halkyon/packages/halkyon_oidc_server/test/unit/id_token_test.dart

import 'dart:convert';

import 'package:clock/clock.dart';
import 'package:dart_jsonwebtoken/dart_jsonwebtoken.dart';
import 'package:halkyon_oidc_server/src/id_token.dart';
import 'package:halkyon_oidc_server/testing.dart';
import 'package:test/test.dart';

// An ID token proves who someone is only when everything in it checks out
// (ADR 0023, 5): signed with one of the provider's keys, the one its `kid`
// names, by an algorithm the provider uses; for this client, from this
// issuer, for this attempt (the nonce), not expired. Each test spoils one
// thing of a token that otherwise passes.

const issuer = 'https://id.example';
const clientId = 'client-1';
const nonce = 'nonce-1';

void main() {
  late TestKey key;
  late TestKey other;
  final now = DateTime.utc(2026, 10, 23, 18);

  setUpAll(() {
    key = TestKey.generate('a', seed: 1);
    other = TestKey.generate('b', seed: 2);
  });

  Map<String, Object?> claims([Map<String, Object?> changes = const {}]) => {
    'iss': issuer,
    'sub': '42',
    'aud': clientId,
    'exp': secondsOf(now.add(const Duration(hours: 1))),
    'iat': secondsOf(now),
    'nonce': nonce,
    'name': 'Ada',
    ...changes,
  }..removeWhere((_, value) => value == null);

  Future<Map<String, Object?>> check(
    String token, {
    Set<String> algorithms = const {'RS256'},
    Map<String?, JWTKey>? keys,
  }) => withClock(
    Clock.fixed(now),
    () => checkIdToken(
      token,
      issuer: issuer,
      clientId: clientId,
      algorithms: algorithms,
      nonce: nonce,
      keyFor: (kid) async => (keys ?? {'a': RSAPublicKey.raw(key.public)})[kid],
    ),
  );

  Matcher rejected() => throwsA(isA<IdTokenRejected>());

  group('a token that checks out', () {
    test(
      'is accepted without typ in its header, as SimpleLogin signs it',
      () async {
        final checked = await check(key.sign(claims()));
        expect(checked['sub'], '42');
        expect(checked['name'], 'Ada');
      },
    );

    test('is accepted with typ JWT too', () async {
      final token = key.sign(
        claims(),
        header: {'alg': 'RS256', 'kid': 'a', 'typ': 'JWT'},
      );
      expect((await check(token))['sub'], '42');
    });

    test(
      'is accepted with the client among several audiences, named as azp',
      () async {
        final token = key.sign(
          claims({
            'aud': [clientId, 'another'],
            'azp': clientId,
          }),
        );
        expect((await check(token))['sub'], '42');
      },
    );

    test(
      'is accepted up to a minute after it expired, for the clocks',
      () async {
        final token = key.sign(
          claims({'exp': secondsOf(now.subtract(const Duration(seconds: 30)))}),
        );
        expect((await check(token))['sub'], '42');
      },
    );

    test(
      'without a kid, is checked with the key when the provider has one',
      () async {
        final token = key.sign(claims(), header: {'alg': 'RS256'});
        final checked = await check(
          token,
          keys: {null: RSAPublicKey.raw(key.public)},
        );
        expect(checked['sub'], '42');
      },
    );
  });

  group('the signature', () {
    test('by another key under the same kid is refused', () {
      final token = other.sign(
        claims(),
        header: {'alg': 'RS256', 'kid': 'a'},
      );
      expect(check(token), rejected());
    });

    test('of a kid the provider has no key for is refused', () {
      expect(check(other.sign(claims())), rejected());
    });

    test('over a payload changed afterwards is refused', () {
      final parts = key.sign(claims()).split('.');
      final changed = base64Url
          .encode(utf8.encode(jsonEncode(claims({'sub': '43'}))))
          .replaceAll('=', '');
      expect(check('${parts[0]}.$changed.${parts[2]}'), rejected());
    });

    test('by an algorithm the provider does not use is refused', () {
      expect(check(key.sign(claims(), algorithm: 'RS512')), rejected());
    });

