How to implement least privilege in programming?

Privilege separation is a security idea that's used a lot in certain types of programming, like systems programming and when we're working with apps that need top-notch security. It's all about sticking to the 'least privilege' rule. This rule says that users, processes, or parts should only have the bare minimum privileges they need to do their jobs. This cuts down on the chance of someone accidentally doing something they shouldn't, or abusing their privileges.

Privilege separation is about splitting a program or system into different parts or processes. Each part has its own level of privilege or access rights. In Provo's paper, they explained how to do this by creating a 'Slave' or 'Child' process, which has just enough privileges to do the actual work. They also created a 'Monitor' or 'Parent' process, which has extra privileges. If the Slave process needs these extra privileges to do something, it asks the Monitor process. The Monitor process checks out the request and if it's okay, it gives the go-ahead. The way the Slave and Monitor processes talk to each other is through IPC (Inter-Process Communication).

The Slave process can make three types of requests: information requests, capability requests, and change of identity requests. Information requests can be handled using stuff like sockets. Capability requests can be dealt with using file descriptors. And a change of identity can be done by getting rid of the current Slave process and making a new one with the extra privileges. It keeps the same UID and GID, and moves the state of the old process over using shared memory.

You can also add more security measures into the mix. For example, you could use authenticated communication, set up a jail directory for the Slave process, or add extra encryption processes (Viega & Messier 2003). Privilege separation is a key idea in secure programming, but it's not a magic solution to get rid of all privilege escalation problems in a program.

Remember, the choice to use Privilege Separation should be based on a good understanding of the security risks and needs of your app or system. While Privilege Separation can boost security, it can also make things more complicated and potentially slow things down. So, it's important to think carefully about the specific security needs, risks, and limits of your project before deciding to use Privilege Separation. And if you do decide to use it, make sure you plan it out properly and follow best practices.