The macOS system must configure the SSH ServerAliveInterval to 900.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-268444 | APPL-15-000110 | SV-268444r1034800_rule | CCI-001133 | medium |
| 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. | ||||
| STIG | Date | |||
| Apple macOS 15 (Sequoia) Security Technical Implementation Guide | 2025-05-05 | |||
Details
Check Text (C-268444r1034800_chk)
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 $ret
If the result is not "pass", this is a finding.
Fix Text (F-72375r1034799_fix)
Configure the macOS system to set the SSH ServerAliveInterval to 900 with the following command:
include_dir=$(/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