feat: Update SuperchainWETH FMA (#246)

* feat: Update SuperchainWETH FMA

* fix instance of superchainweth

* rename to fma-superchainethbridge

Author: tremarkley

security/fma-shared-lockbox.md

@@ -9,7 +9,7 @@
 
 ## Introduction
 
-This document covers the changes introduced by the addition of the Shared Lockbox design, a singleton contract that stores all ETH liquidity for a given set of interoperable chains. It addresses the [ETH withdrawals problem](https://github.com/ethereum-optimism/specs/issues/362) by the introduction of [SuperchainWETH](https://github.com/ethereum-optimism/specs/blob/main/specs/interop/superchain-weth.md). The following components are:
+This document covers the changes introduced by the addition of the Shared Lockbox design, a singleton contract that stores all ETH liquidity for a given set of interoperable chains. It addresses the [ETH withdrawals problem](https://github.com/ethereum-optimism/specs/issues/362) by the introduction of [SuperchainETHBridge](https://github.com/ethereum-optimism/specs/blob/main/specs/interop/superchain-eth-bridge.md). The following components are:
 
 - **Contracts**:
     - Introducing `SharedLockbox`: Stores all ETH liquidity for an interoperable graph. Only authorized `OptimismPortal` addresses can call `lockETH` and `unlockETH`.

security/fma-superchainweth.md renamed to security/fma-superchainethbridge.md

@@ -1,4 +1,4 @@
-# SuperchainWETH: Failure Modes and Recovery Path Analysis
+# SuperchainETHBridge: Failure Modes and Recovery Path Analysis
 
 | Author | Joxes, Gotzen, Parti |
 | --- | --- |
@@ -9,20 +9,22 @@
 
 ## Introduction
 
-This document covers the addition of SuperchainWETH, an interop-enabled version of the WETH contract that allows ETH to be moved across a set of interoperable chains. It act as a wrapper contract compliant with the SuperchainERC20 standard and also have built-in bridging logic. The following components are included:
+This document covers the addition of the `SuperchainETHBridge` contract, an abstraction layer on top of the `L2toL2CrossDomainMessenger` specifically designed for native ETH transfers between chains. The following components are included:
 
 - **Contracts**:
-    - Introducing the `SuperchainWETH` predeploy proxy and implementation contract. It enables wrapping ETH into SuperchainWETH and includes logic for direct ETH interop transfers.
-    - Introducing the `ETHLiquidity` predeploy proxy and implementation contract. It is designed to facilitate the conversion of SuperchainWETH into native ETH—triggered when the supply increases through `crosschainMint` via `relayERC20`—by maintaining a large reserve of native ETH.
+    - Introducing the `SuperchainETHBridge`predeploy proxy and implementation contract. It uses the `L2toL2CrossDomainMessenger` to send and relay messages that handle ETH transfers between chains.
+    - Introducing the `ETHLiquidity` predeploy proxy and implementation contract. It is designed to provide the ETH for the `SuperchainETHBridge` to facilitate ETH transfers between chains, by maintaining a large reserve of native ETH.
 
 Below are references for this project:
 
 - Design doc:
-    - Introduction of SuperchainWETH: https://github.com/ethereum-optimism/design-docs/blob/main/protocol/interoperable-ether.md
-    - Handling SuperchainWETH transfers: https://github.com/ethereum-optimism/design-docs/blob/main/protocol/interoperable-ether-transfers.md
-- Specs: https://github.com/ethereum-optimism/specs/blob/main/specs/interop/superchain-weth.md
+    - Introduction of SuperchainETHBridge: https://github.com/ethereum-optimism/design-docs/blob/main/protocol/superchain-eth-bridge.md
+    - Handling ETH transfers: https://github.com/ethereum-optimism/design-docs/blob/main/protocol/interoperable-ether-transfers.md
+- Specs: 
+   - `SuperchainETHBridge`: https://github.com/ethereum-optimism/specs/blob/main/specs/interop/superchain-eth-bridge.md
+   - `ETHLiquidity`: https://github.com/ethereum-optimism/specs/blob/main/specs/interop/eth-liquidity.md
 - Implementation:
-    - `SuperchainWETH`: https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/src/L2/SuperchainWETH.sol
+    - `SuperchainETHBridge`: https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/src/L2/SuperchainETHBridge.sol
     - `ETHLiquidity`: https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/src/L2/ETHLiquidity.sol
 
 
@@ -37,17 +39,17 @@ Below are references for this project:
 
