Joyn contest - defsec's results

Lines of code

https://github.com/code-423n4/2022-03-joyn/blob/main/royalty-vault/contracts/RoyaltyVault.sol#L68

Vulnerability details

Impact

The platformFee does not have any upper or lower bounds. Values that are too large will lead to reversions in several critical functions or the platform user will lost all funds when paying the fee.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-03-joyn/blob/main/royalty-vault/contracts/RoyaltyVault.sol#L68

2. Here you can see there is no upper bound has been defined.

    function setPlatformFee(uint256 _platformFee) external override onlyOwner {
        platformFee = _platformFee;
        emit NewRoyaltyVaultPlatformFee(_platformFee);
    }

3. In the protocol, the fee percentage has been defined on the scale of X-1000.

Tools Used

Code Review

Recommended Mitigation Steps

Consider defining upper and lower bounds on the platformFee variable.

Judge has assessed an item in Issue #96 as Medium risk. The relevant finding follows:

Impact - LOW All contract initializers were missing access controls, allowing any user to initialize the contract. By front-running the contract deployers to initialize the contract, the incorrect parameters may be supplied, leaving the contract needing to be redeployed.

Proof of Concept Navigate to the following contracts. https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L78 initialize functions does not have access control. They are vulnerable to front-running. Tools Used Manual Code Review

Recommended Mitigation Steps While the code that can be run in contract constructors is limited, setting the owner in the contract's constructor to the msg.sender and adding the onlyOwner modifier to all initializers would be a sufficient level of access control.

Judge has assessed an item in Issue #96 as Medium risk. The relevant finding follows:

Impact - LOW PrePo protocol do not appear to support rebasing/deflationary/inflationary tokens whose balance changes during transfers or over time. The necessary checks include at least verifying the amount of tokens transferred to contracts before and after the actual transfer to infer any fees/interest.

Proof of Concept Navigate to the following contract. 2022-03-joyn/core-contracts/contracts/CoreCollection.sol::175 => payableToken.transferFrom(address(this), msg.sender, amount); 2022-03-joyn/core-contracts/contracts/ERC721Payable.sol::54 => payableToken.transferFrom(msg.sender, recipient, _amount);

Tools Used Manual Code Review

Recommended Mitigation Steps Ensure that to check previous balance/after balance equals to amount for any rebasing/inflation/deflation Add support in contracts for such tokens before accepting user-supplied tokens Consider supporting deflationary / rebasing / etc tokens by extra checking the balances before/after or strictly inform your users not to use such tokens if they don't want to lose them.

C4-001 : Use safeTransfer/safeTransferFrom consistently instead of transfer/transferFrom

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.

Reference: This similar medium-severity finding from Consensys Diligence Audit of Fei Protocol: https://consensys.net/diligence/audits/2021/01/fei-protocol/#unchecked-return-value-for-iweth-transfer-call

Proof of Concept

1. Navigate to the following contract.

2. transfer/transferFrom functions are used instead of safe transfer/transferFrom on the following contracts.

  2022-03-joyn/core-contracts/contracts/CoreCollection.sol::175 => payableToken.transferFrom(address(this), msg.sender, amount);
  2022-03-joyn/core-contracts/contracts/ERC721Payable.sol::54 => payableToken.transferFrom(msg.sender, recipient, _amount);

Tools Used

Code Review

Recommended Mitigation Steps

Consider using safeTransfer/safeTransferFrom or require() consistently.

C4-002 : Incompatibility With Rebasing/Deflationary/Inflationary tokens

Impact - LOW

PrePo protocol do not appear to support rebasing/deflationary/inflationary tokens whose balance changes during transfers or over time. The necessary checks include at least verifying the amount of tokens transferred to contracts before and after the actual transfer to infer any fees/interest.

Proof of Concept

1. Navigate to the following contract.

  2022-03-joyn/core-contracts/contracts/CoreCollection.sol::175 => payableToken.transferFrom(address(this), msg.sender, amount);
  2022-03-joyn/core-contracts/contracts/ERC721Payable.sol::54 => payableToken.transferFrom(msg.sender, recipient, _amount);

Tools Used

Manual Code Review

Recommended Mitigation Steps

• Ensure that to check previous balance/after balance equals to amount for any rebasing/inflation/deflation
• Add support in contracts for such tokens before accepting user-supplied tokens
• Consider supporting deflationary / rebasing / etc tokens by extra checking the balances before/after or strictly inform your users not to use such tokens if they don't want to lose them.

C4-003 : Missing zero-address check in constructors and the setter functions

Impact - LOW

Missing checks for zero-addresses may lead to infunctional protocol, if the variable addresses are updated incorrectly.

