Re: [PHP] PHP subset for user-defined functions

> On 2 December 2016 19:17:36 GMT+00:00, [email protected] wrote:
>> Ihave developed and operated a Linux-Apache-MySQL-PHP service for
>> several years.A new feature requires support for simple, user-defined
>> functions, to returnvalues used by the service. Here, we’re talking
>> about front-end users on theinternet, with some vetting, and typically
>> with some software engineeringexperience. I’ve been thinking about
>> security and support issues of course.Currentplans are to offer a
>> subset of PHP for the user-defined functions: Submittedfunctions would
>> be scanned, and only allowed functions and keywords would besupported.
>> Variable functions would be disallowed, etc. Does anyone haveexperience
>> or advice regarding this type of
>> approach?Thanks,GeorgeSherwoodThesereferences describe the
>> feature:http://testcover.com/pub/background/ecbecc.pdfhttp://testcover.com/pub/background/iwct2015.pdfhttp://testcover.com/pub/background/iwct2016.pdf

> Even with the best of intentions, this sounds fraught with potential  
> security flaws.

> What sorts of things do you want them to be able to do? Is it  
> feasible to offer them basic building blocks which can be connected  
> to each other, e.g. graphical programming style?


> Thanks,
> Ash

My apologies for the one-liner; I'm trying a different mailer now.

> Even with the best of intentions, this sounds fraught with potential  
> security flaws.
Yes. This was my initial thought too. If you have specifics, I'd love  
to hear them.
I have looked into vulnerabilities somewhat.

> What sorts of things do you want them to be able to do?
Here's an example. There are more in the PDFs cited above.

function Weight_boundary($Height,$BMI_boundary,$Input_limit) { /*  
Weight boundary value function */
   if($Height>0&&$BMI_boundary>0) {
     $w_hi=ceil($Height*$Height*$BMI_boundary/703.06957964); /* round  
up $w_hi so BMI >= $BMI_boundary */
     switch($Input_limit) {
       case 'min':
         return($w_hi); /* return minimum integer value for higher BMI class */
       case 'max':
         $w_lo=$w_hi-1;
         return $w_lo; /* return maximum integer value for lower BMI class */
     }
   }
}

> Is it feasible to offer them basic building blocks which can be  
> connected to each other, e.g. graphical programming style?
I don't think so. The plan under consideration would use only the most basic,
safe internal functions.
BTW, I appreciate the power and flexibility of PHP. That's why I use it.
And I don't take the idea of limiting it lightly.

Best regards,
George