From owner-freebsd-hackers  Tue Jul 14 03:13:08 1998
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Received: (from majordom@localhost)
          by hub.freebsd.org (8.8.8/8.8.8) id DAA14569
          for freebsd-hackers-outgoing; Tue, 14 Jul 1998 03:13:08 -0700 (PDT)
          (envelope-from owner-freebsd-hackers@FreeBSD.ORG)
Received: from frmug.org (frmug-gw.frmug.org [193.56.58.252])
          by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id DAA14564
          for <hackers@FreeBSD.ORG>; Tue, 14 Jul 1998 03:13:05 -0700 (PDT)
          (envelope-from roberto@keltia.freenix.fr)
Received: (from uucp@localhost)
	by frmug.org (8.9.0/frmug-2.3/nospam) with UUCP id MAA17920
	for hackers@FreeBSD.ORG; Tue, 14 Jul 1998 12:12:58 +0200 (CEST)
	(envelope-from roberto@keltia.freenix.fr)
Received: (from roberto@localhost)
        by keltia.freenix.fr (8.9.0.Beta4/keltia-2.14/nospam) id MAA05366
        for hackers@FreeBSD.ORG; Tue, 14 Jul 1998 12:06:05 +0200 (CEST)
        (envelope-from roberto)
Message-ID: <19980714120605.A5227@keltia.freenix.fr>
Date: Tue, 14 Jul 1998 12:06:05 +0200
From: Ollivier Robert <roberto@keltia.freenix.fr>
To: hackers@FreeBSD.ORG
Subject: Re: How do you tell (within the kernel) if we started setuid?
Mail-Followup-To: hackers@FreeBSD.ORG
References: <199807140237.KAA10232@ariadne.tensor.pgs.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
X-Mailer: Mutt 0.93i
In-Reply-To: <199807140237.KAA10232@ariadne.tensor.pgs.com>; from Stephen Hocking-Senior Programmer PGS Tensor Perth on Tue, Jul 14, 1998 at 10:37:46AM +0800
X-Operating-System: FreeBSD 3.0-CURRENT ctm#4462 AMD-K6 MMX @ 225 MHz
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

According to Stephen Hocking-Senior Programmer PGS Tensor Perth:
> If you're executing a program that was started setuid root but has 
> subsequently given up its privileges, is there anyway to tell if it was 
> originally set uid?

There is a system call about this. It looks for a special flag in the
process entry.

NAME
     issetugid - is current process tainted by uid or gid changes

int
issetugid(p, uap)
        register struct proc *p;
        struct issetugid_args *uap;
{
        /*
         * Note: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
         * we use P_SUGID because we consider changing the owners as
         * "tainting" as well.
         * This is significant for procs that start as root and "become"
         * a user without an exec - programs cannot know *everything*
         * that libc *might* have put in their data segment.
         */
        if (p->p_flag & P_SUGID)
                return (1);
        return (0);
}

-- 
Ollivier ROBERT -=- FreeBSD: The Power to Serve! -=- roberto@keltia.freenix.fr
FreeBSD keltia.freenix.fr 3.0-CURRENT #61: Sun Jul 12 14:38:23 CEST 1998

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message