Security

flexiq is a library you embed in your own services, so most of its security posture is a function of how you deploy it. This page describes the trust model and the controls available to harden a deployment.

Trust model

The single most important assumption to understand:

Mitigations, in order of strength:

1. Lock down the store. Network-isolate Postgres/Redis, use least-privilege credentials, and never expose the SQLite file to untrusted writers.
2. Authenticate payloads with SignedSerializer (below) so a forged payload is rejected before it is ever deserialized.
3. Avoid cloudpickle entirely by using JsonSerializer or MsgPackSerializer when your task arguments are plain data.

Payload authentication

SignedSerializer prepends an HMAC-SHA256 tag to every payload and verifies it (constant-time) before deserializing. A worker refuses any bytes not produced with the shared key.

import os
from flexiq import Queue
from flexiq.serializers import SignedSerializer, SmartSerializer

key = os.urandom(32)  # 32+ bytes, identical on producers and workers
queue = Queue(serializer=SignedSerializer(SmartSerializer(), key))

For confidentiality as well, wrap EncryptedSerializer (AES-GCM, so it authenticates the payload too — no need to also wrap SignedSerializer):

from flexiq.serializers import EncryptedSerializer, SmartSerializer

enc_key = os.urandom(32)  # 16, 24, or 32 bytes for AES-128/192/256
queue = Queue(serializer=EncryptedSerializer(SmartSerializer(), enc_key))

See Pluggable Serializers for the full matrix.

Payloads at rest

By default, payloads are stored unencrypted (msgpack/cloudpickle bytes). Anyone with read access to the database can recover task arguments. Use EncryptedSerializer when tasks carry secrets or PII.

Payload size limit

Every serialized payload is capped at max_payload_bytes (default 1 MiB) and rejected at enqueue time, so a single producer can't exhaust storage or spike worker memory. Adjust or disable it per queue:

queue.max_payload_bytes = 4 * 1024 * 1024  # 4 MiB
queue.max_payload_bytes = 0                 # disable the cap

Dashboard

The dashboard serves openly by default — authentication is opt-in via serve_dashboard(auth_enabled=True) or flexiq dashboard --auth. Production deployments should enable it (or keep the dashboard on a private network behind their own auth). With auth enabled, the dashboard enforces sessions once at least one user exists; until then every API route returns 503 setup_required. Bootstrap the first admin with FLEXIQ_DASHBOARD_ADMIN_USER / FLEXIQ_DASHBOARD_ADMIN_PASSWORD (the password is removed from the environment after first use).

• Roles. Mutating routes (cancel/replay jobs, purge dead-letters, pause queues, manage webhooks/settings/overrides) require the admin role. viewer sessions keep read access and their own logout/change-password.
• Cookies. Session and CSRF cookies carry HttpOnly (session), SameSite=Strict, and Secure. Behind a TLS-terminating proxy that speaks plain HTTP to the backend you may need serve_dashboard(secure_cookies=False) or flexiq dashboard --insecure-cookies — only on a trusted network.
• Metrics. With auth enabled, /metrics and /readiness require a valid session or the FLEXIQ_DASHBOARD_METRICS_TOKEN bearer (give scrapers the token). Without auth they stay public unless that token is set; /health is always open for liveness probes.
• Settings. The settings API never exposes or accepts keys under the internal auth: namespace (password hashes, sessions, CSRF secret).
• Security headers. Every dashboard response carries a Content-Security-Policy locked to the dashboard's own origin, X-Content-Type-Options: nosniff, X-Frame-Options: DENY, and Referrer-Policy: same-origin. Configured external links and integration URLs are also scheme-filtered client-side — only http(s) and same-origin paths ever become clickable.

Webhooks

Outbound webhook URLs are validated against private/loopback/link-local and cloud-metadata addresses at delivery time (not just registration), which closes the DNS-rebinding SSRF (server-side request forgery) window, and redirects are not followed. For local development against http://localhost, set FLEXIQ_WEBHOOKS_ALLOW_PRIVATE=1.

Webhook payloads are signed with HMAC-SHA256 in the X-Flexiq-Signature header (sha256=<hex>). Receivers must verify it with a constant-time comparison (hmac.compare_digest), never ==.

Proxies and interception

These features reconstruct objects from the (untrusted) payload, so they have their own guards:

• Recipe signing. Set recipe_signing_key= (or FLEXIQ_RECIPE_SECRET) whenever proxy handlers are registered. Without a key, recipes are reconstructed unverified and a one-time warning is logged.
• File proxy allowlist. file_path_allowlist is enforced by path-component containment (no /var/data → /var/data_exfil bypass) against the resolved path.
• Type reconstruction. Interception only reconstructs known-safe kinds (enums, dataclasses, pydantic models, named tuples); arbitrary import-and-call targets like os.system are rejected.

Distributed locks

DistributedLock.info() masks the owner_id of locks held by other owners, so a peer can't read another holder's token and forge a release. Redis locks set a native key TTL, so a crashed holder's lock is reclaimed even if the maintenance reaper is down.

Scaler bind address

flexiq scaler and serve_scaler() bind to 127.0.0.1 by default. The scaler endpoints are unauthenticated — only bind to 0.0.0.0 behind a trusted network boundary (e.g. a KEDA sidecar on a private network).

Production hardening checklist

• Network-isolate Postgres/Redis; least-privilege credentials.
• Use SignedSerializer (and/or EncryptedSerializer) for the queue.
• Set recipe_signing_key if any proxy handler is registered.
• Enable dashboard auth (--auth / auth_enabled=True) and create an admin; serve the dashboard over TLS.
• Set FLEXIQ_DASHBOARD_METRICS_TOKEN if metrics are network-reachable.
• Auth-gate any mounted FastAPI/Flask contrib routers.
• Leave max_payload_bytes enabled (default 1 MiB) unless you need larger.
• Keep the scaler bound to loopback (or behind a network policy).
• Do not set FLEXIQ_WEBHOOKS_ALLOW_PRIVATE in production.