Use server name instead of homeserver url to allow well-known lookups during QR OIDC reciprocation

spec/integ/rendezvous/MSC4108SignInWithQR.spec.ts

@@ -54,9 +54,7 @@ function makeMockClient(opts: { userId: string; deviceId: string; msc4108Enabled
             return opts.deviceId;
         },
         baseUrl,
-        getHomeserverUrl() {
-            return baseUrl;
-        },
+        getDomain: () => "example.com",
         getDevice: jest.fn(),
         getCrypto: jest.fn(() => crypto),
         getAuthIssuer: jest.fn().mockResolvedValue({ issuer: "https://issuer/" }),
@@ -158,18 +156,18 @@ describe("MSC4108SignInWithQR", () => {
 
             const ourChannel = new MSC4108SecureChannel(ourMockSession);
             const qrCodeData = QrCodeData.from_bytes(
-                await ourChannel.generateCode(QrCodeMode.Reciprocate, client.getHomeserverUrl()),
+                await ourChannel.generateCode(QrCodeMode.Reciprocate, client.getDomain()!),
             );
             const opponentChannel = new MSC4108SecureChannel(opponentMockSession, qrCodeData.public_key);
 
             ourLogin = new MSC4108SignInWithQR(ourChannel, true, client);
             opponentLogin = new MSC4108SignInWithQR(opponentChannel, false);
         });
 
-        it("should be able to connect with opponent and share homeserver url & check code", async () => {
+        it("should be able to connect with opponent and share server name & check code", async () => {
             await Promise.all([
                 expect(ourLogin.negotiateProtocols()).resolves.toEqual({}),
-                expect(opponentLogin.negotiateProtocols()).resolves.toEqual({ homeserverBaseUrl: client.baseUrl }),
+                expect(opponentLogin.negotiateProtocols()).resolves.toEqual({ homeserverBaseUrl: client.getDomain() }),
             ]);
 
             expect(ourLogin.checkCode).toBe(opponentLogin.checkCode);

src/rendezvous/MSC4108SignInWithQR.ts

@@ -145,7 +145,7 @@ export class MSC4108SignInWithQR {
         }
 
         if (this.ourIntent === QrCodeMode.Reciprocate && this.client) {
-            this._code = await this.channel.generateCode(this.ourIntent, this.client.getHomeserverUrl());
+            this._code = await this.channel.generateCode(this.ourIntent, this.client.getDomain()!);
         } else if (this.ourIntent === QrCodeMode.Login) {
             this._code = await this.channel.generateCode(this.ourIntent);
         }
@@ -194,7 +194,7 @@ export class MSC4108SignInWithQR {
                     await this.send<ProtocolsPayload>({
                         type: PayloadType.Protocols,
                         protocols: ["device_authorization_grant"],
-                        homeserver: this.client?.getHomeserverUrl() ?? "",
+                        homeserver: this.client?.getDomain() ?? "",
                     });
                 } else {
                     await this.send<FailurePayload>({

src/rendezvous/channels/MSC4108SecureChannel.ts

@@ -54,11 +54,11 @@ export class MSC4108SecureChannel {
     /**
      * Generate a QR code for the current session.
      * @param mode the mode to generate the QR code in, either `Login` or `Reciprocate`.
-     * @param homeserverBaseUrl the base URL of the homeserver to connect to, required for `Reciprocate` mode.
+     * @param serverName the name of the homeserver to connect to, as defined by server discovery in the spec, required for `Reciprocate` mode.
      */
     public async generateCode(mode: QrCodeMode.Login): Promise<Uint8Array>;
-    public async generateCode(mode: QrCodeMode.Reciprocate, homeserverBaseUrl: string): Promise<Uint8Array>;
-    public async generateCode(mode: QrCodeMode, homeserverBaseUrl?: string): Promise<Uint8Array> {
+    public async generateCode(mode: QrCodeMode.Reciprocate, serverName: string): Promise<Uint8Array>;
+    public async generateCode(mode: QrCodeMode, serverName?: string): Promise<Uint8Array> {
         const { url } = this.rendezvousSession;
 
         if (!url) {
@@ -68,7 +68,7 @@ export class MSC4108SecureChannel {
         return new QrCodeData(
             this.secureChannel.public_key(),
             url,
-            mode === QrCodeMode.Reciprocate ? homeserverBaseUrl : undefined,
+            mode === QrCodeMode.Reciprocate ? serverName : undefined,
         ).to_bytes();
     }