This post is written for aspiring reverse engineers and will talk about a technique called _API hashing_. The technique is used by malware authors to hinder reverse engineering. We will first discuss the reasons a malware author may even consider using API hashing. Then we will cover the necessary technical details around static and dynamic imports and finally, we will described API hashing and show a Python script that emulates the hashing method used in Sodinokibi/REvil ransomware. Read on
Earlier this year, I was thrilled to hear that my submission for a talk at this year's [FrOSCon](https://www.froscon.de/) (Free and Open Source Software Conference) was accepted. [The talk](https://programm.froscon.de/2019/events/2350.html) is about Ghidra, the reverse engineering tool which was recently release into open source by the NSA. Since I expected a very heterogeneous audience with people from all kinds of industries with all kinds of backgrounds, I decided to give a long introduction with a lot of motivation for reverse engineering and only use the last quarter or so of the talk to actually show Ghidra's capabilities. You can find the [slides here](https://blag.nullteilerfrei.de/wp-content/uploads/2019/08/FrOSConTalk2019-Ghidra.pdf), the source [of the slides on github](https://github.com/larsborn/FrOSCon2019-Ghidra-Talk) and a recording at [media.ccc](https://media.ccc.de/v/froscon2019-2350-ghidra_-_an_open_source_reverse_engineering_tool). Based on feedback after and during the talk, I added a bullet point under Motivation: a lot of people at FrOSCon seemed to be in the position where a wild binary blob appeared and they had to deal with it. Some because they found an old service running with source code not available (or readable) anymore and some because they want to re-implement a protocol that is not documented.
Say you want to write a C program, but you want to avoid including plain strings within the binary. This is something often done by malware authors, for example, to avoid easy extraction of so called indicators of compromise. I can also imagine a legitimate business that uses string obfuscation to make reverse engineering of their software harder to protect their intellectual property. This is often called string obfuscation. I want to use this knowledge to make the world a better place!
a.k.a. "My Bank does not support CSVs". When I asked my bank for "machine readable" versions of my bank statements, they where like: Their website has a CSV-export function. But only data from the last three months can be exported. Of course, it would have been smart to have performed this export every two months or so, but let's talk about something else. Sure!
I started to play around with ArangoDB and used Python to get some data into my first database. Long story short: if you want to set your own key for the documents, do it on the document, not on the initialization data. EDIT: this is only true for the most recent version 1.3.1 release on pypi by the time of writing1. Read the longer story!
Flask pretty-prints response generated by the
flask.json.jsonifyfunction. Avoiding this on a per request basis doesn't seem to be intended: There is a configuration variable for the whole application:
JSONIFY_PRETTYPRINT_REGULAR. But setting that to
Falseminifies every JSON responses. And, in general, I enjoyed the pretty printed output. So implementing
X-PrettyPrint- which seems to be a quasi-standard - also sounded like a the wrong way because it means replacing the call to
jsonifyby a custom implementation. This short story has a happy end though: Flask does not pretty-print the response if it receives an AJAX request. So one can just send the appropriate header:
curl -H 'X-Requested-With: XMLHttpRequest' "https://exmaple.com/api/endpoint.json";
I am not very disciplined. So trying not to be distracted while
working at my computer is a major project for me. Since "deep work" is en vogue, it is possible to disable notifications in nearly every app nowadays. But there are often tiny bits one cannot change: Slack's icon in the notification area is one of those things: Whenever you have an unread message in any of the channels you are part of, Slack will show a small blue dot on its icon in the notification area. One can argue that it is not that hard to ignore that but fishing is also not that hard and I cannot do it. What I can do though is overwrite
This blag post describes how to use a [Raspberry Pi](http://amzn.to/2wjICvo) to remotely "press" and potentially "hold" the power button on a PC. This is my first non-trivial (still pretty-trivial) hardware-related project. So don't expect anything too fancy. Would you like to know more?