signTransaction produces huge signature, which fails with 'ECDSA: invalid signature length'

Question

I'm trying to create a transaction (created with populateTransaction), and sign it offchain (the above result, passed as a parameter to signTransaction), but it seems it produces an invalid signature (you can see in the logs below), when I send it for ecrecover.

    // acc1, acc2 should sign the kickout method
    const acc1UnsignedTx = await vendor
      .connect(acc1)
      .populateTransaction.kickout(acc3, tokensToStake);

    const acc1Wallet = getWalletForIndex(0);
    const acc1KickoutSignature = await acc1Wallet.signTransaction(
      acc1UnsignedTx
    );

    // acc 2
    const acc2UnsignedTx = await vendor
      .connect(acc2)
      .populateTransaction.kickout(acc3, tokensToStake);

    const acc2Wallet = getWalletForIndex(1);
    const acc2KickoutSignature = await acc2Wallet.signTransaction(
      acc2UnsignedTx
    );

    console.log('acc2 unsigned tx ', acc2UnsignedTx)
    console.log("acc2 signature ", acc2KickoutSignature)

    // one of them call executeTransaction
    const nonceBefore = await vendor.nonce();
    await vendor.executeMultiSigTx(
      acc1UnsignedTx.to!,
      acc1UnsignedTx.value || 0,
      acc1UnsignedTx.data!,
      [acc1KickoutSignature, acc2KickoutSignature]
    );

const getWalletForIndex = (index: any) => {
    return Wallet.fromMnemonic(
      'test test test test test test test test test test test junk',
      `m/44'/60'/0'/0/${index}`
    );
  };

but I get

acc2 unsigned tx  {
  data: '0x512febdc0000000000000000000000003c44cdddb6a900fa2b585dd299e03d12fa4293bc00000000000000000000000000000000000000000000000ad78ebc5ac6200000',
  to: '0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512',
  from: '0x70997970C51812dc3A010C7d01b50e0d17dc79C8',
  gasLimit: BigNumber { _hex: '0x01badbd8', _isBigNumber: true }
}
acc2 signature  0xf8a680808401badbd894e7f1725e7734ce288f8367e1bb143e90bb3f051280b844512febdc0000000000000000000000003c44cdddb6a900fa2b585dd299e03d12fa4293bc00000000000000000000000000000000000000000000000ad78ebc5ac62000001ca0093579b23a74a1cd1d27956e2673ee70afe46e23792211e324bde43c72ea3a4ca06cd521fc22d17326e22285bcde455041ca83a1253d1f8d381aabfa281d426ed3
    1) should kickout through execute when required # of signatures are collected


  0 passing (1s)
  1 failing

  1) Vendor
       should kickout through execute when required # of signatures are collected:
     Error: VM Exception while processing transaction: reverted with reason string 'ECDSA: invalid signature length'

What am I doing wrong with the creation of the signature ? Why is it such a long string(338 length) ?

Answer 1

The value returned by signTransaction is a RLP-encoded raw Ethereum transaction including the signature.

For more info see:

• https://github.com/ethereum/execution-apis/blob/main/src/eth/sign.json#L28-L46
• https://medium.com/@bindassbasanta/sending-a-raw-transaction-ethereum-a7b75f845969