just finished reversing a custom virtual-machine based protector for a private tool. the opcode mapping was randomized and it used a stack-based architecture.
how i did it:
i used a custom debugger script to trace every single instruction and build a frequency map of the opcodes. once i identified the 'dispatch loop', i was able to reconstruct the original logic.
the takeaway:
never rely on standard protectors like Themida or VMProtect without custom settings. i can crack standard VMP in less than an hour, but a well-written custom VM can take weeks.
anyone here working on their own VM protector? i'd love to swap some ideas on instruction randomization.
reverse engineering custom vm obfuscation: a deep dive
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Wednesday at 08:10 AM
#1
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Wednesday at 08:25 AM
#2
cracking themida in an hour? mate u r a legend lol :D
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Wednesday at 08:40 AM
#3
standard protectors are just a 'speed bump' for real reversers lol
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Wednesday at 09:15 AM
#4
wat tool u using for the trace? x64dbg or ida pro?
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Wednesday at 09:30 AM
#5
ida pro with some custom python scripts mate. nothing beats ida for deep analysis :D
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Wednesday at 09:45 AM
#6
ida is expensive tho lol. any cheap alternatives mate?
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Wednesday at 10:00 AM
#7
u can use ghidra mate. it's free and actually very powerful lol :D
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Wednesday at 10:15 AM
#8
ghidra is cool but the decompiler is not as good as ida mate :/
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Wednesday at 10:30 AM
#9
true, ida is still the king for a reason $$$
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Wednesday at 10:45 AM
#10
lol 'expensive' is just a perspective if u have the right cracks mate :D
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Wednesday at 11:00 AM
#11
cracking the cracker. meta lol
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Wednesday at 11:15 AM
#12
how do u handle the opcode randomization? it changes every build lol
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Wednesday at 11:30 AM
#13
u need to build a template for the dispatch loop mate. then u just map the new opcodes to the template :D
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Wednesday at 11:45 AM
#14
template mapping is smart $$$
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Wednesday at 12:00 PM
#15
wat about the anti-trace features? some vms detect the debugger and change the flow lol
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Wednesday at 12:15 PM
#16
u need to use stealth debuggers like scyllahide mate. it hides the debugger from most vms :D
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Wednesday at 12:30 PM
#17
scyllahide is a classic lol
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Wednesday at 12:45 PM
#18
true, it's a must-have for any reverser $$$
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Wednesday at 01:00 PM
#19
nice thread. reversing is like a puzzle for me :D
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Wednesday at 01:15 PM
#20
puzzle with high stakes lol