matrix_sdk/authentication/oauth/qrcode/

login.rs

// Copyright 2024 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::future::IntoFuture;

use eyeball::SharedObservable;
use futures_core::Stream;
use matrix_sdk_base::{
    SessionMeta, boxed_into_future,
    crypto::types::qr_login::{QrCodeData, QrCodeIntent},
    store::RoomLoadSettings,
};
use oauth2::{DeviceCodeErrorResponseType, StandardDeviceAuthorizationResponse};
use ruma::{
    OwnedDeviceId,
    api::client::discovery::get_authorization_server_metadata::v1::AuthorizationServerMetadata,
};
use tracing::trace;
use vodozemac::Curve25519PublicKey;
#[cfg(doc)]
use vodozemac::ecies::CheckCode;

use super::{
    DeviceAuthorizationOAuthError, QRCodeLoginError, SecureChannelError,
    messages::{LoginFailureReason, QrAuthMessage},
    secure_channel::{EstablishedSecureChannel, SecureChannel},
};
use crate::{
    Client,
    authentication::oauth::{
        ClientRegistrationData, OAuth, OAuthError,
        qrcode::{CheckCodeSender, GeneratedQrProgress, LoginProtocolType, QrProgress},
    },
};

async fn send_unexpected_message_error(
    channel: &mut EstablishedSecureChannel,
) -> Result<(), SecureChannelError> {
    channel
        .send_json(QrAuthMessage::LoginFailure {
            reason: LoginFailureReason::UnexpectedMessageReceived,
            homeserver: None,
        })
        .await
}

async fn finish_login<Q>(
    client: &Client,
    mut channel: EstablishedSecureChannel,
    registration_data: Option<&ClientRegistrationData>,
    state: SharedObservable<LoginProgress<Q>>,
) -> Result<(), QRCodeLoginError> {
    let oauth = client.oauth();

    // Register the client with the OAuth 2.0 authorization server.
    trace!("Registering the client with the OAuth 2.0 authorization server.");
    let server_metadata = register_client(&oauth, registration_data).await?;

    // We want to use the Curve25519 public key for the device ID, so let's generate
    // a new vodozemac `Account` now.
    let account = vodozemac::olm::Account::new();
    let public_key = account.identity_keys().curve25519;
    let device_id = public_key;

    // Let's tell the OAuth 2.0 authorization server that we want to log in using
    // the device authorization grant described in [RFC8628](https://datatracker.ietf.org/doc/html/rfc8628).
    trace!("Requesting device authorization.");
    let auth_grant_response =
        request_device_authorization(&oauth, &server_metadata, device_id).await?;

    // Now we need to inform the other device of the login protocols we picked and
    // the URL they should use to log us in.
    trace!("Letting the existing device know about the device authorization grant.");
    let message =
        QrAuthMessage::authorization_grant_login_protocol((&auth_grant_response).into(), device_id);
    channel.send_json(&message).await?;

    // Let's see if the other device agreed to our proposed protocols.
    match channel.receive_json().await? {
        QrAuthMessage::LoginProtocolAccepted => (),
        QrAuthMessage::LoginFailure { reason, homeserver } => {
            return Err(QRCodeLoginError::LoginFailure { reason, homeserver });
        }
        message => {
            send_unexpected_message_error(&mut channel).await?;

            return Err(QRCodeLoginError::UnexpectedMessage {
                expected: "m.login.protocol_accepted",
                received: message,
            });
        }
    }

    // The OAuth 2.0 authorization server may or may not show this user code to
    // double check that we're talking to the right server. Let us display this, so
    // the other device can double check this as well.
    let user_code = auth_grant_response.user_code();
    state.set(LoginProgress::WaitingForToken { user_code: user_code.secret().to_owned() });

    // Let's now wait for the access token to be provided to use by the OAuth 2.0
    // authorization server.
    trace!("Waiting for the OAuth 2.0 authorization server to give us the access token.");
    if let Err(e) = wait_for_tokens(&oauth, &server_metadata, &auth_grant_response).await {
        // If we received an error, and it's one of the ones we should report to the
        // other side, do so now.
        if let Some(e) = e.as_request_token_error() {
            match e {
                DeviceCodeErrorResponseType::AccessDenied => {
                    channel.send_json(QrAuthMessage::LoginDeclined).await?;
                }
                DeviceCodeErrorResponseType::ExpiredToken => {
                    channel
                        .send_json(QrAuthMessage::LoginFailure {
                            reason: LoginFailureReason::AuthorizationExpired,
                            homeserver: None,
                        })
                        .await?;
                }
                _ => (),
            }
        }

        return Err(e.into());
    }

    // We only received an access token from the OAuth 2.0 authorization server, we
    // have no clue who we are, so we need to figure out our user ID
    // now. TODO: This snippet is almost the same as the
    // OAuth::finish_login_method(), why is that method even a public
    // method and not called as part of the set session tokens method.
    trace!("Discovering our own user id.");
    let whoami_response = client.whoami().await.map_err(QRCodeLoginError::UserIdDiscovery)?;
    client
        .base_client()
        .activate(
            SessionMeta {
                user_id: whoami_response.user_id,
                device_id: OwnedDeviceId::from(device_id.to_base64()),
            },
            RoomLoadSettings::default(),
            Some(account),
        )
        .await
        .map_err(|error| QRCodeLoginError::SessionTokens(error.into()))?;

    client.oauth().enable_cross_process_lock().await?;

    state.set(LoginProgress::SyncingSecrets);

    // Tell the existing device that we're logged in.
    trace!("Telling the existing device that we successfully logged in.");
    let message = QrAuthMessage::LoginSuccess;
    channel.send_json(&message).await?;

    // Let's wait for the secrets bundle to be sent to us, otherwise we won't be a
    // fully E2EE enabled device.
    trace!("Waiting for the secrets bundle.");
    let bundle = match channel.receive_json().await? {
        QrAuthMessage::LoginSecrets(bundle) => bundle,
        QrAuthMessage::LoginFailure { reason, homeserver } => {
            return Err(QRCodeLoginError::LoginFailure { reason, homeserver });
        }
        message => {
            send_unexpected_message_error(&mut channel).await?;

            return Err(QRCodeLoginError::UnexpectedMessage {
                expected: "m.login.secrets",
                received: message,
            });
        }
    };

