Overview

About C4

Code4rena (C4) is an open organization consisting of security researchers, auditors, developers, and individuals with domain expertise in smart contracts.

A C4 audit contest is an event in which community participants, referred to as Wardens, review, audit, or analyze smart contract logic in exchange for a bounty provided by sponsoring projects.

During the audit contest outlined in this document, C4 conducted an analysis of the ENS smart contract system written in Solidity. The audit contest took place between July 12—July 19 2022.

Wardens

107 Wardens contributed reports to the ENS contest:

1. PwnedNoMore (izhuer, ItsNio, papr1ka2, and wen)
2. zzzitron
3. panprog
4. GimelSec (rayn and sces60107)
5. 0x52
6. alan724
7. csanuragjain
8. 0x1f8b
9. wastewa
10. Aussie_Battlers (sseefried and oyc_109)
11. brgltd
12. cryptphi
13. peritoflores
14. cccz
15. Lambda
16. IllIllI
17. Dravee
18. bin2chen
19. 0x29A (0x4non and rotcivegaf)
20. Limbooo
21. ronnyx2017
22. joestakey
23. rbserver
24. 0xKitsune
25. benbaessler
26. Sm4rty
27. berndartmueller
28. Bnke0x0
29. Deivitto
30. RedOneN
31. CRYP70
32. gogo
33. Amithuddar
34. hake
35. TomJ
36. MiloTruck
37. Rolezn
38. c3phas
39. Ruhum
40. Ch_301
41. _Adam
42. hyh
43. __141345__
44. asutorufos
45. fatherOfBlocks
46. 0xNineDec
47. rajatbeladiya
48. 0xNazgul
49. robee
50. sashik_eth
51. Funen
52. kyteg
53. Waze
54. JC
55. JohnSmith
56. Rohan16
57. bulej93
58. cRat1st0s
59. rokinot
60. delfin454000
61. 8olidity
62. sach1r0
63. ReyAdmirado
64. zuhaibmohd
65. lcfr_eth
66. simon135
67. seyni
68. cryptonue
69. ElKu
70. dxdv
71. pashov
72. 0xf15ers (remora and twojoy)
73. p_crypt0
74. Critical
75. pedr02b2
76. philogy
77. 0xDjango
78. rishabh
79. svskaushik
80. RustyRabbit
81. minhtrng
82. exd0tpy
83. m_Rassska
84. durianSausage
85. ajtra
86. Tomio
87. 0x040
88. 0xsam
89. Aymen0909
90. Fitraldys
91. lucacez
92. Noah3o6
93. samruna
94. arcoun
95. karanctf
96. sahar
97. ak1
98. Chom
99. Jujic
100. scaraven

This contest was judged by LSDan.

Final report assembled by liveactionllama.

Summary

The C4 analysis yielded an aggregated total of 16 unique vulnerabilities. Of these vulnerabilities, 3 received a risk rating in the category of HIGH severity and 13 received a risk rating in the category of MEDIUM severity.

Additionally, C4 analysis included 71 reports detailing issues with a risk rating of LOW severity or non-critical. There were also 70 reports recommending gas optimizations.

All of the issues presented here are linked back to their original finding.

Scope

The code under review can be found within the C4 ENS contest repository, and is composed of 23 smart contracts written in the Solidity programming language and includes 2,132 lines of Solidity code.

Severity Criteria

C4 assesses the severity of disclosed vulnerabilities according to a methodology based on OWASP standards.

Vulnerabilities are divided into three primary risk categories: high, medium, and low/non-critical.

High-level considerations for vulnerabilities span the following key areas when conducting assessments:

• Malicious Input Handling
• Escalation of privileges
• Arithmetic
• Gas use

Further information regarding the severity criteria referenced throughout the submission review process, please refer to the documentation provided on the C4 website.

High Risk Findings (3)

[H-01] It is possible to create fake ERC1155 NameWrapper token for subdomain, which is not owned by NameWrapper

Submitted by panprog, also found by Aussie_Battlers, brgltd, cryptphi, peritoflores, and wastewa

NameWrapper.sol#L820-L821
NameWrapper.sol#L524
NameWrapper.sol#L572

Due to re-entrancy possibility in NameWrapper._transferAndBurnFuses (called from setSubnodeOwner and setSubnodeRecord), it is possible to do some stuff in onERC1155Received right after transfer but before new owner and new fuses are set. This makes it possible, for example, to unwrap the subdomain, but owner and fuses will still be set even for unwrapped domain, creating fake ERC1155 NameWrapper token for domain, which is not owned by NameWrapper.

Fake token creation scenario:

1. Account1 registers and wraps test.eth domain
2. Account1 calls NameWrapper.setSubnodeOwner for sub.test.eth subdomain with Account1 as owner (to make NameWrapper owner of subdomain)
3. Contract1 smart contract is created, which calls unwrap in its onERC1155Received function, and a function to send sub.test.eth ERC1155 NameWrapper token back to Account1
4. Account1 calls NameWrapper.setSubnodeOwner for sub.test.eth with Contract1 as new owner, which unwraps domain back to Account1 but due to re-entrancy, NameWrapper sets fuses and ownership to Contract1
5. Account1 calls function to send ERC1155 token from Contract1 back to self.

After this sequence of events, sub.test.eth subdomain is owned by Account1 both in ENS registry and in NameWrapper (with fuses and expiry correctly set to the future date). Lots (but not all) of functions in NameWrapper will fail to execute for this subdomain, because they expect NameWrapper to have ownership of the domain in ENS, but some functions will still work, making it possible to make the impression of good domain.

At this point, ownership in NameWrapper is “detached” from ownership in ENS and Account1 can do all kinds of malcious stuff with its ERC1155 token. For example:

1. Sell subdomain to the other user, transfering ERC1155 to that user and burning PARENT_CANNOT_CONTROL to create impression that he can’t control the domain. After receiving the payment, Account1 can wrap the domain again, which burns existing ownership record and replaces with the new one with clear fuses and Account1 ownership, effectively stealing domain back from unsuspecting user, who thought that ERC1155 gives him the right to the domain (and didn’t expect that parent can clear fuses when PARENT_CANNOT_CONTROL is set).
2. Transfer subdomain to some other smart contract, which implements onERC1155Received, then take it back, fooling smart contract into believing that it has received the domain.

Proof of Concept

Copy these to test/wrapper and run:
yarn test test/wrapper/NameWrapperReentrancy.js

https://gist.github.com/panprog/3cd94e3fbb0c52410a4c6609e55b863e

Recommended Mitigation Steps

Consider adding nonReentrant modifiers with ReentrancyGuard implementation from openzeppelin. Alternatively just fix this individual re-entrancy issue. There are multiple ways to fix it depending on expected behaviour, for example saving ERC1155 data and requiring it to match the data after transfer (restricting onERC1155Received to not change any data for the token received):

function _transferAndBurnFuses(
    bytes32 node,
    address newOwner,
    uint32 fuses,
    uint64 expiry
) internal {
    (address owner, uint32 saveFuses, uint64 saveExpiry) = getData(uint256(node));
    _transfer(owner, newOwner, uint256(node), 1, "");
    uint32 curFuses;
    uint64 curExpiry;
    (owner, curFuses, curExpiry) = getData(uint256(node));
    require(owner == newOwner && saveFuses == curFuses && saveExpiry == curExpiry);
    _setFuses(node, newOwner, fuses, expiry);
}

Arachnid (ENS) confirmed

---

[H-02] The expiry of the parent node can be smaller than the one of a child node, violating the guarantee policy

Submitted by PwnedNoMore

NameWrapper.sol#L504
NameWrapper.sol#L356

By design, the child node’s expiry can only be extended up to the parent’s current one. Adding these restrictions means that the ENS users only have to look at the name itself’s fuses and expiry (without traversing the hierarchy) to understand what guarantees the users have.

When a parent node tries to setSubnodeOwner / setSubnodeRecord, the following code is used to guarantee that the new expiry can only be extended up to the current one.

function _getDataAndNormaliseExpiry(
    bytes32 parentNode,
    bytes32 node,
    uint64 expiry
)
    internal
    view
    returns (
        address owner,
        uint32 fuses,
        uint64
    )
{
    uint64 oldExpiry;
    (owner, fuses, oldExpiry) = getData(uint256(node));
    (, , uint64 maxExpiry) = getData(uint256(parentNode));
    expiry = _normaliseExpiry(expiry, oldExpiry, maxExpiry);
    return (owner, fuses, expiry);
}

However, the problem shows when

• The sub-domain (e.g., sub1.base.eth) has its own sub-sub-domain (e.g., sub2.sub1.base.eth)
• The sub-domain is unwrapped later, and thus its oldExpiry becomes zero.
• When base.eth calls NameWrapper.setSubnodeOwner, there is not constraint of sub1.base.eth’s expiry, since oldExpiry == 0. As a result, the new expiry of sub1.base.eth can be arbitrary and smaller than the one of sub2.sub1.base.eth

The point here is that the oldExpiry will be set as 0 when unwrapping the node even it holds child nodes, relaxing the constraint.

Specifically, considering the following scenario

• The hacker owns a domain (or a 2LD), e.g., base.eth

• The hacker assigns a sub-domain to himself, e.g., sub1.base.eth

  • The expiry should be as large as possible

• Hacker assigns a sub-sub-domain, e.g., sub2.sub1.base.eth

  • The expiry should be as large as possible
• The hacker unwraps his sub-domain, i.e., sub1.base.eth

• The hacker re-wraps his sub-domain via NameWrapper.setSubnodeOwner

  • The expiry can be small than the one of sub2.sub1.base.eth

The root cause seems that we should not zero out the expiry when burning a node if the node holds any subnode.

