[1404] Fixed NPE when executing eth_estimateGas with privacy enabled. (#1424)

* [1404] Fixed NPE when executing eth_estimateGas with privacy enabled.

Signed-off-by: Mark Terry <mark.terry@consensys.net>

CHANGELOG.md

@@ -17,6 +17,7 @@ Hyperledger Besu is moving its versioning scheme to [CalVer](https://calver.org/
 ### Bug Fixes
 
 * Log block import rejection reasons at "INFO" level.  Bug [#1412](https://github.com/hyperledger/besu/issues/1412)
+* Fixed NPE when executing `eth_estimateGas` with privacy enabled.  Bug [#1404](https://github.com/hyperledger/besu/issues/1404)
 
 #### Previously identified known issues
 

ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/precompiles/privacy/OnChainPrivacyPrecompiledContract.java

@@ -102,7 +102,7 @@ public class OnChainPrivacyPrecompiledContract extends PrivacyPrecompiledContrac
   @Override
   public Bytes compute(final Bytes input, final MessageFrame messageFrame) {
 
-    if (isMining(messageFrame)) {
+    if (skipContractExecution(messageFrame)) {
       return Bytes.EMPTY;
     }
 

ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/precompiles/privacy/PrivacyPrecompiledContract.java

@@ -102,7 +102,7 @@ public class PrivacyPrecompiledContract extends AbstractPrecompiledContract {
   @Override
   public Bytes compute(final Bytes input, final MessageFrame messageFrame) {
 
-    if (isMining(messageFrame)) {
+    if (skipContractExecution(messageFrame)) {
       return Bytes.EMPTY;
     }
 
@@ -242,6 +242,17 @@ public class PrivacyPrecompiledContract extends AbstractPrecompiledContract {
     return receiveResponse;
   }
 
+  boolean skipContractExecution(final MessageFrame messageFrame) {
+    return isSimulatingPMT(messageFrame) || isMining(messageFrame);
+  }
+
+  boolean isSimulatingPMT(final MessageFrame messageFrame) {
+    // If there's no PrivateMetadataUpdater, the precompile has not been called through the
+    // PrivacyBlockProcessor. This indicates the PMT is being simulated and execution of the
+    // precompile is not required.
+    return messageFrame.getPrivateMetadataUpdater() == null;
+  }
+
   boolean isMining(final MessageFrame messageFrame) {
     boolean isMining = false;
     final ProcessableBlockHeader currentBlockHeader = messageFrame.getBlockHeader();

ethereum/core/src/test/java/org/hyperledger/besu/ethereum/mainnet/precompiles/privacy/PrivacyPrecompiledContractTest.java

@@ -303,6 +303,19 @@ public class PrivacyPrecompiledContractTest {
     assertThat(actual).isEqualTo(Bytes.EMPTY);
   }
 
+  @Test
+  public void testSimulatedPublicTransactionIsSkipped() {
+    final PrivacyPrecompiledContract emptyContract =
+        new PrivacyPrecompiledContract(null, null, null, null);
+
+    // A simulated public transaction doesn't contain a PrivateMetadataUpdater
+    final MessageFrame frame = mock(MessageFrame.class);
+    when(frame.getPrivateMetadataUpdater()).thenReturn(null);
+
+    final Bytes result = emptyContract.compute(null, frame);
+    assertThat(result).isEqualTo(Bytes.EMPTY);
+  }
+
   private byte[] convertPrivateTransactionToBytes(final PrivateTransaction privateTransaction) {
     final BytesValueRLPOutput bytesValueRLPOutput = new BytesValueRLPOutput();
     privateTransaction.writeTo(bytesValueRLPOutput);