v1.1 example update

beyond-hello-wormhole.md

@@ -8,16 +8,14 @@ HelloWormhole is a great example application, but has much room for improvement.
 
 Topics covered:
 
-- Protections
-  - Restricting the sender
-  - Preventing duplicate deliveries
+- Restricting the sender
 - Refunds
 - Chained Deliveries
 - Delivering existing VAAs
 
 ## Protections
 
-### Problem 1 - The greetings can come from anyone
+### Issue: The greetings can come from anyone
 
 A user doesn’t have to go through the HelloWormhole contract to request a greeting - they can call `wormholeRelayer.sendPayloadToEvm{value: cost}(…)` themselves!
 
@@ -49,26 +47,9 @@ Often, it is desirable that all of the requests go through your own source contr
     }
 ```
 
-### Problem 2 - The greetings can be relayed multiple times
+### Example Solution for Problem 1
 
-As mentioned in the first article, without having the mapping of delivery hashes to boolean, anyone can fetch the delivery VAA corresponding to a sent greeting, and have it delivered again to the target HelloWormhole contract! This causes another `GreetingReceived` event to be emitted from the same `senderChain` and `sender`, even though the sender only intended on sending this greeting once.
-
-**Solution:** In our implementation of receiveWormholeMessages, we store each delivery hash in a mapping from delivery hashes to booleans, to indicate that the delivery has already been processed. Then, at the beginning we can check to see if the delivery has already been processed, and revert if it has.
-
-```solidity
-
-    mapping(bytes32 => bool) public seenDeliveryVaaHashes;
-
-    modifier replayProtect(bytes32 deliveryHash) {
-        require(!seenDeliveryVaaHashes[deliveryHash], "Message already processed");
-        seenDeliveryVaaHashes[deliveryHash] = true;
-        _;
-    }
-```
-
-### Example Solution for Problems 1 and 2
-
-We provide a base class in the [Wormhole Solidity SDK](https://github.com/wormhole-foundation/wormhole-solidity-sdk) that includes the modifiers shown above, makes it easy to add these functionalities as such
+We provide a base class in the [Wormhole Solidity SDK](https://github.com/wormhole-foundation/wormhole-solidity-sdk) that includes the modifier shown above, makes it easy to add these functionalities as such
 
 ```solidity
     function receiveWormholeMessages(
@@ -83,7 +64,6 @@ We provide a base class in the [Wormhole Solidity SDK](https://github.com/wormho
         override
         onlyWormholeRelayer
         isRegisteredSender(sourceChain, sourceAddress)
-        replayProtect(deliveryHash)
     {
         latestGreeting = abi.decode(payload, (string));
 

src/HelloWormhole.sol

@@ -48,7 +48,7 @@ contract HelloWormhole is IWormholeReceiver {
         bytes[] memory, // additionalVaas
         bytes32, // address that called 'sendPayloadToEvm' (HelloWormhole contract address)
         uint16 sourceChain,
-        bytes32 deliveryHash // this can be stored in a mapping deliveryHash => bool to prevent duplicate deliveries
+        bytes32 // unique identifier of delivery
     ) public payable override {
         require(msg.sender == address(wormholeRelayer), "Only relayer allowed");
 

src/extensions/HelloWormholeConfirmation.sol

@@ -17,18 +17,39 @@ contract HelloWormholeConfirmation is Base, IWormholeReceiver {
 
     uint16 chainId;
 
-    enum MessageType {GREETING, CONFIRMATION}
+    enum MessageType {
+        GREETING,
+        CONFIRMATION
+    }
 
-    constructor(address _wormholeRelayer, address _wormhole) Base(_wormholeRelayer, _wormhole) {}
+    constructor(
+        address _wormholeRelayer,
+        address _wormhole
+    ) Base(_wormholeRelayer, _wormhole) {}
 
-    function quoteCrossChainGreeting(uint16 targetChain, uint256 receiverValue) public view returns (uint256 cost) {
-        (cost,) = wormholeRelayer.quoteEVMDeliveryPrice(targetChain, receiverValue, SENDING_GAS_LIMIT);
+    function quoteCrossChainGreeting(
+        uint16 targetChain,
+        uint256 receiverValue
+    ) public view returns (uint256 cost) {
+        (cost, ) = wormholeRelayer.quoteEVMDeliveryPrice(
+            targetChain,
+            receiverValue,
+            SENDING_GAS_LIMIT
+        );
     }
 
     // receiverValueForSecondDeliveryPayment will be determined in a front-end calculation (by calling quoteConfirmation on the target chain)
     // We recommend baking in a buffer to account for the possibility of the price of targetChain->sourceChain changing during the sourceChain->targetChain delivery
-    function sendCrossChainGreeting(uint16 targetChain, address targetAddress, string memory greeting, uint256 receiverValueForSecondDeliveryPayment) public payable {
-        uint256 cost = quoteCrossChainGreeting(targetChain, receiverValueForSecondDeliveryPayment);
+    function sendCrossChainGreeting(
+        uint16 targetChain,
+        address targetAddress,
+        string memory greeting,
+        uint256 receiverValueForSecondDeliveryPayment
+    ) public payable {
+        uint256 cost = quoteCrossChainGreeting(
+            targetChain,
+            receiverValueForSecondDeliveryPayment
+        );
         require(msg.value == cost);
 
         wormholeRelayer.sendPayloadToEvm{value: cost}(
@@ -38,49 +59,63 @@ contract HelloWormholeConfirmation is Base, IWormholeReceiver {
             receiverValueForSecondDeliveryPayment, // will be used to pay for the confirmation
             SENDING_GAS_LIMIT,
             // we add a refund chain and address as the requester of the cross chain greeting
-            chainId, 
+            chainId,
             msg.sender
         );
     }
 
