Revert^2 "[SettingsProvider] @Readable annotation to restrict access to hidden keys"

New in this revert:
+ Added missing annotations.
+ Added check for system apps.

BUG: 175024829
Test: atest android.appsecurity.cts.ReadableSettingsFieldsTest
Test: atest android.app.cts.NotificationTemplateTest
Test: atest com.android.systemui.statusbar.notification.row.ExpandableNotificationRowTest

1ca518c1ec75b8307126991ae2d253911b2be10c
Change-Id: I3f270831692b5ba0841e85b84902d0b101ff1095

Change-Id: I4cab132c1ef10f4319b570e8e9e15dcde6d909f8

packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java

@@ -297,6 +297,24 @@ public class SettingsProvider extends ContentProvider {
         Settings.System.getCloneFromParentOnValueSettings(sSystemCloneFromParentOnDependency);
     }
 
+    private static final Set<String> sAllSecureSettings = new ArraySet<>();
+    private static final Set<String> sReadableSecureSettings = new ArraySet<>();
+    static {
+        Settings.Secure.getPublicSettings(sAllSecureSettings, sReadableSecureSettings);
+    }
+
+    private static final Set<String> sAllSystemSettings = new ArraySet<>();
+    private static final Set<String> sReadableSystemSettings = new ArraySet<>();
+    static {
+        Settings.System.getPublicSettings(sAllSystemSettings, sReadableSystemSettings);
+    }
+
+    private static final Set<String> sAllGlobalSettings = new ArraySet<>();
+    private static final Set<String> sReadableGlobalSettings = new ArraySet<>();
+    static {
+        Settings.Global.getPublicSettings(sAllGlobalSettings, sReadableGlobalSettings);
+    }
+
     private final Object mLock = new Object();
 
     @GuardedBy("mLock")
@@ -1919,6 +1937,7 @@ public class SettingsProvider extends ContentProvider {
         if (UserHandle.getAppId(Binder.getCallingUid()) < Process.FIRST_APPLICATION_UID) {
             return;
         }
+        checkReadableAnnotation(settingsType, settingName);
         ApplicationInfo ai = getCallingApplicationInfoOrThrow();
         if (!ai.isInstantApp()) {
             return;
@@ -1932,6 +1951,41 @@ public class SettingsProvider extends ContentProvider {
         }
     }
 
+    /**
+     * Check if the target settings key is readable. Reject if the caller app is trying to access a
+     * settings key defined in the Settings.Secure, Settings.System or Settings.Global and is not
+     * annotated as @Readable.
+     * Notice that a key string that is not defined in any of the Settings.* classes will still be
+     * regarded as readable.
+     */
+    private void checkReadableAnnotation(int settingsType, String settingName) {
+        final Set<String> allFields;
+        final Set<String> readableFields;
+        switch (settingsType) {
+            case SETTINGS_TYPE_GLOBAL:
+                allFields = sAllGlobalSettings;
+                readableFields = sReadableGlobalSettings;
+                break;
+            case SETTINGS_TYPE_SYSTEM:
+                allFields = sAllSystemSettings;
+                readableFields = sReadableSystemSettings;
+                break;
+            case SETTINGS_TYPE_SECURE:
+                allFields = sAllSecureSettings;
+                readableFields = sReadableSecureSettings;
+                break;
+            default:
+                throw new IllegalArgumentException("Invalid settings type: " + settingsType);
+        }
+
+        if (allFields.contains(settingName) && !readableFields.contains(settingName)) {
+            throw new SecurityException(
+                    "Settings key: <" + settingName + "> is not readable. From S+, new public "
+                            + "settings keys need to be annotated with @Readable unless they are "
+                            + "annotated with @hide.");
+        }
+    }
+
     private ApplicationInfo getCallingApplicationInfoOrThrow() {
         // We always use the callingUid for this lookup. This means that if hypothetically an
         // app was installed in user A with cross user and in user B as an Instant App