MAX_SAFE_CHAIN_ID no longer needed

[Solpatium]

Describe the bug

Problem

MetaMask rejects chain ids bigger than 4503599627370476. It is a problem for networks that want to use a bigger chain id. In order to use them with MetaMask some mapping would have to be added.

Source of the problem

#10224 introduced MAX_SAFE_CHAIN_ID for reasons described in https://gist.github.com/rekmarks/a47bd5f2525936c4b8eee31a16345553. At that time libraries used by MetaMask used basic js number for computations, without the support of big integers.
Two libraries mentioned:

• ethereumjs-tx@1.3.7 contained

const isValidEIP155V =
  vInt === this.getChainId() * 2 + 35 || vInt === this.getChainId() * 2 + 36

• ethereumjs-util@7.0.5 contained

v: chainId ? recovery + (chainId * 2 + 35) : recovery + 27,

Solution

Since then those libraries were updated and they accept big integers:

• @ethereumjs/tx@3.2.1 used by MetaMask's develop branch currently
• ethereumjs-util@7.0.10 used by MetaMask's develop branch currently

We could use changes in these libraries and limit chain id to fit in uint256, so it has to be lower than 2**256.

I can try to create a PR with required changes if MetaMask maintainers approve suggested solution.

Steps to reproduce

1. Go to https://metamask.github.io/api-playground/api-documentation/#wallet_addEthereumChain and click "TRY IT NOW" for the example request.
2. Replace chainId with 0xfffffffffffed (MAX_SAFE_CHAIN_ID+1).
3. Send the request.

Error messages or log output

{
  "jsonrpc": "2.0",
  "id": 0,
  "error": {
    "code": 32329,
    "message": "Invalid chain ID \"0xfffffffffffed\": numerical value greater than max safe value. Received:\n0xfffffffffffed"
  }
}

Version

10.9.3

Build type

No response

Browser

Chrome

Operating system

MacOS

Hardware wallet

No response

Additional context

No response

[rekmarks]

I won't be the one to fix this, but I just wanted to say thank you @Solpatium for doing your research and creating such an excellent issue.

I think we'd accept any solution that guarantees safe number handling. We'd have to bump our minimum Chrome version, but we have to do this soon due to changes the ethereumjs team is making in any event (cc: @ryanio), so that should be fine. Someone will confirm that this approach is fine shortly.