address comment

solidity/contracts/libs/FraudMessage.sol

@@ -27,25 +27,44 @@ struct Attribution {
 }
 
 library FraudMessage {
+    uint8 public constant SIGNER_OFFSET = 0;
+    uint8 public constant MERKLE_TREE_OFFSET = 32;
+    uint8 public constant DIGEST_OFFSET = 64;
+    uint8 public constant FRAUD_TYPE_OFFSET = 96;
+    uint8 public constant TIMESTAMP_OFFSET = 97;
+    uint8 public constant MESSAGE_LENGTH = 103;
+
     function encode(
         bytes32 signer,
         bytes32 merkleTree,
         bytes32 digest,
         Attribution memory attribution
     ) internal pure returns (bytes memory) {
         return
-            abi.encode(
+            abi.encodePacked(
                 signer,
                 merkleTree,
                 digest,
-                attribution.fraudType,
+                uint8(attribution.fraudType),
                 attribution.timestamp
             );
     }
 
     function decode(
-        bytes memory _message
+        bytes calldata _message
     ) internal pure returns (bytes32, bytes32, bytes32, Attribution memory) {
-        return abi.decode(_message, (bytes32, bytes32, bytes32, Attribution));
+        require(_message.length == MESSAGE_LENGTH, "Invalid message length");
+
+        bytes32 signer = bytes32(_message[SIGNER_OFFSET:MERKLE_TREE_OFFSET]);
+        bytes32 merkleTree = bytes32(
+            _message[MERKLE_TREE_OFFSET:DIGEST_OFFSET]
+        );
+        bytes32 digest = bytes32(_message[DIGEST_OFFSET:FRAUD_TYPE_OFFSET]);
+        FraudType fraudType = FraudType(uint8(_message[FRAUD_TYPE_OFFSET]));
+        uint48 timestamp = uint48(
+            bytes6(_message[TIMESTAMP_OFFSET:MESSAGE_LENGTH])
+        );
+
+        return (signer, merkleTree, digest, Attribution(fraudType, timestamp));
     }
 }

solidity/contracts/middleware/FraudProofRouter.sol

@@ -113,7 +113,7 @@ contract FraudProofRouter is GasRouter {
         bytes32,
         /*_sender*/
         bytes calldata _message
-    ) internal override onlyMailbox {
+    ) internal override {
         (
             bytes32 signer,
             bytes32 merkleTree,

solidity/remappings.txt

@@ -1,7 +1,7 @@
-@arbitrum=./node_modules/@arbitrum
-@eth-optimism=./node_modules/@eth-optimism
-@layerzerolabs=./node_modules/@layerzerolabs
-@openzeppelin=./node_modules/@openzeppelin
+@arbitrum=../node_modules/@arbitrum
+@eth-optimism=../node_modules/@eth-optimism
+@layerzerolabs=../node_modules/@layerzerolabs
+@openzeppelin=../node_modules/@openzeppelin
 ds-test/=lib/forge-std/lib/ds-test/src/
 forge-std/=lib/forge-std/src/
 fx-portal/=lib/fx-portal/

solidity/test/FraudProofRouter.t.sol

@@ -3,7 +3,7 @@ pragma solidity >=0.8.0;
 
 import {Test} from "forge-std/Test.sol";
 
-import {FraudType, Attribution} from "../contracts/libs/FraudMessage.sol";
+import {FraudType} from "../contracts/libs/FraudMessage.sol";
 import {TypeCasts} from "../contracts/libs/TypeCasts.sol";
 import {TestAttributeCheckpointFraud} from "../contracts/test/TestAttributeCheckpointFraud.sol";
 import {FraudProofRouter} from "../contracts/middleware/FraudProofRouter.sol";
@@ -63,29 +63,38 @@ contract FraudProofRouterTest is Test {
         new FraudProofRouter(address(localMailbox), address(0));
     }
 
-    function test_sendFraudProof() public {
-        FraudType fraudType = FraudType.Whitelist;
+    function test_sendFraudProof(
+        address _signer,
+        bytes32 _digest,
+        bytes32 _merkleTree,
+        uint8 _fraudType,
+        uint48 _timestamp
+    ) public {
+        vm.assume(_fraudType <= uint8(FraudType.Root));
+        vm.assume(_timestamp > 0);
+        vm.warp(_timestamp);
+        FraudType fraudTypeEnum = FraudType(_fraudType);
 
-        testAcf.mockSetAttribution(SIGNER, DIGEST, fraudType);
+        testAcf.mockSetAttribution(_signer, _digest, fraudTypeEnum);
 
         originFpr.sendFraudProof(
             DESTINATION_DOMAIN,
-            SIGNER,
-            TypeCasts.addressToBytes32(address(testMerkleHook)),
-            DIGEST
+            _signer,
+            _merkleTree,
+            _digest
         );
 
         remoteMailbox.processNextInboundMessage();
 
         (FraudType actualFraudType, uint48 actualTimestamp) = remoteFpr
             .fraudAttributions(
                 LOCAL_DOMAIN,
-                SIGNER.addressToBytes32(),
-                address(testMerkleHook).addressToBytes32(),
-                DIGEST
+                _signer.addressToBytes32(),
+                _merkleTree,
+                _digest
             );
 
-        assert(actualFraudType == fraudType);
+        assert(actualFraudType == fraudTypeEnum);
         assertEq(actualTimestamp, block.timestamp);
     }