feat: Improve code quality of the cryptography

example/lib/main.dart

@@ -12,50 +12,22 @@ void main() {
 class MyApp extends StatelessWidget {
   const MyApp({Key? key}) : super(key: key);
 
-  // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      title: 'Flutter Demo',
+      title: 'Moxplatform Demo',
       theme: ThemeData(
-        // This is the theme of your application.
-        //
-        // Try running your application with "flutter run". You'll see the
-        // application has a blue toolbar. Then, without quitting the app, try
-        // changing the primarySwatch below to Colors.green and then invoke
-        // "hot reload" (press "r" in the console where you ran "flutter run",
-        // or simply save your changes to "hot reload" in a Flutter IDE).
-        // Notice that the counter didn't reset back to zero; the application
-        // is not restarted.
         primarySwatch: Colors.blue,
       ),
-      home: const MyHomePage(title: 'Flutter Demo Home Page'),
+      home: const MyHomePage(),
     );
   }
 }
 
-class MyHomePage extends StatefulWidget {
+class MyHomePage extends StatelessWidget {
-  const MyHomePage({Key? key, required this.title}) : super(key: key);
+  const MyHomePage({super.key});
 
-  // This widget is the home page of your application. It is stateful, meaning
+  Future<void> _cryptoTest() async {
-  // that it has a State object (defined below) that contains fields that affect
-  // how it looks.
-
-  // This class is the configuration for the state. It holds the values (in this
-  // case the title) provided by the parent (in this case the App widget) and
-  // used by the build method of the State. Fields in a Widget subclass are
-  // always marked "final".
-
-  final String title;
-
-  @override
-  State<MyHomePage> createState() => _MyHomePageState();
-}
-
-class _MyHomePageState extends State<MyHomePage> {
-  int _counter = 0;
-
-  Future<void> _incrementCounter() async {
     final result = await FilePicker.platform.pickFiles();
     if (result == null) {
       return;
@@ -65,7 +37,7 @@ class _MyHomePageState extends State<MyHomePage> {
     final path = result.files.single.path;
     final enc = await MoxplatformPlugin.crypto.encryptFile(
       path!,
-      path + '.enc',
+      '$path.enc',
       Uint8List.fromList(List.filled(32, 1)),
       Uint8List.fromList(List.filled(16, 2)),
       CipherAlgorithm.aes256CbcPkcs7,
@@ -76,13 +48,13 @@ class _MyHomePageState extends State<MyHomePage> {
     final diff = end.millisecondsSinceEpoch - start.millisecondsSinceEpoch;
     print('TIME: ${diff / 1000}s');
     print('DONE (${enc != null})');
-    final lengthEnc = await File(path + ".enc").length();
+    final lengthEnc = await File('$path.enc').length();
     final lengthOrig = await File(path).length();
     print('Encrypted file is $lengthEnc Bytes large (Orig $lengthOrig)');
 
     await MoxplatformPlugin.crypto.decryptFile(
-      path + '.enc',
+      '$path.enc',
-      path + '.dec',
+      '$path.dec',
       Uint8List.fromList(List.filled(32, 1)),
       Uint8List.fromList(List.filled(16, 2)),
       CipherAlgorithm.aes256CbcPkcs7,
@@ -90,69 +62,41 @@ class _MyHomePageState extends State<MyHomePage> {
     );
     print('DONE');
 
-    final lengthDec = await File(path + ".dec").length();
+    final lengthDec = await File('$path.dec').length();
     print('Decrypted file is $lengthDec Bytes large (Orig $lengthOrig)');
   }
 
