Beyond Linux® From Scratch (systemd edition) - Version 8.0

Chapter 4. Security

Certificate Authority Certificates

Public Key Infrastructure (PKI) is a method to validate the authenticity of an otherwise unknown entity across untrusted networks. PKI works by establishing a chain of trust, rather than trusting each individual host or entity explicitly. In order for a certificate presented by a remote entity to be trusted, that certificate must present a complete chain of certificates that can be validated using the root certificate of a Certificate Authority (CA) that is trusted by the local machine.

Establishing trust with a CA involves validating things like company address, ownership, contact information, etc., and ensuring that the CA has followed best practices, such as undergoing periodic security audits by independent investigators and maintaining an always available certificate revocation list. This is well outside the scope of BLFS (as it is for most Linux distributions). The certificate store provided here is taken from the Mozilla Foundation, who have established very strict inclusion policies described here.

This package is known to build and work properly using an LFS-8.0 platform.

Introduction to Certificate Authorities

Package Information

Additional Downloads

Certificate Authority Certificates Dependencies

Required

OpenSSL-1.0.2k

Optional (runtime)

Java-1.8.0.121 or OpenJDK-1.8.0.121, and NSS-3.29

User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/cacerts

Installation of Certificate Authority Certificates

The make-ca.sh script will process the certificates included in the certdata.txt file for use in multiple certificate stores (if the associated applications are present on the system). Additionally, any local certificates stored in /etc/ssl/local will be imported to the certificate stores. Certificates in this directory should be stored as PEM encoded OpenSSL trusted certificates.

To create an OpenSSL trusted certificate from a regular PEM encoded file, provided by a CA not included in Mozilla's certificate distribution, you need to add trust arguments to the openssl command, and create a new certificate. There are three trust types that are recognised by the make-ca.sh script, SSL/TLS, S/Mime, and code signing. For example, to allow a certificate to be trusted for both SSL/TLS and S/Mime, but explicitly rejected for code signing, you could use the following commands to create a new trusted certificate that has those trust attributes: 

openssl x509 -in MyRootCA.pem -text -fingerprint -setalias "My Root CA 1"     \
        -addtrust serverAuth -addtrust emailProtection -addreject codeSigning \
        > MyRootCA-trusted.pem

If a trust argument is omitted, the certificate is neither trusted, nor rejected. Clients that use OpenSSL or NSS encountering this certificate will present a warning to the user. Clients using GnuTLS without p11-kit support are not aware of trusted certificates. To include this CA into the ca-bundle.crt (used for GnuTLS), it must have serverAuth trust.

To install the various certificate stores, first install the make-ca.sh script into the correct location. As the root user: 

install -vm755 make-ca.sh-20170119 /usr/sbin/make-ca.sh

As the root user, make sure that certdata.txt is in the current directory, and update the certificate stores with the following command: 

/usr/sbin/make-ca.sh

You should periodically download a copy of certdata.txt and run the make-ca.sh script (as the root user), or as part of a monthly cron job to ensure that you have the latest available version of the certificates.

[Note]

Note

If running the script a second time with the same version of certdata.txt, for instance, to add additional stores as the requisite software is installed, add the -f switch to the command line. If packaging, run make-ca.sh --help to see all available command line options.

The certdata.txt file provided by BLFS is obtained from the mozilla-release branch, and is modified to provide a simple dated revision. This will be the correct version for most systems. There are, however, several other variants of the file available for use that might be preferred for one reason or another, including the files shipped with Mozilla products in this book. RedHat and OpenSUSE, for instance, use the version included in NSS-3.29. Additional upstream downloads are available at the links below.

Contents

Installed Programs: make-ca.sh
Installed Libraries: None
Installed Directories: /etc/ssl/{certs,java,local} and /etc/pki/{nssdb,anchors}

Short Descriptions

make-ca.sh

is a shell script that adapts a current version of certdata.txt, and prepares it for use as the system certificate store.

Last updated on 2017-02-14 22:04:32 -0800