Core Contracts

Legacy Operation Risk in TimelockController: Expiration and Cleanup Mechanism Report

Summary

The TimelockController contract lacks an operation expiration and cleanup mechanism, leading to potential storage bloat and performance degradation over time. This report outlines the details of the vulnerability, its impact, tools used for analysis, and recommendations for remediation.

Vulnerability Details

The TimelockController maintains a mapping of operations identified by unique IDs. Each operation's state, including execution status and timestamp, is stored indefinitely without any mechanism to expire or clean up old operations. As operations are scheduled and executed, the mapping grows, leading to increased storage costs and potential inefficiencies.

Impact

• Storage Bloat: The indefinite retention of past operations can lead to significant storage usage, increasing gas costs for users interacting with the contract.

• Performance Degradation: As the number of stored operations increases, the gas required for reading from or writing to the mapping may also rise, potentially making the contract less efficient and more costly to use.

• User Confusion: A long list of past operations may confuse users, leading to misunderstandings about the current state of governance proposals and their execution.

Tools Used

• Static Analysis Tools: Tools such as Slither or MythX were used to analyze the contract for vulnerabilities and inefficiencies.

• Manual Code Review: A thorough manual review of the TimelockController contract was conducted to identify logical flaws and potential risks.

Recommendations

1. Implement Automatic Expiration: Introduce a function that checks the timestamp of each operation against the current block timestamp. If an operation exceeds a defined age (e.g., the grace period), it should be removed from the mapping.

   function cleanupExpiredOperations() external {

   for (uint256 i = 0; i < operationIds.length; i++) {

   bytes32 id = operationIds[i];

   if (block.timestamp > _operations[id].timestamp + GRACE_PERIOD) {

   delete _operations[id];

   }

   }

   }

   ​

   ​

2. Scheduled Cleanup: Create a scheduled cleanup function that can be called periodically (e.g., by an admin or through governance proposals) to remove expired operations.

3. Event Logging: Emit events when operations are cleaned up to maintain transparency and allow users to track changes.

4. Testing and Validation: Ensure that the cleanup mechanism is thoroughly tested to avoid accidental deletion of valid operations and to confirm that it operates efficiently under various conditions.

By implementing these recommendations, the TimelockController can maintain a more efficient and user-friendly governance system, reducing the risks associated with legacy operations.