Image Builder 的安全最佳實務

Image Builder 管道會執行清除指令碼，以協助確保最終映像遵循安全最佳實務，並移除任何不應傳遞至快照的建置成品或設定。不過，您可以略過指令碼的區段，或完全覆寫使用者資料。因此，Image Builder 管道產生的映像不一定符合任何特定的法規條件。

當管道完成建置和測試階段時，Image Builder 會在建立輸出映像之前自動執行下列清除指令碼。

檔案清除完成後，Image Builder 會將步驟附加至解除安裝 Systems Manager 代理程式並移除cronie套件的指令碼。Image Builder 會追蹤服務/tmp/imagebuilder_service工作目錄中建置期間安裝的項目。Image Builder 使用這些標記來決定要移除的內容：

#!/bin/bash
if [[ ! -f {{workingDirectory}}/perform_cleanup ]]; then
    echo "Skipping cleanup"
    exit 0
else
    sudo rm -f {{workingDirectory}}/perform_cleanup
fi

function cleanup() {
    FILES=("$@")
    for FILE in "${FILES[@]}"; do
        if [[ -f "$FILE" ]]; then
            echo "Deleting $FILE";
            sudo shred -zuf $FILE;
        fi;
        if [[ -f $FILE ]]; then
            echo "Failed to delete '$FILE'. Failing."
            exit 1
        fi;
    done
};


# Clean up for cloud-init files
CLOUD_INIT_FILES=(
    "/etc/sudoers.d/90-cloud-init-users"
    "/etc/locale.conf"
    "/var/log/cloud-init.log"
    "/var/log/cloud-init-output.log"
)
if [[ -f {{workingDirectory}}/skip_cleanup_cloudinit_files ]]; then
    echo "Skipping cleanup of cloud init files"
else
    echo "Cleaning up cloud init files"
    cleanup "${CLOUD_INIT_FILES[@]}"
    if [[ -d "/var/lib/cloud" ]]; then
        if [[ $( sudo find /var/lib/cloud -type f | sudo wc -l ) -gt 0 ]]; then
            echo "Deleting files within /var/lib/cloud/*"
            sudo find /var/lib/cloud -type f -exec shred -zuf {} \;
        fi;

        if [[ $( sudo ls /var/lib/cloud | sudo wc -l ) -gt 0 ]]; then
            echo "Deleting /var/lib/cloud/*"
            sudo rm -rf /var/lib/cloud/* || true
        fi;
    fi;
fi;


# Clean up for temporary instance files
INSTANCE_FILES=(
    "/etc/.updated"
    "/etc/aliases.db"
    "/etc/hostname"
    "/var/lib/misc/postfix.aliasesdb-stamp"
    "/var/lib/postfix/master.lock"
    "/var/spool/postfix/pid/master.pid"
    "/var/.updated"
    "/var/cache/yum/x86_64/2/.gpgkeyschecked.yum"
)
if [[ -f {{workingDirectory}}/skip_cleanup_instance_files ]]; then
    echo "Skipping cleanup of instance files"
else
    echo "Cleaning up instance files"
    cleanup "${INSTANCE_FILES[@]}"
fi;


# Clean up for ssh files
SSH_FILES=(
    "/etc/ssh/ssh_host_rsa_key"
    "/etc/ssh/ssh_host_rsa_key.pub"
    "/etc/ssh/ssh_host_ecdsa_key"
    "/etc/ssh/ssh_host_ecdsa_key.pub"
    "/etc/ssh/ssh_host_ed25519_key"
    "/etc/ssh/ssh_host_ed25519_key.pub"
    "/root/.ssh/authorized_keys"
)
if [[ -f {{workingDirectory}}/skip_cleanup_ssh_files ]]; then
    echo "Skipping cleanup of ssh files"
else
    echo "Cleaning up ssh files"
    cleanup "${SSH_FILES[@]}"
    USERS=$(ls /home/)
    for user in $USERS; do
        echo Deleting /home/"$user"/.ssh/authorized_keys;
        sudo find /home/"$user"/.ssh/authorized_keys -type f -exec shred -zuf {} \;
    done
    for user in $USERS; do
        if [[ -f /home/"$user"/.ssh/authorized_keys ]]; then
            echo Failed to delete /home/"$user"/.ssh/authorized_keys;
            exit 1
        fi;
    done;
fi;


