node:http: apply joinDuplicateHeaders on HTTP/1 fallback connections

src/js/internal/http1_server_fallback.ts

@@ -291,6 +291,11 @@ function connectionListenerHTTP1(server, socket, options) {
     req.url = url;
     req.method = typeof methodNum === "number" ? allMethods[methodNum] : methodNum;
     req.upgrade = upgrade;
+    // Like Node's parserOnHeadersComplete (and the native dispatcher): _addHeaderLine reads this
+    // off the request when it combines duplicates of a header that is not list-valued.
+    if (server.joinDuplicateHeaders) {
+      req.joinDuplicateHeaders = true;
+    }
     req._addHeaderLines(rawHeaders, rawHeaders.length);
 
     // Node's parserOnIncoming: upgrade only sticks for CONNECT or when an 'upgrade' listener

src/js/node/http2.ts

@@ -6809,6 +6809,9 @@ class Http2SecureServer extends tls.Server {
       this.maxHeaderSize = http1Options.maxHeaderSize;
       this.insecureHTTPParser = http1Options.insecureHTTPParser;
       this.httpValidation = http1Options.httpValidation;
+      const joinDuplicateHeaders = http1Options.joinDuplicateHeaders;
+      if (joinDuplicateHeaders !== undefined) validateBoolean(joinDuplicateHeaders, "options.joinDuplicateHeaders");
+      this.joinDuplicateHeaders = joinDuplicateHeaders;
     }
     if (typeof onRequestHandler === "function") {
       this.on("request", onRequestHandler);

test/js/node/http/node-http.test.ts

@@ -4139,3 +4139,54 @@ it("connectionListener hands off Upgrade and CONNECT like Node", async () => {
     expect(serverSide.destroyed).toBe(true);
   }
 });
+
+it("connectionListener applies the server's joinDuplicateHeaders option like Node", async () => {
+  // Node keeps only the first value of a header it treats as single-valued (Authorization,
+  // Content-Type, ...) unless the server was created with joinDuplicateHeaders; Cookie and unknown
+  // headers are joined either way. A socket fed in through server.emit("connection", ...) is served
+  // by the JS parser path, which has to read the option off the server like the native path does.
+  const rawRequest =
+    "GET / HTTP/1.1\r\nHost: example.test\r\n" +
+    "Authorization: one\r\nAuthorization: two\r\n" +
+    "Content-Type: text/plain\r\nContent-Type: text/html\r\n" +
+    "Cookie: a=1\r\nCookie: b=2\r\n" +
+    "X-Custom: first\r\nX-Custom: second\r\n" +
+    "Connection: close\r\n\r\n";
+
+  async function headersSeenOverEmittedConnection(options: { joinDuplicateHeaders?: boolean }) {
+    const { promise: seen, resolve, reject } = Promise.withResolvers<Record<string, string | undefined>>();
+    const server = createServer(options, (req, res) => {
+      const { authorization, "content-type": contentType, cookie, "x-custom": xCustom } = req.headers;
+      resolve({ authorization, "content-type": contentType, cookie, "x-custom": xCustom as string });
+      res.end();
+    });
+    const [clientSide, serverSide] = duplexPair();
+    clientSide.on("error", reject);
+    serverSide.on("error", reject);
+    serverSide.on("close", () => reject(new Error("the server closed the connection without dispatching the request")));
+    clientSide.resume();
+    server.emit("connection", serverSide);
+    clientSide.write(rawRequest);
+    try {
+      return await seen;
+    } finally {
+      clientSide.destroy();
+      serverSide.destroy();
+    }
+  }
+
+  const joined = {
+    authorization: "one, two",
+    "content-type": "text/plain, text/html",
+    cookie: "a=1; b=2",
+    "x-custom": "first, second",
+  };
+  const firstValueWins = { ...joined, authorization: "one", "content-type": "text/plain" };
+  expect(
+    await Promise.all([
+      headersSeenOverEmittedConnection({ joinDuplicateHeaders: true }),
+      headersSeenOverEmittedConnection({ joinDuplicateHeaders: false }),
+      headersSeenOverEmittedConnection({}),
+    ]),
+  ).toEqual([joined, firstValueWins, firstValueWins]);
+});

test/js/node/http2/node-http2.test.js

@@ -4365,6 +4365,79 @@ it("http2 allowHTTP1 fallback omits the Connection header on a close-delimited r
   }
 });
 
