angel3_auth_oauth2

Description:

angel3 auth oauth2

Angel3 OAuth2 Handler #

(https://dart.dev/null-safety)


Angel3 library for authenticating users with remote identity providers via OAuth2, i.e. Facebook, Google, Azure AD, etc.
Usage #
First, create an options object:
configureServer(Angel app) async {
// Load from a Map, i.e. app config:
var opts = ExternalAuthOptions.fromMap(app.configuration['auth0'] as Map);

// Create in-place:
var opts = ExternalAuthOptions(
clientId: '<client-id>',
clientSecret: '<client-secret>',
redirectUri: Uri.parse('<callback>'));
}
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After getting authenticated against the remote server, we need to be able to identify users within our own application.
typedef OAuth2Verifier = FutureOr<User> Function(oauth2.Client, RequestContext, ResponseContext);

/// You might use a pure function to create a verifier that queries a
/// given service.
OAuth2Verifier oauth2verifier(Service<User> userService) {
return (client) async {
var response = await client.get('https://api.github.com/user');
var ghUser = json.decode(response.body);
var id = ghUser['id'] as int;

var matchingUsers = await mappedUserService.index({
'query': {'github_id': id}
});

if (matchingUsers.isNotEmpty) {
// Return the corresponding user, if it exists.
return matchingUsers.first;
} else {
// Otherwise,create a user
return await mappedUserService.create(User(githubId: id));
}
};
}
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Now, initialize an OAuth2Strategy, using the options and verifier. You'll also need to provide a name for this instance of the strategy. Consider using the name of the remote authentication provider (ex. facebook).
configureServer(Angel app) {
auth.strategies['github'] = OAuth2Strategy(
options,
authorizationEndpoint,
tokenEndpoint,
yourVerifier,

// This function is called when an error occurs, or the user REJECTS the request.
(e, req, res) async {
res.write('Ooops: $e');
await res.close();
},
);
}
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Lastly, connect it to an AngelAuth instance, and wire it up to an Angel server. Set up two routes:

Redirect users to the external provider
Acts as a callback and handles an access code

In the case of the callback route, you may want to display an HTML page that closes a popup window. In this case, use confirmPopupAuthentication, which is bundled with package:angel3_auth, as a callback function:
configureServer(Angel app) async {
// ...
var auth = AngelAuth<User>();
auth.strategies['github'] = oauth2Strategy;

// Redirect
app.get('/auth/github', auth.authenticate('github'));

// Callback
app.get('/auth/github/callback', auth.authenticate(
'github',
AngelAuthOptions(callback: confirmPopupAuthentication())
));

// Connect the plug-in!!!
await app.configure(auth);
}
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Custom Scope Delimiter #
This package should work out-of-the-box for most OAuth2 providers, such as Github or Dropbox. However, if your OAuth2 scopes are separated by a delimiter other than the default (' '), you can add it in the OAuth2Strategy constructor:
configureServer(Angel app) async {
OAuth2Strategy(..., delimiter: ' ');
}
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Handling non-JSON responses #
Many OAuth2 providers do not follow the specification, and do not return application/json responses.
You can add a getParameters callback to parse the contents of any arbitrary response:
OAuth2Strategy(
// ...
getParameters: (contentType, body) {
if (contentType.type == 'application') {
if (contentType.subtype == 'x-www-form-urlencoded')
return Uri.splitQueryString(body);
else if (contentType.subtype == 'json') return JSON.decode(body);
}

throw FormatException('Invalid content-type $contentType; expected application/x-www-form-urlencoded or application/json.');
}
);
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