id: os_ssh_server_alive_interval_configure
title: Configure SSH ServerAliveInterval option set to $ODV
discussion: |
  SSH _MUST_ be configured with an Active Server Alive Maximum Count set to $ODV.

  Setting the Active Server Alive Maximum Count to $ODV will log users out after a $ODV seconds 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.
  
  NOTE: On macOS 15.2 and higher the SSH configuration can be reset to the macOS default by running /usr/libexec/reset-ssh-configuration.
check: |
  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 $ODV")
    if [[ "$sshCheck" == "0" ]]; then
      ret="fail"
      break
    fi
  done
  /bin/echo $ret
result:
  string: pass
fix: |
  [source,bash]
  ----
  include_dir=$(/usr/bin/awk '/^Include/ {print $2}' /etc/ssh/ssh_config | /usr/bin/tr -d '*')
  
  ssh_config_string=("ServerAliveInterval $ODV")
  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
  ---- 
references:
  cce:
    - CCE-95306-7
  cci:
    - CCI-001133
  800-53r5:
    - SC-10
    - AC-12
  800-53r4:
    - SC-10
  srg:
    - SRG-OS-000163-GPOS-00072
  disa_stig:
    - APPL-26-000110
  800-171r3:
    - 03.01.11
    - 03.13.09
  cmmc:
    - AC.L2-3.1.11
    - SC.L2-3.13.9
macOS:
  - '26.0'
odv:
  hint: Number of seconds.
  recommended: 900
  stig: 900
tags:
  - 800-53r5_moderate
  - 800-53r5_high
  - 800-53r4_moderate
  - 800-53r4_high
  - 800-171
  - cnssi-1253_low
  - cnssi-1253_high
  - cmmc_lvl2
  - stig
  - cnssi-1253_moderate
severity: medium
mobileconfig: false
mobileconfig_info:
