Bug: Zero address returned from contract call causes exception

[cryptobys-rami]

I found this bug in the library where a zero address returned from a contract results in an exception (because zero address is '0x0'). I suggest manipulating return data from contracts to check for zero address. It is quite typical for contracts to search an internal map for an address, returning zero address if it cannot find it.

[Solido]

I think this is related to #239

0x is linked to UintType(length 256) then
final result = type.decode(buffer, offset + headersLength);
and fail on _decode32Bytes

[cryptobys-rami]

BTW - this happens any time any function returns the default variable. Not just for addresses, also other value types... maybe this is a hint?

[Solido]

Trying to debug the cause. Effect is a problem with Buffer decoding but even the 0x response is incorrect.
But I'm just starting using the API so it is a lot of research. Let's discuss here about details to solve this.

[cryptobys-rami]

Sure im happy to help. I ve worked around it by using a different library for reading from functions. Very annoying!

[Solido]

That was my question! This is the basic call of a function so not sure how the tests passes.
Which lib are you using? can we provide a PR to this lib?

[cryptobys-rami]

I used this: https://github.com/y-pakorn/flutter_web3

the problem with flutter_web3 library is that its not native dart, so impossible to debug anything. Also smaller community/less testing? plus side of flutter_web3 is that it uses ethers js library which is the gold standard.

Happy to help make web3dart better

[Solido]

Oh I see it is a wrapper around .js so it also mean limitation in going mobile or desktop.
Like you said less community and commits.

I'd rather help build a standard around web3dart if possible for multi platforms.

Digging now. Keep you updated in the coming hours.

[cryptobys-rami]

Im very keen on the mobile part.

basically at the moment its impossible to use web3dart with metamask on mobile platform
its also impossible to use it on mobile web unless it is run in metamask browser

would love to cooperate to make this possible.

[Solido]

It is possible you need to use wallet connect
You can reach me here https://twitter.com/BlueAquilae

[Solido]

Hi @simolus3 would you accept a bounty to resolve this case?
40euros to help support this project and help us with timing resolution.
Thank you for your consideration on the matter.

[cryptobys-rami]

happy to contribute (to the bounty) as well!

[simolus3]

Sorry for the delay on this issue. I'm not too involved in the Ethereum ecosystem anymore, but I'll try to maintain this package as best as I can.

I tried to reproduce this issue with the following contract:

pragma solidity >=0.7.0 <0.9.0;

contract ReturnDefaults {
    function zero_int() public pure returns (int) {
        return 0;
    }

    function zero_address() public pure returns (address) {
        return address(0);
    }
}

I've deployed this to a local Ganache instance and then ran this script:

import 'package:http/http.dart';
import 'package:web3dart/web3dart.dart';

import 'test.g.dart';

Future<void> main() async {
  final client = Web3Client('http://localhost:7545', Client());
  final contract = Test(
      address:
          EthereumAddress.fromHex('0x4BBA8dcCAff0Dd855e6EC6400cc8494Bfa904c57'),
      client: client);

  print(await contract.zero_address());
  print(await contract.zero_int());
}

This prints zero for me, I don't get the range error here. If you have clear instructions on how to reproduce this (ideally, some simple contract source code + the local chain software) I'm happy to take another look. I don't need a bounty for this, just happy to help.

[Solido]

Thx for the quick reply. The easiest way is to use hardhat
https://hardhat.org/getting-started/#installation

It will create a default local chain and contract

pragma solidity ^0.8.0;

import "hardhat/console.sol";

contract Greeter {
    string private greeting;

    constructor(string memory _greeting) {
        console.log("Deploying a Greeter with greeting:", _greeting);
        greeting = _greeting;
    }

    function greet() public view returns (string memory) {
        return greeting;
    }

    function setGreeting(string memory _greeting) public {
        console.log("Changing greeting from '%s' to '%s'", greeting, _greeting);
        greeting = _greeting;
    }
}

Called greet() will fail as a default example.

[Solido]

@simolus3 Who is taking care of this repo now?

[simolus3]

That also works for me? I ran npx hardhat node followed by npx hardhat run scripts/sample-script.js --network localhost.

import 'package:http/http.dart';
import 'package:web3dart/web3dart.dart';

import 'test.g.dart';

Future<void> main() async {
  final client = Web3Client('http://localhost:8545', Client());
  final contract = Test(
      address:
          EthereumAddress.fromHex('0x5FbDB2315678afecb367f032d93F642f64180aa3'),
      client: client);

  print(await contract.greet()); // Hello, Hardhat!
}

I get the "Value not in range: 32" error only if I pick the wrong contract address. The error message sure could be better here, but I assume that's not the actual cause for you?

Who is taking care of this repo now?

I still am. If anyone wants to help, I'm happy to add new maintainers or transfer the repo, but I need to make sure it's not going into the wrong hands since this package may manage private keys for users.