EssentialForwarder

Solidity API

EssentialForwarder

EIP-2771 based MetaTransaction Forwarding Contract with EIP-3668 OffchainLookup for cross-chain token gating

Allows a Relayer to submit meta-transactions that utilize an NFT (i.e. in a game) on behalf of EOAs. Transactions are only executed if the Relayer provides a signature from a trusted signer. The signature must include the current owner of the Layer 1 NFT being used, or a Burner EOA the owner has authorized to use its NFTs.

EssentialForwarder can be used to build Layer 2 games that use Layer 1 NFTs without bridging and with superior UX. End users can specify a Burner EOA from their primary EOA, and then use that burner address to play games. The Burner EOA can then sign messages for game moves without user interaction without any risk to the NFTs or other assets owned by the primary EOA._

Session

event Session(address owner, address authorized, uint256 length)

Unauthorized

error Unauthorized()

InvalidSignature

error InvalidSignature()

InvalidOwnership

error InvalidOwnership()

OffchainLookup

error OffchainLookup(address sender, string[] urls, bytes callData, bytes4 callbackFunction, bytes extraData)

ADMIN_ROLE

bytes32 ADMIN_ROLE

ERC721_TYPEHASH

bytes32 ERC721_TYPEHASH

_nonces

mapping(address => uint256) _nonces

_sessions

mapping(address => struct IForwardRequest.PlaySession) _sessions

urls

string[] urls

PlaySession

contract IEssentialPlaySession PlaySession

constructor

constructor(string name, string[] _urls) public

setOwnershipSigner

function setOwnershipSigner(address newSigner) external

Change the ownership signer

setPlaySessionOperator

function setPlaySessionOperator(address playSession) external

Change the PlaySession source

getNonce

function getNonce(address from) external view returns (uint256)

Get current nonce for EOA

getSession

function getSession(address authorizer) external view returns (struct IForwardRequest.PlaySession)

Get current session for Primary EOA

createSession

function createSession(address authorized, uint256 length) external

Allow `authorized` to use your NFTs in a game for `length` seconds. Your NFTs will not be held in custody or approved for transfer.

preflight

function preflight(struct IForwardRequest.ERC721ForwardRequest req, bytes signature) public view

Submit a meta-tx request and signature to check validity and receive a response with data useful for fetching a trusted proof per EIP-3668.

Per EIP-3668, a valid signature will cause a revert with useful error params.

executeWithProof

function executeWithProof(bytes response, bytes extraData) external payable returns (bool, bytes)

Re-submit a valid meta-tx request with trust-minimized proof to execute the transaction.

The RPC call and re-submission should be handled by your Relayer client

Name	Type	Description
response	bytes	The unaltered bytes reponse from a call made to an RPC url from OffchainLookup::urls
extraData	bytes	The unaltered bytes from OffchainLookup::extraData

verify

function verify(struct IForwardRequest.ERC721ForwardRequest req, bytes signature) public view returns (bool)

Submit a meta-tx request where a proof of ownership is not required.

Useful for transactions where the signer is not using a specific NFT, but values are still required in the signature - use the zero address for nftContract and 0 for tokenId

execute

function execute(struct IForwardRequest.ERC721ForwardRequest req, bytes signature) public payable returns (bool, bytes)

verifyRequest

function verifyRequest(struct IForwardRequest.ERC721ForwardRequest req, bytes signature) internal view returns (bool)

verifyAuthorization

function verifyAuthorization(struct IForwardRequest.ERC721ForwardRequest req) internal view returns (bool)