From cc42af4c3090da77516ba56ba1fb530ca22c51e3 Mon Sep 17 00:00:00 2001
From: Ferran Borreguero <ferranbt@protonmail.com>
Date: Thu, 28 Mar 2024 14:44:53 +0000
Subject: [PATCH] Do not error on state change for transient objects (#229)

---
 internal/ethapi/api.go                 | 13 +++++++++++--
 suave/e2e/workflow_test.go             |  6 +++++-
 suave/sol/standard_peekers/example.sol | 14 ++++++++++++++
 3 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index 810fff12d..ef9926a17 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -1948,6 +1948,7 @@ func (s *TransactionAPI) SendRawTransaction(ctx context.Context, input hexutil.B
 }
 
 type mevmStateLogger struct {
+	suappAddr      common.Address
 	hasStoredState bool
 }
 
@@ -1955,7 +1956,13 @@ func (m *mevmStateLogger) CaptureStart(env *vm.EVM, from common.Address, to comm
 }
 
 func (m *mevmStateLogger) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
-	if op == vm.SSTORE {
+	if op == vm.SSTORE && scope.Contract.Address() == m.suappAddr {
+		// Modify the state storage is a nil operation in a Suapp, since the changes are not synced up with the
+		// consensus state. It is confusing an a bad UX for users that modify the state and nothing happens.
+		// Thus, we capture the state storage modification and return an error.
+		// However, we do leverage this volatile state to create temporal Contracts that act as Objects in the traditional sense.
+		// Only valid during the scope of the Confidential request. Thus, we need to differentiate between the two state changes:
+		// the ones performed on the Suapp itself (confusing for users) and the ones performed on temporal Contracts.
 		m.hasStoredState = true
 	}
 }
@@ -1995,7 +2002,9 @@ func runMEVM(ctx context.Context, b Backend, state *state.StateDB, header *types
 		return nil, nil, nil, err
 	}
 
-	storageAccessTracer := &mevmStateLogger{}
+	storageAccessTracer := &mevmStateLogger{
+		suappAddr: *msg.To,
+	}
 
 	blockCtx := core.NewEVMBlockContext(header, NewChainContext(ctx, b), nil)
 	suaveCtx := b.SuaveContext(tx, confidentialRequest)
diff --git a/suave/e2e/workflow_test.go b/suave/e2e/workflow_test.go
index 9d4f05283..7b2f218bc 100644
--- a/suave/e2e/workflow_test.go
+++ b/suave/e2e/workflow_test.go
@@ -1168,9 +1168,13 @@ func TestE2EOnChainStateTransition(t *testing.T) {
 	contractAddr := common.Address{0x3}
 	sourceContract := sdk.GetContract(contractAddr, exampleCallSourceContract.Abi, clt)
 
-	// a confidential request cannot make a state change
+	// a confidential request cannot make a state change in the Suapp
 	_, err := sourceContract.SendTransaction("ilegalStateTransition", []interface{}{}, nil)
 	require.Error(t, err)
+
+	// a confidential request can create a new "temporal" contract and change the state there
+	_, err = sourceContract.SendTransaction("offchainCreateNewContract", []interface{}{}, nil)
+	require.NoError(t, err)
 }
 
 func TestE2EConsoleLog(t *testing.T) {
diff --git a/suave/sol/standard_peekers/example.sol b/suave/sol/standard_peekers/example.sol
index 700544c12..bbe8cfca6 100644
--- a/suave/sol/standard_peekers/example.sol
+++ b/suave/sol/standard_peekers/example.sol
@@ -89,6 +89,20 @@ contract ExampleEthCallSource {
     function offchain() public pure returns (bytes memory) {
         return abi.encodeWithSelector(this.onchain.selector);
     }
+
+    function offchainCreateNewContract() public returns (bytes memory) {
+        Other o = new Other();
+        o.setValue(10);
+        return abi.encodeWithSelector(this.onchain.selector);
+    }
+}
+
+contract Other {
+    uint256 value;
+
+    function setValue(uint256 _value) public {
+        value = _value;
+    }
 }
 
 contract ExampleEthCallTarget {