login: implement remoteauth (QR code login)

pkg/connector/login.go

@@ -27,6 +27,11 @@ const LoginStepIDComplete = "fi.mau.discord.login.complete"
 
 func (d *DiscordConnector) GetLoginFlows() []bridgev2.LoginFlow {
 	return []bridgev2.LoginFlow{
+		{
+			ID:          LoginFlowIDRemoteAuth,
+			Name:        "QR Code",
+			Description: "Scan a QR code with the Discord mobile app to log in.",
+		},
 		{
 			ID:          LoginFlowIDToken,
 			Name:        "Token",
@@ -36,9 +41,12 @@ func (d *DiscordConnector) GetLoginFlows() []bridgev2.LoginFlow {
 }
 
 func (d *DiscordConnector) CreateLogin(ctx context.Context, user *bridgev2.User, flowID string) (bridgev2.LoginProcess, error) {
-	if flowID != LoginFlowIDToken {
+	switch flowID {
-		return nil, fmt.Errorf("unknown login flow ID")
+	case LoginFlowIDToken:
+		return &DiscordTokenLogin{connector: d, User: user}, nil
+	case LoginFlowIDRemoteAuth:
+		return &DiscordRemoteAuthLogin{connector: d, User: user}, nil
+	default:
+		return nil, fmt.Errorf("unknown discord login flow id")
 	}
-
-	return &DiscordTokenLogin{connector: d, User: user}, nil
 }