    // Import the secrets bundle, this will allow us to sign the device keys with
    // the master key when we upload them.
    client.encryption().import_secrets_bundle_impl(&bundle).await?;

    // Upload the device keys, this will ensure that other devices see us as a fully
    // verified device ass soon as this method returns.
    client
        .encryption()
        .ensure_device_keys_upload()
        .await
        .map_err(QRCodeLoginError::DeviceKeyUpload)?;

    // Run and wait for the E2EE initialization tasks, this will ensure that we
    // ourselves see us as verified and the recovery/backup states will
    // be known. If we did receive all the secrets in the secrets
    // bundle, then backups will be enabled after this step as well.
    client.encryption().spawn_initialization_task(None).await;
    client.encryption().wait_for_e2ee_initialization_tasks().await;

    trace!("successfully logged in and enabled E2EE.");

    // Tell our listener that we're done.
    state.set(LoginProgress::Done);

    // And indeed, we are done with the login.
    Ok(())
}

/// Register the client with the OAuth 2.0 authorization server.
///
/// Returns the authorization server metadata.
async fn register_client(
    oauth: &OAuth,
    registration_data: Option<&ClientRegistrationData>,
) -> Result<AuthorizationServerMetadata, DeviceAuthorizationOAuthError> {
    let server_metadata = oauth.server_metadata().await.map_err(OAuthError::from)?;
    oauth.use_registration_data(&server_metadata, registration_data).await?;

    Ok(server_metadata)
}

async fn request_device_authorization(
    oauth: &OAuth,
    server_metadata: &AuthorizationServerMetadata,
    device_id: Curve25519PublicKey,
) -> Result<StandardDeviceAuthorizationResponse, DeviceAuthorizationOAuthError> {
    let response = oauth
        .request_device_authorization(server_metadata, Some(device_id.to_base64().into()))
        .await?;
    Ok(response)
}

async fn wait_for_tokens(
    oauth: &OAuth,
    server_metadata: &AuthorizationServerMetadata,
    auth_response: &StandardDeviceAuthorizationResponse,
) -> Result<(), DeviceAuthorizationOAuthError> {
    oauth.exchange_device_code(server_metadata, auth_response).await?;
    Ok(())
}

/// Type telling us about the progress of the QR code login.
#[derive(Clone, Debug, Default)]
pub enum LoginProgress<Q> {
    /// We're just starting up, this is the default and initial state.
    #[default]
    Starting,
    /// We have established the secure channel, but need to exchange the
    /// [`CheckCode`] so the channel can be verified to indeed be secure.
    EstablishingSecureChannel(Q),
    /// We're waiting for the OAuth 2.0 authorization server to give us the
    /// access token. This will only happen if the other device allows the
    /// OAuth 2.0 authorization server to do so.
    WaitingForToken {
        /// The user code the OAuth 2.0 authorization server has given us, the
        /// OAuth 2.0 authorization server might ask the other device to
        /// enter this code.
        user_code: String,
    },
    /// We are syncing secrets.
    SyncingSecrets,
    /// The login process has completed.
    Done,
}

/// Named future for logging in by scanning a QR code with the
/// [`OAuth::login_with_qr_code()`] method.
#[derive(Debug)]
pub struct LoginWithQrCode<'a> {
    client: &'a Client,
    registration_data: Option<&'a ClientRegistrationData>,
    qr_code_data: &'a QrCodeData,
    state: SharedObservable<LoginProgress<QrProgress>>,
}

impl LoginWithQrCode<'_> {
    /// Subscribe to the progress of QR code login.
    ///
    /// It's usually necessary to subscribe to this to let the existing device
    /// know about the [`CheckCode`] which is used to verify that the two
    /// devices are communicating in a secure manner.
    pub fn subscribe_to_progress(&self) -> impl Stream<Item = LoginProgress<QrProgress>> + use<> {
        self.state.subscribe()
    }
}

impl<'a> IntoFuture for LoginWithQrCode<'a> {
    type Output = Result<(), QRCodeLoginError>;
    boxed_into_future!(extra_bounds: 'a);

    fn into_future(self) -> Self::IntoFuture {
        Box::pin(async move {
            // Before we get here, the other device has created a new rendezvous session
            // and presented a QR code which this device has scanned.
            // -- MSC4108 Secure channel setup steps 1-3

            // First things first, establish the secure channel. Since we're the one that
            // scanned the QR code, we're certain that the secure channel is
            // secure, under the assumption that we didn't scan the wrong QR code.
            // -- MSC4108 Secure channel setup steps 3-5
            let channel = self.establish_secure_channel().await?;

            trace!("Established the secure channel.");

            // The other side isn't yet sure that it's talking to the right device, show
            // a check code so they can confirm.
            // -- MSC4108 Secure channel setup step 6
            let check_code = channel.check_code().to_owned();
            self.state.set(LoginProgress::EstablishingSecureChannel(QrProgress { check_code }));

            // The user now enters the checkcode on the other device which verifies it
            // and will only facilitate the login if the code matches.
            // -- MSC4108 Secure channel setup step 7

            // Now attempt to finish the login.
            // -- MSC4108 OAuth 2.0 login all steps
            finish_login(self.client, channel, self.registration_data, self.state).await
        })
    }
}

impl<'a> LoginWithQrCode<'a> {
    pub(crate) fn new(
        client: &'a Client,
        qr_code_data: &'a QrCodeData,
        registration_data: Option<&'a ClientRegistrationData>,
    ) -> LoginWithQrCode<'a> {
        LoginWithQrCode { client, registration_data, qr_code_data, state: Default::default() }
    }

    async fn establish_secure_channel(
        &self,
    ) -> Result<EstablishedSecureChannel, SecureChannelError> {
        let http_client = self.client.inner.http_client.inner.clone();

        let channel = EstablishedSecureChannel::from_qr_code(
            http_client,
            self.qr_code_data,
            QrCodeIntent::Login,
        )
        .await?;

