From 307cd98640917382e61157fc71b5b4fd6d06ef04 Mon Sep 17 00:00:00 2001
From: Gregory Markou <16929357+GregTheGreek@users.noreply.github.com>
Date: Fri, 3 Sep 2021 15:08:18 +0300
Subject: [PATCH] Strict enforcement of chainId (#3788)

* add eip

* updated file

* cleanup language

* small change

* Update eip-.md

* add security notice

* update description

* add discussion to

* Update EIPS/eip-3788.md

Co-authored-by: Micah Zoltu <micah@zoltu.net>

Co-authored-by: Micah Zoltu <micah@zoltu.net>
---
 EIPS/eip-3788.md | 60 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 EIPS/eip-3788.md

diff --git a/EIPS/eip-3788.md b/EIPS/eip-3788.md
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+---
+eip: 3788
+title: Strict enforcement of chainId
+description: Reject transactions that do not explicitly have the same chainId as the node's configuration.
+author: Gregory Markou (@GregTheGreek)
+discussions-to: https://ethereum-magicians.org/t/discussion-to-eip-3788-strict-enforcement-of-chainid/7001
+status: Draft
+type: Standards Track
+category: Core
+created: 2021-09-2
+requires: 155
+---
+
+## Abstract
+
+Reject transactions that do not explicitly have the same chainId as the node's configuration.
+
+## Motivation
+
+Per [EIP-155](./eip-155.md) a transaction with a `chainId = 0` is considered to be a valid 
+transaction. This was a feature to offer developers the ability to sumbit replayable transactions 
+across different chains. With the rise of evm compatible chains, many of which use forks, or packages
+from popular Ethereum clients, we are putting user funds at risk. This is because most wallet
+interfaces do not expose the chainId to the user, meaning they typically do not have insight
+into what chainId they are signing. Should a malicious actor (or accidental) choose to, they
+can easily have users submit transactions with a `chainId = 0` on a non-mainnet network, allowing
+the malicious actor to replay the transaction on ethereum mainnet (or other networks for that matter)
+as a grief or sophisticated attack.
+
+## Specification
+
+As of the fork block `N`, consider transactions with a `chaindId = 0` to be invalid. Such that 
+transactions are verified based on the nodes configuration. Eg:
+```
+if (node.cfg.chainId != tx.chainId) {
+    // Reject transaction
+}
+```
+
+## Rationale
+
+The configuration set by the node is the main source of truth, and thus should be explicitly used
+when deciding how to filter out a transaction. This check should exist in two places, as a filter
+on the JSON-RPC (eg: `eth_sendTransaction`), and stricly enforced on the EVM during transaction 
+validation.
+
+This ensures that users will not have transactions pending that will be guaranteed to fail, and
+prevents the transaction from being included in a block.
+
+## Backwards Compatibility
+This breaks all applications or tooling that submit transactions with a `chainId == 0` after block number `N`.
+
+## Test Cases
+TBD
+
+## Security Considerations
+It should be noted this will not prevent a malicious actor from deploying a network with `chainId = 1`, or copying any other networks chainId.
+
+## Copyright
+Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).