Hadoop security overview

Originally, Hadoop was designed to operate in a trusted environment. It was assumed that all cluster users can be trusted to correctly present their identity and will not try to obtain more permissions than they have. This resulted in implementation of a simple security mode, which is the default authentication system in Hadoop. In a simple security mode, Hadoop trusts the operating system to provide the user's identity. Unlike most relational databases, Hadoop doesn't have any centralized users and privileges storage. There is no user/password concept that would allow Hadoop to properly authenticate the user. Instead, Hadoop accepts the name of the user as represented by the operating system and trusts it without any further checks. The problem with this model is that it is possible to impersonate another user. For example, a rogue user could use a custom built HDFS client, which instead of using Java calls to identify the current OS user will just substitute it...