http,https: protect against slow headers attack

CVE-2018-12122

An attacker can send a char/s within headers and exahust the resources
(file descriptors) of a system even with a tight max header length
protection. This PR destroys a socket if it has not received the headers
in 40s.

PR-URL: nodejs-private/node-private#152
Ref: nodejs-private/node-private#144
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: mcollina

doc/api/http.md

@@ -848,6 +848,26 @@ for handling socket timeouts.
 
 Returns `server`.
 
+### server.headersTimeout
+<!-- YAML
+added: REPLACEME
+-->
+
+* {number} **Default:** `40000`
+
+Limit the amount of time the parser will wait to receive the complete HTTP
+headers.
+
+In case of inactivity, the rules defined in [server.timeout][] apply. However,
+that inactivity based timeout would still allow the connection to be kept open
+if the headers are being sent very slowly (by default, up to a byte per 2
+minutes). In order to prevent this, whenever header data arrives an additional
+check is made that more than `server.headersTimeout` milliseconds has not
+passed since the connection was established. If the check fails, a `'timeout'`
+event is emitted on the server object, and (by default) the socket is destroyed.
+See [server.timeout][] for more information on how timeout behaviour can be
+customised.
+
 ### server.timeout
 <!-- YAML
 added: v0.9.12

doc/api/https.md

@@ -23,6 +23,12 @@ added: v0.3.4
 This class is a subclass of `tls.Server` and emits events same as
 [`http.Server`][]. See [`http.Server`][] for more information.
 
+### server.headersTimeout
+
+- {number} **Default:** `40000`
+
+See [`http.Server#headersTimeout`][].
+
 ### server.setTimeout([msecs][, callback])
 <!-- YAML
 added: v0.11.2
@@ -233,6 +239,7 @@ const req = https.request(options, (res) => {
 [`Buffer`]: buffer.html#buffer_buffer
 [`globalAgent`]: #https_https_globalagent
 [`http.Agent`]: http.html#http_class_http_agent
+[`http.Server#headersTimeout`]: http.html#http_server_headerstimeout
 [`http.close()`]: http.html#http_server_close_callback
 [`http.get()`]: http.html#http_http_get_options_callback
 [`http.listen()`]: http.html#http_server_listen_port_hostname_backlog_callback

lib/_http_outgoing.js

@@ -30,20 +30,33 @@ const automaticHeaders = {
 };
 
 
-var dateCache;
+var nowCache;
+var utcCache;
+
+function nowDate() {
+  if (!nowCache) cache();
+  return nowCache;
+}
+
 function utcDate() {
-  if (!dateCache) {
-    var d = new Date();
-    dateCache = d.toUTCString();
-    timers.enroll(utcDate, 1000 - d.getMilliseconds());
-    timers._unrefActive(utcDate);
-  }
-  return dateCache;
+  if (!utcCache) cache();
+  return utcCache;
 }
-utcDate._onTimeout = function() {
-  dateCache = undefined;
+
+function cache() {
+  const d = new Date();
+  nowCache = d.valueOf();
+  utcCache = d.toUTCString();
+  timers.enroll(cache, 1000 - d.getMilliseconds());
+  timers._unrefActive(cache);
+}
+
+cache._onTimeout = function() {
+  nowCache = undefined;
+  utcCache = undefined;
 };
 
+exports.nowDate = nowDate;
 
 function OutgoingMessage() {
   Stream.call(this);

lib/_http_server.js

@@ -13,6 +13,7 @@ const continueExpression = common.continueExpression;
 const chunkExpression = common.chunkExpression;
 const httpSocketSetup = common.httpSocketSetup;
 const OutgoingMessage = require('_http_outgoing').OutgoingMessage;
+const nowDate = require('_http_outgoing').nowDate;
 
 const STATUS_CODES = exports.STATUS_CODES = {
   100: 'Continue',
@@ -244,6 +245,7 @@ function Server(requestListener) {
   this.timeout = 2 * 60 * 1000;
 
   this._pendingResponseData = 0;
+  this.headersTimeout = 40 * 1000; // 40 seconds
 }
 util.inherits(Server, net.Server);
 
@@ -317,6 +319,9 @@ function connectionListener(socket) {
   var parser = parsers.alloc();
   parser.reinitialize(HTTPParser.REQUEST);
   parser.socket = socket;
+
+  // We are starting to wait for our headers.
+  parser.parsingHeadersStart = nowDate();
   socket.parser = parser;
   parser.incoming = null;
 
