ERC7739Utils

*Utilities to process https://ercs.ethereum.org/ERCS/erc-7739[ERC-7739] typed data signatures that are specific to an EIP-712 domain. This library provides methods to wrap, unwrap and operate over typed data signatures with a defensive rehashing mechanism that includes the app's xref:api:utils/cryptography#EIP712-_domainSeparatorV4[EIP-712] and preserves readability of the signed content using an EIP-712 nested approach. A smart contract domain can validate a signature for a typed data structure in two ways:

• As an application validating a typed data signature. See typedDataSignStructHash.
• As a smart contract validating a raw message signature. See {personalSignStructHash}. NOTE: A provider for a smart contract wallet would need to return this signature as the result of a call to personal_sign or eth_signTypedData, and this may be unsupported by API clients that expect a return value of 129 bytes, or specifically the r,s,v parameters of an xref:api:utils/cryptography#ECDSA[ECDSA] signature, as is for example specified for xref:api:utils/cryptography#EIP712[EIP-712].*

State Variables

PERSONAL_SIGN_TYPEHASH

An EIP-712 type to represent "personal" signatures (i.e. mimic of personal_sign for smart contracts).

bytes32 private constant PERSONAL_SIGN_TYPEHASH = keccak256("PersonalSign(bytes prefixed)");

Functions

encodeTypedDataSig

Nest a signature for a given EIP-712 type into a nested signature for the domain of the app. Counterpart of decodeTypedDataSig to extract the original signature and the nested components.

function encodeTypedDataSig(
    bytes memory signature,
    bytes32 appSeparator,
    bytes32 contentsHash,
    string memory contentsDescr
) internal pure returns (bytes memory);

decodeTypedDataSig

*Parses a nested signature into its components. Constructed as follows: signature ‖ APP_DOMAIN_SEPARATOR ‖ contentsHash ‖ contentsDescr ‖ uint16(contentsDescr.length)

• signature is the signature for the (ERC-7739) nested struct hash. This signature indirectly signs over the original "contents" hash (from the app) and the account's domain separator.
• APP_DOMAIN_SEPARATOR is the EIP-712 EIP712-_domainSeparatorV4 of the application smart contract that is requesting the signature verification (though ERC-1271).
• contentsHash is the hash of the underlying data structure or message.
• contentsDescr is a descriptor of the "contents" part of the the EIP-712 type of the nested signature. NOTE: This function returns empty if the input format is invalid instead of reverting. data instead.*

function decodeTypedDataSig(bytes calldata encodedSignature)
    internal
    pure
    returns (bytes calldata signature, bytes32 appSeparator, bytes32 contentsHash, string calldata contentsDescr);

personalSignStructHash

Nests an ERC-191 digest into a PersonalSign EIP-712 struct, and returns the corresponding struct hash. This struct hash must be combined with a domain separator, using MessageHashUtils-toTypedDataHash before being verified/recovered. This is used to simulates the personal_sign RPC method in the context of smart contracts.

function personalSignStructHash(bytes32 contents) internal pure returns (bytes32);

typedDataSignStructHash

Nests an EIP-712 hash (contents) into a TypedDataSign EIP-712 struct, and returns the corresponding struct hash. This struct hash must be combined with a domain separator, using MessageHashUtils-toTypedDataHash before being verified/recovered.

function typedDataSignStructHash(
    string calldata contentsName,
    string calldata contentsType,
    bytes32 contentsHash,
    bytes memory domainBytes
) internal pure returns (bytes32 result);

typedDataSignStructHash

Variant of {typedDataSignStructHash-string-string-bytes32-bytes} that takes a content descriptor and decodes the contentsName and contentsType out of it.

function typedDataSignStructHash(string calldata contentsDescr, bytes32 contentsHash, bytes memory domainBytes)
    internal
    pure
    returns (bytes32 result);

typedDataSignTypehash

Compute the EIP-712 typehash of the TypedDataSign structure for a given type (and typename).

function typedDataSignTypehash(string calldata contentsName, string calldata contentsType)
    internal
    pure
    returns (bytes32);

decodeContentsDescr

Parse the type name out of the ERC-7739 contents type description. Supports both the implicit and explicit modes. Following ERC-7739 specifications, a contentsName is considered invalid if it's empty or it contains any of the following bytes , )\x00 If the contentsType is invalid, this returns an empty string. Otherwise, the return string has non-zero length.

function decodeContentsDescr(string calldata contentsDescr)
    internal
    pure
    returns (string calldata contentsName, string calldata contentsType);

_isForbiddenChar

function _isForbiddenChar(bytes1 char) private pure returns (bool);