Foundation Drop contest - 0xNazgul's results

[NAZ-L1] Missing Zero-address Validation

Severity: Low Context: AdminRole.sol#L15, AdminRole.sol#L28, AdminRole.sol#L37, MinterRole.sol#L28, MinterRole.sol#L36, MinterRole.sol#L45

Description: Lack of zero-address validation on address parameters may lead to transaction reverts, waste gas, require resubmission of transactions and may even force contract redeployments in certain cases within the protocol.

Recommendation: Consider adding explicit zero-address validation on input parameters of address type.

[NAZ-L2] receive() Function Should Emit An Event

Severity: Low Context: FETHNode.sol#L33

Description: Consider emitting an event inside this function with msg.sender and msg.value as the parameters. This would make it easier to track incoming ether transfers.

Recommendation: Consider adding events to the receive() functions.

[NAZ-L3] Missing Events In Initialize Functions

Severity: Low Context: NFTCollectionFactory.sol#L192, NFTDropCollection.sol#L120, NFTCollection.sol#L105, NFTDropMarket.sol#L100

Description: None of the initialize functions emit emit init-specific events. They all however have the initializer modifier (from Initializable) so that they can be called only once. Off-chain monitoring of calls to these critical functions is not possible.

Recommendation: It is recommended to perform validation of input parameters and emit events.

[NAZ-N1] TODOs Left In The Code

Severity: Informational Context: MarketFees.sol#L193

Description: There should never be any TODOs in the code when deploying.

Recommendation: Consider finishing the TODOs before deploying.

[NAZ-N2] Use Underscores for Number Literals

Severity: Informational Context: Constants.sol#L10, Constants.sol#L26, Constants.sol#L38, Constants.sol#L48, Constants.sol#L53, MarketFees.sol#L45

Description: There are multiple occasions where certain numbers have been hardcoded, either in variables or in the code itself. Large numbers can become hard to read.

Recommendation: Consider using underscores for number literals to improve its readability.

[NAZ-N3] Unindexed Event Parameters

Severity Informational Context: NFTDropCollection.sol#L85

Description: Parameters of certain events are expected to be indexed so that they’re included in the block’s bloom filter for faster access. Failure to do so might confuse off-chain tooling looking for such indexed events.

Recommendation: Consider adding the indexed keyword to event parameters that should include it.

[NAZ-N4] Code Contains Empty Blocks

Severity: Informational Context: NFTDropCollection.sol#L102, NFTCollection.sol#L96, NFTDropMarket.sol#L93

Description: It's best practice that when there is an empty block, to add a comment in the block explaining why it's empty.

Recommendation: Consider adding /* Comment on why */ to the empty block.

[NAZ-N5] Floating Pragma

Severity: Informational Context: All Contracts

Description: Contracts should be deployed with the same compiler version and flags that they have been tested with thoroughly. Locking the pragma helps to ensure that contracts do not accidentally get deployed using, for example, an outdated compiler version that might introduce bugs that affect the contract system negatively.

Recommendation: Consider locking the pragma version.

[NAZ-N6] Older Version Pragma

Severity: Informational Context: All Contracts

Description: Using very old versions of Solidity prevents benefits of bug fixes and newer security checks. Using the latest versions might make contracts susceptible to undiscovered compiler bugs.

Recommendation: Consider using the most recent version.

[NAZ-N7] Missing or Incomplete NatSpec

Severity: Informational Context: All Contracts

Description: Some functions are missing @notice/@dev NatSpec comments for the function, @param for all/some of their parameters and @return for return values. Given that NatSpec is an important part of code documentation, this affects code comprehension, auditability and usability.

Recommendation: Add in full NatSpec comments for all functions to have complete code documentation for future use.

[NAZ-G1] In require(), Use != 0 Instead of > 0 With Uint Values

Context: NFTDropCollection.sol#L131

Description: In a require, when checking a uint, using != 0 instead of > 0 saves 6 gas. This will jump over or avoid an extra ISZERO opcode.

Recommendation: Use != 0 instead of > 0 with uint values but only in require() statements.

[NAZ-G2] The Increment In For Loop Post Condition Can Be Made Unchecked

Context: MarketFees.sol#L198

Description: (This is only relevant if you are using the default solidity checked arithmetic). i++ involves checked arithmetic, which is not required. This is because the value of i is always strictly less than length <= 2**256 - 1. Therefore, the theoretical maximum value of i to enter the for-loop body is 2**256 - 2. This means that the i++ in the for loop can never overflow. Regardless, the overflow checks are performed by the compiler.

Unfortunately, the Solidity optimizer is not smart enough to detect this and remove the checks. One can manually do this by:

for (uint i = 0; i < length; i = unchecked_inc(i)) {
    // do something that doesn't change the value of i
}

function unchecked_inc(uint i) returns (uint) {
    unchecked {
        return i + 1;
    }
}

Note that it’s important that the call to unchecked_inc is inlined. This is only possible for solidity versions starting from 0.8.2.

Recommendation: The increment in the for loop post condition can be made unchecked.

[NAZ-G3] Catching The Array Length Prior To Loop

Context: MarketFees.sol#L198, MarketFees.sol#L484, MarketFees.sol#L503

Description: One can save gas by caching the array length (in stack) and using that set variable in the loop. Replace state variable reads and writes within loops with local variable reads and writes. This is done by assigning state variable values to new local variables, reading and/or writing the local variables in a loop, then after the loop assigning any changed local variables to their equivalent state variables.

Recommendation: Simply do something like so before the for loop: uint length = variable.length. Then add length in place of variable.length in the for loop.

[NAZ-G4] Functions Visibility Can Be Declared External

Context: NFTDropCollection.sol#L159

Description: Several functions across multiple contracts have a public visibility and can be marked with external visibility to save gas.

Recommendation: Change the functions visibility to external to save gas.

[NAZ-G5] Setting The Constructor To Payable

Context: All Contracts

Description: You can cut out 10 opcodes in the creation-time EVM bytecode if you declare a constructor payable. Making the constructor payable eliminates the need for an initial check of msg.value == 0 and saves 21 gas on deployment with no security risks.

Recommendation: Set the constructor to payable.

[NAZ-G6] Use of Custom Errors Instead of String

Context: All Contracts

Description: To save some gas the use of custom errors leads to cheaper deploy time cost and run time cost. The run time cost is only relevant when the revert condition is met.

Recommendation: Use Custom Errors instead of strings.

[NAZ-G7] Function Ordering via Method ID

Context: All Contracts

Description: Contracts most called functions could simply save gas by function ordering via Method ID. Calling a function at runtime will be cheaper if the function is positioned earlier in the order (has a relatively lower Method ID) because 22 gas are added to the cost of a function for every position that came before it. The caller can save on gas if you prioritize most called functions. One could use This tool to help find alternative function names with lower Method IDs while keeping the original name intact.

Recommendation: Find a lower method ID name for the most called functions for example mostCalled() vs. mostCalled_41q() is cheaper by 44 gas.

createNFTDropCollection gas reporter results:
  using > 0 (current):
    - 319246  ·     319578  ·      319361
  using != 0 (recommendation):
    -  319252  ·     319584  ·      319367
  impact: +6 gas