Title

The macOS system must configure the SSH ServerAliveInterval to 900. (Cat II impact)

Discussion

SSH must be configured with an Active Server Alive Maximum Count set to 900. Setting the Active Server Alive Maximum Count to 900 will log users out after a 900-second interval of inactivity. NOTE: /etc/ssh/ssh_config will be automatically modified to its original state following any update or major upgrade to the operating system.

Check Content

Verify the macOS system is configured to set the SSH ServerAliveInterval to 900 with the following command: ret="pass" for u in $(/usr/bin/dscl . -list /Users UniqueID | /usr/bin/awk '$2 > 500 {print $1}'); do sshCheck=$(/usr/bin/sudo -u $u /usr/bin/ssh -G . | /usr/bin/grep -c "^serveraliveinterval 900") if [[ "$sshCheck" == "0" ]]; then ret="fail" break fi done /bin/echo $ret If the result is not "pass", this is a finding.

Fix Text

Configure the macOS system to set the SSH ServerAliveInterval to 900 with the following command: include_dir=$(/usr/bin/awk '/^Include/ {print $2}' /etc/ssh/ssh_config | /usr/bin/tr -d '*') ssh_config_string=("ServerAliveInterval 900") for ssh_config in $ssh_config_string; do ssh_setting=$(echo $ssh_config | /usr/bin/cut -d " " -f1) /usr/bin/grep -qEi "^$ssh_setting" "${include_dir}01-mscp-ssh.conf" && /usr/bin/sed -i "" "s/^$ssh_setting.*/${ssh_config}/" "${include_dir}01-mscp-ssh.conf" || echo "$ssh_config" >> "${include_dir}01-mscp-ssh.conf" for u in $(/usr/bin/dscl . list /users shell | /usr/bin/egrep -v '(^_)|(root)|(/usr/bin/false)' | /usr/bin/awk '{print $1}'); do config=$(/usr/bin/sudo -u $u /usr/bin/ssh -Gv . 2>&1) configfiles=$(echo "$config" | /usr/bin/awk '/Reading configuration data/ {print $NF}'| /usr/bin/tr -d '\r') configarray=( ${(f)configfiles} ) if ! echo $config | /usr/bin/grep -q -i "$ssh_config" ; then for c in $configarray; do if [[ "$c" == "/etc/ssh/crypto.conf" ]]; then continue fi /usr/bin/sudo -u $u /usr/bin/grep -qEi "^$ssh_setting" "$c" && /usr/bin/sed -i "" "s/^$ssh_setting.*/${ssh_config}/I" "$c" if [[ "$c" =~ ".ssh/config" ]]; then if /usr/bin/grep -qEi "$ssh_setting" "$c" 2> /dev/null; then old_file=$(cat ~$u/.ssh/config) echo "$ssh_config" > ~$u/.ssh/config echo "$old_file" >> ~$u/.ssh/config fi fi done fi done done

Additional Identifiers

Rule ID: SV-268444r1034800_rule

Vulnerability ID: V-268444

Group Title: SRG-OS-000163-GPOS-00072

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