Thursday, December 16, 2010

Conquering my Qt fears and semester results

The three main goals I was hoping to accomplish this semester:
-Architecture improvements, especially regarding a plugin system
-License scanner
-Get a basic fully functional GUI

Most of the semester focused on objective 1 and I think I did fairly well in that regard. I feel there is at least a solid foundation for a plugin system and additional interfaces will be added as needed. Regarding objective 2, I didn't get the full application I was hoping to due to various issues, but I did improve the FLIRT support and wrote a research paper on the limitations of FLIRT demonstrated using my toolkit and verifying against IDA. I'll hopefully be releasing it soon, ask me for a draft if you'd like to see it. Right now its titled "Issues with FLIRT Aware Malware." Back to the objective, I honestly just didn't put the effort into accomplishing objective 2. After seeing a lot of the issues with FLIRT, I also wasn't sure if it really was a good function recognition algorithm to spend time creating signatures for. Presumably though, I can automatically create signatures once I gather up the libraries, so it might not be such a big deal.

I did get a basic GUI going, but not to the level I was hoping to. Several things got in the way of this. First, I knew it was a risk that I didn't know Qt very well. I wouldn't say that I know it well yet, but I'm beginning to become competent. Second, someone offered some help, but didn't follow through. This made me focus on other things hoping they were going to help me get a code example of the widget I needed. I did get some help here and there and one of the main things that became clear was that I needed to subclass QAbstractScrollArea for proper support.

So what was the widget I needed? Basically, rendering all of the disassembly area ahead of time had numerous issues. It took too much time to render ahead of time, a pain to keep track of position, and more. The solution: a custom widget that intelligently rendered on demand as the window is scrolled. The problem: the limited Qt work I did was through Qt designer using stock widgets.

Maybe this wouldn't have been so bad if I at least had done work with other GUI frameworks and knew what phrases like model view controller (MVC) meant. As an example, I was referenced to the Okteta KDE project which has a widget very similar to what I needed. However, while the code seems to be designed well, there were several issues. First, it was designed to work as a library, but I wasn't really sure how to build it as it was in some KDE/CMake build system hybrid or something. I don't know CMake and get confused easily when "cmake ." or w/e doesn't work due to some error message. This isn't a huge deal because, all things considered, there were that many files and I could just use my own build script. It is somewhat annoying though that I have this library installed on my computer, but there seems to be no -dev package for it. Second, it used a very flexible enterprise style model view controller design. Normally this would be a solution and not a problem, but I don't really know MVC, so it didn't work out well. This may have been solved as I realized there was a Qt designer plugin for their widgets. Unfortunately, the dependencies seemed to explode for it and I didn't get a chance to try to finish it. Before I was importing source files as needed, I may instead just import the entire project (a couple hundred source files I think).

One of the things as I was doing more and more of this was that there were actually two distinct problems of implementing my widget. The first was that I needed to understand QAbstractScrollArea itself. That is, how the viewport object worked and such. Second, I needed to learn how to make a widget to display hex to set to the viewport. Part of my confusion on this was the what I'd consider a poor example of QAbstractScrollArea: a widget that scrolls another widget. This functionality was too linear and didn't really help one not really familiar with Qt what was really going on.

To fix some of these problems, I've been trying to read up on more Qt stuff such as MVC architecture. As I was reading through one of the examples, codeeditor, I quickly realized this strangely may show what I need to solve my problems despite looking quite different than what I was looking for. They key has to do with the line numbering on the side. I think I ran into this example before, but maybe didn't realize the significance. This widget demonstrates two things: how to render a text based widget and how to use the viewport. This is essentially exactly what I need to get my application rolling. I may consider some point in the future to use something like the Okteta library, but for now I think I finally have the starting point I need to develop my widgets and at least get something working. I'd like to write a small tutorial on harnessing QAbstractScrollArea for beginners as I really think there could have been a better example for it.

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