The blog of a gypsy engineer

Software security, electronics, DIY and traveling.

MessagePack fuzzing

MessagePack is a binary serialization format. There are lots of open source implementations of this protocol on various languages including C/C++. It’s good to do something good in new year. For example, it can be a little contribution to an open source project. Let’s check quickly if the implementation on C/C++ has any memory corruption issues. One of the best ways is of course fuzzing.

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Fuzzing GUI applications: AbiWord

Usually there is no problem if you want to fuzz a headless application. A headless application can be run just in a terminal, and doesn’t have any GUI. You can pick up your favorite fuzzer, and feed fuzzed data to the application. Normally, a headless application just processes data, and then quits or crashes right away. But it may be different if you are trying to fuzz an application with GUI. Let’s try to fuzz an open source text editor AbiWord.

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Python marshal module fuzzing

The marshal module provides a serialization mechanism for Python values. In other words, the module contains functions for writing/reading Python objects in a binary format. Unfortunately the format is undocumented, and Python maintainers may change the format in backward incompatible ways between Python version. The marshal module is used internally by other Python components, for example, for reading and writing .pyc files which contain pseudo-compiled Python code. But Python also has public API to access this serialization mechanism.

This post shows how the marshal module can be quickly tested with a simple dumb fuzzer, and why the module shouldn’t be used with untrusted data.

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