Add toggle to allow or disable null algorithms

This adds the allow null algorithms toogle to the Settings UI.

If supported by the smartphone baseband, the toggle allows users to opt
out of null algorithms, unencrypted cellular communication, for all
cellular generations.

This toggle is behind a feature flag that is off by default. It also
requires radio network HAL 2.1 or later to show.

Co-authored-by: Gil Cukierman <cukie@google.com>
Bug: b/237529943
Test: atest NullAlgorithmsPreferenceControllerTest
Test: adb shell device_config put cellular_security
enable_null_cipher_toggle true; // On cuttlefish, you can now see the
toggle in SIM settings.

Change-Id: Ia03cceee5463171ca455fa0624b911e06f222d2d

tests/unit/src/com/android/settings/network/telephony/NullAlgorithmsPreferenceControllerTest.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright (C) 2020 The Android Open Source 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 com.android.settings.network.telephony;
+
+import static com.android.settings.core.BasePreferenceController.AVAILABLE;
+import static com.android.settings.core.BasePreferenceController.CONDITIONALLY_UNAVAILABLE;
+import static com.android.settings.core.BasePreferenceController.UNSUPPORTED_ON_DEVICE;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.content.Context;
+import android.os.Looper;
+import android.provider.DeviceConfig;
+import android.telephony.TelephonyManager;
+import android.util.Log;
+
+import androidx.preference.Preference;
+import androidx.preference.PreferenceManager;
+import androidx.preference.PreferenceScreen;
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+
+@RunWith(AndroidJUnit4.class)
+public final class NullAlgorithmsPreferenceControllerTest {
+    private static final String LOG_TAG = "NullAlgosControllerTest";
+    private static final int SUB_ID = 2;
+    private static final String PREFERENCE_KEY = "TEST_NULL_CIPHER_PREFERENCE";
+
+    @Mock
+    private TelephonyManager mTelephonyManager;
+    private Preference mPreference;
+    private PreferenceScreen mPreferenceScreen;
+    private NullAlgorithmsPreferenceController mController;
+    private Context mContext;
+    // Ideally we would use TestableDeviceConfig, but that's not doable because the Settings
+    // app is not currently debuggable. For now, we use the real device config and ensure that
+    // we reset the cellular_security namespace property to its pre-test value after every test.
+    private DeviceConfig.Properties mPreTestProperties;
+
+    @Before
+    public void setUp() {
+        if (Looper.myLooper() == null) {
+            Looper.prepare();
+        }
+
+        mPreTestProperties = DeviceConfig.getProperties(
+                TelephonyManager.PROPERTY_ENABLE_NULL_CIPHER_TOGGLE);
+
+        MockitoAnnotations.initMocks(this);
+
+        mContext = spy(ApplicationProvider.getApplicationContext());
+        when(mContext.getSystemService(TelephonyManager.class)).thenReturn(mTelephonyManager);
+
+        doReturn(mTelephonyManager).when(mTelephonyManager).createForSubscriptionId(SUB_ID);
+
+        mController = new NullAlgorithmsPreferenceController(mContext, PREFERENCE_KEY);
+
+        mPreference = spy(new Preference(mContext));
+        mPreference.setKey(PREFERENCE_KEY);
+        mPreferenceScreen = new PreferenceManager(mContext).createPreferenceScreen(mContext);
+        mPreferenceScreen.addPreference(mPreference);
+    }
+
+    @After
+    public void tearDown() {
+        try {
+            DeviceConfig.setProperties(mPreTestProperties);
+        } catch (DeviceConfig.BadConfigException e) {
+            Log.e(LOG_TAG,
+                    "Failed to reset DeviceConfig to pre-test state. Test results may be impacted. "
+                            + e.getMessage());
+        }
+    }
+
+    @Test
+    public void getAvailabilityStatus_unsupportedHardware_unsupportedOnDevice() {
+        DeviceConfig.setProperty(DeviceConfig.NAMESPACE_CELLULAR_SECURITY,
+                TelephonyManager.PROPERTY_ENABLE_NULL_CIPHER_TOGGLE, Boolean.TRUE.toString(),
+                false);
+        doThrow(UnsupportedOperationException.class).when(
+                mTelephonyManager).isNullCipherAndIntegrityPreferenceEnabled();
+        assertThat(mController.getAvailabilityStatus()).isEqualTo(UNSUPPORTED_ON_DEVICE);
+    }
+
+    @Test
+    public void getAvailabilityStatus_featureFlagOff_conditionallyUnavailable() {
+        doReturn(true).when(mTelephonyManager).isNullCipherAndIntegrityPreferenceEnabled();
+        DeviceConfig.setProperty(DeviceConfig.NAMESPACE_CELLULAR_SECURITY,
+                TelephonyManager.PROPERTY_ENABLE_NULL_CIPHER_TOGGLE, Boolean.FALSE.toString(),
+                false);
+        assertThat(mController.getAvailabilityStatus()).isEqualTo(CONDITIONALLY_UNAVAILABLE);
+    }
+
+    @Test
+    public void getAvailabilityStatus_returnAvailable() {
+        DeviceConfig.setProperty(DeviceConfig.NAMESPACE_CELLULAR_SECURITY,
+                TelephonyManager.PROPERTY_ENABLE_NULL_CIPHER_TOGGLE, Boolean.TRUE.toString(),
+                false);
+        // The value returned here shouldn't matter. The fact that this call is successful
+        // indicates that the device supports this operation
+        doReturn(true).when(mTelephonyManager).isNullCipherAndIntegrityPreferenceEnabled();
+        assertThat(mController.getAvailabilityStatus()).isEqualTo(AVAILABLE);
+    }
+
+    @Test
+    public void setChecked_true() {
+        mController.setChecked(true);
+        verify(mTelephonyManager, times(1)).setNullCipherAndIntegrityEnabled(true);
+    }
+
+    @Test
+    public void setChecked_false() {
+        mController.setChecked(false);
+        verify(mTelephonyManager, times(1)).setNullCipherAndIntegrityEnabled(false);
+    }
+}