angel_oauth2 2.3.0

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oauth2 #

Pub build status

A class containing handlers that can be used within Angel to build a spec-compliant OAuth 2.0 server, including PKCE support.

Installation #

In your pubspec.yaml:

  angel_framework: ^2.0.0-alpha
  angel_oauth2: ^2.0.0

Usage #

Your server needs to have definitions of at least two types:

  • One model that represents a third-party application (client) trying to access a user's profile.
  • One that represents a user logged into the application.

Define a server class as such:

import 'package:angel_oauth2/angel_oauth2.dart' as oauth2;

class MyServer extends oauth2.AuthorizationServer<Client, User> {}

Then, implement the findClient and verifyClient to ensure that the server class can not only identify a client application via a client_id, but that it can also verify its identity via a client_secret.

class _Server extends AuthorizationServer<PseudoApplication, Map> {
  final Uuid _uuid = Uuid();

  FutureOr<PseudoApplication> findClient(String clientId) {
    return clientId == ? pseudoApplication : null;

  Future<bool> verifyClient(
      PseudoApplication client, String clientSecret) async {
    return client.secret == clientSecret;

Next, write some logic to be executed whenever a user visits the authorization endpoint. In many cases, you will want to show a dialog:

Future requestAuthorizationCode(
  PseudoApplication client,
  String redirectUri,
  Iterable<String> scopes,
  String state,
  RequestContext req,
  ResponseContext res) async {

Now, write logic that exchanges an authorization code for an access token, and optionally, a refresh token.

Future<AuthorizationCodeResponse> exchangeAuthCodeForAccessToken(
  String authCode,
  String redirectUri,
  RequestContext req,
  ResponseContext res) async {
    return AuthorizationCodeResponse('foo', refreshToken: 'bar');

Now, set up some routes to point the server.

void pseudoCode() {'/oauth2', (router) {
      ..get('/authorize', server.authorizationEndpoint)'/token', server.tokenEndpoint);

The authorizationEndpoint and tokenEndpoint handle all OAuth2 grant types.

Other Grants #

By default, all OAuth2 grant methods will throw a 405 Method Not Allowed error. To support any specific grant type, all you need to do is implement the method. The following are available, not including authorization code grant support (mentioned above):

  • implicitGrant
  • resourceOwnerPasswordCredentialsGrant
  • clientCredentialsGrant
  • deviceCodeGrant

Read the OAuth2 specification for in-depth information on each grant type.


In some cases, you will be using OAuth2 on a mobile device, or on some other public client, where the client cannot have a client secret.

In such a case, you may consider using PKCE.

Both the authorizationEndpoint and tokenEndpoint inject a Pkce factory into the request, so it can be used as follows:

Future requestAuthorizationCode(
    PseudoApplication client,
    String redirectUri,
    Iterable<String> scopes,
    String state,
    RequestContext req,
    ResponseContext res) async {
  // Automatically throws an error if the request doesn't contain the
  // necessary information.
  var pkce = req.container.make<Pkce>();

  // At this point, store `pkce.codeChallenge` and `pkce.codeChallengeMethod`,
  // so that when it's time to exchange the auth code for a token, we can
  // create a [Pkce] object, and verify the client.
  return await getAuthCodeSomehow(client, pkce.codeChallenge, pkce.codeChallengeMethod); 

Future<AuthorizationTokenResponse> exchangeAuthorizationCodeForToken(
    String authCode,
    String redirectUri,
    RequestContext req,
    ResponseContext res) async {
  // When exchanging the authorization code for a token, we'll need
  // a `code_verifier` from the client, so that we can ensure
  // that the correct client is trying to use the auth code.
  // If none is present, an OAuth2 exception is thrown.
  var codeVerifier = await getPkceCodeVerifier(req);

  // Next, we'll need to retrieve the code challenge and code challenge method
  // from earlier.
  var codeChallenge = await getTheChallenge();
  var codeChallengeMethod = await getTheChallengeMethod();

  // Make a [Pkce] object.
  var pkce = Pkce(codeChallengeMethod, codeChallenge);

  // Call `validate`. If the client is invalid, it throws an OAuth2 exception.

  // If we reach here, we know that the `code_verifier` was valid,
  // so we can return our authorization token as per usual.
  return AuthorizationTokenResponse('...');

2.3.0 #

  • Remove implicitGrant, and inline it into requestAuthorizationCode.

2.2.0+1 #

  • Parse+verify client for authorization_code.

2.2.0 #

  • Pass client to exchangeAuthorizationCodeForToken.
  • Apply package:pedantic.

