fix(rest): tidy up host/port parsing and client url building

Author: raymondfeng

packages/rest/src/rest.server.ts

@@ -402,6 +402,20 @@ export class RestServer extends Context implements Server, HttpServerLike {
       'http'
     );
   }
+
+  /**
+   * Parse the host:port string into an object for host and port
+   * @param host The host string
+   */
+  private _parseHostAndPort(host: string | undefined) {
+    host = host || '';
+    host = host.split(',')[0];
+    const portPattern = /:([0-9]+)$/;
+    const port = (host.match(portPattern) || [])[1] || '';
+    host = host.replace(portPattern, '');
+    return {host, port};
+  }
+
   /**
    * Get the URL of the request sent by the client
    * @param request Http request
@@ -413,14 +427,18 @@ export class RestServer extends Context implements Server, HttpServerLike {
     // [::1]
     // 127.0.0.1:3000
     // 127.0.0.1
-    let host =
-      (request.get('x-forwarded-host') || '').split(',')[0] ||
-      request.headers.host!.replace(/:[0-9]+$/, '');
-    let port =
-      (request.get('x-forwarded-port') || '').split(',')[0] ||
-      this.config.port ||
-      (request.headers.host!.match(/:([0-9]+)$/) || [])[1] ||
-      '';
+    let {host, port} = this._parseHostAndPort(
+      request.get('x-forwarded-host') || request.headers.host,
+    );
+
+    const forwardedPort = (request.get('x-forwarded-port') || '').split(',')[0];
+    port = forwardedPort || port;
+
+    if (!host) {
+      // No host detected from http headers. Use the configured values
+      host = this.config.host!;
+      port = this.config.port == null ? '' : this.config.port.toString();
+    }
 
     // clear default ports
     port = protocol === 'https' && port === '443' ? '' : port;

packages/rest/test/integration/rest.server.integration.ts

@@ -391,15 +391,6 @@ paths:
     const app = new Application();
     app.component(RestComponent);
     const server = await app.getServer(RestServer);
-    const greetSpec = {
-      responses: {
-        200: {
-          schema: {type: 'string'},
-          description: 'greeting of the day',
-        },
-      },
-    };
-    server.route(new Route('get', '/greet', greetSpec, function greet() {}));
 
     const response = await createClientForHandler(server.requestHandler)
       .get('/swagger-ui')
@@ -416,6 +407,45 @@ paths:
     expect(response.get('Location')).match(expectedUrl);
   });
 
+  it('honors "x-forwarded-host" headers', async () => {
+    const app = new Application();
+    app.component(RestComponent);
+    const server = await app.getServer(RestServer);
+
+    const response = await createClientForHandler(server.requestHandler)
+      .get('/swagger-ui')
+      .set('x-forwarded-proto', 'http')
+      .set('x-forwarded-host', 'example.com:8080,my.example.com:9080');
+    await server.get(RestBindings.PORT);
+    const expectedUrl = new RegExp(
+      [
+        'https://loopback.io/api-explorer',
+        '\\?url=http://example.com:8080/openapi.json',
+      ].join(''),
+    );
+    expect(response.get('Location')).match(expectedUrl);
+  });
+
+  it('skips port if it is the default for http or https', async () => {
+    const app = new Application();
+    app.component(RestComponent);
+    const server = await app.getServer(RestServer);
+
+    const response = await createClientForHandler(server.requestHandler)
+      .get('/swagger-ui')
+      .set('x-forwarded-proto', 'https')
+      .set('x-forwarded-host', 'example.com')
+      .set('x-forwarded-port', '443');
+    await server.get(RestBindings.PORT);
+    const expectedUrl = new RegExp(
+      [
+        'https://loopback.io/api-explorer',
+        '\\?url=https://example.com/openapi.json',
+      ].join(''),
+    );
+    expect(response.get('Location')).match(expectedUrl);
+  });
+
   it('exposes "GET /swagger-ui" endpoint with apiExplorer.url', async () => {
     const server = await givenAServer({
       rest: {