Julius Joska
8081d98c67
Initial public release. Anonymous on-device identity (no phone number, e-mail, or password), Signal-protocol cryptography (X3DH + PQXDH, Double Ratchet, sealed sender) via libsignal, a metadata-minimizing relay, group chats, disappearing messages, encrypted local storage, optional Tor transport, and a UI localized into Czech, English, German, Russian, and Italian. Monorepo: Flutter client (app/), Rust relay + wire types (rust/), protobuf definitions (proto/), self-host deploy (deploy/). Licensed under AGPL-3.0 with an app-store distribution exception (§7).
105 lines
3.7 KiB
Dart
105 lines
3.7 KiB
Dart
import 'dart:convert';
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import 'dart:math';
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import 'dart:typed_data';
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import 'package:cryptography/cryptography.dart';
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import 'package:sepot/core/errors.dart';
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import 'package:sepot/core/storage/secure_storage.dart';
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import 'package:sepot/models/contact.dart';
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import 'package:sepot/models/conversation.dart';
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import 'package:sepot/models/identity.dart';
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/// Šifrovaná záloha historie (kontakty + konverzace).
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///
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/// Klíč se odvozuje z privátního klíče identity (HKDF-SHA256) → zálohu
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/// dešifruje POUZE tvoje identita (po obnově ze slov). Přílohy (bloby)
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/// v záloze nejsou — obnoví se metadata zpráv, samotný soubor se případně
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/// dotáhne z relaye znovu (dokud tam je).
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class BackupService {
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BackupService(this._storage);
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final SecureStorageService _storage;
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// Formát: magic(8) ‖ nonce(12) ‖ ciphertext ‖ GCM tag(16)
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static const _magic = 'SEPOTBK1';
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static const _nonceLen = 12;
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static const _tagLen = 16;
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Future<SecretKey> _deriveKey(Uint8List privateKey) async {
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final hkdf = Hkdf(hmac: Hmac.sha256(), outputLength: 32);
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return hkdf.deriveKey(
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secretKey: SecretKey(privateKey),
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nonce: utf8.encode('sepot-backup-salt-v1'),
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info: utf8.encode('sepot-backup-v1'),
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);
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}
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Uint8List _randomNonce() {
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final r = Random.secure();
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return Uint8List.fromList(List.generate(_nonceLen, (_) => r.nextInt(256)));
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}
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/// Vytvoř šifrovanou zálohu — vrací bajty souboru `.sepotbackup`.
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Future<Uint8List> export(LocalIdentity identity) async {
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final contacts = await _storage.loadContacts();
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final conversations = await _storage.loadConversations();
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final payload = utf8.encode(jsonEncode({
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'v': 1,
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'contacts': contacts.map((c) => c.toJson()).toList(),
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'conversations': conversations.map((c) => c.toJson()).toList(),
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}));
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final key = await _deriveKey(identity.identityPrivateKey);
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final nonce = _randomNonce();
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final box = await AesGcm.with256bits()
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.encrypt(payload, secretKey: key, nonce: nonce);
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final out = BytesBuilder();
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out.add(utf8.encode(_magic));
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out.add(nonce);
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out.add(box.cipherText);
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out.add(box.mac.bytes);
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return out.toBytes();
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}
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/// Obnov ze zálohy. Vrací počet obnovených konverzací. Vyhodí typovanou
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/// chybu ([BackupCorruptedError], [BackupUnknownFormatError],
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/// [BackupWrongIdentityError]) u poškozeného souboru nebo zálohy cizí
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/// identity — UI ji překládá přes describeError.
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Future<int> import(LocalIdentity identity, Uint8List bytes) async {
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if (bytes.length < _magic.length + _nonceLen + _tagLen) {
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throw const BackupCorruptedError();
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}
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if (utf8.decode(bytes.sublist(0, _magic.length)) != _magic) {
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throw const BackupUnknownFormatError();
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}
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final nonce = bytes.sublist(_magic.length, _magic.length + _nonceLen);
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final body = bytes.sublist(_magic.length + _nonceLen);
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final ct = body.sublist(0, body.length - _tagLen);
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final mac = Mac(body.sublist(body.length - _tagLen));
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final key = await _deriveKey(identity.identityPrivateKey);
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List<int> plain;
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try {
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plain = await AesGcm.with256bits().decrypt(
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SecretBox(ct, nonce: nonce, mac: mac),
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secretKey: key,
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);
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} on SecretBoxAuthenticationError {
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throw const BackupWrongIdentityError();
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}
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final json = jsonDecode(utf8.decode(plain)) as Map<String, dynamic>;
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for (final c in (json['contacts'] as List? ?? const [])) {
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await _storage.saveContact(Contact.fromJson(c as Map<String, dynamic>));
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}
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var restored = 0;
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for (final c in (json['conversations'] as List? ?? const [])) {
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await _storage
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.saveConversation(Conversation.fromJson(c as Map<String, dynamic>));
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restored++;
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}
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return restored;
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}
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}
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