Problem switching UID + GID under FreeBSD

skx has asked for the wisdom of the Perl Monks concerning the following question:

I've deployed a forking server which appears to be having problems on FreeBSD versions 3.2 and below.

This is my code:

use English;               # Avoid $<, etc.

my $username = "nobody";

my ($n,$p, $u,$g, $q,$c,$gc,$dir,$sh);
($n,$p, $u,$g, $q,$c,$gc,$dir,$sh)=getpwnam( $username );

# If we have a uid + gid switch to it.
if ( defined( $u ) and defined( $g ) )
{
    # NOTE: Switch GID first - because once switching UID.
    #       switching GID fails.
        #
    $GID = $g;
    $EGID= $g;
    $UID = $u;
    $EUID= $u;
}
[download]

This setting of GID, EGID, UID, and EUID fails due to broken implementations of setruid() on this platform.

So my question? Is there a sane way to switch UID+GID that will work on FreeBSD in perl? Or a simple way to test for FreeBSD systems to avoid this breakage?

I know I could test $^O - but I'm not sure what a FreeBSD machine would produce.

I guess to detect the failure I can try reading back the values after the switch - but if it fails there's not a lot I can do.

Steve
---
steve.org.uk

Comment on Problem switching UID + GID under FreeBSD Download Code

Replies are listed 'Best First'.
Re: Problem switching UID + GID under FreeBSD by Abigail-II (Bishop) on Oct 29, 2003 at 16:12 UTC
You may want to check out the thread "Is this brokenness in $< $( $> & $)" that's currently running in p5p, which discusses a very similar problem. A patch has been proposed. Abigail	[reply]
Re: Problem switching UID + GID under FreeBSD by sgifford (Prior) on Oct 29, 2003 at 19:36 UTC
I'm not sure exactly what platform limitations you're running into, since I don't have a FreeBSD box, but I seem to recall people using something like this to only use `setreuid` and the like: `($GID,$EGID)=($g,$g); ($UID,$EUID)=($u,$u);` [download] Might be worth a try.	[reply] [d/l]