Suggested Fix

• Potential fix 1: auto-burn CANNOT_UNWRAP which thus lets expiry decide whether a node can be unwrapped.
• Potential fix 2: force the parent to have CANNOT_UNWRAP burnt if they want to set expiries on a child via setSubnodeOwner / setSubnodeRecord / setChildFuses

Proof of Concept / Attack Scenario

For full details, please see original warden submission.

Arachnid (ENS) confirmed

---

[H-03] PARENT_CANNOT_CONTROL can be bypassed by maliciously unwrapping parent node

Submitted by PwnedNoMore, also found by panprog, and zzzitron

NameWrapper.sol#L356
NameWrapper.sol#L295
ENSRegistry.sol#L74

By design, for any subdomain, as long as its PARENT_CANNOT_CONTROL fuse is burnt (and does not expire), its parent should not be able to burn its fuses or change its owner.

However, this contraint can be bypassed by a parent node maliciously unwrapping itself. As long as the hacker becomes the ENS owner of the parent node, he can leverage ENSRegistry::setSubnodeOwner to re-set himself as the ENS owner of the subdomain, and thus re-invoking NameWrapper.wrap can rewrite the fuses and wrapper owner of the given subdoamin.

Considering the following attack scenario:

• Someone owns a domain (or a 2LD), e.g., poc.eth

• The domain owner assigns a sub-domain to the hacker, e.g., hack.poc.eth

  • This sub-domain should not burn CANNOT_UNWRAP
  • This sub-domain can burn PARENT_CANNOT_CONTROL
• Hacker assigns a sub-sub-domain to a victim user, e.g., victim.hack.poc.eth

• The victim user burns arbitrary fuses, including PARENT_CANNOT_CONTROL

  • The hacker should not be able to change the owner and the fuses of victim.hack.poc.eth ideally
• However, the hacker then unwraps his sub-domain, i.e., hack.poc.eth

• The hacker invokes ENSRegistry::setSubnodeOwner(hacker.poc.eth, victim) on the sub-sub-domain

  • He can reassign himself as the owner of the victim.hack.poc.eth
• The hacker invokes NameWrapper.wrap(victim.hacker.poc.eth) to over-write the fuses and owner of the sub-sub-domain, i.e., victim.hacker.poc.eth

The root cause here is that, for any node, when one of its subdomains burns PARENT_CANNOT_CONTROL, the node itself fails to burn CANNOT_UNWRAP. Theoretically, this should check to the root, which however is very gas-consuming.

Suggested Fix

• Potential fix 1: auto-burn CANNOT_UNWRAP which thus lets expiry decide whether a node can be unwrapped.
• Potential fix 2: leave fuses as is when unwrapping and re-wrapping, unless name expires. Meanwhile, check the old fuses even wrapping.

Proof of Concept / Attack Scenario

For full details, please see original warden submission.

Arachnid (ENS) confirmed

---

Medium Risk Findings (13)

[M-01] wrapETH2LD permissioning is over-extended

Submitted by 0x52

Undesired use of ENS wrapper.

Proof of Concept

NameWrapper.sol#L219-L223

Current permissioning for wrapETH2LD allows msg.senders who are not owner to call it if they are EITHER approved for all on the ERC721 registrar or approved on the wrapper. Allowing users who are approved for the ERC721 registrar makes sense. By giving them approval, you are giving them approval to do what they wish with the token. Any other restrictions are moot regardless because they could use approval to transfer themselves the token anyways and bypass them as the new owner. The issue is allowing users who are approved for the wrapper contract to wrap the underlying domain. By giving approval to the contract the user should only be giving approval for the wrapped domains. As it is currently setup, once a user has given approval on the wrapper contract they have essentially given approval for every domain, wrapped or unwrapped, because any unwrapped domain can be wrapped and taken control of. This is an over-extension of approval which should be limited to the tokens managed by the wrapper contract and not extend to unwrapped domains

Recommended Mitigation Steps

Remove L221.

Arachnid (ENS) disagreed with severity and commented:

This was by design, but the warden raises a good point about the implications of this permission model. Recommend downgrading to QA.

LSDan (judge) decreased severity to Medium and commented:

I’m going to downgrade this to medium. There are not assets at direct risk, but with external factors the assets could be at risk due to the user being unaware that in approving wrapped domains, they are also approving unwrapped domains.

---

[M-02] Renew of 2nd level domain is not done properly

Submitted by csanuragjain, also found by cccz and GimelSec

ETHRegistrarController.sol#L201
NameWrapper.sol#L271

The ETHRegistrarController is calling renew from base registrar and not through Namewrapper. This means the fuses for the subdomain will not be updated via _setData. This impacts the permission model set over subdomain and could lead to takeover

Proof of Concept

1. Observe the renew function

function renew(string calldata name, uint256 duration)
        external
        payable
        override
    {
        ...

        uint256 expires = base.renew(uint256(label), duration);

        ....
    }

2. As we can see this is calling renew function of Base Registrar instead of NameWrapper. Since this is not going via NameWrapper fuses will not be set
3. Also since renew in NameWrapper can only be called via Controller which is ETHRegistrarController so there is no way to renew subdomain

Recommended Mitigation Steps

The ETHRegistrarController must renew using Namewrapper’s renew contract.

Arachnid (ENS) commented:

Duplicate of #223.

LSDan (judge) commented:

On #223, which I’ve invalidated, @Arachnid notes that:

In fact, this should only be severity QA, as it can be worked around by calling renew on the registrar controller followed by setChildFuses.

I’m going to make this report the main one and leave the risk rating of Medium in place. While there is a workaround, if the workaround is not employed, permissions will be incorrect and may lead to a breakdown in the functioning of the protocol.

---

[M-03] transfer() depends on gas consts

Submitted by rajatbeladiya, also found by __141345__, _Adam, 0x29A, 0xNineDec, alan724, Amithuddar, asutorufos, Aussie_Battlers, berndartmueller, c3phas, cccz, Ch_301, cryptphi, csanuragjain, Dravee, durianSausage, fatherOfBlocks, GimelSec, hake, hyh, IllIllI, Jujic, Limbooo, pashov, RedOneN, Ruhum, scaraven, TomJ, and zzzitron

ETHRegistrarController.sol#L183-L185
ETHRegistrarController.sol#L204

transfer() forwards 2300 gas only, which may not be enough in future if the recipient is a contract and gas costs change. it could break existing contracts functionality.

Proof of Concept

.transfer or .send method, only 2300 gas will be “forwarded” to fallback function. Specifically, the SLOAD instruction, will go from costing 200 gas to 800 gas.

If any smart contract has a functionality of register ens and it has fallback function which is making some state change in contract on ether receive, it could use more than 2300 gas and revert every transaction.

For reference, check out:

• https://docs.soliditylang.org/en/v0.8.15/security-considerations.html?highlight=transfer#sending-and-receiving-ether
• https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/

Recommended Mitigation Steps

Use .call insted .transfer

 (bool success, ) = msg.sender.call.value(amount)("");
 require(success, "Transfer failed.");

jefflau (ENS) confirmed, but disagreed with severity and commented:

Recommend reducing severity to QA

LSDan (judge) decreased severity to Medium and commented:

I’m downgrading this to Medium. There are external factors required to make this problem occur, but if it does the functionality of the protocol as a whole could be severely impacted.

Arachnid (ENS) commented:

It’s unclear to me how this could be a significant issue. Anyone writing code to register names knows that any excess funds will be returned, and therefore that they need a fallback that consumes minimal gas. Any EVM change that increases the gas of fallback functions would be breaking for a great number of contracts beyond ENS.

LSDan (judge) commented:

It’s unclear to me how this could be a significant issue.

The register functions will fail, consuming a good bit of gas along the way if this occurs. If this were not such a critical piece of functionality I would have considered it QA, but a failure here breaks the protocol.

Anyone writing code to register names knows that any excess funds will be returned, and therefore that they need a fallback that consumes minimal gas. Any EVM change that increases the gas of fallback functions would be breaking for a great number of contracts beyond ENS.

The fact that other contracts will break along with ENS does not invalidate the issue. This is a clearly documented problem that has been known for years (see ref links). There is no reason to introduce more critical contracts to the ecosystem that will fail in this scenario, particularly when it is so easy to avoid.

Arachnid (ENS) commented:

The register functions will fail, consuming a good bit of gas along the way if this occurs. If this were not such a critical piece of functionality I would have considered it QA, but a failure here breaks the protocol.

I think the implied API here is that any contract registering names with the controller must either send the right amount of ether, or have a fallback function that can accept ether. Changes to the consensus layer that invalidate that assumption for a given contract are out-of-scope for ENS.

Sending all remaining gas with the refund increases the threat surface by allowing possible reentrancy etc, which we haven’t examined as a threat model here.

---

[M-04] BytesUtil.compare returns wrong result on some strings longer than 32 characters

Submitted by panprog, also found by alan724 and GimelSec

BytesUtils.sol#L66-L70

Due to incorrect condition in ByteUtil.compare function, irrelevant characters are masked out only for strings shorter than 32 characters. However, they must be masked out for strings of all lengths in the last pass of the loop (when remainder of the string is 32 characters or less). This leads to incorrect comparision of strings longer than 32 characters where len or otherlen is smaller than string length (characters beyond provided length are still accounted for in the comparision in this case while they should be ignored).

This wrong compare behaviour also makes RRUtils.compareNames fail to correctly compare DNS names in certain cases.

