ERC-1271

Allow smart contracts signage

ERC-1271, which allows for on-chain signature verification for Smart Contracts (since contracts do no have private keys).

• The verifying contract would get passed in the 32-byte hash that it wants to verify along with an implementation dependant byte array - domain seperator.

• We expect a return of the bytes4 magic value 0x1626ba7e when function passes.

• signer contract(multi-sig) must implement isValidSignature and return the magicValue

  • up to the contract to implement the logic of what determines a valid signature

  • if its multi-sig: could be concatentation of the various users' signatures

It's essential to understand that you never will be able to sign with your smart contract account. Only we will create a system to delegate the signature to another account in the name of your smart contract.

IMplementation example:

For example we would have to incorporate the following:

{...}
import {Address} from "@openzeppelin/contracts/utils/Address.sol";
import {IERC1271} from "@openzeppelin/contracts/interfaces/IERC1271.sol";
{...}


if (Address.isContract(sellOrder.signer)) {
    (bool success, bytes memory data) = sellOrder.signer.staticcall(abi.encodeWithSelector(IERC1271.isValidSignature.selector, digest, abi.encodePacked(r, s, v));
        
    if (!success) revert MISSING_VALID_SIGNATURE_FUNCTION_EIP1271;
    
    bytes4 magicValue = abi.decode(data, (bytes4));
    // must return the bytes4 magic value 0x1626ba7e when function passes
    if (magicValue != 0x1626ba7e) revert SIGNATURE_INVALID_EIP1271;

• It is established in the standard that in case of success, the function must return the value 0x1626ba7e

• This is not a random value. It is the signature of the function isValidSignature(bytes32,bytes)

Links

• https://ethereum.stackexchange.com/questions/135761/need-help-on-how-eip-712-works-and-where-are-signatures-stored

• https://ethereum.stackexchange.com/questions/27571/sign-data-with-a-contract-account

• https://ethereum.stackexchange.com/questions/11252/smart-contract-transaction-signature