CodeHawks Escrow Contract - Competition Details
Cyfrin
Foundry
40,000 USDC
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Submission Details
Severity: gas

STATE VARIABLES SHOULD BE CACHED IN STACK VARIABLES RATHER THAN RE-READING THEM FROM STORAGE

hunter_w3b

Summary

There is an opportunity to optimize gas consumption by caching the i_tokenContract state variable in a stack variable. By caching the state variable in a local variable, we can reduce the number of read operations from storage, resulting in potential gas savings.

Vulnerability Details

https://github.com/Cyfrin/2023-07-escrow/blob/main/src/Escrow.sol#L109-L129

function resolveDispute(uint256 buyerAward) external onlyArbiter nonReentrant inState(State.Disputed) {
uint256 tokenBalance = i_tokenContract.balanceOf(address(this));
uint256 totalFee = buyerAward + i_arbiterFee; // Reverts on overflow
if (totalFee > tokenBalance) {
revert Escrow__TotalFeeExceedsBalance(tokenBalance, totalFee);
}
​
s_state = State.Resolved;
emit Resolved(i_buyer, i_seller);
​
if (buyerAward > 0) {
i_tokenContract.safeTransfer(i_buyer, buyerAward);
}
if (i_arbiterFee > 0) {
i_tokenContract.safeTransfer(i_arbiter, i_arbiterFee);
}
tokenBalance = i_tokenContract.balanceOf(address(this));
if (tokenBalance > 0) {
i_tokenContract.safeTransfer(i_seller, tokenBalance);
}
}

Recommendations

diff --git a/resolveDispute.sol b/resolveDispute.org.sol
index f3e8cab..fcbc3e3 100644
--- a/resolveDispute.sol
+++ b/resolveDispute.org.sol
@@ -1,6 +1,5 @@
function resolveDispute(uint256 buyerAward) external onlyArbiter nonReentrant inState(State.Disputed) {
- IERC20 tokenContract = i_tokenContract; // Cache state variable in a stack variable
- uint256 tokenBalance = tokenContract.balanceOf(address(this));
+ uint256 tokenBalance = i_tokenContract.balanceOf(address(this));
uint256 totalFee = buyerAward + i_arbiterFee; // Reverts on overflow
if (totalFee > tokenBalance) {
revert Escrow__TotalFeeExceedsBalance(tokenBalance, totalFee);
@@ -10,13 +9,13 @@
emit Resolved(i_buyer, i_seller);
if (buyerAward > 0) {
- tokenContract.safeTransfer(i_buyer, buyerAward);
+ i_tokenContract.safeTransfer(i_buyer, buyerAward);
}
if (i_arbiterFee > 0) {
- tokenContract.safeTransfer(i_arbiter, i_arbiterFee);
+ i_tokenContract.safeTransfer(i_arbiter, i_arbiterFee);
}
- tokenBalance = tokenContract.balanceOf(address(this));
+ tokenBalance = i_tokenContract.balanceOf(address(this));
if (tokenBalance > 0) {
- tokenContract.safeTransfer(i_seller, tokenBalance);
+ i_tokenContract.safeTransfer(i_seller, tokenBalance);
}
}
​

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