- Qt 6.9
- Qt Network Authorization
- C++ Classes
- QOAuthHttpServerReplyHandler
- Qt Network Authorization | Commercial or GPLv3

# QOAuthHttpServerReplyHandler Class

Handles loopback redirects by setting up a local HTTP server. More...

Header: | `#include <QOAuthHttpServerReplyHandler>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS NetworkAuth)` `target_link_libraries(mytarget PRIVATE Qt6::NetworkAuth)`
qmake: | `QT += networkauth`
Inherits: | QOAuthOobReplyHandler

- List of all members, including inherited members

## Public Functions

| QOAuthHttpServerReplyHandler(QObject *parent = nullptr)
| QOAuthHttpServerReplyHandler(quint16 port, QObject *parent = nullptr)
| QOAuthHttpServerReplyHandler(const QHostAddress &address, quint16 port, QObject *parent = nullptr)
virtual | ~QOAuthHttpServerReplyHandler()
`(since 6.9)` QString | callbackHost() const
QString | callbackPath() const
QString | callbackText() const
void | close()
bool | isListening() const
bool | listen(const QHostAddress &address = QHostAddress::Any, quint16 port = 0)
bool | listen(const QSslConfiguration &configuration, const QHostAddress &address = QHostAddress::Any, quint16 port = 0)
quint16 | port() const
`(since 6.9)` void | setCallbackHost(const QString &host)
void | setCallbackPath(const QString &path)
void | setCallbackText(const QString &text)

## Detailed Description

This class serves as a reply handler for OAuth 2.0 authorization processes that use loopback redirection.

The redirect 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. Loopback redirect URIs use `http` as the scheme and either localhost or an IP address literal as the host (see IPv4 and IPv6).

QOAuthHttpServerReplyHandler sets up a localhost server. Once the authorization server redirects the browser to this localhost address, the reply handler parses the redirection URI query parameters, and then signals authorization completion with a signal.

To handle other redirect URI schemes, see QOAuthUriSchemeReplyHandler.

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

     QOAuth2AuthorizationCodeFlow m_oauth;
     QOAuthHttpServerReplyHandler *m_handler = nullptr;

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

     m_oauth.setAuthorizationUrl(QUrl(authorizationUrl));
     m_oauth.setTokenUrl(QUrl(accessTokenUrl));
     m_oauth.setClientIdentifier(clientIdentifier);
     m_oauth.setRequestedScopeTokens({scope});

     m_handler = new QOAuthHttpServerReplyHandler(1234, this);

     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_oauth.setReplyHandler(m_handler);

     // Initiate the authorization
     if (m_handler->isListening()) {
         m_oauth.grant();
     }

### IPv4 and IPv6

If the handler is an any address handler (AnyIPv4, AnyIPv6, or Any), the used callback is in the form of `http://localhost:{port}/{path}`. Handler will first attempt to listen on IPv4 loopback address, and then on IPv6. `localhost` is used because it resolves correctly on both IPv4 and IPv6 interfaces.

For loopback addresses (LocalHost or LocalHostIPv6) the IP literals (`127.0.0.1` and `::1`) are used.

For specific IP addresses the provided IP literal is used directly, for instance: http://192.168.0.123:{port}/{path} in the case of an IPv4 address.

It's also possible to specify the host part of the callback URL manually with setCallbackHost(). For instance you can specify the callback to be `localhost.localnet`. Naturally you need to ensure that such address is reachable upon redirection.

     auto replyHandler = new QOAuthHttpServerReplyHandler(QHostAddress::LocalHost, 1337, this);
     replyHandler->setCallbackHost("localhost.localnet"_L1);

### HTTP and HTTPS Callbacks

Since Qt 6.9 it's possible to configure the handler to use `https` URI scheme instead of `http`. This is done by providing an appropriate QSslConfiguration when calling listen(). Internally the handler will then use QSslServer, and the callback (redirect URL) will be of the form https://{host}:{port}/{path}.

Following example illustrates this:

     // Read certificate and private key
     auto certificates = QSslCertificate::fromPath(sslCertificateFile);
     QFile keyFile(sslPrivateKeyFile);
     if (!keyFile.open(QFile::ReadOnly)) {
         qWarning("Cannot open key file");
         return;
     }
     QSslKey privateKey(&keyFile, QSsl::Rsa, QSsl::Pem);
     if (certificates.size() == 0 || privateKey.isNull()) {
         qWarning("SSL certificate data invalid");
         return;
     }

     // Create SSL configuration
     QSslConfiguration configuration = QSslConfiguration::defaultConfiguration();
     configuration.setLocalCertificate(certificates.at(0));
     configuration.setPrivateKey(privateKey);

     // Instantiate handler with the SSL configuration
     m_handler = new QOAuthHttpServerReplyHandler(1234, this);
     m_handler->listen(configuration);

When possible, it is recommended to use other redirect URI options, see Choosing A Reply Handler and Qt OAuth2 Browser Support.

