[Crypto] Initial support for OpenPGP clients

The default OpenPGP API doesn't work in AndroidX, therefore needed a workaround. There's an alternative library written in Kotlin (https://github.com/android-password-store/openpgp-ktx) but it inherits the same problem: it relies on Android preference library (an API is supposed to be independent of such a library). This workaround uses a single Dialog fragment to merge the two preferences and therefore, we have at least some control on how we are going to work with it. But I have to admit, the original OpenPGP library is not what a library should look like (neither is mine as a consequence). Related issue: open-keychain/open-keychain#2432

app/build.gradle

@@ -87,6 +87,7 @@ dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
     compileOnly project(path: ':HiddenApi')
     implementation project(path: ':libApkParser')
+    implementation project(path: ':libOpenPGP')
     implementation 'com.google.android.material:material:1.3.0-alpha02'
     implementation 'androidx.appcompat:appcompat:1.3.0-alpha02'
     implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.2.0-alpha01'

app/src/main/java/io/github/muntashirakon/AppManager/settings/OpenPgpKeySelectionDialogFragment.java

@@ -0,0 +1,148 @@
+/*
+ * Copyright (C) 2020 Muntashir Al-Islam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package io.github.muntashirakon.AppManager.settings;
+
+import android.app.Dialog;
+import android.app.PendingIntent;
+import android.content.Intent;
+import android.content.pm.PackageManager;
+import android.content.pm.ServiceInfo;
+import android.os.Bundle;
+
+import com.google.android.material.dialog.MaterialAlertDialogBuilder;
+
+import org.openintents.openpgp.IOpenPgpService2;
+import org.openintents.openpgp.OpenPgpError;
+import org.openintents.openpgp.util.OpenPgpApi;
+import org.openintents.openpgp.util.OpenPgpServiceConnection;
+import org.openintents.openpgp.util.OpenPgpUtils;
+
+import java.util.List;
+import java.util.Objects;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.activity.result.IntentSenderRequest;
+import androidx.activity.result.contract.ActivityResultContracts;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.fragment.app.DialogFragment;
+import androidx.fragment.app.FragmentActivity;
+import io.github.muntashirakon.AppManager.AppManager;
+import io.github.muntashirakon.AppManager.R;
+import io.github.muntashirakon.AppManager.logs.Log;
+import io.github.muntashirakon.AppManager.utils.AppPref;
+import io.github.muntashirakon.AppManager.utils.ArrayUtils;
+
+public class OpenPgpKeySelectionDialogFragment extends DialogFragment {
+    public static final String TAG = "OpenPgpKeySelectionDialogFragment";
+
+    private String mOpenPgpProvider;
+    private OpenPgpServiceConnection mServiceConnection;
+    private FragmentActivity activity;
+
+    private static final int NO_KEY = 0;
+
+    private ActivityResultLauncher<IntentSenderRequest> keyIdResultLauncher;
+
+    @NonNull
+    @Override
+    public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
+        activity = requireActivity();
+        // This must be registered using an activity context since the dialog won't exist
+        keyIdResultLauncher = activity.registerForActivityResult(
+                new ActivityResultContracts.StartIntentSenderForResult(),
+                result -> {
+                    if (result.getData() != null)
+                        getUserId(result.getData());
+                });
+        mOpenPgpProvider = (String) AppPref.get(AppPref.PrefKey.PREF_OPEN_PGP_PACKAGE_STR);
+        List<ServiceInfo> serviceInfoList = OpenPgpUtils.getPgpClientServices(activity);
+        CharSequence[] packageLabels = new String[serviceInfoList.size()];
+        String[] packageNames = new String[serviceInfoList.size()];
+        ServiceInfo serviceInfo;
+        PackageManager pm = activity.getPackageManager();
+        for (int i = 0; i < packageLabels.length; ++i) {
+            serviceInfo = serviceInfoList.get(i);
+            packageLabels[i] = serviceInfo.loadLabel(pm);
+            packageNames[i] = serviceInfo.packageName;
+        }
+        int choice = ArrayUtils.indexOf(packageNames, mOpenPgpProvider);
+        return new MaterialAlertDialogBuilder(activity)
+                .setTitle(R.string.open_pgp_provider)
+                .setSingleChoiceItems(packageLabels, choice, (dialog, which) -> {
+                    mOpenPgpProvider = packageNames[which];
+                    AppPref.set(AppPref.PrefKey.PREF_OPEN_PGP_PACKAGE_STR, mOpenPgpProvider);
+                })
+                .setNegativeButton(R.string.cancel, null)
+                .setPositiveButton(R.string.ok, (dialog, which) -> chooseKey())
+                .create();
+    }
+
+    private void chooseKey() {
+        // bind to service
+        mServiceConnection = new OpenPgpServiceConnection(AppManager.getContext(), mOpenPgpProvider,
+                new OpenPgpServiceConnection.OnBound() {
+                    @Override
+                    public void onBound(IOpenPgpService2 service) {
+                        getUserId(new Intent());
+                    }
+
+                    @Override
+                    public void onError(Exception e) {
+                        Log.e(OpenPgpApi.TAG, "exception on binding!", e);
+                    }
+                }
+        );
+        mServiceConnection.bindToService();
+    }
+
+    private void getUserId(@NonNull Intent data) {
+        data.setAction(OpenPgpApi.ACTION_GET_SIGN_KEY_ID);
+        data.putExtra(OpenPgpApi.EXTRA_USER_ID, "");
+        OpenPgpApi api = new OpenPgpApi(activity, mServiceConnection.getService());
+        api.executeApiAsync(data, null, null, new OpenPgpCallback());
+    }
+
+    private class OpenPgpCallback implements OpenPgpApi.IOpenPgpCallback {
+
+        private OpenPgpCallback() {
+        }
+
+        @Override
+        public void onReturn(@NonNull Intent result) {
+            switch (result.getIntExtra(OpenPgpApi.RESULT_CODE, OpenPgpApi.RESULT_CODE_ERROR)) {
+                case OpenPgpApi.RESULT_CODE_SUCCESS: {
+                    long keyId = result.getLongExtra(OpenPgpApi.EXTRA_SIGN_KEY_ID, NO_KEY);
+                    AppPref.set(AppPref.PrefKey.PREF_OPEN_PGP_USER_ID_LONG, keyId);
+                    break;
+                }
+                case OpenPgpApi.RESULT_CODE_USER_INTERACTION_REQUIRED: {
+                    PendingIntent pi = Objects.requireNonNull(result.getParcelableExtra(OpenPgpApi.RESULT_INTENT));
+                    keyIdResultLauncher.launch(new IntentSenderRequest.Builder(pi).build());
+                    break;
+                }
+                case OpenPgpApi.RESULT_CODE_ERROR: {
+                    OpenPgpError error = result.getParcelableExtra(OpenPgpApi.RESULT_ERROR);
+                    if (error != null)
+                        Log.e(OpenPgpApi.TAG, "RESULT_CODE_ERROR: " + error.getMessage());
+                    break;
+                }
+            }
+        }
+    }
+}

