Security Audit — Movie Night

Date: 2026-03-15 Auditor: Claude (AI-assisted review) Scope: Full codebase review (24 source files) Context: Currently exposed only on Tailscale tailnet. Planning to expose via Pangolin to the internet — these findings should be resolved before that transition.

Critical / High

1. Shared search links bypass authentication entirely

Location: app/routers/mood.py:187-207
Issue: GET /api/history/shared/{entry_id} is fully public. Sequential integer IDs make enumeration trivial. Anyone can view mood text, movie recommendations, and viewing patterns.
Fix: Add a cryptographic share token (e.g. secrets.token_urlsafe(16)) stored alongside the history entry. Require the token as a query parameter to access the shared endpoint.

2. Prompt injection via mood text

Location: app/services/llm/base.py:31-48
Issue: User-supplied mood is interpolated directly into the LLM prompt with no sanitization or length limit. A crafted input could manipulate rankings or attempt to extract the system prompt.
Mitigating factor: The title/ID cross-validation in app/routers/mood.py:87-94 is good defense-in-depth and limits the blast radius.
Fix: (a) Add a max length on mood input (~500 chars). (b) Strip or escape prompt-like patterns. (c) Add an explicit instruction in the system prompt to ignore meta-instructions in user text.

Medium

3. Container runs as root

Location: Dockerfile
Issue: No USER directive. The app runs as root inside the container.
Fix: Add RUN useradd -m -u 1000 appuser and USER appuser.

4. Insecure default session secret

Location: app/config.py
Issue: session_secret defaults to "change-me-in-production". If .env is misconfigured, sessions are trivially forgeable.
Fix: Remove the default and make it a required field (pydantic will error on startup if missing).

Location: app/routers/auth.py
Issue: /api/auth/login has no rate limiting, enabling brute-force attacks against Jellyfin credentials.
Fix: Add a simple in-memory rate limiter (e.g. slowapi or a manual counter per IP with a 5-attempt/minute window).

6. No security headers

Issue: No Content-Security-Policy, X-Frame-Options, X-Content-Type-Options, or Strict-Transport-Security headers are set by the application or documented for the reverse proxy.
Fix: Add a FastAPI middleware or document the required headers for the nginx/reverse proxy config.

7. Poster proxy has no input validation or auth

Location: app/main.py:43-52
Issue: item_id is passed directly to Jellyfin with no format validation and no authentication required. This leaks library contents and is a mild SSRF vector.
Fix: Validate item_id matches ^[a-f0-9]+$ (Jellyfin ID format) and require authentication.

8. Arbitrary `additional_user_ids` accepted

Location: app/routers/mood.py:31
Issue: The client can pass any user IDs to filter watch state. No server-side validation that the IDs belong to the household.
Fix: Maintain an allowlist of valid Jellyfin user IDs (or fetch them server-side) instead of trusting client input.

9. Database directory permissions not set

Location: app/database.py:8-9
Issue: os.makedirs uses default umask. Other container processes could read/write the DB.
Fix: os.makedirs(..., mode=0o700, exist_ok=True)

10. Sync endpoint has no rate limit

Location: app/routers/library.py:58-62
Issue: Any authenticated user can spam POST /api/library/sync, spawning unbounded background tasks.
Fix: Track last sync time and reject requests within a cooldown window (e.g. 10 minutes).

Low (easy wins)

#	Finding	Location	Fix
11	No mood text length limit	`app/routers/mood.py:25`	Add `max_length=500` to Pydantic model
12	No auth event logging	`app/routers/auth.py`	Log failed/successful logins with IP + timestamp
13	No search history retention policy	`app/routers/mood.py`	Add periodic cleanup (e.g. 90-day TTL)
14	Tailwind loaded from CDN	`app/static/index.html:7`	Consider Subresource Integrity (`integrity=` attribute)
15	No `.dockerignore` for `.env`	`.dockerignore`	Ensure `.env` is listed

What's done well

Parameterized SQL everywhere — no injection vectors found
Secure session cookies — HttpOnly, SameSite=Lax, Secure flag, 32-byte random IDs
LLM output validation — title/ID cross-check prevents hallucinated recommendations
Dependencies are current — no known CVEs in pinned versions
No secrets in source — .env is gitignored, .env.example is clean

Resolution priority

Must fix before internet exposure (via Pangolin):

Shared search link auth (#1)
Container runs as root (#3)
Session secret default (#4)
Rate limiting on login (#5)
Security headers (#6)
Poster proxy validation (#7)
Mood text length limit (#11)

Should fix soon after:

Prompt injection hardening (#2)
User ID validation (#8)
DB permissions (#9)
Sync rate limit (#10)
Auth logging (#12)

Nice to have:

History retention (#13)
Tailwind SRI (#14)
Dockerignore check (#15)

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