2.1.0 #

  • Updates
  • Support device_code grants.
  • Add support for PKCE.

2.0.0 #

  • Angel 2 support.

1.0.0+1 #

  • Dart2 updates + backwards compatibility assurance.


// ignore_for_file: todo
import 'dart:async';
import 'package:angel_framework/angel_framework.dart';
import 'package:angel_oauth2/angel_oauth2.dart';

main() async {
  var app = Angel();
  var oauth2 = _ExampleAuthorizationServer();
  var _rgxBearer = RegExp(r'^[Bb]earer ([^\n\s]+)$');'/auth', (router) {
      ..get('/authorize', oauth2.authorizationEndpoint)'/token', oauth2.tokenEndpoint);

  // Assume that all other requests must be authenticated...
  app.fallback((req, res) {
    var authToken =
        req.headers.value('authorization')?.replaceAll(_rgxBearer, '')?.trim();

    if (authToken == null) {
      throw AngelHttpException.forbidden();
    } else {
      // TODO: The user has a token, now verify it.
      // It is up to you how to store and retrieve auth tokens within your application.
      // The purpose of `package:angel_oauth2` is to provide the transport
      // across which you distribute these tokens in the first place.

class ThirdPartyApp {}

class User {}

/// A [ThirdPartyApp] can act on behalf of a [User].
class _ExampleAuthorizationServer
    extends AuthorizationServer<ThirdPartyApp, User> {
  FutureOr<ThirdPartyApp> findClient(String clientId) {
    // TODO: Add your code to find the app associated with a client ID.
    throw UnimplementedError();

  FutureOr<bool> verifyClient(ThirdPartyApp client, String clientSecret) {
    // TODO: Add your code to verify a client secret, if given one.
    throw UnimplementedError();

  FutureOr requestAuthorizationCode(
      ThirdPartyApp client,
      String redirectUri,
      Iterable<String> scopes,
      String state,
      RequestContext req,
      ResponseContext res,
      bool implicit) {
    // TODO: In many cases, here you will render a view displaying to the user which scopes are being requested.
    throw UnimplementedError();

  FutureOr<AuthorizationTokenResponse> exchangeAuthorizationCodeForToken(
      ThirdPartyApp client,
      String authCode,
      String redirectUri,
      RequestContext req,
      ResponseContext res) {
    // TODO: Here, you'll convert the auth code into a full-fledged token.
    // You might have the auth code stored in a database somewhere.
    throw UnimplementedError();

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:

  angel_oauth2: ^2.3.0

2. Install it

You can install packages from the command line:

with pub:

$ pub get

with Flutter:

$ flutter pub get

Alternatively, your editor might support pub get or flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:

import 'package:angel_oauth2/angel_oauth2.dart';
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Learn more about scoring.

We analyzed this package on Apr 4, 2020, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.7.1
  • pana: 0.13.6

Health suggestions

Fix lib/src/exception.dart. (-0.50 points)

Analysis of lib/src/exception.dart reported 1 hint:

line 20 col 7: DO use curly braces for all flow control structures.

Fix lib/src/server.dart. (-0.50 points)

Analysis of lib/src/server.dart reported 1 hint:

line 227 col 7: DO use curly braces for all flow control structures.


Package Constraint Resolved Available
Direct dependencies
Dart SDK >=2.0.0-dev <3.0.0
angel_framework ^2.0.0-rc.0 2.1.1
angel_http_exception ^1.0.0 1.1.0
crypto ^2.0.0 2.1.4
Transitive dependencies
angel_container 1.1.0
angel_model 1.0.3
angel_route 3.1.0+1
charcode 1.1.3
code_buffer 1.0.1
collection 1.14.12
combinator 1.1.0
convert 2.1.1
dart2_constant 1.0.2+dart2
file 5.1.0
http2 1.0.0
http_parser 3.1.4
http_server 0.9.8+3
intl 0.16.1
matcher 0.12.6
merge_map 1.0.2
meta 1.1.8
mime 0.9.6+3
mock_request 1.0.6
path 1.6.4
quiver 2.1.3
quiver_hashcode 2.0.0
recase 2.0.1 3.0.0
source_span 1.7.0
stack_trace 1.9.3
string_scanner 1.0.5
term_glyph 1.1.0
tuple 1.0.3
typed_data 1.1.6
Dev dependencies
angel_test ^2.0.0-alpha
angel_validate ^2.0.0-alpha
logging any 0.11.4
oauth2 ^1.0.0
pedantic ^1.0.0
test ^1.0.0
uuid ^2.0.0 2.0.4