    test('as an HMAC keyed with the public key is refused', () {
      // The classic confusion: the public key, which anyone has, as the
      // secret of an HMAC, which a check trusting the header would accept.
      final token = signToken(
        claims(),
        header: {'alg': 'HS256', 'kid': 'a'},
        algorithm: JWTAlgorithm.HS256,
        key: SecretKey(jsonEncode(key.jwk)),
      );
      expect(
        check(token, algorithms: {'RS256', 'HS256'}),
        rejected(),
      );
    });

    test('that is none is refused', () {
      final parts = key.sign(claims()).split('.');
      final header = base64Url
          .encode(utf8.encode(jsonEncode({'alg': 'none', 'kid': 'a'})))
          .replaceAll('=', '');
      expect(check('$header.${parts[1]}.'), rejected());
      expect(check('$header.${parts[1]}'), rejected());
    });

    test('without a kid is refused where the provider has several keys', () {
      final token = key.sign(claims(), header: {'alg': 'RS256'});
      expect(
        check(
          token,
          keys: {
            'a': RSAPublicKey.raw(key.public),
            'b': RSAPublicKey.raw(other.public),
          },
        ),
        rejected(),
      );
    });
  });

  group('the claims', () {
    test('from another issuer, or none, are refused', () {
      expect(
        check(key.sign(claims({'iss': 'https://evil.example'}))),
        rejected(),
      );
      expect(check(key.sign(claims({'iss': '$issuer/'}))), rejected());
      expect(check(key.sign(claims({'iss': null}))), rejected());
    });

    test('for another client, or none, are refused', () {
      expect(check(key.sign(claims({'aud': 'client-2'}))), rejected());
      expect(check(key.sign(claims({'aud': null}))), rejected());
      expect(check(key.sign(claims({'aud': <String>[]}))), rejected());
    });

    test('for several audiences without this client as azp are refused', () {
      expect(
        check(
          key.sign(
            claims({
              'aud': [clientId, 'another'],
            }),
          ),
        ),
        rejected(),
      );
      expect(
        check(
          key.sign(
            claims({
              'aud': [clientId, 'another'],
              'azp': 'another',
            }),
          ),
        ),
        rejected(),
      );
    });

    test('expired more than a minute ago, or never, are refused', () {
      expect(
        check(
          key.sign(
            claims({
              'exp': secondsOf(now.subtract(const Duration(minutes: 2))),
            }),
          ),
        ),
        rejected(),
      );
      expect(check(key.sign(claims({'exp': null}))), rejected());
      expect(check(key.sign(claims({'exp': 'tomorrow'}))), rejected());
    });

    test('issued, or valid from, more than a minute ahead are refused', () {
      final ahead = secondsOf(now.add(const Duration(minutes: 2)));
      expect(check(key.sign(claims({'iat': ahead}))), rejected());
      expect(check(key.sign(claims({'iat': null}))), rejected());
      expect(check(key.sign(claims({'nbf': ahead}))), rejected());
    });

    test('for another attempt, or none, are refused (the nonce)', () {
      expect(check(key.sign(claims({'nonce': 'nonce-2'}))), rejected());
      expect(check(key.sign(claims({'nonce': null}))), rejected());
    });

    test('naming nobody are refused', () {
      expect(check(key.sign(claims({'sub': null}))), rejected());
      expect(check(key.sign(claims({'sub': ''}))), rejected());
      expect(check(key.sign(claims({'sub': 42}))), rejected());
    });
  });

  group('what is no token', () {
    test('is refused', () {
      final good = key.sign(claims()).split('.');
      expect(check(''), rejected());
      expect(check('${good[0]}.${good[1]}'), rejected());
      expect(check('x.${good[1]}.${good[2]}'), rejected());
      final notAnObject = base64Url
          .encode(utf8.encode('[1]'))
          .replaceAll('=', '');
      expect(check('$notAnObject.${good[1]}.${good[2]}'), rejected());
      expect(check('${good[0]}.$notAnObject.${good[2]}'), rejected());
    });
  });
}