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homelab-mfa/README.md
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amir 1fa7144a7b
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feat: login-context approval screen, one-tap Deny, stale-request expiry
- Approve now opens an in-app review screen showing app/user/IP/geo of the
  request (optional deep-link params: app, user, ip, geo, ts) before biometrics
- Add a Deny button on the approval screen (no biometric needed to reject)
- Reject requests older than 2 min via the ts param (replay safety net)
- README: context params table, new Features bullets, approve-context screenshot
- Bump to v1.2 (versionCode 3)
2026-06-21 02:44:27 +00:00

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# Homelab MFA
Biometric push-approval for your homelab logins. When you sign in through Authentik, your phone
buzzes — approve with a fingerprint, or deny with one tap. A self-hosted alternative to Duo /
Authy push, with **no third-party cloud** in the loop.
## How it works
1. You log in via **Authentik**. A flow step fires an **ntfy** notification to your phone with two
action buttons: **Approve** and **Deny**.
2. The buttons are `homemfa://approve?token=…` / `homemfa://deny?token=…` deep links that open this app.
3. **Approve** opens an in-app review screen showing *who is asking* (see context params below), then
triggers a biometric prompt (fingerprint / face / device PIN). On success the app POSTs
`approve:<token>` to `ntfy.khodak.me/mfa-approve`; your Authentik flow is listening on that topic and
completes the login. You can also **Deny** right from that screen.
4. **Deny** POSTs `deny:<token>` to `mfa-deny` and blocks the login — no biometric needed to reject.
### Optional context params
The approve link may carry extra query params so you can see what you're approving before you do:
| Param | Shown as | Example |
|--------|---------------------|------------------------|
| `app` | 🖥 application name | `app=Grafana` |
| `user` | 👤 username | `user=amir` |
| `ip` | 📍 source IP | `ip=203.0.113.44` |
| `geo` | appended to the IP | `geo=Berlin, DE` |
| `ts` | request timestamp (epoch ms) — used to **expire** stale prompts after 2 min | `ts=1750000000000` |
All are optional and URL-encoded; with none present the app just shows a plain Approve / Deny prompt.
The activity is `showWhenLocked` + `turnScreenOn`, so an approval works straight from the lock screen.
## Features
- **Biometric gate** — `BIOMETRIC_STRONG` or device credential required to approve (deny is instant)
- **Login context** — see the app, user, source IP and geo of the request before approving
- **One-tap Deny** — reject a suspicious login straight from the approval screen, no biometric needed
- **Stale-request expiry** — prompts older than 2 minutes can't be approved (replay safety net)
- **Lock-screen ready** — wakes the screen and shows over the keyguard
- **Self-hosted** — talks only to your own ntfy instance; no Firebase, no vendor cloud
- **Zero stored secrets** — stateless; each request carries a one-time token
- **Setup self-check** — a "Test Biometric" button confirms enrollment before you rely on it
## Screenshots
<p align="center">
<img src="docs/screenshots/setup.png" width="240" alt="Setup / ready screen">
&nbsp;
<img src="docs/screenshots/approve-context.png" width="240" alt="Approval prompt with login context">
&nbsp;
<img src="docs/screenshots/approved.png" width="240" alt="Login approved">
</p>
## Install
1. Download `homelab-mfa.apk` from the [latest release](../../releases/latest)
2. On your Android phone: **Settings → Apps → Install unknown apps** → allow your browser/file manager
3. Open the APK and tap Install
4. Open **Homelab MFA** and tap **Test Biometric** to confirm your fingerprint is enrolled
## Server side
You need:
- An **ntfy** instance reachable at `ntfy.khodak.me` (or change the host in `MainActivity.kt`)
- An **Authentik** flow that, on login, publishes a notification with the two `homemfa://` action
buttons, then waits on the `mfa-approve` / `mfa-deny` topics for the decision
## Requirements
- Android 9.0+ (API 28)
- A fingerprint, face, or device PIN enrolled