executeMessage returns bytes4

Author: Amxx

contracts/crosschain/axelar/AxelarGatewayDestination.sol

@@ -81,13 +81,14 @@ abstract contract AxelarGatewayDestination is IERC7786GatewayDestinationPassive,
         require(getRemoteGateway(source).equal(remoteAccount), "Invalid origin gateway");
 
         // Active mode
-        IERC7786Receiver(receiver.parseAddress()).executeMessage(
+        bytes4 result = IERC7786Receiver(receiver.parseAddress()).executeMessage(
             address(0), // not needed in active mode
             new bytes(0), // not needed in active mode
             source,
             sender,
             payload,
             attributes
         );
+        require(result == IERC7786Receiver.executeMessage.selector, "Receiver execution failed");
     }
 }

contracts/crosschain/interfaces/draft-IERC7786.sol

@@ -87,5 +87,5 @@ interface IERC7786Receiver {
         string calldata sender,
         bytes calldata payload,
         bytes[] calldata attributes
-    ) external payable;
+    ) external payable returns (bytes4);
 }

contracts/crosschain/mocks/ERC7786GatewayMock.sol

@@ -38,7 +38,17 @@ contract ERC7786GatewayMock is IERC7786GatewaySource, IERC7786GatewayDestination
 
         if (_activeMode) {
             address target = Strings.parseAddress(receiver);
-            IERC7786Receiver(target).executeMessage(address(this), new bytes(0), source, sender, payload, attributes);
+            require(
+                IERC7786Receiver(target).executeMessage(
+                    address(this),
+                    new bytes(0),
+                    source,
+                    sender,
+                    payload,
+                    attributes
+                ) == IERC7786Receiver.executeMessage.selector,
+                "Receiver error"
+            );
         } else {
             _outbox.set(uint256(keccak256(abi.encode(source, sender, receiver, payload, attributes))));
         }

contracts/crosschain/mocks/ERC7786ReceiverInvalidMock.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import {IERC7786Receiver} from "../interfaces/draft-IERC7786.sol";
+
+contract ERC7786ReceiverInvalidMock is IERC7786Receiver {
+    function executeMessage(
+        address,
+        bytes calldata,
+        string calldata,
+        string calldata,
+        bytes calldata,
+        bytes[] calldata
+    ) public payable virtual returns (bytes4) {
+        return 0xffffffff;
+    }
+}

contracts/crosschain/utils/draft-ERC7786Receiver.sol

@@ -28,7 +28,7 @@ abstract contract ERC7786Receiver is IERC7786Receiver {
         string calldata sender,
         bytes calldata payload,
         bytes[] calldata attributes
-    ) public payable virtual {
+    ) public payable virtual returns (bytes4) {
         if (_isKnownGateway(msg.sender)) {
             // Active mode
             // no extra check
@@ -46,6 +46,7 @@ abstract contract ERC7786Receiver is IERC7786Receiver {
             revert ERC7786ReceiverInvalidGateway(gateway);
         }
         _processMessage(gateway, source, sender, payload, attributes);
+        return IERC7786Receiver.executeMessage.selector;
     }
 
     /// @dev Virtual getter that returns whether an address in a valid ERC-7786 gateway.

test/crosschain/axelar/AxelarGateway.test.js

@@ -12,17 +12,18 @@ async function fixture() {
   const CAIP2 = `eip155:${chainId}`;
   const asCAIP10 = account => `eip155:${chainId}:${getAddress(account)}`;
 
-  const axelar     = await ethers.deployContract('$AxelarGatewayMock');
-  const srcGateway = await ethers.deployContract('$AxelarGatewaySource', [ owner, axelar ]);
-  const dstGateway = await ethers.deployContract('$AxelarGatewayDestination', [ owner, axelar, axelar ]);
-  const receiver   = await ethers.deployContract('$ERC7786ReceiverMock', [ dstGateway ]);
+  const axelar          = await ethers.deployContract('$AxelarGatewayMock');
+  const srcGateway      = await ethers.deployContract('$AxelarGatewaySource', [ owner, axelar ]);
+  const dstGateway      = await ethers.deployContract('$AxelarGatewayDestination', [ owner, axelar, axelar ]);
+  const receiver        = await ethers.deployContract('$ERC7786ReceiverMock', [ dstGateway ]);
+  const invalidReceiver = await ethers.deployContract('$ERC7786ReceiverInvalidMock');
 
   await srcGateway.registerChainEquivalence(CAIP2, 'local');
   await dstGateway.registerChainEquivalence(CAIP2, 'local');
   await srcGateway.registerRemoteGateway(CAIP2, getAddress(dstGateway));
   await dstGateway.registerRemoteGateway(CAIP2, getAddress(srcGateway));
 
