SolidityKeccak256 without tightly packing

I have an ABIEncoderV2 struct that holds 3 arrays as such

    struct Update {
        address[] target;
        uint256[] value;
        bytes[] data;
    }

We hash this struct but these types can’t be packed by the ABI, but I still need to get the hash of said struct in JS. bytes32 updateHash = keccak256(abi.encode(_update));

since solidityKeccak256(types, values) tightly packs the data I can’t use that , is there an alternative that doesn’t pack the data?

i.e. utils.solidityKeccak256(["address[], uint256[], bytes[]"], [update.target, update.value, update.data]) would not work due to reasons mentioned. I think it would even throw an error IIUC.

[ricmoo]

You need to use the normal encoder. You are correct, the solidity* functions are only for tightly packed.

To hash normally, use utils.defaultAbiCoder.encode([ "tuple(address[] target, uint[] value, bytes[] data)" ], [ objectHere ]) and you can then just use the normal utils.keccak256 on that. This should match the abi.encode in Solidity. 😃

One quick note about your API, if you allow calls that use ecrecover to establish the from, you likely want to include a nonce as well to prevent replaying. You may already have other protection from this, but just in case; for delegated transactions that is often overlooked. 😃

[jtremback]

Ah, that works.