Proof of Concept

1. Navigate to the following all contract functions.

https://github.com/code-423n4/2022-03-joyn/blob/main/royalty-vault/contracts/RoyaltyVault.sol#L68


https://github.com/code-423n4/2022-03-joyn/blob/main/royalty-vault/contracts/RoyaltyVaultFactory.sol#L25

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L78

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreFactory.sol#L27

Tools Used

Code Review

Recommended Mitigation Steps

Consider adding zero-address checks in the discussed constructors: require(newAddr != address(0));.

C4-004 : transferOwnership should be two step process

Impact - LOW

The current ownership transfer process involves the current owner calling Unlock.transferOwnership(). This function checks the new owner is not the zero address and proceeds to write the new owner's address into the owner's state variable. If the nominated EOA account is not a valid account, it is entirely possible the owner may accidentally transfer ownership to an uncontrolled account, breaking all functions with the onlyOwner() modifier. Lack of two-step procedure for critical operations leaves them error-prone if the address is incorrect, the new address will take on the functionality of the new role immediately

for Ex : -Alice deploys a new version of the whitehack group address. When she invokes the whitehack group address setter to replace the address, she accidentally enters the wrong address. The new address now has access to the role immediately and is too late to revert

Proof of Concept

1. https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L15, https://github.com/code-423n4/2022-03-joyn/blob/main/royalty-vault/contracts/RoyaltyVault.sol#L11, .
2. The contracts have many onlyOwner function.
3. The contract is inherited from the Ownable which includes transferOwnership.

Tools Used

None

Recommended Mitigation Steps

Implement zero address check and Consider implementing a two step process where the owner nominates an account and the nominated account needs to call an acceptOwnership() function for the transfer of ownership to fully succeed. This ensures the nominated EOA account is a valid and active account.

C4-005 : Front-runnable Initializers

Impact - LOW

All contract initializers were missing access controls, allowing any user to initialize the contract. By front-running the contract deployers to initialize the contract, the incorrect parameters may be supplied, leaving the contract needing to be redeployed.

Proof of Concept

1. Navigate to the following contracts.

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L78

2. initialize functions does not have access control. They are vulnerable to front-running.

Tools Used

Manual Code Review

Recommended Mitigation Steps

While the code that can be run in contract constructors is limited, setting the owner in the contract's constructor to the msg.sender and adding the onlyOwner modifier to all initializers would be a sufficient level of access control.

C4-006 : Consider making contracts Pausable

Impact - LOW

There are many external risks so my suggestion is that you should consider making the contracts pausable, so in case of an unexpected event, the admin can pause transfers.

Tools Used

Code Review

Recommended Mitigation Steps

Consider making contracts Pausable https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/security/Pausable.sol.

C4-007 : Critical changes should use two-step procedure

Impact - NON CRITICAL

The critical procedures should be two step process.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-03-joyn/blob/main/royalty-vault/contracts/RoyaltyVaultFactory.sol#L57

https://github.com/code-423n4/2022-03-joyn/blob/main/royalty-vault/contracts/RoyaltyVaultFactory.sol#L66

Tools Used

Code Review

Recommended Mitigation Steps

Lack of two-step procedure for critical operations leaves them error-prone. Consider adding two step procedure on the critical functions.

C4-008 : # DoS With Block Gas Limit

Impact - Non-Critical

When smart contracts are deployed or functions inside them are called, the execution of these actions always requires a certain amount of gas, based of how much computation is needed to complete them. The Ethereum network specifies a block gas limit and the sum of all transactions included in a block can not exceed the threshold.

Programming patterns that are harmless in centralized applications can lead to Denial of Service conditions in smart contracts when the cost of executing a function exceeds the block gas limit. Modifying an array of unknown size, that increases in size over time, can lead to such a Denial of Service condition.

Proof of Concept

1. Follow the functions shown below.

2022-03-joyn/core-contracts/contracts/CoreFactory.sol::79 => for (uint256 i; i < _collections.length; i++) {

Tools Used

Code Review

Recommended Mitigation Steps

Caution is advised when you expect to have large arrays that grow over time. Actions that require looping across the entire data structure should be avoided.

If you absolutely must loop over an array of unknown size, then you should plan for it to potentially take multiple blocks, and therefore require multiple transactions.

C4-009 : # Missing Re-entrancy Guard

Impact

The re-entrancy guard is missing on the Eth anchor interaction. The external router interaction can cause to the re-entrancy vulnerability.

Proof of Concept

1. Navigate to the following contract.

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

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L139

Tools Used

Code Review

Recommended Mitigation Steps

Follow the check effect interaction pattern or put re-entrancy guard.

