BlockchainC2

BlockchainC2 is a small POC server/agent to assess how the Blockchain (specifically Ethereum's Smart Contract functionality) can be used by an attacker for C2.

Details regarding this application can be found here.

Smart Contract

The Smart Contract used within this POC is quite simple:

pragma solidity ^0.5.0;

contract EventC2 {

    address owner;

    event _ServerData(bool f, bool enc, int seq, string agentID, string data);
    event _ClientData(bool f, bool enc, int seq, string agentID, string data);

    constructor() public {
        owner = msg.sender;
    }
    
    function AddClientData(string memory agentID, string memory d, int id, bool f, bool enc) public {
        emit _ClientData(f, enc, id, agentID, d);
    }

    function AddServerData(string memory agentID, string memory d, int id, bool f, bool enc) public {
        emit _ServerData(f, enc, id, agentID, d);
    }
}

The focus of this Solidity code is to pass events between a server and multiple clients in the form of events.

Building

BlockchainC2 was designed to be run on MacOS/Linux, but the agent can be compiled to execute on MacOS, Windows, or Linux.

To build on MacOS using brew:

# Install solidity and ethereum
brew tap ethereum/ethereum
brew install ethereum
brew install solidity

# Build
make all

To build on Ubuntu:

# Install solidity and ethereum
sudo add-apt-repository ppa:ethereum/ethereum
sudo apt-get update
sudo apt-get install solc ethereum

# Build  
make all

To cross-compile an agent for Windows:

CGO_ENABLED=1 CC="x86_64-w64-mingw32-gcc" GOOS=windows go build blockchainc2/cmd/bc2agent

Running

You will need to setup an account which can be used by the server component. The easiest way to do this is with geth:

geth account new --keystore /tmp/mykeystore/
cat /tmp/mykeystore/*

Ether can be added to your wallet on the Ropsten testnet using https://faucet.ropsten.be/.

Add the keychain to your config.json, for example:

{
	"Key": "{\"address\":\"ADDRESS\",\"crypto\":{\"cipher\":\"aes-128-ctr\",\"ciphertext\":\"CT\",\"cipherparams\":{\"iv\":\"IV\"},\"kdf\":\"scrypt\",\"kdfparams\":{\"dklen\":32,\"n\":262144,\"p\":1,\"r\":8,\"salt\":\"06470fcc2121994e014f85e5ab9cdb3714c76b873a1f1186c3e623e87abc4a7a\"},\"mac\":\"SALT\"},\"id\":\"ID\",\"version\":3}",
	"Endpoint": "wss://ropsten.infura.io/_ws",
	"ContractAddress": "TODO_VIA_SETUP",
	"GasPrice": 0
}

To deploy a contract using bc2server:

./bin/bc2server -config ./config.json -pass Passw0rd -setup

Once the contract has been deployed, add the address to your config.json and start the server with:

./bin/bc2server -config ./config.json -pass Passw0rd

With the server running, agents can be attached using:

./bin/bc2agent -config ./agent_config.json -pass Passw0rd

It is recommended that a fresh account is used for an agent to avoid errors with pending transactions.