receive.md

description
Receive an inbound message from any Hyperlane supported network

Receive

{% hint style="warning" %} Developers must implement the IMessageRecipient interface in order to be able to receive interchain messages. {% endhint %}

Interface

// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.6.11;

interface IMessageRecipient {
    /**
     * @notice Handle an interchain message
     * @param _origin Domain ID of the chain from which the message came
     * @param _sender Address of the message sender on the origin chain as bytes32
     * @param _body Raw bytes content of message body
     */
    function handle(
        uint32 _origin,
        bytes32 _sender,
        bytes calldata _body
    ) external;
}

Security

Access control

{% hint style="danger" %} To ensure only valid interchain messages are accepted, it is important to require that msg.sender is a known Hyperlane messaging.md. {% endhint %}

Developers must implement access control on handle() in order to ensure the security of interchain messages. Only a Hyperlane messaging.md contract should have permission to call this function. An example of this access control is shown below.

address constant mailbox = 0x0E3239277501d215e17a4d31c487F86a425E110B;
// for access control on handle implementations
modifier onlyMailbox() {
    require(msg.sender == mailbox);
    _;    
}

function handle(
    uint32 _origin,
    bytes32 _sender,
    bytes calldata _body
) external onlyMailbox {};

Interchain security modules

Developers can override Hyperlane's default multisig-ism.md-based security model by specifying their own sovereign-consensus.

See the sovereign-consensus documentation for more info on how to set the ISM used by your application.

Encoding

{% hint style="info" %} Hyperlane message senders are left-padded to bytes32 for compatibility with virtual machines that are addressed differently. {% endhint %}

The following utility is provided in the TypeCasts library for convenience.

// alignment preserving cast
function bytes32ToAddress(bytes32 _buf) internal pure returns (address) {
    return address(uint160(uint256(_buf)));
}

Example usage

An example handle() implementation for receiving messages is provided below.

event Received(uint32 origin, address sender, bytes body);
function handle(
    uint32 _origin,
    bytes32 _sender,
    bytes memory _body
) external onlyMailbox() {
    address sender = bytes32ToAddress(_sender);
    emit Received(_origin, sender, _body);
}