While the BytesUtil.compare and RRUtils.compareNames methods are currently not used in the functions in the scope (but are used in mainnet’s DNSSECImpl.checkNsecName, which is out of scope here), they’re public library functions relied upon and can be used by the other users or the ENS project in the future. And since the functions in scope provide incorrect result, that’s a wrong (unexpected) behaviour of the smart contract. Moreover, since the problem can be seen only with the large strings (more than 32 characters), this might go unnoticed with any code that uses compare or compareNames method and can potentially lead to high security risk of any integration project or ENS itself.

Example strings to compare which give incorrect result: 01234567890123450123456789012345ab 01234567890123450123456789012345aa

Each string is 34 characters long, first 33 characters are the same, the last one is different. If we compare first 33 characters of both strings, the result should be equal (as they only differ in the 34th character), but compare will return >, because it fails to ignore the last character of both strings and simply compares strings themselves.

If we compare the first 33 characters from the first string vs all 34 characters of the second string, the result of compare will be >, while the correct result is <, because compare fails to ignore the last character of the first string.

Example dns names to compare which give incorrect result:
01234567890123456789012345678901a0.0123456789012345678901234567890123456789012345678.eth
01234567890123456789012345678901a.0123456789012345678901234567890123456789012345678.eth

The first dns name should come after the second, but dnsCompare returns -1 (the first name to come before), because the length of the 2nd domain (49 characters) is ASCII character 1 and is not correctly masked off during strings comparision.

Proof of Concept

git diff

https://gist.github.com/panprog/32adefdc853ccd0fd0f1aad85c526bea

then:

yarn test test/dnssec-oracle/TestSolidityTests.js

Recommended Mitigation Steps

In addition to the incorrect condition, the mask calculation formula: 32 - shortest + idx will also overflow since shortest can be more than 32, so addition should be performed before subtractions.

            if (shortest - idx >= 32) {
                mask = type(uint256).max;
            } else {
                mask = ~(2 ** (8 * (idx + 32 - shortest)) - 1);
            }

Arachnid (ENS) confirmed

---

[M-05] DNSSECImpl.verifySignature compares strings incorrectly, allowing malicious zones to forge DNSSEC trust chain

Submitted by GimelSec, also found by csanuragjain

DNSSECImpl.sol#L186-L190

DNSSEC allows parent zones to sign for its child zones. To check validity of a signature, RFC4034 3.1.7 requires the Signer's Name in any RRSIG RDATA to contain the zone of covered RRset. This requirement is reasonable since any child zone should be covered by its parent zone.

ENS tries to implement the concept of name coverage in DNSSECImpl.verifySignature, but unfortuantely does it wrong, resulting in possibiliy of coverage between two unrelated domains. In the worst case, an attacker can utilize this bug to forge malicious trust chains and authenticate invalid domains.

Proof of Concept

In DNSSECImpl.verifySignature, ENS tries to verify the name of RRSet zone (name) is contained by Signer’s Name (rrset.signerName).

    if(rrset.signerName.length > name.length
            || !rrset.signerName.equals(0, name, name.length - rrset.signerName.length))    //## This allows matches such as name="SubString.com" signerName="String.com", which is clearly incorrect, use label counts instead
        {
            revert InvalidSignerName(name, rrset.signerName);
        }

In DNS, for a parent zone to contain another child zone, we generally require the child zone to be a subdomain of the parent. For instance, example.eth. in considered to cover sub.example.eth., while xample.eth. should not be cover example.eth..

Unfortunately in the implementation shown above, both cases will path the check, and ample.eth. will be considered appropriate to sign for example.eth.. This is against the original design of DNS, and would result in breach of zone hierarchy.

In practice, the requirement to exploit this is a bit more complex. Since names are stored as a sequence of packed labels, example.eth. should be stored as \x06example\x03eth\x00, while xample.eth. is stored as \x05xample\x03eth\x00. Thus to successfully pull off the attack ,we have to make sure that the packed signer’s name is actually a substring of child zone.

A simple (yet unrealistic) example can be like this xample.eth. can sign for e\x05xample.eth., since packed format of those two names are \x05xample\x03eth\x00 and \x07e\x05ample\x03eth\x00.

In general, it would require some effort for an attacker to find attackable zones, nevertheless, this should still be considered as a potential threat to the integrity of ENS.

Recommended Mitigation Steps

Check label by label instead of comparing the entire name.
To actually meet all requirements specified in RFC4034 and RFC4035, there are still a lot to do, but we will discuss that in a separate issue for clarity.

Arachnid (ENS) disagreed with severity and commented:

This is a valid issue, but unexploitable in the wild; RFC 1035 specifies labels are limited to 63 octets or less, and the ASCII code of lowercase ‘a’ is 97. As a result, no vulnerable names should exist.

Recommend that this be triaged as severity 2 as a result.

LSDan (judge) decreased severity to Medium and commented:

I agree with @Arachnid on this. The lack of real world likelihood makes this a Medium severity.

---

[M-06] BytesUtils: compare will not revert when the offset and len exceeds the bytes lengths

Submitted by zzzitron

BytesUtils.sol#L44-L51

Compare will return false answer without reverting when the inputs are not valid.

Proof of Concept

The compare function is used for compareNames. The names are supposed to be DNS wire format. If the strings are malformed, it is possible to give out-of-range offset, len, otheroffset, and otherlen. When it happens, the compare will return some false values, without reverting, since the validity of offset and len are not checked.

// dnssec-oracle/BytesUtils.sol::compare
// The length of self and other are not enforced

 44     function compare(bytes memory self, uint offset, uint len, bytes memory other, uint otheroffset, uint otherlen) internal pure returns (int) {
 45         uint shortest = len;
 46         if (otherlen < len)
 47         shortest = otherlen;
 48
 49         uint selfptr;
 50         uint otherptr;

Recommended Mitigation Steps

Check whether the offset, len are within the length of self, as well as for the other.

makoto (ENS) acknowledged and commented:

It’s lacking enough test to prove the bug.

Arachnid (ENS) confirmed and commented:

compareNames does not sanity check the lengths passed in, so this is a legitimate bug.

---

[M-07] If PARENT_CANNOT_CONTROL is set on subdomain, it can be unwrapped then wrapped by its owner and then parent can control it again before the expiry

Submitted by panprog

NameWrapper.sol#L955-L961

There is a general incorrect logic of allowing to burn only PARENT_CANNOT_CONTROL fuse without burning CANNOT_UNWRAP fuse. If only PARENT_CANNOT_CONTROL fuse is burnt, then domain can be unwrapped by its owner and then wrapped again, which clears PARENT_CANNOT_CONTROL fuse, making it possible for parent to bypass the limitation of parent control before the expiry.

Bypassing parent control scenario:

1. Alice registers and wraps test.eth domain
2. Alice creates subdomain bob.test.eth and burns PARENT_CANNOT_CONTROL fuse with max expiry, transferring this domain to Bob
3. At this point Bob can verify that he is indeed domain owner of bob.test.eth in NameWrapper, PARENT_CANNOT_CONTROL fuse is burnt for this domain and fuse expiry is set to expiry of test.eth domain. So Bob thinks his domain is secure and can not be taken from him before the expiry.
4. Bob unwraps bob.test.eth domain.
5. Bob wraps bob.test.eth domain, which clears fuses and expiry
6. Alice changes bob.test.eth domain ownership to her breaking Bob’s impression that his domain was secure until expiry.

Proof of Concept

Copy this to test/wrapper and run:
yarn test test/wrapper/NameWrapperBypassPCC.js

https://gist.github.com/panprog/71dea0fd1875b4d7d5849f7da822ea8b

Recommended Mitigation Steps

Burning any fuse (including PARENT_CANNOT_CONTROL) must require CANNOT_UNWRAP fuse to be burned (because otherwise it’s possible to unwrap+wrap to clear that fuse).

In NameWrapper._canFusesBeBurned, condition should be different:

    if (
        fuses & ~CANNOT_UNWRAP != 0 &&
        fuses & (PARENT_CANNOT_CONTROL | CANNOT_UNWRAP) !=
        (PARENT_CANNOT_CONTROL | CANNOT_UNWRAP)
    ) {
        revert OperationProhibited(node);
    }

jefflau (ENS) commented:

A mitigation step for this could be to not burn fuses when unwrapping domains to prevent the PARENT_CANNOT_CONTROL from being reset.

Arachnid (ENS) disagreed with severity and commented:

Since this has to be self-inflicted by the victim, this should be severity 2.

LSDan (judge) decreased severity to Medium and commented:

Agree with the sponsor that this is a medium severity issue due to the external requirement that Bob unwraps and rewraps the domain. Additionally, this requires Alice to all of a sudden become a bad actor, making it highly unlikely that this would occur.

---

[M-08] Wrong Equals Logic

Submitted by 0x1f8b, also found by alan724

BytesUtils.sol#L115-L127

equals with offset might return true when equals without offset returns false.

Proof of Concept

The problem is that self.length could be greater than other.length + offset, it should be ==, or it should contain a length argument.

Here you have an example of the failure:

• equals(0x0102030000, 0, 0x010203) => return true

decoded input	{
	"bytes self": "0x0102030000",
	"uint256 offset": "0",
	"bytes other": "0x010203"
}
decoded output	{
	"0": "bool: true"
}

Recommended Mitigation Steps

    function equals(bytes memory self, uint offset, bytes memory other) internal pure returns (bool) {
-       return self.length >= offset + other.length && equals(self, offset, other, 0, other.length);
+       return self.length == offset + other.length && equals(self, offset, other, 0, other.length);
    }

makoto (ENS) confirmed

---

[M-09] The unwrapETH2LD use transferFrom instead of safeTransferFrom to transfer ERC721 token

Submitted by 0x29A, also found by Amithuddar, benbaessler, berndartmueller, cccz, CRYP70, rbserver, RedOneN, and Sm4rty

NameWrapper.sol#L327-L346

The unwrapETH2LD use transferFrom to transfer ERC721 token, the newRegistrant could be an unprepared contract.

