[HDFS-15051] RBF: Impose directory level permissions for Mount entries

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.4.0
• Component/s: rbf
• Hadoop Flags: Reviewed
• Assignee: Xiaoqiao He
• Reporter: Xiaoqiao He
• Created: 11/Dec/19 13:59
• Updated: 02/Apr/20 06:05
• Resolved: 02/Apr/20 05:50

Description

The current permission checker of #MountTableStoreImpl is not very restrict. In some case, any user could add/update/remove MountTableEntry without the expected permission checking.
The following code segment try to check permission when operate MountTableEntry, however mountTable object is from Client/RouterAdmin MountTable mountTable = request.getEntry();, and user could pass any mode which could bypass the permission checker.

  public void checkPermission(MountTable mountTable, FsAction access)
      throws AccessControlException {
    if (isSuperUser()) {
      return;
    }

    FsPermission mode = mountTable.getMode();
    if (getUser().equals(mountTable.getOwnerName())
        && mode.getUserAction().implies(access)) {
      return;
    }

    if (isMemberOfGroup(mountTable.getGroupName())
        && mode.getGroupAction().implies(access)) {
      return;
    }

    if (!getUser().equals(mountTable.getOwnerName())
        && !isMemberOfGroup(mountTable.getGroupName())
        && mode.getOtherAction().implies(access)) {
      return;
    }

    throw new AccessControlException(
        "Permission denied while accessing mount table "
            + mountTable.getSourcePath()
            + ": user " + getUser() + " does not have " + access.toString()
            + " permissions.");
  }

I just propose revoke WRITE MountTableEntry privilege to super user only.