pkg/connector/login_remoteauth.go

@@ -0,0 +1,189 @@
+// mautrix-discord - A Matrix-Discord puppeting bridge.
+// Copyright (C) 2024 Tulir Asokan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package connector
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/bwmarrin/discordgo"
+	"github.com/rs/zerolog"
+	"go.mau.fi/mautrix-discord/pkg/remoteauth"
+	"maunium.net/go/mautrix/bridgev2"
+	"maunium.net/go/mautrix/bridgev2/database"
+	"maunium.net/go/mautrix/bridgev2/networkid"
+)
+
+const LoginFlowIDRemoteAuth = "fi.mau.discord.login.remote_auth"
+
+type DiscordRemoteAuthLogin struct {
+	connector *DiscordConnector
+	User      *bridgev2.User
+
+	Session *discordgo.Session
+
+	remoteAuthClient *remoteauth.Client
+	qrChan           chan string
+	doneChan         chan struct{}
+}
+
+var _ bridgev2.LoginProcessDisplayAndWait = (*DiscordRemoteAuthLogin)(nil)
+
+func (dl *DiscordRemoteAuthLogin) Start(ctx context.Context) (*bridgev2.LoginStep, error) {
+	log := zerolog.Ctx(ctx)
+
+	log.Debug().Msg("Creating new remoteauth client")
+	client, err := remoteauth.New()
+	if err != nil {
+		return nil, fmt.Errorf("couldn't create Discord remoteauth client: %w", err)
+	}
+
+	dl.remoteAuthClient = client
+
+	dl.qrChan = make(chan string)
+	dl.doneChan = make(chan struct{})
+
+	log.Info().Msg("Starting the QR code login process")
+	err = client.Dial(ctx, dl.qrChan, dl.doneChan)
+	if err != nil {
+		log.Err(err).Msg("Couldn't connect to Discord remoteauth websocket")
+		close(dl.qrChan)
+		close(dl.doneChan)
+		return nil, fmt.Errorf("couldn't connect to Discord remoteauth websocket: %w", err)
+	}
+
+	log.Info().Msg("Waiting for QR code to be ready")
+
+	select {
+	case qrCode := <-dl.qrChan:
+		log.Info().Int("qr_code_data_len", len(qrCode)).Msg("Received QR code, creating login step")
+
+		return &bridgev2.LoginStep{
+			Type:         bridgev2.LoginStepTypeDisplayAndWait,
+			StepID:       "fi.mau.discord.qr",
+			Instructions: "On your phone, find “Scan QR Code” in the official Discord mobile app’s settings.",
+			DisplayAndWaitParams: &bridgev2.LoginDisplayAndWaitParams{
+				Type: bridgev2.LoginDisplayTypeQR,
+				Data: qrCode,
+			},
+		}, nil
+	case <-ctx.Done():
+		log.Debug().Msg("Cancelled while waiting for QR code")
+		return nil, nil
+	}
+}
+
+// Wait implements bridgev2.LoginProcessDisplayAndWait.
+func (dl *DiscordRemoteAuthLogin) Wait(ctx context.Context) (*bridgev2.LoginStep, error) {
+	if dl.doneChan == nil {
+		panic("can't wait for discord remoteauth without a doneChan")
+	}
+
+	log := zerolog.Ctx(ctx)
+
+	log.Debug().Msg("Waiting for remoteauth")
+	select {
+	case <-dl.doneChan:
+		user, err := dl.remoteAuthClient.Result()
+		if err != nil {
+			log.Err(err).Msg("Discord remoteauth failed")
+			return nil, fmt.Errorf("Discord remoteauth failed: %w", err)
+		}
+		log.Debug().Msg("Discord remoteauth succeeded")
+
+		return dl.finalizeSuccessfulLogin(ctx, user)
+	case <-ctx.Done():
+		log.Debug().Msg("Cancelled while waiting for remoteauth to complete")
+		return nil, nil
+	}
+}
+
+func (dl *DiscordRemoteAuthLogin) finalizeSuccessfulLogin(ctx context.Context, user remoteauth.User) (*bridgev2.LoginStep, error) {
+	log := zerolog.Ctx(ctx)
+
+	session, err := discordgo.New(user.Token)
+	if err != nil {
+		return nil, fmt.Errorf("couldn't create discord session from successful remoteauth: %w", err)
+	}
+
+	client := &DiscordClient{
+		connector: dl.connector,
+		Session:   session,
+	}
+	client.SetUp(ctx, nil)
+	err = client.connect(ctx)
+
+	softlyClose := func() {
+		log.Debug().Msg("Softly closing session due to error after successful remoteauth")
+		err := dl.Session.Close()
+		if err != nil {
+			log.Err(err).Msg("Couldn't softly close session due to error after successful remoteauth")
+		}
+	}
+	if err != nil {
+		softlyClose()
+		return nil, fmt.Errorf("couldn't connect to Discord: %w", err)
+	}
+	// At this point we've opened a WebSocket connection to the gateway, received
+	// a READY packet, and know who we are.
+	discordUser := session.State.User
+	dl.Session = session
+
+	ul, err := dl.User.NewLogin(ctx, &database.UserLogin{
+		ID: networkid.UserLoginID(user.UserID),
+		Metadata: &UserLoginMetadata{
+			Token:            user.Token,
+			HeartbeatSession: discordgo.NewHeartbeatSession(),
+		},
+	}, &bridgev2.NewLoginParams{
+		DeleteOnConflict: true,
+		LoadUserLogin: func(ctx context.Context, ul *bridgev2.UserLogin) error {
+			ul.Client = client
+			client.UserLogin = ul
+
+			// Only now that we have a UserLogin can we begin syncing.
+			client.BeginSyncingIfUserLoginPresent(ctx)
+			return nil
+		},
+	})
+	if err != nil {
+		softlyClose()
+		return nil, fmt.Errorf("couldn't create login after successful remoteauth: %w", err)
+	}
+	zerolog.Ctx(ctx).Info().
+		Str("user_id", discordUser.ID).
+		Str("user_username", discordUser.Username).
+		Msg("Connected to Discord during login")
+
+	return &bridgev2.LoginStep{
+		Type:         bridgev2.LoginStepTypeComplete,
+		StepID:       LoginStepIDComplete,
+		Instructions: fmt.Sprintf("Logged in as %s", user.Username),
+		CompleteParams: &bridgev2.LoginCompleteParams{
+			UserLoginID: ul.ID,
+			UserLogin:   ul,
+		},
+	}, nil
+}
+
+func (dl *DiscordRemoteAuthLogin) Cancel() {
+	dl.User.Log.Debug().Msg("Discord remoteauth cancelled")
+
+	// remoteauth.Client doesn't seem to expose a cancellation method right now.
+	close(dl.doneChan)
+	close(dl.qrChan)
+}