app/src/main/java/io/github/muntashirakon/AppManager/settings/SettingsActivity.java

@@ -173,6 +173,10 @@ protected void onCreate(Bundle savedInstanceState) {
                 })
                 .setNegativeButton(R.string.no, null)
                 .show());
+        // OpenPGP Provider
+        findViewById(R.id.open_pgp_provider).setOnClickListener(v ->
+                new OpenPgpKeySelectionDialogFragment().show(getSupportFragmentManager(),
+                        OpenPgpKeySelectionDialogFragment.TAG));
         // About
         findViewById(R.id.about_view).setOnClickListener(v -> {
             @SuppressLint("InflateParams")

app/src/main/java/io/github/muntashirakon/AppManager/utils/AppPref.java

@@ -60,6 +60,8 @@ public enum PrefKey {
         PREF_LAST_VERSION_CODE_LONG,
         PREF_MAIN_WINDOW_FILTER_FLAGS_INT,
         PREF_MAIN_WINDOW_SORT_ORDER_INT,
+        PREF_OPEN_PGP_PACKAGE_STR,
+        PREF_OPEN_PGP_USER_ID_LONG,
         PREF_PERMISSIONS_SORT_ORDER_INT,
         PREF_ROOT_MODE_ENABLED_BOOL,
         PREF_SHOW_DISCLAIMER_BOOL,
@@ -246,6 +248,7 @@ private Object getDefaultValue(@NonNull PrefKey key) {
             case PREF_SHOW_DISCLAIMER_BOOL:
                 return true;
             case PREF_LAST_VERSION_CODE_LONG:
+            case PREF_OPEN_PGP_USER_ID_LONG:
                 return 0L;
             case PREF_APP_THEME_INT:
                 return AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM;
@@ -259,6 +262,8 @@ private Object getDefaultValue(@NonNull PrefKey key) {
             case PREF_COMPONENTS_SORT_ORDER_INT:
             case PREF_PERMISSIONS_SORT_ORDER_INT:
                 return AppDetailsFragment.SORT_BY_NAME;
+            case PREF_OPEN_PGP_PACKAGE_STR:
+                return "";
         }
         throw new IllegalArgumentException("Pref key not found.");
     }

