[Reverse Engineering] Beating a trial on a .net crackme

Today we are dealing with yet another .net crackme. Let’s see how it goes…

The crackme is a sort of X-times usage trial. After we’ve opened the executable 10 times we have the opportunity to test if we cracked the trial or not.

testing the trial validation

Using dotPeek we can decompile the binary, search for the class that is in charge of keeping track of the trial.

Using dnSpy we can not only inspect the binary but patch the code with ease. If we change the validation being made on this line in a way it can never be true we’d effectively cracked the binary.

And so I did, changing the hardcoded 9 to a 0 makes the validation useless as it could never be true.

Now we can start the binary as many times as we want without any issues!



InfoSec Write-ups

A collection of write-ups from the best hackers in the…

Syscall59 — Alan Vivona

Written by

Golang, Python, Javascript, Linux & Infosec. https://twitter.com/syscall59

InfoSec Write-ups

A collection of write-ups from the best hackers in the world on topics ranging from bug bounties and CTFs to vulnhub machines, hardware challenges and real life encounters. In a nutshell, we are the largest InfoSec publication on Medium. Maintained by Hackrew

Syscall59 — Alan Vivona

Written by

Golang, Python, Javascript, Linux & Infosec. https://twitter.com/syscall59

InfoSec Write-ups

A collection of write-ups from the best hackers in the world on topics ranging from bug bounties and CTFs to vulnhub machines, hardware challenges and real life encounters. In a nutshell, we are the largest InfoSec publication on Medium. Maintained by Hackrew

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