@@ -374,6 +379,20 @@ function connectionListener(socket) {
   function onParserExecute(ret, d) {
     socket._unrefTimer();
     debug('SERVER socketOnParserExecute %d', ret);
+
+    var start = parser.parsingHeadersStart;
+
+    // If we have not parsed the headers, destroy the socket
+    // after server.headersTimeout to protect from DoS attacks.
+    // start === 0 means that we have parsed headers.
+    if (start !== 0 && nowDate() - start > self.headersTimeout) {
+      var serverTimeout = self.emit('timeout', socket);
+
+      if (!serverTimeout)
+        socket.destroy();
+      return;
+    }
+
     onParserExecuteCommon(ret, undefined);
   }
 
@@ -442,7 +461,6 @@ function connectionListener(socket) {
     }
   }
 
-
   // The following callback is issued after the headers have been read on a
   // new message. In this callback we setup the response object and pass it
   // to the user.

lib/https.js

@@ -37,6 +37,8 @@ function Server(opts, requestListener) {
   });
 
   this.timeout = 2 * 60 * 1000;
+
+  this.headersTimeout = 40 * 1000; // 40 seconds
 }
 inherits(Server, tls.Server);
 exports.Server = Server;

test/parallel/test-http-slow-headers.js

@@ -0,0 +1,56 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const { createServer } = require('http');
+const { connect } = require('net');
+
+// This test validates that the 'timeout' event fires
+// after server.headersTimeout.
+
+const headers =
+  'GET / HTTP/1.1\r\n' +
+  'Host: localhost\r\n' +
+  'Agent: node\r\n';
+
+const server = createServer(common.mustNotCall());
+let sendCharEvery = 1000;
+
+// 40 seconds is the default
+assert.strictEqual(server.headersTimeout, 40 * 1000);
+
+// Pass a REAL env variable to shortening up the default
+// value which is 40s otherwise this is useful for manual
+// testing
+if (!process.env.REAL) {
+  sendCharEvery = common.platformTimeout(10);
+  server.headersTimeout = 2 * sendCharEvery;
+}
+
+server.once('timeout', common.mustCall((socket) => {
+  socket.destroy();
+}));
+
+server.listen(0, common.mustCall(() => {
+  const client = connect(server.address().port);
+  client.write(headers);
+  client.write('X-CRASH: ');
+
+  const interval = setInterval(() => {
+    client.write('a');
+  }, sendCharEvery);
+
+  client.resume();
+
+  const onClose = common.mustCall(() => {
+    client.removeListener('close', onClose);
+    client.removeListener('error', onClose);
+    client.removeListener('end', onClose);
+    clearInterval(interval);
+    server.close();
+  });
+
+  client.on('error', onClose);
+  client.on('close', onClose);
+  client.on('end', onClose);
+}));

test/parallel/test-https-slow-headers.js

@@ -0,0 +1,69 @@
+'use strict';
+
+const common = require('../common');
+const { readKey } = require('../common/fixtures');
+
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const assert = require('assert');
+const { createServer } = require('https');
+const { connect } = require('tls');
+
+// This test validates that the 'timeout' event fires
+// after server.headersTimeout.
+
+const headers =
+  'GET / HTTP/1.1\r\n' +
+  'Host: localhost\r\n' +
+  'Agent: node\r\n';
+
+const server = createServer({
+  key: readKey('agent1-key.pem'),
+  cert: readKey('agent1-cert.pem'),
+  ca: readKey('ca1-cert.pem'),
+}, common.mustNotCall());
+
+let sendCharEvery = 1000;
+
+// 40 seconds is the default
+assert.strictEqual(server.headersTimeout, 40 * 1000);
+
+// pass a REAL env variable to shortening up the default
+// value which is 40s otherwise
+// this is useful for manual testing
+if (!process.env.REAL) {
+  sendCharEvery = common.platformTimeout(10);
+  server.headersTimeout = 2 * sendCharEvery;
+}
+
+server.once('timeout', common.mustCall((socket) => {
+  socket.destroy();
+}));
+
+server.listen(0, common.mustCall(() => {
+  const client = connect({
+    port: server.address().port,
+    rejectUnauthorized: false
+  });
+  client.write(headers);
+  client.write('X-CRASH: ');
+
+  const interval = setInterval(() => {
+    client.write('a');
+  }, sendCharEvery);
+
+  client.resume();
+
+  const onClose = common.mustCall(() => {
+    client.removeListener('close', onClose);
+    client.removeListener('error', onClose);
+    client.removeListener('end', onClose);
+    clearInterval(interval);
+    server.close();
+  });
+
+  client.on('error', onClose);
+  client.on('close', onClose);
+  client.on('end', onClose);
+}));