# Clean up for instance log files
INSTANCE_LOG_FILES=(
    "/var/log/audit/audit.log"
    "/var/log/boot.log"
    "/var/log/dmesg"
    "/var/log/cron"
)
if [[ -f {{workingDirectory}}/skip_cleanup_instance_log_files ]]; then
    echo "Skipping cleanup of instance log files"
else
    echo "Cleaning up instance log files"
    cleanup "${INSTANCE_LOG_FILES[@]}"
fi;

# Clean up for TOE files
if [[ -f {{workingDirectory}}/skip_cleanup_toe_files ]]; then
    echo "Skipping cleanup of TOE files"
else
    echo "Cleaning TOE files"
    shopt -s nullglob
    TOE_MATCHES=({{workingDirectory}}/TOE_*)
    shopt -u nullglob
    if [[ ${#TOE_MATCHES[@]} -gt 0 ]]; then
        if [[ $( sudo find "${TOE_MATCHES[@]}" -type f | sudo wc -l) -gt 0 ]]; then
            echo "Deleting files within {{workingDirectory}}/TOE_*"
            sudo find "${TOE_MATCHES[@]}" -type f -exec shred -zuf {} \;
        fi
        shopt -s nullglob
        TOE_REMAINING=({{workingDirectory}}/TOE_*)
        shopt -u nullglob
        if [[ ${#TOE_REMAINING[@]} -gt 0 ]]; then
            if [[ $( sudo find "${TOE_REMAINING[@]}" -type f | sudo wc -l) -gt 0 ]]; then
                echo "Failed to delete {{workingDirectory}}/TOE_*"
                exit 1
            fi
            echo "Deleting {{workingDirectory}}/TOE_*"
            sudo rm -rf "${TOE_REMAINING[@]}"
        fi
        shopt -s nullglob
        TOE_FINAL=({{workingDirectory}}/TOE_*)
        shopt -u nullglob
        if [[ ${#TOE_FINAL[@]} -gt 0 ]]; then
            echo "Failed to delete {{workingDirectory}}/TOE_*"
            exit 1
        fi
    fi
fi

# Clean up for ssm log files
if [[ -f {{workingDirectory}}/skip_cleanup_ssm_log_files ]]; then
    echo "Skipping cleanup of ssm log files"
else
    echo "Cleaning up ssm log files"
    if [[ -d "/var/log/amazon/ssm" ]]; then
        if [[ $( sudo find /var/log/amazon/ssm -type f | sudo wc -l) -gt 0 ]]; then
            echo "Deleting files within /var/log/amazon/ssm/*"
            sudo find /var/log/amazon/ssm -type f -exec shred -zuf {} \;
        fi
        if [[ $( sudo find /var/log/amazon/ssm -type f | sudo wc -l) -gt 0 ]]; then
            echo "Failed to delete /var/log/amazon/ssm"
            exit 1
        fi
        echo "Deleting /var/log/amazon/ssm/*"
        sudo rm -rf /var/log/amazon/ssm
        if [[ -d "/var/log/amazon/ssm" ]]; then
            echo "Failed to delete /var/log/amazon/ssm"
            exit 1
        fi
    fi
fi


shopt -s nullglob
SA_MATCHES=(/var/log/sa/sa*)
shopt -u nullglob
if [[ ${#SA_MATCHES[@]} -gt 0 ]]; then
    echo "Deleting /var/log/sa/sa*"
    sudo shred -zuf "${SA_MATCHES[@]}"
    shopt -s nullglob
    SA_REMAINING=(/var/log/sa/sa*)
    shopt -u nullglob
    if [[ ${#SA_REMAINING[@]} -gt 0 ]]; then
        echo "Failed to delete /var/log/sa/sa*"
        exit 1
    fi
fi

