fix(security): treat a new identity key as a message request, never as a known contact
A stranger could pick the display name of an existing contact ("Mom")
and appear as that contact. Messages from a key that is not in the
contact list now open a message request labelled "(unknown)": no
replies, read receipts, typing indicators, calls or name in
notifications until the user accepts it and names the contact
themselves. Names that look like an existing contact (case, diacritics,
Cyrillic/Greek homoglyphs, invisible characters) also show a warning in
the real contact's chat.
When the relay account of a known contact shows up with a different
key, the chat shows "safety number changed", verification is cleared
and the session that now belongs to the other key is dropped before
sending, so a reply never goes to the new key.
This commit is contained in:
Julius Joska
@@ -0,0 +1,58 @@
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import 'dart:typed_data';
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import 'package:flutter_test/flutter_test.dart';
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import 'package:sepot/core/safety/lookalike_names.dart';
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import 'package:sepot/models/contact.dart';
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import 'package:sepot/models/identity.dart';
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/// Jméno zvolené odesílatelem se nesmí dát „obejít“ diakritikou, velikostí
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/// písmen, cizí abecedou ani neviditelnými znaky.
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void main() {
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Contact kontakt(String jmeno, {bool accepted = true, int seed = 1}) =>
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Contact.fromPublicIdentity(
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PublicIdentity(
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displayName: jmeno,
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identityKey: Uint8List.fromList(
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[0x05, ...List.generate(32, (i) => (i * seed + 3) & 0xff)]),
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createdAt: DateTime.utc(2026),
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),
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accepted: accepted,
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);
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test('stejná kostra pro varianty téhož jména', () {
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final mama = nameSkeleton('Máma');
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for (final varianta in [
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'mama',
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'MAMA',
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' Má ma ',
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'Máma!',
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'M\u00E1\u200Bma',
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'\u041C\u00E1\u043C\u0430', // cyrilské М, м, а
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'Ma\u0301ma', // kombinující čárka
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'Mámа\u202E',
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]) {
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expect(nameSkeleton(varianta), mama, reason: varianta);
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}
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});
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test('homoglyfy l/I/1 a rn/m', () {
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expect(nameSkeleton('Pavel'), nameSkeleton('PaveI'));
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expect(nameSkeleton('Pavel'), nameSkeleton('Pave1'));
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expect(nameSkeleton('Marek'), nameSkeleton('rnarek'));
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});
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test('různá jména se nepletou', () {
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expect(nameSkeleton('Máma'), isNot(nameSkeleton('Táta')));
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expect(nameSkeleton('Jana'), isNot(nameSkeleton('Jan')));
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});
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test('porovnává jen s přijatými kontakty a ne se sebou', () {
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final mama = kontakt('Máma');
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final zadost = kontakt('MAMA', accepted: false, seed: 2);
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expect(lookalikeContact('mama', [mama, zadost]), same(mama));
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expect(lookalikeContact('mama', [zadost]), isNull);
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expect(lookalikeContact('mama', [mama], exceptId: mama.id), isNull);
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expect(lookalikeContact('', [kontakt('')]), isNull,
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reason: 'prázdné jméno nic nenese');
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});
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}
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@@ -0,0 +1,251 @@
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// Potřebuje nativní libsignal (FFI) — na builderu bez Rust toolchainu se vynechává (--exclude-tags ffi).
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@Tags(['ffi'])
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library;
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import 'dart:convert';
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import 'dart:io';
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import 'dart:math';
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import 'dart:typed_data';
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import 'package:flutter_test/flutter_test.dart';
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import 'package:libsignal/libsignal.dart' show ProtocolAddress;
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import 'package:sepot/core/crypto/sepot_crypto.dart';
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import 'package:sepot/core/services/messaging_service.dart';
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import 'package:sepot/core/storage/crypto_db.dart';
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import 'package:sepot/core/storage/persistent_stores.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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import 'package:sepot/models/message.dart';
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/// Phishing „Máma“: cizí klíč se jménem existujícího kontaktu nesmí
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/// splynout s kontaktem ani převzít jeho jméno, ověření nebo hovory.
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/// Změna klíče pod adresou známého kontaktu ruší ověření a varuje.
