---

summary: Distrust servers with too small keys

...

Introduction

============

This module sets the security status of s2s connections to invalid if

their key is too small and their certificate was issued after 2014, per

CA/B Forum guidelines.

Details

=======

Certificate Authorities were no longer allowed to issue certificates

with public keys smaller than 2048 bits (for RSA) after December 31

2013. This module was written to enforce this, as there were some CAs

that were slow to comply. As of 2015, it might not be very relevant

anymore, but still useful for anyone who wants to increase their

security levels.

When a server is determined to have a "too small" key, this module sets

its chain and identity status to "invalid", so Prosody will treat it as

a self-signed certificate istead.

"Too small"

-----------

The definition of "too small" is based on the key type and is taken from

[RFC 4492].

  Type     bits

  ------ ------

  RSA      2048

  DSA      2048

  DH       2048

  EC        233

Compatibility

=============

Works with Prosody 0.9 and later. Requires LuaSec with [support for

inspecting public keys](https://github.com/brunoos/luasec/pull/19).