wiki-vault/Sources/Homelab/env-file-hardening.md

---
created: 2026-04-19
path: Sources/Homelab
project: env-file-hardening
status: active
tags:
- pbs
- security
- docker
- ansible
- secrets
type: project-plan
updated: 2026-04-19
---

# Env File Hardening

## Goal

Remove the easy path to PBS secrets. Right now `.env` files in
`/opt/docker` are readable by anyone with filesystem access — including
`pbsdeploy`. If the deploy key is compromised, an attacker can `cat .env`
and grab every API key and password instantly.

Goal: `pbsdeploy` can deploy containers without ever being able to read the
secrets they use.

## Threat Model

- **Primary risk:** `pbsdeploy` SSH key leaks → attacker SSHes in → reads
`.env` files → owns every service.
- **Mitigation goal:** eliminate the trivial read path. Raise the bar so an
attacker would need to escalate to root (no sudo on `pbsdeploy`), pivot
accounts, or break out of a container.
- **Accepted residual risk:** Determined attackers with deep access can
still cause damage. This is about removing low-hanging fruit, not achieving
zero risk.

## Two-Phase Approach

### Phase 1: Filesystem Permissions (80/20 win)

Lock `.env` files down to `root:root 0600`. The Docker daemon runs as root,
so `docker compose` still reads them fine when processing compose files.
`pbsdeploy` runs `docker compose up`, which talks to the daemon via socket
— `pbsdeploy` itself never reads `.env` directly.

**Net effect:** the trivial `cat .env` path is gone. No sidecar needed, no
app code changes, no runtime complexity.

### Phase 2: Encryption at Rest on the Server (defense in depth, deferred)

Currently secrets are encrypted in the `wp-i` repo via ansible-vault, but
land as plaintext on the server filesystem. Phase 2 keeps them encrypted on
disk and decrypts only at container start (via sidecar or similar).

**Protects against:** backup leaks, Linode snapshot exfil, accidental
exposure, offline decrypt of historical filesystem copies.

**Not urgent because:** secrets are already encrypted in the repo, Linode
account is behind 2FA, no compliance driver. This is "nice to have when
refactoring," per earlier conversation on the topic.

## Design Decisions

- **Phase 1 is just filesystem perms** — no sidecar, no Docker secrets, no
app changes. Docker daemon reads `.env` as root; `pbsdeploy` doesn't need
to.
- **Phase 2 uses sidecar pattern when we get there** — tiny init container
decrypts at runtime, injects env vars into main container, zero app code
changes. Compose secrets ruled out because it requires refactoring every
app to read from `/run/secrets/`.
- **External secret manager (Vault, etc.) ruled out** — overkill for
self-hosted prod scale. Revisit only if moving to Kubernetes.
- **Ansible stays the deploy tool** throughout — writes `.env` files as
root with tight perms. `pbsdeploy` has no sudoers entry, so it can't read
them back.
- **Staging first** for both phases.

## How the Permissions Work (Phase 1)

- Ansible SSHes in as `pbsdeploy` → uses `become: yes` to elevate for file
writes → files created as `root:root 0600`.
- `pbsdeploy` can't `cat` them (no read perms). Can't `sudo cat` them
either (no sudoers entry).
- Docker daemon runs as root → reads `.env` when processing compose files →
injects vars into containers.
- Main container sees env vars, doesn't know or care about file perms.

## Next Steps (Phase 1)

- [ ] Audit current state — which services have `.env` files in
`/opt/docker`, current ownership and perms
- [ ] Update Ansible role(s) to write `.env` as `root:root 0600` (not
`deployer` group)
- [ ] Pick a non-critical pilot service on staging
- [ ] Deploy change to pilot, verify container still works, verify
`pbsdeploy` can't read the file
- [ ] Roll out to all staging services
- [ ] Verify nothing breaks over a few deploys
- [ ] Roll out to production
- [ ] Remove `deployer` group read access to `.env` files (group can still
exist for other things if needed)

## Next Steps (Phase 2 — later)

- [ ] Decide on encryption approach: custom sidecar vs. SOPS + age vs.
something else
- [ ] Design sidecar container (Dockerfile, entrypoint, decryption strategy)
- [ ] Decide where the decryption key lives on the server and how it's
protected
- [ ] Pilot on one staging service
- [ ] Roll out across stack

## Open Questions

### Phase 1

- Does anything in `/opt/docker` currently rely on `deployer` group read
access to `.env` that we'd break by tightening perms?
- Are all services using `env_file:` in compose, or do some hardcode
secrets in the compose file itself (which would need separate handling)?

### Phase 2 (deferred)

- Sidecar implementation: custom shell-based init container vs.
off-the-shelf tool like SOPS?
- Where does the decryption key live on the server? (If it's in another
root-owned file, we're just moving the problem — though one layer deeper is
still an improvement.)

## Depends On / Related

- **SSH Login Alerting** — higher priority sibling project. Early warning
system for the threat this project mitigates.
- **PBSII CI/CD** — same `pbsdeploy` / `deployer` setup on staging; phase 1
changes apply there too.
- **Previous conversation on secrets managers** — concluded that for
single-server self-hosted prod, encryption-at-rest on the server is "nice
to have," not urgent. Phase 2 is the realization of that future work.


...sent from Jenny & Travis