Merge gap-b-per-ip-limit: per-IP WS rate limiting via CF-Connecting-IP

backend/app/rate_limit.py

@@ -1,5 +1,24 @@
 import time
 from collections import defaultdict
+from typing import Mapping
+
+
+def resolve_client_ip(headers: Mapping[str, str], direct_host: str | None) -> str:
+    """Resolves the real visitor IP for per-IP rate limiting.
+
+    The App CT sits behind a Cloudflare Tunnel that runs on a separate
+    machine (see README Architecture) — every internet-facing connection's
+    raw TCP peer is that tunnel machine, not the visitor, which would
+    collapse per-IP limiting to a single shared bucket for all remote
+    traffic. Cloudflare's edge sets `CF-Connecting-IP` itself, stripping any
+    client-supplied value first, so it's safe to trust here. Direct
+    LAN/local access (no Cloudflare in front, e.g. local dev) has no such
+    header and falls back to the raw socket peer.
+    """
+    forwarded = headers.get("cf-connecting-ip")
+    if forwarded:
+        return forwarded
+    return direct_host or "unknown"
 
 
 class RateLimiter:

backend/app/ws.py

@@ -36,7 +36,7 @@ from app.models.contact_session import ContactSession
 from app.models.entity import Entity
 from app.models.entity_sighting import EntitySighting
 from app.models.event import Event
-from app.rate_limit import RateLimiter
+from app.rate_limit import RateLimiter, resolve_client_ip
 from app.telemetry import detect_wire_spike, sample_network
 from app.tts.piper import synthesize_spirit_voice
 from app.tts.voices import pick_voice
@@ -53,6 +53,16 @@ fragment_limiter = RateLimiter(max_requests=30, window_seconds=60)
 question_limiter = RateLimiter(max_requests=6, window_seconds=60)
 summon_limiter = RateLimiter(max_requests=4, window_seconds=60)
 
+# Per-IP limiters for the same trigger points (spec §5). Ollama is a shared,
+# single-instance, CPU-only resource — per-account limits alone don't stop
+# one compromised/scripted account from hammering it across many source IPs,
+# nor do they protect the resource from many accounts sharing one IP. IP
+# thresholds are looser than the per-account ones since a single IP can
+# legitimately host multiple accounts on a shared network.
+fragment_ip_limiter = RateLimiter(max_requests=60, window_seconds=60)
+question_ip_limiter = RateLimiter(max_requests=12, window_seconds=60)
+summon_ip_limiter = RateLimiter(max_requests=8, window_seconds=60)
+
 AUDIO_DIR = Path(settings.data_dir) / "audio"
 
 
@@ -65,6 +75,7 @@ def _audio_dir() -> Path:
 class SeanceState:
     user_id: uuid.UUID
     session_id: uuid.UUID
+    client_ip: str
     send_queue: asyncio.Queue = field(default_factory=asyncio.Queue)
     mode: str = "unknown"
     language: str = "en"
@@ -91,6 +102,11 @@ def serialize_entity(entity: Entity) -> dict:
     }
 
 
+def _client_ip(websocket: WebSocket) -> str:
+    host = websocket.client.host if websocket.client else None
+    return resolve_client_ip(websocket.headers, host)
+
+
 async def _authenticate(websocket: WebSocket) -> uuid.UUID | None:
     raw_token = websocket.cookies.get(SESSION_COOKIE_NAME)
     if raw_token is None:
@@ -227,7 +243,12 @@ async def _summon(state: SeanceState, channel: str) -> tuple[Entity, bool]:
 
 
 async def _handle_summon(state: SeanceState) -> None:
-    if not summon_limiter.allow(str(state.user_id)):
+    # Short-circuits: an account already over its own cap never gets far
+    # enough to spend from the IP budget too.
+    if not (
+        summon_limiter.allow(str(state.user_id))
+        and summon_ip_limiter.allow(state.client_ip)
+    ):
         await state.send_queue.put(
             {
                 "type": "error",
@@ -266,7 +287,10 @@ async def _handle_anomaly(state: SeanceState, message: dict) -> None:
             await state.send_queue.put({"type": "status", "state": "attuning"})
         return
 
-    if not fragment_limiter.allow(str(state.user_id)):
+    if not (
+        fragment_limiter.allow(str(state.user_id))
+        and fragment_ip_limiter.allow(state.client_ip)
+    ):
         return  # anomalies during a crowded veil just pass unheard
 
     try:
@@ -279,7 +303,10 @@ async def _handle_anomaly(state: SeanceState, message: dict) -> None:
 
 
 async def _handle_question(state: SeanceState, text: str) -> None:
-    if not question_limiter.allow(str(state.user_id)):
+    if not (
+        question_limiter.allow(str(state.user_id))
+        and question_ip_limiter.allow(state.client_ip)
+    ):
         await state.send_queue.put(
             {
                 "type": "error",
@@ -390,7 +417,11 @@ async def session_socket(websocket: WebSocket) -> None:
         await db.commit()
         await db.refresh(contact_session)
 
-    state = SeanceState(user_id=user_id, session_id=contact_session.id)
+    state = SeanceState(
+        user_id=user_id,
+        session_id=contact_session.id,
+        client_ip=_client_ip(websocket),
+    )
     sender = asyncio.create_task(_sender(state, websocket))
     await state.send_queue.put({"type": "session", "id": str(contact_session.id)})