From fbfa268d47c7915b7a87d3fef22a5b8f3bbabeb7 Mon Sep 17 00:00:00 2001
From: Oli Lan <olilan@google.com>
Date: Tue, 9 Aug 2022 17:48:15 +0100
Subject: [PATCH] Prevent non-admin users from deleting system apps.

This addresses a security issue where the guest user can remove updates
for system apps.

With this CL, attempts to uninstall/downgrade system apps will fail if
attempted by a non-admin user, unless the DELETE_SYSTEM_APP flag is
specified.

This is a fixed version of ag/17408864, to address b/236578018.

Bug: 170646036
Test: manual, try uninstalling system app update as guest
Merged-In: I4e959e296cca9bbdfc8fccc5e5e0e654ca524165
Change-Id: I6ecfef50294c9000a6ce539bdec6f372c872a40b
---
 .../com/android/server/pm/PackageManagerService.java  | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index bcbf7ddfb2a61..7fd3cf7f03f88 100644
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -18529,6 +18529,17 @@ public class PackageManagerService extends IPackageManager.Stub
                 return PackageManager.DELETE_FAILED_INTERNAL_ERROR;
             }
 
+            if (isSystemApp(uninstalledPs)
+                    && (deleteFlags & PackageManager.DELETE_SYSTEM_APP) == 0) {
+                UserInfo userInfo = mUserManager.getUserInfo(userId);
+                if (userInfo == null || !userInfo.isAdmin()) {
+                    Slog.w(TAG, "Not removing package " + packageName
+                            + " as only admin user may downgrade system apps");
+                    EventLog.writeEvent(0x534e4554, "170646036", -1, packageName);
+                    return PackageManager.DELETE_FAILED_USER_RESTRICTED;
+                }
+            }
+
             disabledSystemPs = mSettings.getDisabledSystemPkgLPr(packageName);
             // Save the enabled state before we delete the package. When deleting a stub
             // application we always set the enabled state to 'disabled'.