Basic exercise to get started with ZeppelinOS

Setup

The first thing you should do is to install zos.

npm install -g zos

Then, follow the subsequent commands to setup the exercise project:

git clone [email protected]:zeppelinos/zos-ethberlin-exercise.git
cd zos-ethberlin-exercise
npm install

Exercise

The idea of this exercise is to fix a bug on a contract using ZeppelinOS upgradeability. In the contracts directory you will find a contract called MyWallet with a bug. The idea would be to deploy an instance of the MyWallet contract as if we wouldn't have known it had a bug, and then upgrade it using ZeppelinOS!

We recommend doing this exercise in a local network, you can start a new one running npx truffle develop

Then open a new console and follow the next steps:

1. Buggy contract

The first step would be to create an instance of our buggy contract as if we wouldn't have known it had a bug. To do that we will use the following commands of zos:

zos add MyWallet
zos push --network local
zos create MyWallet --network local

As you can see, a new zos.local.json including all the data of the contracts of your project. You can check your buggy contract running the following commands over the truffle console:

walletAddress = require('./zos.local.json').proxies['MyWallet'][0].address
wallet = MyWallet.at(walletAddress)

someone = web3.eth.accounts[0]
wallet.initWallet(someone)
wallet.owner().then(r => owner = r)
owner === someone // true

anotherone = web3.eth.accounts[1]
wallet.initWallet(anotherone)
wallet.owner().then(r => owner = r)
owner === anotherone // true

As you can see, our instance has a bug, let's fix it...

2. Fix the bug

Once you have created the first instance of MyWallet it's time to realize it had a bug and fix its code. If you don't recognize the vulnerability, you can run the tests with npm test. You will see that one of them is failing. Let's now fix it! Make sure all your tests pass by running npm test.

3. Upgrade your contract with the bugfix

To upgrade your MyWallet instance run the following commands:

zos bump 0.1.1
zos add MyWallet
zos push --network local
zos upgrade MyWallet --network local

Now let's try the same commands over the truffle console to check our contract instance has been upgraded correctly.

walletAddress = require('./zos.local.json').proxies['MyWallet'][0].address
wallet = MyWallet.at(walletAddress)

someone = web3.eth.accounts[0]
wallet.initWallet(someone)
wallet.owner().then(r => owner = r)
owner === someone // true

anotherone = web3.eth.accounts[1]
wallet.initWallet(anotherone) // revert!

As you can see, the bug has been fixed!