This is the page of the MemberManual that describes how to generate a valid SSL cert.
Making a cert for use with Domtool
If you are creating an SSL certificate to use for a web virtual host via DomTool, then you should generate a single output file instead of separate .crt and .key files.
Here is an example. DAYS indicates the number of days that you want the certificate to be valid. FILE is the filename of the certificate that will be generated: it should end in ".pem". The certificate should be placed somewhere in your home directory, like "~/certs", for example.
openssl req -x509 -newkey rsa:1024 -keyout FILE -out FILE -days DAYS -nodes
Here is an explanation of the parameters that you will be asked to provide.
Common Name: This is the domain that goes with the certificate. It can be either a single name (i.e. "yourdomain.org"), or a wildcard domain (like "*.yourdomain.org"). The wildcard domain is used for sharing the same certificate in multiple subdomains of your domain.
Organization: This can be anything you want. It is often the full name or description of your organization or website.
Organizational Unit: This can be anything you want. It can be left blank.
Making a self-signed cert
To create a self-signed SSL cerificate in file.crt with key in file.key, you can run:
openssl req -x509 -newkey rsa:1024 -keyout file.key -out file.crt -days 9999 -nodes