        Ok(channel)
    }
}

/// Named future for logging in by generating a QR code with the
/// [`OAuth::login_with_qr_code()`] method.
#[derive(Debug)]
pub struct LoginWithGeneratedQrCode<'a> {
    client: &'a Client,
    registration_data: Option<&'a ClientRegistrationData>,
    state: SharedObservable<LoginProgress<GeneratedQrProgress>>,
}

impl LoginWithGeneratedQrCode<'_> {
    /// Subscribe to the progress of QR code login.
    ///
    /// It's necessary to subscribe to this to show the QR code to the existing
    /// device so it can send the check code back to this device.
    pub fn subscribe_to_progress(
        &self,
    ) -> impl Stream<Item = LoginProgress<GeneratedQrProgress>> + use<> {
        self.state.subscribe()
    }
}

impl<'a> IntoFuture for LoginWithGeneratedQrCode<'a> {
    type Output = Result<(), QRCodeLoginError>;
    boxed_into_future!(extra_bounds: 'a);

    fn into_future(self) -> Self::IntoFuture {
        Box::pin(async move {
            // Establish and verify the secure channel.
            // -- MSC4108 Secure channel setup all steps
            let mut channel = self.establish_secure_channel().await?;

            trace!("Established the secure channel.");

            // Wait for the other device to send us the m.login.protocols message
            // so that we can discover the homeserver to use for logging in.
            // -- MSC4108 OAuth 2.0 login step 1
            let message = channel.receive_json().await?;

            // Verify that the device authorization grant is supported and extract
            // the homeserver URL.
            let homeserver = match message {
                QrAuthMessage::LoginProtocols { protocols, homeserver } => {
                    if !protocols.contains(&LoginProtocolType::DeviceAuthorizationGrant) {
                        channel
                            .send_json(QrAuthMessage::LoginFailure {
                                reason: LoginFailureReason::UnsupportedProtocol,
                                homeserver: None,
                            })
                            .await?;

                        return Err(QRCodeLoginError::LoginFailure {
                            reason: LoginFailureReason::UnsupportedProtocol,
                            homeserver: None,
                        });
                    }

                    homeserver
                }
                _ => {
                    send_unexpected_message_error(&mut channel).await?;

                    return Err(QRCodeLoginError::UnexpectedMessage {
                        expected: "m.login.protocols",
                        received: message,
                    });
                }
            };

            // Change the login homeserver if it is different from the server hosting the
            // secure channel.
            if self.client.homeserver() != homeserver {
                self.client
                    .switch_homeserver_and_re_resolve_well_known(homeserver)
                    .await
                    .map_err(QRCodeLoginError::ServerReset)?;
            }

            // Proceed with logging in.
            // -- MSC4108 OAuth 2.0 login remaining steps
            finish_login(self.client, channel, self.registration_data, self.state).await
        })
    }
}

impl<'a> LoginWithGeneratedQrCode<'a> {
    pub(crate) fn new(
        client: &'a Client,
        registration_data: Option<&'a ClientRegistrationData>,
    ) -> Self {
        Self { client, registration_data, state: Default::default() }
    }

    async fn establish_secure_channel(
        &self,
    ) -> Result<EstablishedSecureChannel, SecureChannelError> {
        let http_client = self.client.inner.http_client.clone();

        // Create a new ephemeral key pair and a rendezvous session to request a login
        // with.
        // -- MSC4108 Secure channel setup steps 1 & 2
        let secure_channel = SecureChannel::login(http_client, &self.client.homeserver()).await?;

        // Extract the QR code data and emit a progress update so that the caller can
        // present the QR code for scanning by the other device.
        // -- MSC4108 Secure channel setup step 3
        let qr_code_data = secure_channel.qr_code_data().clone();
        trace!("Generated QR code.");
        self.state.set(LoginProgress::EstablishingSecureChannel(GeneratedQrProgress::QrReady(
            qr_code_data,
        )));

        // Wait for the secure channel to connect. The other device now needs to scan
        // the QR code and send us the LoginInitiateMessage which we respond to
        // with the LoginOkMessage. -- MSC4108 step 4 & 5
        let channel = secure_channel.connect().await?;

        // The other device now verifies our message, computes the checkcode and
        // displays it. We emit a progress update to let the caller prompt the
        // user to enter the checkcode and feed it back to us.
        // -- MSC4108 Secure channel setup step 6
        trace!("Waiting for checkcode.");
        let (tx, rx) = tokio::sync::oneshot::channel();
        self.state.set(LoginProgress::EstablishingSecureChannel(GeneratedQrProgress::QrScanned(
            CheckCodeSender::new(tx),
        )));

        // Retrieve the entered checkcode and verify it to confirm that the channel is
        // actually secure.
        // -- MSC4108 Secure channel setup step 7
        let check_code = rx.await.map_err(|_| SecureChannelError::CannotReceiveCheckCode)?;
        trace!("Received check code.");
        channel.confirm(check_code)
    }
}

#[cfg(all(test, not(target_family = "wasm")))]
mod test {
    use std::time::Duration;

    use assert_matches2::{assert_let, assert_matches};
    use futures_util::StreamExt;
    use matrix_sdk_base::crypto::types::{
        SecretsBundle,
        qr_login::{Msc4108IntentData, QrCodeIntentData},
    };
    use matrix_sdk_common::executor::spawn;
    use matrix_sdk_test::async_test;
    use serde_json::json;
    use vodozemac::ecies::CheckCode;

    use super::*;
    use crate::{
        authentication::oauth::qrcode::{
            messages::LoginProtocolType,
            secure_channel::{SecureChannel, test::MockedRendezvousServer},
        },
        config::RequestConfig,
        http_client::HttpClient,
        test_utils::{client::oauth::mock_client_metadata, mocks::MatrixMockServer},
    };

    enum AliceBehaviour {
        HappyPath,
        DeclinedProtocol,
        UnexpectedMessage,
        UnexpectedMessageInsteadOfSecrets,
        RefuseSecrets,
        LetSessionExpire,
    }

    /// The possible token responses.
    enum TokenResponse {
        Ok,
        AccessDenied,
        ExpiredToken,
    }

    fn secrets_bundle() -> SecretsBundle {
        let json = json!({
            "cross_signing": {
                "master_key": "rTtSv67XGS6k/rg6/yTG/m573cyFTPFRqluFhQY+hSw",
                "self_signing_key": "4jbPt7jh5D2iyM4U+3IDa+WthgJB87IQN1ATdkau+xk",
                "user_signing_key": "YkFKtkjcsTxF6UAzIIG/l6Nog/G2RigCRfWj3cjNWeM",
            },
        });

        serde_json::from_value(json).expect("We should be able to deserialize a secrets bundle")
    }

