Nouns DAO contest - 0xkatana's results

A DAO-driven NFT project on Ethereum.

General Information

Platform: Code4rena

Start Date: 22/08/2022

Pot Size: $50,000 USDC

Total HM: 4

Participants: 160

Period: 5 days

Judge: gzeon

Total Solo HM: 2

Id: 155

League: ETH

Nouns DAO

Findings Distribution

Researcher Performance

Rank: 42/160

Findings: 2

Award: $52.41

🌟 Selected for report: 0

🚀 Solo Findings: 0

External Links

Code4rena Contest Page Github Contest Repository Github Findings Repository Nouns DAO

Findings Information

🌟 Selected for report: IllIllI

Also found by: 0bi, 0x040, 0x1337, 0x1f8b, 0xDjango, 0xNazgul, 0xNineDec, 0xRajeev, 0xSky, 0xSmartContract, 0xbepresent, 0xkatana, 0xmatt, 8olidity, Aymen0909, Bjorn_bug, Bnke0x0, CertoraInc, Ch_301, Chom, CodingNameKiki, Deivitto, DevABDee, DimitarDimitrov, Dravee, ElKu, Funen, GalloDaSballo, GimelSec, Guardian, Haruxe, JC, JansenC, Jeiwan, JohnSmith, KIntern_NA, Lambda, LeoS, Noah3o6, Olivierdem, R2, RaymondFam, Respx, ReyAdmirado, Rohan16, Rolezn, Ruhum, Saintcode_, Sm4rty, SooYa, Soosh, TomJ, Tomo, Trabajo_de_mates, Waze, _Adam, __141345__, ajtra, android69, asutorufos, auditor0517, berndartmueller, bobirichman, brgltd, c3phas, cRat1st0s, carlitox477, catchup, cccz, csanuragjain, d3e4, delfin454000, dipp, djxploit, durianSausage, erictee, exd0tpy, fatherOfBlocks, gogo, hyh, ladboy233, lukris02, mics, mrpathfindr, natzuu, oyc_109, p_crypt0, pashov, pauliax, pfapostol, prasantgupta52, rajatbeladiya, rbserver, ret2basic, rfa, robee, rokinot, rvierdiiev, sach1r0, saian, seyni, shenwilly, sikorico, simon135, sryysryy, sseefried, throttle, tnevler, tonisives, wagmi, xiaoming90, yixxas, z3s, zkhorse, zzzitron

Awards

35.4386 USDC - $35.44

Labels

bug

QA (Quality Assurance)

old-submission-method

External Links

Link to GitHub issue

[L-01] `initialize` functions can be frontrun

The initialize function that initializes important contract state can be called by anyone.
See:

NounsDAOLogicV2.initialize
NounsDAOLogicV1.initialize

An unauthorized party can initialize the contract before the legitimate deployer, hoping that the victim continues to use the same contract.
In the best case for the victim, they notice it and have to redeploy their contract costing gas.

Recommended Mitigation Steps

For initializing proxy contracts, deploy contracts using a factory contract that immediately calls initialize after deployment or make sure to call it immediately after deployment and verify the transaction succeeded.

Findings Information

🌟 Selected for report: IllIllI

Also found by: 0x040, 0x1f8b, 0xDjango, 0xNazgul, 0xNineDec, 0xSmartContract, 0xbepresent, 0xc0ffEE, 0xkatana, 2997ms, ACai, Amithuddar, Aymen0909, Ben, BipinSah, Bjorn_bug, Bnke0x0, CertoraInc, Ch_301, Chom, CodingNameKiki, Deivitto, DevABDee, DimitarDimitrov, Diraco, Dravee, ElKu, EthLedger, Fitraldys, Funen, GalloDaSballo, GimelSec, Guardian, IgnacioB, JC, JohnSmith, Junnon, KIntern_NA, Lambda, LeoS, Noah3o6, Olivierdem, Polandia94, R2, Randyyy, RaymondFam, Respx, ReyAdmirado, Rohan16, RoiEvenHaim, Rolezn, Ruhum, SaharAP, Saintcode_, SerMyVillage, Shishigami, Sm4rty, SooYa, TomJ, Tomio, Tomo, Waze, Yiko, _Adam, __141345__, a12jmx, ajtra, ak1, bobirichman, brgltd, bulej93, c3phas, cRat1st0s, carlitox477, catchup, ch0bu, d3e4, delfin454000, djxploit, durianSausage, erictee, exolorkistis, fatherOfBlocks, francoHacker, gogo, hyh, ignacio, jag, joestakey, karanctf, ladboy233, lucacez, lukris02, m_Rassska, martin, medikko, mics, mrpathfindr, natzuu, newfork01, oyc_109, pauliax, peritoflores, pfapostol, prasantgupta52, rbserver, ret2basic, rfa, robee, rokinot, rotcivegaf, rvierdiiev, sach1r0, saian, samruna, seyni, shark, shr1ftyy, sikorico, simon135, sryysryy, tay054, tnevler, wagmi, zishansami

