issetugid man page on FreeBSD

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ISSETUGID(2)		    BSD System Calls Manual		  ISSETUGID(2)

     issetugid — is current process tainted by uid or gid changes

     Standard C Library (libc, -lc)

     #include <unistd.h>


     The issetugid() system call returns 1 if the process environment or mem‐
     ory 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 privi‐
     leges 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” sta‐
     tus 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 process.

     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),
     setreuid(2), setuid(2)

     The issetugid() system call first appeared in OpenBSD 2.0 and was also
     implemented in FreeBSD 3.0.

BSD				August 25, 1996				   BSD

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