<DRAFT!>

			HOWTO certificates

1. Introduction

How you handle certificates depends a great deal on what your role is.

Your role can be one or several of:

  - User of some client application

  - User of some server application

  - Certificate authority

This file is for users who wish to get a certificate of their own.

Certificate authorities should read https://www.openssl.org/docs/apps/ca.html.

In all the cases shown below, the standard configuration file, as

compiled into openssl, will be used.  You may find it in /etc/,

/usr/local/ssl/ or somewhere else.  By default the file is named

openssl.cnf and is described at https://www.openssl.org/docs/apps/config.html.

You can specify a different configuration file using the

'-config {file}' argument with the commands shown below.

2. Relationship with keys

Certificates are related to public key cryptography by containing a

public key.  To be useful, there must be a corresponding private key

somewhere.  With OpenSSL, public keys are easily derived from private

keys, so before you create a certificate or a certificate request, you

need to create a private key.

Private keys are generated with 'openssl genrsa -out privkey.pem' if

you want a RSA private key, or if you want a DSA private key:

'openssl dsaparam -out dsaparam.pem 2048; openssl gendsa -out privkey.pem dsaparam.pem'.

The private keys created by these commands are not passphrase protected;

it might or might not be the desirable thing.  Further information on how to

create private keys can be found at https://www.openssl.org/docs/HOWTO/keys.txt.

The rest of this text assumes you have a private key in the file privkey.pem.

3. Creating a certificate request

To create a certificate, you need to start with a certificate request

(or, as some certificate authorities like to put it, "certificate

signing request", since that's exactly what they do, they sign it and

give you the result back, thus making it authentic according to their

policies).  A certificate request is sent to a certificate authority

to get it signed into a certificate. You can also sign the certificate

yourself if you have your own certificate authority or create a

self-signed certificate (typically for testing purpose).

The certificate request is created like this:

  openssl req -new -key privkey.pem -out cert.csr

Now, cert.csr can be sent to the certificate authority, if they can

handle files in PEM format.  If not, use the extra argument '-outform'

followed by the keyword for the format to use (see another HOWTO

<formats.txt?>).  In some cases, -outform does not let you output the

certificate request in the right format and you will have to use one

of the various other commands that are exposed by openssl (or get

creative and use a combination of tools).

The certificate authority performs various checks (according to their

policies) and usually waits for payment from you. Once that is

complete, they send you your new certificate.

Section 5 will tell you more on how to handle the certificate you

received.

4. Creating a self-signed test certificate

You can create a self-signed certificate if you don't want to deal

with a certificate authority, or if you just want to create a test

certificate for yourself.  This is similar to creating a certificate

request, but creates a certificate instead of a certificate request.

This is NOT the recommended way to create a CA certificate, see

https://www.openssl.org/docs/apps/ca.html.

  openssl req -new -x509 -key privkey.pem -out cacert.pem -days 1095

5. What to do with the certificate

If you created everything yourself, or if the certificate authority

was kind enough, your certificate is a raw DER thing in PEM format.

Your key most definitely is if you have followed the examples above.

However, some (most?) certificate authorities will encode them with

things like PKCS7 or PKCS12, or something else.  Depending on your

applications, this may be perfectly OK, it all depends on what they

know how to decode.  If not, there are a number of OpenSSL tools to

convert between some (most?) formats.

So, depending on your application, you may have to convert your

certificate and your key to various formats, most often also putting

them together into one file.  The ways to do this is described in

another HOWTO <formats.txt?>, I will just mention the simplest case.

In the case of a raw DER thing in PEM format, and assuming that's all

right for your applications, simply concatenating the certificate and

the key into a new file and using that one should be enough.  With

some applications, you don't even have to do that.

By now, you have your certificate and your private key and can start

using applications that depend on it.

--

Richard Levitte