Vulnerable code sample

import sys
import os
import re
import importlib

def vulnerable_omni_complete_simulation(buffer_content, file_path):
    """
    This function simulates the vulnerable logic in python3complete.vim.
    It adds the buffer's directory to the path and then attempts to import
    modules found within the buffer's text to gather completion suggestions.
    """
    buffer_dir = os.path.dirname(file_path)

    # The core of the vulnerability: The current file's directory is
    # prepended to Python's path, giving it import priority.
    if buffer_dir not in sys.path:
        sys.path.insert(0, buffer_dir)

    # Simplified logic to find 'import' statements in the buffer.
    # The actual script's parsing is more complex.
    import_pattern = re.compile(r"^\s*(?:from|import)\s+([a-zA-Z0-9_]+)")

    for line in buffer_content.splitlines():
        match = import_pattern.match(line)
        if match:
            module_name = match.group(1)
            # The dangerous action: Importing the module to inspect it for
            # completions. If a malicious __init__.py exists in a sibling
            # directory, its code will be executed here.
            try:
                # In a real scenario, this would be followed by dir(module)
                # to get attributes for completion.
                importlib.import_module(module_name)
            except ImportError:
                # Ignore modules that can't be found.
                pass
            except Exception:
                # The malicious code could raise an exception.
                pass

    # Clean up the path for subsequent operations in a real script.
    if buffer_dir in sys.path:
        sys.path.remove(buffer_dir)

# Example usage demonstrating the vulnerability.
# In a real attack, these would be two separate files on disk.

# 1. The content of the file the user is editing in Vim, e.g., /tmp/project/main.py
hostile_buffer_content = """
import os
import sys
import malicious_package # User types this and triggers omni-completion

print("Hello, world!")
"""

# 2. The path to the file being edited.
current_file = "/tmp/project/main.py"

# 3. A malicious package is placed next to the file being edited.
#    Directory structure:
#    /tmp/project/
#    ├── main.py
#    └── malicious_package/
#        └── __init__.py   <-- This file contains the malicious code.

# To simulate this without creating actual files, we can use a mock.
# In a real attack, the `importlib.import_module` call below would
# trigger the execution of the actual malicious __init__.py file.

# This part is for demonstration only to show what would happen.
# print("Simulating the creation of a malicious package...")
# malicious_code_path = "/tmp/project/malicious_package"
# os.makedirs(malicious_code_path, exist_ok=True)
# with open(os.path.join(malicious_code_path, "__init__.py"), "w") as f:
#     f.write("import os\n")
#     f.write("print('!!! MALICIOUS CODE EXECUTED !!!')\n")
#     f.write("os.system('echo Malicious payload triggered > /tmp/pwned')\n")


# print(f"Running vulnerable completion logic on file: {current_file}")
# vulnerable_omni_complete_simulation(hostile_buffer_content, current_file)

# print("Simulation finished. Check for /tmp/pwned file.")