Awards

16.9732 USDC - $16.97

Labels

bug

G (Gas Optimization)

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] Split up require statements instead of &&

Combining require statement conditions with && logic uses unnecessary gas. It is better to split up each part of the logical statement into a separate require statements

One example is

require(msg.sender == pendingAdmin && msg.sender != address(0), 'NounsDAO::_acceptAdmin: pending admin only');

This can be improved to

require(msg.sender == pendingAdmin);
require(msg.sender != address(0));

Recommended Mitigation Steps

Use separate require statements instead of concatenating with &&

[G-03] Cache array length before loop

Caching the array length outside a loop saves reading it on each iteration, as long as the array's length is not changed during the loop. This saves gas.

Recommended Mitigation Steps

Cache the array length before the for loop

[G-04] 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/code-423n4/2022-08-nounsdao/tree/main/contracts/governance/NounsDAOLogicV2.sol#L541 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/governance/NounsDAOLogicV2.sol#L967 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721.sol#L126 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721Checkpointable.sol#L153 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721Checkpointable.sol#L215 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721Checkpointable.sol#L218 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721Checkpointable.sol#L225

Recommended Mitigation Steps

Replace > 0 with != 0 to save gas

[G-05] Short require strings save gas

Strings in solidity are handled in 32 byte chunks. A require string longer than 32 bytes uses more gas. Shortening these strings will save gas.

Recommended Mitigation Steps

Shorten all require strings to less than 32 characters

[G-06] 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.

Recommended Mitigation Steps

Use prefix not postfix to increment in a loop

[G-07] 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-08] 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-09] 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 no underflow from subtraction was found include https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721Checkpointable.sol#L173 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721Checkpointable.sol#L182

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-10] 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.

Locations where this was found include https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/governance/NounsDAOProxy.sol#L41 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721.sol#L73

Recommended Mitigation Steps

Add payable to these functions for gas savings

[G-11] 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-12] 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.

Recommended Mitigation Steps

Replace smaller int or uint variables with uint256 variables

[G-13] Use newer solidity version

A solidity version before 0.8.6 is used in this project. The latest release of solidity includes changes that can provide gas savings. The improvements include:

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-14] 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

Recommended Mitigation Steps

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

[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/code-423n4/2022-08-nounsdao/tree/main/contracts/governance/NounsDAOLogicV2.sol#L951 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/base/ERC721Checkpointable.sol#L184

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.

Many cases of function arguments using memory instead of calldata can use this improvement to save gas https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/governance/NounsDAOLogicV2.sol#L185-L188 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/governance/NounsDAOLogicV1.sol#L175-L178

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

[G-19] Use `abi.encodePacked()` not `abi.encode()`

Changing abi.encode to abi.encodePacked can save gas. abi.encode pads extra null bytes at the end of the call data which is normally unnecessary. In general, abi.encodePacked is more gas-efficient.

There are many places where this change can be made: https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/governance/NounsDAOLogicV2.sol#L313 https://github.com/code-423n4/2022-08-nounsdao/tree/main/contracts/governance/NounsDAOLogicV1.sol#L302

Recommended Mitigation Steps

Change abi.encode to abi.encodePacked

Nouns DAO contest - 0xkatana's results

A DAO-driven NFT project on Ethereum.

General Information

Findings Distribution

Researcher Performance

External Links

[Q-94] QA Report - $35.44

Findings Information

Awards

Labels

External Links

[L-01] initialize functions can be frontrun

Recommended Mitigation Steps

[G-21] Gas Report - $16.97

Findings Information

Awards

Labels

External Links

[G-01] Redundant zero initialization

Recommended Mitigation Steps

[G-02] Split up require statements instead of &&

Recommended Mitigation Steps

[G-03] Cache array length before loop

Recommended Mitigation Steps

[G-04] Use != 0 instead of > 0

Recommended Mitigation Steps

[G-05] Short require strings save gas

Recommended Mitigation Steps

[G-06] Use prefix not postfix in loops

Recommended Mitigation Steps

[G-07] For loop incrementing can be unsafe

Recommended Mitigation Steps

[G-08] Use iszero assembly for zero checks

Recommended Mitigation Steps

[G-09] Save gas with unchecked

Recommended Mitigation Steps

[G-10] Add payable to constructors that won't receive ETH

Recommended Mitigation Steps

[G-11] Use uint not bool

Recommended Mitigation Steps

[G-12] Use uint256 not smaller ints

Recommended Mitigation Steps

[G-13] Use newer solidity version

Recommended Mitigation Steps

[G-14] Use Solidity errors instead of require

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

[G-19] Use abi.encodePacked() not abi.encode()

Recommended Mitigation Steps

[L-01] `initialize` functions can be frontrun

[G-19] Use `abi.encodePacked()` not `abi.encode()`