# 001 — CSRF verification fails behind a TLS-terminating reverse proxy

**Status:** Fixed

## Description

Deploying Daybook behind Apache (TLS-terminating reverse proxy → plain HTTP
to the container) on `cloud-vm-1`, login failed with:

```
Forbidden (403)
CSRF verification failed. Request aborted.
```

**Root cause:** `daybook_project/settings.py` set `ALLOWED_HOSTS` from an env
var but never set `CSRF_TRUSTED_ORIGINS` or `SECURE_PROXY_SSL_HEADER`. Without
the latter, Django has no way to know the original request was HTTPS — the
proxy terminates TLS and forwards plain HTTP — so it treats every request as
insecure, which breaks CSRF checks on any POST (including login) once a
browser connects over `https://`.

This isn't specific to `cloud-vm-1` — it'll happen on any reverse-proxied
deployment (Apache, Nginx, Traefik, a cloud load balancer), which is the
explicitly recommended setup in `deploy/cloud_agent_deploy.md` §8. The
runbook doesn't mention CSRF or proxy-awareness anywhere.

## Fix

**App (`daybook_project/settings.py`):**

```python
CSRF_TRUSTED_ORIGINS = [origin.strip() for origin in os.environ.get("DJANGO_CSRF_TRUSTED_ORIGINS", "").split(",") if origin.strip()]
SECURE_PROXY_SSL_HEADER = ("HTTP_X_FORWARDED_PROTO", "https")
```

Committed locally as `d458cd3` ("Fix CSRF failure behind a TLS-terminating
reverse proxy") — **needs to be pushed to `main`**, the deploy agent that
made this fix didn't have push access to the Forgejo repo.

**Deploy env (`deploy/env.example` / runbook):** needs a new var,
`DJANGO_CSRF_TRUSTED_ORIGINS`, set to the public HTTPS origin, e.g.:

```
DJANGO_CSRF_TRUSTED_ORIGINS=https://daybook.example.com
```

**Proxy config:** `SECURE_PROXY_SSL_HEADER` only works if the proxy actually
sends that header. The Apache example in `cloud_agent_deploy.md` §8 is
missing it — needs:

```apache
RequestHeader set X-Forwarded-Proto "https"
```

inside the `<VirtualHost *:443>` block (requires `a2enmod headers`). The
equivalent for Nginx is `proxy_set_header X-Forwarded-Proto $scheme;`, worth
adding to `docs/deployment.md`'s reverse-proxy notes too since that doc
mentions Nginx/Traefik as options without this caveat.

## Resolution

- [x] Pushed commit `d458cd3` to `main`.
- [x] Added `DJANGO_CSRF_TRUSTED_ORIGINS` to `deploy/env.example` with an
      explanatory comment.
- [x] Updated `cloud_agent_deploy.md` §8's Apache example to include
      `RequestHeader set X-Forwarded-Proto "https"`, plus a Caddy equivalent
      and a checklist item that verifies by actually logging in through the
      proxy (not just curling `/api/capabilities`, which is unauthenticated
      GET and wouldn't have caught this).
- [x] Updated `docs/deployment.md`'s "Reverse Proxy Notes" and checklist with
      the same requirement, plus an Nginx/Apache/Caddy header cheat sheet.