 ### FM1: Insufficient ETH in `ETHLiquidity`
 
-- **Description:** If `ETHLiquidity` lacks sufficient ETH, mint calls will revert when the contract attempts to forward funds using `SafeSend`. This breaks bridging flows dependent on `relayETH`  and `crosschainMint`.
+- **Description:** If `ETHLiquidity` lacks sufficient ETH, mint calls will revert when the contract attempts to forward funds using `SafeSend`. This breaks bridging flows dependent on `relayETH`.
 - **Risk Assessment:** Medium.
-    - Potential Impact: High. Not having enough ETH balance in `ETHLiquidity` prevents relaying ETH or mint SuperchainWETH through `crosschainMint`, which would greatly degrade the user experience, as they would be temporarily stuck. The situation becomes even more serious if the affected cross-chain messages expire before the issue can be resolved, making it impossible to retry the relay and get the funds in destination chain.  
+    - Potential Impact: High. Not having enough ETH balance in `ETHLiquidity` prevents relaying ETH, which would greatly degrade the user experience, as they would be temporarily stuck. The situation becomes even more serious if the affected cross-chain messages expire before the issue can be resolved, making it impossible to retry the relay and get the funds in destination chain.  
     - Likelihood: Very low. `ETHLiquidity` starts with a maximum balance (`type(uint248).max`).
 - **Mitigations:** Our current codebase includes tests to check if the `mint` request exceeds the contract’s balance ([test](https://github.com/ethereum-optimism/optimism/blob/dd37e6192c37ed4c5b18df0269f065f378c495cc/packages/contracts-bedrock/test/L2/ETHLiquidity.t.sol#L103)). Initial ETH supply in `ETHLiquidity` is `type(uint248).max` ([test](https://github.com/ethereum-optimism/optimism/blob/dd37e6192c37ed4c5b18df0269f065f378c495cc/packages/contracts-bedrock/test/L2/ETHLiquidity.t.sol#L29)) and equally set in all chains.
 - **Detection:** Perform checks on the `ETHLiquidity` balance as a preventive monitoring measure. User-filed support tickets may flag this issue in case of failure.
-- **Recovery Path(s):** Coordinate an L2 hard fork to replenish the `ETHLiquidity` contract. Investigate the causes of the depletion to determine if other factors are involved. Messages will need to be retried for relaying; otherwise, use the `expireMessage` feature if it is available and integrated into `SuperchainWETH`.
+- **Recovery Path(s):** Coordinate an L2 hard fork to replenish the `ETHLiquidity` contract. Investigate the causes of the depletion to determine if other factors are involved. Messages will need to be retried for relaying; otherwise, use the `expireMessage` feature if it is available and integrated into `SuperchainETHBridge`.
 
 ### FM2: Overflow during `burn` in `ETHLiquidity` due to max Balance
 
-- **Description:** If the `ETHLiquidity` contract has already reached the maximum allowed ETH balance (`type(uint256).max`), invoking the `sendETH` function (which triggers `crosschainBurn`) could cause an overflow. This occurs when `burn` is called with an amount that, when added to the current balance, exceeds the maximum `uint256` value. Such an overflow would cause a revert, since the proper Solidity version is used.
+- **Description:** If the `ETHLiquidity` contract has already reached the maximum allowed ETH balance (`type(uint256).max`), invoking the `sendETH` function could cause an overflow. This occurs when `burn` is called with an amount that, when added to the current balance, exceeds the maximum `uint256` value. Such an overflow would cause a revert, since the proper Solidity version is used.
 - **Risk Assessment:** Low.
     - Potential Impact: Medium. Reverts during `sendETH` calls are expected when the requested amount exceeds the maximum value representable by a `uint256`.
     - Likelihood: Very low. `ETHLiquidity` starts with a maximum balance (`type(uint248).max`) which is still far from `uint256` limit.
@@ -61,7 +63,7 @@ See [fma-generic-contracts.md](https://github.com/ethereum-optimism/design-docs/
 
 - [x]  Check this box to confirm that these items have been considered and updated if necessary.
 
-See [relevant FMAs to SuperchainWETH, To Do] 
+See [relevant FMAs to SuperchainETHBridge, To Do] 
 
 - [ ]  Check this box to confirm that these items have been considered and updated if necessary.
 
@@ -70,8 +72,8 @@ See [relevant FMAs to SuperchainWETH, To Do]
 - [x]  Resolve all the comments.
 - [ ]  FM1, FM2: Establish a balance monitoring measure in `ETHLiquidity` (optional).
 - [ ]  Ensure the support team is aware of these failure modes and prepared to respond.
-- [ ]  **Ensure that the actions items specified in each FMAs on which SuperchainWETH depends are completed.**
+- [ ]  **Ensure that the actions items specified in each FMAs on which SuperchainETHBridge depends are completed.**
 
 ## Audit Requirements
 
-Following the [Audit Framework](https://gov.optimism.io/t/op-labs-audit-framework-when-to-get-external-security-review-and-how-to-prepare-for-it/6864), SuperchainWETH fits within the second budget, which includes smart contract code that secures assets. That means the `SuperchainWETH.sol` and `ETHLiquidity.sol` and associated interop contract dependencies (`CrossL2Inbox`, `L2ToL2CrossDomainMessenger`, `SuperchainTokenBridge`, `L1BlockInterop`, `SystemConfigInterop`, `OptimismPortalInterop`) require an audit before going to production.
+Following the [Audit Framework](https://gov.optimism.io/t/op-labs-audit-framework-when-to-get-external-security-review-and-how-to-prepare-for-it/6864), SuperchainETHBridge fits within the second budget, which includes smart contract code that secures assets. That means the `SuperchainETHBridge.sol` and `ETHLiquidity.sol` and associated interop contract dependencies (`CrossL2Inbox`, `L2ToL2CrossDomainMessenger`, `SuperchainTokenBridge`, `L1BlockInterop`, `SystemConfigInterop`, `OptimismPortalInterop`) require an audit before going to production.