COW Order Signer Security Audit

Audit Report Revisions

Audit Overview

We were tasked with performing an audit of the Gnosis Guild codebase and in particular their COW Order Signer module.

Over the course of the audit, we identified a potential cross-chain replay attack which is located in a dependency of the system and should be inapplicable; we invite the Gnosis Guild team to review it regardless.

As an additional point, we urge the Gnosis Guild team to clarify why the validTo and feeAmount sanitizations have been set in place given that they are already present as "immutable" arguments of the CowswapOrderSigner::signOrder function call.

We advise the Gnosis Guild team to closely evaluate all minor-and-above findings identified in the report and promptly remediate them as well as consider all optimizational exhibits identified in the report.

Post-Audit Conclusion

The Gnosis Guild team iterated through all findings within the report and provided us with a revised commit hash to evaluate all exhibits on.

All CowSwap related exhibits have been safely acknowledged by the Gnosis Guild team to avoid mutating the original code as ported over from the CowSwap codebase.

We evaluated all alleviations performed by Gnosis Guild and have identified that a single style-related exhibit has not been adequately dealt with. We advise the Gnosis Guild team to revisit the following exhibit: COS-01S

Post-Audit Conclusion (50bc415e93)

The Gnosis Guild team proceeded with remediating COS-01S per our recommendation, thus ensuring all exhibits related to the Gnosis Guild contracts have been dealt with.

As such, we consider all exhibits and relevant outputs of the audit report properly consumed by the Gnosis Guild team.

Audit Synopsis

Severity	Identified	Alleviated	Partially Alleviated	Acknowledged
	1	0	0	1
	6	3	0	3
	2	2	0	0
	0	0	0	0
	0	0	0	0

During the audit, we filtered and validated a total of 3 findings utilizing static analysis tools as well as identified a total of 6 findings during the manual review of the codebase. We strongly recommend that any minor severity or higher findings are dealt with promptly prior to the project's launch as they can introduce potential misbehaviours of the system as well as exploits.

Total Alleviations

The list below covers each segment of the audit in depth and links to the respective chapter of the report:

• 🎯 Scope
• 💻 Compilation
• 🔍 Static Analysis
• 👁️ Manual Review
• 🖋️ Code Style