CTF Write-Up: Ether
- CTF challenge available at ctf-mystiko.com.
- Challenge name: Ether
- Category: Web
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Challenge description:
Description:
Dear insider users
Welcome to the Mystiko Ethereum mining farm. We are still running some tests before we go live.
Please, let us know if you can find any problems ASAP, so we can fix them before moving to the Ethereum network.
Thanks,
- dh0ck
Solution:
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The attached file is a postman request:
We can see that the request is reaching a supposed “ethereum farm” with many nodes, to check their status. There is one node (846) with a special result, we should be able to find it by fuzzing the node parameter:
This would represent that the node 846 mined an Ether. We can see the transaction ID. We must combine that with the knowledge from the postman file, that mentions the Rinkeby nodes, to be able to research what is Rinkeby, and realize that it’s not the official ethereum network, but a test network.
We can search the transaction there, on
https://rinkeby.etherscan.io/tx/0xf4ab9a4a8a638ee4a8f84f0f5bd01aef2d46253ef3a1303bad31c0a08685484e
in the lower part we can see the flag as UTF-8
There are countless tutorials out there on how to use the Rinkeby network and create a transaction or contract there, so I will not cover that here.
