fix(response interceptor): proxy original response headers (#563)

Author: chimurai

src/handlers/response-interceptor.ts

@@ -31,8 +31,8 @@ export function responseInterceptor(interceptor: Interceptor) {
     _proxyRes.on('data', (chunk) => (buffer = Buffer.concat([buffer, chunk])));
 
     _proxyRes.on('end', async () => {
-      // set original content type from upstream
-      res.setHeader('content-type', originalProxyRes.headers['content-type'] || '');
+      // copy original headers
+      copyHeaders(proxyRes, res);
 
       // call interceptor with intercepted response (buffer)
       const interceptedBuffer = Buffer.from(await interceptor(buffer, originalProxyRes, req, res));
@@ -79,3 +79,33 @@ function decompress(proxyRes: http.IncomingMessage, contentEncoding: string) {
 
   return _proxyRes;
 }
+
+/**
+ * Copy original headers
+ * https://github.com/apache/superset/blob/9773aba522e957ed9423045ca153219638a85d2f/superset-frontend/webpack.proxy-config.js#L78
+ */
+function copyHeaders(originalResponse, response) {
+  response.statusCode = originalResponse.statusCode;
+  response.statusMessage = originalResponse.statusMessage;
+
+  if (response.setHeader) {
+    let keys = Object.keys(originalResponse.headers);
+
+    // ignore chunked, brotli, gzip, deflate headers
+    keys = keys.filter((key) => !['content-encoding', 'transfer-encoding'].includes(key));
+
+    keys.forEach((key) => {
+      let value = originalResponse.headers[key];
+
+      if (key === 'set-cookie') {
+        // remove cookie domain
+        value = Array.isArray(value) ? value : [value];
+        value = value.map((x) => x.replace(/Domain=[^;]+?/i, ''));
+      }
+
+      response.setHeader(key, value);
+    });
+  } else {
+    response.headers = originalResponse.headers;
+  }
+}

test/e2e/response-interceptor.spec.ts

@@ -41,6 +41,32 @@ describe('responseInterceptor()', () => {
     });
   });
 
+  describe('intercept responses with original headers', () => {
+    beforeEach(() => {
+      agent = request(
+        createApp(
+          createProxyMiddleware({
+            target: `http://httpbin.org`,
+            changeOrigin: true, // for vhosted sites, changes host header to match to target's host
+            selfHandleResponse: true,
+            onProxyRes: responseInterceptor(async (responseBuffer, proxyRes, req, res) => {
+              return responseBuffer;
+            }),
+          })
+        )
+      );
+    });
+
+    it('should proxy and return original headers from http://httpbin.org/cookies/set/cookie/monster', async () => {
+      return agent
+        .get(`/cookies/set/cookie/monster`)
+        .expect('Access-Control-Allow-Origin', '*')
+        .expect('Date', /.+/)
+        .expect('set-cookie', /.*cookie=monster.*/)
+        .expect(302);
+    });
+  });
+
   describe('intercept compressed responses', () => {
     beforeEach(() => {
       agent = request(