How to create self-signed SSL TLS X.509 certificates using BastionXP Certificate Manager

Ganesh Velrajan
7 min readSep 15, 2023
BastionXP Certificate Manager — Private CA For Zero Trust Security

In this article, we’ll discuss how to use BastionXP Private PKI/CA, a web API based PKI/CA, to create self-signed SSL X.509 certificates. These self-signed SSL X.509 certificates can be used by any HTTPS or TLS server and client applications for secure SSL/TLS connection over the internet. These certificates can be used to validate server and client identity — a key requirement for enforcing Zero Trust Security.

For example, the generated X.509 certificates can be used to configure any webserver (Apache, NGNIX, Wordpress), Database (MySQL, Postgresql DB), Workloads(Docker, Kubernetes Pods, Microservices, Service Mesh), IoT gateways, devices or even your own web app server(HTTPS) and web app client.

The client SSL/TLS X.509 certificate can be used to enforce mutual TLS (mTLS) authentication between client-server applications in organizations that require Zero Trust Security.

A Private PKI CA like BastionXP is a crucial security tool for any organization that wants to become complaint with industry security standards such as HIPAA, SOC, SOC2, ISO 270001 etc.

So, let’s get started with BastionXP Certificate Manager Setup.

Note: This is a simple quick-start guide to keep the introduction to BastionXP simple. For a production-grade enterprise security configuration, for example using OIDC based SSO login to generate SSL Certificates based on user identity, refer to the BastionXP Documentation.

Overview:

Following are the steps to generate SSL X.509 self-signed certificates:

  1. We will use the BastionXP Certificate Manager to create a Root CA certificate, an Intermediate CA certificate and their private keys.
  2. We will use the BastionXP client utility bsh to create X.509 server private key, server certificate signing request(CSR), client private key and client certificate signing request(CSR). The BastionXP client will send the CSR to the BastionXP CA server.
  3. BastionXP CA will use the intermediate CA key to sign the X.509 server certificate signing request and the X.509 client certificate signing request.
  4. Once the certificates are signed successfully, the BastionXP CA will send the self-signed X.509 server and client certificates to the bsh client. The client will store the certificate and the private key in the user’s home directory.
  5. We’ll use the generated Self-Signed Server Certificate in a HTTPS web server written in Go and verify the certificates.

BastionXP Certificate Manager — Quick Start Guide

Follow the steps below to download, install, configure and run BastionXP as SSL/TLS X.509 Certificate Manager.

Prerequisites

You need to have the following to install and run BastionXP Certificate Manager:

  • A Linux VM or server or WSL(Windows Subsystem For Linux).
  • TCP Port: 443

BastionXP PKI/CA VM Setup

Step 1.1 — Download and Install

Follow the instructions here to download and install BastionXP CA in a Linux machine or VM.

Step 1.2 — Configuration File

Create a directory named bastionxp under /etc in your system as shown below:

$ sudo mkdir -p /etc/bastionxp

Create a configuratin file named config.json in the /etc/bastionxp directory with the following contents.

{ 
"mode": "auth",
"gateway_domain": "localhost",
"email": "bob@example.com"
}

Step 1.3 — Restart

Now restart the BastionXP service already running in the background, to pickup the above configuration changes.

$ sudo systemctl restart bastionxp

You can check the bastionxp logs as shown below:

$ tail -f /var/lib/bastionxp/bastionxp.log

You’ll see the following logs in the log file:

Using config file: /etc/bastionxp/config.json
Creating TLS Root CA certificate at: /var/lib/bastionxp/tls_root_ca.crt
Root CA Fingerprint: 35a85a609a703ab0984ba652ce0d3e0da1397aadc992b0139205f5c45dfd73a5
Creating TLS Intermediate CA certificate at: /var/lib/bastionxp/tls_intermediate_ca.crt
Creating Auth Server Host Certificate at: /var/lib/bastionxp/server.crt
...
...

To get a server certificate from the CA, we need to use the BastionXP client utility: bsh

Step 2.1 — Download BastionXP client

Follow the instructions here to download and install BastionXP Client bsh in your machine.

Step 2.2 — Establish Trust with the Certificate Manager

Before we can get SSL/TLS certificates from the CA, we need to make the bsh client trust the BastionXP CA.