   @override
   Widget build(BuildContext context) {
-    // This method is rerun every time setState is called, for instance as done
-    // by the _incrementCounter method above.
-    //
-    // The Flutter framework has been optimized to make rerunning build methods
-    // fast, so that you can just rebuild anything that needs updating rather
-    // than having to individually change instances of widgets.
     return Scaffold(
       appBar: AppBar(
-        // Here we take the value from the MyHomePage object that was created by
+        title: const Text('Moxplatform Demo'),
-        // the App.build method, and use it to set our appbar title.
-        title: Text(widget.title),
       ),
       body: Center(
-        // Center is a layout widget. It takes a single child and positions it
-        // in the middle of the parent.
         child: Column(
-          // Column is also a layout widget. It takes a list of children and
-          // arranges them vertically. By default, it sizes itself to fit its
-          // children horizontally, and tries to be as tall as its parent.
-          //
-          // Invoke "debug painting" (press "p" in the console, choose the
-          // "Toggle Debug Paint" action from the Flutter Inspector in Android
-          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
-          // to see the wireframe for each widget.
-          //
-          // Column has various properties to control how it sizes itself and
-          // how it positions its children. Here we use mainAxisAlignment to
-          // center the children vertically; the main axis here is the vertical
-          // axis because Columns are vertical (the cross axis would be
-          // horizontal).
           mainAxisAlignment: MainAxisAlignment.center,
           children: <Widget>[
-            const Text(
+            ElevatedButton(
-              'You have pushed the button this many times:',
+              onPressed: _cryptoTest,
+              child: const Text('Test cryptography'),
             ),
-            Text(
-              '$_counter',
-              style: Theme.of(context).textTheme.headline4,
-            ),
-
             ElevatedButton(
               onPressed: () {
                 MoxplatformPlugin.contacts.recordSentMessage('Hallo', 'Welt');
               },
-              child: Text('Test recordSentMessage (no fallback)'),
+              child: const Text('Test recordSentMessage (no fallback)'),
             ),
             ElevatedButton(
               onPressed: () {
                 MoxplatformPlugin.contacts.recordSentMessage('Person', 'Person', fallbackIcon: FallbackIconType.person);
               },
-              child: Text('Test recordSentMessage (person fallback)'),
+              child: const Text('Test recordSentMessage (person fallback)'),
             ),
             ElevatedButton(
               onPressed: () {
                 MoxplatformPlugin.contacts.recordSentMessage('Notes', 'Notes', fallbackIcon: FallbackIconType.notes);
               },
-              child: Text('Test recordSentMessage (notes fallback)'),
+              child: const Text('Test recordSentMessage (notes fallback)'),
             ),
           ],
         ),

packages/moxplatform_android/android/src/main/java/me/polynom/moxplatform_android/Constants.kt

@@ -0,0 +1,26 @@
+package me.polynom.moxplatform_android
+
+// The tag we use for logging.
+const val TAG = "Moxplatform"
+
+// The size of the buffer to hashing, encryption, and decryption in bytes.
+const val BUFFER_SIZE = 8096
+
+// TODO: Maybe try again to rewrite the entire plugin in Kotlin
+//const val METHOD_CHANNEL_KEY = "me.polynom.moxplatform_android"
+//const val BACKGROUND_METHOD_CHANNEL_KEY = METHOD_CHANNEL_KEY + "_bg"
+
+// https://github.com/ekasetiawans/flutter_background_service/blob/e427f3b70138ec26f9671c2617f9061f25eade6f/packages/flutter_background_service_android/android/src/main/java/id/flutter/flutter_background_service/BootReceiver.java#L20
+//const val WAKELOCK_DURATION = 10*60*1000L;
+
+// The name of the wakelock the background service manager holds.
+//const val SERVICE_WAKELOCK_NAME = "BackgroundService.Lock"
+
+//const val DATA_RECEIVER_METHOD_NAME = "dataReceived"
+
+// Shared preferences keys
+//const val SHARED_PREFERENCES_KEY = "me.polynom.moxplatform_android"
+//const val SP_MANUALLY_STOPPED_KEY = "manually_stopped"
+//const val SP_ENTRYPOINT_KEY = "entrypoint_handle"
+//const val SP_EXTRA_DATA_KEY = "extra_data"
+//const val SP_AUTO_START_AT_BOOT_KEY = "auto_start_at_boot"

packages/moxplatform_android/android/src/main/java/me/polynom/moxplatform_android/Crypto.kt

