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diff --git a/openssl/doc/HOWTO/certificates.txt b/openssl/doc/HOWTO/certificates.txt new file mode 100644 index 0000000..65f8fc8 --- /dev/null +++ b/openssl/doc/HOWTO/certificates.txt @@ -0,0 +1,110 @@ +<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 |