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.

Dependency Updates

This codemod relies on an external dependency. We have automatically added this dependency to your project's pyproject.toml file.

This library holds security tools for protecting Python API calls.

There are a number of places where Python project dependencies can be expressed, including setup.py, pyproject.toml, setup.cfg, and requirements.txt files. If this change is incorrect, or if you are using another packaging system such as poetry, it may be necessary for you to manually add the dependency to the proper location in your project.

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

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Feedback | Community | Docs | Codemod ID: pixee:python/sandbox-process-creation

[pixeebot]

This library holds security tools for protecting Python API calls.

License: MIT ✅ Open Source ✅ More facts

[coderabbitai]

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[burnettk]

@pixeebot, this change is causing issues with mypy like:

analyzing "security": module is installed, but missing library stubs or py.typed
marker  [import-untyped]
    from security import safe_command
    ^
src/spiffworkflow_backend/services/git_service.py:15:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
src/spiffworkflow_backend/services/git_service.py: note: In member "run_shell_command" of class "GitService":
src/spiffworkflow_backend/services/git_service.py:195:13: error: Returning Any
from function declared to return "CompletedProcess[bytes] | bool" 
[no-any-return]
                return result.returncode == 0
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/spiffworkflow_backend/services/git_service.py:202:9: error: Returning Any
from function declared to return "CompletedProcess[bytes] | bool" 
[no-any-return]
            return result
            ^~~~~~~~~~~~~
Found 3 errors in 1 file (checked 277 source files)

does the python security package you wrote have type hints? it would be nice to not lose type hints with this change. thank you.

[drdavella]

@burnettk thank you very much for the feedback! The security package does include type annotations on main. I will create a new release so that it is available downstream.

[drdavella]

For example, you can see the type annotations here: https://github.com/pixee/python-security/blob/6256809dac1c45530e5eeef8b48032a2bbd6b7d6/src/security/safe_command/api.py#L126-L138

[burnettk]

@drdavella , thank you.

[burnettk]

@drdavella in security lib api.py, is the print(executable_path) inside of def check supposed to be there? we started getting "random" None's on stdout when upgrading from 1.2.1 to 1.3.0. it might be coming from another line of code, but that's the first print statement i noticed in the diff.

[drdavella]

Hi @burnettk, no that looks like a leftover from debugging/development. I'll fix it and release a bugfix.

[burnettk]

confirmed fixed in 1.3.1