Running a PHP system()/exec() command with root privs...

I am doing a lot of checking above that code hoffmann.  Any scripts that chmod and chown I am pretty careful with.  =)  You might laugh, but this is actually for OS-X in a very multi-user environment.  I have a netinfo server which this script is going on, and it will store user's logins and personal files and allow users to login over the network with the right credentials from other OS-X machines.  Anyway, I am going to try your idea now.  I never would have though to try SSH.  I assume it is the answer though.  I'll be back on in a few min once I figure out if that worked for me or not.

> You might laugh, ..
it's not me laughing, but any black had identifying a vulnerability in your web site, and giving you a shortname like:

   whatever;rm -rf /*&;

or even more complex ..
Even if it is accessable only via intranet, it might be vulnerable, just think of someone sending you a HTML formated mail with a link to your CGI, filling in the above code. Most people do not realize the trick, unfortunatelly.

I could not figure out how to get SSH to work from a key, instead I did find that I could do the following.  Have a file with the root password in it that I hide in a bunch of subfolders and run the following command from php...

exec("sudo -u root -S chown admin:staff /Users/alal/ < /ghost/folder/la41230/pass\n");

Where pass contains the root password, hidden in a few subfolders for minor security.  And for the logins I am first checking for no spaces because well, it has to be a single string, also limiting it to 8 characters, then running it through a filter to check for non-alphanumeric characters.  Now... I think that should be good enough, but sure, someone could find a way around it I'm sure.  Having the password in a plaintext file isn't exaxtly the smartest thing here either, and I know this.  But this is for a educational facility and access to the website will be restricted to me and two other educated faculty.  The reason I am still commenting is that...

#1: I couldn't get your way to work, can't find out how to use keys for SSH.
#2: My way works perfectly from the console on the server... but when run from within' PHP I get a completely irrellevant error...
/etc/mail/sendmail.cf: line 81: fileclass: cannot open /etc/mail/local-host-names: Group writable directory

I am not doing anything relating to mail... I have a feeling I have accidently stumbled upon something that is way beyond me, like a flaw in PHP, or something.  I do have mail support enabled from within' Apache that uses sendmail.cf.  Any ideas...?  =)  BTW, I marked your first answer as an answer because if I could setup SSH like you said, it would prolly work.  =)

buuuh, which sudo (on which OS) did read from STDIN and/or here documents?

#1: hmm probably another question now
#2: does sendmail have something to do with this wuestion?
    anyway, it complains if you have a mailbox and/or .forward (probably .vcation too) in a group-writable user directory, sendmail.cf has a setting to ignore this (not well documented, 'cause not recomended anyway)

That's the thing, sendmail has nothing to do with the question.  I am not even using anything related to sendmail.  But for some reason when I run that line on PHP/Apache on OS-X Server 10.1, I get the sendmail error, odd huh?  Sadly enough, I'm close to giving up on this idea and just making them call me to add/delete users.  =\  Thanks for your help hoffman

just guessing:
  the web server tries to send a mail when a CGI or PHP script fails