Monday, May 11, 2009

Concept Art

Some concept art for a project I'm working on with my oldest son. He's the artist, not I.

The Mac Hacker's Handbook

The Mac Hacker's Handbook is the best reference for Mac-specific attack information that I have found. At 368 pages, it may appear small compared to the typical 750+ page security tome. That's because the authors have done a near-perfect job of sticking to the topic at hand, the Mac. The authors do not succumb to the usual temptation to try and teach assembly language or reverse engineering. Rather, they do an excellent job touching on those topics in an OS X context, and assume the reader has a little background in that area already, or can otherwise keep up. I have done some limited research into the areas of Mac malware and process injection in the past. This book has done a fantastic job of filling in many holes in my knowledge that I hadn't been able to take care of before. Plus, it introduced me to a number of Mac-specific security features I wasn't aware of before. Highly recommended for anyone interested in Mac security.

Detailed commentary follows.

The authors Charlie Miller and Dino Dai Zovi have impressed me on several levels.

A couple of years ago, I did a presentation of Mac malware, where I researched some similar areas on my own. The purpose of my talk was to demonstrate that the privilege separation on a typical single-user OS X box made no difference, because an attacker could do everything they need from user mode.

My skills are somewhere between beginner and intermediate in the areas of programming, reverse engineering, vulnerability research and exploit writing. With a lot of work, I was able to create a very crude keyboard sniffer by attaching a library to launched processes. In one chapter (chapter 11), this book spelled out everything I needed to know and more. And implements several useful injected components in a much more flexible way than I was able to. I could have really used this information then.

I ran across many of the same libraries and examples that the authors reference in the book. However, they were mostly code examples with no context, intended to be groked by hard-core Mac programmers. Here, they are presented in an actual understandable way, building on examples as they go. It makes a huge difference. The level of writing meshed perfectly with my past knowledge and filled in the holes I had. I have an advantage over a rank beginner, but I suspect they have reached as wide an audience as is possible with their writing.

They do this consistently throughout the book. And this is what really made this an excellent book for me, was the actual writing. You'll have to excuse me if I geek out a little bit on this topic, but I've written a few technical books myself, and I have a great appreciation for how hard it is to do this well.

There are many traps one can fall into when writing a book like this. A lot of the topics are circular. As in, it's difficult to pick a sane order to follow, and not repeat a lot of information. There's always a temptation to try and show off advanced topics, and not adequately cover the intro material. It's easy to get lazy and not put the time into explaining a concept, assuming everyone knows it. Authors sometimes dump a lot of pictures and code on the reader for length.

These authors fell for none of these. The ordering of topics and advancing difficulty seem ideal. Code is almost uniformly useful and well-documented. They don't beat you over the head with example after example for the same topic. Rather than attempting to include a complete PowerPC and x86 instruction reference, they give you the minimum set of instructions that they used. The pacing was great. I was neither bored reading things I knew, nor unable to keep up with the material (until I struggled slightly to absorb the last chapter or two.)

Production values are good. The price is great, the length is very appropriate. Editing is good. (Not perfect; I spotted a dozen very minor typos. But then, I can't turn off my internal proofreader anymore, you're unlikely to notice most if any of those.)

There are other minor things to appreciate if you've been around vulnerabilities and exploits for a while. I feel like they did a great job explaining heap exploitation, compared to other attempts I've read. I very much enjoyed the little bits of history when they discuss who pioneered a particular technique. Most of Dino's code has a date in the comments, so you have some idea what was known at the time.

I'd go so far as to say that this book really is a general book about how to find and exploit vulnerabilities, using the Mac as your research platform. And it turns out that the Mac is a great place to learn.