Prevent artifact storage path escapes from reserved dataset names

[fallintoplace]

Summary

• reject . and .. for artifact directory names
• resolve artifact subpaths against the artifact root and fail if they escape it
• add storage and interface regression coverage for reserved dataset names

Why

ArtifactStorage previously joined artifact_path and dataset_name directly. In resume flows, dataset_name=".." could resolve outside the artifact root, and dataset_name="." could collapse the dataset directory onto the artifact root.

Testing

• uv run --package data-designer-engine pytest packages/data-designer-engine/tests/engine/storage/test_artifact_storage.py
• uv run --package data-designer pytest packages/data-designer/tests/interface/test_data_designer.py -k reserved_dataset_name
• uv run ruff check packages/data-designer-engine/src/data_designer/engine/storage/artifact_storage.py packages/data-designer-engine/tests/engine/storage/test_artifact_storage.py packages/data-designer/tests/interface/test_data_designer.py
• uv run ruff format --check packages/data-designer-engine/src/data_designer/engine/storage/artifact_storage.py packages/data-designer-engine/tests/engine/storage/test_artifact_storage.py packages/data-designer/tests/interface/test_data_designer.py

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[greptile-apps]

Greptile Summary

This PR closes a path-traversal hole in ArtifactStorage where passing dataset_name=".." in a resume flow could cause the engine to read or write outside the designated artifact root. The fix adds two complementary defenses: an explicit reject of "." and ".." in the model validator, and a _resolve_artifact_subpath helper that uses Path.resolve() plus relative_to() as a belt-and-suspenders check on every derived storage path.

• Validation guard — validate_folder_names now rejects "." and ".." for all five configurable folder name fields before any path construction occurs.
• Runtime path guard — _resolve_artifact_subpath resolves the candidate path against resolved_artifact_path (a new cached property) and raises ArtifactStorageError if the result escapes the artifact root, protecting against any future bypass of the validator.
• Test coverage — new parametrized unit tests cover all five fields for both reserved names, a cache-injection test exercises the runtime guard independently, and an integration test confirms DataDesigner.create() surfaces the error end-to-end.

Confidence Score: 5/5

The change adds purely additive validation with no modifications to existing logic paths; all new error paths raise immediately without side effects.

Both the validator-level and runtime-level guards are correct, the Path.resolve() + relative_to() pattern is the standard way to prevent directory traversal in Python, and the test suite covers the direct validation path, the cache-injection bypass scenario, and the full integration path through DataDesigner.create().

No files require special attention.

Important Files Changed

Filename	Overview
packages/data-designer-engine/src/data_designer/engine/storage/artifact_storage.py	Adds path-traversal defenses: a '.' / '..' reject in the model validator, a new resolved_artifact_path cached_property, and a _resolve_artifact_subpath helper that uses Path.resolve() + relative_to() as a belt-and-suspenders check on every derived path.
packages/data-designer-engine/tests/engine/storage/test_artifact_storage.py	Adds parametrized coverage for all five folder-name fields rejecting '.' and '..', plus a test that directly injects '..' into the resolved_dataset_name cache to verify the belt-and-suspenders check in _resolve_artifact_subpath.
packages/data-designer/tests/interface/test_data_designer.py	Adds an integration-level regression test verifying that DataDesigner.create() propagates the ArtifactStorageError when dataset_name='..' is passed.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["ArtifactStorage init"] --> B["validate_artifact_path\nmust be existing dir"]
    B --> C["validate_folder_names"]
    C --> D["Check each folder name"]
    D -->|"empty"| E["ArtifactStorageError"]
    D -->|"duplicate"| F["ArtifactStorageError"]
    D -->|"invalid chars"| G["ArtifactStorageError"]
    D -->|"dot or dotdot"| H["ArtifactStorageError"]
    D -->|"passes"| I["Init MediaStorage via base_dataset_path"]
    I --> J["_resolve_artifact_subpath"]
    J --> K["resolved_artifact_path.joinpath parts .resolve"]
    K --> L{"relative_to check"}
    L -->|"fails"| M["ArtifactStorageError escapes root"]
    L -->|"passes"| N["Return resolved Path"]
    N --> O["ArtifactStorage ready"]

Loading

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flowchart TD
    A["ArtifactStorage init"] --> B["validate_artifact_path\nmust be existing dir"]
    B --> C["validate_folder_names"]
    C --> D["Check each folder name"]
    D -->|"empty"| E["ArtifactStorageError"]
    D -->|"duplicate"| F["ArtifactStorageError"]
    D -->|"invalid chars"| G["ArtifactStorageError"]
    D -->|"dot or dotdot"| H["ArtifactStorageError"]
    D -->|"passes"| I["Init MediaStorage via base_dataset_path"]
    I --> J["_resolve_artifact_subpath"]
    J --> K["resolved_artifact_path.joinpath parts .resolve"]
    K --> L{"relative_to check"}
    L -->|"fails"| M["ArtifactStorageError escapes root"]
    L -->|"passes"| N["Return resolved Path"]
    N --> O["ArtifactStorage ready"]

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[fallintoplace]

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