Bug: 21589105 Rescope WRITE_SETTINGS permission (framework services perm check

changes)

AppOpsManager:
Changed the default operating mode for WRITE_SETTINGS to MODE_DEFAULT from
MODE_ALLOWED.

packages/SettingsProvider:
We no longer do static permission checks for WRITE_SETTINGS in early checks and
defer that to app op when MODE_DEFAULT is returned. For some operations,
checking against WRITE_SECURE_SETTINGS is sufficient.

ActivityManagerService & PowerManagerService:
Incorporated app op checks and handled the MODE_DEFAULT case.

provider/Settings:
Added helper function to do checks on whether app ops protected operations
can be performed by a caller. This includes checks for WRITE_SETTINGS and
SYSTEM_ALERT_WINDOW.
Also added a public API (with javadocs) for apps to query if they can modify
system settings.
Changed the javadocs description for ACTION_MANAGE_WRITE_SETTINGS and
ACTION_MANAGE_OVERLAY_PERMISSION.
Added public API (with javadocs) for apps to query whether they can draw overlays or not,
and also javadocs description on how to use that check.

Change-Id: I7b651fe8af836c2074defdbd6acfec3f32acdbe9

2 files changed, 29 insertions, 4 deletions

diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 89e500e..783dea5 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -17201,8 +17201,7 @@ public final class ActivityManagerService extends ActivityManagerNative
     public void updatePersistentConfiguration(Configuration values) {
         enforceCallingPermission(android.Manifest.permission.CHANGE_CONFIGURATION,
                 "updateConfiguration()");
-        enforceCallingPermission(android.Manifest.permission.WRITE_SETTINGS,
-                "updateConfiguration()");
+        enforceWriteSettingsPermission("updateConfiguration()");
         if (values == null) {
             throw new NullPointerException("Configuration must not be null");
         }
@@ -17214,6 +17213,25 @@ public final class ActivityManagerService extends ActivityManagerNative
         }
     }
 
+    private void enforceWriteSettingsPermission(String func) {
+        int uid = Binder.getCallingUid();
+        if (uid == Process.ROOT_UID) {
+            return;
+        }
+
+        if (Settings.checkAndNoteWriteSettingsOperation(mContext, uid,
+                Settings.getPackageNameForUid(mContext, uid), false)) {
+            return;
+        }
+
+        String msg = "Permission Denial: " + func + " from pid="
+                + Binder.getCallingPid()
+                + ", uid=" + uid
+                + " requires " + android.Manifest.permission.WRITE_SETTINGS;
+        Slog.w(TAG, msg);
+        throw new SecurityException(msg);
+    }
+
     public void updateConfiguration(Configuration values) {
         enforceCallingPermission(android.Manifest.permission.CHANGE_CONFIGURATION,
                 "updateConfiguration()");
diff --git a/services/core/java/com/android/server/power/PowerManagerService.java b/services/core/java/com/android/server/power/PowerManagerService.java
index 88476ce..b920f97 100644
--- a/services/core/java/com/android/server/power/PowerManagerService.java
+++ b/services/core/java/com/android/server/power/PowerManagerService.java
@@ -30,6 +30,7 @@ import com.android.server.lights.LightsManager;
 import com.android.server.Watchdog;
 
 import android.Manifest;
+import android.app.AppOpsManager;
 import android.content.BroadcastReceiver;
 import android.content.ContentResolver;
 import android.content.Context;
@@ -3319,8 +3320,14 @@ public final class PowerManagerService extends SystemService
          */
         @Override // Binder call
         public void setStayOnSetting(int val) {
-            mContext.enforceCallingOrSelfPermission(
-                    android.Manifest.permission.WRITE_SETTINGS, null);
+            int uid = Binder.getCallingUid();
+            // if uid is of root's, we permit this operation straight away
+            if (uid != Process.ROOT_UID) {
+                if (!Settings.checkAndNoteWriteSettingsOperation(mContext, uid,
+                        Settings.getPackageNameForUid(mContext, uid), true)) {
+                    return;
+                }
+            }
 
             final long ident = Binder.clearCallingIdentity();
             try {