Proof of Concept

Should a ERC-721 compatible token be transferred to an unprepared contract, it would end up being locked up there. Moreover, if a contract explicitly wanted to reject ERC-721 safeTransfers.
Plus take a look to the OZ safeTransfer comments:
Usage of this method is discouraged, use safeTransferFrom whenever possible.

Recommended Mitigation Steps

    function unwrapETH2LD(
        bytes32 labelhash,
        address newRegistrant,
        address newController
    ) public override onlyTokenOwner(_makeNode(ETH_NODE, labelhash)) {
        _unwrap(_makeNode(ETH_NODE, labelhash), newController);
-       registrar.transferFrom(
+       registrar.safeTransferFrom(
            address(this),
            newRegistrant,
            uint256(labelhash)
        );
    }

jefflau (ENS) disputed and commented:

Transfer is to the contract itself, so there is no point in using safeTransferFrom. For other situations where transferFrom the behaviour is intended.

LSDan (judge) commented:

Transfer is to the contract itself, so there is no point in using safeTransferFrom. For other situations where transferFrom the behaviour is intended.

That’s incorrect in the report above. This is transferring from, not to, the contract itself.

jefflau (ENS) commented:

That’s incorrect in the report above. This is transferring from, not to, the contract itself.

Yes sorry, that is true. I was replying to some of the duplicates that I closed such as: #126, #147.

---

[M-10] Incorrect implementation of RRUtils.serialNumberGte

Submitted by GimelSec, also found by Lambda and zzzitron

RRUtils.sol#L266-L268

Comparing serial numbers should follow RFC1982 due to the possibility of numbers wrapping around. RRUtils.serialNumberGte tried to follow the RFC but failed to do so, leading to incorrect results in comparison.

Proof of Concept

For a serial number i1 to be greater than i2, the rules provided by RFC1982 is as follow
((i1 < i2) && ((i2 - i1) > (2**31))) || ((i1 > i2) && ((i1 - i2) < (2**31)))

ENS implements int32(i1) - int32(i2) > 0, which will suffer from revert in cases such as i1=0x80000000, i2=0x7fffffff

Recommended Mitigation Steps

Use the naive implementation instead
return (i1 == i2) || ((i1 < i2) && ((i2 - i1) > (2**31))) || ((i1 > i2) && ((i1 - i2) < (2**31)));

Arachnid (ENS) disagreed with severity and commented:

This is intentional, see https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_solution

Nevertheless, this should be documented. Recommend triaging as QA.

Arachnid (ENS) commented:

Correction - while the operation is correct per the Wikipedia article, it should be in an unchecked block to allow overflow. Recommend triaging as 2.

LSDan (judge) decreased severity to Medium and commented:

Agree with the sponsor. This is a bug and it does potentially impact protocol functionality, but it will not occur until far in the future, making it fairly unlikely. Medium makes sense here.

---

[M-11] The preimage DB (i.e., NameWrapper.names) can be maliciously manipulated/corrupted

Submitted by PwnedNoMore

NameWrapper.sol#L520

By design, the NameWrapper.names is used as a preimage DB so that the client can query the domain name by providing the token ID. The name should be correctly stored. To do so, the NameWrapper record the domain’s name every time it gets wrapped. And as long as all the parent nodes are recorded in the DB, wrapping a child node will be very efficient by simply querying the parent node’s name.

However, within a malicious scenario, it is possible that a subdomain can be wrapped without recording its info in the preimage DB.

Specifically, when NameWrappper.setSubnodeOwner / NameWrappper.setSubnodeRecord on a given subdomain, the following code is used to check whether the subdomain is wrapped or not. The preimage DB is only updated when the subdomain is not wrapped (to save gas I beieve).

function setSubnodeOwner(
    bytes32 parentNode,
    string calldata label,
    address newOwner,
    uint32 fuses,
    uint64 expiry
)
    public
    onlyTokenOwner(parentNode)
    canCallSetSubnodeOwner(parentNode, keccak256(bytes(label)))
    returns (bytes32 node)
{
    bytes32 labelhash = keccak256(bytes(label));
    node = _makeNode(parentNode, labelhash);
    (, , expiry) = _getDataAndNormaliseExpiry(parentNode, node, expiry);
    if (ens.owner(node) != address(this)) {
        ens.setSubnodeOwner(parentNode, labelhash, address(this));
        _addLabelAndWrap(parentNode, node, label, newOwner, fuses, expiry);
    } else {
        _transferAndBurnFuses(node, newOwner, fuses, expiry);
    }
}

However, the problem is that ens.owner(node) != address(this) is not sufficient to check whether the node is alreay wrapped. The hacker can manipulate this check by simply invoking EnsRegistry.setSubnodeOwner to set the owner as the NameWrapper contract without wrapping the node.

Consider the following attack scenario.

• the hacker registers a 2LD domain, e.g., base.eth

• he assigns a subdomain for himself, e.g., sub1.base.eth

  • the expiry of sub1.base.eth should be set as expired shortly
  • note that the expiry is for sub1.base.eth instead of base.eth, so it is safe to make it soonly expired
• the hacker waits for expiration and unwraps his sub1.base.eth
• the hacker invokes ens.setSubnodeOwner to set the owner of sub2.sub1.base.eth as NameWrapper contract
• the hacker re-wraps his sub1.base.eth

• the hacker invokes nameWrapper.setSubnodeOwner for sub2.sub1.base.eth

  • as such, names[namehash(sub2.sub1.base.eth)] becomes empty

• the hacker invokes nameWrapper.setSubnodeOwner for eth.sub2.sub1.base.eth.

  • as such, names[namehash(eth.sub2.sub1.base.eth)] becomes \x03eth

It is not rated as a High issue since the forged name is not valid, i.e., without the tailed \x00 (note that a valid name should be like \x03eth\x00). However, the preimage BD can still be corrupted due to this issue.

Suggested Fix

When wrapping node X, check whether NameWrapper.names[X] is empty directly, and update the preimage DB if it is empty.

Proof of Concept / Attack Scenario

For full details, please see original warden submission.

jefflau (ENS) confirmed

---

[M-12] ERC1155Fuse: _transfer does not revert when sent to the old owner

Submitted by zzzitron

The safeTransferFrom does not comply with the ERC1155 standard when the token is sent to the old owner.

Proof of Concept

According to the EIP-1155 standard for the safeTransferFrom:

MUST revert if balance of holder for token _id is lower than the _value sent.

Let’s say alice does not hold any token of tokenId, and bob holds one token of tokenId. Then alice tries to send one token of tokenId to bob with safeTranferFrom(alice, bob, tokenId, 1, ""). In this case, even though alice’s balance (= 0) is lower than the amount (= 1) sent, the safeTransferFrom will not revert. Thus, violating the EIP-1155 standard.
It can cause problems for other contracts using this token, since they assume the token was transferred if the safeTransferFrom does not revert. However, in the example above, no token was actually transferred.

// wrapper/ERC1155Fuse.sol::_transfer
// ERC1155Fuse::safeTransferFrom uses _transfer

274     function _transfer(
275         address from,
276         address to,
277         uint256 id,
278         uint256 amount,
279         bytes memory data
280     ) internal {
281         (address oldOwner, uint32 fuses, uint64 expiry) = getData(id);
282         if (oldOwner == to) {
283             return;
284         }

Recommended Mitigation Steps

Revert even if the to address already owns the token.

jefflau (ENS) confirmed and commented:

Recommend severity QA.

LSDan (judge) commented:

I’m going to leave this as Medium. This issue could definitely impact other protocols and potentially cause a loss of funds given external factors.

---

[M-13] Users can create extra ENS records at no cost

Submitted by wastewa, also found by bin2chen, Limbooo, PwnedNoMore, and ronnyx2017

ETHRegistrarController.sol#L249-L268
ETHRegistrarController.sol#L125
BaseRegistrarImplementation.sol#L106

Users using the register function in ETHRegistrarController.sol, can create an additional bogus ENS entry (Keep the ERC721 and all the glory for as long as they want) for free by exploiting the functionCall in the _setRecords function.
The only check there (in the setRecord function) is that the nodehash matches the originally registered ENS entry, this is extremely dangerous because the rest of the functionCall is not checked and the controller has very elevated privileges in ENS ecosystem (and probably beyond).

The single exploit I am showing is already very bad, but I expect there will be more if this is left in. An example of a potential hack is that some of the functions in other ENS contracts (which give the RegistrarController elevated privilege) have dynamic types as the first variables—if users can generate a hash that is a low enough number, they will be able to unlock more exploits in the ENS ecosystem because of how dynamic types are abi encoded. Other developers will probably also trust the ETHRegistrarController.sol, so other unknown dangers may come down the road.

The exploit I made (full code in PoC) can mint another ENS entry and keep it for as long as it wants, without paying more—will show code below.

Proof of Concept

Put this code in the TestEthRegistrarController.js test suite to run. I just appended this to tests at the bottom of file.

I called the BaseRegistrarImplementation.register function with the privileges of ETHRegistrarController by passing the base registrar’s address as the resolver param in the ETHRegistrarController.register function call. I was able to set a custom duration at no additional cost.

