Postmarks

Description

Run Postmarks, a single-user ActivityPub bookmarking website for the Fediverse, via Docker Compose. The owner curates a public collection of bookmarks that federates to followers on Mastodon and other ActivityPub servers. Upstream project: ckolderup/postmarks.

Overview

This role builds Postmarks from source into a custom image, wires it to the standard reverse proxy, and persists its SQLite data. Postmarks is single-user: there are no accounts, only "the owner". The upstream login is a single shared-secret password form that flips one session boolean (req.session.loggedIn).

Cosmos

The diagram places Postmarks in the Infinito.Nexus cosmos: the components it deploys (capabilities), the central services it consumes (dependencies), and its outward reach (federation and bridged external networks).

flowchart LR
    subgraph deps [Dependencies]
        dep_svc_net_tor["svc-net-tor 🐳🐝"]
        dep_web_app_dashboard["web-app-dashboard 🐳🐝"]
        dep_web_app_keycloak["web-app-keycloak 🐳🐝"]
        dep_web_app_matomo["web-app-matomo 🐳🐝"]
        dep_web_app_prometheus["web-app-prometheus 🐳🐝"]
        dep_web_app_stalwart["web-app-stalwart 🐳🐝"]
        dep_web_svc_css["web-svc-css 💻"]
        dep_web_svc_logout["web-svc-logout 🐳🐝"]
    end
    subgraph role [web-app-postmarks 🐳🐝]
        svc_sso["sso"]
        svc_logout["logout"]
        svc_dashboard["dashboard"]
        svc_matomo["matomo"]
        svc_css["css"]
        svc_email["email ❌"]
        svc_prometheus["prometheus"]
        svc_postmarks["postmarks"]
        svc_tor["tor"]
    end
    dep_svc_net_tor -. "0..1" .-> svc_tor
    dep_web_app_dashboard -. "0..1" .-> svc_dashboard
    dep_web_app_keycloak -. "0..1" .-> svc_sso
    dep_web_app_matomo -. "0..1" .-> svc_matomo
    dep_web_app_prometheus -. "0..1" .-> svc_prometheus
    dep_web_app_stalwart -- "0..0" --> svc_email
    dep_web_svc_css -. "0..1" .-> svc_css
    dep_web_svc_logout -. "0..1" .-> svc_logout
    linkStyle 5 stroke:red;

Solid 1:1 edges are fixed relationships; dashed 0..1 edges are conditional (enabled only in matching deployments); red 0..0 edges are turned off in this role. Node markers show the role's deploy modes (💻 host, 🐳 compose, 🐝 swarm); ❌ marks a service that is explicitly turned off, and ⚙️ an Ansible role dependency declared in meta/main.yml.

Features

Containerized build: Clones the pinned upstream ref and runs node server.js behind the front proxy.
Single-owner model: One privileged identity, gated by req.session.loggedIn.
Trusted-header SSO bridge: Establishes the owner session from the oauth2-proxy identity (see below).
Minimal footprint: Small Node.js/Express service that fits neatly into larger stacks.

Quick Setup

Development

Clone, set up the workstation, and deploy Postmarks onto the local stack:

git clone https://github.com/infinito-nexus/core.git
cd core
make onboard
make compose-deploy mode=reinstall apps=web-app-postmarks full_cycle=false

Production

Run the published image to provision the inventory and deploy Postmarks to a managed server (the mounted volume persists the inventory):

APP=web-app-postmarks
HOST=<your-server>
DOMAIN=<your-domain>
TLS_MODE=self_signed
SSH_PUBLIC_KEY="<your-ssh-public-key>"

docker run --rm -it \
  -v "$PWD/inventories:/etc/infinito.nexus/inventories" \
  -e APP="$APP" -e HOST="$HOST" -e DOMAIN="$DOMAIN" -e TLS_MODE="$TLS_MODE" -e SSH_PUBLIC_KEY="$SSH_PUBLIC_KEY" \
  ghcr.io/infinito-nexus/core/debian bash -c '
    INVENTORY=/etc/infinito.nexus/inventories/production
    infinito administration inventory provision "$INVENTORY" \
      --inventory-file "$INVENTORY/devices.yml" \
      --host "$HOST" \
      --include "$APP" \
      --vars "{\"TLS_MODE\": \"$TLS_MODE\", \"DOMAIN_PRIMARY\": \"$DOMAIN\", \"users\": {\"administrator\": {\"authorized_keys\": [\"$SSH_PUBLIC_KEY\"]}}}" &&
    infinito administration deploy dedicated "$INVENTORY/devices.yml" \
      --password-file "$INVENTORY/.password" \
      --diff -vv'

Single sign-on

Postmarks has no native OIDC/SAML/LDAP/REMOTE_USER login — the only auth path is the ADMIN_KEY password form. Under the oauth2 SSO flavor this role adds a trusted-header SSO bridge:

A sidecar web-app-keycloak oauth2-proxy authenticates the visitor against Keycloak (OIDC, or LDAP federated through Keycloak) and nginx overwrites the X-Forwarded-* identity headers on every proxied request.
A small Express middleware (files/sso/header_auth.js, mounted into server.js at build time by files/sso/patch_server.js) reads only those nginx-overwritten X-Forwarded-* headers and flips req.session.loggedIn = true, so the existing isAuthenticated gate on /admin opens for the proxied owner.
The bridge activates only when PROXY_HEADER_SSO is truthy (derived from lookup('sso', application_id, 'is_proxy_gated')); otherwise the middleware is a transparent pass-through and the native password form still guards /admin.
An optional PROXY_HEADER_SSO_ADMIN_GROUP check against X-Forwarded-Groups restricts the owner session to members of the application's administrator RBAC group.

Security: the identity headers are trusted unconditionally, which is only safe because the app port is bound to 127.0.0.1 and every request traverses the oauth2-proxy that overwrites X-Forwarded-*. The X-Auth-Request-* / Remote-User variants are deliberately ignored so an already-authenticated client cannot inject a different identity. Logout must go through web-svc-logout / the oauth2-proxy sign-out, not Postmarks' own logout link, because the proxy header re-establishes the session on the next request.

RBAC is not feasible beyond the group gate: Postmarks has no in-app authorisation tier beyond "owner or not" and no per-user identity, so X-Forwarded-Email/X-Forwarded-Preferred-Username cannot scope anything inside the app. This RBAC exception is documented per lifecycle.md.

Further Resources

Persona contract opt-outs

The persona flags are declared in templates/playwright.env.j2. administrator is blocked only in the sso: false variants: as described above, Postmarks' sole native credential is the single shared ADMIN_KEY password form, which is not the Keycloak administrator secret the persona types, so without the trusted-header bridge there is no admin login to drive. biber is blocked in every variant — the oauth2-proxy admits only the application's administrator RBAC group and the bridge re-checks X-Forwarded-Groups, so biber is denied before Postmarks is reached, and with SSO off the only credential left belongs to no user account.

Credits

Implemented by Kevin Veen-Birkenbach. Part of the Infinito.Nexus Project and maintained by Kevin Veen-Birkenbach. Licensed under the Infinito.Nexus Community License (Non-Commercial).