+// Sends a request with two Authorization and two Cookie lines over a TLS connection that negotiated
+// http/1.1 (the allowHTTP1 fallback) and returns what the handler saw, plus the option as stored on
+// the server.
+async function duplicateHeadersSeenOverAllowHTTP1(options) {
+  const server = http2.createSecureServer({ ...TLS_CERT, allowHTTP1: true, ...options }, (req, res) => {
+    res.end(JSON.stringify({ authorization: req.headers.authorization, cookie: req.headers.cookie }));
+  });
+  await new Promise(resolve => server.listen(0, resolve));
+  try {
+    const { promise, resolve, reject } = Promise.withResolvers();
+    const socket = tls.connect(
+      { host: "localhost", port: server.address().port, ca: TLS_CERT.cert, ALPNProtocols: ["http/1.1"] },
+      () =>
+        socket.write(
+          "GET / HTTP/1.1\r\nHost: localhost\r\n" +
+            "Authorization: one\r\nAuthorization: two\r\n" +
+            "Cookie: a=1\r\nCookie: b=2\r\n" +
+            "Connection: close\r\n\r\n",
+        ),
+    );
+    const chunks = [];
+    socket.on("error", reject);
+    socket.on("data", chunk => chunks.push(chunk));
+    socket.on("end", () => resolve(Buffer.concat(chunks).toString()));
+    const raw = await promise;
+    expect(raw).toStartWith("HTTP/1.1 200 OK\r\n");
+    return { server: server.joinDuplicateHeaders, ...JSON.parse(raw.slice(raw.indexOf("\r\n\r\n") + 4)) };
+  } finally {
+    server.close();
+  }
+}
+
+it("http2 allowHTTP1 fallback applies joinDuplicateHeaders from options or options.http1Options like Node", async () => {
+  // Authorization is one of the headers Node keeps only the first value of unless the option is
+  // set; Cookie is joined either way. Node reads the option through
+  // storeHTTPOptions({ ...options, ...options.http1Options }), so http1Options takes precedence.
+  const joined = { authorization: "one, two", cookie: "a=1; b=2" };
+  const firstValueWins = { authorization: "one", cookie: "a=1; b=2" };
+  expect(
+    await Promise.all([
+      duplicateHeadersSeenOverAllowHTTP1({ joinDuplicateHeaders: true }),
+      duplicateHeadersSeenOverAllowHTTP1({ http1Options: { joinDuplicateHeaders: true } }),
+      duplicateHeadersSeenOverAllowHTTP1({ joinDuplicateHeaders: true, http1Options: { joinDuplicateHeaders: false } }),
+      duplicateHeadersSeenOverAllowHTTP1({ joinDuplicateHeaders: false }),
+      duplicateHeadersSeenOverAllowHTTP1({}),
+    ]),
+  ).toEqual([
+    { server: true, ...joined },
+    { server: true, ...joined },
+    { server: false, ...firstValueWins },
+    { server: false, ...firstValueWins },
+    { server: undefined, ...firstValueWins },
+  ]);
+});
+
+it("http2 createSecureServer type-checks joinDuplicateHeaders only when allowHTTP1 is set, like Node", () => {
+  for (const [options, received] of [
+    [{ joinDuplicateHeaders: "yes" }, "type string ('yes')"],
+    [{ http1Options: { joinDuplicateHeaders: 1 } }, "type number (1)"],
+  ]) {
+    expect(() => {
+      http2.createSecureServer({ ...TLS_CERT, allowHTTP1: true, ...options });
+    }).toThrow(
+      expect.objectContaining({
+        code: "ERR_INVALID_ARG_TYPE",
+        message: `The "options.joinDuplicateHeaders" property must be of type boolean. Received ${received}`,
+      }),
+    );
+    // Without allowHTTP1 there is no HTTP/1 side to configure: Node neither validates nor stores it.
+    expect(Object.hasOwn(http2.createSecureServer({ ...TLS_CERT, ...options }), "joinDuplicateHeaders")).toBe(false);
+  }
+});
+
 // close() must not depend on the peer sending a SETTINGS ACK — Node's kMaybeDestroy
 // waits on nghttp2_session_want_write()/want_read(), which does not track outstanding
 // ACKs. A server that never ACKs a client-sent SETTINGS must not stall close().