The primary use cases for a localhost `https` handler should be limited to development-time, or tightly controlled and provisioned environments. For example, some Authorization Servers won't allow plain `http` redirect URIs at all, in which case this can add to development convenience.

From security perspective, while using SSL/TLS does encrypt the localhost traffic, OAuth2 has also other security mechanisms in place such as PKCE. Under no circumstances you should distribute private certificate keys along with the application.

Note: Browsers will issue severe warnings if the certificate is not trusted. This is typical with self-signed certificates, whose use should be limited to development-time.

## Member Function Documentation

### `[explicit]` QOAuthHttpServerReplyHandler::QOAuthHttpServerReplyHandler(QObject *parent = nullptr)

Constructs a QOAuthHttpServerReplyHandler object using parent as a parent object. Calls listen() with port `0` and address LocalHost.

See also listen().

### `[explicit]` QOAuthHttpServerReplyHandler::QOAuthHttpServerReplyHandler(quint16 port, QObject *parent = nullptr)

Constructs a QOAuthHttpServerReplyHandler object using parent as a parent object. Calls listen() with port and address LocalHost.

See also listen().

### `[explicit]` QOAuthHttpServerReplyHandler::QOAuthHttpServerReplyHandler(const QHostAddress &address, quint16 port, QObject *parent = nullptr)

Constructs a QOAuthHttpServerReplyHandler object using parent as a parent object. Calls listen() with address and port.

See also listen().

### `[virtual noexcept]` QOAuthHttpServerReplyHandler::~QOAuthHttpServerReplyHandler()

Destroys the QOAuthHttpServerReplyHandler object. Stops listening for connections / redirections.

See also close().

### `[since 6.9]` QString QOAuthHttpServerReplyHandler::callbackHost() const

Returns the name that is used as the host component of the callback() / OAuth2 redirect_uri parameter.

This function was introduced in Qt 6.9.

See also setCallbackHost().

### QString QOAuthHttpServerReplyHandler::callbackPath() const

Returns the path that is used as the path component of the callback() / OAuth2 redirect_uri parameter.

See also setCallbackPath().

### QString QOAuthHttpServerReplyHandler::callbackText() const

Returns the text that is used in response to the redirection at the end of the authorization stage.

The text is wrapped in a simple HTML page, and displayed to the user by the browser / user-agent which did the redirection.

The default text is

     Callback received. Feel free to close this page.

See also setCallbackText().

### void QOAuthHttpServerReplyHandler::close()

Tells this handler to stop listening for connections / redirections.

See also listen().

### bool QOAuthHttpServerReplyHandler::isListening() const

Returns `true` if this handler is currently listening, and `false` otherwise.

See also listen() and close().

### bool QOAuthHttpServerReplyHandler::listen(const QHostAddress &address = QHostAddress::Any, quint16 port = 0)

Tells this handler to listen for incoming connections / redirections on address and port. Returns `true` if listening is successful, and `false` otherwise.

Active listening is only required when performing the initial authorization phase, typically initiated by a QOAuth2AuthorizationCodeFlow::grant() call.

It is recommended to close the listener after successful authorization. Listening is not needed for requesting access tokens or refreshing them.

If this function is called with Null as the address, the handler will attempt to listen to LocalHost, and if that fails, LocalHostIPv6.

See also IPv4 and IPv6.

See also close(), isListening(), and QTcpServer::listen().

### bool QOAuthHttpServerReplyHandler::listen(const QSslConfiguration &configuration, const QHostAddress &address = QHostAddress::Any, quint16 port = 0)

Tells this handler to listen for incoming `https` connections / redirections on address and port. Returns `true` if listening is successful, and `false` otherwise.

See HTTP and HTTPS Callbacks for further information.

See also listen(const QHostAddress &, quint16), close(), isListening(), QSslServer, and QTcpServer::listen().

### quint16 QOAuthHttpServerReplyHandler::port() const

Returns the port on which this handler is listening, otherwise returns 0.

See also listen() and isListening().

### `[since 6.9]` void QOAuthHttpServerReplyHandler::setCallbackHost(const QString &host)

Sets host to be used as the hostname component of the callback(). Providing a non-empty host overrides the default behavior, see IPv4 and IPv6.

This function was introduced in Qt 6.9.

See also callbackHost().

### void QOAuthHttpServerReplyHandler::setCallbackPath(const QString &path)

Sets path to be used as the path component of the callback().

See also callbackPath().

### void QOAuthHttpServerReplyHandler::setCallbackText(const QString &text)

Sets text to be used in response to the redirection at the end of the authorization stage.

See also callbackText().