TransactionDecoder: handle empty bytes (#8997)

* handle empty bytes

* check for empty before getting tx type

Signed-off-by: Sally MacFarlane <macfarla.github@gmail.com>

---------

Signed-off-by: Sally MacFarlane <macfarla.github@gmail.com>

Author: macfarla

ethereum/core/src/main/java/org/hyperledger/besu/ethereum/core/encoding/TransactionDecoder.java

@@ -108,6 +108,9 @@ private static Transaction decodeTypedTransaction(
    */
   public static Transaction decodeOpaqueBytes(
       final Bytes opaqueBytes, final EncodingContext context) {
+    if (opaqueBytes.isEmpty()) {
+      throw new IllegalArgumentException("Empty opaque bytes");
+    }
     var transactionType = getTransactionType(opaqueBytes);
     if (transactionType.isPresent()) {
       return decodeTypedTransaction(opaqueBytes, transactionType.get(), context);
@@ -128,6 +131,9 @@ public static Transaction decodeOpaqueBytes(
    */
   private static Optional<TransactionType> getTransactionType(final Bytes opaqueBytes) {
     try {
+      if (opaqueBytes.isEmpty()) {
+        return Optional.empty();
+      }
       byte transactionTypeByte = opaqueBytes.get(0);
       return Optional.of(TransactionType.of(transactionTypeByte));
     } catch (IllegalArgumentException ex) {

ethereum/core/src/test/java/org/hyperledger/besu/ethereum/core/encoding/TransactionRLPDecoderTest.java

@@ -115,6 +115,13 @@ void shouldDecodeWithHighNonce() {
     assertThat(transaction.getNonce()).isEqualTo(MAX_NONCE - 1);
   }
 
+  @Test
+  void shouldThrowIllegalArgWithEmptyBytes() {
+    assertThatThrownBy(
+            () -> TransactionDecoder.decodeOpaqueBytes(Bytes.EMPTY, EncodingContext.BLOCK_BODY))
+        .isInstanceOf(IllegalArgumentException.class);
+  }
+
   @Test
   void testForAccessListTransaction() {
     BlockDataGenerator gen = new BlockDataGenerator();