PartyDAO contest - 0xkatana's results

A protocol for buying, using, and selling NFTs as a group.

General Information

Platform: Code4rena

Start Date: 12/09/2022

Pot Size: $75,000 USDC

Total HM: 19

Participants: 110

Period: 7 days

Judge: HardlyDifficult

Total Solo HM: 9

Id: 160

League: ETH

PartyDAO

Findings Distribution

Researcher Performance

Rank: 75/110

Findings: 1

Award: $40.18

🌟 Selected for report: 0

🚀 Solo Findings: 0

External Links

Code4rena Contest Page Github Contest Repository Github Findings Repository PartyDAO

Findings Information

🌟 Selected for report: CertoraInc

Also found by: 0x1f8b, 0x4non, 0x5rings, 0x85102, 0xNazgul, 0xSmartContract, 0xkatana, Amithuddar, Aymen0909, B2, Bnke0x0, CRYP70, Chom, ChristianKuri, CodingNameKiki, Deivitto, Diraco, Fitraldys, Funen, IgnacioB, JAGADESH, JC, Lambda, LeoS, Matin, Metatron, MiloTruck, Noah3o6, Ocean_Sky, Olivierdem, PaludoX0, RaymondFam, ReyAdmirado, Rohan16, Rolezn, Saintcode_, Sm4rty, SnowMan, StevenL, Tomio, Tomo, V_B, Waze, __141345__, ajtra, asutorufos, aysha, brgltd, bulej93, c3phas, ch0bu, d3e4, delfin454000, dharma09, djxploit, erictee, fatherOfBlocks, francoHacker, gianganhnguyen, gogo, got_targ, ignacio, jag, karanctf, ladboy233, leosathya, lukris02, m_Rassska, malinariy, martin, natzuu, pashov, peanuts, peiw, pfapostol, prasantgupta52, robee, simon135, slowmoses, sryysryy, tnevler

Awards

40.1848 USDC - $40.18

Labels

bug

G (Gas Optimization)

low quality report

sponsor disputed

old-submission-method

External Links

Link to GitHub issue

[G-01] Redundant zero initialization

Solidity does not recognize null as a value, so uint variables are initialized to zero. Setting a uint variable to zero is redundant and can waste gas.

Recommended Mitigation Steps

Remove the redundant zero initialization uint256 i; instead of uint256 i = 0;

[G-02] Use != 0 instead of > 0

Using > 0 uses slightly more gas than using != 0. Use != 0 when comparing uint variables to zero, which cannot hold values below zero

Locations where this was found include https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/Crowdfund.sol#L144 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/Crowdfund.sol#L471

Recommended Mitigation Steps

Replace > 0 with != 0 to save gas

[G-03] Use prefix not postfix in loops

Using a prefix increment (++i) instead of a postfix increment (i++) saves gas for each loop cycle and so can have a big gas impact when the loop executes on a large number of elements.

Locations where this was found include https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/CollectionBuyCrowdfund.sol#L62

Recommended Mitigation Steps

Use prefix not postfix to increment in a loop

[G-04] For loop incrementing can be unsafe

For loops that use i++ do not need to use safemath for this operation because the loop would run out of gas long before this point. Making this addition operation unsafe using unchecked saves gas.

Sample code to make the for loop increment unsafe

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;
    }
}

Idea borrowed from https://gist.github.com/hrkrshnn/ee8fabd532058307229d65dcd5836ddc#the-increment-in-for-loop-post-condition-can-be-made-unchecked

Recommended Mitigation Steps

Make the increment in for loops unsafe to save gas

[G-05] Use iszero assembly for zero checks

Comparing a value to zero can be done using the iszero EVM opcode. This can save gas

Source from t11s https://twitter.com/transmissions11/status/1474465495243898885

Recommended Mitigation Steps

Use the assembly iszero evm opcode to compare values to zero

[G-06] Save gas with unchecked

Use unchecked math when there is no overflow risk to save gas. Solidity 0.8.X adds Safemath by default, and there are cases where Safemath provides no benefit and uses extra gas.

Locations where this was found include https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/Crowdfund.sol#L358 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/Crowdfund.sol#L360

Recommended Mitigation Steps

Add unchecked around math that can't overflow for gas savings. In Solidity before 0.8.0, use the normal math operators instead of safe math functions.

