Ecrecover in smart contract doesn't return my address

Question

I'm trying to call a smart contract on Base L2 that has an ecrecover function, but when I sign a message and pass it my r,s,v values (contract accepts 4 params, all uint256, presumably hashedmessage, r, s, v), it never returns my address? I'm using ethers and the code below, am I doing something wrong?

const ethers = require('ethers');

async function main(message) {
    const provider = new ethers.providers.JsonRpcProvider('https://goerli.base.org');

    const wallet = new ethers.Wallet('private-key', provider);
    console.log('Signing wallet address:', wallet.address);
    const contractAddress = 'addr';
    
    const messageHash = ethers.utils.keccak256(ethers.utils.toUtf8Bytes(message));
    const signature = await wallet.signMessage(ethers.utils.arrayify(messageHash));
    
    const sig = ethers.utils.splitSignature(signature);
    
    const functionSelector = 'functionname';
    const arg0 = messageHash.slice(2);
    const arg1 = ethers.utils.hexZeroPad(ethers.utils.hexlify(sig.v), 32).slice(2);
    const arg2 = sig.r.slice(2);
    const arg3 = sig.s.slice(2);
    
    const data = functionSelector + arg0 + arg1 + arg2 + arg3;
    
    const rawTransaction = {
        to: contractAddress,
        value: ethers.utils.parseEther("0"),
        gasPrice: ethers.utils.parseUnits("1", "gwei"),
        gasLimit: ethers.utils.hexlify(1000000),
        nonce: await wallet.getTransactionCount(),
        data: '0x' + data,
        chainId: 84531  // Base Testnet Chain ID
    };
    
    const signedTransaction = await wallet.signTransaction(rawTransaction);
    
    try {
        const txResponse = await provider.sendTransaction(signedTransaction);
        console.log('Transaction sent:', txResponse.hash);
        
        const receipt = await txResponse.wait();
        console.log('Transaction confirmed:', receipt.transactionHash);

    } catch (error) {
        console.error('Error:', error);
    }
}

main('Hello World');

Contract decompiled code:

def unknown7e392050(uint256 _param1, uint256 _param2, uint256 _param3, uint256 _param4) payable: 
  require calldata.size - 4 >=′ 128
  require _param1 == _param1
  require _param2 == uint8(_param2)
  require _param3 == _param3
  require _param4 == _param4
  signer = erecover(_param1, _param2 << 248, _param3, _param4) # precompiled
  if not erecover.result:
      revert with ext_call.return_data[0 len return_data.size]
  log 0xe1f54da2: _param1, addr(signer)
  if addr(signer) != caller:
      revert with 0, 'Signer must be the message sender'
  return 5

Answer 1

Let's start with the fact that the function in the smart contract works correctly if you pass it valid values.

Judging by the code, you are using ethers version 5.6(7).+. The inconsistency of the signature check on messageHash is that wallet.signMessage adds its prefix = "\x19Ethereum Signed Message:\n" to your messageHash string.

There are two solutions.

You can generate the hash separately instead of arg0 to send to rawTransaction

Or, what I recommend, upgrade to ethers 6.7 and use the following code to sign the message:

    const signer = new ethers.SigningKey(privateKey);
    const messageHash = await ethers.solidityPackedKeccak256([ "string", "uint" ], [ message, message.length ] );
    const signature = signer.sign(messageHash);

//    console.log(`messageHash: ${messageHash}`);
//    console.log(`v: ${sign.v}`);
//    console.log(`r: ${sign.r}`);
//    console.log(`s: ${sign.s}`);