Uyuni uses SSL certificates to ensure that clients are registered to the correct server.
Every client that uses SSL to register to the Uyuni Server checks that it is connecting to the right server by validating against a server certificate. This process is called an SSL handshake.
During the SSL handshake, the client checks that the hostname in the server certificate matches what it expects. The client also needs to check if the server certificate is trusted.
Certificate authorities (CAs) are certificates that are used to sign other certificates. All certificates must be signed by a certificate authority (CA) in order for them to be considered valid, and for clients to be able to successfully match against them.
In order for SSL authentication to work correctly, the client must trust the root CA. This means that the root CA must be installed on every client.
The default method of SSL authentication is for Uyuni to use self-signed certificates. In this case, Uyuni has generated all the certificates, and the root CA has signed the server certificate directly.
An alternative method is to use an intermediate CA. In this case, the root CA signs the intermediate CA. The intermediate CA can then sign any number of other intermediate CAs, and the final one signs the server certificate. This is referred to as a chained certificate.
If you are using intermediate CAs in a chained certificate, the root CA is installed on the client, and the server certificate is installed on the server. During the SSL handshake, clients must be able to verify the entire chain of intermediate certificates between the root CA and the server certificate, so they must be able to access all the intermediate certificates.
There are two main ways of achieving this. In older versions of Uyuni, by default, all the intermediate CAs are installed on the client. However, you could also configure your services on the server to provide them to the client. In this case, during the SSL handshake, the server presents the server certificate as well as all the intermediate CAs. This mechanims is used now as the new default configuration.
By default, Uyuni uses a self-signed certificate without intermediate CAs. For additional security, you can arrange a third party CA to sign your certificates. Third party CAs perform checks to ensure that the information contained in the certificate is correct. They usually charge an annual fee for this service. Using a third party CA makes certificates harder to spoof, and provides additional protection for your installation. If you have certificates signed by a third party CA, you can import them to your Uyuni installation.
This manual describe the use of SSL certificates in 2 steps
How to create a self-signed certificate with Uyuni tools
How to deploy a certificate on Uyuni Server or Proxy
In case the certificates are provided by a third party instance like an own or external PKI, step 1 can be skipped.