Protecting against POODLE in node.js

README.md

Google recently announced that there is an exploit in SSLv3, this vulnerability is know as POODLE. There is no other option than to disable SSLv3 in order to combat this major flaw. There have already been guides on how to disable this in different servers. But nothing excised for Node.js yet, until now. In order to resolve this for Node.js we need to use various of undocumented options and modules.

In the index.js file below you can see an example of how you can protect your HTTPS server against the POODLE attack. It uses the secureOptions option to pass in constants in to the SSL context which is created by node.

Start the server locally by running:

sudo node index.js

And see if SSLv3 is correctly disabled by connecting with an openssl client:

openssl s_client -connect 127.0.0.1:443 -ssl3

It should respond with a handshake failure:

CONNECTED(00000003)
47309:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:/SourceCache/OpenSSL098/OpenSSL098-52/src/ssl/s3_pkt.c:546:

If we connect normally, it will just work:

openssl s_client -connect 127.0.0.1:443

index.js

'use strict';

var constants = require('constants')
  , https = require('https')
  , path = require('path')
  , tls = require('tls')
  , fs = require('fs');

//
// https and tls support the same createServer options, so it doesn't
// matter which one you create as long as you supply the `secureOptions`
//
https.createServer({
  //
  // This is the default secureProtocol used by Node.js, but it might be
  // sane to specify this by default as it's required if you want to
  // remove supported protocols from the list. This protocol supports:
  //
  // - SSLv2, SSLv3, TLSv1, TLSv1.1 and TLSv1.2
  //
  secureProtocol: 'SSLv23_method',

  //
  // Supply `SSL_OP_NO_SSLv3` constant as secureOption to disable SSLv3
  // from the list of supported protocols that SSLv23_method supports.
  //
  secureOptions: constants.SSL_OP_NO_SSLv3,

  cert: fs.readFileSync(path.join(__dirname, 'ssl', 'server.crt')),
  key: fs.readFileSync(path.join(__dirname, 'ssl', 'server.key')),
}, function (req, res) {
  res.end('works');
}).listen(443);

I just discovered that these options aren't documented under crypto.createCredentials() where they are needed for Haraka (because we have to do the TLS upgrade on a plaintext connection). I'll post an issue or PR to the core docs.

@ploer Agreed

@ploer that's possible but you can also just set a different secureProtocol if you don't want to support any of the SSLv* versions.

We have implemented the changes above but now when requests come into the server node crashes with the following error:

events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: 140314695460672:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:../deps/openssl/openssl/ssl/s3_pkt.c:1256:SSL alert number 40

    at SlabBuffer.use (tls.js:232:18)
    at CleartextStream.read [as _read] (tls.js:452:29)
    at CleartextStream.Readable.read (_stream_readable.js:320:10)
    at EncryptedStream.write [as _write] (tls.js:366:25)
    at doWrite (_stream_writable.js:221:10)
    at writeOrBuffer (_stream_writable.js:211:5)
    at EncryptedStream.Writable.write (_stream_writable.js:180:11)
    at write (_stream_readable.js:583:24)
    at flow (_stream_readable.js:592:7)
    at Socket.pipeOnReadable (_stream_readable.js:624:5)
    at Socket.EventEmitter.emit (events.js:92:17)

Has anyone run into this before and found a solution? We have tested and verified that our node server no longer allows SSL3 but as soon as something tries to communicate that way the above happens.

Ignore my above comment, figured out the problem. We had a method that would post back to another server (in some cases) that was forcing SSLv3. Problem solved.