From 6a500d930dde299c030d0ed8274309f91fa93263 Mon Sep 17 00:00:00 2001
From: Zaki Manian <zaki@iqlusion.io>
Date: Fri, 23 Aug 2024 14:15:35 +0100
Subject: [PATCH] Fixes for the Sequencer downtime oracle to correctly detect
 invalid rounds

---
 .../permutations/SequencerPriceRouter.sol     | 20 ++++++++++++++-----
 .../SequencerPriceRouter.t.sol                | 14 +++++++++++--
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/src/modules/price-router/permutations/SequencerPriceRouter.sol b/src/modules/price-router/permutations/SequencerPriceRouter.sol
index dd7e1b0c1..aa44a2c4d 100644
--- a/src/modules/price-router/permutations/SequencerPriceRouter.sol
+++ b/src/modules/price-router/permutations/SequencerPriceRouter.sol
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: Apache-2.0
 pragma solidity 0.8.21;
 
-import {PriceRouter, Registry, ERC20, IChainlinkAggregator} from "src/modules/price-router/PriceRouter.sol";
+import { PriceRouter, Registry, ERC20, IChainlinkAggregator } from "src/modules/price-router/PriceRouter.sol";
 
 /**
  * @title SequencerPriceRouter
@@ -13,6 +13,7 @@ contract SequencerPriceRouter is PriceRouter {
 
     error SequencerPriceRouter__SequencerDown();
     error SequencerPriceRouter__GracePeriodNotOver();
+    error SequencerPriceRouter__InvalidRound();
 
     //============================== IMMUTABLES ===============================
 
@@ -27,9 +28,13 @@ contract SequencerPriceRouter is PriceRouter {
      */
     uint256 internal immutable gracePeriod;
 
-    constructor(address _sequencerUptimeFeed, uint256 _gracePeriod, address newOwner, Registry _registry, ERC20 _weth)
-        PriceRouter(newOwner, _registry, _weth)
-    {
+    constructor(
+        address _sequencerUptimeFeed,
+        uint256 _gracePeriod,
+        address newOwner,
+        Registry _registry,
+        ERC20 _weth
+    ) PriceRouter(newOwner, _registry, _weth) {
         sequencerUptimeFeed = IChainlinkAggregator(_sequencerUptimeFeed);
         gracePeriod = _gracePeriod;
     }
@@ -41,7 +46,7 @@ contract SequencerPriceRouter is PriceRouter {
      *         to price assets, as the datafeeds could be stale, and need to be updated.
      */
     function _runPreFlightCheck() internal view override {
-        (, int256 answer, uint256 startedAt,,) = sequencerUptimeFeed.latestRoundData();
+        (, int256 answer, uint256 startedAt, , ) = sequencerUptimeFeed.latestRoundData();
 
         // This check should make TXs from L1 to L2 revert if someone tried interacting with the cellar while the sequencer is down.
         // Answer == 0: Sequencer is up
@@ -50,6 +55,11 @@ contract SequencerPriceRouter is PriceRouter {
             revert SequencerPriceRouter__SequencerDown();
         }
 
+        // Detect invalid round in the oracle.
+        if (startedAt == 0) {
+            revert SequencerPriceRouter__InvalidRound();
+        }
+
         // Make sure the grace period has passed after the
         // sequencer is back up.
         uint256 timeSinceUp = block.timestamp - startedAt;
diff --git a/test/testPriceRouter/SequencerPriceRouter.t.sol b/test/testPriceRouter/SequencerPriceRouter.t.sol
index 054ff5e5e..581555425 100644
--- a/test/testPriceRouter/SequencerPriceRouter.t.sol
+++ b/test/testPriceRouter/SequencerPriceRouter.t.sol
@@ -21,7 +21,7 @@ contract SequencerPriceRouterTest is Test {
 
     // Variables so this contract can act as a mock sequencer uptime fee.
     int256 mockAnswer = type(int256).max;
-    uint256 mockStartedAt = 0;
+    uint256 mockStartedAt = 1;
 
     function setUp() external {
         // Setup forked environment.
@@ -45,6 +45,16 @@ contract SequencerPriceRouterTest is Test {
         // Sequencer is currently up so pricing succeeds.
         sequencerPriceRouter.getPriceInUSD(USDC);
 
+        //if the sequencer is oracle experiences an invalid round
+        mockAnswer = 0;
+        mockStartedAt = 0;
+
+        // Pricing calls revert.
+        vm.expectRevert(
+            bytes(abi.encodeWithSelector(SequencerPriceRouter.SequencerPriceRouter__InvalidRound.selector))
+        );
+        sequencerPriceRouter.getPriceInUSD(USDC);
+
         // But if sequencer goes down.
         mockAnswer = 1;
         mockStartedAt = block.timestamp - 1;
@@ -78,6 +88,6 @@ contract SequencerPriceRouterTest is Test {
         (roundID, answer, startedAt, updatedAt, answeredInRound) = IChainlinkAggregator(arbitrumSequencerUptimeFeed)
             .latestRoundData();
         if (mockAnswer != type(int256).max) answer = mockAnswer;
-        if (mockStartedAt != 0) startedAt = mockStartedAt;
+        startedAt = mockStartedAt;
     }
 }