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Sunday, July 29, 2007

Book Review: Fuzzing: Brute Force Vulnerability Discovery



Fuzzing: Brute Force Vulnerability Discovery

By Michael Sutton, Adam Greene, Pedram Amini

“Great on Theory…Pretty Good on Execution”

Four Stars

I anxiously awaited reading and putting this book to use. Fuzzing is one of those “mystical” concepts that the people cranking out exploits were doing and I wanted to be able to use some of the publicly available fuzzers to fuzz for vulnerabilities and join the ranks.

From the back cover: “…Now, its your turn. In this book, renowned fuzzing experts show you how to use fuzzing to reveal weaknesses in your software before someone else does.”

I thought the book excellently covered the theory portions of fuzzing. The format of theory/background of a fuzzing method (Environment Variable and Argument Fuzzing, Web Application and Server fuzzing, File Format Fuzzing, Network Protocol Fuzzing, Web Browser Fuzzing, and In-Memory Fuzzing) followed with that fuzzing method Automation or on Unix and then on Windows worked perfectly. It was a good structure and informative. The Automation or Unix and Windows sections fit in well with the theory sections before it.

I think the book falls a bit short on practical execution (case studies) of using the fuzzing tools. Granted I say this based on my own expectations of what I would like to see from a fuzzing book but also from what the authors say in the preface that we will get out of the book. They say, “We detail numerous vulnerabilities throughout the book and discuss how they might have been identifies through fuzzing.” Some of the case studies are exactly what I expected like case studies in Chapter 10, the fuzzing with SPIKE section in Chapter 15, and the Complete Walkthru with Sulley in Chapter 21. Some of the others fall a bit short. I expected a lot more out of the ActiveX fuzzing sections (chapter 18), the Shockwave Flash example in Chapter 21 was useful for the discussion of creating a test case for a protocol but after 11 pages of mostly code in the last section we basically get told to load it into PaiMei and “go fuzz”, and while the theory parts of chapter’s 7 & 8 were great, telling me to find an AIX 5.3 box to see some example environment variables and argument vulnerabilities was less than useful. It would have been much more useful to use some of today’s fuzzing tools to find some old vulnerabilities in something like *BSD or old RedHat distributions, something I might have in the lab or at least something I could install in VMWare.

Likes: Theory, background, discussion of how and why they built the “author built” fuzzers they cover in the book, some of the case studies gave me everything I needed to reproduce on my own in the lab. Providing the fuzzers on the companion website was great as well. The George Bush quotes were hilarious as well and made me look forward to each chapter so I could get another quote.

Dislikes: some of the case studies I don’t think went into enough detail (no step by step instructions), I think the explanations of the blocks of code could have been better and numbering lines so we could refer to them in the text would have helped. The discussion of the existing frameworks was a little bit light (but we do get told to go the companion website for more info). Ideally we would have walked thru a couple of easy examples using multiple fuzzer frameworks to get us from advisory to EIP= 0x41414141. That would have been nice to see.

Overall a great book, it has a place on the bookshelf next to shellcoder’s handbook and some other programming books and it will be used (many times) as a reference to play with the various fuzzers available out there.

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