BaseEnvironment writes shell snapshots and cwd metadata through the process
umask. With a common 022 umask, snapshot files containing exported environment
state landed at mode 0644 even though they can include env-carried credentials
from the parent process.
Set umask 077 only around Hermes metadata writes: the initial snapshot
bootstrap and the post-command snapshot/cwd refresh. User commands still run
under the caller's original umask, while Hermes-owned snapshot and cwd files
are created owner-only.
This intentionally does not copy the source PR's global orphan sweep; deleting
all matching /tmp snapshot files could interfere with concurrent Hermes
processes. The security-critical local disclosure fix is the file mode clamp.
This is salvageable because the source report still identifies a concrete
credential-disclosure path, but the safe subset is smaller than the original
proposal: clamp only the Hermes-owned snapshot writes and leave process-wide
cleanup, user command umask, and concurrent sessions alone.
Salvages source PR: https://github.com/NousResearch/hermes-agent/pull/20056
Related issue: https://github.com/NousResearch/hermes-agent/issues/48441
Co-authored-by: Andrew Homeyer <andrew@hndl.app>
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