Sandbox Process Creation

[pixeebot]

This codemod sandboxes all instances of subprocess.run and subprocess.call to offer protection against attack.

Left unchecked, subprocess.run and subprocess.call can execute any arbitrary system command. If an attacker can control part of the strings used as program paths or arguments, they could execute arbitrary programs, install malware, and anything else they could do if they had a shell open on the application host.

Our change introduces a sandbox which protects the application:

  import subprocess
+ from security import safe_command
  ...
- subprocess.run("echo 'hi'", shell=True)
+ safe_command.run(subprocess.run, "echo 'hi'", shell=True)
  ...
- subprocess.call(["ls", "-l"])
+ safe_command.call(subprocess.call, ["ls", "-l"])

The default safe_command restrictions applied are the following:

• Prevent command chaining. Many exploits work by injecting command separators and causing the shell to interpret a second, malicious command. The safe_command functions attempt to parse the given command, and throw a SecurityException if multiple commands are present.
• Prevent arguments targeting sensitive files. There is little reason for custom code to target sensitive system files like /etc/passwd, so the sandbox prevents arguments that point to these files that may be targets for exfiltration.

There are more options for sandboxing if you are interested in locking down system commands even more.

💡 This codemod adds a dependency to your project. Currently we add the dependency to a file named `requirements.txt` if it exists in your project.

There are a number of other places where Python project dependencies can be expressed, including `setup.py`, `pyproject.toml`, and `setup.cfg`. We are working on adding support for these files, but for now you may need to update these files manually before accepting this change.

More reading

• https://github.com/pixee/python-security/blob/main/src/security/safe_command/api.py
• https://cheatsheetseries.owasp.org/cheatsheets/OS_Command_Injection_Defense_Cheat_Sheet.html

I have additional improvements ready for this repo! If you want to see them, leave the comment:

@pixeebot next

... and I will open a new PR right away!

Powered by: pixeebot (codemod ID: pixee:python/sandbox-process-creation)

[pixeebot]

This library holds security tools for protecting Python API calls.

License: MIT ✅ Open Source ✅ More facts

[pixeebot]

I'm confident in this change, and the CI checks pass, too!

If you see any reason not to merge this, or you have suggestions for improvements, please let me know!

[pixeebot]

Just a friendly ping to remind you about this change. If there are concerns about it, we'd love to hear about them!

[pixeebot]

This change may not be a priority right now, so I'll close it. If there was something I could have done better, please let me know!

You can also customize me to make sure I'm working with you in the way you want.