Fail2BANを使ってみる

サーバのログから特定のキーワードを抽出し、該当アクセスを遮断してくれるFail2BANというソフトがあります。
似たようなことはシェルスクリプトでも出来なくはないのですが、N回連続でアクセスがあったら10分ブロック。のようなことができます。

なお、Fail2BANはiptablesにルールを動的に差し込むことで遮断しますので、iptablesが動作する環境が必要です。

• インストール

  apt-get install fail2ban

• 設定
  jail.localに設定をすると、jail.confを上書きできます。jail.confはアップデート時に変更されることがあるので
  jail.localのほうへ設定をします。

• jail.localの設定例

  [INCLUDES]
  
  #before = paths-distro.conf
  before = paths-debian.conf      #Ubuntuなので、こちらを読み込ます
  
  # The DEFAULT allows a global definition of the options. They can be overridden
  # in each jail afterwards.
  
  [DEFAULT]
  
  #
  # MISCELLANEOUS OPTIONS
  #
  
  # "ignoreip" can be an IP address, a CIDR mask or a DNS host. Fail2ban will not
  # ban a host which matches an address in this list. Several addresses can be
  # defined using space separator.
  ignoreip = 127.0.0.1/8 # BAN対象外ネットワークを設定。
  
  # External command that will take an tagged arguments to ignore, e.g. <ip>,
  # and return true if the IP is to be ignored. False otherwise.
  #
  # ignorecommand = /path/to/command <ip>
  ignorecommand =
  
  # "bantime" is the number of seconds that a host is banned.
  bantime  = 3600   # BANする秒数
  
  # A host is banned if it has generated "maxretry" during the last "findtime"
  # seconds.
  findtime  = 30  # 条件に合致したとカウントする秒数
  
  # "maxretry" is the number of failures before a host get banned.
  maxretry = 1  # 条件に合致した回数
  
  
  #
  # ACTIONS
  #
  
  # Some options used for actions
  
  # Destination email address used solely for the interpolations in
  # jail.{conf,local,d/*} configuration files.
  destemail = fail2ban@example.com
  
  # Sender email address used solely for some actions
  sender = fail2ban@example.com
  
  
  #
  # JAILS
  #
  

• 設定例
  • PHPMYADMINへのアタック防御
    まずはログから対象となるキーワードをひっかける設定を行います。参考
    • filter.d/apache-phpmyadmin.confを作成

      [Definition]
      failregex = \[client <HOST>\] File does not exist:.*(?i)admin.*
                  \[client <HOST>\] File does not exist:.*(?i)manager.*
                  \[client <HOST>\] File does not exist:.*(?i)setup.*
                  \[client <HOST>\] File does not exist:.*(?i)mysql.*
                  \[client <HOST>\] File does not exist:.*(?i)sqlweb.*
                  \[client <HOST>\] File does not exist:.*(?i)webdb.*
                  \[client <HOST>\] File does not exist:.*(?i)pma.*
                  \[client <HOST>\] File does not exist:.*(?i)vtigercrm.*
                  ^<HOST>.*GET.*(?i)admin.*
                  ^<HOST>.*GET.*(?i)manager.*
                  ^<HOST>.*GET.*(?i)setup.*
                  ^<HOST>.*GET.*(?i)mysql.*
                  ^<HOST>.*GET.*(?i)sqlweb.*
                  ^<HOST>.*GET.*(?i)webdb.*
                  ^<HOST>.*GET.*(?i)pma.*
                  ^<HOST>.*GET.*(?i)vtigercrm.*
      
                  [[]client <HOST>[]] user .* authentication failure
                  [[]client <HOST>[]] user .* not found
                  [[]client <HOST>[]] user .* password mismatch
      
                  ^<HOST> -.*"POST /wp-login.php HTTP.*$
      
                  [[]client <HOST>[]] script '.*' not found or unable to stat$
                  [[]client <HOST>[]] client denied by server configuration:
                  [[]client <HOST>[]] File does not exist: .*([Aa]dmin|[Mm]anager|[Ee]ditor|[Uu]ser|login)
                  [[]client <HOST>[]] File does not exist: .*/([Pp][Mm][Aa]|[Mm][Yy][Ss][Qq][Ll])
                  [[]client <HOST>[]] File does not exist: .*/(db|scripts|forum|board|[vV][bB])
                  [[]client <HOST>[]] File does not exist: .*/(blog|wordpress|wp)
                  [[]client <HOST>[]] File does not exist: .*/(catalog|shop|oscommerce|ipb)
      
      ignoreregex =

    • 設定がマッチするかをチェックします。

      fail2ban-regex  /var/log/apache2/access_log /etc/fail2ban/filter.d/apache-phpmyadmin.conf

    • jail.localに以下追記します。

      [apache-admin]
      enabled  = true
      filter   = apache-phpmyadmin
      action  = iptables[name=admin, port=http,https protocol=tcp]
                sendmail-whois[name=admin, dest=root]
      logpath  = /var/log/apache2/error.log
                 /var/log/apache2/access.log
      maxretry = 10
      findtime = 1200
      bantime = 1200

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