What is the diferrence between making, say, shutdown executable by the non-root user by doing:
chmod u+s /sbin/shutdown
giving:
-r-sr-x--- root root shutdown?

and just making shutdown executable by all?

Thanks any help.

Setting the SUID bit forces the program to run with the privelages of the program owner. Making something executable by all will allow anybody to run the program; however, it may fail if the user does not have appropriate privelages.

Thanks.

You couldn't give an example of where the suided progam and the all-may-excuted program behave differently could you? Sorry if being dense.

I think "crontab" and "at" are good examples.

Due to underlying (system) authority issues w/these commands, they need to run w/setuid.

I think I'm right?

hope this helps,
manny


/home/manny> ll /usr/bin/* | grep rws
-rwsr-sr-x 1 root root 164 Jun 13 11:04 /usr/bin/aptlist
-rwsr-xr-x 1 root root 37528 Jan 17 2002 /usr/bin/at
-rwsr-sr-x 1 root root 31112 Apr 3 2002 /usr/bin/cdparanoia
-rwsr-sr-x 1 root root 593233 Feb 22 2002 /usr/bin/cdrdao
-rwsr-sr-x 1 root root 211146 Feb 28 2002 /usr/bin/cdrecord
-rwsr-xr-x 1 root root 34296 Feb 12 2003 /usr/bin/chage
-rws--x--x 1 root root 12072 Jun 24 2002 /usr/bin/chfn
-rws--x--x 1 root root 11496 Jun 24 2002 /usr/bin/chsh
-rwsr-xr-x 1 root root 21080 Apr 14 2002 /usr/bin/crontab
-rwsr-xr-x 1 root root 36100 Feb 12 2003 /usr/bin/gpasswd
-rwsr-xr-x 1 root root 39215 Aug 19 2002 /usr/bin/kv4lsetup
-rwsr-sr-x 1 root root 402726 Jul 16 2002 /usr/bin/lame
-rwsr-xr-x 1 root root 19931 May 13 03:06 /usr/bin/lppasswd
-rwsr-sr-x 1 root root 404480 Feb 28 2002 /usr/bin/mkisofs
-rwsr-sr-x 1 root root 137084 Jul 16 2001 /usr/bin/ncpmount
-rwsr-sr-x 1 root root 117628 Jul 16 2001 /usr/bin/ncpumount
-rws--x--x 1 root root 4764 Jun 24 2002 /usr/bin/newgrp
-rwsr-xr-x 1 root root 149454 Jul 16 2001 /usr/bin/nwsfind
-rwsr-xr-x 1 root root 14588 Jul 24 2001 /usr/bin/rcp
-rwsr-xr-x 1 root root 10940 Jul 24 2001 /usr/bin/rlogin
-rwsr-xr-x 1 root root 7932 Jul 24 2001 /usr/bin/rsh
-rwsr-sr-x 1 root root 4816 Jul 16 2001 /usr/bin/slist
-rws--x--x 2 root root 808526 Aug 18 13:12 /usr/bin/sperl5.6.1
-rws--x--x 2 root root 808526 Aug 18 13:12 /usr/bin/suidperl

SUID example: passwd -without the SUID bit, users would not be able to change their password because /etc/shadow is accessible only by root.

Executable by all example: more -any user can run it but it doesn't always let you view the file if you don't have permission (ie more /etc/shadow as a nonroot user)

Right - I get it. You've got to call that a success. Thanks.