-  return { owner, sender, accounts, CAIP2, asCAIP10, axelar, srcGateway, dstGateway, receiver };
+  return { owner, sender, accounts, CAIP2, asCAIP10, axelar, srcGateway, dstGateway, receiver, invalidReceiver };
 }
 
 describe('AxelarGateway', function () {
@@ -31,13 +32,13 @@ describe('AxelarGateway', function () {
   });
 
   it('initial setup', async function () {
-    expect(await this.srcGateway.localGateway()).to.equal(this.axelar);
-    expect(await this.srcGateway.getEquivalentChain(this.CAIP2)).to.equal('local');
-    expect(await this.srcGateway.getRemoteGateway(this.CAIP2)).to.equal(getAddress(this.dstGateway));
+    expect(this.srcGateway.localGateway()).to.eventually.equal(this.axelar);
+    expect(this.srcGateway.getEquivalentChain(this.CAIP2)).to.eventually.equal('local');
+    expect(this.srcGateway.getRemoteGateway(this.CAIP2)).to.eventually.equal(getAddress(this.dstGateway));
 
-    expect(await this.dstGateway.localGateway()).to.equal(this.axelar);
-    expect(await this.dstGateway.getEquivalentChain(this.CAIP2)).to.equal('local');
-    expect(await this.dstGateway.getRemoteGateway(this.CAIP2)).to.equal(getAddress(this.srcGateway));
+    expect(this.dstGateway.localGateway()).to.eventually.equal(this.axelar);
+    expect(this.dstGateway.getEquivalentChain(this.CAIP2)).to.eventually.equal('local');
+    expect(this.dstGateway.getRemoteGateway(this.CAIP2)).to.eventually.equal(getAddress(this.srcGateway));
   });
 
   describe('Active mode', function () {
@@ -52,13 +53,32 @@ describe('AxelarGateway', function () {
       const attributes = [];
       const package    = ethers.AbiCoder.defaultAbiCoder().encode([ 'string', 'string', 'bytes', 'bytes[]' ], [ getAddress(this.sender), getAddress(this.receiver), payload, attributes ]);
 
-      const tx = await this.srcGateway.connect(this.sender).sendMessage(this.CAIP2, getAddress(this.receiver), payload, attributes);
-      await expect(tx)
+      await expect(this.srcGateway.connect(this.sender).sendMessage(this.CAIP2, getAddress(this.receiver), payload, attributes))
         .to.emit(this.srcGateway, 'MessagePosted').withArgs(ethers.ZeroHash, srcCAIP10, dstCAIP10, payload, attributes)
         .to.emit(this.axelar, 'ContractCall').withArgs(this.srcGateway, 'local', getAddress(this.dstGateway), ethers.keccak256(package), package)
         .to.emit(this.axelar, 'ContractCallExecuted').withArgs(anyValue)
         .to.emit(this.receiver, 'MessageReceived').withArgs(ethers.ZeroAddress, this.CAIP2, getAddress(this.sender), payload, attributes);
     });
+
+    it('invalid receiver - bad return value', async function () {
+      await expect(this.srcGateway.connect(this.sender).sendMessage(
+        this.CAIP2,
+        getAddress(this.invalidReceiver),
+        ethers.randomBytes(128),
+        [],
+      ))
+        .to.be.revertedWith('Receiver execution failed');
+    });
+
+    it('invalid receiver - EOA', async function () {
+      await expect(this.srcGateway.connect(this.sender).sendMessage(
+        this.CAIP2,
+        getAddress(this.accounts[0]),
+        ethers.randomBytes(128),
+        [],
+      ))
+        .to.be.revertedWithoutReason();
+    });
   });
 
   describe('Passive mode', function () {