The final checks of the PoC show that we own two new ENS entries from a single ETHRegistrarController.register call. The labelhash of the new bogus ENS entry is the nodehash of the first registered ENS entry.

  it('Should allow us to make bogus erc721 token in ENS contract', async () => {
    const label = 'newconfigname'
    const name = `${label}.eth`
    const node = namehash.hash(name)
    const secondTokenDuration = 788400000 // keep bogus NFT for 25 years;

    var commitment = await controller.makeCommitment(
      label,
      registrantAccount,
      REGISTRATION_TIME,
      secret,
      baseRegistrar.address,
      [
        baseRegistrar.interface.encodeFunctionData('register(uint256,address,uint)', [
          node,
          registrantAccount,
          secondTokenDuration
        ]),
      ],
      false,
      0,
      0
    )
    var tx = await controller.commit(commitment)
    expect(await controller.commitments(commitment)).to.equal(
      (await web3.eth.getBlock(tx.blockNumber)).timestamp
    )

    await evm.advanceTime((await controller.minCommitmentAge()).toNumber())
    var balanceBefore = await web3.eth.getBalance(controller.address)

    let tx2 = await controller.register(
      label,
      registrantAccount,
      REGISTRATION_TIME,
      secret,
      baseRegistrar.address,
      [
        baseRegistrar.interface.encodeFunctionData('register(uint256,address,uint)', [
          node,
          registrantAccount,
          secondTokenDuration
        ]),
      ],
      false,
      0,
      0,
      { value: BUFFERED_REGISTRATION_COST }
    )

    expect(await nameWrapper.ownerOf(node)).to.equal(registrantAccount)
    expect(await ens.owner(namehash.hash(name))).to.equal(nameWrapper.address)


    expect(await baseRegistrar.ownerOf(node)).to.equal( // this checks that bogus NFT is owned by us
      registrantAccount
    )
    expect(await baseRegistrar.ownerOf(sha3(label))).to.equal(
      nameWrapper.address
    )
  })

Tools Used

chai tests in repo

Recommended Mitigation Steps

I recommend being stricter on the signatures of the user-provided resolver and the function that is being called (like safeTransfer calls in existing token contracts).
An example of how to do this is by creating an interface that ENS can publish for users that want to compose their own resolvers and call that instead of a loose functionCall. Users will be free to handle data however they like, while restricting the space of things that can go wrong.

I will provide a loose example here:

interface IUserResolver {
    function registerRecords(bytes32 nodeId, bytes32 labelHash, bytes calldata extraData)

}

Arachnid (ENS) confirmed

jefflau (ENS) disagreed with severity and commented:

We left this as high severity, but this is a duplicate of this: #222 comment.

I believe this still a low severity, or at a minimum medium.

The only thing you can pass to register is the node, as the require inside setRecords checks the nodehash. However register in the baseRegistrar itself takes a label not the namehash of the name, so it will register a name with the hash of namehash(namehash('eth') + node), which will be a very useless name as the label will then be a 32 byte keccak hash so 0x123...abc.eth.

In the warden’s test he tests for the node of the account they originally wanted to buy, not the bogus nft:

expect(await baseRegistrar.ownerOf(node)).to.equal( // this checks that bogus NFT is owned by us
      registrantAccount
    )

To test for the bogus nft they would need to do:

const node2 = sha3(namehash('eth') + node)
expect(await baseRegistrar.ownerOf(node2)).to.equal( // this checks that bogus NFT is owned by us
      registrantAccount
    )

LSDan (judge) decreased severity to Medium and commented:

After a lot of consideration of this issue, I’m going to downgrade it to medium. There are two main considerations in doing this:

1. The “free” name created is essentially junk.
2. The additional potential exploits are unknown and kinda hand-wavy. If there are additional exploits in the future as a result of this they almost definitely rely on external factors that don’t exist today.

---

Low Risk and Non-Critical Issues

For this contest, 71 reports were submitted by wardens detailing low risk and non-critical issues. The report highlighted below by IllIllI received the top score from the judge.

The following wardens also submitted reports: Dravee, 0x29A, Bnke0x0, Deivitto, joestakey, rbserver, 0x1f8b, benbaessler, TomJ, dxdv, hake, Rolezn, 0xNazgul, 0xf15ers, alan724, Sm4rty, Funen, sashik_eth, Ruhum, robee, _Adam, Aussie_Battlers, Waze, brgltd, c3phas, Ch_301, hyh, Lambda, MiloTruck, p_crypt0, Rohan16, 0xNineDec, 8olidity, zzzitron, GimelSec, JC, JohnSmith, kyteg, rokinot, asutorufos, berndartmueller, bulej93, cRat1st0s, Critical, csanuragjain, delfin454000, fatherOfBlocks, sach1r0, pedr02b2, philogy, PwnedNoMore, rajatbeladiya, __141345__, 0xDjango, rishabh, zuhaibmohd, cryptphi, svskaushik, seyni, RustyRabbit, lcfr_eth, minhtrng, ReyAdmirado, pashov, bin2chen, cryptonue, ElKu, exd0tpy, simon135, and gogo.

Low Risk Issues Summary

	Issue	Instances
[L‑01]	require() should be used instead of assert()	2
[L‑02]	Missing checks for address(0x0) when assigning values to address state variables	1
[L‑03]	Open TODOs	1
[L-04]	File is missing NatSpec	10
[L-05]	NatSpec is incomplete	13

Total: 27 instances over 5 issues

Non-critical Issues Summary

	Issue	Instances
[N‑01]	Name validation is not strictly valid	1
[N‑02]	Adding a return statement when the function defines a named return variable, is redundant	1
[N‑03]	require()/revert() statements should have descriptive reason strings	17
[N‑04]	public functions not called by the contract should be declared external instead	13
[N‑05]	constants should be defined rather than using magic numbers	150
[N‑06]	Redundant cast	1
[N‑07]	Missing event and or timelock for critical parameter change	3
[N‑08]	File is missing version pragma	1
[N‑09]	Use a more recent version of solidity	7
[N‑10]	pragma experimental ABIEncoderV2 is deprecated	2
[N‑11]	Constant redefined elsewhere	1
[N‑12]	Inconsistent spacing in comments	2
[N‑13]	Lines are too long	8
[N‑14]	Inconsistent method of specifying a floating pragma	10
[N‑15]	Non-library/interface files should use fixed compiler versions, not floating ones	4
[N‑16]	Typos	5
[N‑17]	File does not contain an SPDX Identifier	14
[N‑18]	Event is missing indexed fields	18
[N‑19]	Not using the named return variables anywhere in the function is confusing	4
[N‑20]	Duplicated require()/revert() checks should be refactored to a modifier or function	6

Total: 268 instances over 20 issues

[L‑01] require() should be used instead of assert()

Prior to solidity version 0.8.0, hitting an assert consumes the remainder of the transaction’s available gas rather than returning it, as require()/revert() do. assert() should be avoided even past solidity version 0.8.0 as its documentation states that “The assert function creates an error of type Panic(uint256). … Properly functioning code should never create a Panic, not even on invalid external input. If this happens, then there is a bug in your contract which you should fix”.

There are 2 instances of this issue. (For in-depth details on this and all further issues with multiple instances, please see the warden’s full report.)

[L‑02] Missing checks for address(0x0) when assigning values to address state variables

There is 1 instance of this issue:

File: contracts/dnssec-oracle/Owned.sol

19:           owner = newOwner;

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/dnssec-oracle/Owned.sol#L19

[L‑03] Open TODOs

Code architecture, incentives, and error handling/reporting questions/issues should be resolved before deployment

There is 1 instance of this issue:

File: contracts/dnssec-oracle/DNSSECImpl.sol

238:          // TODO: Check key isn't expired, unless updating key itself

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/dnssec-oracle/DNSSECImpl.sol#L238

[L-04] File is missing NatSpec

There are 10 instances of this issue.

[L-05] NatSpec is incomplete

There are 13 instances of this issue.

[N‑01] Name validation is not strictly valid

While the documentation does in fact say that there are other validations necessary to be compatible with the legacy DNS system, it would be better to have the following function signature instead function valid(string calldata name, bool isEnforceLegacyRules) public pure returns (bool), so it’s clear what the caller is validating

There is 1 instance of this issue:

File: contracts/ethregistrar/ETHRegistrarController.sol

77       function valid(string memory name) public pure returns (bool) {
78           return name.strlen() >= 3;
79:      }

https://github.com/code-423n4/2022-07-ens/blob/4dfb0e32f586bff3db486349523a93480e3ddfba/contracts/ethregistrar/ETHRegistrarController.sol#L77-L79

[N‑02] Adding a return statement when the function defines a named return variable, is redundant

There is 1 instance of this issue:

File: contracts/dnssec-oracle/DNSSECImpl.sol

139:          return rrset;

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/dnssec-oracle/DNSSECImpl.sol#L139

[N‑03] require()/revert() statements should have descriptive reason strings

There are 17 instances of this issue.

[N‑04] public functions not called by the contract should be declared external instead

Contracts are allowed to override their parents’ functions and change the visibility from external to public.

There are 13 instances of this issue.

[N‑05] constants should be defined rather than using magic numbers

Even assembly can benefit from using readable constants instead of hex/numeric literals.

There are 150 instances of this issue.

[N‑06] Redundant cast

The type of the variable is the same as the type to which the variable is being cast.

There is 1 instance of this issue:

File: contracts/registry/ReverseRegistrar.sol

/// @audit address(resolver)
53:               address(resolver) != address(0),

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/registry/ReverseRegistrar.sol#L53

[N‑07] Missing event and or timelock for critical parameter change

Events help non-contract tools to track changes, and events prevent users from being surprised by changes

There are 3 instances of this issue.

