fix: recipient rate limited ISM (#4636)

### Description Add recipient restriction to rate limited ISM. This prevents multiple recipients from sharing the same rate limit ISM and denial of service attacks. ### Backward compatibility No ### Testing Unit Tests
hyperlane-xyz · Oct 7, 2024 · bb75eba · bb75eba
1 parent 7dccf80
commit bb75eba
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diff --git a/.changeset/breezy-toys-pay.md b/.changeset/breezy-toys-pay.md
@@ -0,0 +1,5 @@
+---
+'@hyperlane-xyz/core': minor
+---
+
+fix: constrain rate limited ISM to a single message recipient
diff --git a/solidity/contracts/isms/warp-route/RateLimitedIsm.sol b/solidity/contracts/isms/warp-route/RateLimitedIsm.sol
@@ -16,6 +16,8 @@ contract RateLimitedIsm is
     using Message for bytes;
     using TokenMessage for bytes;
 
+    address public immutable recipient;
+
     mapping(bytes32 messageId => bool validated) public messageValidated;
 
     modifier validateMessageOnce(bytes calldata _message) {
@@ -25,14 +27,22 @@ contract RateLimitedIsm is
         _;
     }
 
+    modifier onlyRecipient(bytes calldata _message) {
+        require(_message.recipientAddress() == recipient, "InvalidRecipient");
+        _;
+    }
+
     constructor(
         address _mailbox,
-        uint256 _maxCapacity
-    ) MailboxClient(_mailbox) RateLimited(_maxCapacity) {}
+        uint256 _maxCapacity,
+        address _recipient
+    ) MailboxClient(_mailbox) RateLimited(_maxCapacity) {
+        recipient = _recipient;
+    }
 
     /// @inheritdoc IInterchainSecurityModule
     function moduleType() external pure returns (uint8) {
-        return uint8(IInterchainSecurityModule.Types.UNUSED);
+        return uint8(IInterchainSecurityModule.Types.NULL);
     }
 
     /**
@@ -42,7 +52,12 @@ contract RateLimitedIsm is
     function verify(
         bytes calldata,
         bytes calldata _message
-    ) external validateMessageOnce(_message) returns (bool) {
+    )
+        external
+        onlyRecipient(_message)
+        validateMessageOnce(_message)
+        returns (bool)
+    {
         require(_isDelivered(_message.id()), "InvalidDeliveredMessage");
 
         uint256 newAmount = _message.body().amount();

diff --git a/solidity/test/isms/RateLimitedIsm.t.sol b/solidity/test/isms/RateLimitedIsm.t.sol
@@ -25,18 +25,20 @@ contract RateLimitedIsmTest is Test {
     function setUp() external {
         localMailbox = new TestMailbox(ORIGIN);
 
+        testRecipient = new TestRecipient();
         rateLimitedIsm = new RateLimitedIsm(
             address(localMailbox),
-            MAX_CAPACITY
+            MAX_CAPACITY,
+            address(testRecipient)
         );
-        testRecipient = new TestRecipient();
 
         testRecipient.setInterchainSecurityModule(address(rateLimitedIsm));
     }
 
     function testRateLimitedIsm_revertsIDeliveredFalse(
-        bytes calldata _message
+        uint256 _amount
     ) external {
+        bytes memory _message = _encodeTestMessage(_amount);
         vm.prank(address(localMailbox));
         vm.expectRevert("InvalidDeliveredMessage");
         rateLimitedIsm.verify(bytes(""), _message);
@@ -62,6 +64,21 @@ contract RateLimitedIsmTest is Test {
         rateLimitedIsm.verify(bytes(""), encodedMessage);
     }
 
+    function test_verifyOnlyRecipient(uint128 _amount) external {
+        bytes memory _message = MessageUtils.formatMessage(
+            uint8(3),
+            uint32(1),
+            ORIGIN,
+            WARP_ROUTE_ADDR.addressToBytes32(),
+            ORIGIN,
+            ~address(testRecipient).addressToBytes32(), // bad recipient
+            TokenMessage.format(bytes32(""), _amount, bytes(""))
+        );
+
+        vm.expectRevert("InvalidRecipient");
+        rateLimitedIsm.verify(bytes(""), _message);
+    }
+
     function _encodeTestMessage(
         uint256 _amount
     ) internal view returns (bytes memory) {