[azure-ai-ml] Fix path traversal vulnerability in storage download helpers

[ayushhgarg-work]

Summary

Fixes a path traversal vulnerability (CWE-22) in the download methods of all three storage helpers that could allow server-supplied blob/file names containing .. segments to write files outside the intended destination directory.

Changes

Added path validation in the download flows to ensure resolved target paths remain within the caller-specified destination directory. Malicious paths are skipped with a warning log.

Affected files:

• azure/ai/ml/_artifacts/_blob_storage_helper.py — BlobStorageClient.download()
• azure/ai/ml/_artifacts/_gen2_storage_helper.py — Gen2StorageClient.download()
• azure/ai/ml/_artifacts/_fileshare_storage_helper.py — recursive_download()

Details

The download methods construct local file paths from server-returned blob/file names without verifying the resolved path stays under the destination. A name like ../../etc/malicious would escape the download directory.

The fix resolves both the destination and target to absolute paths, then uses Path.relative_to() to confirm the target is a descendant of the destination. Items that fail this check are skipped and a warning is logged.

[Copilot]

Pull request overview

This PR addresses a CWE-22 path traversal risk in the artifact storage download helpers by validating that server-supplied blob/file paths resolve under the caller-provided destination directory before writing to disk.

Changes:

• Add resolved-path containment checks (via Path.resolve() + Path.relative_to()) to block .. traversal and other escaping paths during downloads.
• Skip suspicious items and emit a warning log instead of writing outside the destination directory.
• Apply the same protection pattern across Blob, ADLS Gen2, and Fileshare download implementations.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
sdk/ml/azure-ai-ml/azure/ai/ml/_artifacts/_blob_storage_helper.py	Adds destination/target resolution and containment checks before writing downloaded blobs.
sdk/ml/azure-ai-ml/azure/ai/ml/_artifacts/_gen2_storage_helper.py	Adds equivalent containment validation for ADLS Gen2 get_paths() results prior to directory creation or file writes.
sdk/ml/azure-ai-ml/azure/ai/ml/_artifacts/_fileshare_storage_helper.py	Adds containment validation for both file and subdirectory downloads in the recursive fileshare helper.