C4-010 : Missing events for only functions that change critical parameters

Impact - Non critical

The afunctions that change critical parameters should emit events. Events allow capturing the changed parameters so that off-chain tools/interfaces can register such changes with timelocks that allow users to evaluate them and consider if they would like to engage/exit based on how they perceive the changes as affecting the trustworthiness of the protocol or profitability of the implemented financial services. The alternative of directly querying on-chain contract state for such changes is not considered practical for most users/usages.

Missing events and timelocks do not promote transparency and if such changes immediately affect users’ perception of fairness or trustworthiness, they could exit the protocol causing a reduction in liquidity which could negatively impact protocol TVL and reputation.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-03-joyn/blob/main/splits/contracts/Splitter.sol#L195

See similar High-severity H03 finding OpenZeppelin’s Audit of Audius (https://blog.openzeppelin.com/audius-contracts-audit/#high) and Medium-severity M01 finding OpenZeppelin’s Audit of UMA Phase 4 (https://blog.openzeppelin.com/uma-audit-phase-4/)

Tools Used

None

Recommended Mitigation Steps

Add events to all functions that change critical parameters.

C4-001 : There is no need to assign default values to variables

Impact - Gas Optimization

When a variable is declared solidity assigns the default value. In case the contract assigns the value again, it costs extra gas.

Example: uint x = 0 costs more gas than uint x without having any different functionality.

Proof of Concept

  2022-03-joyn/core-contracts/contracts/CoreCollection.sol::279 => for (uint256 i = 0; i < _amount; i++) {

Tools Used

Code Review

Recommended Mitigation Steps

uint x = 0 costs more gas than uint x without having any different functionality.

C4-002 : Cache array length in for loops can save gas

Impact

Reading array length at each iteration of the loop takes 6 gas (3 for mload and 3 to place memory_offset) in the stack.

Caching the array length in the stack saves around 3 gas per iteration.

Proof of Concept

1. Navigate to the following smart contract line.

  2022-03-joyn/core-contracts/contracts/CoreCollection.sol::205 => bytes(HASHED_PROOF).length == 0,
  2022-03-joyn/core-contracts/contracts/CoreFactory.sol::75 => _collections.length > 0,
  2022-03-joyn/core-contracts/contracts/CoreFactory.sol::79 => for (uint256 i; i < _collections.length; i++) {

Tools Used

None

Recommended Mitigation Steps

Consider to cache array length.

C4-003: > 0 can be replaced with != 0 for gas optimization

Impact

!= 0 is a cheaper operation compared to > 0, when dealing with uint.

Proof of Concept

1. Navigate to the following contracts.

  2022-03-joyn/core-contracts/contracts/CoreCollection.sol::53 => _maxSupply > 0,
  2022-03-joyn/core-contracts/contracts/CoreCollection.sol::146 => require(amount > 0, "CoreCollection: Amount should be greater than 0");
  2022-03-joyn/core-contracts/contracts/CoreCollection.sol::161 => if (mintFee > 0) {
  2022-03-joyn/core-contracts/contracts/CoreCollection.sol::305 => IRoyaltyVault(royaltyVault).getVaultBalance() > 0
  2022-03-joyn/core-contracts/contracts/CoreFactory.sol::75 => _collections.length > 0,

Tools Used

Code Review

Recommended Mitigation Steps

Use "!=0" instead of ">0" for the gas optimization.

C4-004: Immutable variables

Impact

'immutable' greatly reduces gas costs. There are variables that do not change so they can be marked as immutable to greatly improve the gas costs.

Proof of Concept

2022-03-joyn/core-contracts/contracts/CoreCollection.sol::227 => keccak256(abi.encodePacked("CoreCollection", block.number)) 2022-03-joyn/core-contracts/contracts/CoreFactory.sol::148 => new CoreProxy{salt: keccak256(abi.encodePacked(_collection.id))}( 2022-03-joyn/core-contracts/contracts/ERC721Claimable.sol::98 => return keccak256(abi.encodePacked(who, claimableAmount));

Tools Used

Code Review

Recommended Mitigation Steps

Mark variables as immutable.

C4-005: Revert String Size Optimization

Impact

Shortening revert strings to fit in 32 bytes will decrease deploy time gas and will decrease runtime gas when the revert condition has been met.

Revert strings that are longer than 32 bytes require at least one additional mstore, along with additional overhead for computing memory offset, etc.

