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fix(security): harden terminal safety and sandbox file writes (#1653)

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* fix(security): harden terminal safety and sandbox file writes

Two security improvements:

1. Dangerous command detection: expand shell -c pattern to catch
   combined flags (bash -lc, bash -ic, ksh -c) that were previously
   undetected. Pattern changed from matching only 'bash -c' to
   matching any shell invocation with -c anywhere in the flags.

2. File write sandboxing: add HERMES_WRITE_SAFE_ROOT env var that
   constrains all write_file/patch operations to a configured directory
   tree. Opt-in — when unset, behavior is unchanged. Useful for
   gateway/messaging deployments that should only touch a workspace.

Based on PR #1085 by ismoilh.

* fix: correct "POSIDEON" typo to "POSEIDON" in banner ASCII art

The poseidon skin's banner_logo had the E and I letters swapped,
spelling "POSIDEON-AGENT" instead of "POSEIDON-AGENT".

---------

Co-authored-by: ismoilh <ismoilh@users.noreply.github.com>
Co-authored-by: unmodeled-tyler <unmodeled.tyler@proton.me>
This commit is contained in:
Teknium 2026-03-17 02:22:12 -07:00 • committed by GitHub
parent 6a320e8bfe
commit 2c7c30be69
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6 changed files with 137 additions and 7 deletions
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26
tools/file_operations.py
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@ -75,14 +75,40 @@ WRITE_DENIED_PREFIXES = [
]
def _get_safe_write_root() -> Optional[str]:
"""Return the resolved HERMES_WRITE_SAFE_ROOT path, or None if unset.
When set, all write_file/patch operations are constrained to this
directory tree. Writes outside it are denied even if the target is
not on the static deny list. Opt-in hardening for gateway/messaging
deployments that should only touch a workspace checkout.
"""
root = os.getenv("HERMES_WRITE_SAFE_ROOT", "")
if not root:
return None
try:
return os.path.realpath(os.path.expanduser(root))
except Exception:
return None
def _is_write_denied(path: str) -> bool:
"""Return True if path is on the write deny list."""
resolved = os.path.realpath(os.path.expanduser(path))
# 1) Static deny list
if resolved in WRITE_DENIED_PATHS:
return True
for prefix in WRITE_DENIED_PREFIXES:
if resolved.startswith(prefix):
return True
# 2) Optional safe-root sandbox
safe_root = _get_safe_write_root()
if safe_root:
if not (resolved == safe_root or resolved.startswith(safe_root + os.sep)):
return True
return False