fix: Restrict upload of binary or unknown file types by default

[fsbraun]

Description

This PR changes the default settings for file validations to deny upload of binary or unknown file types. Uploading unknown file types is a security risk which will have to be enabled first by setting:

FILER_REMOVE_FILE_VALIDATORS = [
    "application/octet-stream",
]

The docs now include an example of how to run binary file uploads by a virus checker (ClamAV in the example)

# settings.py
FILER_ADD_FILE_VALIDATORS = {
    "application/octet-stream": ["my_validator_app.validators.validate_octet_stream"],
}

# my_validator_app.validators.py

def validate_octet_stream(file_name: str, file: typing.IO, owner: User, mime_type: str) -> None:
    """Octet streams are binary files without a specific mime type. They are run through
    a virus check."""
    try:
        from django_clamd.validators import validate_file_infection

        validate_file_infection(file)
    except (ModuleNotFoundError, ImportError):
        raise FileValidationError(
            _('File "{file_name}": Virus check for binary/unknown file not available').format(file_name=file_name)
        )

It bumps the version to 3.3 since it will require an explicit update of settings for some use cases.

Related resources

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Checklist

• I have opened this pull request against master
• I have added or modified the tests when changing logic
• I have followed the conventional commits guidelines to add meaningful information into the changelog
• I have read the contribution guidelines and I have joined #workgroup-pr-review on
  Slack to find a “pr review buddy” who is going to review my pull request.

[sourcery-ai]

Reviewer's Guide by Sourcery

This PR implements security improvements by restricting the upload of binary and unknown file types by default. The implementation adds a default validator for 'application/octet-stream' MIME type in the FILE_VALIDATORS settings and provides a way to customize validation through configuration settings.

Class diagram for file validation changes

classDiagram
    class FilerConfig {
        +FILE_VALIDATORS: dict
    }

    class ValidationSettings {
        +FILER_REMOVE_FILE_VALIDATORS: list
        +FILER_ADD_FILE_VALIDATORS: dict
    }

    FilerConfig --> ValidationSettings

    note for FilerConfig "FILE_VALIDATORS now includes 'application/octet-stream' with a default deny validator."
    note for ValidationSettings "Settings can be customized to add or remove file validators."

Loading

File-Level Changes

Change	Details	Files
Added default security restriction for binary/unknown file uploads	Added 'application/octet-stream' to FILE_VALIDATORS with deny validator Added configuration option FILER_REMOVE_FILE_VALIDATORS to override restrictions Added documentation for custom binary file validation with virus checking example	filer/settings.py docs/validation.rst
Updated test cases to handle new file upload restrictions	Modified binary upload test to temporarily disable validators Added validator state management in test setup and teardown Preserved original validator configuration after test execution	tests/test_admin.py

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[sourcery-ai]

Hey @fsbraun - I've reviewed your changes - here's some feedback:

Overall Comments:

• Consider adding a migration guide section to the documentation to help users transition from the previous behavior, especially for cases where they need to explicitly enable binary file uploads.

Here's what I looked at during the review

• 🟡 General issues: 1 issue found
• 🟢 Security: all looks good
• 🟡 Testing: 2 issues found
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.73%. Comparing base (b0f39ab) to head (031c1be).
Report is 27 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1507      +/-   ##
==========================================
+ Coverage   76.59%   76.73%   +0.14%     
==========================================
  Files          75       77       +2     
  Lines        3546     3624      +78     
  Branches      568      519      -49     
==========================================
+ Hits         2716     2781      +65     
- Misses        667      677      +10     
- Partials      163      166       +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

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[fsbraun]

@sourcery-ai review

[sourcery-ai]

I'm sorry, I don't understand the command @sourcery-ai I added migration information to README.rst.

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