From 628b7851dcf35f8cf0e4369114a8e194ddb9e3ca Mon Sep 17 00:00:00 2001
From: Jeff Chang <chengjeff@google.com>
Date: Tue, 25 Jan 2022 12:35:46 +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 316c20ba5c47f..e08816117f2ba 100644
--- a/services/core/java/com/android/server/wm/EnsureActivitiesVisibleHelper.java
+++ b/services/core/java/com/android/server/wm/EnsureActivitiesVisibleHelper.java
@@ -93,7 +93,7 @@ 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
-                && mTask.isTopActivityFocusable()
+                && mTask.canBeResumed(starting)
                 && (starting == null || !starting.isDescendantOf(mTask));
 
         mTask.forAllActivities(a -> {
diff --git a/services/core/java/com/android/server/wm/RootWindowContainer.java b/services/core/java/com/android/server/wm/RootWindowContainer.java
index 52da4b80a75d1..22a11353eae40 100644
--- a/services/core/java/com/android/server/wm/RootWindowContainer.java
+++ b/services/core/java/com/android/server/wm/RootWindowContainer.java
@@ -1948,7 +1948,8 @@ class RootWindowContainer extends WindowContainer<DisplayContent>
 
         try {
             if (mTaskSupervisor.realStartActivityLocked(r, app,
-                    top == r && r.isFocusable() /*andResume*/, true /*checkConfig*/)) {
+                    top == r && r.getTask().canBeResumed(r) /*andResume*/,
+                    true /*checkConfig*/)) {
                 mTmpBoolean = true;
             }
         } catch (RemoteException e) {
diff --git a/services/core/java/com/android/server/wm/Task.java b/services/core/java/com/android/server/wm/Task.java
index 96f18bd1b4c3e..8723ecb6a9758 100644
--- a/services/core/java/com/android/server/wm/Task.java
+++ b/services/core/java/com/android/server/wm/Task.java
@@ -4240,6 +4240,17 @@ class Task extends WindowContainer<WindowContainer> {
         return getVisibility(starting) != TASK_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) == TASK_VISIBILITY_VISIBLE;
+    }
+
     /**
      * Returns true if the task should be visible.
      *