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void main() {
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late Directory tmp;
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late CryptoDb db;
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late SecureStorageService storage;
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late MessagingService service;
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late LocalIdentity ja;
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late LocalIdentity mama;
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late Contact mamaContact;
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final rng = Random.secure();
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final sent = <(String, Map<String, dynamic>)>[];
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final calls = <String>[];
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Uint8List randomBytes(int n) =>
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Uint8List.fromList(List.generate(n, (_) => rng.nextInt(256)));
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const mamaAccount = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
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setUpAll(() async => SepotCrypto.init());
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setUp(() async {
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tmp = Directory.systemTemp.createTempSync('sepot_request');
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db = CryptoDb.open(path: '${tmp.path}/app.db', dek: randomBytes(32));
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storage = SecureStorageService(dbPath: '${tmp.path}/app.db')
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..debugAttachDb(db);
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service = MessagingService(storage: storage);
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ja = await LocalIdentity.create('Já');
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service.debugSetIdentity(ja);
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sent.clear();
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calls.clear();
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service.debugSendTap = (to, content) => sent.add((to, content));
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service.onCallSignal = (contact, _) => calls.add(contact.id);
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mama = await LocalIdentity.create('Máma');
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mamaContact = Contact.fromPublicIdentity(
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mama.publicIdentity
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.withRouting(accountId: mamaAccount, deliveryAddress: randomBytes(32)),
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verified: true,
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);
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await storage.saveContact(mamaContact);
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await storage.saveConversation(Conversation(contactId: mamaContact.id));
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});
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tearDown(() {
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db.close();
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tmp.deleteSync(recursive: true);
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});
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/// Obálka od [from] po dešifrování (sealed sender už ověřil klíč a účet).
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Future<void> deliver(
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LocalIdentity from,
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String account,
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Map<String, dynamic> content,
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) =>
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service.debugProcessOpened(
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SepotSealedMessage(
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plaintext: utf8.encode(jsonEncode({'v': 1, ...content})),
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senderName: account,
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senderDeviceId: 1,
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senderIdentityKey: from.publicIdentity.identityKey,
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),
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randomBytes(16),
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);
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Map<String, dynamic> text(String name, String txt) => {
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't': 'txt',
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'id': 'm-${rng.nextInt(1 << 30)}',
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'txt': txt,
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'p': {'n': name, 'da': base64Encode(randomBytes(32))},
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};
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Future<Contact> contactOf(LocalIdentity id) async =>
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(await storage.loadContacts()).singleWhere((c) => c.id == id.id);
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test('cizí klíč se jménem „Máma“ = žádost o zprávu, ne splynutí', () async {
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final podvrh = await LocalIdentity.create('Máma');
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await deliver(podvrh, 'b' * 32, text('Máma', 'Pošli mi kód z SMS'));
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final kontakty = await storage.loadContacts();
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expect(kontakty, hasLength(2), reason: 'nový klíč = nový kontakt');
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final skutecna = await contactOf(mama);
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expect(skutecna.displayName, 'Máma');
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expect(skutecna.verified, isTrue, reason: 'cizí klíč ověření nemění');
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expect(skutecna.publicIdentity.identityKey, mama.publicIdentity.identityKey);
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final zadost = await contactOf(podvrh);
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expect(zadost.accepted, isFalse);
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expect(zadost.verified, isFalse);
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final zprava = (await storage.loadConversation(zadost.id))!.messages.single;
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expect(zprava.content, 'Pošli mi kód z SMS');
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expect(zprava.senderId, podvrh.id, reason: 'zpráva patří podvrhu');
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final upozorneni =
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(await storage.loadConversation(skutecna.id))!.messages.single;
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expect(upozorneni.notice, MessageNotice.lookalikeRequest);
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expect(upozorneni.content, 'Máma');
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});
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test('podobné jméno (cyrilice, velká písmena, mezery) se taky pozná',
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() async {
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final podvrh = await LocalIdentity.create('x');
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await deliver(podvrh, 'c' * 32, text(' МÁМА ', 'ahoj'));
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final upozorneni =
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(await storage.loadConversation(mamaContact.id))!.messages.single;
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expect(upozorneni.notice, MessageNotice.lookalikeRequest);
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});
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test('stejný účet na relayi s jiným klíčem = změna bezpečnostního kódu',
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() async {
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final novyKlic = await LocalIdentity.create('Máma');
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await deliver(novyKlic, mamaAccount, text('Máma', 'nový telefon'));
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final skutecna = await contactOf(mama);
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expect(skutecna.verified, isFalse, reason: 'ověření se ruší');
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expect(skutecna.displayName, 'Máma');