[G-07] Add payable to functions that won't receive ETH

Identifying a function as payable saves gas. Functions that have a modifier like onlyPartyDao cannot be called by normal users and will not mistakenly receive ETH. These functions can be payable to save gas.

There are many functions that have access control modifiers in the contracts. Some examples are https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/party/PartyGovernance.sol#L451 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/party/PartyGovernance.sol#L458 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/party/PartyGovernance.sol#L483 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/party/PartyGovernance.sol#L526 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/party/PartyGovernance.sol#L800

Recommended Mitigation Steps

Add payable to these functions for gas savings

[G-08] Add payable to constructors that won't receive ETH

Identifying a constructor as payable saves gas. Constructors should only be called by the admin or deployer and should not mistakenly receive ETH. Constructors can be payable to save gas.

Recommended Mitigation Steps

Add payable to these functions for gas savings

[G-09] Use internal function in place of modifier

An internal function can save gas vs. a modifier. A modifier inlines the code of the original function but an internal function does not.

Source https://blog.polymath.network/solidity-tips-and-tricks-to-save-gas-and-reduce-bytecode-size-c44580b218e6#dde7

Recommended Mitigation Steps

Use internal functions in place of modifiers to save gas.

[G-10] Use uint not bool

Booleans are more expensive than uint256 or any type that takes up a full word because each write operation emits an extra SLOAD to first read the slot's contents, replace the bits taken up by the boolean, and then write back. This is the compiler's defense against contract upgrades and pointer aliasing, and it cannot be disabled.

Recommended Mitigation Steps

Replace bool variables with uints

[G-11] Use uint256 not smaller ints

From the solidity docs

When using elements that are smaller than 32 bytes, your contract’s gas usage may be higher. This is because the EVM operates on 32 bytes at a time. Therefore, if the element is smaller than that, the EVM must use more operations in order to reduce the size of the element from 32 bytes to the desired size.

Locations where this was found include https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/BuyCrowdfundBase.sol#L27 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/BuyCrowdfundBase.sol#L30 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/BuyCrowdfundBase.sol#L36 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/BuyCrowdfundBase.sol#L60 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/BuyCrowdfundBase.sol#L62 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/BuyCrowdfundBase.sol#L64

Recommended Mitigation Steps

Replace smaller int or uint variables with uint256 variables

[G-12] Use newer solidity version

A solidity version before 0.8.X is used in this project. The latest release of solidity includes changes that can provide gas savings. The improvements include:

Low level inliner from 0.8.2, leads to cheaper runtime gas. Especially relevant when the contract has small functions. For example, OpenZeppelin libraries typically have a lot of small helper functions and if they are not inlined, they cost an additional 20 to 40 gas because of 2 extra jump instructions and additional stack operations needed for function calls.
Optimizer improvements in packed structs: Before 0.8.3, storing packed structs, in some cases used an additional storage read operation. After EIP-2929, if the slot was already cold, this means unnecessary stack operations and extra deploy time costs. However, if the slot was already warm, this means additional cost of 100 gas alongside the same unnecessary stack operations and extra deploy time costs.
Custom errors from 0.8.4, leads to cheaper deploy time cost and run time cost. Note: the run time cost is only relevant when the revert condition is met. In short, replace revert strings by custom errors.
Solidity version 0.8.13 can save more gas with Yul IR pipeline

Source https://gist.github.com/hrkrshnn/ee8fabd532058307229d65dcd5836ddc#upgrade-to-at-least-084

Recommended Mitigation Steps

Use solidity release 0.8.13 with Yul IR pipeline and other improvements for gas savings

[G-13] Use Solidity errors instead of require

Solidity errors introduced in version 0.8.4 can save gas on revert conditions https://blog.soliditylang.org/2021/04/21/custom-errors/ https://twitter.com/PatrickAlphaC/status/1505197417884528640

Locations where this was found include https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/utils/ReadOnlyDelegateCall.sol#L20 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/proposals/ProposalExecutionEngine.sol#L246 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/proposals/ProposalExecutionEngine.sol#L247

Recommended Mitigation Steps

Replace require blocks with new solidity errors described in https://blog.soliditylang.org/2021/04/21/custom-errors/

