From ef804614e20ec422194704aa7aa8eed15a520954 Mon Sep 17 00:00:00 2001
From: Siarhei Vishniakou <svv@google.com>
Date: Mon, 29 Nov 2021 09:07:25 -0800
Subject: [PATCH] Add ALLOW_SLIPPERY_TOUCHES permission

This permission allows the app to use FLAG_SLIPPERY. This means, windows
of the app that has this permission can let touches slip out when the
finger moves out of the window bounds.

Bug: 157929241
Bug: 206188649
Test: atest FlagSlipperyTest
Change-Id: I9ccdfd298f32c36b9c4da68c2e9c355c97dc7593
---
 core/res/AndroidManifest.xml                  |  4 ++++
 packages/SystemUI/AndroidManifest.xml         |  1 +
 .../com/android/server/wm/DisplayPolicy.java  | 17 ---------------
 .../server/wm/WindowManagerService.java       | 21 ++++++++++++++++++-
 4 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 316ea3455c69d..f84623a7691da 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -5845,6 +5845,10 @@
     <!-- Allows input events to be monitored. Very dangerous!  @hide -->
     <permission android:name="android.permission.MONITOR_INPUT"
                 android:protectionLevel="signature|recents" />
+    <!-- Allows the use of FLAG_SLIPPERY, which permits touch events to slip from the current
+         window to the window where the touch currently is on top of.  @hide -->
+    <permission android:name="android.permission.ALLOW_SLIPPERY_TOUCHES"
+                android:protectionLevel="signature|recents" />
     <!--  Allows the caller to change the associations between input devices and displays.
         Very dangerous! @hide -->
     <permission android:name="android.permission.ASSOCIATE_INPUT_DEVICE_TO_DISPLAY"
diff --git a/packages/SystemUI/AndroidManifest.xml b/packages/SystemUI/AndroidManifest.xml
index dde0a199f4269..f57d02cb95e8e 100644
--- a/packages/SystemUI/AndroidManifest.xml
+++ b/packages/SystemUI/AndroidManifest.xml
@@ -121,6 +121,7 @@
     <uses-permission android:name="android.permission.SET_ORIENTATION" />
     <uses-permission android:name="android.permission.DISABLE_KEYGUARD" />
     <uses-permission android:name="android.permission.MONITOR_INPUT" />
+    <uses-permission android:name="android.permission.ALLOW_SLIPPERY_TOUCHES" />
     <uses-permission android:name="android.permission.INPUT_CONSUMER" />
 
     <!-- DreamManager -->
diff --git a/services/core/java/com/android/server/wm/DisplayPolicy.java b/services/core/java/com/android/server/wm/DisplayPolicy.java
index 71ab5b617e8e3..4768b27a4f9ec 100644
--- a/services/core/java/com/android/server/wm/DisplayPolicy.java
+++ b/services/core/java/com/android/server/wm/DisplayPolicy.java
@@ -45,7 +45,6 @@ import static android.view.WindowManager.LayoutParams.FLAG_ALLOW_LOCK_WHILE_SCRE
 import static android.view.WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS;
 import static android.view.WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN;
 import static android.view.WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;
-import static android.view.WindowManager.LayoutParams.FLAG_SLIPPERY;
 import static android.view.WindowManager.LayoutParams.LAYOUT_IN_DISPLAY_CUTOUT_MODE_ALWAYS;
 import static android.view.WindowManager.LayoutParams.PRIVATE_FLAG_FORCE_DRAW_BAR_BACKGROUNDS;
 import static android.view.WindowManager.LayoutParams.PRIVATE_FLAG_FORCE_SHOW_STATUS_BAR;
@@ -845,20 +844,6 @@ public class DisplayPolicy {
         return true;
     }
 
-    /**
-     * Only trusted overlays are allowed to use FLAG_SLIPPERY.
-     */
-    static int sanitizeFlagSlippery(int flags, int privateFlags, String name) {
-        if ((flags & FLAG_SLIPPERY) == 0) {
-            return flags;
-        }
-        if ((privateFlags & PRIVATE_FLAG_TRUSTED_OVERLAY) != 0) {
-            return flags;
-        }
-        Slog.w(TAG, "Removing FLAG_SLIPPERY for non-trusted overlay " + name);
-        return flags & ~FLAG_SLIPPERY;
-    }
-
     /**
      * Sanitize the layout parameters coming from a client.  Allows the policy
      * to do things like ensure that windows of a specific type can't take
@@ -942,8 +927,6 @@ public class DisplayPolicy {
         } else if (mRoundedCornerWindow == win) {
             mRoundedCornerWindow = null;
         }
-
-        attrs.flags = sanitizeFlagSlippery(attrs.flags, attrs.privateFlags, win.getName());
     }
 
     /**
diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index 23f9c58b9af9f..35ffdf40492cf 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -1652,6 +1652,7 @@ public class WindowManagerService extends IWindowManager.Stub
 
             final DisplayPolicy displayPolicy = displayContent.getDisplayPolicy();
             displayPolicy.adjustWindowParamsLw(win, win.mAttrs);
+            attrs.flags = sanitizeFlagSlippery(attrs.flags, win.getName(), callingUid, callingPid);
             win.setRequestedVisibilities(requestedVisibilities);
 
             res = displayPolicy.validateAddingWindowLw(attrs, callingPid, callingUid);
@@ -2207,6 +2208,7 @@ public class WindowManagerService extends IWindowManager.Stub
             if (attrs != null) {
                 displayPolicy.adjustWindowParamsLw(win, attrs);
                 win.mToken.adjustWindowParams(win, attrs);
+                attrs.flags = sanitizeFlagSlippery(attrs.flags, win.getName(), uid, pid);
                 int disableFlags =
                         (attrs.systemUiVisibility | attrs.subtreeSystemUiVisibility) & DISABLE_MASK;
                 if (disableFlags != 0 && !hasStatusBarPermission(pid, uid)) {
@@ -8219,6 +8221,23 @@ public class WindowManagerService extends IWindowManager.Stub
         mAtmService.setFocusedTask(task.mTaskId, touchedActivity);
     }
 
+    /**
+     * You need ALLOW_SLIPPERY_TOUCHES permission to be able to set FLAG_SLIPPERY.
+     */
+    private int sanitizeFlagSlippery(int flags, String windowName, int callingUid, int callingPid) {
+        if ((flags & FLAG_SLIPPERY) == 0) {
+            return flags;
+        }
+        final int permissionResult = mContext.checkPermission(
+                    android.Manifest.permission.ALLOW_SLIPPERY_TOUCHES, callingPid, callingUid);
+        if (permissionResult != PackageManager.PERMISSION_GRANTED) {
+            Slog.w(TAG, "Removing FLAG_SLIPPERY from '" + windowName
+                    + "' because it doesn't have ALLOW_SLIPPERY_TOUCHES permission");
+            return flags & ~FLAG_SLIPPERY;
+        }
+        return flags;
+    }
+
     /**
      * Assigns an InputChannel to a SurfaceControl and configures it to receive
      * touch input according to it's on-screen geometry.
@@ -8258,7 +8277,7 @@ public class WindowManagerService extends IWindowManager.Stub
         h.setWindowToken(window);
         h.name = name;
 
-        flags = DisplayPolicy.sanitizeFlagSlippery(flags, privateFlags, name);
+        flags = sanitizeFlagSlippery(flags, name, callingUid, callingPid);
 
         final int sanitizedFlags = flags & (LayoutParams.FLAG_NOT_TOUCHABLE
                 | FLAG_SLIPPERY | LayoutParams.FLAG_NOT_FOCUSABLE);