    /// This is most of the code that is required to be the other side, the
    /// existing device, of the QR login dance.
    async fn grant_login(
        alice: SecureChannel,
        check_code_receiver: tokio::sync::oneshot::Receiver<CheckCode>,
        behavior: AliceBehaviour,
    ) {
        let alice = alice.connect().await.expect("Alice should be able to connect the channel");

        let check_code =
            check_code_receiver.await.expect("We should receive the check code from bob");

        let mut alice = alice
            .confirm(check_code.to_digit())
            .expect("Alice should be able to confirm the secure channel");

        let message = alice
            .receive_json()
            .await
            .expect("Alice should be able to receive the initial message from Bob");

        assert_let!(QrAuthMessage::LoginProtocol { protocol, .. } = message);
        assert_eq!(protocol, LoginProtocolType::DeviceAuthorizationGrant);

        let message = match behavior {
            AliceBehaviour::DeclinedProtocol => QrAuthMessage::LoginFailure {
                reason: LoginFailureReason::UnsupportedProtocol,
                homeserver: None,
            },
            AliceBehaviour::UnexpectedMessage => QrAuthMessage::LoginDeclined,
            _ => QrAuthMessage::LoginProtocolAccepted,
        };

        alice.send_json(message).await.unwrap();

        let message: QrAuthMessage = alice.receive_json().await.unwrap();
        assert_let!(QrAuthMessage::LoginSuccess = message);

        let message = match behavior {
            AliceBehaviour::UnexpectedMessageInsteadOfSecrets => QrAuthMessage::LoginDeclined,
            AliceBehaviour::RefuseSecrets => QrAuthMessage::LoginFailure {
                reason: LoginFailureReason::DeviceNotFound,
                homeserver: None,
            },
            _ => QrAuthMessage::LoginSecrets(secrets_bundle()),
        };

        alice.send_json(message).await.unwrap();
    }

    #[async_test]
    async fn test_qr_login() {
        let server = MatrixMockServer::new().await;
        let rendezvous_server =
            MockedRendezvousServer::new(server.server(), "abcdEFG12345", Duration::MAX).await;
        let (sender, receiver) = tokio::sync::oneshot::channel();

        let oauth_server = server.oauth();
        oauth_server.mock_server_metadata().ok().expect(1).named("server_metadata").mount().await;
        oauth_server.mock_registration().ok().expect(1).named("registration").mount().await;
        oauth_server
            .mock_device_authorization()
            .ok()
            .expect(1)
            .named("device_authorization")
            .mount()
            .await;
        oauth_server.mock_token().ok().expect(1).named("token").mount().await;

        server.mock_versions().ok().expect(1..).named("versions").mount().await;
        server.mock_who_am_i().ok().expect(1).named("whoami").mount().await;
        server.mock_upload_keys().ok().expect(1).named("upload_keys").mount().await;
        server.mock_query_keys().ok().expect(1).named("query_keys").mount().await;

        let client = HttpClient::new(reqwest::Client::new(), Default::default());
        let alice = SecureChannel::reciprocate(client, &rendezvous_server.homeserver_url)
            .await
            .expect("Alice should be able to create a secure channel.");

        assert_let!(
            QrCodeIntentData::Msc4108 {
                data: Msc4108IntentData::Reciprocate { server_name },
                ..
            } = &alice.qr_code_data().intent_data()
        );

        let bob = Client::builder()
            .server_name_or_homeserver_url(server_name)
            .request_config(RequestConfig::new().disable_retry())
            .build()
            .await
            .expect("We should be able to build the Client object from the URL in the QR code");

        let qr_code = alice.qr_code_data().clone();

        let oauth = bob.oauth();
        let registration_data = mock_client_metadata().into();
        let login_bob = oauth.login_with_qr_code(Some(&registration_data)).scan(&qr_code);
        let mut updates = login_bob.subscribe_to_progress();

        let updates_task = spawn(async move {
            let mut sender = Some(sender);

            while let Some(update) = updates.next().await {
                match update {
                    LoginProgress::EstablishingSecureChannel(QrProgress { check_code }) => {
                        sender
                            .take()
                            .expect("The establishing secure channel update should be received only once")
                            .send(check_code)
                            .expect("Bob should be able to send the check code to Alice");
                    }
                    LoginProgress::Done => break,
                    _ => (),
                }
            }
        });
        let alice_task =
            spawn(async { grant_login(alice, receiver, AliceBehaviour::HappyPath).await });

        // Wait for all tasks to finish.
        login_bob.await.expect("Bob should be able to login");
        alice_task.await.expect("Alice should have completed it's task successfully");
        updates_task.await.unwrap();

        assert!(bob.encryption().cross_signing_status().await.unwrap().is_complete());
        let own_identity =
            bob.encryption().get_user_identity(bob.user_id().unwrap()).await.unwrap().unwrap();

        assert!(own_identity.is_verified());
    }

    async fn grant_login_with_generated_qr(
        alice: &Client,
        qr_receiver: tokio::sync::oneshot::Receiver<QrCodeData>,
        cctx_receiver: tokio::sync::oneshot::Receiver<CheckCodeSender>,
        behavior: AliceBehaviour,
    ) {
        let qr_code_data = qr_receiver.await.expect("Alice should receive the QR code");

        let mut channel = EstablishedSecureChannel::from_qr_code(
            alice.inner.http_client.inner.clone(),
            &qr_code_data,
            QrCodeIntent::Reciprocate,
        )
        .await
        .expect("Alice should be able to establish the secure channel");

        trace!("Established the secure channel.");

        // The other side isn't yet sure that it's talking to the right device, show
        // a check code so they can confirm.
        let check_code = channel.check_code().to_digit();

        let check_code_sender =
            cctx_receiver.await.expect("Alice should receive the CheckCodeSender");

        check_code_sender
            .send(check_code)
            .await
            .expect("Alice should be able to send the check code to Bob");

        // Alice sends m.login.protocols message
        let message = QrAuthMessage::LoginProtocols {
            protocols: vec![LoginProtocolType::DeviceAuthorizationGrant],
            homeserver: alice.homeserver(),
        };
        channel
            .send_json(message)
            .await
            .expect("Alice should be able to send the `m.login.protocols` message to Bob");

