This case study is a result of source code analysis of Apache httpd server MPM modules. The main goal of this document is to show what may be done by an attacker who has the possibility of running arbitrary code in the context of the worker process (WP).
The work has been concentrated on verifying whether (and to which extent) it is secure to run an external code in the worker process context. Such code may be provided through appropriate functions of script languages attached as a module (like dl(), dlopen()) or as a result of running an exploit of one of vulnerabilities found in Apache modules (e.g. Integer Overflow in chunk_split() function). In order to simulate running an external code in the WP context we use dl() function from mod_php module.
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