc/ssh/sshd_config | /usr/bin/tr -d '*')

if [[ -z $include_dir ]]; then
/usr/bin/sed -i.bk "1s/.*/Include \/etc\/ssh\/sshd_config.d\/\*/" /etc/ssh/sshd_config
fi

/usr/bin/grep -qxF 'unusedconnectiontimeout 900' "${include_dir}01-mscp-sshd.conf" 2>/dev/null || echo "unusedconnectiontimeout 900" >> "${include_dir}01-mscp-sshd.conf"

for file in $(ls ${include_dir}); do
if [[ "$file" == "100-macos.conf" ]]; then
continue
fi
if [[ "$file" == "01-mscp-sshd.conf" ]]; then
break
fi
/bin/mv ${include_dir}${file} ${include_dir}20-${file}
done