        // Alice receives m.login.protocol message
        let message: QrAuthMessage = channel
            .receive_json()
            .await
            .expect("Alice should be able to receive the `m.login.protocol` message from Bob");
        assert_let!(QrAuthMessage::LoginProtocol { protocol, .. } = message);
        assert_eq!(protocol, LoginProtocolType::DeviceAuthorizationGrant);

        // Alice sends m.login.protocol_accepted message
        let message = match behavior {
            AliceBehaviour::DeclinedProtocol => QrAuthMessage::LoginFailure {
                reason: LoginFailureReason::UnsupportedProtocol,
                homeserver: None,
            },
            AliceBehaviour::UnexpectedMessage => QrAuthMessage::LoginDeclined,
            _ => QrAuthMessage::LoginProtocolAccepted,
        };
        channel
            .send_json(message)
            .await
            .expect("Alice should be able to send the `m.login.protocol_accepted` message to Bob");

        let message: QrAuthMessage = channel
            .receive_json()
            .await
            .expect("Alice should be able to receive the `m.login.success` message from Bob");
        assert_let!(QrAuthMessage::LoginSuccess = message);

        // Alice sends m.login.secrets message
        let message = match behavior {
            AliceBehaviour::UnexpectedMessageInsteadOfSecrets => QrAuthMessage::LoginDeclined,
            AliceBehaviour::RefuseSecrets => QrAuthMessage::LoginFailure {
                reason: LoginFailureReason::DeviceNotFound,
                homeserver: None,
            },
            _ => QrAuthMessage::LoginSecrets(secrets_bundle()),
        };
        channel
            .send_json(message)
            .await
            .expect("Alice should be able to send the `m.login.secrets` message to Bob");
    }

    #[async_test]
    async fn test_generated_qr_login() {
        let server = MatrixMockServer::new().await;
        let rendezvous_server =
            MockedRendezvousServer::new(server.server(), "abcdEFG12345", Duration::MAX).await;
        let (qr_sender, qr_receiver) = tokio::sync::oneshot::channel();
        let (cctx_sender, cctx_receiver) = tokio::sync::oneshot::channel();

        let oauth_server = server.oauth();
        oauth_server.mock_server_metadata().ok().expect(1).named("server_metadata").mount().await;
        oauth_server.mock_registration().ok().expect(1).named("registration").mount().await;
        oauth_server
            .mock_device_authorization()
            .ok()
            .expect(1)
            .named("device_authorization")
            .mount()
            .await;
        oauth_server.mock_token().ok().expect(1).named("token").mount().await;

        server.mock_versions().ok().expect(1..).named("versions").mount().await;
        server.mock_who_am_i().ok().expect(1).named("whoami").mount().await;
        server.mock_upload_keys().ok().expect(1).named("upload_keys").mount().await;
        server.mock_query_keys().ok().expect(1).named("query_keys").mount().await;

        let homeserver_url = rendezvous_server.homeserver_url.clone();

        // Create Alice, the existing client, as a logged-in client. They will scan the
        // QR code generated by Bob.
        let alice = server.client_builder().logged_in_with_oauth().build().await;
        assert!(alice.session_meta().is_some(), "Alice should be logged in");

        // Create Bob, the new client. They will generate the QR code.
        let bob = Client::builder()
            .server_name_or_homeserver_url(&homeserver_url)
            .request_config(RequestConfig::new().disable_retry())
            .build()
            .await
            .expect("Should be able to create a client for Bob");

        let secure_channel = SecureChannel::login(bob.inner.http_client.clone(), &homeserver_url)
            .await
            .expect("Bob should be able to create a secure channel");

        assert_matches!(
            secure_channel.qr_code_data().intent_data(),
            QrCodeIntentData::Msc4108 { data: Msc4108IntentData::Login, .. }
        );

        let registration_data = mock_client_metadata().into();
        let bob_oauth = bob.oauth();
        let bob_login = bob_oauth.login_with_qr_code(Some(&registration_data)).generate();
        let mut bob_updates = bob_login.subscribe_to_progress();

        let updates_task = spawn(async move {
            let mut qr_sender = Some(qr_sender);
            let mut cctx_sender = Some(cctx_sender);

            while let Some(update) = bob_updates.next().await {
                match update {
                    LoginProgress::EstablishingSecureChannel(GeneratedQrProgress::QrReady(qr)) => {
                        qr_sender
                            .take()
                            .expect("The establishing secure channel update with a qr code should be received only once")
                            .send(qr)
                            .expect("Bob should be able to send the qr code code to Alice");
                    }
                    LoginProgress::EstablishingSecureChannel(GeneratedQrProgress::QrScanned(
                        cctx,
                    )) => {
                        cctx_sender
                            .take()
                            .expect("The establishing secure channel update with a CheckCodeSender should be received only once")
                            .send(cctx)
                            .expect("Bob should be able to send the qr code code to Alice");
                    }
                    LoginProgress::Done => break,
                    _ => (),
                }
            }
        });

        let alice_task = spawn(async move {
            grant_login_with_generated_qr(
                &alice,
                qr_receiver,
                cctx_receiver,
                AliceBehaviour::HappyPath,
            )
            .await
        });

        // Wait for all tasks to finish.
        bob_login.await.expect("Bob should be able to login");
        alice_task.await.expect("Alice should have completed it's task successfully");
        updates_task.await.unwrap();

        assert!(bob.encryption().cross_signing_status().await.unwrap().is_complete());
        let own_identity =
            bob.encryption().get_user_identity(bob.user_id().unwrap()).await.unwrap().unwrap();

        assert!(own_identity.is_verified());
    }

    #[async_test]
    async fn test_generated_qr_login_with_homeserver_swap() {
        let initial_server = MatrixMockServer::new().await;
        let rendezvous_server =
            MockedRendezvousServer::new(initial_server.server(), "abcdEFG12345", Duration::MAX)
                .await;
        let (qr_sender, qr_receiver) = tokio::sync::oneshot::channel();
        let (cctx_sender, cctx_receiver) = tokio::sync::oneshot::channel();

        let login_server = MatrixMockServer::new().await;
        let oauth_server = login_server.oauth();
        oauth_server.mock_server_metadata().ok().expect(1).named("server_metadata").mount().await;
        oauth_server.mock_registration().ok().expect(1).named("registration").mount().await;
        oauth_server
            .mock_device_authorization()
            .ok()
            .expect(1)
            .named("device_authorization")
            .mount()
            .await;
        oauth_server.mock_token().ok().expect(1).named("token").mount().await;

        initial_server.mock_versions().ok().expect(1..).named("versions").mount().await;

        login_server.mock_well_known().ok().expect(1).named("well_known").mount().await;
        login_server.mock_versions().ok().expect(1..).named("versions").mount().await;
        login_server.mock_who_am_i().ok().expect(1).named("whoami").mount().await;
        login_server.mock_upload_keys().ok().expect(1).named("upload_keys").mount().await;
        login_server.mock_query_keys().ok().expect(1).named("query_keys").mount().await;

        let rendezvous_homeserver_url = rendezvous_server.homeserver_url.clone();