Proof of Concept

Revert strings > 32 bytes are here:

2022-03-joyn/core-contracts/contracts/CoreCollection.sol::47 => require(!initialized, "CoreCollection: Already initialized");

Tools Used

Manual Review

Recommended Mitigation Steps

Shorten the revert strings to fit in 32 bytes. That will affect gas optimization.

C4-006 : Adding unchecked directive can save gas

Impact

For the arithmetic operations that will never over/underflow, using the unchecked directive (Solidity v0.8 has default overflow/underflow checks) can save some gas from the unnecessary internal over/underflow checks.

Proof of Concept

 2022-03-joyn/core-contracts/contracts/CoreCollection.sol::205 => bytes(HASHED_PROOF).length == 0,
  2022-03-joyn/core-contracts/contracts/CoreFactory.sol::75 => _collections.length > 0,
  2022-03-joyn/core-contracts/contracts/CoreFactory.sol::79 => for (uint256 i; i < _collections.length; i++) {

Tools Used

None

Recommended Mitigation Steps

Consider applying unchecked arithmetic where overflow/underflow is not possible.

C4-007 : Free gas savings for using solidity 0.8.10+

Impact

Using newer compiler versions and the optimizer gives gas optimizations and additional safety checks are available for free.

Proof of Concept

Solidity 0.8.10 has a useful change which reduced gas costs of external calls which expect a return value: https://blog.soliditylang.org/2021/11/09/solidity-0.8.10-release-announcement/

Code Generator: Skip existence check for external contract if return data is expected. In this case, the ABI decoder will revert if the contract does not exist

All Contracts

Tools Used

None

Recommended Mitigation Steps

Consider to upgrade pragma to at least 0.8.10.

C4-008 : Use calldata instead of memory for function parameters

Impact

In some cases, having function arguments in calldata instead of memory is more optimal.

Consider the following generic example:

contract C {
function add(uint[] memory arr) external returns (uint sum) {
uint length = arr.length;
for (uint i = 0; i < arr.length; i++) {
sum += arr[i];
}
}
}

In the above example, the dynamic array arr has the storage location memory. When the function gets called externally, the array values are kept in calldata and copied to memory during ABI decoding (using the opcode calldataload and mstore). And during the for loop, arr[i] accesses the value in memory using a mload. However, for the above example this is inefficient. Consider the following snippet instead:

contract C {
function add(uint[] calldata arr) external returns (uint sum) {
uint length = arr.length;
for (uint i = 0; i < arr.length; i++) {
sum += arr[i];
}
}
}

In the above snippet, instead of going via memory, the value is directly read from calldata using calldataload. That is, there are no intermediate memory operations that carries this value.

Gas savings: In the former example, the ABI decoding begins with copying value from calldata to memory in a for loop. Each iteration would cost at least 60 gas. In the latter example, this can be completely avoided. This will also reduce the number of instructions and therefore reduces the deploy time cost of the contract.

In short, use calldata instead of memory if the function argument is only read.

Note that in older Solidity versions, changing some function arguments from memory to calldata may cause "unimplemented feature error". This can be avoided by using a newer (0.8.*) Solidity compiler.

Examples Note: The following pattern is prevalent in the codebase:

function f(bytes memory data) external {
(...) = abi.decode(data, (..., types, ...));
}

Here, changing to bytes calldata will decrease the gas. The total savings for this change across all such uses would be quite significant.

Proof Of Concept

Examples:

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L144

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L203

Tools Used

None

Recommended Mitigation Steps

Change memory definition with calldata.

C4-009 : Non-strict inequalities are cheaper than strict ones

Impact

Strict inequalities add a check of non equality which costs around 3 gas.

Proof of Concept

All Facets Directory Contracts
Examples :
https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L305

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L161

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L146

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L53

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L161

https://github.com/code-423n4/2022-03-joyn/blob/main/royalty-vault/contracts/RoyaltyVault.sol#L35

Tools Used

Code Review

Recommended Mitigation Steps

Use >= or <= instead of > and < when possible.

C4-010 : Changing function visibility from public to external can save gas

Impact

There is a function declared as public that are never called internally within the contract. It is best practice to mark such functions as external instead, as this saves gas (especially in the case where the function takes arguments, as external functions can read arguments directly from calldata instead of having to allocate memory).

Proof of Concept

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L236

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L248

Tools Used

Code Review

Recommended Mitigation Steps

All of the public functions in the contract are not called internally, so access can be changed to external to reduce gas.

C4-011: Redundant Import

Impact

Constructor is redundant in the following code.

Proof of Concept

https://github.com/code-423n4/2022-03-joyn/blob/main/core-contracts/contracts/CoreCollection.sol#L37

Tools Used

Code Review

Recommended Mitigation Steps

Consider deleting the redundant code.