[N‑08] File is missing version pragma

There is 1 instance of this issue:

File: contracts/ethregistrar/IBaseRegistrar.sol

0:    import "../registry/ENS.sol";

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/ethregistrar/IBaseRegistrar.sol#L0

[N‑09] Use a more recent version of solidity

• Use a solidity version of at least 0.8.12 to get string.concat() to be used instead of abi.encodePacked(<str>,<str>)
  There are 4 instances of this issue.
• Use a solidity version of at least 0.8.13 to get the ability to use using for with a list of free functions
  There are 3 instances of this issue.

[N‑10] pragma experimental ABIEncoderV2 is deprecated

Use pragma abicoder v2 instead

There are 2 instances of this issue.

[N‑11] Constant redefined elsewhere

Consider defining in only one contract so that values cannot become out of sync when only one location is updated. A cheap way to store constants in a single location is to create an internal constant in a library. If the variable is a local cache of another contract’s value, consider making the cache variable internal or private, which will require external users to query the contract with the source of truth, so that callers don’t get out of sync.

There is 1 instance of this issue:

File: contracts/wrapper/NameWrapper.sol

/// @audit seen in contracts/registry/ReverseRegistrar.sol 
35:       ENS public immutable override ens;

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/wrapper/NameWrapper.sol#L35

[N‑12] Inconsistent spacing in comments

Some lines use // x and some use //x. The instances below point out the usages that don’t follow the majority, within each file

There are 2 instances of this issue.

[N‑13] Lines are too long

Usually lines in source code are limited to 80 characters. Today’s screens are much larger so it’s reasonable to stretch this in some cases. Since the files will most likely reside in GitHub, and GitHub starts using a scroll bar in all cases when the length is over 164 characters, the lines below should be split when they reach that length

There are 8 instances of this issue.

[N‑14] Inconsistent method of specifying a floating pragma

Some files use >=, some use ^. The instances below are examples of the method that has the fewest instances for a specific version. Note that using >= without also specifying <= will lead to failures to compile, or external project incompatability, when the major version changes and there are breaking-changes, so ^ should be preferred regardless of the instance counts

There are 10 instances of this issue.

[N‑15] Non-library/interface files should use fixed compiler versions, not floating ones

There are 4 instances of this issue.

[N‑16] Typos

There are 5 instances of this issue.

[N‑17] File does not contain an SPDX Identifier

There are 14 instances of this issue.

[N‑18] Event is missing indexed fields

Index event fields make the field more quickly accessible to off-chain tools that parse events. However, note that each index field costs extra gas during emission, so it’s not necessarily best to index the maximum allowed per event (threefields). Each event should use three indexed fields if there are three or more fields, and gas usage is not particularly of concern for the events in question.

There are 18 instances of this issue.

[N‑19] Not using the named return variables anywhere in the function is confusing

Consider changing the variable to be an unnamed one.

There are 4 instances of this issue.

[N‑20] Duplicated require()/revert() checks should be refactored to a modifier or function

The compiler will inline the function, which will avoid JUMP instructions usually associated with functions

There are 6 instances of this issue.

jefflau (ENS) commented:

High quality submission, documented well with links and code examples.

---

Gas Optimizations

For this contest, 70 reports were submitted by wardens detailing gas optimizations. The report highlighted below by 0xKitsune received the top score from the judge.

The following wardens also submitted reports: joestakey, IllIllI, gogo, Dravee, m_Rassska, MiloTruck, rbserver, hake, TomJ, 0x1f8b, ajtra, Bnke0x0, c3phas, Deivitto, kyteg, RedOneN, Sm4rty, Tomio, __141345__, brgltd, bulej93, Ch_301, cRat1st0s, durianSausage, JC, JohnSmith, _Adam, 0xNazgul, asutorufos, delfin454000, fatherOfBlocks, rokinot, Waze, 0xNineDec, 0x040, 0x29A, 0xsam, Aussie_Battlers, Aymen0909, Fitraldys, lucacez, Noah3o6, ReyAdmirado, robee, Rohan16, Rolezn, sach1r0, samruna, 8olidity, arcoun, benbaessler, CRYP70, karanctf, lcfr_eth, rajatbeladiya, sahar, sashik_eth, simon135, zuhaibmohd, cryptonue, ElKu, Funen, hyh, seyni, ak1, Chom, GimelSec, Lambda, and Ruhum.

Gas Optimizations Summary

The following sections detail the gas optimizations found throughout the codebase. Each optimization is documented with the setup, an explainer for the optimization, a gas report and line identifiers for each optimization across the codebase. For each section’s gas report, the optimizer was turned on and set to 10000 runs. You can replicate any tests/gas reports by heading to 0xKitsune/gas-lab and cloning the repo. Then, simply copy/paste the contract examples from any section and run forge test --gas-report. You can also easily update the optimizer runs in the foundry.toml.

---

[G-01] Use assembly to hash instead of Solidity

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
    }

    function testGas() public view {
        c0.solidityHash(2309349, 2304923409);
        c1.assemblyHash(2309349, 2304923409);
    }
}

contract Contract0 {
    function solidityHash(uint256 a, uint256 b) public view {
        //unoptimized
        keccak256(abi.encodePacked(a, b));
    }
}

contract Contract1 {
    function assemblyHash(uint256 a, uint256 b) public view {
        //optimized
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            let hashedVal := keccak256(0x00, 0x40)
        }
    }
}

Gas Report

╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract0 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 36687              ┆ 214             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ solidityHash       ┆ 313             ┆ 313 ┆ 313    ┆ 313 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract1 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 31281              ┆ 186             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ assemblyHash       ┆ 231             ┆ 231 ┆ 231    ┆ 231 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Lines

For full list of line references, see warden’s original submission.

[G-02] unchecked{++i} instead of i++ (or use assembly when applicable)

Use ++i instead of i++. This is especially useful in for loops but this optimization can be used anywhere in your code. You can also use unchecked{++i;} for even more gas savings but this will not check to see if i overflows. For extra safety if you are worried about this, you can add a require statement after the loop checking if i is equal to the final incremented value. For best gas savings, use inline assembly, however this limits the functionality you can achieve. For example you cant use Solidity syntax to internally call your own contract within an assembly block and external calls must be done with the call() or delegatecall() instruction. However when applicable, inline assembly will save much more gas.

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;
    Contract2 c2;
    Contract3 c3;
    Contract4 c4;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
        c2 = new Contract2();
        c3 = new Contract3();
        c4 = new Contract4();
    }

    function testGas() public {
        c0.iPlusPlus();
        c1.plusPlusI();
        c2.uncheckedPlusPlusI();
        c3.safeUncheckedPlusPlusI();
        c4.inlineAssemblyLoop();
    }
}

contract Contract0 {
    //loop with i++
    function iPlusPlus() public pure {
        uint256 j = 0;
        for (uint256 i; i < 10; i++) {
            j++;
        }
    }
}

contract Contract1 {
    //loop with ++i
    function plusPlusI() public pure {
        uint256 j = 0;
        for (uint256 i; i < 10; ++i) {
            j++;
        }
    }
}

contract Contract2 {
    //loop with unchecked{++i}
    function uncheckedPlusPlusI() public pure {
        uint256 j = 0;
        for (uint256 i; i < 10; ) {
            j++;

            unchecked {
                ++i;
            }
        }
    }
}

contract Contract3 {
    //loop with unchecked{++i} with additional overflow check
    function safeUncheckedPlusPlusI() public pure {
        uint256 j = 0;
        uint256 i = 0;
        for (i; i < 10; ) {
            j++;

            unchecked {
                ++i;
            }
        }

        //check for overflow
        assembly {
            if lt(i, 10) {
                mstore(0x00, "loop overflow")
                revert(0x00, 0x20)
            }
        }
    }
}

contract Contract4 {
    //loop with inline assembly
    function inlineAssemblyLoop() public pure {
        assembly {
            let j := 0

            for {
                let i := 0
            } lt(i, 10) {
                i := add(i, 0x01)
            } {
                j := add(j, 0x01)
            }
        }
    }
}

Gas Report

╭────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Contract0 contract ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 37687              ┆ 219             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ iPlusPlus          ┆ 2039            ┆ 2039 ┆ 2039   ┆ 2039 ┆ 1       │
╰────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Contract1 contract ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 37287              ┆ 217             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ plusPlusI          ┆ 1989            ┆ 1989 ┆ 1989   ┆ 1989 ┆ 1       │
╰────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭────────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Contract3 contract     ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost        ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 42693                  ┆ 244             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name          ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ safeUncheckedPlusPlusI ┆ 1355            ┆ 1355 ┆ 1355   ┆ 1355 ┆ 1       │
╰────────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Contract2 contract ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 35887              ┆ 210             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ uncheckedPlusPlusI ┆ 1329            ┆ 1329 ┆ 1329   ┆ 1329 ┆ 1       │
╰────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract4 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 26881              ┆ 164             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ inlineAssemblyLoop ┆ 709             ┆ 709 ┆ 709    ┆ 709 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Lines

• DNSSECImpl.sol:93
• ETHRegistrarController.sol:256
• BytesUtils.sol:266
• BytesUtils.sol:313
• ERC1155Fuse.sol:92
• ERC1155Fuse.sol:205
• StringUtils.sol:14

[G-03] Use assembly for math (add, sub, mul, div)

Use assembly for math instead of Solidity. You can check for overflow/underflow in assembly to ensure safety. If using Solidity versions < 0.8.0 and you are using Safemath, you can gain significant gas savings by using assembly to calculate values and checking for overflow/underflow.