        // Create Alice, the existing client, as a logged-in client. They will scan the
        // QR code generated by Bob.
        let alice = login_server.client_builder().logged_in_with_oauth().build().await;
        assert!(alice.session_meta().is_some(), "Alice should be logged in");

        // Create Bob, the new client. They will generate the QR code.
        let bob = Client::builder()
            .server_name_or_homeserver_url(&rendezvous_homeserver_url)
            .request_config(RequestConfig::new().disable_retry())
            .build()
            .await
            .expect("Should be able to create a client for Bob");

        let secure_channel =
            SecureChannel::login(bob.inner.http_client.clone(), &rendezvous_homeserver_url)
                .await
                .expect("Bob should be able to create a secure channel");

        assert_matches!(
            secure_channel.qr_code_data().intent_data(),
            QrCodeIntentData::Msc4108 { data: Msc4108IntentData::Login, .. }
        );

        // Alice and Bob should have different homeservers configured at the start.
        let initial_server_url = initial_server.server().uri().parse().unwrap();
        assert_eq!(bob.homeserver(), initial_server_url);
        let login_server_url = login_server.server().uri().parse().unwrap();
        assert_eq!(alice.homeserver(), login_server_url);
        assert_ne!(initial_server_url, login_server_url);

        let registration_data = mock_client_metadata().into();
        let bob_oauth = bob.oauth();
        let bob_login = bob_oauth.login_with_qr_code(Some(&registration_data)).generate();
        let mut bob_updates = bob_login.subscribe_to_progress();

        let updates_task = spawn(async move {
            let mut qr_sender = Some(qr_sender);
            let mut cctx_sender = Some(cctx_sender);

            while let Some(update) = bob_updates.next().await {
                match update {
                    LoginProgress::EstablishingSecureChannel(GeneratedQrProgress::QrReady(qr)) => {
                        qr_sender
                            .take()
                            .expect("The establishing secure channel update with a qr code should be received only once")
                            .send(qr)
                            .expect("Bob should be able to send the qr code code to Alice");
                    }
                    LoginProgress::EstablishingSecureChannel(GeneratedQrProgress::QrScanned(
                        cctx,
                    )) => {
                        cctx_sender
                            .take()
                            .expect("The establishing secure channel update with a CheckCodeSender should be received only once")
                            .send(cctx)
                            .expect("Bob should be able to send the qr code code to Alice");
                    }
                    LoginProgress::Done => break,
                    _ => (),
                }
            }
        });

        let alice_task = spawn(async move {
            grant_login_with_generated_qr(
                &alice,
                qr_receiver,
                cctx_receiver,
                AliceBehaviour::HappyPath,
            )
            .await
        });

        // Wait for all tasks to finish.
        bob_login.await.expect("Bob should be able to login");
        alice_task.await.expect("Alice should have completed it's task successfully");
        updates_task.await.unwrap();

        assert!(bob.encryption().cross_signing_status().await.unwrap().is_complete());
        let own_identity =
            bob.encryption().get_user_identity(bob.user_id().unwrap()).await.unwrap().unwrap();

        assert!(own_identity.is_verified());

        // After login, Bob should have switched to the new homeserver.
        assert_eq!(bob.homeserver(), login_server_url);
    }

    async fn test_failure(
        token_response: TokenResponse,
        alice_behavior: AliceBehaviour,
    ) -> Result<(), QRCodeLoginError> {
        let server = MatrixMockServer::new().await;
        let expiration = match alice_behavior {
            AliceBehaviour::LetSessionExpire => Duration::from_secs(2),
            _ => Duration::MAX,
        };
        let rendezvous_server =
            MockedRendezvousServer::new(server.server(), "abcdEFG12345", expiration).await;
        let (sender, receiver) = tokio::sync::oneshot::channel();

        let oauth_server = server.oauth();
        let expected_calls = match alice_behavior {
            AliceBehaviour::LetSessionExpire => 0,
            _ => 1,
        };
        oauth_server
            .mock_server_metadata()
            .ok()
            .expect(expected_calls)
            .named("server_metadata")
            .mount()
            .await;
        oauth_server
            .mock_registration()
            .ok()
            .expect(expected_calls)
            .named("registration")
            .mount()
            .await;
        oauth_server
            .mock_device_authorization()
            .ok()
            .expect(expected_calls)
            .named("device_authorization")
            .mount()
            .await;

        let token_mock = oauth_server.mock_token();
        let token_mock = match token_response {
            TokenResponse::Ok => token_mock.ok(),
            TokenResponse::AccessDenied => token_mock.access_denied(),
            TokenResponse::ExpiredToken => token_mock.expired_token(),
        };
        token_mock.named("token").mount().await;

        server.mock_versions().ok().named("versions").mount().await;
        server.mock_who_am_i().ok().named("whoami").mount().await;

        let client = HttpClient::new(reqwest::Client::new(), Default::default());
        let alice = SecureChannel::reciprocate(client, &rendezvous_server.homeserver_url)
            .await
            .expect("Alice should be able to create a secure channel.");

        assert_let!(
            QrCodeIntentData::Msc4108 {
                data: Msc4108IntentData::Reciprocate { server_name },
                ..
            } = &alice.qr_code_data().intent_data()
        );

        let bob = Client::builder()
            .server_name_or_homeserver_url(server_name)
            .request_config(RequestConfig::new().disable_retry())
            .build()
            .await
            .expect("We should be able to build the Client object from the URL in the QR code");

        let qr_code = alice.qr_code_data().clone();

        let oauth = bob.oauth();
        let registration_data = mock_client_metadata().into();
        let login_bob = oauth.login_with_qr_code(Some(&registration_data)).scan(&qr_code);
        let mut updates = login_bob.subscribe_to_progress();

