get_password_hash() computes PBKDF2-SHA256 with 600k iterations to
hash the HERMES_WEBUI_PASSWORD env var. This is called on nearly every
HTTP request via check_auth -> is_auth_enabled -> get_password_hash.
Before: ~1s of PBKDF2 per request, regardless of how many times the
same env-var value has already been hashed. A page load hitting 5+
API endpoints would burn 5+ seconds purely on password hashing.
After: compute once on first call, cache the hex result in a module-
level variable. Subsequent calls are a single global-variable read
(~50ns). The env var is immutable for the process lifetime, so there
is nothing to invalidate.
Thread-safe: double-checked locking ensures that under a burst of
concurrent requests only one thread computes PBKDF2, while the fast
path (after initialisation) requires zero locks.
Security analysis: zero regression. The hash is derived from a static
env var and a static signing key — both already readable from process
memory. Caching does not introduce any new disclosure or replay
vector. PBKDF2 is still used for the initial computation and for
verify_password() on login.
AI: deepseek/deepseek-v4-flash
bc3f4e54a6