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Commit 1b794fae authored by Dianne Hackborn's avatar Dianne Hackborn
Browse files

Fix issue #72151749: Lock down 'clear cache' functionality to... 

...only system signature

Apps that hold the original permission are silently ignored.  There
is a new internal permission you must hold to actually delete cache
files.

Test: booted and run, can still clear cache in settings.
Bug: 72151749
Change-Id: I47a5cb697e1a4fa3665ac71aaabcda57bef7b561
parent 4945e8e3

core/res/AndroidManifest.xml

+7 −2
Original line number Diff line number Diff line
@@ -2955,11 +2955,16 @@ 
    <permission android:name="android.permission.MANAGE_SCOPED_ACCESS_DIRECTORY_PERMISSIONS"

        android:protectionLevel="signature" />



    <!-- @SystemApi Allows an application to delete cache files.

    <p>Not for use by third-party applications. -->

    <!-- @SystemApi Old permission for deleting an app's cache files, no longer used,

         but signals for us to quietly ignore calls instead of throwing an exception. -->

    <permission android:name="android.permission.DELETE_CACHE_FILES"

        android:protectionLevel="signature|privileged" />



    <!-- Allows an application to delete cache files.

         @hide -->

    <permission android:name="android.permission.INTERNAL_DELETE_CACHE_FILES"

        android:protectionLevel="signature" />



    <!-- @SystemApi Allows an application to delete packages.

         <p>Not for use by third-party applications.

         <p>Starting in {@link android.os.Build.VERSION_CODES#N}, user confirmation is requested

services/core/java/com/android/server/pm/PackageManagerService.java

+15 −2
Original line number Diff line number Diff line
@@ -19102,8 +19102,21 @@ public class PackageManagerService extends IPackageManager.Stub 
    public void deleteApplicationCacheFilesAsUser(final String packageName, final int userId,

            final IPackageDataObserver observer) {

        final int callingUid = Binder.getCallingUid();

        if (mContext.checkCallingOrSelfPermission(

                android.Manifest.permission.INTERNAL_DELETE_CACHE_FILES)

                != PackageManager.PERMISSION_GRANTED) {

            // If the caller has the old delete cache permission, silently ignore.  Else throw.

            if (mContext.checkCallingOrSelfPermission(

                    android.Manifest.permission.DELETE_CACHE_FILES)

                    == PackageManager.PERMISSION_GRANTED) {

                Slog.w(TAG, "Calling uid " + callingUid + " does not have " +

                        android.Manifest.permission.INTERNAL_DELETE_CACHE_FILES +

                        ", silently ignoring");

                return;

            }

            mContext.enforceCallingOrSelfPermission(

                android.Manifest.permission.DELETE_CACHE_FILES, null);

                    android.Manifest.permission.INTERNAL_DELETE_CACHE_FILES, null);

        }

        mPermissionManager.enforceCrossUserPermission(callingUid, userId,

                /* requireFullPermission= */ true, /* checkShell= */ false,

                "delete application cache files");