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Chapter 4. SSL Infrastructure
For Red Hat Satellite customers, security concerns are of the utmost importance. One of the strengths of Red Hat Satellite is its ability to process every single request over Secure Sockets Layer, or SSL. To maintain this level of security, customers installing Red Hat Satellite within their infrastructures must generate custom SSL keys and certificates.
Manual creation and deployment of SSL keys and certificates can be quite involved. Both the Red Hat Proxy Server and the Red Hat Satellite Server allows users to build their own SSL keys and certificates based on their own private Certificate Authority (CA) during installation. In addition, a separate command line utility, the Red Hat Satellite SSL Maintenance Tool, exists for this purpose. Regardless, these keys and certificates must then be deployed to all systems within the managed infrastructure. In many cases, deployment of these SSL keys and certificates is automated. This chapter describes efficient methods for conducting all of these tasks.
This chapter does not explain SSL in depth. The Red Hat Satellite SSL Maintenance Tool was designed to hide much of the complexity involved in setting up and maintaining the public-key infrastructure (PKI). For more information, see the relevant sections of the Red Hat Enterprise Linux Deployment Guide.
4.1. A Brief Introduction to SSL
Secure Sockets Layer (SSL) is a protocol that enables client-server applications to pass information securely. SSL uses a system of public and private key pairs to encrypt communication passed between clients and servers. Public certificates can be left accessible, while private keys must be secured. It's the mathematical relationship (a digital signature) between a private key and its paired public certificate that makes this system work. Through this relationship, a connection of trust is established.
SSL private keys and public certificates will be discussed throughout this document. Both can be referred to as keys, one public and one private. However, when discussing SSL, it is the convention to refer to the public half of an SSL key pair (or key set) as the SSL public certificate.
An organization's SSL infrastructure is generally made up of the following SSL keys and certificates:
- Certificate Authority (CA) SSL private key and public certificate: only one set per organization generally generated. The public certificate is digitally signed by its private key. The public certificate is distributed to every system.
- Web server SSL private key and public certificate: one set per application server. The public certificate is digitally signed by both its private key and the CA SSL private key. It is often referred to as a Web server's key set; this is because there is an intermediary SSL certificate request that is generated. The details of what this is used for are not important to this discussion. All three are deployed to a Red Hat Satellite Server.
The following is a scenario to help visualize the concept: An organization with one Red Hat Satellite Server and five Red Hat Proxy Servers will need to generate one CA SSL key pair and six Web server SSL key sets. A CA SSL public certificate is distributed to all systems and used by all clients to establish a connection to their respective upstream servers. Each server has its own SSL key set that is specifically tied to that server's host name and generated using its own SSL private key and the CA SSL private key in combination. This establishes a digitally verifiable association between the Web server's SSL public certificate and the CA SSL key pair and server's private key. The Web server's key set cannot be shared with other web servers.
The most critical portion of this system is the CA SSL key pair. From that private key and public certificate an administrator can regenerate any Web server's SSL key set. This CA SSL key pair must be secured. It is highly recommended that once the entire Red Hat Satellite infrastructure of servers is set up and running, archive the SSL build directory generated by this tool and/or the installers onto separate media, write down the CA password, and secure the media and password in a safe place.