QOAuthUriSchemeReplyHandler Class

Detailed Description

This class serves as a reply handler for OAuth 2.0 authorization processes that use private/custom or HTTPS URI schemes for redirection. It manages the reception of the authorization redirection (also known as the callback) and the subsequent acquisition of access tokens.

The redirection URI is where the authorization server redirects the user-agent (typically, and preferably, the system browser) once the authorization part of the flow is complete.

The use of specific URI schemes requires configuration at the operating system level to associate the URI with the correct application. The way to set up this association varies between operating systems. See Platform Support and Dependencies.

This class complements QOAuthHttpServerReplyHandler, which handles http schemes by setting up a localhost server.

The following code illustrates the usage. First, the needed variables:

QOAuth2AuthorizationCodeFlow m_oauth;
QOAuthUriSchemeReplyHandler m_handler;

Followed up by the OAuth setup (error handling omitted for brevity):

m_oauth.setAuthorizationUrl(QUrl("https://some.authorization.service/v3/authorize"_L1));
m_oauth.setAccessTokenUrl(QUrl("https://some.authorization.service/v3/access_token"_L1));
m_oauth.setClientIdentifier("a_client_id"_L1);
m_oauth.setScope("read"_L1);

connect(&m_oauth, &QAbstractOAuth::authorizeWithBrowser, this, &QDesktopServices::openUrl);
connect(&m_oauth, &QAbstractOAuth::granted, this, [this]() {
    // Here we use QNetworkRequestFactory to store the access token
    m_api.setBearerToken(m_oauth.token().toLatin1());
    m_handler.close();
});

Finally, we then set up the URI scheme reply-handler:

m_handler.setRedirectUrl(QUrl{"com.my.app:/oauth2redirect"_L1});
m_oauth.setReplyHandler(&m_handler);

// Initiate the authorization
if (m_handler.listen()) {
    m_oauth.grant();
}

Private/Custom URI Schemes

Custom URI schemes typically use reverse-domain notation followed by a path, or occasionally a host/host+path:

// Example with path:
com.example.myapp:/oauth2/callback
// Example with host:
com.example.myapp://oauth2.callback

HTTPS URI Scheme

With HTTPS URI schemes, the redirect URLs are regular https links:

https://myapp.example.com/oauth2/callback

These links are called Universal Links on iOS and App Links on Android.

The use of https schemes is recommended as it provides additional security by forcing application developers to prove ownership of the URLs used. This proving is done by hosting an association file, which the operating system will consult as part of its internal URL dispatching.

The content of this file associates the application and the used URLs. The association files must be publicly accessible without any HTTP redirects. In addition, the hosting site must have valid certificates and, at least with Android, the file must be served as application/json content-type (refer to your server's configuration guide).

In addition, https links can provide some usability benefits:

• The https URL doubles as a regular https link. If the user hasn't installed the application (since the URL wasn't handled by any application), the https link may for example serve instructions to do so.
• The application selection dialogue to open the URL may be avoided, and instead your application may be opened automatically

The tradeoff is that this requires extra setup as you need to set up this publicly-hosted association file.

Platform Support and Dependencies

Currently supported platforms are Android, iOS, and macOS.

URI scheme listening is based on QDesktopServices::setUrlHandler() and QDesktopServices::unsetUrlHandler(). These are currently provided by Qt::Gui module and therefore QtNetworkAuth module depends on Qt::Gui. If QtNetworkAuth is built without Qt::Gui, QOAuthUriSchemeReplyHandler will not be included.

Android

On Android the URI schemes require:

• Setting up intent-filters in the application manifest
• Optionally, for automatic verification with https schemes, hosting a site association file assetlinks.json

See also the Qt Android Manifest File Configuration.

iOS and macOS

On iOS and macOS the URI schemes require:

• Setting up site association entitlement
• With https schemes, hosting a site association file (apple-app-site-association)

Windows, Linux

Currently not supported.