[OWASP_PHPSEC] Replacement for Insecure Output Functions

Abbas Naderi abiusx at owasp.org
Thu Aug 1 20:11:18 UTC 2013


Hi Folks,
We need replacements for unsafe functions in PHP, for now all those that provide any plain output are deemed unsafe because they provide risk of XSS. We definitely can track them via TaintTracking, but a huge application probably has zillions of those, and running all possible paths are almost impossible.

To solve this issue, we are introducing a static parser, that scans a whole folder of PHP code, and detects every usage of these functions where variables are concatenated and/or outputted. Those with constant strings are safe for now.

Then we ask the developers to replace-all them with our replacements, which are available in core lib. 
Now we need these replacements to be as logical as possible, to encourage developers to switch, and we need them wisely planned beacuse it will be very hard to change them at a later time.

That's why I need you to look at them, and propose ideas how to complete them. We need replacements for all output functions, e.g echo, print, printf, etc. Var_dump and print_r are debug functions and nobody uses them in a real app, so no need for those.

Please see the approach I have taken in the core lib, to understand what I mean more.

The final point is, we need to be able to introduce some decontaminated areas using PHPDOCs, and leave unsafe output be in those areas. These areas should be very limited, possibly only in a single file in the whole project, and are intended to be watched carefully by the developers, cuz they can probably fix XSS issues in a few lines of code, where they certainly can't in a whole project.

I'm awaiting your responses,
-Abbas
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