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Pádraic Brady:
PHP's "Magic Hash" Vulnerability (Or Beware Of Type Juggling)
May 14, 2015 @ 12:19:43

Pádraic Brady has a new post to his site talking about the recently announced (but actually relatively old) issue with PHP hash comparison, the "magic hash" issues.

A while back, I noticed a flurry of activity around a somewhat obvious outcome of PHP's type juggling antics. As the snowball gathered pace and grew, it's being more widely reported as a vulnerability dubbed "Magic Hashes". What is this mysterious potential vulnerability in PHP applications? The vulnerability is a straightforward outcome of PHP's type juggling antics.

He talks about the == (double equals) versus === (triple equals), how they differ and how the use of the triple equals basically negates this issue. The problem comes back around to PHP's type juggling and how it assumes equality based on the data given. He includes some specific examples showing places the issue can happen even when comparing two variables of the same type. He also makes a mention of another issue that can come in separate from this called timing attacks and how to prevent them as well.

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magichash vulnerability typejuggling timing attack doubleequals tripleequals

Link: http://blog.astrumfutura.com/2015/05/phps-magic-hash-vulnerability-or-beware-of-type-juggling/

Jani Hartikainen:
Parsing and evaluating PHP in Haskell Part 2
January 23, 2013 @ 11:24:34

Jani Hartikainen has posted the second article in his series looking at parsing PHP with Haskell (part one is here). In this new article he builds on the parser he built last time and gets to the actual evaluation of the PHP code.

Last week I wrote a post about a PHP parser / evaluator I wrote in Haskell. I explained some of the parts on how the parser itself was designed to process PHP code into an abstract source tree. Continuing from where we left off in the previous part, in this post I'll discuss the actual evaluation part.

He starts by introducing the structure of the evaluator script, how it's broken up into functionality based on the type of object/data type being handled. He uses a "custom monad transformer stack" to handle the environment for the evaluation as is progresses. He talks about handling statements and expressions, declaring custom functions and the actual execution of the function call. There's also a mention of handling conditionals/looping as well as dealing with PHP's type juggling.

if you're interested in seeing the final result (and maybe trying it out for yourself) you can find the full source on Github.

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haskell parse evaluate monad transformer functions expressions looping typejuggling



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