code: @Override
      public byte[] getUserSessionKey ( CIFSContext tc, byte[] chlng ) {
          if ( this.hashesExternal ) {
              return null;
          }
          return super.getUserSessionKey(tc, chlng);
      }
docs: {@inheritDoc}
  
  @see jcifs.smb.NtlmPasswordAuthenticator#getUserSessionKey(jcifs.CIFSContext, byte[])