app/src/main/res/layout/activity_settings.xml

@@ -276,6 +276,34 @@
 
             </androidx.appcompat.widget.LinearLayoutCompat>
 
+            <View
+                android:layout_width="match_parent"
+                android:layout_height="1dp"
+                android:background="@color/ten_percent_black" />
+
+            <androidx.appcompat.widget.LinearLayoutCompat
+                android:id="@+id/open_pgp_provider"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:padding="@dimen/padding_medium"
+                android:background="?selectableItemBackground"
+                android:orientation="vertical">
+
+                <TextView
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:textColor="?android:attr/textColorPrimary"
+                    android:text="@string/open_pgp_provider"
+                    android:textSize="@dimen/title_font" />
+
+                <TextView
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:text="@string/pref_open_pgp_provider_msg"
+                    android:textSize="@dimen/subtitle_font" />
+
+            </androidx.appcompat.widget.LinearLayoutCompat>
+
             <View
                 android:layout_width="match_parent"
                 android:layout_height="1dp"

app/src/main/res/values/strings.xml

@@ -618,4 +618,6 @@
     <string name="ok">OK</string>
     <string name="cancel">Cancel</string>
     <string name="systemless_app">Systemless App</string>
+    <string name="open_pgp_provider">OpenPGP Provider</string>
+    <string name="pref_open_pgp_provider_msg">Adding an OpenPGP provider enables you to encrypt sensitive info such as app data backups</string>
 </resources>

libOpenPGP/.gitignore

@@ -0,0 +1 @@
+/build

libOpenPGP/build.gradle

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2020 Muntashir Al-Islam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+apply plugin: 'com.android.library'
+
+android {
+    compileSdkVersion 29
+
+    defaultConfig {
+        minSdkVersion 21
+        targetSdkVersion 29
+        versionCode 11
+        versionName "11"
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+        preRelease {
+            minifyEnabled false
+            versionNameSuffix '-PRE'
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+dependencies {
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+    implementation 'androidx.annotation:annotation:1.1.0'
+}
+
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"

libOpenPGP/src/main/AndroidManifest.xml

@@ -0,0 +1,18 @@
+<!--
+  ~ Copyright (C) 2020 Muntashir Al-Islam
+  ~
+  ~ This program is free software: you can redistribute it and/or modify
+  ~ it under the terms of the GNU General Public License as published by
+  ~ the Free Software Foundation, either version 3 of the License, or
+  ~ (at your option) any later version.
+  ~
+  ~ This program is distributed in the hope that it will be useful,
+  ~ but WITHOUT ANY WARRANTY; without even the implied warranty of
+  ~ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  ~ GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License
+  ~ along with this program.  If not, see <https://www.gnu.org/licenses/>.
+  -->
+
+<manifest package="org.openintents.openpgp" />

libOpenPGP/src/main/aidl/org/openintents/openpgp/IOpenPgpService.aidl

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2014-2015 Dominik Schürmann <[email protected]>
+ *
+ * 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.openintents.openpgp;
+
+interface IOpenPgpService {
+
+    /**
+     * do NOT use this, data returned from the service through "output" may be truncated
+     * @deprecated
+     */
+    Intent execute(in Intent data, in ParcelFileDescriptor input, in ParcelFileDescriptor output);
+
+}

libOpenPGP/src/main/aidl/org/openintents/openpgp/IOpenPgpService2.aidl

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2015 Dominik Schürmann <[email protected]>
+ *
+ * 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.openintents.openpgp;
+
+interface IOpenPgpService2 {
+
+    /**
+     * see org.openintents.openpgp.util.OpenPgpApi for documentation
+     */
+    ParcelFileDescriptor createOutputPipe(in int pipeId);
+
+    /**
+     * see org.openintents.openpgp.util.OpenPgpApi for documentation
+     */
+    Intent execute(in Intent data, in ParcelFileDescriptor input, int pipeId);
+}