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final upozorneni =
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(await storage.loadConversation(skutecna.id))!.messages.single;
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expect(upozorneni.notice, MessageNotice.identityChanged);
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final zadost = await contactOf(novyKlic);
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expect(zadost.accepted, isFalse, reason: 'nový klíč se nepřebírá');
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});
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test('opakovaná změna nepřidává další a další upozornění', () async {
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final novyKlic = await LocalIdentity.create('Máma');
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await deliver(novyKlic, mamaAccount, text('Máma', '1'));
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await deliver(novyKlic, mamaAccount, text('Máma', '2'));
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final zpravy = (await storage.loadConversation(mamaContact.id))!.messages;
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expect(zpravy.where((m) => m.notice != null), hasLength(1));
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});
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test('žádost o zprávu nezvoní, přijatý kontakt ano', () async {
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final cizi = await LocalIdentity.create('Máma');
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await deliver(cizi, 'd' * 32, text('Máma', 'ahoj'));
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await deliver(cizi, 'd' * 32, {'t': 'call', 'id': 'c1', 'k': 'offer'});
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expect(calls, isEmpty);
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await deliver(mama, mamaAccount, {'t': 'call', 'id': 'c2', 'k': 'offer'});
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expect(calls, [mama.id]);
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});
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test('neznámý odesílatel nedostane potvrzení přečtení', () async {
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await storage.setSetting('read_receipts_enabled', true);
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final cizi = await LocalIdentity.create('Někdo');
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await deliver(cizi, 'e' * 32, text('Někdo', 'ahoj'));
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final zadost = await contactOf(cizi);
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sent.clear();
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await service.sendReadReceipts(zadost, ['m1']);
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expect(sent, isEmpty);
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await service.sendReadReceipts(await contactOf(mama), ['m2']);
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expect(sent.single.$2['t'], 'rr');
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});
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test('známý kontakt dál chodí do své konverzace beze změny', () async {
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await deliver(mama, mamaAccount, text('Úplně jiné jméno', 'ahoj'));
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final kontakty = await storage.loadContacts();
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expect(kontakty, hasLength(1));
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expect(kontakty.single.displayName, 'Máma',
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reason: 'jméno z profilu odesílatele nepřepisuje moje');
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expect(kontakty.single.accepted, isTrue);
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expect(kontakty.single.verified, isTrue);
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});
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test('kontakt uložený před 1.2.3 (bez příznaku) je přijatý', () {
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final json = mamaContact.toJson()..remove('accepted');
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expect(Contact.fromJson(json).accepted, isTrue);
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});
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group('odesílání: relace patřící cizímu klíči', () {
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late SepotCrypto ja2;
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late ProtocolAddress addr;
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setUp(() {
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addr = ProtocolAddress(name: mamaAccount, deviceId: 1);
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ja2 = SepotCrypto.fromPrivateKey(
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privateKey: ja.identityPrivateKey,
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accountId: 'f' * 32,
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registrationId: 7,
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storesFactory: (pair) => SepotStores(
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session: DbSessionStore(db),
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identity: DbIdentityKeyStore(db,
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identityKeyPair: pair, registrationId: 7),
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preKey: DbPreKeyStore(db),
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signedPreKey: DbSignedPreKeyStore(db),
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kyberPreKey: DbKyberPreKeyStore(db),
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),
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);
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});
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Future<SepotPreKeyBundle> bundleOf(LocalIdentity id) =>
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SepotCrypto.fromPrivateKey(
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privateKey: id.identityPrivateKey,
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accountId: mamaAccount,
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registrationId: 9,
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).generatePreKeyBundle(
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preKeyId: 1,
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signedPreKeyId: 1,
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kyberPreKeyId: 1,
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timestampMs: DateTime.now().millisecondsSinceEpoch,
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);
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test('relace s klíčem kontaktu zůstává', () async {
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await ja2.processRemoteBundle(addr, await bundleOf(mama));
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await service.debugDropForeignSession(ja2, addr, mamaContact);
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expect(await ja2.hasSession(addr), isTrue);
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expect((await contactOf(mama)).verified, isTrue);
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});
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test('relace přepsaná cizím klíčem se zahodí a kontakt varuje', () async {
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await ja2.processRemoteBundle(addr, await bundleOf(mama));
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final utocnik = await LocalIdentity.create('Máma');
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await ja2.processRemoteBundle(addr, await bundleOf(utocnik));
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await service.debugDropForeignSession(ja2, addr, mamaContact);
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expect(await ja2.hasSession(addr), isFalse,
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reason: 'odpověď nesmí odejít útočníkovi');
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final kontakt = await contactOf(mama);
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expect(kontakt.verified, isFalse);
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final upozorneni =
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(await storage.loadConversation(kontakt.id))!.messages.single;
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expect(upozorneni.notice, MessageNotice.identityChanged);
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});
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});
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}
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