Rate limiting PiP aspect ratio change request

Using CountQuotaTrack to limit how frequent an app can request aspect
ratio change via PictureInPictureParams, which could result flood of PiP
resizing requests and freeze the PiP window.

Note that CountQuotaTrack is initialized out of the WM lock to avoid
dead lock with the AM one.

Bug: 283103220
Test: Manually, using the POC app
Test: Manually, switching YT PiP video functions at a regular rate
Test: atest WindowOrganizerTests ActivityThreadTest
Change-Id: Icb7dd17bbf7df573a9bb28f3dc56e90e78384f4f

2 files changed, 45 insertions, 0 deletions

diff --git a/services/core/java/com/android/server/wm/ActivityClientController.java b/services/core/java/com/android/server/wm/ActivityClientController.java
index fe4522acc148..c9395daff974 100644
--- a/services/core/java/com/android/server/wm/ActivityClientController.java
+++ b/services/core/java/com/android/server/wm/ActivityClientController.java
@@ -99,6 +99,7 @@ import android.view.RemoteAnimationDefinition;
 import android.window.SizeConfigurationBuckets;
 import android.window.TransitionInfo;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.app.AssistUtils;
 import com.android.internal.policy.IKeyguardDismissCallback;
 import com.android.internal.protolog.common.ProtoLog;
@@ -108,6 +109,9 @@ import com.android.server.pm.KnownPackages;
 import com.android.server.pm.pkg.AndroidPackage;
 import com.android.server.uri.GrantUri;
 import com.android.server.uri.NeededUriGrants;
+import com.android.server.utils.quota.Categorizer;
+import com.android.server.utils.quota.Category;
+import com.android.server.utils.quota.CountQuotaTracker;
 import com.android.server.vr.VrManagerInternal;
 
 /**
@@ -123,6 +127,13 @@ class ActivityClientController extends IActivityClientController.Stub {
     private final ActivityTaskSupervisor mTaskSupervisor;
     private final Context mContext;
 
+    // Prevent malicious app abusing the Activity#setPictureInPictureParams API
+    @VisibleForTesting CountQuotaTracker mSetPipAspectRatioQuotaTracker;
+    // Limit to 60 times / minute
+    private static final int SET_PIP_ASPECT_RATIO_LIMIT = 60;
+    // The timeWindowMs here can not be smaller than QuotaTracker#MIN_WINDOW_SIZE_MS
+    private static final long SET_PIP_ASPECT_RATIO_TIME_WINDOW_MS = 60_000;
+
     /** Wrapper around VoiceInteractionServiceManager. */
     private AssistUtils mAssistUtils;
 
@@ -946,6 +957,7 @@ class ActivityClientController extends IActivityClientController.Stub {
     public boolean enterPictureInPictureMode(IBinder token, final PictureInPictureParams params) {
         final long origId = Binder.clearCallingIdentity();
         try {
+            ensureSetPipAspectRatioQuotaTracker();
             synchronized (mGlobalLock) {
                 final ActivityRecord r = ensureValidPictureInPictureActivityParams(
                         "enterPictureInPictureMode", token, params);
@@ -960,6 +972,7 @@ class ActivityClientController extends IActivityClientController.Stub {
     public void setPictureInPictureParams(IBinder token, final PictureInPictureParams params) {
         final long origId = Binder.clearCallingIdentity();
         try {
+            ensureSetPipAspectRatioQuotaTracker();
             synchronized (mGlobalLock) {
                 final ActivityRecord r = ensureValidPictureInPictureActivityParams(
                         "setPictureInPictureParams", token, params);
@@ -1012,6 +1025,19 @@ class ActivityClientController extends IActivityClientController.Stub {
     }
 
     /**
+     * Initialize the {@link #mSetPipAspectRatioQuotaTracker} if applicable, which should happen
+     * out of {@link #mGlobalLock} to avoid deadlock (AM lock is used in QuotaTrack ctor).
+     */
+    private void ensureSetPipAspectRatioQuotaTracker() {
+        if (mSetPipAspectRatioQuotaTracker == null) {
+            mSetPipAspectRatioQuotaTracker = new CountQuotaTracker(mContext,
+                    Categorizer.SINGLE_CATEGORIZER);
+            mSetPipAspectRatioQuotaTracker.setCountLimit(Category.SINGLE_CATEGORY,
+                    SET_PIP_ASPECT_RATIO_LIMIT, SET_PIP_ASPECT_RATIO_TIME_WINDOW_MS);
+        }
+    }
+
+    /**
      * Checks the state of the system and the activity associated with the given {@param token} to
      * verify that picture-in-picture is supported for that activity.
      *
@@ -1035,6 +1061,19 @@ class ActivityClientController extends IActivityClientController.Stub {
                     + ": Current activity does not support picture-in-picture.");
         }
 
+        // Rate limit how frequent an app can request aspect ratio change via
+        // Activity#setPictureInPictureParams
+        final int userId = UserHandle.getCallingUserId();
+        if (r.pictureInPictureArgs.hasSetAspectRatio()
+                && params.hasSetAspectRatio()
+                && !r.pictureInPictureArgs.getAspectRatio().equals(
+                params.getAspectRatio())
+                && !mSetPipAspectRatioQuotaTracker.noteEvent(
+                userId, r.packageName, "setPipAspectRatio")) {
+            throw new IllegalStateException(caller
+                    + ": Too many PiP aspect ratio change requests from " + r.packageName);
+        }
+
         final float minAspectRatio = mContext.getResources().getFloat(
                 com.android.internal.R.dimen.config_pictureInPictureMinAspectRatio);
         final float maxAspectRatio = mContext.getResources().getFloat(
diff --git a/services/tests/wmtests/src/com/android/server/wm/WindowOrganizerTests.java b/services/tests/wmtests/src/com/android/server/wm/WindowOrganizerTests.java
index 43b424fab907..fb854c5bda68 100644
--- a/services/tests/wmtests/src/com/android/server/wm/WindowOrganizerTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/WindowOrganizerTests.java
@@ -1235,6 +1235,12 @@ public class WindowOrganizerTests extends WindowTestsBase {
         assertNotNull(o.mInfo);
         assertNotNull(o.mInfo.pictureInPictureParams);
 
+        // Bypass the quota check, which causes NPE in current test setup.
+        if (mWm.mAtmService.mActivityClientController.mSetPipAspectRatioQuotaTracker != null) {
+            mWm.mAtmService.mActivityClientController.mSetPipAspectRatioQuotaTracker
+                    .setEnabled(false);
+        }
+
         final PictureInPictureParams p2 = new PictureInPictureParams.Builder()
                 .setAspectRatio(new Rational(3, 4)).build();
         mWm.mAtmService.mActivityClientController.setPictureInPictureParams(record.token, p2);