[G-14] Use simple comparison in if statement

The comparison operators >= and <= use more gas than >, <, or ==. Replacing the >= and ≤ operators with a comparison operator that has an opcode in the EVM saves gas

The existing code is https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/AuctionCrowdfund.sol#L276-L280 https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/crowdfund/BuyCrowdfundBase.sol#L159-L163

if (block.timestamp >= expiry) {
    // Expired. `finalize()` needs to be called.
    return CrowdfundLifecycle.Expired;
}
return CrowdfundLifecycle.Active;

A simple comparison can be used for gas savings by reversing the logic

if (block.timestamp < expiry) {
    return CrowdfundLifecycle.Active;
}
// Expired. `finalize()` needs to be called.
return CrowdfundLifecycle.Expired;

Recommended Mitigation Steps

Replace the comparison operator and reverse the logic to save gas using the suggestions above

[G-15] Bitshift for divide by 2

When multiply or dividing by a power of two, it is cheaper to bitshift than to use standard math operations.

There is a divide by 2 operation on these lines https://github.com/PartyDAO/party-contracts-c4/tree/main/contracts/party/PartyGovernance.sol#L434

Recommended Mitigation Steps

Bitshift right by one bit instead of dividing by 2 to save gas

[G-16] Non-public variables save gas

Many constant variables are public, but changing the visibility of these variables to private or internal can save gas.

Recommended Mitigation Steps

Declare some public variables as private or internal to save gas

[G-17] Use calldata instead of memory for function arguments

Using calldata instead of memory for function arguments saves gas sometimes. This can happen when a function is called externally and the memory array values are kept in calldata and copied to memory during ABI decoding (using the opcode calldataload and mstore). If the array is used in a for loop, arr[i] accesses the value in memory using a mload. If calldata is used instead, then 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.

Source https://gist.github.com/hrkrshnn/ee8fabd532058307229d65dcd5836ddc#use-calldata-instead-of-memory-for-function-parameters

Recommended Mitigation Steps

Change function arguments from memory to calldata

[G-18] Write contracts in vyper

The contracts are all written entirely in solidity. Writing contracts with vyper instead of solidity can save gas.

Source https://twitter.com/eiber_david/status/1515737811881807876 doggo demonstrates https://twitter.com/fubuloubu/status/1528179581974417414?t=-hcq_26JFDaHdAQZ-wYxCA&s=19

Recommended Mitigation Steps

Write some or all of the contracts in vyper to save gas

#0 - 0xble
2022-09-26T01:07:14Z

Unhelpful bot report

PartyDAO contest - 0xkatana's results

A protocol for buying, using, and selling NFTs as a group.

General Information

Findings Distribution

Researcher Performance

External Links

[G-13] Gas Report - $40.18

Findings Information

Awards

Labels

External Links

[G-01] Redundant zero initialization

Recommended Mitigation Steps

[G-02] Use != 0 instead of > 0

Recommended Mitigation Steps

[G-03] Use prefix not postfix in loops

Recommended Mitigation Steps

[G-04] For loop incrementing can be unsafe

Recommended Mitigation Steps

[G-05] Use iszero assembly for zero checks

Recommended Mitigation Steps

[G-06] Save gas with unchecked

Recommended Mitigation Steps

[G-07] Add payable to functions that won't receive ETH

Recommended Mitigation Steps

[G-08] Add payable to constructors that won't receive ETH

Recommended Mitigation Steps

[G-09] Use internal function in place of modifier

Recommended Mitigation Steps

[G-10] Use uint not bool

Recommended Mitigation Steps

[G-11] Use uint256 not smaller ints

Recommended Mitigation Steps

[G-12] Use newer solidity version

Recommended Mitigation Steps

[G-13] Use Solidity errors instead of require

Recommended Mitigation Steps

[G-14] Use simple comparison in if statement

Recommended Mitigation Steps

[G-15] Bitshift for divide by 2

Recommended Mitigation Steps

[G-16] Non-public variables save gas

Recommended Mitigation Steps

[G-17] Use calldata instead of memory for function arguments

Recommended Mitigation Steps

[G-18] Write contracts in vyper

Recommended Mitigation Steps

#0 - 0xble2022-09-26T01:07:14Z

#0 - 0xble
2022-09-26T01:07:14Z