cryptorHeader for new cryptoModule

pubnub · Sep 27, 2023 · 6378d0c · 6378d0c
1 parent 639bb30
commit 6378d0c
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diff --git a/pubnub/lib/src/crypto/crypto.dart b/pubnub/lib/src/crypto/crypto.dart
@@ -6,6 +6,90 @@ import 'dart:typed_data' show Uint8List;
 import 'package:pubnub/core.dart';
 import 'encryption_mode.dart';
 
+class CryptorHeader {
+  static const SENTINEL = 'PNED';
+  static const LEGACY_IDENTIFIER = '';
+  static const IDENTIFIER_LENGTH = 4;
+  static const MAX_VERSION = 1;
+
+  static CryptorHeaderV1? from(String id, List<int> metadata) {
+    if (id == LEGACY_IDENTIFIER) return null;
+    return CryptorHeaderV1(id, metadata.length);
+  }
+
+  static CryptorHeaderV1? tryParse(List<int> encryptedData) {
+    List<int> sentinel;
+    var version;
+    if (encryptedData.length >= 4) {
+      sentinel = encryptedData.sublist(0,4).toList();
+      if (utf8.decode(sentinel) != SENTINEL) return null;
+    }
+
+    if (encryptedData.length >= 5) {
+      version = encryptedData[4];
+    } else {
+      throw PubNubException('decryption error');
+    }
+    if (version > MAX_VERSION) throw PubNubException('unknown cryptor');
+
+    var identifier;
+    var pos = 5 + IDENTIFIER_LENGTH;
+    if (encryptedData.length >= pos) {
+      identifier = encryptedData.sublist(5, pos).toList();
+    } else {
+      throw PubNubException('decryption error');
+    }
+    var metadataLength;
+    if (encryptedData.length > pos + 1) {
+      metadataLength = encryptedData[pos];
+    }
+    pos += 1;
+    if (metadataLength == 255 && encryptedData.length >= pos + 2) {
+      metadataLength = encryptedData
+          .sublist(pos, pos + 2)
+          .fold<int>(0, (acc, el) => (acc << 8) + el);
+    }
+    return CryptorHeaderV1(utf8.decode(identifier), metadataLength);
+  }
+}
+
+class CryptorHeaderV1 {
+  static const VERSION = 1;
+  final String _identifier;
+  final int _metadataLength;
+
+  CryptorHeaderV1(this._identifier, this._metadataLength);
+
+  String get identifier => _identifier;
+  int get metadataLength => _metadataLength;
+
+  int get length {
+    return (CryptorHeader.SENTINEL.length +
+        1 +
+        CryptorHeader.IDENTIFIER_LENGTH +
+        (_metadataLength < 225 ? 1 : 3) +
+        _metadataLength);
+  }
+
+  List<int> get data {
+    var pos = 0;
+    var header = List<int>.filled(length, 0);
+    header.setAll(pos, CryptorHeader.SENTINEL.codeUnits);
+    pos += CryptorHeader.SENTINEL.length;
+    header[pos] = VERSION;
+    pos++;
+    header.setAll(pos, _identifier.codeUnits);
+    pos+=CryptorHeader.IDENTIFIER_LENGTH;
+    var metadataLength = this.metadataLength;
+    if (metadataLength < 255){
+      header[pos] = metadataLength;
+    } else {
+      header.setAll(pos, [255, metadataLength >> 8, metadataLength & 0xff]);
+    }
+    return header;
+  }
+}
+
 /// Configuration used in cryptography.
 class CryptoConfiguration {
   /// Encryption mode used.

diff --git a/pubnub/test/unit/crypto/crypto_test.dart b/pubnub/test/unit/crypto/crypto_test.dart
@@ -22,5 +22,14 @@ void main() {
 
       expect(result, equals(plaintext));
     });
+
+    test('cryptoHeader tryParse/data from encrypted text', () async {
+      var encryptedDataWithHeader = 'PNEDACRH�_�ƿ';
+      var headerData = [80, 78, 69, 68, 1, 65, 67, 82, 72, 16];
+      var expectedBytes = [...headerData, ...List<int>.filled(16, 0)];
+
+      CryptorHeaderV1? header = CryptorHeader.tryParse(encryptedDataWithHeader.codeUnits);
+      expect(header!.data, equals(expectedBytes));
+    });
   });
 }