👉 Overview
👀 What ?
Under the Linux operating system, euid, ruid, and suid are three user identifiers that play a crucial role in managing user permissions and ensuring system security. Euid refers to 'Effective User ID', ruid to 'Real User ID', and suid to 'Set User ID'.
🧐 Why ?
Understanding these identifiers is crucial as they help in managing user permissions, ensuring that users can only access the resources and execute the commands that are necessary for their work. This concept is necessary for maintaining system security and preventing unauthorized access to sensitive data and system resources.
⛏️ How ?
In a Linux system, when a user logs in, their ruid and euid are set to their user ID. The ruid indicates who the user actually is, while the euid determines what the user can do, especially in terms of access permissions. The suid is a special type of permission that allows a user to execute a file with the permissions of the file owner. This is typically used in programs that require higher privileges to run. In order to use these identifiers effectively, it's important to have a clear understanding of the Linux Permission Model and the principles of least privilege.
⏳ When ?
The use of euid, ruid, and suid in the Linux OS was introduced with the Unix operating system in the 1970s and has been a part of the Linux security model since its inception.
⚙️ Technical Explanations
The Linux system uses several user identifiers such as the euid, ruid, and suid to manage user permissions and ensure system security. The ruid identifies the user who created the process, while the euid is used by the system to decide what resources a process can access. The suid, on the other hand, is a special type of file permission that allows a user to execute a file with the permissions of the file owner, rather than the user who ran it. This is particularly useful for executing programs that require higher privileges. It's important to manage these identifiers carefully, as misuse can lead to security vulnerabilities. For example, setting the suid bit on a file that can be manipulated can allow an attacker to elevate their privileges and take control of the system.