@@ -0,0 +1,144 @@
+package me.polynom.moxplatform_android
+
+import android.util.Log
+
+import java.io.FileInputStream
+import java.io.FileOutputStream
+import java.lang.Exception
+import java.security.MessageDigest
+import javax.crypto.Cipher
+import javax.crypto.CipherOutputStream
+import javax.crypto.spec.IvParameterSpec
+import javax.crypto.spec.SecretKeySpec
+
+// A FileOutputStream that continuously hashes whatever it writes to the file.
+private class HashedFileOutputStream(name: String, hashAlgorithm: String) : FileOutputStream(name) {
+    private val digest: MessageDigest
+
+    init {
+        this.digest = MessageDigest.getInstance(hashAlgorithm)
+    }
+
+    override fun write(buffer: ByteArray, offset: Int, length: Int) {
+        super.write(buffer, offset, length)
+
+        digest.update(buffer, offset, length)
+    }
+
+    fun digest() : ByteArray {
+        return digest.digest()
+    }
+}
+
+fun getCipherSpecFromInteger(algorithmType: Int): String {
+    return when (algorithmType) {
+        0 -> "AES_128/GCM/NoPadding"
+        1 -> "AES_256/GCM/NoPadding"
+        2 -> "AES_256/CBC/PKCS7PADDING"
+        else -> ""
+    }
+}
+
+// Compute the hash, specified by @algorithm, of the file at path @srcFile. If an exception
+// occurs, returns null. If everything went well, returns the raw hash of @srcFile.
+fun hashFile(srcFile: String, algorithm: String): ByteArray? {
+    val buffer = ByteArray(BUFFER_SIZE)
+    try {
+        val digest = MessageDigest.getInstance(algorithm)
+        val fInputStream = FileInputStream(srcFile)
+        var length: Int
+
+        while (true) {
+            length = fInputStream.read()
+            if (length <= 0) break
+
+            // Only update the digest if we read more than 0 bytes
+            digest.update(buffer, 0, length)
+        }
+
+        fInputStream.close()
+
+        return digest.digest()
+    } catch (e: Exception) {
+        Log.e(TAG, "[hashFile]: " + e.stackTraceToString())
+        return null
+    }
+}
+
+// Encrypt the plaintext file at @src to @dest using the secret key @key and the IV @iv. The algorithm is chosen using @cipherAlgorithm. The file is additionally
+// hashed before and after encryption using the hash algorithm specified by @hashAlgorithm.
+fun encryptAndHash(src: String, dest: String, key: ByteArray, iv: ByteArray, cipherAlgorithm: String, hashAlgorithm: String): HashMap<String, ByteArray>? {
+    val buffer = ByteArray(BUFFER_SIZE)
+    val secretKey = SecretKeySpec(key, cipherAlgorithm)
+    try {
+        val digest = MessageDigest.getInstance(hashAlgorithm)
+        val cipher = Cipher.getInstance(cipherAlgorithm)
+        cipher.init(Cipher.ENCRYPT_MODE, secretKey, IvParameterSpec(iv))
+
+        val fileInputStream = FileInputStream(src)
+        val fileOutputStream = HashedFileOutputStream(dest, hashAlgorithm)
+        val cipherOutputStream = CipherOutputStream(fileOutputStream, cipher)
+
+        var length: Int
+        while (true) {
+            length = fileInputStream.read(buffer)
+            if (length <= 0) break
+
+            digest.update(buffer, 0, length)
+            cipherOutputStream.write(buffer, 0, length)
+        }
+
+        // Flush and close
+        cipherOutputStream.flush()
+        cipherOutputStream.close()
+        fileInputStream.close()
+
+        return hashMapOf(
+            "plaintextHash" to digest.digest(),
+            "ciphertextHash" to fileOutputStream.digest(),
+        )
+    } catch (e: Exception) {
+        Log.e(TAG, "[encryptAndHash]: " + e.stackTraceToString())
+        return null
+    }
+}
+
+// Decrypt the ciphertext file at @src to @dest using the secret key @key and the IV @iv. The algorithm is chosen using @cipherAlgorithm. The file is additionally
+// hashed before and after decryption using the hash algorithm specified by @hashAlgorithm.
+fun decryptAndHash(src: String, dest: String, key: ByteArray, iv: ByteArray, cipherAlgorithm: String, hashAlgorithm: String): HashMap<String, ByteArray>? {
+    // Shamelessly stolen from https://github.com/hugo-pcl/native-crypto-flutter/pull/3
+    val buffer = ByteArray(BUFFER_SIZE)
+    val secretKey = SecretKeySpec(key, cipherAlgorithm)
+    try {
+        val digest = MessageDigest.getInstance(hashAlgorithm)
+        val cipher = Cipher.getInstance(cipherAlgorithm)
+        cipher.init(Cipher.ENCRYPT_MODE, secretKey, IvParameterSpec(iv))
+
+        val fileInputStream = FileInputStream(src)
+        val fileOutputStream = HashedFileOutputStream(dest, hashAlgorithm)
+        val cipherOutputStream = CipherOutputStream(fileOutputStream, cipher)
+
+        // Read, decrypt, and hash until we read 0 bytes
+        var length: Int
+        while (true) {
+            length = fileInputStream.read(buffer)
+            if (length <= 0) break
+
+            digest.update(buffer, 0, length)
+            cipherOutputStream.write(buffer, 0, length)
+        }
+
+        // Flush
+        cipherOutputStream.flush()
+        cipherOutputStream.close()
+        fileInputStream.close()
+
+        return hashMapOf(
+            "plaintextHash" to digest.digest(),
+            "ciphertextHash" to fileOutputStream.digest(),
+        )
+    } catch (e: Exception) {
+        Log.e(TAG, "[hashAndDecrypt]: " + e.stackTraceToString())
+        return null
+    }
+}

packages/moxplatform_android/android/src/main/java/me/polynom/moxplatform_android/HashedFileOutputStream.java

