Easy-RSA 3

This document explains how Easy-RSA 3 and each of its assorted features work.

If you are looking for a quickstart with less background or detail, an implementation-specific Howto or Readme may be available in this (the doc/) directory.

Easy-RSA Overview

Easy-RSA is a utility for managing X.509 PKI, or Public Key Infrastructure. A PKI is based on the notion of trusting a particular authority to authenticate a remote peer; for more background on how PKI works, see the Intro-To-PKI document.

The code is written in platform-neutral POSIX shell, allowing use on a wide range of host systems. The official Windows release also comes bundled with the programs necessary to use Easy-RSA. The shell code attempts to limit the number of external programs it depends on. Crypto-related tasks use openssl as the functional backend.

Feature Highlights

Here's a non-exhaustive list of the more notable Easy-RSA features:

  • Easy-RSA is able to manage multiple PKIs, each with their own independent configuration, storage directory, and X.509 extension handling.
  • Multiple Subject Name (X.509 DN field) formatting options are supported. For VPNs, this means a cleaner commonName only setup can be used.
  • A single backend is used across all supported platforms, ensuring that no platform is 'left out' of the rich features. Unix-alikes (BSD, Linux, etc) and Windows are all supported.
  • Easy-RSA's X.509 support includes CRL, CDP, keyUsage/eKu attributes, and additional features. The included support can be changed or extended as an advanced feature.
  • Interactive and automated (batch) modes of operation
  • Flexible configuration: features can be enabled through command-line options, environment variables, a config file, or a combination of these.
  • Built-in defaults allow Easy-RSA to be used without first editing a config file.

Obtaining and Using Easy-RSA

Download and extraction (installation)

Easy-RSA's main program is a script, supported by a couple of config files. As such, there is no formal "installation" required. Preparing to use Easy-RSA is as simple as downloading the compressed package (.tar.gz for Linux/Unix or .zip for Windows) and extract it to a location of your choosing. There is no compiling or OS-dependent setup required.

You should install and run Easy-RSA as a non-root (non-Administrator) account as root access is not required.

Running Easy-RSA

Invoking Easy-RSA is done through your preferred shell. Under Windows, you will use the EasyRSA Start.bat program to provide a POSIX-shell environment suitable for using Easy-RSA.

The basic format for running commands is:

./easyrsa command [ cmd-opts ]

where command is the name of a command to run, and cmd-opts are any options to supply to the command. Some commands have mandatory or optional cmd-opts. Note the leading ./ component of the command: this is required in Unix-like environments and may be a new concept to some Windows users.

General usage and command help can be shown with:

./easyrsa help [ command ]

When run without any command, general usage and a list of available commands are shown; when a command is supplied, detailed help output for that command is shown.

Configuring Easy-RSA

Easy-RSA 3 no longer needs any configuration file prior to operation, unlike earlier versions. However, the vars.example file contains many commented options that can be used to control non-default behavior as required. Reading this file will provide an idea of the basic configuration available. Note that a vars file must be named just vars (without an extension) to actively use it.

Additionally, some options can be defined at runtime with options on the command-line. A full list can be shown with:

./easyrsa help options

Any of these options can appear before the command as required as shown below:

./easyrsa [options] command [ cmd-opts ]

For experts, additional configuration flexibility is available by way of env-vars and custom X.509 extensions. Consult the EasyRSA-Advanced documentation for details

Getting Started: The Basics

Some of the terms used here will be common to those familiar with how PKI works. Instead of describing PKI basics, please consult the document Intro-To-PKI if you need a more basic description of how a PKI works.

Creating an Easy-RSA PKI

In order to do something useful, Easy-RSA needs to first initialize a directory for the PKI. Multiple PKIs can be managed with a single installation of Easy-RSA, but the default directory is called simply "pki" unless otherwise specified.

To create or clear out (re-initialize) a new PKI, use the command:

./easyrsa init-pki

which will create a new, blank PKI structure ready to be used. Once created, this PKI can be used to make a new CA or generate keypairs.

The PKI Directory Structure

An Easy-RSA PKI contains the following directory structure:

  • private/ - dir with private keys generated on this host
  • reqs/ - dir with locally generated certificate requests (for a CA imported requests are stored here)

In a clean PKI no files will exist until, just the bare directories. Commands called later will create the necessary files depending on the operation.

When building a CA, a number of new files are created by a combination of Easy-RSA and (indirectly) openssl. The important CA files are:

  • ca.crt - This is the CA certificate
  • index.txt - This is the "master database" of all issued certs
  • serial - Stores the next serial number (serial numbers increment)
  • private/ca.key - This is the CA private key (security-critical)
  • certs_by_serial/ - dir with all CA-signed certs by serial number
  • issued/ - dir with issued certs by commonName

After Creating a PKI

Once you have created a PKI, the next useful step will be to either create a CA, or generate keypairs for a system that needs them. Continue with the relevant section below.

Using Easy-RSA as a CA

Building the CA

In order to sign requests to produce certificates, you need a CA. To create a new CA in a PKI you have created, run:

./easyrsa build-ca

Be sure to use a strong passphrase to protect the CA private key. Note that you must supply this passphrase in the future when performing signing operations with your CA, so be sure to remember it.

During the creation process, you will also select a name for the CA called the Common Name (CN.) This name is purely for display purposes and can be set as you like.

Importing requests to the CA

Once a CA is built, the PKI is intended to be used to import requests from external systems that are requesting a signed certificate from this CA. In order to sign the request, it must first be imported so Easy-RSA knows about it. This request file must be a standard CSR in PKCS#10 format.

Regardless of the file name to import, Easy-RSA uses a "short name" defined during import to refer to this request. Importing works like this:

./easyrsa import-req /path/to/request.req nameOfRequest

The nameOfRequest should normally refer to the system or person making the request.

Signing a request

Once Easy-RSA has imported a request, it can be reviewed and signed. Every certificate needs a "type" which controls what extensions the certificate gets Easy-RSA ships with 3 possible types: client, server, and ca, described below:

  • client - A TLS client, suitable for a VPN user or web browser (web client)
  • server - A TLS server, suitable for a VPN or web server
  • ca - A subordinate CA, used when chaining multiple CAs together

Additional types of certs may be defined by local sites as needed; see the advanced documentation for details.

Revoking and publishing CRLs

If an issue certificate needs to be revoked, this can be done as follows:

./easyrsa revoke nameOfRequest

To generate a CRL suitable for publishing to systems that use it, run:

./easyrsa gen-crl

Note that this will need to be published or sent to systems that rely on an up-to-date CRL as the certificate is still otherwise valid.

Using Easy-RSA to generate keypairs & requests

Easy-RSA can generate a keypair and certificate request in PKCS#10 format. This request is what a CA needs in order to generate and return a signed certificate.

Ideally you should never generate entity keypairs for a client or server in a PKI you are using for your CA. It is best to separate this process and generate keypairs only on the systems you plan to use them.

Easy-RSA can generate a keypair and request with the following command:

./easyrsa gen-req nameOfRequest

You will then be given a chance to modify the Subject details of your request. Easy-RSA uses the short name supplied on the command-line by default, though you are free to change it if necessary. After providing a passphrase and Subject details, the keypair and request files will be shown.

In order to obtain a signed certificate, the request file must be sent to the CA for signing; this step is obviously not required if a single PKI is used as both the CA and keypair/request generation as the generated request is already "imported."