Update to Argon2

Author: AaronFeickert

lib/secure_storage.dart

@@ -63,8 +63,14 @@
 import 'dart:convert';
 import 'dart:math';
 import 'dart:typed_data';
+import 'package:argon2/argon2.dart';
 import 'package:cryptography/cryptography.dart';
 
+/// Return a list of all known versions
+List<int> getVersions() {
+  return [1, 2, 3];
+}
+
 /// Get the PBKDF iterations for this version
 /// https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html#pbkdf2
 int getPbkdfIterations(int version) {
@@ -78,6 +84,17 @@ int getPbkdfIterations(int version) {
   }
 }
 
+/// Get the Argon2id memory parameter for this version
+/// https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html#argon2id
+int getArgon2Memory(int version) {
+  switch (version) {
+    case 3:
+      return 47104;
+    default:
+      throw VersionError();
+  }
+}
+
 /// Constants that should not be changed without good reason
 const int saltLength = 16; // in bytes
 const String dataKeyDomain = 'STACK_WALLET_DATA_KEY';
@@ -130,7 +147,14 @@ class StorageCryptoHandler {
     final salt = _randomBytes(saltLength);
 
     // Use the passphrase and salt to derive the main key with the PBKDF
-    final mainKey = await _pbkdf2(salt, _stringToBytes(passphrase), version);
+    Uint8List mainKey = Uint8List(Xchacha20.poly1305Aead().secretKeyLength);
+    if (version == 1 || version == 2) {
+      mainKey = await _pbkdf2(salt, _stringToBytes(passphrase), version);
+    } else if (version == 3) {
+      mainKey = await _argon2id(salt, _stringToBytes(passphrase), version);
+    } else {
+      throw VersionError();
+    }
 
     // Generate a random data key
     final dataKey = _randomBytes(Xchacha20.poly1305Aead().secretKeyLength);
@@ -151,7 +175,14 @@ class StorageCryptoHandler {
     Uint8List encryptedDataKey = keyBlobBytes.sublist(saltLength);
 
     // Derive the candidate main key
-    final Uint8List mainKey = await _pbkdf2(salt, _stringToBytes(passphrase), version);
+    Uint8List mainKey = Uint8List(Xchacha20.poly1305Aead().secretKeyLength);
+    if (version == 1 || version == 2) {
+      mainKey = await _pbkdf2(salt, _stringToBytes(passphrase), version);
+    } else if (version == 3) {
+      mainKey = await _argon2id(salt, _stringToBytes(passphrase), version);
+    } else {
+      throw VersionError();
+    }
 
     // Determine if the main key is valid against the encrypted data key
     try {
@@ -183,7 +214,13 @@ class StorageCryptoHandler {
     _salt = _randomBytes(saltLength);
 
     // Use the passphrase and salt to derive the main key with the PBKDF
-    _mainKey = await _pbkdf2(_salt, _stringToBytes(passphrase), version);
+    if (version == 1 || version == 2) {
+      _mainKey = await _pbkdf2(_salt, _stringToBytes(passphrase), version);
+    } else if (version == 3) {
+      _mainKey = await _argon2id(_salt, _stringToBytes(passphrase), version);
+    } else {
+      throw VersionError();
+    }
   }
 
   /// Get the key blob, which is safe to store
@@ -357,6 +394,25 @@ Future<Uint8List> _pbkdf2(Uint8List salt, Uint8List passphrase, int version) asy
   return Uint8List.fromList(mainKeyBytes);
 }
 
+/// Argon2id
+Future<Uint8List> _argon2id(Uint8List salt, Uint8List passphrase, int version) async {
+  final parameters = Argon2Parameters(
+    Argon2Parameters.ARGON2_id,
+    salt,
+    version: Argon2Parameters.ARGON2_VERSION_13,
+    iterations: 1,
+    lanes: 1,
+    memory: getArgon2Memory(version),
+  );
+  final Argon2BytesGenerator argon2 = Argon2BytesGenerator();
+  argon2.init(parameters);
+
+  var derivedKeyBytes = Uint8List(Xchacha20.poly1305Aead().secretKeyLength);
+  argon2.generateBytes(passphrase, derivedKeyBytes);
+
+  return derivedKeyBytes;
+}
+
 /// XChaCha20-Poly1305 encryption
 Future<SecretBox> _xChaCha20Poly1305Encrypt(Uint8List key, Uint8List nonce, Uint8List data, Uint8List aad) async {
   final Xchacha20 aead = Xchacha20.poly1305Aead();

lib/stack_wallet_backup.dart

@@ -29,6 +29,7 @@
 import 'dart:convert';
 import 'dart:math';
 import 'dart:typed_data';
+import 'package:argon2/argon2.dart';
 import 'package:collection/collection.dart';
 import 'package:cryptography/cryptography.dart';
 import 'package:tuple/tuple.dart';
@@ -84,6 +85,24 @@ List<VersionParameters> getAllVersions() {
     Blake2b().hashLengthInBytes 
   ));
 