shopt -s nullglob
DHCLIENT_MATCHES=(/var/lib/dhclient/dhclient*.lease)
shopt -u nullglob
if [[ ${#DHCLIENT_MATCHES[@]} -gt 0 ]]; then
    echo "Deleting /var/lib/dhclient/dhclient*.lease"
    sudo shred -zuf "${DHCLIENT_MATCHES[@]}"
    shopt -s nullglob
    DHCLIENT_REMAINING=(/var/lib/dhclient/dhclient*.lease)
    shopt -u nullglob
    if [[ ${#DHCLIENT_REMAINING[@]} -gt 0 ]]; then
        echo "Failed to delete /var/lib/dhclient/dhclient*.lease"
        exit 1
    fi
fi

if [[ $( sudo find /var/tmp -type f | sudo wc -l) -gt 0 ]]; then
    echo "Deleting files within /var/tmp/*"
    sudo find /var/tmp -type f -exec shred -zuf {} \;
fi
if [[ $( sudo find /var/tmp -type f | sudo wc -l) -gt 0 ]]; then
    echo "Failed to delete /var/tmp"
    exit 1
fi
if [[ $( sudo ls /var/tmp | sudo wc -l ) -gt 0 ]]; then
    echo "Deleting /var/tmp/*"
    sudo rm -rf /var/tmp/*
fi

if [[ -f "/var/lib/systemd/random-seed" ]]; then
    echo "Deleting /var/lib/systemd/random-seed"
    sudo shred -zuf /var/lib/systemd/random-seed
    sudo rm -f /var/lib/systemd/random-seed
fi

# Shredding is not guaranteed to work well on rolling logs

if [[ -f "/var/lib/rsyslog/imjournal.state" ]]; then
    echo "Deleting /var/lib/rsyslog/imjournal.state"
    sudo shred -zuf /var/lib/rsyslog/imjournal.state
    sudo rm -f /var/lib/rsyslog/imjournal.state
fi

if [[ -d "/var/log/journal" ]] && [[ $( sudo ls /var/log/journal/ | sudo wc -l ) -gt 0 ]]; then
    echo "Deleting /var/log/journal/*"
    sudo find /var/log/journal/ -type f -exec shred -zuf {} \;
    sudo rm -rf /var/log/journal/*
fi

if [[ -f "/etc/machine-id" ]]; then
    echo "Truncating /etc/machine-id"
    sudo truncate -s 0 /etc/machine-id
fi

if [[ -f "/var/lib/dbus/machine-id" ]]; then
    echo "Truncating /var/lib/dbus/machine-id"
    sudo truncate -s 0 /var/lib/dbus/machine-id
fi

sudo touch /etc/machine-id

# Flush all pending writes to disk before instance shutdown and snapshot
sync

echo "Sanitize OK"


###############################################################################
# Image Builder appends the following steps to the clean up script to uninstall
# the Systems Manager (SSM) agent and, on Amazon Linux 1, Amazon Linux 2, and
# Amazon Linux 2023, to remove the cronie package when Image Builder installed a
# crontab during the build. Image Builder uses the /tmp/imagebuilder_service
# working directory to track what it installed.
###############################################################################

SERVICE_ROOT_WORKING_DIR="/tmp/imagebuilder_service"

# SSM_UNINSTALL_CONDITION reflects the systemsManagerAgent.uninstallAfterBuild
# recipe setting and how the SSM agent was installed:
#   SSM_INSTALLED_BY_CUSTOMER      - always uninstall the SSM agent
#   SSM_INSTALLED_BY_IMAGE_BUILDER - uninstall only if Image Builder installed it
#   (any other value)              - leave the SSM agent in the final image
SSM_UNINSTALL_CONDITION="<uninstallAfterBuild condition>"

function error_exit {
  echo "$1" 1>&2
  exit 1
}

function ssm_exists() {
  eval "$1"  > /dev/null 2>&1
  echo $?
}

function cleanup_image() {
  rm -rf "${SERVICE_ROOT_WORKING_DIR}"
}

function uninstall_ssm_agent() {

  uninstall_package="$1"
  uninstall_all=""
  uninstall_success="false"

  if [ "${uninstall_package}" == "" ]; then
    uninstall_all="true"
  fi

  yum="sudo yum search amazon-ssm-agent | grep amazon-ssm-agent"
  snap="sudo snap list amazon-ssm-agent"
  rpm="sudo rpm -qa amazon-ssm-agent | grep amazon-ssm-agent"
  dpkg="sudo dpkg --get-selections | grep amazon-ssm-agent"
  pkg="su -m root -c \"pkg info -l amazon-ssm-agent | grep amazon-ssm-agent\""


