tennisonchan / brownie-contract-upgrades

Brownie Contract Upgrades

Showcasing how to use proxy, TransparentUpgradeableProxy to achieve upgrading the contracts

• Smart contracts are immutable but it can be "mutable" for upgrade or bug fixing
• 3 methods for upgrading:
  • Parameterize
  • Migration
  • Proxies

Parameterization

• Cannot add new storage
• Cannot add new logic
• Simple but not flexible
• Who is the admin? than it'll be a centralized contract
• E.g. Contract registry
• Some argues we shouldn't do this https://blog.trailofbits.com/2018/09/05/contract-upgrade-anti-patterns/

Migration

• Deploy a new contract and tell everyone "this is a new one now"
• Truly immutable
• Easy to audit
• lots of education
• Different address
• How contract migration works https://blog.trailofbits.com/2018/10/29/how-contract-migration-works/

Proxies

• Use lots of low level functionality, like the delegatecall
• Delegatecall / Callcode and Libraries https://docs.soliditylang.org/en/v0.4.21/introduction-to-smart-contracts.html#delegatecall-callcode-and-libraries
• With the fallback function in Proxies contract, we can delegate our calls to a different contract

1. Implementation contract, has all the protocols. we launch a new implementation contract when we upgrade
2. Proxy contract, which points to the implementation contract
3. User, making calls to the proxy contract
4. Admin, who can upgrade the contract

Potential Issues

• Storage clashes
  • Delegated function only storage value based on position, not by variable name
• Function selector clashes
  • The clashes of the functions with the same function selector in both implement contract and the proxy contract

Transparent Proxy Pattern

• ProxyAdmin https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/proxy/transparent/ProxyAdmin.sol
• TransparentUpgradeableProxy https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/proxy/transparent/TransparentUpgradeableProxy.sol
• Admin cannot call implementation contract functions
• Admin can only call the functions that govern the upgrades in the proxy contract

Universal Upgradable Proxies (UUPS)

• AdminOnly upgrade functions are in implementation contract
• Saving Gas
• Proxy contract is smaller

Diamond Proxies, Multi-Facet Proxy

• https://eips.ethereum.org/EIPS/eip-2535