From: Joel VanderWerf <vjoel@...>
Date: 2007-01-25T04:06:56+09:00
Subject: Re: Help with kernel.exec

Petr Janda wrote:
> Hey there,
> Im trying to figure out something. If I had Postfix execute a ruby
> script that says
> 
> Kernel.exec "/usr/sbin/sendmail -i -f #{@sender} -- #{@recipient}"
> 
> would this be a huge security risk? to me it seems so because if you had
> a specially crafted email address you could execute a different command.
> How to protect against it?

One thing you can do is to use 2 or more args with exec.

$ ri exec | cat
------------------------------------------------------------ Kernel#exec
      exec(command [, arg, ...])
------------------------------------------------------------------------
      Replaces the current process by running the given external
      command. If exec is given a single argument, that argument is
      taken as a line that is subject to shell expansion before being
      executed. If multiple arguments are given, the second and
      subsequent arguments are passed as parameters to command with no
      shell expansion.
...

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407