Pause

Ability to Pause Project

This section described the implementation risks associated with being able to pause a project. Operational risks related to pausing are covered in the Ability to Pause Operational Risk section.

All Data Plane functions should be pausable. For example, a bridge contract could have a function that could transfer coins based on actions on another blockchain. The ability to pause a function in a project allows administrators to stop functions from successfully executing. If there is a vulnerability that is being actively exploited in a project, having the ability to pause a function could stop the exploitation of the project midway through the attack.

For Ethereum based projects, the OpenZeppelin project has an example contract Pausable.sol that can be used to implement pausing. Using this template, pausing a function becomes as simple as adding a modifier whenNotPaused. The code below shows how this would work in practice.

contract Example is Pausable {
    function pause() external onlyOwner {
        _pause();
    }
    function transfer(
        address _sender,
        address _tokenContract,
        address _recipient,
        uint256 _amount
    ) external whenNotPaused {
        // Only executed when not paused

When analyzing whether a project can be paused, it is important to check whether all data processing functions can be paused, or just some parts of the project.

Example

For example, in August 2022 the Nomad Bridge had an issue (see Rekt for an analysis of the issue from people outside the team). An attacker was able to determine a methodology for stealing funds using the Replica contract's process() function. Depite most of the Data Plane processing functions in the project being pausable, the process() function was not. This meant that the attack was able to proceed without the administrators of the project being able to stop it.

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Last update: October 13, 2023
Created: October 13, 2023