The macOS system must configure SSH ServerAliveInterval option set to 900.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-259445	SRG-OS-000163-GPOS-00072	APPL-14-000110	SV-259445r970703_rule	2024-12-04	2

Description
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.

ℹ️ Check
Verify the macOS system is configured to set the SSH ServerAliveInterval option set 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.

ℹ️ Check

Verify the macOS system is configured to set the SSH ServerAliveInterval option set 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
Configure the macOS system to set the SSH ServerAliveInterval option set to 900 with the following command: for u in $(/usr/bin/dscl . -list /Users UniqueID \| /usr/bin/awk '$2 > 500 {print $1}'); do config=$(/usr/bin/sudo -u $u /usr/bin/ssh -Gv . 2>&1 \| /usr/bin/awk '/Reading configuration data/ {print $NF}'\| /usr/bin/tr -d '\r') configarray=( ${(f)config} ) for c in $configarray; do /usr/bin/sudo -u $u /usr/bin/grep -q '^ServerAliveInterval' "$c" && /usr/bin/sed -i '' 's/.ServerAliveInterval./ServerAliveInterval 900/' "$c" \|\| /bin/echo 'ServerAliveInterval 900' >> "$c" done done

✔️ Fix

Configure the macOS system to set the SSH ServerAliveInterval option set to 900 with the following command: for u in $(/usr/bin/dscl . -list /Users UniqueID | /usr/bin/awk '$2 > 500 {print $1}'); do config=$(/usr/bin/sudo -u $u /usr/bin/ssh -Gv . 2>&1 | /usr/bin/awk '/Reading configuration data/ {print $NF}'| /usr/bin/tr -d '\r') configarray=( ${(f)config} ) for c in $configarray; do /usr/bin/sudo -u $u /usr/bin/grep -q '^ServerAliveInterval' "$c" && /usr/bin/sed -i '' 's/.*ServerAliveInterval.*/ServerAliveInterval 900/' "$c" || /bin/echo 'ServerAliveInterval 900' >> "$c" done done