feat(entropy_contracts): don't call an address if it is an Eoa in reveal callback (#1395)

* don't call an address if it is an Eoa

* fix comment

* update comment

Author: Dev Kalra

target_chains/ethereum/contracts/contracts/entropy/Entropy.sol

@@ -364,8 +364,9 @@ abstract contract Entropy is IEntropy, EntropyState {
     }
 
     // Fulfill a request for a random number and call back the requester. This method validates the provided userRandomness
-    // and provider's revelation against the corresponding commitment in the in-flight request. If both values are validated,
-    // this function calls the requester's entropyCallback method with the sequence number and the random number as arguments.
+    // and provider's revelation against the corresponding commitment in the in-flight request. If both values are validated
+    // and the requestor address is a contract address, this function calls the requester's entropyCallback method with the
+    // sequence number and the random number as arguments. Else if the requestor is an EOA, it won't call it.
     //
     // Note that this function can only be called once per in-flight request. Calling this function deletes the stored
     // request information (so that the contract doesn't use a linear amount of storage in the number of requests).
@@ -405,11 +406,18 @@ abstract contract Entropy is IEntropy, EntropyState {
 
         clearRequest(provider, sequenceNumber);
 
-        IEntropyConsumer(callAddress)._entropyCallback(
-            sequenceNumber,
-            provider,
-            randomNumber
-        );
+        // Check if the callAddress is a contract account.
+        uint len;
+        assembly {
+            len := extcodesize(callAddress)
+        }
+        if (len != 0) {
+            IEntropyConsumer(callAddress)._entropyCallback(
+                sequenceNumber,
+                provider,
+                randomNumber
+            );
+        }
     }
 
     function getProviderInfo(

target_chains/ethereum/contracts/forge-test/Entropy.t.sol

@@ -799,7 +799,7 @@ contract EntropyTest is Test, EntropyTestUtils, EntropyEvents {
         vm.stopPrank();
     }
 
-    function testRequestWithCallbackAndRevealWithCallback() public {
+    function testRequestWithCallbackAndRevealWithCallbackByContract() public {
         bytes32 userRandomNumber = bytes32(uint(42));
         uint fee = random.getFee(provider1);
         EntropyConsumer consumer = new EntropyConsumer(address(random));
@@ -853,6 +853,46 @@ contract EntropyTest is Test, EntropyTestUtils, EntropyEvents {
         assertEq(reqAfterReveal.sequenceNumber, 0);
     }
 
+    function testRequestWithCallbackAndRevealWithCallbackByEoa() public {
+        bytes32 userRandomNumber = bytes32(uint(42));
+        uint fee = random.getFee(provider1);
+        vm.deal(user1, fee);
+        vm.prank(user1);
+        uint64 assignedSequenceNumber = random.requestWithCallback{value: fee}(
+            provider1,
+            userRandomNumber
+        );
+        EntropyStructs.Request memory req = random.getRequest(
+            provider1,
+            assignedSequenceNumber
+        );
+        bytes32 blockHash = bytes32(uint256(0));
+
+        vm.expectEmit(false, false, false, true, address(random));
+        emit RevealedWithCallback(
+            req,
+            userRandomNumber,
+            provider1Proofs[assignedSequenceNumber],
+            random.combineRandomValues(
+                userRandomNumber,
+                provider1Proofs[assignedSequenceNumber],
+                0
+            )
+        );
+        random.revealWithCallback(
+            provider1,
+            assignedSequenceNumber,
+            userRandomNumber,
+            provider1Proofs[assignedSequenceNumber]
+        );
+
+        EntropyStructs.Request memory reqAfterReveal = random.getRequest(
+            provider1,
+            assignedSequenceNumber
+        );
+        assertEq(reqAfterReveal.sequenceNumber, 0);
+    }
+
     function testRequestAndRevealWithCallback() public {
         uint64 sequenceNumber = request(user2, provider1, 42, false);
         assertEq(random.getRequest(provider1, sequenceNumber).requester, user2);

target_chains/ethereum/entropy_sdk/solidity/IEntropy.sol

@@ -51,9 +51,10 @@ interface IEntropy is EntropyEvents {
         bytes32 userRandomNumber
     ) external payable returns (uint64 assignedSequenceNumber);
 
-    // Fulfill a request for a random number. This method validates the provided userRevelation and provider's proof
-    // against the corresponding commitments in the in-flight request. If both values are validated, this function returns
-    // the corresponding random number.
+    // Fulfill a request for a random number and call back the requester. This method validates the provided userRandomness
+    // and provider's revelation against the corresponding commitment in the in-flight request. If both values are validated
+    // and the requestor address is a contract address, this function calls the requester's entropyCallback method with the
+    // sequence number and the random number as arguments. Else if the requestor is an EOA, it won't call it.
     //
     // Note that this function can only be called once per in-flight request. Calling this function deletes the stored
     // request information (so that the contract doesn't use a linear amount of storage in the number of requests).