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.
2026-10-23 10:50:42 +02:00
parent 2f6b542f24
commit 717aeed4ff
23 changed files with 999 additions and 67 deletions
@@ -0,0 +1,58 @@
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:sepot/core/safety/lookalike_names.dart';
+import 'package:sepot/models/contact.dart';
+import 'package:sepot/models/identity.dart';
+
+/// Jméno zvolené odesílatelem se nesmí dát „obejít“ diakritikou, velikostí
+/// písmen, cizí abecedou ani neviditelnými znaky.
+void main() {
+  Contact kontakt(String jmeno, {bool accepted = true, int seed = 1}) =>
+      Contact.fromPublicIdentity(
+        PublicIdentity(
+          displayName: jmeno,
+          identityKey: Uint8List.fromList(
+              [0x05, ...List.generate(32, (i) => (i * seed + 3) & 0xff)]),
+          createdAt: DateTime.utc(2026),
+        ),
+        accepted: accepted,
+      );
+
+  test('stejná kostra pro varianty téhož jména', () {
+    final mama = nameSkeleton('Máma');
+    for (final varianta in [
+      'mama',
+      'MAMA',
+      ' Má ma ',
+      'Máma!',
+      'M\u00E1\u200Bma',
+      '\u041C\u00E1\u043C\u0430', // cyrilské М, м, а
+      'Ma\u0301ma', // kombinující čárka
+      'Mámа\u202E',
+    ]) {
+      expect(nameSkeleton(varianta), mama, reason: varianta);
+    }
+  });
+
+  test('homoglyfy l/I/1 a rn/m', () {
+    expect(nameSkeleton('Pavel'), nameSkeleton('PaveI'));
+    expect(nameSkeleton('Pavel'), nameSkeleton('Pave1'));
+    expect(nameSkeleton('Marek'), nameSkeleton('rnarek'));
+  });
+
+  test('různá jména se nepletou', () {
+    expect(nameSkeleton('Máma'), isNot(nameSkeleton('Táta')));
+    expect(nameSkeleton('Jana'), isNot(nameSkeleton('Jan')));
+  });
+
+  test('porovnává jen s přijatými kontakty a ne se sebou', () {
+    final mama = kontakt('Máma');
+    final zadost = kontakt('MAMA', accepted: false, seed: 2);
+    expect(lookalikeContact('mama', [mama, zadost]), same(mama));
+    expect(lookalikeContact('mama', [zadost]), isNull);
+    expect(lookalikeContact('mama', [mama], exceptId: mama.id), isNull);
+    expect(lookalikeContact('', [kontakt('')]), isNull,
+        reason: 'prázdné jméno nic nenese');
+  });
+}