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;
    Contract2 c2;
    Contract3 c3;
    Contract4 c4;
    Contract5 c5;
    Contract6 c6;
    Contract7 c7;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
        c2 = new Contract2();
        c3 = new Contract3();
        c4 = new Contract4();
        c5 = new Contract5();
        c6 = new Contract6();
        c7 = new Contract7();
    }

    function testGas() public {
        c0.addTest(34598345, 100);
        c1.addAssemblyTest(34598345, 100);
        c2.subTest(34598345, 100);
        c3.subAssemblyTest(34598345, 100);
        c4.mulTest(34598345, 100);
        c5.mulAssemblyTest(34598345, 100);
        c6.divTest(34598345, 100);
        c7.divAssemblyTest(34598345, 100);
    }
}

contract Contract0 {
    //addition in Solidity
    function addTest(uint256 a, uint256 b) public pure {
        uint256 c = a + b;
    }
}

contract Contract1 {
    //addition in assembly
    function addAssemblyTest(uint256 a, uint256 b) public pure {
        assembly {
            let c := add(a, b)

            if lt(c, a) {
                mstore(0x00, "overflow")
                revert(0x00, 0x20)
            }
        }
    }
}

contract Contract2 {
    //subtraction in Solidity
    function subTest(uint256 a, uint256 b) public pure {
        uint256 c = a - b;
    }
}

contract Contract3 {
    //subtraction in assembly
    function subAssemblyTest(uint256 a, uint256 b) public pure {
        assembly {
            let c := sub(a, b)

            if gt(c, a) {
                mstore(0x00, "underflow")
                revert(0x00, 0x20)
            }
        }
    }
}

contract Contract4 {
    //multiplication in Solidity
    function mulTest(uint256 a, uint256 b) public pure {
        uint256 c = a * b;
    }
}

contract Contract5 {
    //multiplication in assembly
    function mulAssemblyTest(uint256 a, uint256 b) public pure {
        assembly {
            let c := mul(a, b)

            if lt(c, a) {
                mstore(0x00, "overflow")
                revert(0x00, 0x20)
            }
        }
    }
}

contract Contract6 {
    //division in Solidity
    function divTest(uint256 a, uint256 b) public pure {
        uint256 c = a * b;
    }
}

contract Contract7 {
    //division in assembly
    function divAssemblyTest(uint256 a, uint256 b) public pure {
        assembly {
            let c := div(a, b)

            if gt(c, a) {
                mstore(0x00, "underflow")
                revert(0x00, 0x20)
            }
        }
    }
}

Gas Report

╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract0 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 40493              ┆ 233             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ addTest            ┆ 303             ┆ 303 ┆ 303    ┆ 303 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract1 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 37087              ┆ 216             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ addAssemblyTest    ┆ 263             ┆ 263 ┆ 263    ┆ 263 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract2 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 40293              ┆ 232             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ subTest            ┆ 300             ┆ 300 ┆ 300    ┆ 300 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract3 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 37287              ┆ 217             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ subAssemblyTest    ┆ 263             ┆ 263 ┆ 263    ┆ 263 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract4 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 41893              ┆ 240             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ mulTest            ┆ 325             ┆ 325 ┆ 325    ┆ 325 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract5 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 37087              ┆ 216             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ mulAssemblyTest    ┆ 265             ┆ 265 ┆ 265    ┆ 265 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract6 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 41893              ┆ 240             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ divTest            ┆ 325             ┆ 325 ┆ 325    ┆ 325 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract7 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 37287              ┆ 217             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ divAssemblyTest    ┆ 265             ┆ 265 ┆ 265    ┆ 265 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Lines

For full list of line references, see warden’s original submission.

[G-04] Use calldata instead of memory for function arguments that do not get mutated.

Mark data types as calldata instead of memory where possible. This makes it so that the data is not automatically loaded into memory. If the data passed into the function does not need to be changed (like updating values in an array), it can be passed in as calldata. The one exception to this is if the argument must later be passed into another function that takes an argument that specifies memory storage.

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;
    Contract2 c2;
    Contract3 c3;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
        c2 = new Contract2();
        c3 = new Contract3();
    }

    function testGas() public {
        uint256[] memory arr = new uint256[](10);
        c0.calldataArray(arr);
        c1.memoryArray(arr);

        bytes memory data = abi.encode("someText");
        c2.calldataBytes(data);
        c3.memoryBytes(data);
    }
}

contract Contract0 {
    function calldataArray(uint256[] calldata arr) public {
        uint256 j;
        for (uint256 i; i < arr.length; i++) {
            j = arr[i] + 10;
        }
    }
}

contract Contract1 {
    function memoryArray(uint256[] memory arr) public {
        uint256 j;
        for (uint256 i; i < arr.length; i++) {
            j = arr[i] + 10;
        }
    }
}

contract Contract2 {
    function calldataBytes(bytes calldata data) public {
        bytes32 val;
        for (uint256 i; i < 10; i++) {
            val = keccak256(abi.encode(data, i));
        }
    }
}

contract Contract3 {
    function memoryBytes(bytes memory data) public {
        bytes32 val;
        for (uint256 i; i < 10; i++) {
            val = keccak256(abi.encode(data, i));
        }
    }
}

Gas Report

╭───────────────────────────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ src/test/GasTest.t.sol:Contract0 contract ┆                 ┆      ┆        ┆      ┆         │
╞═══════════════════════════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost                           ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 97947                                     ┆ 521             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                             ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ calldataArray                             ┆ 2824            ┆ 2824 ┆ 2824   ┆ 2824 ┆ 1       │
╰───────────────────────────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭───────────────────────────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ src/test/GasTest.t.sol:Contract1 contract ┆                 ┆      ┆        ┆      ┆         │
╞═══════════════════════════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost                           ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 128171                                    ┆ 672             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                             ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ memoryArray                               ┆ 3755            ┆ 3755 ┆ 3755   ┆ 3755 ┆ 1       │
╰───────────────────────────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭───────────────────────────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ src/test/GasTest.t.sol:Contract2 contract ┆                 ┆      ┆        ┆      ┆         │
╞═══════════════════════════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost                           ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 100547                                    ┆ 534             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                             ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ calldataBytes                             ┆ 4934            ┆ 4934 ┆ 4934   ┆ 4934 ┆ 1       │
╰───────────────────────────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭───────────────────────────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ src/test/GasTest.t.sol:Contract3 contract ┆                 ┆      ┆        ┆      ┆         │
╞═══════════════════════════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost                           ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 135183                                    ┆ 707             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                             ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ memoryBytes                               ┆ 7551            ┆ 7551 ┆ 7551   ┆ 7551 ┆ 1       │
╰───────────────────────────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯

Lines

For full list of line references, see warden’s original submission.

[G-05] Use multiple require() statements instead of require(expression && expression && …)

You can save gas by breaking up a require statement with multiple conditions, into multiple require statements with a single condition.

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
    }

    function testGas() public {
        c0.singleRequire(3);
        c1.multipleRequire(3);
    }
}

contract Contract0 {
    function singleRequire(uint256 num) public {
        require(num > 1 && num < 10 && num == 3);
    }
}

contract Contract1 {
    function multipleRequire(uint256 num) public {
        require(num > 1);
        require(num < 10);
        require(num == 3);
    }
}

Gas Report

╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract0 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 35487              ┆ 208             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ singleRequire      ┆ 286             ┆ 286 ┆ 286    ┆ 286 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract1 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 35887              ┆ 210             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ multipleRequire    ┆ 270             ┆ 270 ┆ 270    ┆ 270 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Lines

• BytesUtils.sol:268
• ERC1155Fuse.sol:216
• ERC1155Fuse.sol:291

[G-06] Use assembly to write storage values

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
    }

    function testGas() public {
        c0.updateOwner(0x158B28A1b1CB1BE12C6bD8f5a646a0e3B2024734);
        c1.assemblyUpdateOwner(0x158B28A1b1CB1BE12C6bD8f5a646a0e3B2024734);
    }
}

contract Contract0 {
    address owner = 0xb4c79daB8f259C7Aee6E5b2Aa729821864227e84;

    function updateOwner(address newOwner) public {
        owner = newOwner;
    }
}

contract Contract1 {
    address owner = 0xb4c79daB8f259C7Aee6E5b2Aa729821864227e84;

    function assemblyUpdateOwner(address newOwner) public {
        assembly {
            sstore(owner.slot, newOwner)
        }
    }
}

Gas Report

╭────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Contract0 contract ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 60623              ┆ 261             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ updateOwner        ┆ 5302            ┆ 5302 ┆ 5302   ┆ 5302 ┆ 1       │
╰────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Contract1 contract ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 54823              ┆ 232             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ assemblyUpdateOwner┆ 5236            ┆ 5236 ┆ 5236   ┆ 5236 ┆ 1       │
╰────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯

Lines

• Owned.sol:15
• Owned.sol:19
• ETHRegistrarController.sol:61
• ETHRegistrarController.sol:62

[G-07] Use assembly to check for address(0)

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
    }

    function testGas() public view {
        c0.ownerNotZero(address(this));
        c1.assemblyOwnerNotZero(address(this));
    }
}

contract Contract0 {
    function ownerNotZero(address _addr) public pure {
        require(_addr != address(0), "zero address)");
    }
}

contract Contract1 {
    function assemblyOwnerNotZero(address _addr) public pure {
        assembly {
            if iszero(_addr) {
                mstore(0x00, "zero address")
                revert(0x00, 0x20)
            }
        }
    }
}

Gas Report

╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract0 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 61311              ┆ 338             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ ownerNotZero       ┆ 258             ┆ 258 ┆ 258    ┆ 258 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭──────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract1 contract   ┆                 ┆     ┆        ┆     ┆         │
╞══════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 44893                ┆ 255             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ assemblyOwnerNotZero ┆ 252             ┆ 252 ┆ 252    ┆ 252 ┆ 1       │
╰──────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Lines

• ReverseRegistrar.sol:53
• DNSSECImpl.sol:336
• ETHRegistrarController.sol:100
• NameWrapper.sol:132
• NameWrapper.sol:139
• NameWrapper.sol:318
• NameWrapper.sol:661
• NameWrapper.sol:763
• NameWrapper.sol:799
• NameWrapper.sol:911
• ERC1155Fuse.sol:61
• ERC1155Fuse.sol:176
• ERC1155Fuse.sol:199
• ERC1155Fuse.sol:248
• ERC1155Fuse.sol:249

[G-08] Use assembly when getting a contract’s balance of ETH.

