[Sheflug] executing a program as a certain user from a CGI/perl script

[Andrew Basterfield <nospam [at] mailandnews.com>]

OK here's my query

We have a mixed linux/windows LAN in out flat with a Linux intenet 
ip-masq gateway/mailserver/caching DNS. In the past if a user wanted to 
connect the LAN to the internet they would telnet into the gateway and 
run pppd which is suid root. Now I have written a perl cgi script so now 
all the user has to do is point their browser at the server & click on 
the connect or disconnect buttons on the gateway's webpage. This is fine 
except it also allows random internet users outside our LAN to 
disconnect us from the internet also - what I want is a 
username/password login on the webpage (easy with a POST type <form>) 
but how do I run pppd from the perl script with the supplied username & 
password? I tried....

open(shell, "| su $username -c pppd call $connection");
print(shell $password);

[$username, $password & $connection come from POST data from webpage]

..but 'su' won't work down a pipe. This is stretching the limits of my 
(very basic) perl so I'm lost.

any ideas apprectated.

A. Basterfield

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