Fraxlend (Frax Finance) contest - Waze's results

Fraxlend: A permissionless lending platform and the final piece of the Frax Finance Defi Trinity.

General Information

Platform: Code4rena

Start Date: 12/08/2022

Pot Size: $50,000 USDC

Total HM: 15

Participants: 120

Period: 5 days

Judge: Justin Goro

Total Solo HM: 6

Id: 153

League: ETH

Frax Finance

Findings Distribution

Researcher Performance

Rank: 41/120

Findings: 2

Award: $68.33

🌟 Selected for report: 0

🚀 Solo Findings: 0

#1 Missing natspec comment toShares

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/VaultAccount.sol#L14

toShares() was missing natspec comment. add natspec comment to toShares() to give knowledge to the user about the function and params

#2 Missing natspec comment toAmount

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/VaultAccount.sol#L31

toAmount() was missing natspec comment. add natspec comment to toAmount() to give knowledge to the user about the function and params

#3 Missing indexed field

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L1145

Each event should use three indexed fields if there are three or more fields. add indexed in _swapperAddress.

#4 Typo

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L306

typo can decrease readibility so to increase it fix the typo from approcal to approval.

#5 Missing immutable

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L57-L59

the state CIRCUIT_BREAKER_ADDRESS, COMPTROLLER_ADDRESS and TIME_LOCK_ADDRESS can't be initialize by constructor. the constructor parameter mention state CIRCUIT_BREAKER_ADDRESS, COMPTROLLER_ADDRESS and TIME_LOCK_ADDRESSS to initialize. so i suggest to add immutable on CIRCUIT_BREAKER_ADDRESS, COMPTROLLER_ADDRESS and TIME_LOCK_ADDRESS.

#6 Made to a struct

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L32-L38

for mapping that have same location of mapping (address => bool) can be compacted to aWhitelist struct

#7 Unbounded loop an array can lead DOS

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#L66

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L81

As this array can grow quite large, the transaction’s gas cost could exceed the block gas limit and make it impossible to call this function at all.

#8 Missing check for immutable address

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L98

constructor have four params address, so to avoid vulnerability we suggest to consider add simple checkaddress(0) for the params

#1 data.length should be cached

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/SafeERC20.sol#L19-L21

cache the data.length to the local because use multiple times for saving the gas fee. because mload is cheaper than sload.

#2 Default uint

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/SafeERC20.sol#L22

default value uint is 0 so remove unnecassary explicit value can reduce gas.

#3 Increment

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/SafeERC20.sol#L23

pre increment e.g ++i more cheaper gas than post increment e.g i++. i suggest to use pre increment.

#4 Use ++ instead i + 1

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/VaultAccount.sol#L26

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/VaultAccount.sol#L43

use ++i instead of i = i + 1 for increment can save the gas about 9 gas. example from shares = shares +1 to ++shares

#5 Use require instead &&

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L57-L67

use require instead && can save the gas because simply logic when code was executed so i suggest to change 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");

apply to others.

#6 Loop

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#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

default uint is 0 so remove unnecassary explicit can reduce gas. caching the array length can reduce gas it caused access to a local variable is more cheap than query storage / calldata / memory in solidity. pre increment e.g ++i more cheaper gas than post increment e.g i++. i suggest to use pre increment.

#7 bytes(_name).length should get cached name

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L254

cache the bytes(_name).length to the local for saving the gas fee. because mload is cheaper than sload.

#8 bytes(nameOfContract).length should get cached name kf cintract

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L257

cache the bytes(nameOfContract).length to the local saving the gas fee. because mload is cheaper than sload.

#9 Use Storage instead memory

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L419

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L517

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L611

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L882

Use storage instead of memory to reduce the gas fee. i suggest to change this.

#10 SSTORE2.read should get cached

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L208-L209

cache the SSTORE2.read to the local because use multiple times for saving the gas fee. because mload is cheaper than sload.

#11 Use Calldata instead memory

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L310

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L355

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L398

When arguments are read-only on external functions, the function() has an inputed parameter that using memory, if this function didnt change the parameter, its cheaper to use calldata then memory. so we suggest to change it.

#12 Reduce the string

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L57-L67

Shortening revert strings to fit in 32 bytes will decrease deployment time gas and will decrease runtime gas when the revert condition is met. Revert strings that are longer than 32 bytes require at least one additional mstore, along with additional overhead for computing memory offset, etc.

#13 Use custom revert string

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L57-L67

Custom errors from Solidity 0.8.0 are cheaper than revert strings (cheaper deployment cost and runtime cost when the revert condition is met)

#14 use !=0 instead >0

https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L66

!= 0 costs less gas compared to > 0 for unsigned integers in require statements with the optimizer enabled (6 gas)

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