Can't create 'MultiSignature' type in addSignature

[hanwencheng]

Use the following code to inject signature:

    const signature = registry.createType('Sr25519Signature', signatureRaw);
        //signature is a length 64 u8 array
    unsignedTx.addSignature(signer, signature, u8aPayload);

ends with the error

error is Error: createType(MultiSignature):: Unable to create Enum via index 82, in Ed25519, Sr25519, Ecdsa

which caused by the createType function here, I guess the Enum type 'MultiSignature' cannot be direct created.

[jacogr]

64-bytes is not a valid MultiSignature. That is 65 bytes in length -

• the first byte is the indicator, 0=ed25519, 1=sr25519, 2=edcsa
• the last 64 bytes is the actual signature

[hanwencheng]

I use Keyring for testing with a prefixed bytes, but it turns out to be a bad proof.

e,.g

//This function get the 65 bytes signature with first byte as indicator
function prefixSignature (signatureRaw: ArrayLike<number>): Uint8Array {
    const u8aSignature = Uint8Array.from(signatureRaw);
    const u8aHeader = new Uint8Array([1]);
    const signature = new Uint8Array(65);
    signature.set(u8aHeader);
    signature.set(u8aSignature, 1);
    return signature;
}

const suri = 'ability cave solid soccer gloom thought response hard around minor want welcome//kusama';
const keyring = new Keyring({ss58Format: 42, type: 'sr25519'});
const signer:KeyringPair = keyring.addFromUri(suri, undefined, 'sr25519');
console.assert(senderAddress === signer.address, 'address should be the same ');

const payload:SignerPayload = registry.createType('SignerPayload', payloadRaw, { version: payloadRaw.version });
const signatureRaw = signer.sign(hexToU8a(payload.toRaw().data));

//if prefix the u8a then it is a bad proof after sending
const isBadproof = signer.verify(hexToU8a(payload.toRaw().data), prefixSignature(signatureRaw));

//if not prefixed then can't add signature
unsignedTx.addSignature(senderAddress, signatureRaw, payload.toPayload());

unsignedTx.send();

And the Signing with Keypair here is aligned with test code in SingleAccountSigner as well as the add signature process in signViaSigner.

So I am not sure what is the correct way to add the prefix.

[jacogr]

If you sign via the keyring, pass the withType: true option and it generates a MultiSignature.

[jacogr]

Here is an example of that - https://github.com/polkadot-js/api/blob/master/packages/types/src/extrinsic/v4/ExtrinsicPayload.ts#L87

(So you can also just skip creating a signer payload, pass the data as received into creating an ExtrinsicPayload and call sign on it - like here where it gets a SignerPayload and signs it just using the exposed helper on ExtrinsicPayload, https://github.com/polkadot-js/extension/blob/master/packages/extension-base/src/background/RequestExtrinsicSign.ts#L18)

[polkadot-js-bot]

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