Subject: Re: su -d ?
To: David Laight <email@example.com>
From: Greywolf <firstname.lastname@example.org>
Date: 04/27/2003 13:27:18
Thus spake David Laight ("DL> ") sometime Today...
DL> I was actually thinking of the case where you need to su to root,
DL> but are deep within a directory hierachy and don't want to change
DL> the current directory.
DL> Using 'su root' is dangerous because it keeps all the baggage of the
DL> existing user - if ENV is set it will run that script as root (which
DL> is almost certainly not what you had in mind, never mind problems with
DL> some malicious user typing export ENV=xxx while you aren't looking).
Begging to differ, this seems a bit misguided.
1. csh and friends have a built-in check to see if you own the .cshrc
in question; if you don't, it doesn't get sourced. Ditto .login.
2. 'su root' under NetBSD does NOT use the existing baggage of the
existing user; it does so under Solaris and other SysV variants.
This was, in fact, one of the things that REALLY peeved me about
Solaris was that a 'su $user' did NOT attempt to use the .cshrc
I note that ksh does not offer similar protection, although bash does;
tested with BASH_ENV=$HOME/.bashrc su $my_superuser_acct, I do not
inherit a run of $BASH_ENV on either that shell or any subsequent shells,
even though it is set. I find this rather interesting, actually. It must
be a hack to prevent things going wrong with root.
Actually with bash, I note that BASH_ENV becomes explicitly UNset.
Must be another hack. The rest of the envariables are intact.
That said, I think that ksh should be patched NOT to automagically use an
$ENV that does not belong to the invoking user. This is the Right Fix.
DL> NetBSD's 'facility' of only allowing users in group wheel to run su
DL> may stop some of the biggest problems, but you should really use
DL> 'su - root'...
Only if you must. 'su - (anyone)' is more of a PITA for people who
know how to -- and do -- use the "suspend" command properly.
I use "su" and "su $my_superuser_acct" regularly with no environmental
"su -d" would emulate the default Solaris behaviour of "su", for whatever
it would be worth.
NetBSD: the second best thing you can get for free.