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OpenZeppelin Upgrades

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Integrate upgrades into your existing workflow. Plugins for Hardhat and Truffle to deploy and manage upgradeable contracts on Ethereum.

  • Deploy upgradeable contracts.
  • Upgrade deployed contracts.
  • Manage proxy admin rights.
  • Easily use in tests.

Installation

Hardhat

npm install --save-dev @openzeppelin/hardhat-upgrades
npm install --save-dev @nomiclabs/hardhat-ethers ethers # peer dependencies
// hardhat.config.js
require('@openzeppelin/hardhat-upgrades');

Truffle

npm install --save-dev @openzeppelin/truffle-upgrades

Usage

See the documentation for each plugin, or take a look at the sample code snippets below.

Hardhat Truffle

Hardhat users will be able to write scripts that use the plugin to deploy or upgrade a contract, and manage proxy admin rights.

const { ethers, upgrades } = require("hardhat");

async function main() {
  // Deploying
  const Box = await ethers.getContractFactory("Box");
  const instance = await upgrades.deployProxy(Box, [42]);
  await instance.deployed();

  // Upgrading
  const BoxV2 = await ethers.getContractFactory("BoxV2");
  const upgraded = await upgrades.upgradeProxy(instance.address, BoxV2);
}

main();

Truffle users will be able to write migrations that use the plugin to deploy or upgrade a contract, or manage proxy admin rights.

const { deployProxy, upgradeProxy } = require('@openzeppelin/truffle-upgrades');

const Box = artifacts.require('Box');
const BoxV2 = artifacts.require('BoxV2');

module.exports = async function (deployer) {
  const instance = await deployProxy(Box, [42], { deployer });
  const upgraded = await upgradeProxy(instance.address, BoxV2, { deployer });
}

Whether you're using Hardhat or Truffle, you can use the plugin in your tests to ensure everything works as expected.

it('works before and after upgrading', async function () {
  const instance = await upgrades.deployProxy(Box, [42]);
  assert.strictEqual(await instance.retrieve(), 42);
  
  await upgrades.upgradeProxy(instance.address, BoxV2);
  assert.strictEqual(await instance.retrieve(), 42);
});

How do the plugins work?

Both plugins provide functions which take care of managing upgradeable deployments of your contracts.

For example, deployProxy does the following:

  1. Validate that the implementation is upgrade safe

  2. Deploy a proxy admin for your project (if needed)

  3. Check if there is an implementation contract deployed with the same bytecode, and deploy one if not

  4. Create and initialize the proxy contract

And when you call upgradeProxy:

  1. Validate that the new implementation is upgrade safe and is compatible with the previous one

  2. Check if there is an implementation contract deployed with the same bytecode, and deploy one if not

  3. Upgrade the proxy to use the new implementation contract

The plugins will keep track of all the implementation contracts you have deployed in an .openzeppelin folder in the project root, as well as the proxy admin. You will find one file per network there. It is advised that you commit to source control the files for all networks except the development ones (you may see them as .openzeppelin/unknown-*.json).

Note: the format of the files within the .openzeppelin folder is not compatible with those of the OpenZeppelin CLI. If you want to use these plugins for an existing OpenZeppelin CLI project, we will be sharing soon a guide on how to migrate.

Proxy patterns

The plugins support the UUPS, transparent, and beacon proxy patterns. UUPS and transparent proxies are upgraded individually, whereas any number of beacon proxies can be upgraded atomically at the same time by upgrading the beacon that they point to. For more details on the different proxy patterns available, see the documentation for Proxies.

For UUPS and transparent proxies, use deployProxy and upgradeProxy as shown above. For beacon proxies, use deployBeacon, deployBeaconProxy, and upgradeBeacon. See the documentation for Hardhat Upgrades and Truffle Upgrades for examples.

Managing ownership

Transparent proxies define an admin address which has the rights to upgrade them. By default, the admin is a proxy admin contract deployed behind the scenes. You can change the admin of a proxy by calling the admin.changeProxyAdmin function in the plugin. Keep in mind that the admin of a proxy can only upgrade it, but not interact with the implementation contract. Read here for more info on this restriction.

The proxy admin contract also defines an owner address which has the rights to operate it. By default, this address is the externally owned account used during deployment. You can change the proxy admin owner by calling the admin.transferProxyAdminOwnership function in the plugin. Note that changing the proxy admin owner effectively transfers the power to upgrade any proxy in your whole project to the new owner, so use with care. Refer to each plugin documentation for more details on the admin functions.

UUPS and beacon proxies do not use admin addresses. UUPS proxies rely on an _authorizeUpgrade function to be overridden to include access restriction to the upgrade mechanism, whereas beacon proxies are upgradable only by the owner of their corresponding beacon.

Once you have transferred the rights to upgrade a proxy or beacon to another address, you can still use your local setup to validate and deploy the implementation contract. The plugins include a prepareUpgrade function that will validate that the new implementation is upgrade-safe and compatible with the previous one, and deploy it using your local Ethereum account. You can then execute the upgrade itself from the admin or owner address. You can also use the proposeUpgrade function to automatically set up the upgrade in Defender Admin.

Community

Join the OpenZeppelin forum to ask questions or discuss about these plugins, smart contracts upgrades, or anything related to Ethereum development!

License

OpenZeppelin Upgrade plugins are released under the MIT License.