        let _updates_task = spawn(async move {
            let mut sender = Some(sender);

            while let Some(update) = updates.next().await {
                match update {
                    LoginProgress::EstablishingSecureChannel(QrProgress { check_code }) => {
                        sender
                            .take()
                            .expect("The establishing secure channel update should be received only once")
                            .send(check_code)
                            .expect("Bob should be able to send the check code to Alice");
                    }
                    LoginProgress::Done => break,
                    _ => (),
                }
            }
        });

        if !matches!(alice_behavior, AliceBehaviour::LetSessionExpire) {
            let _alice_task =
                spawn(async move { grant_login(alice, receiver, alice_behavior).await });
        }

        login_bob.await
    }

    async fn test_generated_failure(
        token_response: TokenResponse,
        alice_behavior: AliceBehaviour,
    ) -> Result<(), QRCodeLoginError> {
        let server = MatrixMockServer::new().await;
        let expiration = match alice_behavior {
            AliceBehaviour::LetSessionExpire => Duration::from_secs(2),
            _ => Duration::MAX,
        };
        let rendezvous_server =
            MockedRendezvousServer::new(server.server(), "abcdEFG12345", expiration).await;

        let (qr_sender, qr_receiver) = tokio::sync::oneshot::channel();
        let (cctx_sender, cctx_receiver) = tokio::sync::oneshot::channel();

        let oauth_server = server.oauth();
        let expected_calls = match alice_behavior {
            AliceBehaviour::LetSessionExpire => 0,
            _ => 1,
        };
        oauth_server
            .mock_server_metadata()
            .ok()
            .expect(expected_calls)
            .named("server_metadata")
            .mount()
            .await;
        oauth_server
            .mock_registration()
            .ok()
            .expect(expected_calls)
            .named("registration")
            .mount()
            .await;
        oauth_server
            .mock_device_authorization()
            .ok()
            .expect(expected_calls)
            .named("device_authorization")
            .mount()
            .await;

        let token_mock = oauth_server.mock_token();
        let token_mock = match token_response {
            TokenResponse::Ok => token_mock.ok(),
            TokenResponse::AccessDenied => token_mock.access_denied(),
            TokenResponse::ExpiredToken => token_mock.expired_token(),
        };
        token_mock.named("token").mount().await;

        server.mock_versions().ok().named("versions").mount().await;
        server.mock_who_am_i().ok().named("whoami").mount().await;

        let homeserver_url = rendezvous_server.homeserver_url.clone();

        // Create Alice, the existing client, as a logged-in client. They will scan the
        // QR code generated by Bob.
        let alice = server.client_builder().logged_in_with_oauth().build().await;
        assert!(alice.session_meta().is_some(), "Alice should be logged in");

        // Create Bob, the new client. They will generate the QR code.
        let bob = Client::builder()
            .server_name_or_homeserver_url(&homeserver_url)
            .request_config(RequestConfig::new().disable_retry())
            .build()
            .await
            .expect("Should be able to create a client for Bob");

        let secure_channel = SecureChannel::login(bob.inner.http_client.clone(), &homeserver_url)
            .await
            .expect("Bob should be able to create a secure channel");

        assert_matches!(
            secure_channel.qr_code_data().intent_data(),
            QrCodeIntentData::Msc4108 { data: Msc4108IntentData::Login, .. }
        );

        let registration_data = mock_client_metadata().into();
        let bob_oauth = bob.oauth();
        let bob_login = bob_oauth.login_with_qr_code(Some(&registration_data)).generate();
        let mut bob_updates = bob_login.subscribe_to_progress();

        let _updates_task = spawn(async move {
            let mut qr_sender = Some(qr_sender);
            let mut cctx_sender = Some(cctx_sender);

            while let Some(update) = bob_updates.next().await {
                match update {
                    LoginProgress::EstablishingSecureChannel(GeneratedQrProgress::QrReady(qr)) => {
                        qr_sender
                            .take()
                            .expect("The establishing secure channel update with a qr code should be received only once")
                            .send(qr)
                            .expect("Bob should be able to send the qr code code to Alice");
                    }
                    LoginProgress::EstablishingSecureChannel(GeneratedQrProgress::QrScanned(
                        cctx,
                    )) => {
                        cctx_sender
                            .take()
                            .expect("The establishing secure channel update with a CheckCodeSender should be received only once")
                            .send(cctx)
                            .expect("Bob should be able to send the qr code code to Alice");
                    }
                    LoginProgress::Done => break,
                    _ => (),
                }
            }
        });

        if !matches!(alice_behavior, AliceBehaviour::LetSessionExpire) {
            let _alice_task = spawn(async move {
                grant_login_with_generated_qr(&alice, qr_receiver, cctx_receiver, alice_behavior)
                    .await
            });
        }

        bob_login.await
    }

    #[async_test]
    async fn test_qr_login_refused_access_token() {
        let result = test_failure(TokenResponse::AccessDenied, AliceBehaviour::HappyPath).await;

        assert_let!(Err(QRCodeLoginError::OAuth(e)) = result);
        assert_eq!(
            e.as_request_token_error(),
            Some(&DeviceCodeErrorResponseType::AccessDenied),
            "The server should have told us that access has been denied."
        );
    }

    #[async_test]
    async fn test_generated_qr_login_refused_access_token() {
        let result =
            test_generated_failure(TokenResponse::AccessDenied, AliceBehaviour::HappyPath).await;

        assert_let!(Err(QRCodeLoginError::OAuth(e)) = result);
        assert_eq!(
            e.as_request_token_error(),
            Some(&DeviceCodeErrorResponseType::AccessDenied),
            "The server should have told us that access has been denied."
        );
    }

    #[async_test]
    async fn test_qr_login_expired_token() {
        let result = test_failure(TokenResponse::ExpiredToken, AliceBehaviour::HappyPath).await;

        assert_let!(Err(QRCodeLoginError::OAuth(e)) = result);
        assert_eq!(
            e.as_request_token_error(),
            Some(&DeviceCodeErrorResponseType::ExpiredToken),
            "The server should have told us that access has been denied."
        );
    }

    #[async_test]
    async fn test_generated_qr_login_expired_token() {
        let result =
            test_generated_failure(TokenResponse::ExpiredToken, AliceBehaviour::HappyPath).await;

        assert_let!(Err(QRCodeLoginError::OAuth(e)) = result);
        assert_eq!(
            e.as_request_token_error(),
            Some(&DeviceCodeErrorResponseType::ExpiredToken),
            "The server should have told us that access has been denied."
        );
    }

