Category Archives: Security

Here you can find posts about software security, vulnerability research, fuzzing, Java Security Libraries, and common security-related topics.

Global buffer overflow

There are a lot of articles, posts, and even books which describe a stack buffer overflow. There are a little less stuff about heap buffer overflows. But there is one more thing which you can overflow – buffers in global memory. Although all of those types of issues are very similar, let me try to fill this little gap with global buffer overflows.

Русская версия

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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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Accessing private fields with synthetic methods in Java

In Java, you can define one class B inside another class A. Class B is called an inner class, and class A is called an outer class. It looks like the following:

Class A has a private field “secret”. This private field can be accessed by both A and B classes. But in some cases, this private field can be accessed by other classes in the same package even if neither A or B provide any accessors. It actually depends on what we have in go() method.

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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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DNS tunneling with Java

DNS tunneling may help you to bypass a firewall if DNS requests are allowed. Or, it can just get you a free Wi-Fi. There are a number standalone tools which allow you to setup a TCP-over-DNS tunnel. Here is a simple implementation of DNS tunneling with pure Java. It’s not ready for using in real world, but it shows an idea how DNS tunneling can be implemented. The implementation works with standard JRE, and doesn’t require any additional library.

(русская версия – Java и свет в конце DNS туннеля)

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