This is required because the Certificate Manager is running locally on localhost and using a self-signed SSL/TLS certificate for the localhost domain name.

Use the fingerprint collected from the BastionXP CA setup logs above and make the client trust the CA.

$ bsh init --auth-server localhost --fingerprint 35a85a609a703ab0984ba652ce0d3e0da1397aadc992b0139205f5c45dfd73a5 
Downloading Root CA certificates... Please wait.
Successfully downloaded Root CA TLS certificates.

The above command will download the Root CA’s certificate named tls_root_ca.crt to a local folder named .bsh in your home directory: Eg: /home/bob/.bsh/tls_root_ca.crt

$ ls ~/.bsh tls_root_ca.crt

Now you can optionally add the BastionXP Root CA certificate to your system’s certificate trust store, as shown below for debian variants:

$ sudo cp ~/.bsh/tls_root_ca.crt /usr/local/share/ca-certificates/. 
$ sudo update-ca-certificates

Here after your system will start trusting all certificates issued by the BastionXP Certificate Manager.

Step 2.3 — Get the Server Cerfiticate

Now, we are ready to get a signed server certificate from the CA using the below command.

$ bsh login --auth-server localhost --no-auth --host localhost 

Downloaded long-lived SSH & TLS certificates for the host.

You can find the SSL/TLS server certificate and private key in the following location: /home/bob/.bsh

$ ls ~/.bsh 
...
tls_server.crt
tls_server.key
...

Get a Client Certificate

Step 3.1 — Download the Client Certificate

Again, use the bsh client to get a client certificate from the BastionXP CA.

$ bsh login --auth-server localhost --user bob --no-auth 
Downloading certificates... Please wait.
Successfully downloaded short-lived certificates.
Your roles are: []. Your access expires in 8 hours.

You’ll find the SSL/TLS client certificate and private key in the following location: /home/bob/.bsh

$ ls ~/.bsh 
...
tls_client.crt
tls_client.key
...

View the Issued Certificates:

We’ll use the OpenSSL tool to verify the certificates generated by the BastionXP CA so far.

Root CA Certificate:

$ openssl x509 -in ~/.bsh/tls_root_ca.crt -noout  -text
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
5f:b4:2a:23:83:bc:11:ba:2b:85:f0:a6:47:76:15:9c
Signature Algorithm: sha256WithRSAEncryption
Issuer: CN = localhost
Validity
Not Before: Sep 11 05:37:11 2023 GMT
Not After : Aug 18 05:37:11 2123 GMT
Subject: CN = localhost
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (4096 bit)
Modulus:
00:ba:06:5b:eb:13:d6:f9:d2:bb:fb:c0:70:86:db:
0e:91:79:dd:89:dd:99:26:eb:e6:09:da:77:cc:fe:
07:b0:09:21:c2:c7:17:e4:ee:58:d7:ce:9f:96:57:
6d:e5:73:8f:e5:23:9e:11:a7:76:de:94:9e:2a:7a:
8e:1b:3 ...
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Key Usage: critical
Digital Signature, Key Encipherment, Certificate Sign
X509v3 Basic Constraints: critical
CA:TRUE
X509v3 Subject Key Identifier:
78:2A:6C:A0:64:AA:59:42:2B:FA:11:25:66:3A:BE:5F:27:EA:6E:17
X509v3 Subject Alternative Name:
DNS:localhost
Signature Algorithm: sha256WithRSAEncryption
Signature Value:
72:3e:3f:8d:b2:72:68:e8:ef:88:b9:0d:d3:db:b0:22:a2:0c:
7c:93:6b:f6:bf:73:cc:93:62:e5:75:a1:ee:ae:a0:a2:c1:1f:
16:e4:79:0a:f3:a9:48: ...

