Joyn contest - minhquanym's results

Lines of code

https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/ERC721Payable.sol#L54 https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreCollection.sol#L175

Vulnerability details

Impact

• It is good to add a require() statement that checks the return value of token transfers or to use something like OpenZeppelin’s safeTransfer/safeTransferFrom unless one is sure the given token reverts in case of a failure. Failure to do so will cause silent failures of transfers and affect token accounting in contract. transferFrom() might return false instead of reverting. In this case, failed transfer allows exploiter to call mintToken for free.

Proof of concept

• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/ERC721Payable.sol#L54
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreCollection.sol#L175

Recommended Mitigation Steps

• Consider using safeTransfer/safeTransferFrom or require().

Lines of code

https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L40-L41 https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L67-L70

Vulnerability details

Impact

• In function sendToSplitter, line 40 calculate platformShare = (balanceOfVault * platformFee) * 10000;
• And owner can set this platformFee to arbitrary uint256 value using setPlatformFee function.
• If platformFee > 10000 then platformShare will even bigger than balanceOfVault, make line 41 revert everytime because of arithmetic underflow and causes denial of service.

Proof of concept

• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L40-L41
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L67-L70

Recommended Mitigation Steps

• Check if platformFee <= 10000 in setPlatformFee function. require(platformFee <= 10000, ‘invalid platformFee’);

1. Cache length in the for loop and uncheck index

Impact

• At each iteration of the loop, length is read from memory. We can cache the length and save gas per iteration.
• Solidity 0.8.0 check safe math in every operation. Use uncheck to increase index can save gas.

Occurences

• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreCollection.sol#L279
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreFactory.sol#L79
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/splits/contracts/Splitter.sol#L50
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/splits/contracts/Splitter.sol#L274

Recommended Mitigation Steps

• For example, for-loop in line 79 CoreFactory.sol can be optimized:

uint256 length = _collections.length;
for (uint256 i; i < length; ) {
	// do something //
	uncheck { ++i; }
}

2. != 0 costs less gass compared to > 0 for unsigned integer

Impact

• != 0 costs less gass compared to > 0 for unsigned integer

Occurences

• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L35
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreCollection.sol#L53
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreCollection.sol#L146
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreCollection.sol#L161
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreCollection.sol#L305
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/core-contracts/contracts/CoreFactory.sol#L75
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/splits/contracts/Splitter.sol#L164

Recommended Mitigation Steps

• Change > 0 with != 0.

3. Remove == true when check boolean variable save gas.

Impact

• Remove == true when check boolean variable can save a tiny amount of gas.

Occurences

• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L44
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L48
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L55

Recommended Mitigation Steps

• Remove == true.

4. Check amount before transfer can save gas.

Impact

• platformShare can be 0 when balanceOfVault < 10000 / platformFee (platformFee = 500 in default)
• splitterShare can be 0 when platformFee == 10000.
• In that case, we should check if platformShare != 0 and splitterShare != 0 before making the transfer to save gas.

Proof of concept

• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L40
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L44
• https://github.com/code-423n4/2022-03-joyn/blob/c9297ccd925ebb2c44dbc6eaa3effd8db5d2368a/royalty-vault/contracts/RoyaltyVault.sol#L52

Recommended Mitigation Steps

• Add check if platformShare != 0 before transfer