Abstract

Failure to adhere to the principle of least privilege amplifies the risk posed by other vulnerabilities.

Description

Programs that run with root privileges have caused innumerable Unix security disasters. It is imperative that you carefully review privileged programs for all kinds of security problems, but it is equally important that privileged programs drop back to an unprivileged state as quickly as possible in order to limit the amount of damage that an overlooked vulnerability might be able to cause.

Privilege management functions can behave in some less-than-obvious ways, and they have different quirks on different platforms. These inconsistencies are particularly pronounced if you are transitioning from one non-root user to another.

Signal handlers and spawned processes run at the privilege of the owning process, so if a process is running as root when a signal fires or a sub-process is executed, the signal handler or sub-process will operate with root privileges. An attacker may be able to leverage these elevated privileges to do further damage.