UuidHelper copies the array before modifying it

Previously, the assumption was that the caller owned the array
and didn't care if it was modified, but that assumptions was
not correct

JAVA-3634

Author: jyemin

bson/src/main/org/bson/internal/UuidHelper.java

@@ -21,6 +21,7 @@
 import org.bson.BsonSerializationException;
 import org.bson.UuidRepresentation;
 
+import java.util.Arrays;
 import java.util.UUID;
 
 /**
@@ -85,21 +86,28 @@ public static byte[] encodeUuidToBinary(final UUID uuid, final UuidRepresentatio
         return binaryData;
     }
 
+    // This method will NOT modify the contents of the byte array
     public static UUID decodeBinaryToUuid(final byte[] data, final byte type, final UuidRepresentation uuidRepresentation) {
         if (data.length != 16) {
             throw new BsonSerializationException(String.format("Expected length to be 16, not %d.", data.length));
         }
 
+        byte[] localData = data;
+
         if (type == BsonBinarySubType.UUID_LEGACY.getValue()) {
             switch(uuidRepresentation) {
                 case C_SHARP_LEGACY:
-                    reverseByteArray(data, 0, 4);
-                    reverseByteArray(data, 4, 2);
-                    reverseByteArray(data, 6, 2);
+                    localData = Arrays.copyOf(data, 16);
+
+                    reverseByteArray(localData, 0, 4);
+                    reverseByteArray(localData, 4, 2);
+                    reverseByteArray(localData, 6, 2);
                     break;
                 case JAVA_LEGACY:
-                    reverseByteArray(data, 0, 8);
-                    reverseByteArray(data, 8, 8);
+                    localData = Arrays.copyOf(data, 16);
+
+                    reverseByteArray(localData, 0, 8);
+                    reverseByteArray(localData, 8, 8);
                     break;
                 case PYTHON_LEGACY:
                     break;
@@ -111,7 +119,7 @@ public static UUID decodeBinaryToUuid(final byte[] data, final byte type, final
             }
         }
 
-        return new UUID(readLongFromArrayBigEndian(data, 0), readLongFromArrayBigEndian(data, 8));
+        return new UUID(readLongFromArrayBigEndian(localData, 0), readLongFromArrayBigEndian(localData, 8));
     }
 
     private UuidHelper() {

bson/src/test/unit/org/bson/internal/UuidHelperSpecification.groovy

@@ -26,10 +26,11 @@ class UuidHelperSpecification extends Specification {
     @Unroll
     def 'should decode different types of UUID'() {
         given:
-        byte[] expectedBytes = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
+        byte[] expectedBytes = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16] as byte[]
 
         expect:
         uuid == UuidHelper.decodeBinaryToUuid(expectedBytes, (byte) type, uuidRepresentation)
+        expectedBytes == [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16] as byte[]
 
         where:
         uuid                                                    | type | uuidRepresentation