To ensure system-wide trust for the self-signed certificate I use on my intranet server, I added an exception for it in Firefox, but this is not possible in other applications such as Chrome, console apps, and IDEs.
Therefore, I want the certificate to be trusted system-wide, and the recommended approach seems to be installing it as a root CA.
However, I’m concerned that whoever controls the self-signed certificate could potentially use it to sign forged certificates for any site on my machine, which is not what I want. I only need the single intranet server to be self-signed, not all services I use.
What is the recommended approach for dealing with intranet TLS in this situation?
2 Answers
Introduction
Intranet servers are used by organizations to serve content within their internal network. These servers use self-signed certificates to secure the communication between the server and the clients. However, these certificates are not trusted by default by the clients, which can lead to security warnings and errors. In this post, we will discuss the self-signed certificate system-wide without installing as root CA and the recommended way to deal with intranet TLS.
What is a self-signed certificate?
A self-signed certificate is a digital certificate that is signed by the same entity whose identity it certifies. In other words, the certificate is not issued by a trusted third-party certificate authority (CA) but is created and signed by the server itself. Self-signed certificates are used to secure communication between the server and the client and are commonly used on intranet servers.
The recommended way to deal with intranet TLS
The recommended way to deal with intranet TLS is to use a private CA. A private CA is a certificate authority that is owned and operated by the organization that uses it to issue digital certificates for its internal servers and services. Private CAs are used to establish trust within an organization and are not trusted by external clients.
To set up a private CA, the organization needs to create a root certificate and install it on all the clients within the organization. The root certificate is used to sign the digital certificates issued by the private CA. The private CA can issue digital certificates for all the internal servers and services, and these certificates will be trusted by all the clients within the organization.
Self-signed certificate system-wide without installing as root CA
It is possible to trust a self-signed certificate system-wide without installing it as a root CA. However, this approach is not recommended as it can lead to security vulnerabilities.
When a self-signed certificate is installed as a root CA, it can sign certificates for any site on the machine, including external sites. This means that whoever controls the self-signed certificate can create forged certificates for any site, which can lead to a man-in-the-middle attack.
To trust a self-signed certificate system-wide without installing it as a root CA, the certificate needs to be added to the trusted certificate store on each client. This can be done manually, but it is not practical for organizations with a large number of clients.
How can I prevent security vulnerabilities?
To prevent security vulnerabilities, it is recommended to use a private CA to issue digital certificates for internal servers and services. This approach ensures that the certificates are trusted by all the clients within the organization and prevents the self-signed certificate from being used to sign forged certificates for external sites.
If a self-signed certificate needs to be trusted system-wide, it should be added to the trusted certificate store on each client manually. However, this approach should only be used as a last resort and should be avoided if possible.
Conclusion
Intranet servers use self-signed certificates to secure communication between the server and the clients. To establish trust within an organization, it is recommended to use a private CA to issue digital certificates for internal servers and services. Self-signed certificates can be trusted system-wide by adding them to the trusted certificate store on each client manually, but this approach should only be used as a last resort and should be avoided if possible. By following these recommendations, organizations can ensure that their internal communication is secure and trusted by all the clients.
If you have control over the server, the recommended approach is to create an actual root CA using a tool such as easy-rsa, Xca or the Windows Server CA role.
Next, replace the self-signed server certificate with one that is issued by your custom CA, ensuring that the certificate is marked as a “leaf” or “end-entity” certificate, with the “X.509v3 Basic Constraints” extension present and set to “CA: FALSE”.
Then, install the custom CA’s root certificate into your computer and securely store the CA private key so that it’s only accessible when issuing a new certificate.
By separating the CA from the server, you avoid potential issues with the system ignoring Basic Constraints when directly installing the server’s self-signed certificate into the “Trusted CA” folder.
Additionally, this approach simplifies the process of updating or changing the server certificate in the future, as you can simply use the same root CA to issue a new certificate without needing to re-trust the server certificate.