@@ -1,34 +0,0 @@
-package me.polynom.moxplatform_android;
-
-import java.io.FileNotFoundException;
-import java.io.FileOutputStream;
-import java.io.IOException;
-import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
-
-public class HashedFileOutputStream extends FileOutputStream {
-    public MessageDigest digest;
-
-    public HashedFileOutputStream(String name, String hashSpec) throws FileNotFoundException, NoSuchAlgorithmException {
-        super(name);
-
-        digest = MessageDigest.getInstance(hashSpec);
-    }
-
-    @Override
-    public void write(byte[] b, int off, int len) throws IOException {
-        super.write(b, off, len);
-
-        digest.update(b, off, len);
-    }
-
-    public String getHexHash() {
-        StringBuffer result = new StringBuffer();
-        for (byte b : digest.digest()) result.append(Integer.toString((b & 0xff) + 0x100, 16).substring(1));
-        return result.toString();
-    }
-
-    public byte[] getHash() {
-        return digest.digest();
-    }
-}

packages/moxplatform_android/android/src/main/java/me/polynom/moxplatform_android/MoxplatformAndroidPlugin.java

@@ -1,6 +1,7 @@
 package me.polynom.moxplatform_android;
 
 import static me.polynom.moxplatform_android.RecordSentMessageKt.recordSentMessage;
+import static me.polynom.moxplatform_android.CryptoKt.*;
 
 import android.app.ActivityManager;
 import android.content.BroadcastReceiver;
@@ -8,28 +9,17 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.SharedPreferences;
-import android.graphics.Bitmap;
-import android.graphics.BitmapFactory;
-import android.graphics.drawable.Icon;
-import android.os.Build;
 import android.util.Log;
 
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
-import androidx.core.app.Person;
 import androidx.core.content.ContextCompat;
-import androidx.core.content.pm.ShortcutInfoCompat;
-import androidx.core.content.pm.ShortcutManagerCompat;
-import androidx.core.graphics.drawable.IconCompat;
 import androidx.localbroadcastmanager.content.LocalBroadcastManager;
 
 import java.io.FileInputStream;
 import java.security.MessageDigest;
 import java.util.ArrayList;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.List;
-import java.util.Set;
 
 import javax.crypto.Cipher;
 import javax.crypto.CipherOutputStream;
@@ -169,7 +159,16 @@ public class MoxplatformAndroidPlugin extends BroadcastReceiver implements Flutt
             int algorithm = (int) args.get(4);
             String hashSpec = (String) args.get(5);
 
-            result.success(encryptFile(src, dest, key, iv, algorithm, hashSpec));
+            result.success(
+                    encryptAndHash(
+                            src,
+                            dest,
+                            key,
+                            iv,
+                            getCipherSpecFromInteger(algorithm),
+                            hashSpec
+                    )
+            );
           }
         });
         encryptionThread.start();
@@ -186,7 +185,16 @@ public class MoxplatformAndroidPlugin extends BroadcastReceiver implements Flutt
             int algorithm = (int) args.get(4);
             String hashSpec = (String) args.get(5);
 
