grpc-js: reject invalid Content-Type requests

This commit implements the following portion of the spec:

If Content-Type does not begin with "application/grpc",
gRPC servers SHOULD respond with HTTP status of
415 (Unsupported Media Type). This will prevent other
HTTP/2 clients from interpreting a gRPC error response,
which uses status 200 (OK), as successful.

packages/grpc-js/src/server.ts

@@ -288,6 +288,22 @@ export class Server {
           return;
         }
 
+        const contentType = headers[http2.constants.HTTP2_HEADER_CONTENT_TYPE];
+
+        if (
+          typeof contentType !== 'string' ||
+          !contentType.startsWith('application/grpc')
+        ) {
+          stream.respond(
+            {
+              [http2.constants.HTTP2_HEADER_STATUS]:
+                http2.constants.HTTP_STATUS_UNSUPPORTED_MEDIA_TYPE,
+            },
+            { endStream: true }
+          );
+          return;
+        }
+
         try {
           const path = headers[http2.constants.HTTP2_HEADER_PATH] as string;
           const handler = this.handlers.get(path);

packages/grpc-js/test/test-server.ts

@@ -19,6 +19,7 @@
 // tslint:disable no-any
 import * as assert from 'assert';
 import * as fs from 'fs';
+import * as http2 from 'http2';
 import * as path from 'path';
 
 import * as grpc from '../src';
@@ -450,4 +451,46 @@ describe('Generic client and server', () => {
       });
     });
   });
+
+  it('responds with HTTP status of 415 on invalid content-type', done => {
+    const server = new Server();
+    const creds = ServerCredentials.createInsecure();
+
+    server.bindAsync('localhost:0', creds, (err, port) => {
+      assert.ifError(err);
+      const client = http2.connect(`http://localhost:${port}`);
+      let count = 0;
+
+      function makeRequest(headers: http2.IncomingHttpHeaders) {
+        const req = client.request(headers);
+        let statusCode: string;
+
+        req.on('response', headers => {
+          statusCode = headers[http2.constants.HTTP2_HEADER_STATUS] as string;
+          assert.strictEqual(
+            statusCode,
+            http2.constants.HTTP_STATUS_UNSUPPORTED_MEDIA_TYPE
+          );
+        });
+
+        req.on('end', () => {
+          assert(statusCode);
+          count++;
+          if (count === 2) {
+            client.close();
+            server.tryShutdown(done);
+          }
+        });
+
+        req.end();
+      }
+
+      server.start();
+
+      // Missing Content-Type header.
+      makeRequest({ ':path': '/' });
+      // Invalid Content-Type header.
+      makeRequest({ ':path': '/', 'content-type': 'application/not-grpc' });
+    });
+  });
 });