  if [[ ("${uninstall_all}" == "true" || "${uninstall_package}" == "snap") && $(ssm_exists "${snap}") -eq 0 ]]; then
    echo "Package found in Snap.... Uninstalling"
    (sleep 30 ; sudo snap remove amazon-ssm-agent) &>/dev/null &
    uninstall_success="true"
  fi

  if [[ ("${uninstall_all}" == "true" || "${uninstall_package}" == "yum") && $(ssm_exists "${yum}") -eq 0 ]]; then
    echo "Package found in Yum.... Uninstalling"
    (sleep 30 ; sudo yum remove -y amazon-ssm-agent) &>/dev/null &
    uninstall_success="true"
  fi

  if [[ ("${uninstall_all}" == "true" || "${uninstall_package}" == "rpm") && $(ssm_exists "${rpm}") -eq 0 ]]; then
    echo "Package found in Rpm.... Uninstalling"
    (sleep 30 ; sudo rpm -e amazon-ssm-agent) &>/dev/null &
    uninstall_success="true"
  fi

  if [[ ("${uninstall_all}" == "true" || "${uninstall_package}" == "dpkg") && $(ssm_exists "${dpkg}") -eq 0 ]]; then
    echo "Package found in Dpkg.... Uninstalling"
    (sleep 30 ; sudo dpkg -r --force-all amazon-ssm-agent) &>/dev/null &
    uninstall_success="true"
  fi

  if [[ ("${uninstall_all}" == "true" || "${uninstall_package}" == "pkg") && $(ssm_exists "${pkg}") -eq 0 ]]; then
    echo "Package found in FreeBSD.... Uninstalling"
    (sleep 30 ; su -m root -c "pkg remove -y amazon-ssm-agent") &> /dev/null &
    uninstall_success="true"
  fi

  if [ "${uninstall_success}" == "false" ] ; then
    error_exit "Unable to uninstall an SSM agent"
  fi
}

# Amazon Linux releases where Image Builder installs cronie to provide a crontab:
# Amazon Linux AMI (AL1), AL2, and AL2023.
function is_cronie_supported_amazon_linux() {
    if [ "$(get_os_type)" != "amzn" ]; then
        return 1
    fi
    case "$(get_os_version)" in
        2|2023) return 0 ;;
        # AL1 releases use date-based versions from 2010 through 2018.
        201[0-8].[0-9][0-9]) return 0 ;;
        *) return 1 ;;
    esac
}

function uninstall_crontab() {
    if is_cronie_supported_amazon_linux ; then
        echo "Uninstalling cronie package"
        sudo yum remove -y cronie
    fi
}

function get_os_type() {
    FILE=/etc/os-release
    if [ -e $FILE ]; then
        . $FILE
        echo $ID
    else
        echo ""
    fi
}

function get_os_version() {
    FILE=/etc/os-release
    if [ -e $FILE ]; then
        . $FILE
        echo $VERSION_ID
    else
        echo ""
    fi
}

if [ "${SSM_UNINSTALL_CONDITION}" == "SSM_INSTALLED_BY_CUSTOMER" ] ; then
  echo "Uninstall after build set to true. Uninstalling SSM agent."
  uninstall_ssm_agent

elif [ "${SSM_UNINSTALL_CONDITION}" == "SSM_INSTALLED_BY_IMAGE_BUILDER" ] ; then
  echo "Checking if the SSM agent was installed by Image Builder"
  if [[ -f ${SERVICE_ROOT_WORKING_DIR}/ssm_installed ]] ; then
    package_manager="$(cat ${SERVICE_ROOT_WORKING_DIR}/ssm_installed)"
    echo "Uninstalling the SSM agent installed by Image Builder using ${package_manager}"
    uninstall_ssm_agent "${package_manager}"
  fi
else
  echo "Uninstall after build set to false. Skipping SSM agent uninstall."
fi

