Close the ApplicationExitInfo trace stream in Crashlytics NDK

firebase-crashlytics-ndk/CHANGELOG.md

@@ -1,5 +1,9 @@
 # Unreleased
 
+- [fixed] Fixed a file descriptor leak when reading the native crash trace from
+  `ApplicationExitInfo`, which could trigger a StrictMode `CloseGuard` violation on the app start
+  following a native crash. (#8510)
+
 # 20.1.0
 
 - [changed] Updated `firebase-crashlytics` dependency to 20.1.0

firebase-crashlytics-ndk/src/main/java/com/google/firebase/crashlytics/ndk/CrashpadController.java

@@ -257,11 +257,15 @@ private static CrashlyticsReport.ApplicationExitInfo convertApplicationExitInfoT
         .build();
   }
 
+  @VisibleForTesting
   @RequiresApi(api = Build.VERSION_CODES.S)
-  private static String getTraceFileFromApplicationExitInfo(
-      ApplicationExitInfo applicationExitInfo) {
-    try {
-      return convertInputStreamToString(applicationExitInfo.getTraceInputStream());
+  static String getTraceFileFromApplicationExitInfo(ApplicationExitInfo applicationExitInfo) {
+    // The stream returned by getTraceInputStream() wraps a ParcelFileDescriptor that is only
+    // released when the stream is closed. Leaving it open leaks the file descriptor until the
+    // finalizer runs, which StrictMode's detectLeakedClosableObjects() reports as a CloseGuard
+    // violation. try-with-resources is null safe, so a missing trace still returns null.
+    try (InputStream traceInputStream = applicationExitInfo.getTraceInputStream()) {
+      return convertInputStreamToString(traceInputStream);
     } catch (IOException e) {
       Logger.getLogger().w("Failed to get input stream from ApplicationExitInfo");
     }

firebase-crashlytics-ndk/src/test/java/com/google/firebase/crashlytics/ndk/CrashpadControllerRobolectricTest.java

@@ -0,0 +1,172 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.crashlytics.ndk;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import android.app.ApplicationExitInfo;
+import android.os.Build.VERSION_CODES;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+import java.util.zip.GZIPInputStream;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+
+/**
+ * Tests that the trace stream taken from an {@link ApplicationExitInfo} is always released.
+ *
+ * <p>The stream returned by {@link ApplicationExitInfo#getTraceInputStream()} wraps a {@code
+ * ParcelFileDescriptor}, so failing to close it leaks a file descriptor until finalization and trips
+ * StrictMode's {@code detectLeakedClosableObjects()}. See
+ * https://github.com/firebase/firebase-android-sdk/issues/8510.
+ */
+@RunWith(RobolectricTestRunner.class)
+@Config(sdk = VERSION_CODES.TIRAMISU)
+public class CrashpadControllerRobolectricTest {
+
+  private static final String TRACE = "----- pid 1234 -----\nnative crash trace\n----- end -----\n";
+
+  @Test
+  public void getTraceFileFromApplicationExitInfo_closesTraceInputStream() throws IOException {
+    CloseTrackingInputStream traceInputStream =
+        new CloseTrackingInputStream(
+            new ByteArrayInputStream(TRACE.getBytes(StandardCharsets.UTF_8)));
+    ApplicationExitInfo applicationExitInfo = mock(ApplicationExitInfo.class);
+    when(applicationExitInfo.getTraceInputStream()).thenReturn(traceInputStream);
+
+    String traceFile = CrashpadController.getTraceFileFromApplicationExitInfo(applicationExitInfo);
+
+    assertTrue("The trace input stream must be closed.", traceInputStream.isClosed());
+    assertEquals(TRACE, gunzipAndDecode(traceFile));
+  }
+
+  @Test
+  public void getTraceFileFromApplicationExitInfo_closesTraceInputStreamWhenReadFails()
+      throws IOException {
+    ThrowingInputStream traceInputStream = new ThrowingInputStream();
+    ApplicationExitInfo applicationExitInfo = mock(ApplicationExitInfo.class);
+    when(applicationExitInfo.getTraceInputStream()).thenReturn(traceInputStream);
+
+    String traceFile = CrashpadController.getTraceFileFromApplicationExitInfo(applicationExitInfo);
+
+    assertNull(traceFile);
+    assertTrue(
+        "The trace input stream must be closed even when reading it fails.",
+        traceInputStream.isClosed());
+  }
+
+  @Test
+  public void getTraceFileFromApplicationExitInfo_nullTraceInputStream_returnsNull()
+      throws IOException {
+    ApplicationExitInfo applicationExitInfo = mock(ApplicationExitInfo.class);
+    when(applicationExitInfo.getTraceInputStream()).thenReturn(null);
+
+    assertNull(CrashpadController.getTraceFileFromApplicationExitInfo(applicationExitInfo));
+  }
+
+  @Test
+  public void getTraceFileFromApplicationExitInfo_traceInputStreamThrows_returnsNull()
+      throws IOException {
+    ApplicationExitInfo applicationExitInfo = mock(ApplicationExitInfo.class);
+    when(applicationExitInfo.getTraceInputStream()).thenThrow(new IOException("no trace"));
+
+    assertNull(CrashpadController.getTraceFileFromApplicationExitInfo(applicationExitInfo));
+  }
+
+  /** The caller owns the stream, so this helper must keep leaving it open. */
+  @Test
+  public void convertInputStreamToString_roundTripsWithoutClosingTheStream() throws IOException {
+    CloseTrackingInputStream inputStream =
+        new CloseTrackingInputStream(
+            new ByteArrayInputStream(TRACE.getBytes(StandardCharsets.UTF_8)));
+
+    String converted = CrashpadController.convertInputStreamToString(inputStream);
+
+    assertEquals(TRACE, gunzipAndDecode(converted));
+    assertFalse(inputStream.isClosed());
+  }
+
+  @Test
+  public void convertInputStreamToString_nullInputStream_returnsNull() throws IOException {
+    assertNull(CrashpadController.convertInputStreamToString(null));
+  }
+
+  /** Reverses {@code CrashpadController}'s gzip + base64 encoding of the trace file. */
+  private static String gunzipAndDecode(String traceFile) throws IOException {
+    byte[] gzipped = Base64.getDecoder().decode(traceFile);
+    try (GZIPInputStream gzip = new GZIPInputStream(new ByteArrayInputStream(gzipped));
+        ByteArrayOutputStream out = new ByteArrayOutputStream()) {
+      byte[] bytes = new byte[8192];
+      int length;
+      while ((length = gzip.read(bytes)) != -1) {
+        out.write(bytes, 0, length);
+      }
+      return out.toString(StandardCharsets.UTF_8.name());
+    }
+  }
+
+  private static final class CloseTrackingInputStream extends FilterInputStream {
+    private boolean closed = false;
+
+    CloseTrackingInputStream(InputStream inputStream) {
+      super(inputStream);
+    }
+
+    boolean isClosed() {
+      return closed;
+    }
+
+    @Override
+    public void close() throws IOException {
+      closed = true;
+      super.close();
+    }
+  }
+
+  private static final class ThrowingInputStream extends InputStream {
+    private boolean closed = false;
+
+    boolean isClosed() {
+      return closed;
+    }
+
+    @Override
+    public int read() throws IOException {
+      throw new IOException("Failed to read the trace");
+    }
+
+    @Override
+    public int read(byte[] bytes, int offset, int length) throws IOException {
+      throw new IOException("Failed to read the trace");
+    }
+
+    @Override
+    public void close() {
+      closed = true;
+    }
+  }
+}