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General cleanup and update to specify exactly how our implementation

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passes on the status across fork/exec.

The previous version had some typos, referred to itself as link(2) in
one place :-), and didn't really match openbsd's implementation either.

Now that I've mentioned typos, hopefully our Typo Police and Xref Police
will be gentle with me. :-)
This commit is contained in:
Peter Wemm 1997-03-31 16:36:14 +00:00
parent 8996ff49a1
commit 0e1cf9a328
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=24456
1 changed files with 38 additions and 31 deletions
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69
lib/libc/sys/issetugid.2
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@ -31,12 +31,14 @@
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $Id$
.\"
.Dd August, 25 1996
.Dt ISSETUGID 2
.Os OpenBSD 2.0
.Os
.Sh NAME
.Nm issetugid
.Nd is current executable running setuid or setgid
.Nd is current process tainted by uid or gid changes
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
@ -44,31 +46,31 @@
.Sh DESCRIPTION
The
.Fn issetugid
function returns 1 if the process was made setuid or setgid as
the result of the last
.Fn execve
system call.
Otherwise it returns 0.
function returns 1 if the process environment or memory address space
is considered ``tainted'', and returns 0 otherwise.
.Pp
This system call exists so that library routines (inside libc, libtermlib,
or other libraries) can gaurantee safe behavior when used inside
setuid or setgid programs.
Some library routines may not be passed sufficient information to know
if the current program was started setuid or setgid because higher level
calling code may have made changes to the uid or the euid.
In particular, it is wise to use this call to determine if a
pathname returned from a
.Fn getenv
call may safely be used to
.Fn open
the specified file.
A process is tainted if it was created as a result of an
.Xr 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 it's real,
effective or saved user or group ID's since it began execution.
.Pp
.Fn issetugid
is unaffected by calls to
.Fn setuid ,
.Fn fork ,
and other such calls. It is only controlled by
.Fn execve .
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
.Xr getenv 3
should be viewed with suspicion if it is used to control operation.
.Pp
A ``tainted'' status is inherited by child processes as a result of the
.Xr fork 2
system call (or other library code that calls fork, such as
.Xr popen 3 ).
.Pp
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
.Xr su 1
which begin setuid but need to be able to create an untainted process.
.Sh ERRORS
The
.Fn issetugid
@ -76,12 +78,17 @@ function is always successful, and no return value is reserved to
indicate an error.
.Sh SEE ALSO
.Xr execve 2 ,
.Xr setuid 2 ,
.Xr seteuid 2,
.Xr fork 2 ,
.Xr setgid 2 ,
.Xr setegid 2
.Xr setegid 2 ,
.Xr seteuid 2 ,
.Xr setregid 2 ,
.Xr setregid 2 ,
.Xr setuid 2
.Sh HISTORY
A
.Fn lstat
function call appeared in
OpenBSD 2.0
.Fn issetugid
function call first appeared in
.Ox 2.0
and was also implemented in
.Fx 3.0 .