# When Image Builder installs a crontab during the build (on Amazon Linux 1,
# Amazon Linux 2, or Amazon Linux 2023), it records a crontab_installed marker
# and removes the cronie package here. To keep cronie in your final image,
# delete the marker before clean up runs:
#   rm -f /tmp/imagebuilder_service/crontab_installed
if [[ -f ${SERVICE_ROOT_WORKING_DIR}/crontab_installed ]] ; then
  echo "Uninstalling crontab installed by Image Builder"
  uninstall_crontab
fi

cleanup_image

在映像建置器管道自訂 Windows 映像之後，它會執行 Microsoft Sysprep 公用程式。這些動作遵循AWS 強化和清理映像的最佳實務。

Image Builder 管道會執行清除指令碼，以協助確保最終映像遵循安全最佳實務，並移除任何不應傳遞至快照的建置成品或設定。不過，您可以略過指令碼的區段，或完全覆寫使用者資料。因此，Image Builder 管道產生的映像不一定符合任何特定的法規條件。

當管道完成建置和測試階段時，Image Builder 會在建立輸出映像之前自動執行下列清除指令碼。

#!/bin/bash
if [[ ! -f {{workingDirectory}}/perform_cleanup ]]; then
  echo "Skipping cleanup"
  exit 0
else
  sudo rm -f {{workingDirectory}}/perform_cleanup
fi

function cleanup() {
  FILES=("$@")
  for FILE in "${FILES[@]}"; do
      if [[ -f "$FILE" ]]; then
          echo "Deleting $FILE";
          sudo rm -f $FILE;
      fi;
      if [[ -f $FILE ]]; then
          echo "Failed to delete '$FILE'. Failing."
          exit 1
      fi;
  done
};

# Reset EC2 macOS Init instance history so the image behaves as a first boot
if [[ -f {{workingDirectory}}/skip_cleanup_ec2_macos_init_files ]]; then
  echo "Skipping cleanup of ec2-macos-init instance history"
else
  echo "Cleaning up ec2-macos-init instance history"
  if [[ -x /usr/local/bin/ec2-macos-init ]]; then
      sudo /usr/local/bin/ec2-macos-init clean -all
  fi
fi

# Clean up for temporary instance files
INSTANCE_FILES=(
  "/Library/Preferences/SystemConfiguration/NetworkInterfaces.plist"
)
if [[ -f {{workingDirectory}}/skip_cleanup_instance_files ]]; then
  echo "Skipping cleanup of instance files"
else
  echo "Cleaning up instance files"
  cleanup "${INSTANCE_FILES[@]}"
fi;


# Clean up for ssh files
SSH_FILES=(
  "/etc/ssh/ssh_host_rsa_key"
  "/etc/ssh/ssh_host_rsa_key.pub"
  "/etc/ssh/ssh_host_ecdsa_key"
  "/etc/ssh/ssh_host_ecdsa_key.pub"
  "/etc/ssh/ssh_host_ed25519_key"
  "/etc/ssh/ssh_host_ed25519_key.pub"
  "/var/root/.ssh/authorized_keys"
)
if [[ -f {{workingDirectory}}/skip_cleanup_ssh_files ]]; then
  echo "Skipping cleanup of ssh files"
else
  echo "Cleaning up ssh files"
  cleanup "${SSH_FILES[@]}"
  USERS=$(ls /Users/)
  for user in $USERS; do
      if [[ -f /Users/"$user"/.ssh/authorized_keys ]]; then
          echo Deleting /Users/"$user"/.ssh/authorized_keys;
          sudo rm -f /Users/"$user"/.ssh/authorized_keys;
      fi;
  done
  for user in $USERS; do
      if [[ -f /Users/"$user"/.ssh/authorized_keys ]]; then
          echo Failed to delete /Users/"$user"/.ssh/authorized_keys;
          exit 1
      fi;
  done;
fi;


# Clean up for instance log files
INSTANCE_LOG_FILES=(
  "/var/log/amazon/ec2/ec2-macos-init.log"
  "/var/log/amazon/ec2/ena-ethernet.log"
  "/var/log/amazon/ec2/system-monitoring.log"
)
if [[ -f {{workingDirectory}}/skip_cleanup_instance_log_files ]]; then
  echo "Skipping cleanup of instance log files"
else
  echo "Cleaning up instance log files"
  cleanup "${INSTANCE_LOG_FILES[@]}"
fi;

