doc/security/openssl_selfsigned_certificate_chain.adoc

= OpenSSL Self-signed Certificate Chain

// Copyright 2023 Jake Winters
// SPDX-License-Identifier: CC-BY-4.0

Version: 0.0.5.14


This documentation contains the complete set of commands to create a new OpenSSL self-signed
certificate chain with V3 subjectAltName (SAN) extensions enabled.
Multiple SANs can be included in a certificate by adding each domain as a comma-delimited string.
Each key can be encrypted or unencrypted, with multiple encryption options; AES is recommended.
Optional verification can also be performed between multiple levels of certificates to ensure the
chain of trust is valid.


== Create Certificate Authority Key

`openssl genrsa -aes256 -out ca-key.pem 4096`

== Verify Certificate Authority Key

`openssl rsa -noout -text -in ca-key.pem`

== Create Certificate Authority Certificate

`openssl req -new -x509 -days 3653 -extensions v3_ca -key ca-key.pem -out ca-crt.pem`

== Convert Certificate to PEM Format

`openssl x509 -in ca-crt.pem -out ca-crt.pem -outform PEM`

== Verify Certificate Authority Certificate

`openssl x509 -noout -text -in ca-crt.pem`

== Create Intermediate Certificate Authority Key

`openssl genrsa -aes256 -out intermediate-key.pem 4096`

== Verify Intermediate Certificate Authority Key

`openssl rsa -noout -text -in intermediate-key.pem`

== Create Intermediate Certificate Signing Request

`openssl req -new -sha256 -key intermediate-key.pem -out intermediate-csr.pem`

== Create Intermediate Certificate Authority Certificate

`openssl ca -config intermediate.conf -extensions v3_intermediate_ca -days 1096 -notext -md sha256 -in intermediate-csr.pem -out intermediate-crt.pem`

== Verify Intermediate Certificate Authority Certificate

`openssl x509 -noout -text -in intermediate-crt.pem`

== Verify Chain of Trust (CA to Intermediate)

`openssl verify -CAfile ca-crt.pem intermediate-crt.pem`

== Create Server Key

`openssl genrsa -aes256 -out server-key.pem 2048`

== Verify Server Key

`openssl rsa -noout -text -in server-key.pem`

== Create Server Cerificate Signing Request

`openssl req -new -sha256 -subj "/C=/ST=/L=/O=/CN=" -addext "subjectAltName = DNS.1:" -key server-key.pem -out server-csr.pem`

== Create Server Certificate

`openssl x509 -sha256 -req  -days 365 -in server-csr.pem -CA intermediate-crt.pem -CAkey intermediate-key.pem -extensions SAN -extfile <(cat /etc/ssl/openssl.cnf <(printf "\n[SAN]\nsubjectAltName=DNS.1:")) -out server-crt.pem`

== Verify Server Certificate

`openssl x509 -noout -text -in server-crt.pem`

== Verify Chain of Trust (Intermediate to Server)

`openssl verify -CAfile intermediate-crt.pem server-crt.pem`