cert_rsa_server.info

Let’s break down the script cert_rsa_server.sh, which is designed for creating and managing RSA server certificates. This script facilitates setting up the necessary directories, renewing database serial numbers, generating RSA keys, creating Certificate Signing Requests (CSRs), issuing certificates, and preparing certificate chain bundles for applications like HAProxy. Additionally, it verifies the integrity and details of the generated keys, CSRs, and certificates.

Here’s a detailed explanation:

Script Metadata link

• Filename: cert_rsa_server.sh
• Author: GJS (homelab-alpha)
• Date: June 9, 2024
• Version: 1.0.1
• Description: This script automates the process of creating and managing RSA certificates for server authentication, including key generation, CSR creation, certificate issuance, verification, and preparation of certificate chain bundles.
• RAW Script: cert_rsa_server.sh

Detailed Explanation link

Functions link

1. print_cyan: This function prints text in cyan color to enhance readability in the terminal.

   print_cyan() {
     echo -e "\e[36m$1\e[0m" # \e[36m sets text color to cyan, \e[0m resets it
   }
   

   
   

2. generate_random_hex: This function generates a random hexadecimal value, which is useful for serial numbers and CRL numbers.

   generate_random_hex() {
     openssl rand -hex 16
   }
   

   
   

3. print_section_header: This function prints section headers in cyan to clearly separate different parts of the script.

   print_section_header() {
     echo ""
     echo ""
     echo -e "$(print_cyan "=== $1 === ")"
   }
   

Main Script Execution link

Prompt for Certificate Information link

The script prompts the user for the certificate name, FQDN, and IPv4 address.

read -r -p "$(print_cyan "Enter the name of the new certificate: ")" file_name
read -r -p "$(print_cyan "Enter the FQDN name of the new certificate: ")" fqdn
read -r -p "$(print_cyan "Enter the IPv4 address of the new certificate (syntax: , IP:192.168.x.x): ")" ipv4

Define Directory Paths link

It defines the directory paths for storing SSL files and certificates.

print_section_header "Define directory paths"
ssl_dir="$HOME/ssl"
certificates_dir="$ssl_dir/certificates"
intermediate_dir="$ssl_dir/intermediate"

Renew Database Serial Numbers link

The script renews database serial numbers by generating random hex values and writing them to the respective serial files for the root, intermediate, and TSA directories.

print_section_header "Renew db serial numbers"
for dir in "$ssl_dir/root/db" "$intermediate_dir/db" "$ssl_dir/tsa/db"; do
  generate_random_hex >"$dir/serial"
done
generate_random_hex >"$ssl_dir/root/db/crlnumber"
generate_random_hex >"$intermediate_dir/db/crlnumber"

Generate RSA Key link

It generates an RSA key and saves it in the private directory for the server certificate.

print_section_header "Generate RSA key"
openssl genrsa -out "$certificates_dir/private/${file_name}.pem"

Generate Certificate Signing Request (CSR) link

The script creates a CSR for the server certificate using the generated RSA key and a configuration file.

print_section_header "Generate Certificate Signing Request (CSR)"
openssl req -new -sha256 -config "$certificates_dir/cert.cnf" -key "$certificates_dir/private/${file_name}.pem" -out "$certificates_dir/csr/${file_name}.pem"

Create an Extfile with All the Alternative Names link

It creates an extfile with parameters for the server certificate, such as subject alternative names (SANs), key usage, and extended key usage.

print_section_header "Create an extfile with all the alternative names"
{
  echo "subjectAltName = DNS:${fqdn}, DNS:www.${fqdn}${ipv4}"
  echo "basicConstraints = critical, CA:FALSE"
  echo "keyUsage = critical, digitalSignature"
  echo "extendedKeyUsage = serverAuth"
  echo "nsCertType = server"
  echo "nsComment = OpenSSL Generated Server Certificate"
} >>"$certificates_dir/extfile/${file_name}.cnf"

Generate Certificate link

The script issues the server certificate based on the CSR and extfile, valid for a specified period.

print_section_header "Generate Certificate"
openssl ca -config "$certificates_dir/cert.cnf" -notext -batch -in "$certificates_dir/csr/${file_name}.pem" -out "$certificates_dir/certs/${file_name}.pem" -extfile "$certificates_dir/extfile/${file_name}.cnf"

