core: vm: create new oracle contract instance in each call (#251)

Since the VM might be called from different source (downloader, RPC,
etc.). We need to make the call state separate. Modify the calling
sequence so a new oracle contract instance is used on each run.

3 files changed, 16 insertions, 6 deletions

diff --git a/core/vm/evm.go b/core/vm/evm.go
index 6b2844020..baf3a0ac9 100644
--- a/core/vm/evm.go
+++ b/core/vm/evm.go
@@ -49,7 +49,7 @@ type (
 func run(evm *EVM, contract *Contract, input []byte, readOnly bool) ([]byte, error) {
 	if contract.CodeAddr != nil {
 		if o := OracleContracts[*contract.CodeAddr]; o != nil {
-			return RunOracleContract(o, evm, input, contract)
+			return RunOracleContract(o(), evm, input, contract)
 		}
 		precompiles := PrecompiledContractsHomestead
 		if evm.ChainConfig().IsByzantium(evm.BlockNumber) {
diff --git a/core/vm/oracle.go b/core/vm/oracle.go
index 81755cd9b..0d4c10d9e 100644
--- a/core/vm/oracle.go
+++ b/core/vm/oracle.go
@@ -38,9 +38,11 @@ type OracleContract interface {
 }
 
 // A map representing available system oracle contracts.
-var OracleContracts = map[common.Address]OracleContract{
-	GovernanceContractAddress: &GovernanceContract{
-		coreDKGUtils: &defaultCoreDKGUtils{},
+var OracleContracts = map[common.Address]func() OracleContract{
+	GovernanceContractAddress: func() OracleContract {
+		return &GovernanceContract{
+			coreDKGUtils: &defaultCoreDKGUtils{},
+		}
 	},
 }
 
diff --git a/core/vm/oracle_contracts_test.go b/core/vm/oracle_contracts_test.go
index f8f327a68..0b8b7b4f7 100644
--- a/core/vm/oracle_contracts_test.go
+++ b/core/vm/oracle_contracts_test.go
@@ -195,7 +195,11 @@ func (g *OracleContractsTestSuite) SetupTest() {
 }
 
 func (g *OracleContractsTestSuite) TearDownTest() {
-	OracleContracts[GovernanceContractAddress].(*GovernanceContract).coreDKGUtils = &defaultCoreDKGUtils{}
+	OracleContracts[GovernanceContractAddress] = func() OracleContract {
+		return &GovernanceContract{
+			coreDKGUtils: &defaultCoreDKGUtils{},
+		}
+	}
 }
 
 func (g *OracleContractsTestSuite) newPrefundAccount() (*ecdsa.PrivateKey, common.Address) {
@@ -936,7 +940,11 @@ func (g *OracleContractsTestSuite) TestResetDKG() {
 	mock := &testCoreMock{
 		tsigReturn: true,
 	}
-	OracleContracts[GovernanceContractAddress].(*GovernanceContract).coreDKGUtils = mock
+	OracleContracts[GovernanceContractAddress] = func() OracleContract {
+		return &GovernanceContract{
+			coreDKGUtils: mock,
+		}
+	}
 
 	// Fill data for previous rounds.
 	roundHeight := int64(g.config.RoundLength)