Receive

Receive an inbound message from any Hyperlane supported network

Developers must implement the IMessageRecipient interface in order to be able to receive interchain messages.

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

To ensure only valid interchain messages are accepted, it is important to require that msg.sender is a known Hyperlane Mailbox.

Developers must implement access control on handle() in order to ensure the security of interchain messages. Only a Hyperlane Mailbox 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-based security model by specifying their own Interchain security modules.

See the Interchain security modules documentation for more info on how to set the ISM used by your application.

Encoding

Hyperlane message senders are left-padded to bytes32 for compatibility with virtual machines that are addressed differently.

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);
}