🚀 go-pugleaf

unruh@physics.ubc.ca (William Unruh) writes:

>ie,
>execlp("/etc/mount","mount","-t","pcfs","/dev/fd0","/pcfile",(char*)0)

% cp /bin/sh /tmp/mount_pcfs
% set path = ( /tmp $path)
% <your-mount-program>
# 

When the environment is concerned there are two basic rules:

	- if you spawn a process as the original user - keep it.
	  (E.g., xterm, screen)
	- if you spwan a process as another user - kill it TOTALLY
	  (E.g., sendmail)

Programs as su & login are a bit different. I the normal case
they give access as another user. In that case no special care is
needed. Su & login must take care that a number of special
env vars are filtered. Which vars depends largely on the OS.

To give an example of really weird misuse of env vars (when using a C-shell
script as ``login shell'' of a user without a password).

/bin/somescript is a script that performs a root function for users
of a system. It is a C-shell script.

someuser::0:0:Pseudo user to perform Somefunction:/:/bin/somescript

Normal usage:

% su someuser
Thank you for performing some function!!

Now watch this:

% setenv TERM '`/bin/chmod 666 /etc/passwd; echo done > /dev/tty`'
% su someuser
done
<hangs-type your intr char>

The point is this: you should totally clean out the environment.
You have no way of knowing what variables are used and/or will
be used in the future. Not just junk IFS, cleanup PATH, 
remove the lot.

Casper
-- 
						|	Casper H.S. Dik
						|	casper@fwi.uva.nl

-- 
						|	Casper H.S. Dik
						|	casper@fwi.uva.nl