Fraxlend (Frax Finance) contest - sach1r0's results

Non-Library/Interface files should use fixed compiler versions, not floating ones

Details

Contracts should be deployed with the same compiler version/flags where they have been tested with. Locking the pragma helps to ensure that contracts do not accidentally get deployed using an outdated compiler version that might introduce bugs that affect the contract system negatively. see reference: https://github.com/code-423n4/2021-11-unlock-findings/issues/15, https://code4rena.com/reports/2022-03-paladin/ and https://swcregistry.io/docs/SWC-103

Mitigation

I suggest removing ^ in pragma solidity ^0.8.15 and change it to pragma solidity 0.8.15 to be consistent with the rest of the contracts.

Line of code

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L2 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/VariableInterestRate.sol#L2 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L2 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairConstants.sol#L2 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L2 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L2 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L2

Breaking down multiple require statements instead of using &&

Details

Require statements including conditions with the && operator can be broken down in multiple require statements to save gas. See reference: [G-09] of https://code4rena.com/reports/2022-04-backd/

Mitigation

I suggest breaking down multiple conditions into two require statement instead of using &&. Example: Changing from:

require(
    _minInterest < MAX_INT && _minInterest <= _vertexInterest && _minInterest >= MIN_INT,
    "LinearInterestRate: _minInterest < MAX_INT && _minInterest <= _vertexInterest && _minInterest >= MIN_INT"
);

to:

require(_minInterest < MAX_INT,"LinearInterestRate: _minInterest < MAX_INT");
require(_minInterest <= _vertexInterest,"LinearInterestRate: _minInterest <= _vertexInterest");
require(_minInterest >= MIN_INT,"LinearInterestRate: _minInterest >= MIN_INT");

Line of code

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L57-L60 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L61-L64 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L65-L68

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No need to explicitly initialize variables with their default values

Details

When variables are not set, it is assumed to have it's default value(0 for uint, false for bool, address(0) for address). Explicitly initializing it with its default value is an anti-pattern and wastes gas.

Mitigation

change uint256 private constant MIN_INT = 0; to uint256 private constant MIN_INT; see reference: https://code4rena.com/reports/2022-02-jpyc/ [G-07] GENERAL RECOMMENDATIONS

Line of code

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L33 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L51 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L81 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairConstants.sol#L47 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L265 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L270 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L289 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L308 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L127 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L152 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L402

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Pre-increment cost less gas than post-increment

Details

i++ costs more gas than ++i , for uint pre-decrement is cheaper than post-decrement see reference: https://github.com/code-423n4/2021-12-nftx-findings/issues/195

Mitigation

change i++ to ++i

Line of code

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L51 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L81 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L289 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L308 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L130 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L158

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Solidity compiler will always read the length of the array during each iteration

Details

.length in a loop can be extracted into a variable and used where necessary to reduce the number of storage reads see reference: https://github.com/code-423n4/2021-10-union-findings/issues/92

Mitigation:

This extra costs can be avoided by caching the array length. Example: uint256 _addressesLength = _addresses.length; for (uint256 i = 0; i < _addressesLength; i++) { }

Line of code

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L66 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L81 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L265 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L270 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L289 https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L308