From f464ff68fde68c2452900be9948a119895609323 Mon Sep 17 00:00:00 2001
From: Nikita Ioffe <ioffe@google.com>
Date: Thu, 16 Jun 2022 13:36:35 +0100
Subject: [PATCH] Handle the visibility of sdk sandbox uids

Sdk sandbox processes have the following visibility rules:

1. Sdk sandbox process should be visible to itself
2. Sdk sandbox process should be visible to the corresponding client app
3. Sdk sandbox process shouldn't be visible to anything else

On top of that handle the NPE in the
ComputerEngine.shouldFilterApplication by treating null
PackageStateInternal the same way it is treated in case the calling uid
belongs to the instant app, which is to pretend that null application
exists and that it shouldn't be visible to sdk sandbox.

Bug: 236162773
Test: atest SdkSandboxInprocessTests
Change-Id: Ic2583610f55c36169f9abb35b58a0ab60884a312
---
 .../com/android/server/pm/ComputerEngine.java | 21 +++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/services/core/java/com/android/server/pm/ComputerEngine.java b/services/core/java/com/android/server/pm/ComputerEngine.java
index 31847bcbc5171..9489dc8de5930 100644
--- a/services/core/java/com/android/server/pm/ComputerEngine.java
+++ b/services/core/java/com/android/server/pm/ComputerEngine.java
@@ -2726,7 +2726,7 @@ public class ComputerEngine implements Computer {
         if (Process.isSdkSandboxUid(callingUid)) {
             int clientAppUid = Process.getAppUidForSdkSandboxUid(callingUid);
             // SDK sandbox should be able to see it's client app
-            if (clientAppUid == UserHandle.getUid(userId, ps.getAppId())) {
+            if (ps != null && clientAppUid == UserHandle.getUid(userId, ps.getAppId())) {
                 return false;
             }
         }
@@ -2740,9 +2740,9 @@ public class ComputerEngine implements Computer {
         // these hidden application details to customize carrier apps.
         if (ps == null || (filterUninstall && !ps.isHiddenUntilInstalled()
                 && !ps.getUserStateOrDefault(userId).isInstalled())) {
-            // If caller is instant app and ps is null, pretend the application exists,
-            // but, needs to be filtered
-            return (callerIsInstantApp || filterUninstall);
+            // If caller is instant app or sdk sandbox and ps is null, pretend the application
+            // exists, but, needs to be filtered
+            return (callerIsInstantApp || filterUninstall || Process.isSdkSandboxUid(callingUid));
         }
         // if the target and caller are the same application, don't filter
         if (isCallerSameApp(ps.getPackageName(), callingUid)) {
@@ -3173,6 +3173,19 @@ public class ComputerEngine implements Computer {
     }
 
     public boolean filterAppAccess(int uid, int callingUid) {
+        if (Process.isSdkSandboxUid(uid)) {
+            // Sdk sandbox instance should be able to see itself.
+            if (callingUid == uid) {
+                return false;
+            }
+            final int clientAppUid = Process.getAppUidForSdkSandboxUid(uid);
+            // Client app of this sdk sandbox process should be able to see it.
+            if (clientAppUid == uid) {
+                return false;
+            }
+            // Nobody else should be able to see the sdk sandbox process.
+            return true;
+        }
         final int userId = UserHandle.getUserId(uid);
         final int appId = UserHandle.getAppId(uid);
         final Object setting = mSettings.getSettingBase(appId);