Pablo Guides

# Course #47: Introduction to certgraph$

## Installation and Configuration on Kali Linux

Before diving into the functionality and benefits of the `certgraph$` tool, it is crucial to ensure that you have it properly installed and configured on your Kali Linux system.

### Step 1: Update Your Kali Linux System

Before installing any new tools, it's a good practice to update your system to ensure all existing packages are up to date. Open your terminal and execute the following command:

"`bash
sudo apt update && sudo apt upgrade -y
"`

### Step 2: Installing certgraph$

`certgraph$` can be installed from the Kali Linux repositories. To install it, use the following command:

"`bash
sudo apt install certgraph
"`

Once the installation is complete, you can verify that certgraph$ is installed by checking its version:

"`bash
certgraph -V
"`

### Step 3: Configuration

While `certgraph$` does not require extensive configuration out of the box, there are some settings that you may want to customize based on your pentesting needs. Configuration files can usually be found in `/etc/certgraph/`.

1. **Edit the Configuration File**:
Open the configuration file with a text editor:

   sudo nano /etc/certgraph/certgraph.conf

 

Here, you can set options such as output formats, verbosity levels, or log file paths.

2. **Set Up API Keys**:
If the tool requires certain API keys to access online databases or services, make sure to input them in the relevant sections of the configuration file.

3. **Network Configuration**:
If you're running this tool in a specific network environment, ensure that your firewall settings are adjusted to allow traffic as necessary.

### Step 4: Testing Installation

After configuration, it’s a good idea to run a simple command to ensure that `certgraph$` is functioning correctly:

"`bash
certgraph –help
"`

This command should display the help information about the tool, confirming that the installation was successful.

—

## Step-by-Step Usage and Real-World Use Cases

Now that you have `certgraph$` installed, let's explore how to use it effectively in real-world penetration testing scenarios.

### Getting Started with certgraph$

`certgraph$` is a tool designed to analyze SSL/TLS certificates and their relationships. It is particularly useful for discovering vulnerabilities through certificate analysis, understanding certificate chains, and identifying misconfigurations.

### Basic Commands

#### 1. **Scanning a Single Domain**

To perform a basic scan of a single domain, you can use:

"`bash
certgraph -d example.com
"`

This command will retrieve the SSL certificate for the specified domain and provide information regarding the certificate chain, expiration dates, and issuing authorities.

#### 2. **Scanning Multiple Domains**

To scan multiple domains in a single execution, you can create a text file with the list of domains and use the `-f` option:

"`bash
certgraph -f domains.txt
"`

The `domains.txt` file should simply contain one domain per line.

### Advanced Usage

#### 3. **Exporting Results**

For documentation and reporting purposes, exporting the results of your scan can be invaluable. To export results to a JSON file, you can use:

"`bash
certgraph -d example.com -o output.json
"`

#### 4. **Check for Expired Certificates**

To quickly check for expired certificates across a set of domains, you can script the process by combining `certgraph$` with other command-line tools. Here’s a simple bash script that checks for expired certificates:

"`bash
#!/bin/bash
while IFS= read -r domain; do
cert_info=$(certgraph -d "$domain")
if echo "$cert_info" | grep -q "expired"; then
echo "$domain has an expired certificate."
fi
done < domains.txt ``` ### Real-World Use Cases #### Use Case 1: Vulnerability Assessment During a routine vulnerability assessment, you can use `certgraph$` to identify any expired or misconfigured certificates in your organization's web applications. This can help mitigate risks associated with SSL/TLS vulnerabilities. #### Use Case 2: Third-Party Vendor Analysis When onboarding a new vendor, you can assess their domain's certificates using `certgraph$`. This can provide insights into their security posture and whether they follow best practices for certificate management. #### Use Case 3: Compliance Auditing For organizations subject to regulatory compliance (e.g., PCI DSS, GDPR), conducting regular certificate audits with `certgraph$` can ensure that all certificates are valid and configured correctly, reducing the risk of non-compliance penalties. --- ## Detailed Technical Explanations ### How SSL/TLS Certificates Work Understanding the underlying technology of SSL/TLS certificates is essential for making the most out of `certgraph$`. Certificates are used to establish secure connections between clients and servers, confirming the identity of the server. 1. **Certificate Authority (CA)**: A trusted entity that issues digital certificates. The CA validates the identity of the entity requesting the certificate. 2. **Public and Private Keys**: Certificates contain a public key that is shared with clients, while the private key is kept secure by the server. This asymmetric encryption ensures secure data transmission. 3. **Certificate Chains**: Certificates can be chained together, where each certificate in the chain is signed by the next one. A complete chain is necessary for clients to trust the server certificate. ### Common Vulnerabilities in SSL/TLS - **Expired Certificates**: Certificates that have surpassed their validity period. - **Self-Signed Certificates**: Certificates that are not verified by a trusted CA, often leading to trust issues in client-server communications. - **Weak Encryption Algorithms**: Using outdated encryption methods can expose vulnerabilities. ### External Reference Links - [Let's Encrypt](https://letsencrypt.org/): A free, automated, and open certificate authority. - [SSL Labs](https://www.ssllabs.com/ssltest/): A tool for testing SSL/TLS configurations. - [OWASP SSL/TLS Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/SSL_TLS_Cheat_Sheet.html): A guide for implementing secure SSL/TLS configurations. ### Code Examples for WordPress If you manage a WordPress site, you may want to integrate certificate checks into your site maintenance routines. Below is an example code snippet that you can use in a custom plugin or your theme’s `functions.php` file: ```php function check_ssl_certificate($domain) { $command = "certgraph -d " . escapeshellarg($domain); $output = shell_exec($command); if (strpos($output, 'expired') !== false) { return "$domain has an expired SSL certificate!"; } return "$domain SSL certificate is valid."; } // Usage add_action('admin_notices', function() { $domains = ['example.com', 'anotherdomain.com']; foreach ($domains as $domain) { echo '

';
}
});
"`

This code checks the SSL certificate status of specified domains and displays a notice in the WordPress admin area.

—

## Conclusion

With `certgraph$`, penetration testers can enhance their toolkit significantly by gaining insights into SSL/TLS certificates and their configurations. It can help identify vulnerabilities, manage certificates effectively, and ensure compliance with security standards.

By integrating `certgraph$` into your pentesting methodology, you not only enhance your overall approach to security but also provide valuable recommendations for improving SSL/TLS practices within organizations.

—

Made by pablo rotem / פבלו רותם