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Security Audit
October 18th, 2023
Version 1.0.0
Presented by 0xMacro
This document includes the results of the security audit for Connext's smart contract code as found in the section titled ‘Source Code’. The security audit was performed by the Macro security team from October 9, 2023 to October 13, 2023.
The purpose of this audit is to review the source code of certain Connext Solidity contracts, and provide feedback on the design, architecture, and quality of the source code with an emphasis on validating the correctness and security of the software in its entirety.
Disclaimer: While Macro’s review is comprehensive and has surfaced some changes that should be made to the source code, this audit should not solely be relied upon for security, as no single audit is guaranteed to catch all possible bugs.
The following is an aggregation of issues found by the Macro Audit team:
| Severity | Count | Acknowledged | Won't Do | Addressed |
|---|---|---|---|---|
| Low | 1 | - | - | 1 |
| Code Quality | 4 | - | - | 4 |
| Informational | 1 | - | - | - |
Connext was quick to respond to these issues.
Our understanding of the specification was based on the following sources:
The following source code was reviewed during the audit:
2c28f1939b9a2f05ef915f9e8b07a005476aab5a
Specifically, we audited the following contracts within this repository, in the `packages/deployments/contracts/contracts/messaging/` directory:
| Source Code | SHA256 |
|---|---|
| RootManager.sol |
|
| connectors/SpokeConnector.sol |
|
| connectors/arbitrum/ArbitrumSpokeConnector.sol |
|
| connectors/consensys/ConsensysSpokeConnector.sol |
|
| connectors/gnosis/GnosisSpokeConnector.sol |
|
| connectors/mainnet/MainnetSpokeConnector.sol |
|
| connectors/multichain/MultichainSpokeConnector.sol |
|
| connectors/optimism/OptimismSpokeConnector.sol |
|
| connectors/polygon/PolygonSpokeConnector.sol |
|
| connectors/polygonzk/PolygonZkSpokeConnector.sol |
|
| connectors/wormhole/WormholeSpokeConnector.sol |
|
| connectors/zksync/ZkSyncSpokeConnector.sol |
|
| interfaces/IHubSpokeConnector.sol |
|
Click on an issue to jump to it, or scroll down to see them all.
We quantify issues in three parts:
This third part – the severity level – is a summary of how much consideration the client should give to fixing the issue. We assign severity according to the table of guidelines below:
| Severity | Description |
|---|---|
|
(C-x) Critical |
We recommend the client must fix the issue, no matter what, because not fixing would mean significant funds/assets WILL be lost. |
|
(H-x) High |
We recommend the client must address the issue, no matter what, because not fixing would be very bad, or some funds/assets will be lost, or the code’s behavior is against the provided spec. |
|
(M-x) Medium |
We recommend the client to seriously consider fixing the issue, as the implications of not fixing the issue are severe enough to impact the project significantly, albiet not in an existential manner. |
|
(L-x) Low |
The risk is small, unlikely, or may not relevant to the project in a meaningful way. Whether or not the project wants to develop a fix is up to the goals and needs of the project. |
|
(Q-x) Code Quality |
The issue identified does not pose any obvious risk, but fixing could improve overall code quality, on-chain composability, developer ergonomics, or even certain aspects of protocol design. |
|
(I-x) Informational |
Warnings and things to keep in mind when operating the protocol. No immediate action required. |
|
(G-x) Gas Optimizations |
The presented optimization suggestion would save an amount of gas significant enough, in our opinion, to be worth the development cost of implementing it. |
disputeBlocks
In SpokeConnector’s constructor, disputedBlocks can be set to a value smaller than minDisputedBlocks, as there is no explicit check preventing this.
An appropriate check is done in the RootManager’s constructor, but omitted in the SpokeConnector’s constructor.
Remediations to Consider
Consider adding a check that reverts when disputedBlocks is smaller than minDisputedBlocks.
external instead of public
The following functions can be set to external instead of public as they are not being called within the contract:
In RootManager.sol:
setMinDisputeBlockssetDisputeBlockssetDelayBlocksremoveConnectordiscardRootIn SpokeConnector.sol:
addSenderremoveSenderaddProposerremoveProposersetMinDisputeBlockssetDisputeBlockssetDelayBlockssetRateLimitBlocksremovePendingAggregateRootThe following events and errors are declared but not used anywhere in the code.
In RootManager.sol:
event RootPropagatederror RootManager_slowPropagate__OldAggregateRoot()In SpokeConnector.sol:
error SpokeConnector_send__OptimisticModeOn()Consider removing those declarations from the code.
In RootManager.sol, finalize(), and dequeue() functions emit two different events with some shared arguments for the same logic execution. This could be optimized by unifying these two events from each function into one.
In RootManager.sol the function dequeue() has the following comment
/**
* ...
* @dev Reverts if no verified inbound roots are found.
* ...
*/
However, the function does not revert and returns the current root and count for that case.
By enabling the optimistic mode, the propagation of messages to domains will completely bypass the native AMBs of each domain. A unique off-chain agent will be responsible for proposing aggregate roots and propagating them to every domain, concentrating the on-chain aggregation into one centric point.
Watchers will still execute their duties as protection against fraudulent messages but, at the moment, all the execution and safeguard controls will be centralized in Connext’s off-chain components.
Macro makes no warranties, either express, implied, statutory, or otherwise, with respect to the services or deliverables provided in this report, and Macro specifically disclaims all implied warranties of merchantability, fitness for a particular purpose, noninfringement and those arising from a course of dealing, usage or trade with respect thereto, and all such warranties are hereby excluded to the fullest extent permitted by law.
Macro will not be liable for any lost profits, business, contracts, revenue, goodwill, production, anticipated savings, loss of data, or costs of procurement of substitute goods or services or for any claim or demand by any other party. In no event will Macro be liable for consequential, incidental, special, indirect, or exemplary damages arising out of this agreement or any work statement, however caused and (to the fullest extent permitted by law) under any theory of liability (including negligence), even if Macro has been advised of the possibility of such damages.
The scope of this report and review is limited to a review of only the code presented by the Connext team and only the source code Macro notes as being within the scope of Macro’s review within this report. This report does not include an audit of the deployment scripts used to deploy the Solidity contracts in the repository corresponding to this audit. Specifically, for the avoidance of doubt, this report does not constitute investment advice, is not intended to be relied upon as investment advice, is not an endorsement of this project or team, and it is not a guarantee as to the absolute security of the project. In this report you may through hypertext or other computer links, gain access to websites operated by persons other than Macro. Such hyperlinks are provided for your reference and convenience only, and are the exclusive responsibility of such websites’ owners. You agree that Macro is not responsible for the content or operation of such websites, and that Macro shall have no liability to your or any other person or entity for the use of third party websites. Macro assumes no responsibility for the use of third party software and shall have no liability whatsoever to any person or entity for the accuracy or completeness of any outcome generated by such software.