Date: Fri, 17 Sep 2004 15:26:17 -0400 From: Bill Moran <wmoran@potentialtech.com> To: Richard Bradley <rtb27@cam.ac.uk> Cc: freebsd-questions@freebsd.org Subject: Re: how to make an executable run as another user Message-ID: <20040917152617.2cbdf4c5.wmoran@potentialtech.com> In-Reply-To: <200409171950.19717.rtb27@cam.ac.uk> References: <200409171950.19717.rtb27@cam.ac.uk>
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Richard Bradley <rtb27@cam.ac.uk> wrote: > Um. I feel silly asking this. But I can't work it out. Not silly, common problem for shell script writers. > I want a shell script to run as another user. I always thought this was easy > to do with the setuid bit, but never tried it before. I read "man chmod" and > found this: > > ..... > 4000 (the setuid bit). Executable files with this bit set will > run with effective uid set to the uid of the file owner. > ..... > s The set-user-ID-on-execution and set-group-ID-on-execution > bits. > .... > > And off I went. I wrote a shell script to output the current uid. I chown'ed > it to another user. I "chmod +s"ed it. I ran it. > > It didn't work. > > ----- > > rtb27# cat test > #! /bin/sh > whoami > rtb27# ll test > -rwsr-sr-x 1 rich wheel 20 Sep 17 19:34 test > rtb27# ./test > root Interpreted programs (i.e. scripts) don't honor setuid/setgid (with the notable exception of setuidperl, which is installed but disabled on FreeBSD) Clever use of su or sudo can work around this. Also, writing a C or C++ wrapper program will help. That's a bit of a PITA, though. -- Bill Moran Potential Technologies http://www.potentialtech.com
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