From 51d10362e9eaff8fafb73844ff63cb05d1621e61 Mon Sep 17 00:00:00 2001
From: Pointcheval Hugo <hugo@gitlab.pointcheval.fr>
Date: Thu, 17 Dec 2020 22:10:27 +0100
Subject: [PATCH] Add AES cipher implementation

---
 lib/src/sym/AES.dart | 112 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 lib/src/sym/AES.dart

diff --git a/lib/src/sym/AES.dart b/lib/src/sym/AES.dart
new file mode 100644
index 0000000..8a9ea4b
--- /dev/null
+++ b/lib/src/sym/AES.dart
@@ -0,0 +1,112 @@
+// Copyright (c) 2020
+// Author: Hugo Pointcheval
+
+import 'dart:typed_data';
+
+import '../cipher.dart';
+import '../exceptions.dart';
+import '../key.dart';
+import '../platform.dart';
+
+/// Defines all available key sizes.
+enum AESKeySize { bits128, bits192, bits256 }
+
+class AESCipher implements Cipher {
+  SecretKey _sk;
+  CipherParameters _params;
+  bool _isInit;
+
+  List<CipherParameters> _supportedCipherParams = [
+    CipherParameters(BlockCipherMode.CBC, Padding.PKCS5),
+  ];
+
+  @override
+  String get algorithm => "AES";
+
+  @override
+  SecretKey get secretKey => _sk;
+
+  @override
+  CipherParameters get parameters => _params;
+
+  @override
+  bool get isInitialized => _isInit;
+
+  /// Creates an AES cipher with specified secretKey and mode/padding
+  AESCipher(SecretKey secretKey, CipherParameters parameters) {
+    if (secretKey.algorithm != "AES") {
+      throw CipherInitException("Invalid key type: " + secretKey.algorithm);
+    } else if (!_supportedCipherParams.contains(parameters)) {
+      throw CipherInitException("Invalid cipher parameters.");
+    }
+    _params = parameters;
+    _isInit = true;
+  }
+
+  /// Generates a secret key of specified size, then creates an AES cipher.
+  AESCipher.generate(AESKeySize size, CipherParameters parameters) {
+    Map<AESKeySize, int> _supportedSizes = {
+      AESKeySize.bits128: 128,
+      AESKeySize.bits192: 192,
+      AESKeySize.bits256: 256
+    };
+
+    if (!_supportedCipherParams.contains(parameters)) {
+      throw CipherInitException("Invalid cipher parameters.");
+    } else if (!_supportedSizes.containsKey(size)) {
+      throw CipherInitException("Invalid key size.");
+    }
+
+    _sk = SecretKey.generate("AES", _supportedSizes[size]);
+    _params = parameters;
+    _isInit = true;
+  }
+
+  @override
+  Future<CipherText> encrypt(Uint8List data) async {
+    if (!_isInit) {
+      throw CipherInitException('Cipher not properly initialized.');
+    } else if (_sk == null || _sk.isEmpty) {
+      throw CipherInitException('Invalid key size.');
+    }
+    List<Uint8List> c =
+        await Platform().encrypt(data, _sk.encoded, "AES", _params);
+    return AESCipherText(c[0], c[1]);
+  }
+
+  @override
+  Future<Uint8List> decrypt(CipherText cipherText) async {
+    if (cipherText.algorithm != "AES") {
+      throw DecryptionException("This cipher text's algorithm is not AES: " +
+          cipherText.algorithm +
+          "\nYou must use an AESCipherText.");
+    } else if (!_isInit) {
+      throw CipherInitException('Cipher not properly initialized.');
+    } else if (_sk == null || _sk.isEmpty) {
+      throw CipherInitException('Invalid key size.');
+    }
+    List<Uint8List> payload = [cipherText.bytes, cipherText.iv];
+    Uint8List d =
+        await Platform().decrypt(payload, _sk.encoded, "AES", _params);
+    return d;
+  }
+}
+
+class AESCipherText implements CipherText {
+  Uint8List _bytes;
+  Uint8List _iv;
+
+  @override
+  String get algorithm => "AES";
+
+  @override
+  Uint8List get bytes => _bytes;
+
+  @override
+  Uint8List get iv => _iv;
+
+  AESCipherText(Uint8List bytes, Uint8List iv) {
+    _bytes = bytes;
+    _iv = iv;
+  }
+}