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Securing PHP

Securing PHP. Survey of the solutions Stanislav Malyshev stas@zend.com. Most code is extremely buggy…. Can we help?. Input filtering. Unauthorized code (remote include) Unauthorized DB access (SQL Injection) Client subversion (XSS, XSRF). Let’s protect all data. Magic quotes:

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Securing PHP

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  1. Securing PHP Survey of the solutions Stanislav Malyshev stas@zend.com

  2. Most code is extremely buggy… Can we help?

  3. Input filtering • Unauthorized code (remote include) • Unauthorized DB access (SQL Injection) • Client subversion (XSS, XSRF)

  4. Let’s protect all data Magic quotes:  a.php?data=1’2 -> $data == “1\’2” can be inside quotes • Optional • No support for context

  5. Let’s restrict the user Safe mode:  Allow access only to own files  Allow only “safe” actions  No OS support  Too many modules not controlled  Too hard to find out all “unsafe” ones and not kill apps

  6. Let’s filter • $var = filter_input(INPUT_GET, 'var'); • Standard filters for standard use-cases • No time machine • Voluntary

  7. Let’s watch the data Data tainting • No unfiltered data in sensitive contexts • How do I know the filtering was right? • Complex implementation – contexts • Performance

  8. Static  Can be as slow as it needs to False positive OK External engine $$foo = $$bar $foo->$bar($baz) eval($foo.$bar) Dynamic Real code, real data Can prevent attack Need for speed Engine modification Breaks applications Static vs. Dynamic

  9. Let’s watch the data - II CSSE • Track each character of data • Ensure the data is safely • Safety is context-dependant • Modification for all operations • Performance?

  10. Let’s watch the input & learn Runtime detection  No need to study application • No need to study context • Complex heuristics • Needs data collection

  11. ?

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