Adds an nginx-side rate limit on POST /login so a brute-force or DoS
attempt can't pin the box on the bcrypt-shaped credential check inside
rousette/PAM. Configuration:
- Keyed on $binary_remote_addr (per source IP), 5 requests/minute
sustained with a burst of 3 nodelay, a real user fumbling their
password three times in a row sails through; the 4th attempt in
the same window returns 429.
- GET /login is unmetered (the keyed map yields the empty string,
which limit_req treats as "no key, no limit"), so a 401-driven
HX-Redirect bouncing the user back to the login page doesn't
eat into the budget.
- 32k zone (~500 IPs, the minimum nginx accepts). At cache
saturation an attacker rotating addresses still tops out around
~2500 attempts/min, all serialised through bcrypt one at a time.
- 429 instead of the default 503 keeps the response out of the
/50x.html error_page rewrite (which auto-refreshes and would
loop a throttled client straight back to /login).
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
Joachim Wiberg
beabc1fe5b