session manager - prevent file path injection

[pgrayy]

Description

Fixing a vulnerability in the file and s3 session managers where customers can manipulate the storage paths through session id.

from strands.session.file_session_manager import FileSessionManager

FileSessionManager(session_id="../../private", storage_dir="./")

Currently, session_id is appended to the storage path without first being sanitized. Doing the above could lead the session manager to add or remove files from a restricted directory. This is a risk for Strands customers that obtain session_id from a third party.

This PR fixes the issue by raising an exception if the session_id contains separators.

Related Issues

Issue raised to the team internally.

Documentation PR

Updated the API docs through docstrings in this PR.

Type of Change

Bug fix

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare: Wrote new unit tests.

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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[zastrowm]

Some nits/organizational items