ERC-5568: Well-Known Format for Required Actions Ethereum Improvement Proposals AllCoreNetworkingInterfaceERCMetaInformational ⚠️ Review Standards Track: ERC ERC-5568: Well-Known Format for Required Actions Signal to wallets that an action is needed through a well-known function and revert reason Authors Gavin John (@Pandapip1) Created 2022-08-31 Requires EIP-140 This EIP is in the process of being peer-reviewed. If you are interested in this EIP, please participate using this discussion link. Table of Contents Abstract Motivation Specification Action Detection Custom Revert Reason Responding to a Revert Rationale Backwards Compatibility Human-Readable Revert Messages ERC-3668 Security Considerations Revert Reason Collisions Copyright Abstract This ERC introduces a minimalistic machine-readable (binary) format to signal to wallets that an action needs to be taken by the user using a well-known function and revert reason. It provides just enough data to be extendable by future ERCs and to take in arbitrary parameters (up to 64 kB of data). Example use cases could include approving a token for an exchange, sending an HTTP request, or requesting the user to rotate their keys after a certain period of time to enforce good hygiene. Motivation Oftentimes, a smart contract needs to signal to a wallet that an action needs to be taken, such as to sign a transaction or send an HTTP request to a URL. Traditionally, this has been done by hard-coding the logic into the frontend, but this ERC allows the smart contract itself to request the action. This means that, for example, an exchange or a market can directly tell the wallet to approve the smart contract to spend the token, vastly simplifying front-end code. Specification The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119. Action Detection interface IERC5568 { function walletSignal24(bytes32 selector, bytes function_data) view returns (uint24 instruction_id, bytes instruction_data); } The instruction_id of an instruction defined by an ERC MUST be its ERC number unless there are exceptional circumstances (be reasonable). An ERC MUST define exactly zero or one instruction_id. The structure of the instruction data for any instruction_id MUST be defined by the ERC that defines the instruction_id. To indicate that an action needs to be taken, return the instruction_id and instruction_data. To indicate no actions need to be taken, set instruction_id to be 0 and instruction_data to any value. Custom Revert Reason To signal an action was not taken, a compliant smart contract MUST revert with the following error: error WalletSignal24(uint24 instruction_id, bytes instruction_data) The instruction_id of an instruction defined by an ERC MUST be its ERC number unless there are exceptional circumstances (be reasonable). An ERC MUST define exactly zero or one instruction_id. The structure of the instruction data for any instruction_id MUST be defined by the ERC that defines the instruction_id. Responding to a Revert Before submitting a transaction to the mempool, the walletSignal24 function MUST be simulated locally. It MUST be treated as if it were a non-view function capable of making state changes (e.g. CALLS to non-view functions are allowed). If the resulting instruction_id is nonzero, an action needs to be taken. The instruction_id, and instruction_data MUST be taken from the walletSignal24 simulation. The instruction SHOULD be evaluated as per the relevant ERC. If the instruction is not supported by the wallet, it MUST display an error to the user indicating that is the case. The wallet MUST then re-evaluate the transaction, except if an instruction explicitly states that the transaction MUST NOT be re-evaluated. If an instruction is invalid, or the instruction_id, and instruction_data cannot be parsed, then an error MUST be displayed to the user indicating that is the case. The transaction MUST NOT be re-evaluated. Rationale This ERC was explicitly optimized for deployment gas cost and simplicity. It is expected that libraries will eventually be developed that makes this more developer-friendly. ERC-165 is not used, since the interface is simple enough that it can be detected simply by calling the function. Backwards Compatibility Human-Readable Revert Messages See Revert Reason Collisions. ERC-3668 ERC-3668 can be used alongside this ERC, but it uses a different mechanism than this ERC. Security Considerations Revert Reason Collisions It is unlikely that the signature of the custom error matches any custom errors in the wild. In the case that it does, no harm is caused unless the data happen to be a valid instruction, which is even more unlikely. Copyright Copyright and related rights waived via CC0. Citation Please cite this document as: Gavin John (@Pandapip1), "ERC-5568: Well-Known Format for Required Actions [DRAFT]," Ethereum Improvement Proposals, no. 5568, August 2022. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-5568. Ethereum Improvement Proposals Ethereum Improvement Proposals ethereum/EIPs Ethereum Improvement Proposals (EIPs) describe standards for the Ethereum platform, including core protocol specifications, client APIs, and contract standards.