mirror of
https://github.com/openssl/openssl.git
synced 2024-12-21 06:09:35 +08:00
67472bd82b
* adds links to various related documents. * fixes a few typos. * rewords a few sentences. Reviewed-by: Richard Levitte <levitte@openssl.org> Reviewed-by: Rich Salz <rsalz@openssl.org>
111 lines
4.6 KiB
Plaintext
111 lines
4.6 KiB
Plaintext
<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
|