# Clean up for TOE files
if [[ -f {{workingDirectory}}/skip_cleanup_toe_files ]]; then
  echo "Skipping cleanup of TOE files"
else
  echo "Cleaning TOE files"
  shopt -s nullglob
  TOE_MATCHES=({{workingDirectory}}/TOE_*)
  shopt -u nullglob
  if [[ ${#TOE_MATCHES[@]} -gt 0 ]]; then
      if [[ $( sudo find "${TOE_MATCHES[@]}" -type f | sudo wc -l) -gt 0 ]]; then
          echo "Deleting files within {{workingDirectory}}/TOE_*"
          sudo find "${TOE_MATCHES[@]}" -type f -exec rm -f {} \;
      fi
      shopt -s nullglob
      TOE_REMAINING=({{workingDirectory}}/TOE_*)
      shopt -u nullglob
      if [[ ${#TOE_REMAINING[@]} -gt 0 ]]; then
          if [[ $( sudo find "${TOE_REMAINING[@]}" -type f | sudo wc -l) -gt 0 ]]; then
              echo "Failed to delete {{workingDirectory}}/TOE_*"
              exit 1
          fi
          echo "Deleting {{workingDirectory}}/TOE_*"
          sudo rm -rf "${TOE_REMAINING[@]}"
      fi
      shopt -s nullglob
      TOE_FINAL=({{workingDirectory}}/TOE_*)
      shopt -u nullglob
      if [[ ${#TOE_FINAL[@]} -gt 0 ]]; then
          echo "Failed to delete {{workingDirectory}}/TOE_*"
          exit 1
      fi
  fi
fi

# Clean up for ssm log files
if [[ -f {{workingDirectory}}/skip_cleanup_ssm_log_files ]]; then
  echo "Skipping cleanup of ssm log files"
else
  echo "Cleaning up ssm log files"
  if [[ -d "/var/log/amazon/ssm" ]]; then
      if [[ $( sudo find /var/log/amazon/ssm -type f | sudo wc -l) -gt 0 ]]; then
          echo "Deleting files within /var/log/amazon/ssm/*"
          sudo find /var/log/amazon/ssm -type f -exec rm -f {} \;
      fi
      if [[ $( sudo find /var/log/amazon/ssm -type f | sudo wc -l) -gt 0 ]]; then
          echo "Failed to delete /var/log/amazon/ssm"
          exit 1
      fi
      echo "Deleting /var/log/amazon/ssm/*"
      sudo rm -rf /var/log/amazon/ssm
      if [[ -d "/var/log/amazon/ssm" ]]; then
          echo "Failed to delete /var/log/amazon/ssm"
          exit 1
      fi
  fi
fi


# Clean up for DHCP lease files
shopt -s nullglob
DHCP_LEASE_MATCHES=(/var/db/dhcpclient/leases/*)
shopt -u nullglob
if [[ ${#DHCP_LEASE_MATCHES[@]} -gt 0 ]]; then
  echo "Deleting /var/db/dhcpclient/leases/*"
  sudo rm -f "${DHCP_LEASE_MATCHES[@]}"
  shopt -s nullglob
  DHCP_LEASE_REMAINING=(/var/db/dhcpclient/leases/*)
  shopt -u nullglob
  if [[ ${#DHCP_LEASE_REMAINING[@]} -gt 0 ]]; then
      echo "Failed to delete /var/db/dhcpclient/leases/*"
      exit 1
  fi
fi

if [[ $( sudo find /var/tmp -type f | sudo wc -l) -gt 0 ]]; then
      echo "Deleting files within /var/tmp/*"
      sudo find /var/tmp -type f -exec rm -f {} \;
fi
if [[ $( sudo find /var/tmp -type f | sudo wc -l) -gt 0 ]]; then
      echo "Failed to delete /var/tmp"
      exit 1
fi
if [[ $( sudo ls /var/tmp | sudo wc -l ) -gt 0 ]]; then
      echo "Deleting /var/tmp/*"
      sudo rm -rf /var/tmp/*
fi

# Flush all pending writes to disk before instance shutdown and snapshot
sync