fix: harden SAC security per audit (0.4.15)

Close audit findings: anti-spoof client IP for login rate limit, JWT/CORS
enforce on startup, SSH host-key verification and sudo via stdin, optional
WinRM HTTPS, SSE httpOnly cookie auth, ingest body limit, ILIKE escaping,
and HMAC API key hashing with legacy SHA-256 fallback.

backend/app/auth/api_key.py

@@ -1,4 +1,5 @@
-import hashlib
+import hashlib
+import hmac
 import secrets
 
 from fastapi import Depends, HTTPException, Security
@@ -6,16 +7,28 @@ from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
 from sqlalchemy import select
 from sqlalchemy.orm import Session
 
+from app.config import get_settings
 from app.database import get_db
 from app.models import ApiKey
 
 security_scheme = HTTPBearer(auto_error=False)
 
 
-def hash_api_key(raw_key: str) -> str:
+def _legacy_hash_api_key(raw_key: str) -> str:
     return hashlib.sha256(raw_key.encode("utf-8")).hexdigest()
 
 
+def hash_api_key(raw_key: str) -> str:
+    secret = get_settings().jwt_secret.encode("utf-8")
+    return hmac.new(secret, raw_key.encode("utf-8"), hashlib.sha256).hexdigest()
+
+
+def verify_api_key_hash(raw_key: str, stored_hash: str) -> bool:
+    if hmac.compare_digest(hash_api_key(raw_key), stored_hash):
+        return True
+    return hmac.compare_digest(_legacy_hash_api_key(raw_key), stored_hash)
+
+
 def generate_api_key() -> tuple[str, str, str]:
     """Returns (full_key, prefix, hash)."""
     raw = f"sac_{secrets.token_urlsafe(32)}"
@@ -24,9 +37,11 @@ def generate_api_key() -> tuple[str, str, str]:
 
 
 def verify_api_key(db: Session, raw_key: str) -> bool:
-    key_hash = hash_api_key(raw_key)
-    row = db.scalar(select(ApiKey).where(ApiKey.key_hash == key_hash, ApiKey.is_active.is_(True)))
-    return row is not None
+    rows = db.scalars(select(ApiKey).where(ApiKey.is_active.is_(True))).all()
+    for row in rows:
+        if verify_api_key_hash(raw_key, row.key_hash):
+            return True
+    return False
 
 
 def get_api_key_auth(

backend/app/auth/stream_cookie.py

@@ -0,0 +1,37 @@
+"""httpOnly cookie auth for SSE (EventSource cannot send Authorization header)."""
+
+from __future__ import annotations
+
+from fastapi import Response
+
+from app.config import Settings
+
+STREAM_COOKIE_NAME = "sac_stream"
+STREAM_COOKIE_PATH = "/api/v1/stream"
+
+
+def stream_cookie_kwargs(settings: Settings) -> dict[str, object]:
+    secure = settings.sac_public_url.lower().startswith("https://")
+    return {
+        "key": STREAM_COOKIE_NAME,
+        "httponly": True,
+        "secure": secure,
+        "samesite": "strict",
+        "path": STREAM_COOKIE_PATH,
+        "max_age": max(60, int(settings.jwt_expire_minutes) * 60),
+    }
+
+
+def set_stream_auth_cookie(response: Response, token: str, settings: Settings) -> None:
+    response.set_cookie(value=token, **stream_cookie_kwargs(settings))
+
+
+def clear_stream_auth_cookie(response: Response, settings: Settings) -> None:
+    kwargs = stream_cookie_kwargs(settings)
+    response.delete_cookie(
+        key=kwargs["key"],
+        path=kwargs["path"],
+        secure=bool(kwargs["secure"]),
+        httponly=True,
+        samesite="strict",
+    )