java: Fix incremental mac finalization. Again.

Author: moiseev-signal

RELEASE_NOTES.md

@@ -1,3 +1,5 @@
 v0.76.2
 
 - Java: Fix lifetime management for bridged objects used with async functions; previously there was a window where they could get prematurely deallocated, leading to undefined behavior.
+
+- Java: Simplify and fix the finalization of incremental mac streams.

java/shared/java/org/signal/libsignal/internal/NativeHandleGuard.java

@@ -88,6 +88,11 @@ protected void finalize() {
     }
   }
 
+  // A note on synchronization.
+  //
+  // close is synchronized to eliminate the race between it and finalize.
+  //
+  // All in the name of calling release exactly once.
   public abstract static class CloseableOwner extends SimpleOwner implements AutoCloseable {
     private boolean isClosed = false;
 
@@ -96,7 +101,7 @@ protected CloseableOwner(long nativeHandle) {
     }
 
     @Override
-    public void close() {
+    public synchronized void close() {
       if (isClosed) {
         return;
       }

java/shared/java/org/signal/libsignal/protocol/incrementalmac/IncrementalMacInputStream.java

@@ -94,7 +94,7 @@ public int read(byte[] bytes, int offset, int length) throws IOException {
   }
 
   @Override
-  public synchronized void close() throws IOException {
+  public void close() throws IOException {
     if (this.closed) {
       return;
     }
@@ -103,16 +103,6 @@ public synchronized void close() throws IOException {
     this.handleOwner.close();
   }
 
-  @Override
-  @SuppressWarnings("deprecation")
-  protected void finalize() throws Throwable {
-    try {
-      close();
-    } finally {
-      super.finalize();
-    }
-  }
-
   // Read implementation for the READ_FROM_INPUT state.
   // In it, we are filling the currentChunk reading from the input channel.
   // Once there is a full chunk worth of data (or if we have reached the end of

java/shared/java/org/signal/libsignal/protocol/incrementalmac/IncrementalMacOutputStream.java

@@ -65,7 +65,7 @@ public void flush() throws IOException {
   }
 
   @Override
-  public synchronized void close() throws IOException {
+  public void close() throws IOException {
     if (this.closed) {
       return;
     }
@@ -82,14 +82,4 @@ public synchronized void close() throws IOException {
     // problems on Android
     this.digestStream.close();
   }
-
-  @Override
-  @SuppressWarnings("deprecation")
-  protected void finalize() throws Throwable {
-    try {
-      close();
-    } finally {
-      super.finalize();
-    }
-  }
 }