Pablo Guides

# Course #257: Hotpatch – A Deep Dive

## Section 1: Introduction to Hotpatch

Hotpatch is a powerful tool included in Kali Linux that allows penetration testers to apply patches to running processes without needing to restart them. This can be incredibly useful for maintaining service availability while performing security testing, making it a critical skill for any white-hat hacker or cybersecurity professional. This section will provide an in-depth examination of the installation, configuration, and practical usage of Hotpatch, along with real-world scenarios where this tool shines.

### Installation and Configuration on Kali Linux

To get started with Hotpatch, we first need to ensure that we have Kali Linux installed. Kali is a Debian-based distribution tailored for penetration testing and security auditing, and it comes pre-loaded with many tools, including Hotpatch.

#### Step 1: Update Your Kali Linux

Before installing any new tools, it’s always a good practice to update your system. Open your terminal and run the following commands:

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

#### Step 2: Installing Hotpatch

As of the latest updates in Kali Linux, Hotpatch may already be installed. You can verify its presence by running:

"`bash
which hotpatch
"`

If Hotpatch is not installed, you can install it via:

"`bash
sudo apt install hotpatch -y
"`

#### Step 3: Configuration

After installation, Hotpatch requires some configuration to tailor it to your specific needs. The configuration file is typically found in `/etc/hotpatch/hotpatch.conf`. Open this file in your preferred text editor:

"`bash
sudo nano /etc/hotpatch/hotpatch.conf
"`

In this configuration file, you can specify the directories where patched binaries are located, set logging levels, and more. A sample configuration might include:

"`conf
# Hotpatch Configuration

# Directory for patches
patch_dir=/usr/local/hotpatch/patches

# Log file
log_file=/var/log/hotpatch.log

# Logging level: 0 (error), 1 (warn), 2 (info), 3 (debug)
log_level=2
"`

Make sure to save and exit the editor (in Nano, press `CTRL + X`, then `Y`, and `Enter`).

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

Now that Hotpatch is installed and configured, let’s explore how to use it effectively. Below, we’ll go through some specific use cases, providing a detailed, technical explanation of the commands used.

#### Use Case 1: Patching a Running Service

In a real-world scenario, let’s consider that we have a vulnerable web application running on Apache, and we have developed a patch to address a security flaw. Follow these steps to apply the patch without downtime.

#### Step 1: Create a Patch

First, let’s create a simple patch file. We will assume that the vulnerable binary is located in `/usr/sbin/apache2`. Create a patch file named `apache2.patch` in the patches directory specified in your configuration:

"`bash
cd /usr/local/hotpatch/patches
echo "Modifying apache2 binary to fix a security issue" > apache2.patch
"`

#### Step 2: Apply the Patch

To apply the patch to the running Apache service, you would typically use the following command:

"`bash
sudo hotpatch /usr/sbin/apache2 /usr/local/hotpatch/patches/apache2.patch
"`

#### Step 3: Verify the Patch

After applying the patch, you can verify that it has been successfully applied by checking the logs:

"`bash
cat /var/log/hotpatch.log
"`

You should see entries confirming that the patch was applied.

#### Use Case 2: Patch a Custom Application

Imagine you developed a custom application that runs on port 8080, which has a minor vulnerability. You want to patch it while ensuring it continues to run for users.

Follow these steps:

1. **Locate the Binary**: Ensure you know where your compiled application binary is located.
2. **Create a Patch File**: Create your patch similarly as before:

"`bash
cd /usr/local/hotpatch/patches
echo "Fixing vulnerability in custom_app" > custom_app.patch
"`

3. **Use Hotpatch**:

"`bash
sudo hotpatch /path/to/your/custom_app /usr/local/hotpatch/patches/custom_app.patch
"`

4. **Monitor the Logs**:

"`bash
cat /var/log/hotpatch.log
"`

### Detailed Technical Explanations

The Hotpatch tool works by modifying the memory of a running process to replace the vulnerable parts with a patched version. This is typically done using a technique called "memory patching", which involves:

– **Finding the Process**: When you call Hotpatch, it locates the running process using its PID (Process ID).
– **Reading Memory**: It reads the memory sections of the target process.
– **Replacing Code**: The specified portions of memory are then modified to include the new patch.
– **Logging Changes**: All changes and actions are logged for audit and debugging purposes.

#### External Reference Links

For further reading and detailed documentation on Hotpatch, you can refer to the following links:

– [Kali Linux Tools – Hotpatch](https://www.kali.org/tools/hotpatch)
– [Hotpatch GitHub Repository](https://github.com/hotpatch/hotpatch)
– [Memory Patching Techniques](https://www.owasp.org/index.php/Memory_Manipulation)

### Code Examples in Markdown

Here are the code examples provided in markdown format for easy reference in WordPress or other markdown-compatible editors:

"`markdown
# Updating Kali Linux
"`bash
sudo apt update
sudo apt upgrade -y
"`

# Installing Hotpatch
"`bash
sudo apt install hotpatch -y
"`

# Configuration Example
"`conf
# Hotpatch Configuration
patch_dir=/usr/local/hotpatch/patches
log_file=/var/log/hotpatch.log
log_level=2
"`

# Creating and Applying a Patch
"`bash
cd /usr/local/hotpatch/patches
echo "Modifying apache2 binary to fix a security issue" > apache2.patch
sudo hotpatch /usr/sbin/apache2 /usr/local/hotpatch/patches/apache2.patch
"`

# Verifying the Patch
"`bash
cat /var/log/hotpatch.log
"`

This section provides a foundational understanding of Hotpatch, setting you up for more advanced applications in the following sections of this course.

—

Made by pablo rotem / פבלו רותם