The browser orphan reaper reads a daemon PID from a `.pid` file in a
world-writable, predictably-named temp dir (`/tmp/agent-browser-h_*`) it
does not write itself, then tree-kills that PID via `_terminate_host_pid`
after only a liveness check. A same-user actor could plant a fake socket
dir whose `.pid` points at an arbitrary victim process, and OS PID reuse
after the real daemon exits could land the recorded PID on an unrelated
process — either way an arbitrary same-user process (and its whole tree)
gets SIGTERMed. Local DoS.
Add `_verify_reapable_browser_daemon()`, gated before the kill: via psutil
(a hard dep, fine cross-platform for the same-user processes the reaper can
signal) require both (1) identity — `agent-browser` in the process
name/cmdline — and (2) binding — the live process references *this* session's
socket dir in its cmdline or `AGENT_BROWSER_SOCKET_DIR`. The binding check is
the real spoof defense: a planted/recycled PID won't embed our exact socket
path. Fail-closed on any ambiguity (unreadable cmdline, no match), leaving the
process and its socket dir untouched for a later sweep.
Builds on @sgaofen's fix in #14394 (cmdline identity check); rewritten to use
psutil instead of `/proc`+`ps` (cross-platform, Windows-covered) and to add
the session-socket-dir binding check for recycled-PID / spoof resistance.
Co-authored-by: sgaofen <135070653+sgaofen@users.noreply.github.com>
teknium1
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