Invalid Transaction: Transaction has a bad signature - Ledger signature into tx

Question

I am attempting to submit a transaction using Polkadot JS API and a signature that has been signed by Ledger. Upon passing it to send I get the Invalid Transaction: Transaction has a bad signature error.

The payload is generated roughly as follows:

const lastHeader = await api.rpc.chain.getHeader();

const payload = {
        specVersion: api.runtimeVersion.specVersion.toHex(),
        transactionVersion: api.runtimeVersion.transactionVersion.toHex(),
        address: submitAddress,
        blockHash: lastHeader.hash.toHex(),
        blockNumber: lastHeader.number.toHex(),
        genesisHash: api.genesisHash.toHex(),
        method: api.createType('Call', tx).toHex(),
        nonce: tx.nonce.toHex(),
        signedExtensions: Object.values(
          api.registry.metadata.extrinsic.signedExtensions.toHuman() || {}
        ).map((e: any) => e.identifier),
        tip: tx.tip.toHex(),
        version: tx.version,
};

const raw = api.registry.createType('ExtrinsicPayload', payload);

The Ledger device is successfully generating a signature, using @zondax/ledger-substrate-js's sign method.

I am then injecting this signature into the tx like so:

tx.addSignature(from, hexAddPrefix(signature.toString('hex')));

const unsub = await tx.send(({ status, events = [] }: AnyApi) => {
   ...
});

This is yielding an error: RpcError: 1010: Invalid Transaction: Transaction has a bad signature.

console logging tx.toHuman() after addSignature gives the following:

{
    "isSigned": true,
    "method": {
        "args": {
            "amount": "20,000,000,000",
            "pool_id": "15"
        },
        "method": "join",
        "section": "nominationPools"
    },
    "era": {
        "ImmortalEra": "0x00"
    },
    "nonce": "0",
    "signature": "0x4ce81c594615f5b0812b29f392081ae07fd65a142998fca1a2f9f81d67ded13098cd544689b401ca7c915b23ec6bf58a51aba7ba4eec51f7eb491f5af0c95b09",
    "signer": {
        "Id": "16F1ghy4bMr72BGyin7ryTxiQqJFJwpePsNJcZo1p6dUGVZT"
    },
    "tip": "0"
}

What is incorrect / missing in the above snippets that is yielding this error?

Thanks

Answer 1

Solution

Detailed explanations of the problem and great troubleshooting pointers can be found on the JS Apps issue here: https://github.com/polkadot-js/api/issues/5555

To summarise, ensure the entire payload is constructed using Polkadot JS types:

const lastHeader = await api.rpc.chain.getHeader();
const blockNumber = api.registry.createType(
  'BlockNumber',
  lastHeader.number.toNumber()
);
const method = api.createType('Call', tx);
const era = api.registry.createType('ExtrinsicEra', {
  current: lastHeader.number.toNumber(),
  period: 64,
});

const nonceRaw = api.query.system.account(address)?.nonce || 0;
const nonce = api.registry.createType('Compact<Index>', nonceRaw);

const payload = {
  specVersion: api.runtimeVersion.specVersion.toHex(),
  transactionVersion: api.runtimeVersion.transactionVersion.toHex(),
  address: address,
  blockHash: lastHeader.hash.toHex(),
  blockNumber: blockNumber.toHex(),
  era: era.toHex(),
  genesisHash: api.genesisHash.toHex(),
  method: method.toHex(),
  nonce: nonce.toHex(),
  signedExtensions: [
    'CheckNonZeroSender',
    'CheckSpecVersion',
    'CheckTxVersion',
    'CheckGenesis',
    'CheckMortality',
    'CheckNonce',
    'CheckWeight',
    'ChargeTransactionPayment',
  ],
  tip: api.registry.createType('Compact<Balance>', 0).toHex(),
  version: tx.version,
};
const raw = api.registry.createType('ExtrinsicPayload', payload, {
  version: payload.version,
});

When it comes to addSignature we need to pass this payload along with address and signature:

tx.addSignature(address, txSignature, txPayload);

const unsub = await tx.send(({ status, events = [] }: AnyApi) => {
   ...
});