Make Record serializable again

ibauersachs · ibauersachs · commit 05e0f0ad0619 · 2021-12-26T16:20:23.000+01:00
Instead of relying on the unstable default Java serialization of each record type, this uses a proxy object. The proxy object only contains the DNS wire data of a record, which is guaranteed to be stable. This avoids all concerns about compatibility when Record classes evolve and with inheritance. Closes #132 See #114
diff --git a/src/main/java/org/xbill/DNS/Record.java b/src/main/java/org/xbill/DNS/Record.java
@@ -5,9 +5,14 @@
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.io.InvalidObjectException;
+import java.io.ObjectInputStream;
+import java.io.ObjectStreamException;
+import java.io.Serializable;
 import java.text.DecimalFormat;
 import java.util.Arrays;
 import java.util.function.Supplier;
+import lombok.extern.slf4j.Slf4j;
 import org.xbill.DNS.utils.base16;
 
 /**
@@ -16,9 +21,11 @@
  *
  * @author Brian Wellington
  */
-public abstract class Record implements Cloneable, Comparable<Record> {
+@Slf4j
+public abstract class Record implements Cloneable, Comparable<Record>, Serializable {
   protected Name name;
-  protected int type, dclass;
+  protected int type;
+  protected int dclass;
   protected long ttl;
 
   private static final DecimalFormat byteFormat = new DecimalFormat();
@@ -27,6 +34,23 @@ public abstract class Record implements Cloneable, Comparable<Record> {
     byteFormat.setMinimumIntegerDigits(3);
   }
 
+  private static class RecordSerializationProxy implements Serializable {
+    private static final long serialVersionUID = 1434159920070152561L;
+    private final byte[] wireData;
+
+    RecordSerializationProxy(Record r) {
+      wireData = r.toWire(Section.ANSWER);
+    }
+
+    protected Object readResolve() throws ObjectStreamException {
+      try {
+        return Record.fromWire(wireData, Section.ANSWER);
+      } catch (IOException e) {
+        throw new InvalidObjectException(e.getMessage());
+      }
+    }
+  }
+
   protected Record() {}
 
   /** @since 3.1 */
@@ -43,6 +67,15 @@ protected Record(Name name, int type, int dclass, long ttl) {
     this.ttl = ttl;
   }
 
+  Object writeReplace() {
+    log.trace("Creating proxy object for serialization");
+    return new RecordSerializationProxy(this);
+  }
+
+  private void readObject(ObjectInputStream ois) throws InvalidObjectException {
+    throw new InvalidObjectException("Use RecordSerializationProxy");
+  }
+
   private static Record getEmptyRecord(Name name, int type, int dclass, long ttl, boolean hasData) {
     Record rec;
     if (hasData) {
@@ -169,7 +202,8 @@ public static Record newRecord(Name name, int type, int dclass) {
   }
 
   static Record fromWire(DNSInput in, int section, boolean isUpdate) throws IOException {
-    int type, dclass;
+    int type;
+    int dclass;
     long ttl;
     int length;
     Name name;
@@ -404,12 +438,7 @@ protected static String byteArrayToString(byte[] array, boolean quote) {
 
   /** Converts a byte array into the unknown RR format. */
   protected static String unknownToString(byte[] data) {
-    StringBuilder sb = new StringBuilder();
-    sb.append("\\# ");
-    sb.append(data.length);
-    sb.append(" ");
-    sb.append(base16.toString(data));
-    return sb.toString();
+    return "\\# " + data.length + " " + base16.toString(data);
   }
 
   /**
@@ -453,8 +482,7 @@ public static Record fromString(
     rec.rdataFromString(st, origin);
     t = st.get();
     if (t.type != Tokenizer.EOL && t.type != Tokenizer.EOF) {
-      throw st.exception(
-          "unexpected tokens at end of record (wanted EOL/EOF, got " + t.toString() + ")");
+      throw st.exception("unexpected tokens at end of record (wanted EOL/EOF, got " + t + ")");
     }
     return rec;
   }
diff --git a/src/test/java/org/xbill/DNS/ARecordTest.java b/src/test/java/org/xbill/DNS/ARecordTest.java
@@ -40,7 +40,11 @@
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
 import org.junit.jupiter.api.BeforeEach;
@@ -135,4 +139,19 @@ void rrToWire() {
     ar.rrToWire(dout, null, false);
     assertArrayEquals(m_addr_bytes, dout.toByteArray());
   }
+
+  @Test
+  void testSerializable() throws IOException, ClassNotFoundException {
+    try (ByteArrayOutputStream bos = new ByteArrayOutputStream()) {
+      try (ObjectOutputStream oos = new ObjectOutputStream(bos)) {
+        ARecord expected = new ARecord(Name.root, DClass.IN, 60, m_addr);
+        oos.writeObject(expected);
+        try (ObjectInputStream ois =
+            new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray()))) {
+          Record actual = (Record) ois.readObject();
+          assertEquals(expected, actual);
+        }
+      }
+    }
+  }
 }
diff --git a/src/test/java/org/xbill/DNS/RecordTest.java b/src/test/java/org/xbill/DNS/RecordTest.java
@@ -552,7 +552,6 @@ void fromString_invalid() throws IOException {
     int t = Type.A;
     int d = DClass.IN;
     int ttl = 0xABE99;
-    InetAddress addr = InetAddress.getByName("191.234.43.10");
 
     assertThrows(
         RelativeNameException.class,
