Puppet::Parser::Functions::newfunction(
  :pw_hash,
  :type => :rvalue,
  :arity => 3,
  :doc => "Hashes a password using the crypt function. Provides a hash
  usable on most POSIX systems.

  The first argument to this function is the password to hash. If it is
  undef or an empty string, this function returns undef.

  The second argument to this function is which type of hash to use. It
  will be converted into the appropriate crypt(3) hash specifier. Valid
  hash types are:

  |Hash type            |Specifier|
  |---------------------|---------|
  |MD5                  |1        |
  |SHA-256              |5        |
  |SHA-512 (recommended)|6        |

  The third argument to this function is the salt to use.

  Note: this uses the Puppet Master's implementation of crypt(3). If your
  environment contains several different operating systems, ensure that they
  are compatible before using this function.") do |args|
    raise ArgumentError, "pw_hash(): wrong number of arguments (#{args.size} for 3)" if args.size != 3
    raise ArgumentError, "pw_hash(): first argument must be a string" unless args[0].is_a? String or args[0].nil?
    raise ArgumentError, "pw_hash(): second argument must be a string" unless args[1].is_a? String
    hashes = { 'md5'     => '1',
               'sha-256' => '5',
               'sha-512' => '6' }
    hash_type = hashes[args[1].downcase]
    raise ArgumentError, "pw_hash(): #{args[1]} is not a valid hash type" if hash_type.nil?
    raise ArgumentError, "pw_hash(): third argument must be a string" unless args[2].is_a? String
    raise ArgumentError, "pw_hash(): third argument must not be empty" if args[2].empty?
    raise ArgumentError, "pw_hash(): characters in salt must be in the set [a-zA-Z0-9./]" unless args[2].match(/\A[a-zA-Z0-9.\/]+\z/)

    password = args[0]
    return nil if password.nil? or password.empty?

    salt = "$#{hash_type}$#{args[2]}"

    # handle weak implementations of String#crypt
    if 'test'.crypt('$1$1') != '$1$1$Bp8CU9Oujr9SSEw53WV6G.'
      # JRuby < 1.7.17
      if RUBY_PLATFORM == 'java'
        # puppetserver bundles Apache Commons Codec
        org.apache.commons.codec.digest.Crypt.crypt(password.to_java_bytes, salt)
      else
        # MS Windows and other systems that don't support enhanced salts
        raise Puppet::ParseError, 'system does not support enhanced salts'
      end
    else
      password.crypt(salt)
    end
end
