AcceSSL

Scalable software Security Module⁠ for OpenSSL.

Why would I want it?

To be a little bit more secure. To be able to scale performance of SSL layer if you need it.

How does it work?

RSA public and private key operations in OpenSSL are relayed via UDP to AcceSSL workers which compute the result and return it to OpenSSL. AcceSSL uses OpenSSL engine mechanism⁠, so your server software needs to support it. Newer versions of Apache HTTP server and nginx support it out of the box.

How scalable is it?

One worker process can handle multiple clients (i.e. OpenSSL-based servers, like nginx). Also OpenSSL-based servers can utilize many AcceSSL workers. Unfortunately OpenSSL API for RSA operations is synchronous. It means you need at least that many threads/processes in OpenSSL-based server as there are AcceSSL workers to utilize all workers.

Unscientific benchmarks show that you could scale on Amazon EC2 to 50000 1024-bit RSA private operations per second. More benchmarks will follow.

Is it secure?

Hopefully a bit more secure than storing your private key on Internet-facing machine. Private keys are stored on AcceSSL workers only, and servers connected to the Internet store only public key. On the other hand the decrypted payload is transmitted in clear text over UDP between OpenSSL client and AcceSSL worker. For more secure setup you could consider physically separate network for AcceSSL traffic.

nginx example

Using Ubuntu 14.04 as base platform:

• install nginx and AcceSSL on Web-server

  sudo apt-get install nginx
  sudo dpkg -i accessl_0.1_amd64.deb
  

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• install AcceSSL on another machine that will act as a worker

  sudo dpkg -i accessl_0.1_amd64.deb
  

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• obtain SSL keys

  For the rest of tutorial I'll assume you have public key server.crt on Web-server machine and private key in server.key.

• run twice as many workers as there cores on AcceSSL machine

  worker -p 10000 -k server.key &
  worker -p 10001 -k server.key &
  ...
  worker -p 1000N -k server.key &
  

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• run accessld on Web-server machine specifying all the workers

  sudo accessld -w WORKER_IP:10000 -w WORKER_IP:10001 ... -w WORKER_IP:1000N &
  

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• convert your server.crt into a stub-key, that can be loaded by nginx:

  crt2key server.crt server.stubkey
  

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• configure nginx to use AcceSSL

  add

  ssl_engine accessl;
  

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  to /etc/nginx/nginx.conf in global section (outside any {})

• configure nginx site to use certificate and stubkey

  ssl_certificate server.crt;
  ssl_certificate_key server.stubkey;
  

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• restart nginx

  sudo service nginx restart
  

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Supported platforms

Linux 64-bit. Currently tested only on Ubuntu 14.04. Should be able to compile on Mac OS X 10.9

TODO

Quite a lot actually.

License

Affero GPL⁠. Contact me if you'd like another license.