Fix OutOfMemoryError on large files

lib/src/cipher.dart

@@ -1,4 +1,4 @@
-// Copyright (c) 2020
+// Copyright (c) 2021
 // Author: Hugo Pointcheval
 
 import 'dart:typed_data';
@@ -52,14 +52,23 @@ abstract class Cipher {
 ///
 /// It's the result of an encryption.
 abstract class CipherText {
-  /// Returns the standard algorithm name used for this ciphertext
+  /// Returns the standard algorithm name used for this ciphertext.
   CipherAlgorithm get algorithm;
 
-  /// Returns the data of this ciphertext
-  Uint8List get bytes;
+  /// Returns the data of this ciphertext (in chunks).
+  List<Uint8List> get bytes;
 
-  /// Returns the IV of this cipertext
-  Uint8List get iv;
+  /// Returns the IV of this cipertext (in chunks).
+  List<Uint8List> get iv;
+
+  /// Returns the chunk number of this cipherText.
+  int get size;
+
+  /// Returns this ciphertext in simple Byte Array format.
+  Uint8List encode();
+
+  /// Transforms a simple Byte Array to a NativeCrypto cipherText.
+  void decode(Uint8List src);
 }
 
 /// Represents a pair of [BlockCipherMode] and [Padding]

lib/src/sym/AES.dart

@@ -1,8 +1,10 @@
-// Copyright (c) 2020
+// Copyright (c) 2021
 // Author: Hugo Pointcheval
 
 import 'dart:typed_data';
 
+import 'package:native_crypto/native_crypto.dart';
+
 import '../cipher.dart';
 import '../exceptions.dart';
 import '../key.dart';
@@ -81,9 +83,28 @@ class AESCipher implements Cipher {
     } else if (_sk == null || _sk.isEmpty) {
       throw CipherInitException('Invalid key size.');
     }
-    List<Uint8List> c =
-        await Platform().encrypt(data, _sk.encoded, algorithm, _params);
-    return AESCipherText(c[0], c[1]);
+    Uint8List dataToEncrypt;
+    int maxSize = 33554432;
+    AESCipherText cipherText = AESCipherText.empty();
+    // If data is bigger than 32mB -> split in chunks
+    if (data.length > maxSize) {
+      int chunkNb = (data.length / maxSize).ceil();
+      for (var i = 0; i < chunkNb; i++) {
+        if (i < (chunkNb - 1)) {
+          dataToEncrypt = data.sublist(i * maxSize, (i + 1) * maxSize);
+        } else {
+          dataToEncrypt = data.sublist(i * maxSize);
+        }
+        List<Uint8List> c = await Platform()
+            .encrypt(dataToEncrypt, _sk.encoded, algorithm, _params);
+        cipherText.append(c[0], c[1]);
+      }
+    } else {
+      List<Uint8List> c =
+          await Platform().encrypt(data, _sk.encoded, algorithm, _params);
+      cipherText.append(c[0], c[1]);
+    }
+    return cipherText;
   }
 
   @override
@@ -96,29 +117,106 @@ class AESCipher implements Cipher {
       throw CipherInitException('Cipher not properly initialized.');
     } else if (_sk == null || _sk.isEmpty) {
       throw CipherInitException('Invalid key size.');
+    } else if (cipherText.bytes.length != cipherText.iv.length) {
+      throw DecryptionException(
+          "This cipher text's bytes chunks length is not the same as iv chunks length");
     }
-    List<Uint8List> payload = [cipherText.bytes, cipherText.iv];
-    Uint8List d =
-        await Platform().decrypt(payload, _sk.encoded, algorithm, _params);
-    return d;
+
+    BytesBuilder decryptedData = BytesBuilder();
+    if (cipherText.size > 1) {
+      for (var i = 0; i < cipherText.size; i++) {
+        List<Uint8List> payload = [cipherText.bytes[i], cipherText.iv[i]];
+        Uint8List d =
+            await Platform().decrypt(payload, _sk.encoded, algorithm, _params);
+        decryptedData.add(d);
+      }
+    } else {
+      List<Uint8List> payload = [cipherText.bytes[0], cipherText.iv[0]];
+      Uint8List d =
+          await Platform().decrypt(payload, _sk.encoded, algorithm, _params);
+      decryptedData.add(d);
+    }
+    return decryptedData.toBytes();
   }
 }
 
 class AESCipherText implements CipherText {
-  Uint8List _bytes;
-  Uint8List _iv;
+  List<Uint8List> _bytes;
+  List<Uint8List> _iv;
 
   @override
   CipherAlgorithm get algorithm => CipherAlgorithm.AES;
 
   @override
-  Uint8List get bytes => _bytes;
+  List<Uint8List> get bytes => _bytes;
 
   @override
-  Uint8List get iv => _iv;
+  List<Uint8List> get iv => _iv;
+
+  @override
+  int get size => _bytes.length;
 
   AESCipherText(Uint8List bytes, Uint8List iv) {
+    _bytes = List.from([bytes]);
+    _iv = List.from([iv]);
+  }
+
+  AESCipherText.from(List<Uint8List> bytes, List<Uint8List> iv) {
     _bytes = bytes;
     _iv = iv;
   }
+
+  AESCipherText.empty() {
+    _bytes = <Uint8List>[];
+    _iv = <Uint8List>[];
+  }
+
+  void append(Uint8List bytes, Uint8List iv) {
+    _bytes.add(bytes);
+    _iv.add(iv);
+  }
+
+  /// Returns this ciphertext in [Uint8List] format.
+  ///
+  /// Encoding
+  /// --------
+  /// Uint8List encoding is : IV_1 + M_1 + IV_2 + M_2 + ... + IV_n + M_n
+  ///
+  /// Where **IV_k** is the IV of the cipher text **M_k**
+  ///
+  /// IV is **always** 16 bytes long, And the **M** are all max
+  /// size (of 33 554 480 bytes) except the last one which is shorter than the others.
+  Uint8List encode() {
+    BytesBuilder builder = BytesBuilder();
+    for (var i = 0; i < size; i++) {
+      builder.add(_iv[i]);
+      builder.add(_bytes[i]);
+    }
+
+    return builder.toBytes();
+  }
+
+  /// Transforms a [Uint8List] to a *NativeCrypto* cipherText.
+  ///
+  /// Decoding
+  /// --------
+  /// See the list as a chain of chunks (IV and Messages)
+  /// `[IV][MESSAGE][IV][MESSAGE] ... [IV][MESSA...]`
+  ///
+  /// Chunk length is IV length + Message length = 16 + 33 554 480 bytes
+  void decode(Uint8List src) {
+    ByteBuffer buffer = src.buffer;
+
+    int chunkSize = 16 + 33554480;
+    int chunkNb = (buffer.lengthInBytes / chunkSize).ceil();
+
+    for (var i = 0; i < chunkNb; i++) {
+      _iv.add(buffer.asUint8List(i * chunkSize, 16));
+      if (i < (chunkNb - 1)) {
+        _bytes.add(buffer.asUint8List(16 + i * chunkSize, 33554480));
+      } else {
+        _bytes.add(buffer.asUint8List(16 + i * chunkSize));
+      }
+    }
+  }
 }