+  // Version 3 uses Argon2id, XChaCha20-Poly1305, and Blake2b
+  version = 3;
+  aad = protocol + version.toString();
+  const int owaspRecommendedArgon2idMemoryVersion3 = 47104; // OWASP recommendation: https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html#argon2id
+  const int argon2idSaltLength = 16; // Take that, rainbow tables!
+  versions.add(VersionParameters(
+    version,
+    (passphrase) => _argon2id(passphrase, Uint8List.fromList(utf8.encode(aad)), owaspRecommendedArgon2idMemoryVersion3, Xchacha20.poly1305Aead().secretKeyLength),
+    (adk, salt) => _argon2id(adk, salt, owaspRecommendedArgon2idMemoryVersion3, Xchacha20.poly1305Aead().secretKeyLength),
+    (key, nonce, plaintext) => _xChaCha20Poly1305Encrypt(key, nonce, plaintext, aad),
+    (key, blob) => _xChaCha20Poly1305Decrypt(key, blob, aad),
+    (data) => _blake2b(data, aad),
+    argon2idSaltLength,
+    Xchacha20.poly1305Aead().nonceLength,
+    Poly1305().macLength,
+    Blake2b().hashLengthInBytes 
+  ));
+
   return versions;
 }
 
@@ -239,6 +258,25 @@ Future<Uint8List> _pbkdf2(Uint8List passphrase, Uint8List salt, MacAlgorithm mac
   return Uint8List.fromList(derivedKeyBytes);
 }
 
+/// Argon2id
+Future<Uint8List> _argon2id(Uint8List passphrase, Uint8List salt, int memory, int derivedKeyLength) async {
+  final parameters = Argon2Parameters(
+    Argon2Parameters.ARGON2_id,
+    salt,
+    version: Argon2Parameters.ARGON2_VERSION_13,
+    iterations: 1,
+    lanes: 1,
+    memory: memory,
+  );
+  final Argon2BytesGenerator argon2 = Argon2BytesGenerator();
+  argon2.init(parameters);
+
+  var derivedKeyBytes = Uint8List(derivedKeyLength);
+  argon2.generateBytes(passphrase, derivedKeyBytes);
+
+  return derivedKeyBytes;
+}
+
 //
 // AEAD functions
 //

pubspec.yaml

@@ -8,6 +8,7 @@ environment:
   flutter: ">=3.10.2"
 
 dependencies:
+  argon2: ^1.0.1
   collection: ^1.16.0
   cryptography: ^2.0.5
   flutter:

test/secure_storage_test.dart

@@ -29,30 +29,37 @@ const int saltLength = 16; // must match the library's value, which is private
 
 void main() {
   /// Version-independent operations
-  test ('upgrade, version 1 to 2', () async {
-    // Create a storage handler with version 1
-    const String passphrase = 'test';
-    StorageCryptoHandler handler = await StorageCryptoHandler.fromNewPassphrase(passphrase, 1);
-
-    // Encrypt some data
-    const String name = 'secret_data_that_should_not_be_padded';
-    const value = 'the secret data not to pad';
-    final String encryptedValue = await handler.encryptValue(name, value);
-
-    // Upgrade to version 2 (in this case, using the same passphrase) and get the new key blob
-    await handler.resetPassphrase(passphrase, 2);
-    final String keyBlob = await handler.getKeyBlob();
-
-    // Now we can recover the handler with the new passphrase
-    handler = await StorageCryptoHandler.fromExisting(passphrase, keyBlob, 2);
-
-    // Confirm that decryption works as expected
-    final String decryptedValue = await handler.decryptValue(name, encryptedValue);
-    expect(decryptedValue, value);
-  });
+  for (int oldVersion in getVersions()) {
+    for (int newVersion in getVersions()) {
+      if (oldVersion >= newVersion) {
+        continue;
+      }
+        test ('upgrade, version $oldVersion to $newVersion', () async {
+          // Create a storage handler with the old version
+          const String passphrase = 'test';
+          StorageCryptoHandler handler = await StorageCryptoHandler.fromNewPassphrase(passphrase, oldVersion);
+
+          // Encrypt some data
+          const String name = 'secret_data_that_should_not_be_padded';
+          const value = 'the secret data not to pad';
+          final String encryptedValue = await handler.encryptValue(name, value);
+
+          // Upgrade to the new version (in this case, using the same passphrase) and get the new key blob
+          await handler.resetPassphrase(passphrase, newVersion);
+          final String keyBlob = await handler.getKeyBlob();
+
+          // Now we can recover the handler with the new passphrase
+          handler = await StorageCryptoHandler.fromExisting(passphrase, keyBlob, newVersion);
+
+          // Confirm that decryption works as expected
+          final String decryptedValue = await handler.decryptValue(name, encryptedValue);
+          expect(decryptedValue, value);
+        });
+    }
+  }
 
   /// Run with each known version
-  for (int version in [1, 2]) {
+  for (int version in getVersions()) {
     /// Version-specific operations
     test('examples, version $version', () async {
       // Create a storage handler from a new passphrase
@@ -174,7 +181,7 @@ void main() {
       expect(() => StorageCryptoHandler.fromExisting(passphrase, evilKeyBlob, version), throwsA(const TypeMatcher<IncorrectPassphraseOrVersion>()));
 
       // Evil version
-      for (int evilVersion in [1, 2]) {
+      for (int evilVersion in getVersions()) {
         if (evilVersion == version) {
           continue;
         }