You can use selfbalance() instead of address(this).balance when getting your contract’s balance of ETH to save gas. Additionally, you can use balance(address) instead of address.balance() when getting an external contract’s balance of ETH.

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;
    Contract2 c2;
    Contract3 c3;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
        c2 = new Contract2();
        c3 = new Contract3();
    }

    function testGas() public {
        c0.addressInternalBalance();
        c1.assemblyInternalBalance();
        c2.addressExternalBalance(address(this));
        c3.assemblyExternalBalance(address(this));
    }
}

contract Contract0 {
    function addressInternalBalance() public returns (uint256) {
        return address(this).balance;
    }
}

contract Contract1 {
    function assemblyInternalBalance() public returns (uint256) {
        assembly {
            let c := selfbalance()
            mstore(0x00, c)
            return(0x00, 0x20)
        }
    }
}

contract Contract2 {
    function addressExternalBalance(address addr) public {
        uint256 bal = address(addr).balance;
        bal++;
    }
}

contract Contract3 {
    function assemblyExternalBalance(address addr) public {
        uint256 bal;
        assembly {
            bal := balance(addr)
        }
        bal++;
    }
}

Gas Report

╭────────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract0 contract     ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost        ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 23675                  ┆ 147             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name          ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ addressInternalBalance ┆ 148             ┆ 148 ┆ 148    ┆ 148 ┆ 1       │
╰────────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭─────────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract1 contract      ┆                 ┆     ┆        ┆     ┆         │
╞═════════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost         ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 27081                   ┆ 165             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name           ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ assemblyInternalBalance ┆ 133             ┆ 133 ┆ 133    ┆ 133 ┆ 1       │
╰─────────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract2 contract     ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost        ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 61511                  ┆ 339             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name          ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ addressExternalBalance ┆ 417             ┆ 417 ┆ 417    ┆ 417 ┆ 1       │
╰────────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭─────────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract3 contract      ┆                 ┆     ┆        ┆     ┆         │
╞═════════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost         ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 57105                   ┆ 317             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name           ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ assemblyExternalBalance ┆ 411             ┆ 411 ┆ 411    ┆ 411 ┆ 1       │
╰─────────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Lines

• ETHRegistrarController.sol:211

[G-09] Cache array length during for loop definition.

A typical for loop definition may look like: for (uint256 i; i < arr.length; i++){}. Instead of using array.length, cache the array length before the loop, and use the cached value to safe gas. This will avoid an MLOAD every loop for arrays stored in memory and an SLOAD for arrays stored in storage. This can have significant gas savings for arrays with a large length, especially if the array is stored in storage.

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;
    Contract2 c2;
    Contract3 c3;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
        c2 = new Contract2();
        c3 = new Contract3();
    }

    function testGas() public view {
        uint256[] memory arr = new uint256[](10);
        c0.nonCachedMemoryListLength(arr);
        c1.cachedMemoryListLength(arr);
        c2.nonCachedStorageListLength();
        c3.cachedStorageListLength();
    }
}

contract Contract0 {
    function nonCachedMemoryListLength(uint256[] memory arr) public pure {
        uint256 j;
        for (uint256 i; i < arr.length; i++) {
            j = arr[i] + 10;
        }
    }
}

contract Contract1 {
    function cachedMemoryListLength(uint256[] memory arr) public pure {
        uint256 j;

        uint256 length = arr.length;
        for (uint256 i; i < length; i++) {
            j = arr[i] + 10;
        }
    }
}

contract Contract2 {
    uint256[] arr = new uint256[](10);

    function nonCachedStorageListLength() public view {
        uint256 j;
        for (uint256 i; i < arr.length; i++) {
            j = arr[i] + 10;
        }
    }
}

contract Contract3 {
    uint256[] arr = new uint256[](10);

    function cachedStorageListLength() public view {
        uint256 j;
        uint256 length = arr.length;

        for (uint256 i; i < length; i++) {
            j = arr[i] + 10;
        }
    }
}

Gas Report

╭───────────────────────────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ src/test/GasTest.t.sol:Contract0 contract ┆                 ┆      ┆        ┆      ┆         │
╞═══════════════════════════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost                           ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 128171                                    ┆ 672             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                             ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ nonCachedMemoryListLength                 ┆ 3755            ┆ 3755 ┆ 3755   ┆ 3755 ┆ 1       │
╰───────────────────────────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭───────────────────────────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ src/test/GasTest.t.sol:Contract1 contract ┆                 ┆      ┆        ┆      ┆         │
╞═══════════════════════════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost                           ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 128777                                    ┆ 675             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                             ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ cachedMemoryListLength                    ┆ 3733            ┆ 3733 ┆ 3733   ┆ 3733 ┆ 1       │
╰───────────────────────────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭───────────────────────────────────────────┬─────────────────┬───────┬────────┬───────┬─────────╮
│ src/test/GasTest.t.sol:Contract2 contract ┆                 ┆       ┆        ┆       ┆         │
╞═══════════════════════════════════════════╪═════════════════╪═══════╪════════╪═══════╪═════════╡
│ Deployment Cost                           ┆ Deployment Size ┆       ┆        ┆       ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 118474                                    ┆ 539             ┆       ┆        ┆       ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                             ┆ min             ┆ avg   ┆ median ┆ max   ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ nonCachedStorageListLength                ┆ 27979           ┆ 27979 ┆ 27979  ┆ 27979 ┆ 1       │
╰───────────────────────────────────────────┴─────────────────┴───────┴────────┴───────┴─────────╯
╭───────────────────────────────────────────┬─────────────────┬───────┬────────┬───────┬─────────╮
│ src/test/GasTest.t.sol:Contract3 contract ┆                 ┆       ┆        ┆       ┆         │
╞═══════════════════════════════════════════╪═════════════════╪═══════╪════════╪═══════╪═════════╡
│ Deployment Cost                           ┆ Deployment Size ┆       ┆        ┆       ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 118674                                    ┆ 540             ┆       ┆        ┆       ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                             ┆ min             ┆ avg   ┆ median ┆ max   ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ cachedStorageListLength                   ┆ 26984           ┆ 26984 ┆ 26984  ┆ 26984 ┆ 1       │
╰───────────────────────────────────────────┴─────────────────┴───────┴────────┴───────┴─────────╯

Lines

• DNSSECImpl.sol:93
• ETHRegistrarController.sol:256
• ERC1155Fuse.sol:92
• ERC1155Fuse.sol:205
• RRUtils.sol:310

[G-10] Consider marking functions as payable

You can mark public or external functions as payable to save gas. Functions that are not payable have additional logic to check if there was a value sent with a call, however, making a function payable eliminates this check. This optimization should be carefully considered due to potentially unwanted behavior when a function does not need to accept ether.

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
    }

    function testGas() public {
        c0.isNotPayable();
        c1.isPayable();
    }
}

contract Contract0 {
    function isNotPayable() public view {
        uint256 val = 0;
        val++;
    }
}

contract Contract1 {
    function isPayable() public payable {
        uint256 val = 0;
        val++;
    }
}

Gas Report

╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract0 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 32081              ┆ 190             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ isNotPayable       ┆ 198             ┆ 198 ┆ 198    ┆ 198 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract1 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 29681              ┆ 178             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ isPayable          ┆ 174             ┆ 174 ┆ 174    ┆ 174 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Lines

For full list of line references, see warden’s original submission.

[G-11] Use custom errors instead of string error messages

contract GasTest is DSTest {
    Contract0 c0;
    Contract1 c1;

    function setUp() public {
        c0 = new Contract0();
        c1 = new Contract1();
    }

    function testFailGas() public {
        c0.stringErrorMessage();
        c1.customErrorMessage();
    }
}

contract Contract0 {
    function stringErrorMessage() public {
        bool check = false;
        require(check, "error message");
    }
}

contract Contract1 {
    error CustomError();

    function customErrorMessage() public {
        bool check = false;
        if (!check) {
            revert CustomError();
        }
    }
}

Gas Report

╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract0 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 34087              ┆ 200             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ stringErrorMessage ┆ 218             ┆ 218 ┆ 218    ┆ 218 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Contract1 contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 26881              ┆ 164             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ customErrorMessage ┆ 161             ┆ 161 ┆ 161    ┆ 161 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Lines

For full list of line references, see warden’s original submission.

jefflau (ENS) commented:

High quality submission with gas tables and reproduction.

---

Disclosures

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C4 does not provide any guarantee or warranty regarding the security of this project. All smart contract software should be used at the sole risk and responsibility of users.