Use compat flags to reflect the current status of legacy storage.

Scoped Storage status of an app can be changed by using compat flags,
as apps can chose to opt-in/opt out of Scoped Storage using these flags.
See ag/10406320 for more details.

Update documentation of isExternalStorageLegacy() method.

Remove checks around INSTALL_PACKAGES and OP_REQUEST_INSTALL_PACKAGES as
that does not allow legacy external storage.

Remove check for WRITE_MEDIA_STORAGE as its value is now
reflected by OP_LEGACY_STORAGE (ag/10162772)

Bug: 132649864
Test: atest ExternalStorageHostTest
Test: atest com.android.providers.media
Test: manually using StorageTest app
Merged-In: Id53da8f8783455038bad101e6ac50ba66b595012
Change-Id: Id53da8f8783455038bad101e6ac50ba66b595012
(cherry picked from commit f8af82046a52e588b56ca893aaf47de620f4c7ad)
diff --git a/core/java/android/os/Environment.java b/core/java/android/os/Environment.java
index f2fb5b2..09ccb72 100644
--- a/core/java/android/os/Environment.java
+++ b/core/java/android/os/Environment.java
@@ -23,6 +23,7 @@
 import android.app.AppGlobals;
 import android.app.AppOpsManager;
 import android.app.admin.DevicePolicyManager;
+import android.compat.Compatibility;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.content.Context;
 import android.content.Intent;
@@ -88,6 +89,16 @@
     private static final File DIR_APEX_ROOT = getDirectory(ENV_APEX_ROOT,
             "/apex");
 
+    /**
+     * See definition in com.android.providers.media.LocalCallingIdentity
+     */
+    private static final long DEFAULT_SCOPED_STORAGE = 149924527L;
+
+    /**
+     * See definition in com.android.providers.media.LocalCallingIdentity
+     */
+    private static final long FORCE_ENABLE_SCOPED_STORAGE = 132649864L;
+
     @UnsupportedAppUsage
     private static UserEnvironment sCurrentUser;
     private static boolean sUserRequired;
@@ -1191,12 +1202,13 @@
     }
 
     /**
-     * Returns whether the primary shared/external storage media is a legacy
-     * view that includes files not owned by the app.
+     * Returns whether the shared/external storage media is a
+     * legacy view that includes files not owned by the app.
      * <p>
      * This value may be different from the value requested by
      * {@code requestLegacyExternalStorage} in the app's manifest, since an app
-     * may inherit its legacy state based on when it was first installed.
+     * may inherit its legacy state based on when it was first installed, target sdk and other
+     * factors.
      * <p>
      * Non-legacy apps can continue to discover and read media belonging to
      * other apps via {@link android.provider.MediaStore}.
@@ -1207,18 +1219,19 @@
     }
 
     /**
-     * Returns whether the shared/external storage media at the given path is a
+     * Returns whether the shared/external storage media is a
      * legacy view that includes files not owned by the app.
      * <p>
      * This value may be different from the value requested by
      * {@code requestLegacyExternalStorage} in the app's manifest, since an app
-     * may inherit its legacy state based on when it was first installed.
+     * may inherit its legacy state based on when it was first installed, target sdk and other
+     * factors.
      * <p>
      * Non-legacy apps can continue to discover and read media belonging to
      * other apps via {@link android.provider.MediaStore}.
      *
      * @throws IllegalArgumentException if the path is not a valid storage
-     *             device.
+     * device.
      */
     public static boolean isExternalStorageLegacy(@NonNull File path) {
         final Context context = AppGlobals.getInitialApplication();
@@ -1232,24 +1245,23 @@
             return false;
         }
 
-        if (packageManager.checkPermission(Manifest.permission.WRITE_MEDIA_STORAGE,
-                context.getPackageName()) == PackageManager.PERMISSION_GRANTED) {
+        // TODO(b/150672994): Compat flags do not override instant app and isolated process's
+        //  behavior.
+        boolean defaultScopedStorage = Compatibility.isChangeEnabled(DEFAULT_SCOPED_STORAGE);
+        boolean forceEnableScopedStorage = Compatibility.isChangeEnabled(
+                FORCE_ENABLE_SCOPED_STORAGE);
+        // if Scoped Storage is strictly enforced, the app does *not* have legacy storage access
+        // Note: does not require packagename/uid as this is directly called from an app process
+        if (isScopedStorageEnforced(defaultScopedStorage, forceEnableScopedStorage)) {
+            return false;
+        }
+        // if Scoped Storage is strictly disabled, the app has legacy storage access
+        // Note: does not require packagename/uid as this is directly called from an app process
+        if (isScopedStorageDisabled(defaultScopedStorage, forceEnableScopedStorage)) {
             return true;
         }
 
-        if (packageManager.checkPermission(Manifest.permission.INSTALL_PACKAGES,
-                context.getPackageName()) == PackageManager.PERMISSION_GRANTED) {
-            return true;
-        }
         final AppOpsManager appOps = context.getSystemService(AppOpsManager.class);
-        final String[] packagesForUid = packageManager.getPackagesForUid(uid);
-        for (String packageName : packagesForUid) {
-            if (appOps.checkOpNoThrow(AppOpsManager.OP_REQUEST_INSTALL_PACKAGES,
-                    uid, packageName) == AppOpsManager.MODE_ALLOWED) {
-                return true;
-            }
-        }
-
         return appOps.checkOpNoThrow(AppOpsManager.OP_LEGACY_STORAGE,
                 uid, context.getOpPackageName()) == AppOpsManager.MODE_ALLOWED;
     }
@@ -1298,6 +1310,16 @@
         }
     }
 
+    private static boolean isScopedStorageEnforced(boolean defaultScopedStorage,
+            boolean forceEnableScopedStorage) {
+        return defaultScopedStorage && forceEnableScopedStorage;
+    }
+
+    private static boolean isScopedStorageDisabled(boolean defaultScopedStorage,
+            boolean forceEnableScopedStorage) {
+        return !defaultScopedStorage && !forceEnableScopedStorage;
+    }
+
     static File getDirectory(String variableName, String defaultPath) {
         String path = System.getenv(variableName);
         return path == null ? new File(defaultPath) : new File(path);