feat(ai): durcissement phase F (#79) - rate limit, redaction, OpenAPI/MCP, E2E

backend/tools/ratelimit.py

@@ -0,0 +1,153 @@
+"""Rate limiting for the AI tool layer (Phase F).
+
+Complements the IP-based login limiter (``backend.ratelimit``) with a
+per-identity, per-tool sliding-window limiter applied to every tool call,
+whether it originates from the in-app assistant or the MCP server.
+
+Two counters are maintained per identity:
+
+* a **global** counter (all tools combined), capped by
+  ``OBSIGATE_TOOL_RATE_LIMIT``;
+* a **per-tool** counter, capped by ``OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL``
+  (defaults to the global cap) so a single expensive tool cannot consume the
+  whole budget.
+
+The window length is ``OBSIGATE_TOOL_RATE_WINDOW`` seconds (default 60).
+
+The identity is the token JTI when available (``_token_jti`` attached by the
+auth middleware), otherwise the user id/username. This gives "per token / per
+tool" limiting while remaining meaningful for anonymous/disabled-auth mode.
+"""
+
+from __future__ import annotations
+
+import logging
+import os
+import time
+from collections import deque
+from typing import Any
+
+logger = logging.getLogger("obsigate.tools.ratelimit")
+
+# --- Configuration (read at call time so tests can monkeypatch env) ---
+DEFAULT_RATE_LIMIT = 60
+DEFAULT_RATE_WINDOW = 60
+
+
+def _env_int(name: str, default: int) -> int:
+    try:
+        return int(os.environ.get(name, str(default)))
+    except (TypeError, ValueError):
+        return default
+
+
+def _global_limit() -> int:
+    return _env_int("OBSIGATE_TOOL_RATE_LIMIT", DEFAULT_RATE_LIMIT)
+
+
+def _per_tool_limit() -> int:
+    return _env_int("OBSIGATE_TOOL_RATE_LIMIT_PER_TOOL", _global_limit())
+
+
+def _window() -> int:
+    return max(1, _env_int("OBSIGATE_TOOL_RATE_WINDOW", DEFAULT_RATE_WINDOW))
+
+
+# --- In-memory store: {counter_key: deque[timestamp]} ---
+_calls: dict[str, deque] = {}
+
+
+def _identity_key(identity: str | None) -> str:
+    return identity or "anonymous"
+
+
+def _counter_key(identity: str | None, tool: str | None) -> str:
+    base = _identity_key(identity)
+    return f"{base}\x00{tool}" if tool else base
+
+
+def _prune(entries: deque, now: float, window: int) -> None:
+    cutoff = now - window
+    while entries and entries[0] <= cutoff:
+        entries.popleft()
+
+
+def check_and_record(identity: str | None, tool: str, *, now: float | None = None) -> tuple[bool, int]:
+    """Record one call and report whether it is allowed.
+
+    Args:
+        identity: Rate-limit identity (token JTI or username).
+        tool: Tool name (used for the per-tool counter).
+        now: Optional timestamp override (tests).
+
+    Returns:
+        ``(allowed, retry_after)``. When ``allowed`` is False, ``retry_after``
+        is the number of seconds until the oldest call leaves the window.
+    """
+    now = time.time() if now is None else now
+    window = _window()
+    global_limit = _global_limit()
+    tool_limit = _per_tool_limit()
+
+    global_entries = _calls.setdefault(_counter_key(identity, None), deque())
+    tool_entries = _calls.setdefault(_counter_key(identity, tool), deque())
+    _prune(global_entries, now, window)
+    _prune(tool_entries, now, window)
+
+    if len(global_entries) >= global_limit or len(tool_entries) >= tool_limit:
+        oldest = min(
+            global_entries[0] if len(global_entries) >= global_limit else now,
+            tool_entries[0] if len(tool_entries) >= tool_limit else now,
+        )
+        retry_after = max(1, int(oldest + window - now) + 1)
+        logger.warning(f"Tool rate limit exceeded for '{_identity_key(identity)}' on '{tool}'")
+        return False, retry_after
+
+    global_entries.append(now)
+    tool_entries.append(now)
+    return True, 0
+
+
+def remaining(identity: str | None, tool: str | None = None) -> int:
+    """Return the number of calls still allowed in the current window."""
+    now = time.time()
+    window = _window()
+    if tool:
+        entries = _calls.get(_counter_key(identity, tool))
+        if entries is None:
+            return _per_tool_limit()
+        _prune(entries, now, window)
+        return max(0, _per_tool_limit() - len(entries))
+    entries = _calls.get(_counter_key(identity, None))
+    if entries is None:
+        return _global_limit()
+    _prune(entries, now, window)
+    return max(0, _global_limit() - len(entries))
+
+
+def reset(identity: str | None = None) -> None:
+    """Clear rate-limit state (all identities, or a single one)."""
+    if identity is None:
+        _calls.clear()
+        return
+    prefix = f"{_identity_key(identity)}\x00"
+    for key in [k for k in _calls if k == _identity_key(identity) or k.startswith(prefix)]:
+        del _calls[key]
+
+
+def get_status(identity: str | None = None) -> dict[str, Any]:
+    """Diagnostic snapshot of the limiter (for tests / admin tooling)."""
+    if identity is None:
+        return {
+            "tracked_identities": len({k.split("\x00", 1)[0] for k in _calls}),
+            "global_limit": _global_limit(),
+            "per_tool_limit": _per_tool_limit(),
+            "window_seconds": _window(),
+        }
+    return {
+        "identity": _identity_key(identity),
+        "remaining_global": remaining(identity),
+        "global_limit": _global_limit(),
+        "per_tool_limit": _per_tool_limit(),
+        "window_seconds": _window(),
+    }