-    function quoteConfirmation(uint16 targetChain) public view returns (uint256 cost) {
-        (cost,) = wormholeRelayer.quoteEVMDeliveryPrice(targetChain, 0, CONFIRMATION_GAS_LIMIT);
+    function quoteConfirmation(
+        uint16 targetChain
+    ) public view returns (uint256 cost) {
+        (cost, ) = wormholeRelayer.quoteEVMDeliveryPrice(
+            targetChain,
+            0,
+            CONFIRMATION_GAS_LIMIT
+        );
     }
 
     function receiveWormholeMessages(
         bytes memory payload,
         bytes[] memory, // additionalVaas
         bytes32 sourceAddress,
         uint16 sourceChain,
-        bytes32 deliveryHash
+        bytes32 // deliveryHash
     )
         public
         payable
         override
         onlyWormholeRelayer
         isRegisteredSender(sourceChain, sourceAddress)
-        replayProtect(deliveryHash)
     {
         MessageType msgType = abi.decode(payload, (MessageType));
 
-        if(msgType == MessageType.GREETING) {
-            (,string memory greeting, address sender) = abi.decode(payload, (MessageType, string, address));
+        if (msgType == MessageType.GREETING) {
+            (, string memory greeting, address sender) = abi.decode(
+                payload,
+                (MessageType, string, address)
+            );
             latestGreeting = greeting;
             emit GreetingReceived(latestGreeting, sourceChain, sender);
 
             uint256 confirmationCost = quoteConfirmation(sourceChain);
-            require(msg.value >= confirmationCost, "Didn't receive enough value for the second send!");
+            require(
+                msg.value >= confirmationCost,
+                "Didn't receive enough value for the second send!"
+            );
             wormholeRelayer.sendPayloadToEvm{value: confirmationCost}(
-                sourceChain, 
-                fromWormholeFormat(sourceAddress), 
+                sourceChain,
+                fromWormholeFormat(sourceAddress),
                 abi.encode(MessageType.CONFIRMATION, greeting, sender),
                 0,
                 CONFIRMATION_GAS_LIMIT
             );
-        } else if(msgType == MessageType.CONFIRMATION) {
-            (,string memory greeting, address sender) = abi.decode(payload, (MessageType, string, address));
+        } else if (msgType == MessageType.CONFIRMATION) {
+            (, string memory greeting, address sender) = abi.decode(
+                payload,
+                (MessageType, string, address)
+            );
             emit GreetingSuccess(greeting, sender);
             latestConfirmedSentGreeting = greeting;
         }
     }
-}
+}

src/extensions/HelloWormholeProtections.sol

@@ -12,13 +12,26 @@ contract HelloWormholeProtections is Base, IWormholeReceiver {
 
     string public latestGreeting;
 
-    constructor(address _wormholeRelayer, address _wormhole) Base(_wormholeRelayer, _wormhole) {}
+    constructor(
+        address _wormholeRelayer,
+        address _wormhole
+    ) Base(_wormholeRelayer, _wormhole) {}
 
-    function quoteCrossChainGreeting(uint16 targetChain) public view returns (uint256 cost) {
-        (cost,) = wormholeRelayer.quoteEVMDeliveryPrice(targetChain, 0, GAS_LIMIT);
+    function quoteCrossChainGreeting(
+        uint16 targetChain
+    ) public view returns (uint256 cost) {
+        (cost, ) = wormholeRelayer.quoteEVMDeliveryPrice(
+            targetChain,
+            0,
+            GAS_LIMIT
+        );
     }
 
-    function sendCrossChainGreeting(uint16 targetChain, address targetAddress, string memory greeting) public payable {
+    function sendCrossChainGreeting(
+        uint16 targetChain,
+        address targetAddress,
+        string memory greeting
+    ) public payable {
         uint256 cost = quoteCrossChainGreeting(targetChain);
         require(msg.value == cost);
         wormholeRelayer.sendPayloadToEvm{value: cost}(
@@ -35,16 +48,18 @@ contract HelloWormholeProtections is Base, IWormholeReceiver {
         bytes[] memory, // additionalVaas
         bytes32 sourceAddress,
         uint16 sourceChain,
-        bytes32 deliveryHash
+        bytes32 // delivery hash
     )
         public
         payable
         override
         onlyWormholeRelayer
         isRegisteredSender(sourceChain, sourceAddress)
-        replayProtect(deliveryHash)
     {
-        (string memory greeting, address sender) = abi.decode(payload, (string, address));
+        (string memory greeting, address sender) = abi.decode(
+            payload,
+            (string, address)
+        );
         latestGreeting = greeting;
 
         emit GreetingReceived(latestGreeting, sourceChain, sender);