halkyon/packages/halkyon_app/test/privacy/sodium_content_cipher_test.dart

import 'dart:convert';
import 'dart:typed_data';

import 'package:flutter_test/flutter_test.dart';
import 'package:halkyon_app/halkyon_app.dart';

/// Content sealed with a data key (ADR 0019), with libsodium as its build
/// hook compiles it.
void main() {
  final crypto = SodiumAccountCrypto();
  late UnlockedAccountKeys alice;
  late UnlockedAccountKeys bob;
  late SodiumContentCipher device;

  final context = utf8.encode('card_revision/0192/payload');
  final plain = Uint8List.fromList(utf8.encode('{"front":"火"}'));

  setUpAll(() async {
    alice = (await crypto.newAccount('alice password')).keys;
    bob = (await crypto.newAccount('bob password')).keys;
  });

  setUp(() async {
    device = SodiumContentCipher();
    await device.unlock(alice);
  });

  tearDown(() => device.dispose());

  test("a key made on one device opens on another of the account's, and "
      'what it seals opens there', () async {
    final sealedKey = device.newKey('studyset-1');
    final sealed = device.seal(plain, keyId: 'studyset-1', context: context);

    final other = SodiumContentCipher();
    await other.unlock(alice);
    addTearDown(other.dispose);
    expect(other.has('studyset-1'), isFalse);
    expect(other.openKey('studyset-1', sealedKey), isTrue);

    expect(other.has('studyset-1'), isTrue);
    expect(other.unseal(sealed, context: context), plain);
    expect(sealed.keyId, 'studyset-1');
    expect(String.fromCharCodes(sealed.payload), isNot(contains('front')));
  });

  test("another account's device opens neither the key nor what it "
      'sealed', () async {
    final sealedKey = device.newKey('studyset-1');
    final sealed = device.seal(plain, keyId: 'studyset-1', context: context);

    final bobs = SodiumContentCipher();
    await bobs.unlock(bob);
    addTearDown(bobs.dispose);

    expect(bobs.openKey('studyset-1', sealedKey), isFalse);
    expect(bobs.unseal(sealed, context: context), isNull);
  });

  test('a key opens only under the ID it was sealed with, and only once '
      'the account is unlocked', () async {
    final sealedKey = device.newKey('studyset-1');
    final other = SodiumContentCipher();
    addTearDown(other.dispose);

    expect(() => other.openKey('studyset-1', sealedKey), throwsStateError);
    await other.unlock(alice);
    expect(other.openKey('studyset-2', sealedKey), isFalse);
    expect(other.openKey('studyset-1', sealedKey), isTrue);
  });

  test('a payload moved to another row, or changed, opens no more', () {
    device.newKey('studyset-1');
    final sealed = device.seal(plain, keyId: 'studyset-1', context: context);
    final changed = Uint8List.fromList(sealed.payload)..last ^= 1;

    expect(
      device.unseal(sealed, context: utf8.encode('card_revision/0193/payload')),
      isNull,
    );
    expect(
      device.unseal(
        SealedPayload(
          keyId: sealed.keyId,
          nonce: sealed.nonce,
          payload: changed,
        ),
        context: context,
      ),
      isNull,
    );
    expect(device.unseal(sealed, context: context), plain);
  });

  test(
    "a row's keyed ID (ADR 0030, D57) is the same on every device of the "
    "account, another on another account's, and none before unlocking",
    () async {
      final other = SodiumContentCipher();
      await other.unlock(alice);
      addTearDown(other.dispose);
      final bobs = SodiumContentCipher();
      await bobs.unlock(bob);
      addTearDown(bobs.dispose);
      final locked = SodiumContentCipher();

      final id = device.rowId('train/day/2026-10-30');
      expect(other.rowId('train/day/2026-10-30'), id);
      expect(bobs.rowId('train/day/2026-10-30'), isNot(id));
      expect(device.rowId('train/day/2026-10-31'), isNot(id));
      expect(() => locked.rowId('train/day/2026-10-30'), throwsStateError);
    },
  );

  test('without its key nothing opens, nor is sealed', () {
    final sealed = SealedPayload(
      keyId: 'unknown',
      nonce: Uint8List(24),
      payload: Uint8List(100),
    );

    expect(device.unseal(sealed, context: context), isNull);
    expect(
      () => device.seal(plain, keyId: 'unknown', context: context),
      throwsStateError,
    );
  });

  test("a shared key's content opens when a member it trusts signed it, "
      "and only for that key (Halkyon's ADR 0044, D20)", () async {
    final carol = (await crypto.newAccount('carol password')).keys;
    PublicKeys keysOf(UnlockedAccountKeys account) => (
      encryption: account.encryptionPublicKey,
      signing: account.signingPublicKey,
    );
    Future<SodiumContentCipher> deviceOf(UnlockedAccountKeys account) async {
      final cipher = SodiumContentCipher();
      await cipher.unlock(account);
      addTearDown(cipher.dispose);
      return cipher;
    }

    final bobs = await deviceOf(bob);
    final carols = await deviceOf(carol);
    for (final keyId in ['shared', 'other']) {
      device.newKey(keyId);
      for (final (cipher, keys) in [(bobs, bob), (carols, carol)]) {
        expect(
          cipher.openSharedKey(
            keyId,
            device.sealKeyTo(keyId, keysOf(keys)),
            sealedBy: alice.signingPublicKey,
          ),
          isTrue,
        );
      }
    }
    final byBob = bobs.seal(plain, keyId: 'shared', context: context);
    final byCarol = carols.seal(plain, keyId: 'shared', context: context);
    final byAlice = device.seal(plain, keyId: 'shared', context: context);

    // Only the account's own, until told whom to trust.
    expect(device.unseal(byBob, context: context), isNull);
    expect(device.unseal(byAlice, context: context), plain);

    device.trustSigners('shared', [
      alice.signingPublicKey,
      bob.signingPublicKey,
    ]);
    expect(device.unseal(byBob, context: context), plain);
    expect(device.unseal(byAlice, context: context), plain);
    expect(device.unseal(byCarol, context: context), isNull);
    expect(
      device.unseal(
        bobs.seal(plain, keyId: 'other', context: context),
        context: context,
      ),
      isNull,
    );

    // What it trusts is replaced, not added to.
    device.trustSigners('shared', [carol.signingPublicKey]);
    expect(device.unseal(byCarol, context: context), plain);
    expect(device.unseal(byBob, context: context), isNull);
    expect(device.unseal(byAlice, context: context), isNull);
  });
}