Replace unsafe pyyaml loader with SafeLoader

[pixee-b1171e79b0e16eb5]

The default loaders in PyYAML are not safe to use with untrusted data. They potentially make your application vulnerable to arbitrary code execution attacks. If you open a YAML file from an untrusted source, and the file is loaded with the default loader, an attacker could execute arbitrary code on your machine.

This codemod hardens all yaml.load() calls against such attacks by replacing the default loader with yaml.SafeLoader. This is the recommended loader for loading untrusted data. For most use cases it functions as a drop-in replacement for the default loader.

Calling yaml.load() without an explicit loader argument is equivalent to calling it with Loader=yaml.Loader, which is unsafe. This usage [has been deprecated](https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load(input\)-Deprecation) since PyYAML 5.1. This codemod will add an explicit SafeLoader argument to all yaml.load() calls that don't use an explicit loader.

The changes from this codemod look like the following:

  import yaml
  data = b'!!python/object/apply:subprocess.Popen \\n- ls'
- deserialized_data = yaml.load(data, yaml.Loader)
+ deserialized_data = yaml.load(data, Loader=yaml.SafeLoader)

More reading

• https://owasp.org/www-community/vulnerabilities/Deserialization_of_untrusted_data
• https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load(input)-Deprecation

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!

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💬Feedback | 👥Community | 📚Docs | Codemod ID: pixee:python/harden-pyyaml

[pixee-b1171e79b0e16eb5]

I'm confident in this change, but I'm not a maintainer of this project. Do you see any reason not to merge it?

If this change was not helpful, or you have suggestions for improvements, please let me know!

[pixee-b1171e79b0e16eb5]

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

[pixee-b1171e79b0e16eb5]

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.