support for chacha20 encryption.

lib/src/kdbx_format.dart

@@ -5,6 +5,7 @@ import 'dart:typed_data';
 
 import 'package:convert/convert.dart' as convert;
 import 'package:crypto/crypto.dart' as crypto;
+import 'package:cryptography/cryptography.dart' as cryptography;
 import 'package:kdbx/kdbx.dart';
 import 'package:kdbx/src/crypto/argon2.dart';
 import 'package:kdbx/src/crypto/key_encrypter_kdf.dart';
@@ -285,8 +286,8 @@ class KdbxBody extends KdbxNode {
       return result;
     } else if (cipherId == CryptoConsts.CIPHER_IDS[Cipher.chaCha20].uuid) {
       _logger.fine('We need chacha20');
-      // TODO can we combine this with _encryptV3?
-      throw UnsupportedError('Unsupported cipher chacha20 for kdbx 4.x');
+      return kdbxFile.kdbxFormat
+          .transformContentV4ChaCha20(header, compressedBytes, cipherKey);
     } else {
       throw UnsupportedError('Unsupported cipherId $cipherId');
     }
@@ -509,12 +510,21 @@ class KdbxFormat {
       return result;
     } else if (cipherId == CryptoConsts.CIPHER_IDS[Cipher.chaCha20].uuid) {
       _logger.fine('We need chacha20');
-      throw UnsupportedError('chacha20 not yet supported $cipherId');
+//      throw UnsupportedError('chacha20 not yet supported $cipherId');
+      return transformContentV4ChaCha20(header, encrypted, cipherKey);
     } else {
       throw UnsupportedError('Unsupported cipherId $cipherId');
     }
   }
 
+  Uint8List transformContentV4ChaCha20(
+      KdbxHeader header, Uint8List encrypted, Uint8List cipherKey) {
+    final encryptionIv = header.fields[HeaderFields.EncryptionIV].bytes;
+    final key = cryptography.SecretKey(cipherKey);
+    final nonce = cryptography.SecretKey(encryptionIv);
+    return cryptography.chacha20.decrypt(encrypted, key, nonce: nonce);
+  }
+
 //  Uint8List _transformDataV4Aes() {
 //  }
 

test/kdbx4_test.dart

@@ -88,6 +88,12 @@ void main() {
           Credentials.composite(ProtectedValue.fromString('asdf'), keyFile));
       expect(file.body.rootGroup.entries, hasLength(1));
     });
+    test('Reading chacha20', () async {
+      final data = await File('test/chacha20.kdbx').readAsBytes();
+      final file =
+          kdbxFormat.read(data, Credentials(ProtectedValue.fromString('asdf')));
+      expect(file.body.rootGroup.entries, hasLength(1));
+    });
   });
   group('Writing', () {
     test('Create and save', () {
@@ -98,22 +104,8 @@ void main() {
         header: KdbxHeader.createV4(),
       );
       final rootGroup = kdbx.body.rootGroup;
-      {
-        final entry = KdbxEntry.create(kdbx, rootGroup);
-        rootGroup.addEntry(entry);
-        entry.setString(KdbxKey('Username'), PlainValue('user1'));
-        entry.setString(
-            KdbxKey('Password'), ProtectedValue.fromString('LoremIpsum'));
-      }
-      {
-        final entry = KdbxEntry.create(kdbx, rootGroup);
-        rootGroup.addEntry(entry);
-        entry.setString(KdbxKey('Username'), PlainValue('user2'));
-        entry.setString(
-          KdbxKey('Password'),
-          ProtectedValue.fromString('Second Password'),
-        );
-      }
+      _createEntry(kdbx, rootGroup, 'user1', 'LoremIpsum');
+      _createEntry(kdbx, rootGroup, 'user2', 'Second Password');
       final saved = kdbx.save();
 
       final loadedKdbx = kdbxFormat.read(
@@ -126,5 +118,26 @@ void main() {
       final file =
           kdbxFormat.read(data, Credentials(ProtectedValue.fromString('asdf')));
     });
+    test('write chacha20', () async {
+      final data = await File('test/chacha20.kdbx').readAsBytes();
+      final file =
+          kdbxFormat.read(data, Credentials(ProtectedValue.fromString('asdf')));
+      expect(file.body.rootGroup.entries, hasLength(1));
+      _createEntry(file, file.body.rootGroup, 'user1', 'LoremIpsum');
+
+      // and try to write it.
+      final output = file.save();
+      expect(output, isNotNull);
+      File('test_output_chacha20.kdbx').writeAsBytesSync(output);
+    });
   });
 }
+
+KdbxEntry _createEntry(
+    KdbxFile file, KdbxGroup group, String username, String password) {
+  final entry = KdbxEntry.create(file, group);
+  group.addEntry(entry);
+  entry.setString(KdbxKey('UserName'), PlainValue(username));
+  entry.setString(KdbxKey('Password'), ProtectedValue.fromString(password));
+  return entry;
+}