security: rate limit admin authentication

apps/api/app/admin_security.py

@@ -0,0 +1,59 @@
+from datetime import datetime, timedelta, timezone
+import hashlib
+import hmac
+
+from fastapi import HTTPException, Request
+from sqlalchemy import delete, func, select, text
+from sqlalchemy.orm import Session
+
+from .models import AdminAuthAttempt
+from .submission_security import RateLimitConfig, client_address
+
+
+class AdminAuthConfig(RateLimitConfig):
+    admin_token: str
+    admin_auth_attempt_limit: int
+    admin_auth_window_seconds: int
+
+
+def verify_admin(
+    request: Request,
+    db: Session,
+    authorization: str | None,
+    config: AdminAuthConfig,
+) -> str:
+    now = datetime.now(timezone.utc)
+    cutoff = now - timedelta(seconds=config.admin_auth_window_seconds)
+    client = client_address(request, config.trusted_proxy_cidrs)
+    client_hash = hmac.new(
+        config.rate_limit_secret.encode(), f"admin:{client}".encode(), hashlib.sha256
+    ).hexdigest()
+    if db.get_bind().dialect.name == "postgresql":
+        lock_key = int(client_hash[:16], 16) & 0x7FFF_FFFF_FFFF_FFFF
+        db.execute(text("SELECT pg_advisory_xact_lock(:lock_key)"), {"lock_key": lock_key})
+    db.execute(delete(AdminAuthAttempt).where(AdminAuthAttempt.created_at < now - timedelta(days=1)))
+    failures = db.scalar(
+        select(func.count()).select_from(AdminAuthAttempt).where(
+            AdminAuthAttempt.client_hash == client_hash,
+            AdminAuthAttempt.created_at >= cutoff,
+        )
+    ) or 0
+    if failures >= config.admin_auth_attempt_limit:
+        db.commit()
+        raise HTTPException(
+            status_code=429,
+            detail="too many admin authentication attempts",
+            headers={"Retry-After": str(config.admin_auth_window_seconds)},
+        )
+    expected = f"Bearer {config.admin_token}"
+    if not authorization or not hmac.compare_digest(authorization, expected):
+        db.add(AdminAuthAttempt(client_hash=client_hash, created_at=now))
+        db.commit()
+        raise HTTPException(
+            status_code=401,
+            detail="invalid admin token",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+    db.execute(delete(AdminAuthAttempt).where(AdminAuthAttempt.client_hash == client_hash))
+    db.commit()
+    return "admin"