Keyguard: Introduce 3rd party keyguard perms and utils

For CM13, the third party keyguard permission is being added to
the cmsdk rather than frameworks/base.  This patch also introduces
CmLockPatternUtils, a subclass of LockPatternUtils, which allows us
to make use of the new third party keyguard permissions in cmsdk.

Change-Id: I91fadfaae79e3f146e9ae73929cea91294ef8d87

cm/res/AndroidManifest.xml

@@ -135,6 +135,12 @@
             android:description="@string/permdesc_protectedApp"
             android:protectionLevel="signature|privileged" />
 
+    <!-- Allows an application to be used as a third party keyguard -->
+    <permission android:name="android.permission.THIRD_PARTY_KEYGUARD"
+                android:label="@string/permlab_thirdPartyKeyguard"
+                android:description="@string/permdesc_thirdPartyKeyguard"
+                android:protectionLevel="signature|privileged" />
+
     <application android:process="system"
                  android:persistent="true"
                  android:hasCode="false"

cm/res/res/values/strings.xml

@@ -122,4 +122,9 @@
     <string name="live_display_outdoor_summary">Use outdoor settings only</string>
     <string name="live_display_hint">LiveDisplay can help reduce eyestrain and help you sleep at night. Click here to try it out!</string>
 
+    <!-- Third party keyguard permission label -->
+    <string name="permlab_thirdPartyKeyguard">third party lock screen</string>
+    <!-- Third party keyguard permission description -->
+    <string name="permdesc_thirdPartyKeyguard">Allows an app to be used as an insecure lock screen.</string>
+
 </resources>

src/java/org/cyanogenmod/internal/util/CmLockPatternUtils.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2015 The CyanogenMod Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.cyanogenmod.internal.util;
+
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.pm.PackageInfo;
+import android.content.pm.PackageManager;
+import android.os.UserHandle;
+import android.text.TextUtils;
+
+import com.android.internal.widget.LockPatternUtils;
+
+import cyanogenmod.platform.Manifest;
+
+public class CmLockPatternUtils extends LockPatternUtils {
+
+    /**
+     * Third party keyguard component to be displayed within the keyguard
+     */
+    public static final String THIRD_PARTY_KEYGUARD_COMPONENT = "lockscreen.third_party";
+
+    private Context mContext;
+
+    public CmLockPatternUtils(Context context) {
+        super(context);
+        mContext = context;
+    }
+
+    /**
+     * Sets a third party lock screen.
+     * @param component
+     */
+    public void setThirdPartyKeyguard(ComponentName component)
+            throws PackageManager.NameNotFoundException {
+        if (component != null) {
+            // Check that the package this component belongs to has the third party keyguard perm
+            final PackageManager pm = mContext.getPackageManager();
+            final boolean hasThirdPartyKeyguardPermission = pm.checkPermission(
+                    Manifest.permission.THIRD_PARTY_KEYGUARD, component.getPackageName()) ==
+                        PackageManager.PERMISSION_GRANTED;
+            if (!hasThirdPartyKeyguardPermission) {
+                throw new SecurityException("Package " + component.getPackageName() + " does not" +
+                        "have " + Manifest.permission.THIRD_PARTY_KEYGUARD);
+            }
+        }
+
+        setString(THIRD_PARTY_KEYGUARD_COMPONENT,
+                component != null ? component.flattenToString() : "", getCurrentUser());
+    }
+
+    /**
+     * Get the currently applied 3rd party keyguard component
+     * @return
+     */
+    public ComponentName getThirdPartyKeyguardComponent() {
+        String component = getString(THIRD_PARTY_KEYGUARD_COMPONENT, getCurrentUser());
+        return component != null ? ComponentName.unflattenFromString(component) : null;
+    }
+
+    /**
+     * @return Whether a third party keyguard is set
+     */
+    public boolean isThirdPartyKeyguardEnabled() {
+        String component = getString(THIRD_PARTY_KEYGUARD_COMPONENT, getCurrentUser());
+        return !TextUtils.isEmpty(component);
+    }
+
+    private int getCurrentUser() {
+        return UserHandle.USER_CURRENT;
+    }
+}