http: check reason chars in writeHead

Previously, the reason argument passed to ServerResponse#writeHead was
not being properly validated.  One could pass CRLFs which could lead to
http response splitting. This commit changes the behavior to throw an
error in the event any invalid characters are included in the reason.

CVE-2016-5325

PR-URL: https://github.com/nodejs/node-private/pull/60
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>

lib/_http_server.js

@@ -191,6 +191,9 @@ ServerResponse.prototype.writeHead = function(statusCode, reason, obj) {
   if (statusCode < 100 || statusCode > 999)
     throw new RangeError(`Invalid status code: ${statusCode}`);
 
+  if (common._checkInvalidHeaderChar(this.statusMessage))
+    throw new Error('Invalid character in statusMessage.');
+
   var statusLine = 'HTTP/1.1 ' + statusCode.toString() + ' ' +
                    this.statusMessage + CRLF;
 

test/parallel/test-http-status-reason-invalid-chars.js

@@ -0,0 +1,46 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+
+function explicit(req, res) {
+  assert.throws(() => {
+    res.writeHead(200, `OK\r\nContent-Type: text/html\r\n`);
+  }, /Invalid character in statusMessage/);
+
+  assert.throws(() => {
+    res.writeHead(200, 'OK\u010D\u010AContent-Type: gotcha\r\n');
+  }, /Invalid character in statusMessage/);
+
+  res.statusMessage = 'OK';
+  res.end();
+}
+
+function implicit(req, res) {
+  assert.throws(() => {
+    res.statusMessage = `OK\r\nContent-Type: text/html\r\n`;
+    res.writeHead(200);
+  }, /Invalid character in statusMessage/);
+  res.statusMessage = 'OK';
+  res.end();
+}
+
+const server = http.createServer((req, res) => {
+  if (req.url === '/explicit') {
+    explicit(req, res);
+  } else {
+    implicit(req, res);
+  }
+}).listen(common.PORT, common.mustCall(() => {
+  const url = `http://localhost:${common.PORT}`;
+  let left = 2;
+  const check = common.mustCall((res) => {
+    left--;
+    assert.notEqual(res.headers['content-type'], 'text/html');
+    assert.notEqual(res.headers['content-type'], 'gotcha');
+    if (left === 0) server.close();
+  }, 2);
+  http.get(`${url}/explicit`, check).end();
+  http.get(`${url}/implicit`, check).end();
+}));