GHSA-5qr3-c538-wm9j — half two of the bypass chain.
``_mount_plugin_api_routes`` imports each dashboard plugin's
manifest ``api`` field as a Python module via
``importlib.util.spec_from_file_location`` — arbitrary code
execution by design. Two primitives in the surrounding code
turned that "by design" RCE into a usable attack:
1. Absolute paths in the manifest swallow the plugin directory.
``Path('safe/dashboard') / '/tmp/evil.py'`` resolves to
``/tmp/evil.py``, so a single manifest line
``{"api": "/tmp/payload.py"}`` was enough to redirect the
importer at any Python file on disk.
2. ``..`` traversal in the manifest climbs out of the dashboard
directory. ``Path('plugins/safe/dashboard') /
'../../../tmp/evil.py'`` lands in ``/tmp/evil.py`` after
``resolve()`` — the static-asset handler
(``serve_plugin_asset``) already defends against this via
``is_relative_to``; the api-mount path didn't.
Fix at three layers so a regression in any one can't re-open the
advisory:
* New ``_safe_plugin_api_relpath`` validator runs at *discovery*
time and stores only sanitised relative paths on the plugin
entry's ``_api_file`` field. Absolute paths, ``..`` traversal,
empty / non-string values, and paths that ``resolve()`` outside
the plugin's ``dashboard/`` directory are rejected with a
warning naming the plugin. ``has_api`` follows the sanitised
value so the dashboard frontend doesn't render a fake "Backend
API" badge for plugins whose api was scrubbed.
* ``_mount_plugin_api_routes`` re-validates the resolved path
against the live filesystem just before the import — defence in
depth in case ``_dir`` is tampered with post-cache or a future
caller bypasses the discovery-time validator.
* Project plugins (``source == "project"``) are refused outright
for backend import. ``./.hermes/plugins/`` ships with the CWD,
so any threat model that includes "user opens a malicious repo"
treats it as attacker-controlled; project plugins can still
extend the UI via static JS/CSS but their Python ``api`` is no
longer auto-imported. Combined with the truthy env-gate fix
from the previous commit, the original advisory chain now
fails at two distinct choke points.
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