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public static boolean isSecureDir(Path file) {
  if (!Files.isDirectory( file)) {
    return false;
  }
  if (!file.isAbsolute()) {
    file = file.toAbsolutePath();
  }

  // If any parent dirs (from root on down) are not secure, dir is not secure
  for (int i = 1; i <= file.getNameCount(); i++) {
    Path partialPath = Paths.get( file.getRoot().toString(), file.subpath( 0, i).toString());

    try {
      if (Files.isSymbolicLink( partialPath)) {
        if (!isSecureDir( Files.readSymbolicLink( partialPath))) {
          // Symbolic link, linked-to dir not secure
          return false;
        }
      } else {
        FileSystem fileSystem = partialPath.getFileSystem();
        UserPrincipalLookupService upls = fileSystem.getUserPrincipalLookupService();
        UserPrincipal root = upls.lookupPrincipalByName("root");
        UserPrincipal user = upls.lookupPrincipalByName( System.getProperty("user.name"));
        UserPrincipal owner = Files.getOwner( partialPath);
        if (!owner.equals( user) && !owner.equals( root)) {
          // dir owned by someone else, not secure
          return false;
        }
        PosixFileAttributes attr = Files.readAttributes( partialPath, PosixFileAttributes.class);
        Set<PosixFilePermission> perms = attr.permissions();
        if (perms.contains( PosixFilePermission.GROUP_WRITE) ||
            perms.contains( PosixFilePermission.OTHERS_WRITE)) {
          // someone else can write files, not secure
          return false;
        }
      }
    } catch (IOException x) {
      x.printStackTrace(System.out);
      return false;
    }
  }

  return true;
}