bsd/man/man2/issetugid.2

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  36 .Dd August 25, 1996
  37 .Dt ISSETUGID 2
  38 .Os
  39 .Sh NAME
  40 .Nm issetugid
  41 .Nd is current process tainted by uid or gid changes
  42 .Sh LIBRARY
  43 .Lb libc
  44 .Sh SYNOPSIS
  45 .In unistd.h
  46 .Ft int
  47 .Fn issetugid void
  48 .Sh DESCRIPTION
  49 The
  50 .Fn issetugid
  51 system call returns 1 if the process environment or memory address space
  52 is considered
  53 .Dq tainted ,
  54 and returns 0 otherwise.
  55 .Pp
  56 A process is tainted if it was created as a result of an
  57 .Xr execve 2
  58 system call which had either of the setuid or setgid bits set (and extra
  59 privileges were given as a result) or if it has changed any of its real,
  60 effective or saved user or group ID's since it began execution.
  61 .Pp
  62 This system call exists so that library routines (eg: libc, libtermcap)
  63 can reliably determine if it is safe to use information
  64 that was obtained from the user, in particular the results from
  65 .Xr getenv 3
  66 should be viewed with suspicion if it is used to control operation.
  67 .Pp
  68 A
  69 .Dq tainted
  70 status is inherited by child processes as a result of the
  71 .Xr fork 2
  72 system call (or other library code that calls fork, such as
  73 .Xr popen 3 ) .
  74 .Pp
  75 It is assumed that a program that clears all privileges as it prepares
  76 to execute another will also reset the environment, hence the
  77 .Dq tainted
  78 status will not be passed on.
  79 This is important for programs such as
  80 .Xr su 1
  81 which begin setuid but need to be able to create an untainted process.
  82 .Sh ERRORS
  83 The
  84 .Fn issetugid
  85 system call is always successful, and no return value is reserved to
  86 indicate an error.
  87 .Sh SEE ALSO
  88 .Xr execve 2 ,
  89 .Xr fork 2 ,
  90 .Xr setegid 2 ,
  91 .Xr seteuid 2 ,
  92 .Xr setgid 2 ,
  93 .Xr setregid 2 ,
  94 .Xr setreuid 2 ,
  95 .Xr setuid 2
  96 .Sh HISTORY
  97 The
  98 .Fn issetugid
  99 system call first appeared in
 100 .Ox 2.0
 101 and was also implemented in
 102 .Fx 3.0 .