CodeHawks Escrow Contract - Competition Details

Summary

Enum is used in Escrow contract for managing various states of functions. But Enums are gas expensive and it can be done cheaper by using constants. One of the examples of using constants instead of enums is Openzeppelin's ReentrancyGuard.sol contract.
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/security/ReentrancyGuard.sol

Vulnerability Details

It costs so much less gas to read and write constant values than reading and writing from Enums.

Savings

Savings for confirmReceipt function:

Savings for initiateDispute function:

Savings for resolveDispute function:

Tools Used

Manual Analysis and Gas Savings are calculated via $ forge test --gas-report

Implementation

Implementing constants in place of Enum in Escrow contract requires quiet a bit of refactoring in Escrow.sol, IEscrow.sol and EscrowTest.t.sol. But for testing purposes, I have already modified all these contracts and they can be found here: https://github.com/0xSandip/EscrowGasChanges

Basically what i did was:

1. Made new constants:

2. Made a new state variable to keep track of the state:

3. Initialized the s_state as CREATED in the constructor:

4. Changed the inState modifier:

and modified all the instances of the state and values everywhere in the Escrow, IEscrow and EscrowTest.t.sol contract which can be referenced from the above link.