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CCIPSender

This project is a proof-of-concept to demonstration interactions with the CCIP bridge.

It's not designed to be production code, it's not security-audited, use at your own risk.

Overview

A sender contract serves as an entrypoint between your end user and the router contract from Chainlink. This contract is under your control and can be used to offer more possibility of customization.

Notably, this sender contract allows to:

  • Compute and pay the fees for the end-user by pre-funding the contract
  • Offers gasless transfer for end-user through the standard ERC-2771 (meta transactions)
  • Configure which blockchains and fee tokens are available.
  • Configure which users is authorized to use the contract

The sender contract will be the main entrypoint for your user to bridge tokens. It will contain all the logic to transfer tokens and send messages.

More information is available in the CCIP Chainlink website and in the library CCIP in github smartcontractkit/ccip

The main reference is the CCIP masterclass

Configuration and usage

To allow bidirectional transactions, you must deploy the sender contract on each blockchain.

Let's look at the example of a bridge between Polygon and Avalanche.

After deployment of the contracts, the first step is to establish the link between Polygon and Avalanche.

Allow list chains

We will allow Avalanche to be a destination chain. We call the function setAllowlistChain() to do this.

function setAllowlistChain(uint64 _chainSelector, bool allowedSourceChain, bool allowedDestinationChain)

Example:

setAllowlistChain(6433500567565415381, false, true)

And Polygon too

setAllowlistChain(4051577828743386545, false, true)

The configuration of the source chain is only useful if we use a receiver contract, but this is not the case for the moment.

Activate fee tokens

We will now set the fee payment for our two senders contracts.

For Polygon, we will authorize to pay the fees in MATIC, the Polygon PoS native token

For Avalanche, we will authorize to pay the fees in AVAX, the Avalanche native token.

The selected id for native token is zero, the function has to be called in the two blockchains

changeStatusFeePaymentMethod(0, true);

For non-native token, we use another function setFeePaymentMethod:

function setFeePaymentMethod(IERC20 tokenAddress_, string calldata  label_)

Authorize user to use the contracts

Our function transferTokens from our sender contract is protected by an access control. Only authorized users can transfer tokens. You have to grant the corresponding role to your brider's users.

grantRole(bytes32 role, address account)

Example:

grantRole(`b0f04d2e44f4b417ab78712b52802767b073e39f75dba9f6e3a31125b053f026`, <Sender address>)

Fund the sender contract

It is important to fund our sender contract to pay the fees.

For that, we will call the function depositNativeTokens() with our account holding native tokens.

Approve the sender contract

With our bridge user, we authorize the bridge to transfer our tokens in our name.

This is done with the classic ERC-20 approve function.

Module

We divided the code into several components called modules. Each module is responsible to perform specific task.

Group Contract name Description
CCIPSender Our main contract to deploy
CCIPBaseSender Our base contract providing the public transfer functions
Security
AuthorizationModule Manage the access control
Wrappers
CCIPSenderBuild Build a CCIP message
CCIPContractBalance Withdraw native and fee tokens from the contracts
Configuration
CCIPAllowlistedChain Set and define the blockchain supported by the sender contract.
CCIPRouterManage Store the router contracts address and associated functions
CCIPSenderPayment Compute fee required to transmit the transfer message

Documentation

Here a summary of the main documentation

Document Link/Files
Technical documentation doc/technical
Toolchain doc/TOOLCHAIN.md
Surya report doc/schem/surya

Deployment

The main contract is CCIPSender. This contract has to be deployed on each source chain where you want perform transfers.

UML

Usage

Explain how it works.

Toolchain installation

The contracts are developed and tested with Foundry, a smart contract development toolchain.

To install the Foundry suite, please refer to the official instructions in the Foundry book.

Initialization

You must first initialize the submodules, with

forge install

See also the command's documentation.

Later you can update all the submodules with:

forge update

See also the command's documentation.

Compilation

The official documentation is available in the Foundry website

 forge build --contracts src/deplyoment/CCIPSender.sol

Testing

You can run the tests with

forge test

To run a specific test, use

forge test --match-contract <contract name> --match-test <function name>

See also the test framework's official documentation, and that of the test commands.

Coverage

  • Perform a code coverage
forge coverage
  • Generate LCOV report
forge coverage --report lcov
  • Generate index.html
forge coverage --report lcov && genhtml lcov.info --branch-coverage --output-dir coverage

See Solidity Coverage in VS Code with Foundry & Foundry forge coverage

Intellectual property

The original code is copyright (c) Taurus 2024, and is released under MIT license.