injection fix using shell=false

[ayushhgarg-work]

Description

What

Fix command injection vulnerability (CWE-94) in commandline_utility.py by removing
unsafe shell=True + string-join pattern.

Related: MSRC Case 106104 (Moderate - Remote Code Execution)

Why

The run_cli_command function previously joined command arguments into a single string
via " ".join(cmd_arguments) and executed it with subprocess.check_output(..., shell=True).
This allowed shell metacharacters in user-controlled input (e.g., scoring_script path
in a deployment YAML) to break out of the command and execute arbitrary code.

Changes

• Set shell=False and pass cmd_arguments as a list directly to
  subprocess.check_output on all platforms — shell metacharacters are never interpreted
• Removed the " ".join(cmd_arguments) pattern and the outdated comment
  referencing the old shell=True approach
• Added unit tests for run_cli_command covering:
  • Correct subprocess argument forwarding (shell, stderr, env)
  • Shell metacharacter injection prevention (;, & payloads matching MSRC attack vectors)
  • CalledProcessError propagation

Fix in local_endpoint_helper.py

OnlineEndpoints.list(local=True) crashed with json.JSONDecodeError when an endpoint cache file under ~/.azureml/inferencing was empty or partially written.
Guard the read loop in EndpointStub-backed list() to skip empty, partially-written, or unreadable cache files instead of raising.

Testing

• Verified on Windows that malicious arguments containing &, ;, | are passed as
  literal strings and do not result in command injection
• All 7 unit tests pass on Windows

[Copilot]

Pull request overview

This PR updates the local endpoints CLI invocation helper to mitigate command injection by avoiding shell=True + string-joined commands on non-Windows platforms, and introduces Windows-specific handling for commands that are provided as .cmd/.bat shims.

Changes:

• Switch non-Windows execution to shell=False with argv list.
• Add Windows branch that builds a command line string via subprocess.list2cmdline(...) and executes with shell=True.
• Minor refactor/formatting around command printing and subprocess args construction.

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[ayushhgarg-work]

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[ayushhgarg-work]

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