You are browsing the archive for Trivia.

Yara to spellcheck’em all

November 24, 2019 in Tips & Tricks, Trivia

This is a trivial yara rule stub. It picks up binaries with mispeleleleled words. I have started putting it together only yesterday when I noticed that many of popular (and often signed) binaries include lots of these. This suggests the coders are non-native speakers. The more far-fetching scenarios could include automatic checks against APT for popular misspellings to quickly highlight a possible attribution hints or… a false flag 🙂

Improve at your own risk 🙂

rule mispel
{
    strings:
        $s1 = "appling" ascii wide
        $s2 = "runing" ascii wide
        $s3 = "youre" ascii wide
        $s4 = "faild" ascii wide
        $s5 = "suces" ascii wide
        $s6 = "seting" ascii wide
        $s7 = "opend" ascii wide
        $s8 = "seqence" ascii wide

    condition:
        (1 of ($s*))
}

Batch decompilation with IDA / Hex-Rays Decompiler

July 4, 2019 in IDA/Hex-Rays, Random ideas, Reversing, Silly, Tips & Tricks, Trivia

if you are very used to 32-bit IDA you may sometimes find yourself in a blind alley when you try to port your working solution to IDA 64-bit. This was the case with my old batch decompilation script.

The way it works is very simple – for every <file> in a folder, run IDA in its automation/batch mode mode, decompile the <file>, and finally save it in a <file>.c file – more or less like the below (I am omitting the loop):

c:\Ida\idaw.exe -A -Ohexrays:-new:%%k.c:ALL “%%k”

Nothing could be simpler.

Until you run it with the 64-bit idaw64.exe:

c:\Ida\idaw64.exe -A -Ohexrays:-new:%%k.c:ALL “%%k”

It doesn’t work. It loads idaw64 and just stays there.

The gotcha is in a plug-in name. The 64-bit decompiler’s plugin name is not hexrays, it’s not hexrays64 either. It is actually hexx64.dll.

So, you have to run this instead:

c:\Ida\idaw64.exe -A -Ohexx64:-new:%%k.c:ALL “%%k”

It’s ridiculously trivial, but it’s always the little things.

Also, interestingly, when you google hexx64.dll or hexx64.p64 you only get a few hits. As if not too many ppl ever came across the issue.

Another gotcha is that if you run it with too many files, your system’s performance will deteriorate quickly. I don’t know if it is memory fragmentation/leaks, or something else, but after running the script on a number of samples I observed my VM dying on me and requiring a restart due to low memory (despite no other process running on a 2G RAM guest). If you know what causes it I would be grateful if you could let me know.

The third gotcha is to rely on the text version of IDA for this task – it is faster than the GUI version. At least in my experience.

Finally, the last gotcha is to remove all the other plugins from the IDA’s Plugins directory, other than the one you are using e.g. hexrays. Why? This may look like nothing, but IDA enumerates and loads all of them _each_ time it starts.