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Chapter 38. Writing Secure Privileged Programs > Operate with Least Privilege
38.2. Operate with Least Privilege
A set-user-ID (or set-group-ID) program typically requires privileges only to perform certain operations. While the program (especially one assuming superuser privileges) is performing other work, it should disable these privileges. When privileges will never again be required, they should be dropped permanently. In other words, the program should always operate with the least privilege required to accomplish the tasks that it is currently performing. The saved set-user-ID facility was designed for this purpose (Section 9.4).
38.2.1.
38.2.1.1. Hold privileges only while they are required
In a set-user-ID program, we can use the following sequence of seteuid() calls to temporarily drop and then reacquire privileges:
