A Warrant Canary Smart Contract with Enclosed Funds

This project is a warrant canary contract, which allows users of the contract to passively inform a broad audience that a certain event has happened by not updating the a timestamp in the contract. Additionally, a user can enclose funds in the contract which can be moved by a predefined third party to their own wallet after expiration of the warrant canary. In this configuration the contract acts like a dead man's switch. It is written in solidity, so it runs on Ethereum or any EVM compatible chain.

A user can do several different interactions:

• Create a warrant canary. To do this he needs to:
  1. Define a time after which the warrant canary expires if the expiration time is not updated.
  2. Add a short description of the purpose of the warrant canary.
  3. Add a trusted third party if necessary. (wallet address).
• Update the timestamp to prove that a certain event did not happen yet.
• Move funds to the warrant canary.
• Update the time after which the warrant canary expires.
• Update the wallet address of the trusted third party.
• Remove funds from the warrant canary.
• Delete the warrant canary.

A trusted third party can:

• Withdraw funds if the warrant canary has expired.
• Delete the warrant canary if it has expired.

The general audience can:

• Check if the warrant canary has expired and therefore know, that a certain event has happened
• Add funds to any warrant canary.

The owner of the contract can:

• Pause the contract so no new warrant canaries can be created and no funds can be added to existing ones. Withdrawing and updating expiration is still possible.
• Withdraw excess funds, meaning funds that are not associated with a warrant canary. (This functionality is tested in the smart contract tests)
• Withdraw ERC-20 tokens which have been sent to the address accidentally. -> not implemented.

Website

The scroll testnet website can be reached by: https://warrantcanary-testnet.haurog.xyz/ or https://warrantcanary-testnet.netlify.app/

The scroll mainnet website can be reached by: https://warrantcanary-scroll-mainnet.haurog.xyz/ or https://warrantcanary-scroll.netlify.app/

20211127.warrant.canary.screencast.mp4

Design Patterns Decisions

Avoiding Attack Vectors and Bugs

Deployed Address

Directory Structure

• .github/workflows: Defining github actions to run tests automatically
• client: Frontend for the Warrant Canary contract. Plain HTML, CSS and javascript.
• contracts: Deployed smart contracts.
• migrations: Migration configuration files for deploying the smart contracts.
• test: Files for testing the smart contracts with truffle.

Run Tests Locally

This repository has been migrated from truffle to hardhat on the October 27th 2023. This means that the directory structure, tests and deployment are in a bit of a mixed state of truffle and hardhat style.

• Install NodeJS
• Install hardhat
• Run npm install in project root to install dependencies.
• Run npx hardhat test

Deployment

This repository uses frame.sh to connect to a hardware wallet to do the deployment. The chain to deploy needs to be also selected in the header of the deploy script: scripts/deploy.js

To scroll sepolia testnet:

npx hardhat run --network scrollSepolia scripts/deploy.js --verbose

To scroll mainnet:

npx hardhat run --network scrollMainnet scripts/deploy.js --verbose

Verify: Verification is done by hand. First flatten the contract by running

npx hardhat flatten > Flattened.sol

Then go to the scroll explorer and the contract address and verify manually: Example scroll Sepolia testnet: https://sepolia.scrollscan.com/address/0xdefd37cfe93f8b50ec4332bdacdaf4eadfc78be3 Example Scroll Mainnet: https://scrollscan.com/address/0xdefd37cfe93f8b50ec4332bdacdaf4eadfc78be3

Possible Improvements and Known Issues

• In general event handling does not seem to be too reliable, sometimes it is missing updates.
• Switching the account in Metamask is not handled on the website. Needs to be reloaded manually.
• If ERC-20 tokens are accidentally sent to the contract they cannot be retrieved.
• To make this contract and frontend more useable, a badge like element, like netlify badge at the top of this readme, will need to be developed such that anyone can add such a badge to their website to publicly show the status of their warrant canary.