Imlement generating of keyfiles (keyx format)

lib/src/credentials/keyfile.dart

@@ -3,15 +3,23 @@ import 'dart:typed_data';
 
 import 'package:collection/collection.dart' show IterableExtension;
 import 'package:convert/convert.dart' as convert;
+import 'package:crypto/crypto.dart' as crypto;
 import 'package:kdbx/src/credentials/credentials.dart';
 import 'package:kdbx/src/crypto/protected_value.dart';
-import 'package:xml/xml.dart' as xml;
-import 'package:crypto/crypto.dart' as crypto;
-
+import 'package:kdbx/src/utils/byte_utils.dart';
 import 'package:logging/logging.dart';
+import 'package:meta/meta.dart';
+import 'package:xml/xml.dart' as xml;
 
 final _logger = Logger('keyfile');
 
+const _nodeVersion = 'Version';
+const _nodeKey = 'Key';
+const _nodeData = 'Data';
+const _nodeMeta = 'Meta';
+const _nodeKeyFile = 'KeyFile';
+const _nodeHash = 'Hash';
+
 class KeyFileCredentials implements CredentialsPart {
   factory KeyFileCredentials(Uint8List keyFileContents) {
     try {
@@ -22,13 +30,27 @@ class KeyFileCredentials implements CredentialsPart {
       }
       final xmlContent = xml.XmlDocument.parse(keyFileAsString);
       final metaVersion =
-          xmlContent.findAllElements('Version').singleOrNull?.text;
-      final key = xmlContent.findAllElements('Key').single;
-      final dataString = key.findElements('Data').single;
+          xmlContent.findAllElements(_nodeVersion).singleOrNull?.text;
+      final key = xmlContent.findAllElements(_nodeKey).single;
+      final dataString = key.findElements(_nodeData).single;
       final encoded = dataString.text.replaceAll(RegExp(r'\s'), '');
       Uint8List dataBytes;
       if (metaVersion != null && metaVersion.startsWith('2.')) {
         dataBytes = convert.hex.decode(encoded) as Uint8List;
+        assert((() {
+          final hash = dataString.getAttribute(_nodeHash);
+          if (hash == null) {
+            throw const FormatException('Keyfile must contain a hash.');
+          }
+          final expectedHashBytes = convert.hex.decode(hash);
+          final actualHash =
+              crypto.sha256.convert(dataBytes).bytes.sublist(0, 4) as Uint8List;
+          if (!ByteUtils.eq(expectedHashBytes, actualHash)) {
+            throw const FormatException(
+                'Corrupted keyfile. Hash does not match');
+          }
+          return true;
+        })());
       } else {
         dataBytes = base64.decode(encoded);
       }
@@ -42,6 +64,13 @@ class KeyFileCredentials implements CredentialsPart {
     }
   }
 
+  /// Creates a new random (32 bytes) keyfile value.
+  factory KeyFileCredentials.random() => KeyFileCredentials._(
+      ProtectedValue.fromBinary(ByteUtils.randomBytes(32)));
+
+  factory KeyFileCredentials.fromBytes(Uint8List bytes) =>
+      KeyFileCredentials._(ProtectedValue.fromBinary(bytes));
+
   KeyFileCredentials._(this._keyFileValue);
 