Create Certificate Chain Bundle link

It creates a certificate chain bundle by concatenating the server certificate and the intermediate CA chain bundle.

print_section_header "Create Certificate Chain Bundle"
cat "$certificates_dir/certs/${file_name}.pem" "$intermediate_dir/certs/ca_chain_bundle.pem" >"$certificates_dir/certs/${file_name}_chain_bundle.pem"

Create Certificate Chain Bundle for HAProxy link

The script creates a certificate chain bundle specifically for HAProxy by concatenating the chain bundle and the private key.

print_section_header "Create Certificate Chain Bundle for HAProxy"
cat "$certificates_dir/certs/${file_name}_chain_bundle.pem" "$certificates_dir/private/${file_name}.pem" >"$certificates_dir/certs/${file_name}_haproxy.pem"
chmod 600 "$certificates_dir/certs/${file_name}_haproxy.pem"

Verification Steps link

The script performs several verification steps to ensure the integrity and correctness of the certificates and keys.

1. Verify Certificate against the Certificate Chain Bundle

   print_section_header "Verify ${file_name} Certificate against the ${file_name} Certificate chain Bundle"
   openssl verify -CAfile "$certificates_dir/certs/${file_name}_chain_bundle.pem" "$certificates_dir/certs/${file_name}.pem"
   

   
   

2. Verify Certificate against the Intermediate Certificate Authority Chain Bundle

   print_section_header "Verify ${file_name} Certificate against the Intermediate Certificate Authority Chain Bundle"
   openssl verify -CAfile "$intermediate_dir/certs/ca_chain_bundle.pem" "$certificates_dir/certs/${file_name}.pem"
   

   
   

3. Verify Certificate Chain Bundle against the Intermediate Certificate Authority Chain Bundle

   print_section_header "Verify ${file_name} Certificate Chain Bundle against the Intermediate Certificate Authority Chain Bundle"
   openssl verify -CAfile "$intermediate_dir/certs/ca_chain_bundle.pem" "$certificates_dir/certs/${file_name}_chain_bundle.pem"
   

   
   

4. Verify HAProxy Certificate Chain Bundle against the Intermediate Certificate Authority Chain Bundle

   print_section_header "Verify HAProxy Certificate Chain Bundle against the Intermediate Certificate Authority Chain Bundle"
   openssl verify -CAfile "$intermediate_dir/certs/ca_chain_bundle.pem" "$certificates_dir/certs/${file_name}_haproxy.pem"
   

Check Generated Files link

The script includes steps to check the private key, CSR, server certificate, and the chain bundle to verify their contents.

1. Check Private Key

   print_section_header "Check Private Key"
   openssl rsa -in "$certificates_dir/private/${file_name}.pem" -text -noout
   

   
   

2. Check CSR

   print_section_header "Check Certificate Signing Request (CSR)"
   openssl req -text -noout -verify -in "$certificates_dir/csr/${file_name}.pem"
   

   
   

3. Check Certificate

   print_section_header "Check Certificate Certificate"
   openssl x509 -in "$certificates_dir/certs/${file_name}.pem" -text -noout
   

   
   

4. Check Certificate Chain Bundle

   print_section_header "Check Certificate Chain Bundle"
   openssl x509 -in "$certificates_dir/certs/${file_name}_chain_bundle.pem" -text -noout
   

Convert Certificate to Different Formats link

The script converts the certificate from PEM to CRT and KEY formats for compatibility with various applications.

print_section_header "Convert Certificate from ${fqdn}.pem to"
cat "$certificates_dir/certs/${file_name}.pem" >"$certificates_dir/certs/${file_name}.crt"
cat "$certificates_dir/certs/${file_name}_chain_bundle.pem" >"$certificates_dir/certs/${file_name}_chain_bundle.crt"
cat "$certificates_dir/private/${file_name}.pem" >"$certificates_dir/private/${file_name}.key"
chmod 600 "$certificates_dir/private/${file_name}.key"
echo -e "$(print_cyan "--> ")""${fqdn}.crt"
echo -e "$(print_cyan "--> ")""${fqdn}_chain_bundle.crt"
echo -e "$(print_cyan "--> ")""${fqdn}.key"

Conclusion link

This script ensures that every step in generating and managing an RSA server certificate is performed correctly and securely, from key generation to certificate verification and format conversion.