From 43b8bcc01474bce480642acae2c554393c3bfb6a Mon Sep 17 00:00:00 2001
From: Jeff Chang <chengjeff@google.com>
Date: Tue, 8 Feb 2022 14:06:14 +0800
Subject: [PATCH] [RESTRICT AUTOMERGE] Do not resume activity if behind a
 translucent task

The top-focusable activity resides in the RESUMED state while the app
process is newly created and attached. The behavior may enable UI
hijacking attacks against apps implementing authentication.

This CL disallows the system to resume the activity for the case if it
is not visible or is occluded by other translucent tasks.

Bug: 211481342
Test: atest CtsWindowManagerDeviceTestCases:ActivityLifecycleTests
Change-Id: I7903494cf928b5b5613700262b7c5fff10f3c5a0
---
 .../server/wm/EnsureActivitiesVisibleHelper.java      |  2 +-
 .../com/android/server/wm/RootWindowContainer.java    |  3 ++-
 services/core/java/com/android/server/wm/Task.java    | 11 +++++++++++
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/services/core/java/com/android/server/wm/EnsureActivitiesVisibleHelper.java b/services/core/java/com/android/server/wm/EnsureActivitiesVisibleHelper.java
index c4e03f5c65f51..c49a1c9b24dc3 100644
--- a/services/core/java/com/android/server/wm/EnsureActivitiesVisibleHelper.java
+++ b/services/core/java/com/android/server/wm/EnsureActivitiesVisibleHelper.java
@@ -95,7 +95,7 @@ class EnsureActivitiesVisibleHelper {
         // activities are actually behind other fullscreen activities, but still required
         // to be visible (such as performing Recents animation).
         final boolean resumeTopActivity = mTop != null && !mTop.mLaunchTaskBehind
-                && mContiner.isTopActivityFocusable()
+                && mContiner.canBeResumed(starting)
                 && (starting == null || !starting.isDescendantOf(mContiner));
 
         final PooledConsumer f = PooledLambda.obtainConsumer(
diff --git a/services/core/java/com/android/server/wm/RootWindowContainer.java b/services/core/java/com/android/server/wm/RootWindowContainer.java
index 59c652e382677..c6d75fc6fe9ff 100644
--- a/services/core/java/com/android/server/wm/RootWindowContainer.java
+++ b/services/core/java/com/android/server/wm/RootWindowContainer.java
@@ -1963,7 +1963,8 @@ class RootWindowContainer extends WindowContainer<DisplayContent>
         }
 
         try {
-            if (mStackSupervisor.realStartActivityLocked(r, app, top == r /*andResume*/,
+            if (mStackSupervisor.realStartActivityLocked(r, app,
+                    top == r && r.getTask().canBeResumed(r) /*andResume*/,
                     true /*checkConfig*/)) {
                 mTmpBoolean = true;
             }
diff --git a/services/core/java/com/android/server/wm/Task.java b/services/core/java/com/android/server/wm/Task.java
index 98df383579c93..0be73815d9cfc 100644
--- a/services/core/java/com/android/server/wm/Task.java
+++ b/services/core/java/com/android/server/wm/Task.java
@@ -3638,6 +3638,17 @@ class Task extends WindowContainer<WindowContainer> {
         return getVisibility(starting) != STACK_VISIBILITY_INVISIBLE;
     }
 
+    /**
+     * Returns {@code true} is the activity in this Task can be resumed.
+     *
+     * @param starting The currently starting activity or {@code null} if there is none.
+     */
+    boolean canBeResumed(@Nullable ActivityRecord starting) {
+        // No need to resume activity in Task that is not visible.
+        return isTopActivityFocusable()
+                && getVisibility(starting) == STACK_VISIBILITY_VISIBLE;
+    }
+
     /**
      * Returns true if the task should be visible.
      *