FruitFly's dropper script and its missing tricks

Note to original post:

This post was originally written back in May 2019 but was removed because of “pressure” from my employer at the time, Apple. It was written over the weekend on my own equipment and was all about information I had way before I joined Apple. Personally I don’t think there is any special drama here other than unreleased technical details about a malware that is dead and its author busted long time ago. When paranoia and envy are dominant then everything can be a potential media drama in people’s mind. It’s all bullshit. My position didn’t change and given that there is an upcoming presentation about this malware by Thomas Reed at Objective By The Sea it’s time to re-release this.


While sorting out my Mac malware collection I found out that I had an unreleased (no known public references) FruitFly/Quimitchin dropper script lost in my archives.

FruitFly made big headlines two years ago and its author has been arrested. It was first reported by MalwareBytes and then a new variant was analysed by Patrick Wardle. Besides being under the radar for more than a decade, it was kind of exotic malware because most of its code was written in Perl. Last time I did something serious in Perl was twenty years ago or so!

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Why I Left Twitter

Because I can :-) I was going to write a longer post about this but it is pretty much irrelevant. Essentially I have been thinking about this over the past weeks given that my character might be somewhat incompatible with what I want to achieve next. Sunday I got locked out of Twitter because some random asshole made an harassment complaint because I called him “dumb fuck” and “dumb idiot”, pretty normal things around my feed. [Read More]

How to make LLDB a real debugger

These days the de facto debugger in macOS is LLDB. Apple’s old gdb fork doesn’t work anymore and the GNU gdb version is better these days but still quite meh (in the past it couldn’t deal with fat binary targets and I still think this holds true). So we are all essentially stuck with LLDB, warts and all. I also hate the lack of a gdbinit style output but Deroko started that project and I improved it with lldbinit.

Besides its horrible long command line syntax which is so unpopular that gdb-compatible commands were introduced, my biggest problem with it has been the lack of x86 hardware breakpoint support. While hardware breakpoints might not be needed to debug applications within Xcode, they are essential to any serious reverse engineer dealing with arbitrary untrusted targets such as malware, packers, obfuscators, and DRM. It has been a serious blocker for me against some targets and a source of immense frustration because it should be a basic debugger feature.

Last week I finally got fed up enough to dive into the LLDB C++ codebase and finally try to implement this feature. Instead of just posting a patch, this post is a journey into LLDB internals and how I implemented this feature. Hopefully it will help others exploring the LLDB codebase, which seems unfriendly because of the lack of really good documentation into its architecture. Maybe this could lead to further improvements and make LLDB more reverse engineer friendly.

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Crafting an EFI Emulator and Interactive Debugger

In 2016 I reversed Apple’s EFI firmware password reset scheme using SCBO files. There was an old rumor that these files were able to unlock firmware password locked Macs (and even a sketchy video about a universal SCBO able to unlock any Mac). That post is available at Apple EFI firmware passwords and the SCBO myth.

All the interesting computing action happened at the EFI execution level. I made good reversing progress with static analysis, but dynamic analysis with a debugger would make the job much easier. I love debuggers because they allow you to quickly test ideas and cut corners while reversing a target. Reading disassembly listings for long periods is tiring. (U)EFI debuggers can be found in the market but they are usually quite expensive (a couple thousand USD).

My solution was to create an emulator and debugger based on Unicorn. At the time I was working a lot with Unicorn so it was natural to use it to solve this problem (“if all you have is a hammer, everything looks like a nail”). After I wrote the blogpost some people directed me to some emulators (TianoCore EmulatorPkg and efiperun). I never tried them to see if they contained an interactive debugger like I wanted. The pain wasn’t big since this was a couple of days project and it was quite fun to write.

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Keygenning Carbon Copy Cloner Keychain Password

Passwords are a modern annoyance and their diversity is something you can’t avoid if you want a minimum amount of account security (don’t forget to turn on those 2FA options, avoiding SMS versions if possible). They get more annoying when you set a super smart new password with that smug feeling that it is such a great password that you will never forget about it (or something crappy you set in a rush). [Read More]

Reversing and Keygenning qwertyoruiop's Crackme

I was bored this weekend and decided to take some rust out of my reversing skills before they disappear for good. I have spent the past two years or so mostly writing C code (secure C is more like an asymptote but that is why it is a fun challenge) and barely doing any serious reverse engineering and security research. So I decided to revisit some unfinished business with qwertyoruiop’s crackme. I had a look when he originally sent it but got distracted with something else at the time and never finished it. I couldn’t find any public write-up about it so I decided to write one. It is mostly targeted to newcomers to reverse engineering and macOS. You can click the pictures to see the full size version.

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lldbinit - Improving LLDB

Many years ago I had to use gdb for the first time and I absolutely hated it. At the time I was reversing (cof cof cof) Windows apps so SoftIce and friends were my favorite tools. Compared to these gdb was a complete trash, mostly because the naked gdb lacks a nice context display. I like to know what the hell is going around each time I step in the debugger, without having to type a bunch of commands for it. [Read More]

Measuring OS X Meltdown Patches Performance

Happy New Year and happy ten year anniversary to this blog, which I totally forgot back in October :-/. Blogging activity here has been so slow that I almost forgot how to work with Hugo. We started 2018 with heavy speculation on critical CPU bugs that were under disclosure embargo. Luckily for us, Google decided to break the embargo and release some proper information about the bugs so speculation could stop and facts could finally flow in. [Read More]

Exploiting CVE-2017-5123

This is a guest post by a young and talented Portuguese exploiter, Federico Bento. He won this year’s Pwnie for Epic Achievement exploiting TIOCSTI ioctl. Days ago he posted a video demonstrating an exploit for CVE-2017-5123 and luckly for you I managed to convince him to do a write-up about it. I hope you enjoy his work. Thanks Federico! While this one was on a rush, I want to create another blog dedicated to Portuguese hackers and researchers content. [Read More]

How to compile AFL's LLVM mode in OS X

American fuzzy lop aka AFL is one of the easiest and best fuzzers out there and should be part of your development cycle if you care at least one bit about the security of your code. Its performance in OS X is a bit of a let down because of issues at fork() system call. AFL warns you about this when compiling it: WARNING: Fuzzing on MacOS X is slow because of the unusually high overhead of fork() on this OS. [Read More]