-            result.success(decryptFile(src, dest, key, iv, algorithm, hashSpec));
+            result.success(
+                    decryptAndHash(
+                            src,
+                            dest,
+                            key,
+                            iv,
+                            getCipherSpecFromInteger(algorithm),
+                            hashSpec
+                    )
+            );
           }
         });
         decryptionThread.start();
@@ -254,119 +262,4 @@ public class MoxplatformAndroidPlugin extends BroadcastReceiver implements Flutt
     Log.d(TAG, "Detached from service");
     this.service = null;
   }
-
-  private String getCipherSpecFromInteger(int algorithm) {
-    switch (algorithm) {
-      case 0: return "AES_128/GCM/NoPadding";
-      case 1: return "AES_256/GCM/NoPadding";
-      case 2: return "AES_256/CBC/PKCS7PADDING";
-      default:
-        Log.d(TAG, "INVALID ALGORITHM");
-        return "";
-    }
-  }
-
-  public HashMap<String, byte[]> encryptFile(String src, String dest, byte[] key, byte[] iv, int algorithm, String hashSpec) {
-    String spec = getCipherSpecFromInteger(algorithm);
-    if (spec.isEmpty()) {
-      return null;
-    }
-
-    // Shamelessly stolen from https://github.com/hugo-pcl/native-crypto-flutter/pull/3
-    byte[] buffer = new byte[8096];
-    SecretKeySpec sk = new SecretKeySpec(key, spec);
-    try {
-      MessageDigest md = MessageDigest.getInstance(hashSpec);
-      Cipher cipher = Cipher.getInstance(spec);
-      cipher.init(Cipher.ENCRYPT_MODE, sk, new IvParameterSpec(iv));
-      FileInputStream fin = new FileInputStream(src);
-      HashedFileOutputStream fout = new HashedFileOutputStream(dest, hashSpec);
-      CipherOutputStream cout = new CipherOutputStream(fout, cipher);
-      int len = 0;
-      int bufLen = 0;
-      while (true) {
-        len = fin.read(buffer);
-        if (len != 0 && len > 0) {
-          md.update(buffer, 0, len);
-          cout.write(buffer, 0, len);
-        } else {
-          break;
-        }
-      }
-      cout.flush();
-      cout.close();
-      fin.close();
-
-      return new HashMap<String, byte[]>() {{
-        put("plaintext_hash", md.digest());
-        put("ciphertext_hash", fout.getHash());
-      }};
-    } catch (Exception ex) {
-      Log.d(TAG, "ENC: " + ex.getMessage());
-      return null;
-    }
-  }
-
-  public HashMap<String, byte[]> decryptFile(String src, String dest, byte[] key, byte[] iv, int algorithm, String hashSpec) {
-    String spec = getCipherSpecFromInteger(algorithm);
-    if (spec.isEmpty()) {
-      return null;
-    }
-
-    // Shamelessly stolen from https://github.com/hugo-pcl/native-crypto-flutter/pull/3
-    byte[] buffer = new byte[8096];
-    SecretKeySpec sk = new SecretKeySpec(key, spec);
-    try {
-      Cipher cipher = Cipher.getInstance(spec);
-      cipher.init(Cipher.DECRYPT_MODE, sk, new IvParameterSpec(iv));
-      FileInputStream fin = new FileInputStream(src);
-      HashedFileOutputStream fout = new HashedFileOutputStream(dest, hashSpec);
-      CipherOutputStream cout = new CipherOutputStream(fout, cipher);
-      MessageDigest md = MessageDigest.getInstance(hashSpec);
-      Log.d(TAG, "Reading from " + src + ", writing to " + dest);
-      int len = 0;
-      while (true) {
-        len = fin.read(buffer);
-        if (len != 0 && len > 0) {
-          cout.write(buffer, 0, len);
-          md.update(buffer, 0, len);
-        } else {
-          break;
-        }
-      }
-      cout.flush();
-      cout.close();
-      fin.close();
-
-      return new HashMap<String, byte[]>() {{
-        put("plaintext_hash", md.digest());
-        put("ciphertext_hash", fout.getHash());
-      }};
-    } catch (Exception ex) {
-      Log.d(TAG, "DEC: " + ex.getMessage());
-      return null;
-    }
-  }
-
-  public byte[] hashFile(String src, String algorithm) {
-    byte[] buffer = new byte[8096];
-    try {
-      MessageDigest md = MessageDigest.getInstance(algorithm);
-      FileInputStream fin = new FileInputStream(src);
-      int len = 0;
-      while (true) {
-        len = fin.read(buffer);
-        if (len != 0 && len > 0) {
-          md.update(buffer, 0, len);
-        } else {
-          break;
-        }
-      }
-
-      return md.digest();
-    } catch (Exception ex) {
-      Log.d(TAG, "Hash: " + ex.getMessage());
-      return null;
-    }
-  }
 }

packages/moxplatform_android/lib/src/crypto_android.dart

@@ -28,8 +28,8 @@ class AndroidCryptographyImplementation extends CryptographyImplementation {
     // ignore: argument_type_not_assignable
     final result = Map<String, dynamic>.from(resultRaw);
     return CryptographyResult(
-      result['plaintext_hash']! as Uint8List,
+      result['plaintextHash']! as Uint8List,
-      result['ciphertext_hash']! as Uint8List,
+      result['ciphertextHash']! as Uint8List,
     );
   }
 
@@ -56,8 +56,8 @@ class AndroidCryptographyImplementation extends CryptographyImplementation {
     // ignore: argument_type_not_assignable
     final result = Map<String, dynamic>.from(resultRaw);
     return CryptographyResult(
-      result['plaintext_hash']! as Uint8List,
+      result['plaintextHash']! as Uint8List,
-      result['ciphertext_hash']! as Uint8List,
+      result['ciphertextHash']! as Uint8List,
     );
   }