   static final RegExp _hexValuePattern =
@@ -54,6 +83,56 @@ class KeyFileCredentials implements CredentialsPart {
     return _keyFileValue.binaryValue;
 //    return crypto.sha256.convert(_keyFileValue.binaryValue).bytes as Uint8List;
   }
+
+  /// Generates a `.keyx` file as described for Keepass keyfile:
+  /// https://keepass.info/help/base/keys.html#keyfiles
+  Uint8List toXmlV2() {
+    return utf8.encode(toXmlV2String()) as Uint8List;
+  }
+
+  /// Generates a `.keyx` file as described for Keepass keyfile:
+  /// https://keepass.info/help/base/keys.html#keyfiles
+  @visibleForTesting
+  String toXmlV2String() {
+    final hash =
+        (crypto.sha256.convert(_keyFileValue.binaryValue).bytes as Uint8List)
+            .sublist(0, 4);
+    final hashHexString = hexFormatLikeKeepass(convert.hex.encode(hash));
+    final keyHexString =
+        hexFormatLikeKeepass(convert.hex.encode(_keyFileValue.binaryValue));
+
+    final builder = xml.XmlBuilder()
+      ..processing('xml', 'version="1.0" encoding="utf-8"');
+    builder.element(_nodeKeyFile, nest: () {
+      builder.element(_nodeMeta, nest: () {
+        builder.element(_nodeVersion, nest: () {
+          builder.text('2.0');
+        });
+      });
+      builder.element(_nodeKey, nest: () {
+        builder.element(_nodeData, nest: () {
+          builder.attribute(_nodeHash, hashHexString);
+          builder.text(keyHexString);
+        });
+      });
+    });
+    return builder.buildDocument().toXmlString(pretty: true);
+  }
+
+  /// keypass has all-uppercase letters in pairs of 4 bytes (8 characters).
+  @visibleForTesting
+  static String hexFormatLikeKeepass(final String hexString) {
+    final hex = hexString.toUpperCase();
+    const _groups = 8;
+    final remaining = hex.length % _groups;
+    return [
+      for (var i = 0; i < hex.length ~/ _groups; i++)
+        hex.substring(i * _groups, i * _groups + _groups),
+      if (remaining != 0) hex.substring(hex.length - remaining)
+    ].join(' ');
+    // range(0, hexString.length / 8).map((i) => hexString.substring(i*_groups, i*_groups + _groups));
+    // hexString.toUpperCase().chara
+  }
 }
 
 class KeyFileComposite implements Credentials {

lib/src/crypto/protected_value.dart

@@ -46,7 +46,7 @@ class ProtectedValue implements StringValue {
     return ProtectedValue(_xor(value, salt), salt);
   }
 
-  static final random = Random.secure();
+  static final _random = Random.secure();
 
   final Uint8List _value;
   final Uint8List _salt;
@@ -57,7 +57,7 @@ class ProtectedValue implements StringValue {
 
   static Uint8List _randomBytes(int length) {
     return Uint8List.fromList(
-        List.generate(length, (i) => random.nextInt(0xff)));
+        List.generate(length, (i) => _random.nextInt(0xff)));
   }
 
   static Uint8List _xor(Uint8List a, Uint8List b) {

test/keyfile/keyfile_create_test.dart

@@ -0,0 +1,45 @@
+import 'dart:typed_data';
+
+import 'package:kdbx/kdbx.dart';
+import 'package:logging/logging.dart';
+import 'package:quiver/iterables.dart';
+import 'package:test/expect.dart';
+import 'package:test/scaffolding.dart';
+
+import '../internal/test_utils.dart';
+
+final _logger = Logger('keyfile_create_test');
+
+void main() {
+  // ignore: unused_local_variable
+  final testUtils = TestUtil.instance;
+  final exampleBytes = Uint8List.fromList(
+      range(0, 16).expand((element) => [0xca, 0xfe]).toList());
+  group('creating keyfile', () {
+    test('Create keyfile', () {
+      final keyFile = KeyFileCredentials.fromBytes(exampleBytes);
+      final output = keyFile.toXmlV2String();
+      _logger.info(output);
+      expect(output, contains('Hash="4CA06E29"'));
+      expect(output, contains('CAFECAFE CAFECAFE'));
+    });
+    test('hex format', () {
+      final toTest = {
+        'abcd': 'ABCD',
+        'abcdefgh': 'ABCDEFGH',
+        'abcdef': 'ABCDEF',
+        '1234567812345678': '12345678 12345678',
+        '12345678123456': '12345678 123456',
+      };
+      for (final e in toTest.entries) {
+        expect(KeyFileCredentials.hexFormatLikeKeepass(e.key), e.value);
+      }
+    });
+    test('create and load', () {
+      final keyFile = KeyFileCredentials.fromBytes(exampleBytes);
+      final output = keyFile.toXmlV2();
+      final read = KeyFileCredentials(output);
+      expect(read.getBinary(), equals(exampleBytes));
+    });
+  });
+}