what is setuid
The setuid (set user ID)
is a special permission in Unix-like operating systems that allows a user to execute a program with the privileges of the program's owner instead of their own. In simple terms:
When a program has the setuid permission set and is run by a user, it runs with the permissions and privileges of the user who owns the program.
This can be useful for granting temporary elevated privileges to regular users when they need to perform certain tasks that require higher permissions, such as system maintenance or administrative tasks.
It's a security mechanism that should be used carefully, as it can potentially introduce security vulnerabilities if not implemented properly.
For example, if there is a program owned by the system administrator and has the setuid bit set, a regular user running that program will temporarily gain the privileges of the administrator while executing that specific program. After the program finishes running, the user's privileges return to their normal level.
The setuid permission is denoted by an 's' in the execute position of the owner's permission field when you view file permissions using the ls -l command. For example:
diffCopy code-rwsr-xr-x 1 owner user 12345 Nov 23 10:00 myprogram
In this example, the "s" in the owner's execute permission position indicates that the setuid permission is set for the "myprogram" executable.