Server Certificate:

$ openssl x509 -in ~/.bsh/tls_server.crt -noout  -text
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
8b:a6:d8:6f:1c:d0:a4:d9:fa:f4:9c:4c:14:41:1f:14
Signature Algorithm: sha256WithRSAEncryption
Issuer: CN = localhost
Validity
Not Before: Sep 11 06:14:29 2023 GMT
Not After : Aug 31 06:14:29 2025 GMT
Subject: CN = localhost
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (4096 bit)
Modulus:
00:db:b9:a4:72:1d:c0:86:52:0a:c1:80:a7:a8:0a:
06:2d:62:d4:94:4d:82:bb:0d:99:d9:b9:14:06:ee:
d2:22:51:45:fe:dc:9b ...
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Key Usage: critical
Digital Signature, Key Encipherment
X509v3 Extended Key Usage:
TLS Web Server Authentication, TLS Web Client Authentication
X509v3 Subject Alternative Name:
DNS:localhost
Signature Algorithm: sha256WithRSAEncryption
Signature Value:
4a:30:7b:01:65:e0:5f:06:e2:f0:12:2e:46:c6:13:92:c9:be:
a2:e9:dd:45:1d:e3:62:f4:61:90:f6:81:8a:ba:79:30:02:12:
37:15:d5:a1:7e:d5:a5:07:6a:2a ...

Client Certificate:

$ openssl x509 -in ~/.bsh/tls_client.crt -noout  -text
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
2d:11:ed:0e:e3:47:05:9a:14:05:5a:26:6b:7b:80:83
Signature Algorithm: sha256WithRSAEncryption
Issuer: CN = localhost
Validity
Not Before: Sep 11 06:13:08 2023 GMT
Not After : Sep 11 14:13:08 2023 GMT
Subject: CN = bob
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (4096 bit)
Modulus:
00:e7:d5:cd:79:ba:52:d4:87:9a:0d:8e:30:f4:b2:
3d:6d:8e:1d:d9:91:8c:30:ef:94:b8:da:87:2d:f2:
96:59:34:c4:c4:ac:63 ...
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Key Usage: critical
Digital Signature, Key Encipherment
X509v3 Extended Key Usage:
TLS Web Client Authentication
X509v3 Authority Key Identifier:
78:2A:6C:A0:64:AA:59:42:2B:FA:11:25:66:3A:BE:5F:27:EA:6E:17
X509v3 Subject Alternative Name:
email:bob
Signature Algorithm: sha256WithRSAEncryption
Signature Value:
b1:08:8f:90:7f:06:64:89:83:02:49:d0:14:35:45:cb:09:e0:
b7:61:c8:fd:bc:4f:54:6f:1b:1a:d6:4c:a9:ec:d7:56:26:6e:
0f:c6:0d:cc:2c:39:77:78:1d ...

Golang based TLS Server Example

We’ll use the below hello world HTTPS web server written in Golang to test the server certificate issued by the BastionXP CA.

package main 

import (
"net/http"
"log"
)

var (
CertFilePath = "/home/bob/.bsh/tls_server.crt"
KeyFilePath = "/home/bob/.bsh/tls_server.key"
)

func helloHandler(w http.ResponseWriter, req *http.Request)
{
w.Write([]byte("Hello, world!\n"))
}

func main() {
http.HandleFunc("/hello", helloHandler)
err := http.ListenAndServeTLS(":8443", CertFilePath, KeyFilePath, nil)
if err != nil {
log.Fatal(err)
}
}

Execute the above Go program using the following command:

$ go run https_server.go &

Now, try connecting to the above HTTPS server using the following command:

$ curl https://localhost:8443/hello

You’ll see the following error when you run the above command.

curl: (60) SSL certificate problem: unable to get local issuer certificate 
More details here: https://curl.se/docs/sslcerts.html curl failed to verify
the legitimacy of the server and therefore could not establish a secure
connection to it. To learn more about this situation and how to fix it,
please visit the web page mentioned above.

This is because the curl command line utility is not aware of the BastionXP Root CA and therefore doesn't trust the server certificate issued by the CA.

To make the curl utility trust the BastionXP CA and the certificates issued by it, use the --cacert flag in the curl command and provide the CA's root certificate as shown below:

$ curl --cacert ~/.bsh/tls_root_ca.crt https://localhost:8443/hello 

Hello, world!

Congratulations! You have successfully set up a private CA, generated a server certificate and used it for a HTTPS web service.

Next Steps

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Ganesh Velrajan

Ganesh Velrajan is the founder of Ampas Labs Inc. Learn more about our SSH Remote Access Solutions at https://www.socketxp.com and https://www.bastionxp.com