    #[async_test]
    async fn test_qr_login_declined_protocol() {
        let result = test_failure(TokenResponse::Ok, AliceBehaviour::DeclinedProtocol).await;

        assert_let!(Err(QRCodeLoginError::LoginFailure { reason, .. }) = result);
        assert_eq!(
            reason,
            LoginFailureReason::UnsupportedProtocol,
            "Alice should have told us that the protocol is unsupported."
        );
    }

    #[async_test]
    async fn test_generated_qr_login_declined_protocol() {
        let result =
            test_generated_failure(TokenResponse::Ok, AliceBehaviour::DeclinedProtocol).await;

        assert_let!(Err(QRCodeLoginError::LoginFailure { reason, .. }) = result);
        assert_eq!(
            reason,
            LoginFailureReason::UnsupportedProtocol,
            "Alice should have told us that the protocol is unsupported."
        );
    }

    #[async_test]
    async fn test_qr_login_unexpected_message() {
        let result = test_failure(TokenResponse::Ok, AliceBehaviour::UnexpectedMessage).await;

        assert_let!(Err(QRCodeLoginError::UnexpectedMessage { expected, .. }) = result);
        assert_eq!(expected, "m.login.protocol_accepted");
    }

    #[async_test]
    async fn test_generated_qr_login_unexpected_message() {
        let result =
            test_generated_failure(TokenResponse::Ok, AliceBehaviour::UnexpectedMessage).await;

        assert_let!(Err(QRCodeLoginError::UnexpectedMessage { expected, .. }) = result);
        assert_eq!(expected, "m.login.protocol_accepted");
    }

    #[async_test]
    async fn test_qr_login_unexpected_message_instead_of_secrets() {
        let result =
            test_failure(TokenResponse::Ok, AliceBehaviour::UnexpectedMessageInsteadOfSecrets)
                .await;

        assert_let!(Err(QRCodeLoginError::UnexpectedMessage { expected, .. }) = result);
        assert_eq!(expected, "m.login.secrets");
    }

    #[async_test]
    async fn test_generated_qr_login_unexpected_message_instead_of_secrets() {
        let result = test_generated_failure(
            TokenResponse::Ok,
            AliceBehaviour::UnexpectedMessageInsteadOfSecrets,
        )
        .await;

        assert_let!(Err(QRCodeLoginError::UnexpectedMessage { expected, .. }) = result);
        assert_eq!(expected, "m.login.secrets");
    }

    #[async_test]
    async fn test_qr_login_refuse_secrets() {
        let result = test_failure(TokenResponse::Ok, AliceBehaviour::RefuseSecrets).await;

        assert_let!(Err(QRCodeLoginError::LoginFailure { reason, .. }) = result);
        assert_eq!(reason, LoginFailureReason::DeviceNotFound);
    }

    #[async_test]
    async fn test_generated_qr_login_refuse_secrets() {
        let result = test_generated_failure(TokenResponse::Ok, AliceBehaviour::RefuseSecrets).await;

        assert_let!(Err(QRCodeLoginError::LoginFailure { reason, .. }) = result);
        assert_eq!(reason, LoginFailureReason::DeviceNotFound);
    }

    #[async_test]
    async fn test_qr_login_session_expired() {
        let result = test_failure(TokenResponse::Ok, AliceBehaviour::LetSessionExpire).await;

        assert_matches!(result, Err(QRCodeLoginError::NotFound));
    }

    #[async_test]
    async fn test_generated_qr_login_session_expired() {
        let result =
            test_generated_failure(TokenResponse::Ok, AliceBehaviour::LetSessionExpire).await;

        assert_matches!(result, Err(QRCodeLoginError::NotFound));
    }

    #[async_test]
    async fn test_device_authorization_endpoint_missing() {
        let server = MatrixMockServer::new().await;
        let rendezvous_server =
            MockedRendezvousServer::new(server.server(), "abcdEFG12345", Duration::MAX).await;
        let (sender, receiver) = tokio::sync::oneshot::channel();

        let oauth_server = server.oauth();
        oauth_server
            .mock_server_metadata()
            .ok_without_device_authorization()
            .expect(1)
            .named("server_metadata")
            .mount()
            .await;
        oauth_server.mock_registration().ok().expect(1).named("registration").mount().await;

        server.mock_versions().ok().named("versions").mount().await;
        server.mock_who_am_i().ok().named("whoami").mount().await;

        let client = HttpClient::new(reqwest::Client::new(), Default::default());
        let alice = SecureChannel::reciprocate(client, &rendezvous_server.homeserver_url)
            .await
            .expect("Alice should be able to create a secure channel.");

        assert_let!(
            QrCodeIntentData::Msc4108 {
                data: Msc4108IntentData::Reciprocate { server_name },
                ..
            } = &alice.qr_code_data().intent_data()
        );

        let bob = Client::builder()
            .server_name_or_homeserver_url(server_name)
            .request_config(RequestConfig::new().disable_retry())
            .build()
            .await
            .expect("We should be able to build the Client object from the URL in the QR code");

        let qr_code = alice.qr_code_data().clone();

        let oauth = bob.oauth();
        let registration_data = mock_client_metadata().into();
        let login_bob = oauth.login_with_qr_code(Some(&registration_data)).scan(&qr_code);
        let mut updates = login_bob.subscribe_to_progress();

        let _updates_task = spawn(async move {
            let mut sender = Some(sender);

            while let Some(update) = updates.next().await {
                match update {
                    LoginProgress::EstablishingSecureChannel(QrProgress { check_code }) => {
                        sender
                                .take()
                                .expect("The establishing secure channel update should be received only once")
                                .send(check_code)
                                .expect("Bob should be able to send the check code to Alice");
                    }
                    LoginProgress::Done => break,
                    _ => (),
                }
            }
        });
        let _alice_task =
            spawn(async move { grant_login(alice, receiver, AliceBehaviour::HappyPath).await });
        let error = login_bob.await.unwrap_err();

        assert_matches!(
            error,
            QRCodeLoginError::OAuth(DeviceAuthorizationOAuthError::NoDeviceAuthorizationEndpoint)
        );
    }
}