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issetugid — is current process tainted by uid or gid changes
Standard C Library (libc, -lc)
The issetugid() system call returns 1 if the process environment or
memory address space is considered “tainted”, and returns 0 otherwise.
A process is tainted if it was created as a result of an execve(2) system
call which had either of the setuid or setgid bits set (and extra
privileges were given as a result) or if it has changed any of its real,
effective or saved user or group ID's since it began execution.
This system call exists so that library routines (eg: libc, libtermcap)
can reliably determine if it is safe to use information that was obtained
from the user, in particular the results from getenv(3) should be viewed
with suspicion if it is used to control operation.
A “tainted” status is inherited by child processes as a result of the
fork(2) system call (or other library code that calls fork, such as
It is assumed that a program that clears all privileges as it prepares to
execute another will also reset the environment, hence the “tainted”
status will not be passed on. This is important for programs such as
su(1) which begin setuid but need to be able to create an untainted
The issetugid() system call is always successful, and no return value is
reserved to indicate an error.
execve(2), fork(2), setegid(2), seteuid(2), setgid(2), setregid(2),
The issetugid() system call first appeared in OpenBSD 2.0 and was also
implemented in FreeBSD 3.0.