Plan: Security Hardening & Documentation — COMPLETE

Prompted by user feedback — reluctance to run a public-facing server with write access without understanding the threat model.

Problem

There's no security documentation. Security-conscious users have to guess at the attack surface and hardening options. This blocks public adoption.

What Was Done

1. Security page on the website — DONE

• docs/site/security/index.md + pages branch security.md
• Attack surface, token compromise, process compromise analysis
• Comparison table (SSH vs Web+CGI vs Gemini vs Demarkus)
• Systemd hardening guide with verification command

2. Systemd hardening in install script + deployment docs — DONE

• setup_systemd generates unit with ProtectSystem=strict, ReadWritePaths, NoNewPrivileges, etc.
• Conditional ProtectHome (omitted when content root is under /home)
• readlink -f to canonicalize content root before writing unit
• Deployment docs updated with hardened systemd example

3. Install script detects insecure existing config on update — DONE

• _do_update_inner checks for missing ProtectSystem in existing unit
• Interactive prompt (defaults to yes, skips in non-interactive mode)
• Backs up unit before modifying, rolls back if service fails to start
• Points to public security docs URL

4. Read-only mode (-read-only flag) — DONE

• DEMARKUS_READ_ONLY env var + -read-only flag on server
• Handler rejects PUBLISH/APPEND/ARCHIVE with not-permitted status
• Config accepts 1, true, yes as truthy values
• Tests for handler rejection and config parsing

5. demarkus-publish CLI tool — DONE

• server/cmd/demarkus-publish/main.go
• Writes directly to versioned store on disk (same store.Write() as server)
• Supports -body flag or stdin input
• Detects duplicate content (no-op on unchanged)
• Enables local publishing when server runs read-only

6. Read-only chroot install script — DONE

• install-readonly.sh — separate script for maximum security deployments
• Chroot structure: /srv/demarkus/{bin,content,tls}
• Systemd unit with RootDirectory, ReadOnlyPaths=/, BindReadOnlyPaths=/dev/urandom
• Installs demarkus-publish to /usr/local/bin for local publishing
• SHA-256 checksum verification on downloads
• Rejects dangerous root paths (/, /usr, /etc, etc.)
• No auto firewall changes (user decides)

7. Cleanup

• Removed redundant demarkus.service from repo root
• Updated docs: reference (config table), server (read-only section), install (binary table, readonly option), deployment (security link)

Key Design Decisions

• Shared store code: demarkus-publish calls store.Write() directly — same code path as the server. No duplication.
• not-permitted not unauthorized: Read-only rejection is a server policy, not an auth failure.
• Separate install script: Read-only chroot install is a different deployment model, kept separate to avoid complicating the main install script.
• No iptables: Replaced fragile iptables write isolation with read-only mode + chroot, which is simpler and more secure.